short-lived access tokens
short-lived access tokens and long-lived refresh tokens
short-lived access tokens
short-lived access tokens and long-lived refresh tokens
https://clickamericana.com/topics/science-technology/vintage-portable-manual-typewriters

The Smith-Coronas were offered in 4 different colors.

The Remington Quiet-Riter was eventually offered in white sand, desert sage, mist green, and French gray,

The Royal HH was offered in 6 colors including green, pink, and blue. Brown was the most ubiquitous.
Why bother with dozens of big standards in your office when you can have a portable or two that you can move and which are always in demand?
100% The Practical Magazine of Efficient Management, November 1916, Volume 7, No. 45, p49. https://www.google.com/books/edition/Management/hqj2SD6khL4C?hl=en&gbpv=1&dq=corona&pg=RA4-PA49&printsec=frontcover
Origin of Royal's Vogue by [[x over it]]
Remington Quie- Riter Typewriter 1955
"students who use typewriters get up to 38% better grades."
"gives book reports and themes a professional look"
gendered sales technique - "girls particularly appreciate" the easy change ribbon system...
VINTAGE 1958 COMMERCIAL - REMINGTON RAND - OFFICE-RITER TYPEWRITER
Up to 10 carbons!<br /> Cuts clear, clean stencils 149.50 plus carrying case additional<br /> $1.50 a week payable monthly
Successful Secretary Presented by Royal Office Typewriters. A Thomas Craven Film Corporation Production, 1966. https://www.youtube.com/watch?v=If5b2FiDaLk.
Script: Lee Thuna<br /> Educational Consultant: Catharine Stevens<br /> Assistant Director: Willis F. Briley<br /> Design: Francisco Reynders<br /> Director & Producer: Carl A. Carbone<br /> A Thomas Craven Film Corporation Production
"Mother the mail"
gendered subservience
"coding boobytraps"
"I think you'll like the half sheet better. It is faster." —Mr. Typewriter, timestamp
A little bit of the tone of "HAL" from 2001: A Space Odyssey (1968). This is particularly suggestive as H.A.L. was a one letter increment from I.B.M. and the 1966 Royal 660 was designed to compete with IBM's Selectric
This calm voice makes suggestions to a secretary while H.A.L. does it for a male astronaut (a heroic figure of the time period). Suddenly the populace feels the computer might be a bad actor.
"We're living in an electric world, more speed and less effort."—Mr. Typewriter<br /> (techno-utopianism)
The twenty-first century, he wrote, far fromit becoming an oasis of democratic values, would more likely resemble thestruggles, wars, and conflicts of the nineteenth century.13
interesting, we jump back to ww1 versus 1800s, tragedy of great power politics vibes
Very interesting manuscript. The combination of yeast display data with AF3 structure prediction makes a compelling case for using in silico methods (AF3 and CamSol) to rapidly and conservatively identify promiscuous VHH binders across multiple targets. A couple of suggestions that might improve readability and deepen the interpretation:
Figure 2 and beyond: The clustering and FACS plots use three shades of blue to distinguish mono- and polyspecific VHHs, and the shades are close enough that they're hard to tell apart at a glance. Increasing the contrast in brightness (or switching to a more distinguishable palette) would make these figures easier to read.
Figure 3C: The 0.8 ipTM cutoff is used to separate binders from nonbinders, but it would help to see how ipTM tracks with the FACS fluorescence signal directly — e.g., a secondary axis or a simple correlation plot. That would let readers judge whether 0.8 is the right cutoff for this specific interaction, or just the field-standard benchmark being applied by convention.
Detection systems: I was surprised to see two such different detection systems used (AF-488 and PE) rather than, say, two AlexaFluor variants — different fluorophores and detection modes can have very different dynamic ranges, and AF-488 in particular has a smaller dynamic range than PE. It would help to know why these specific systems were chosen, since more comparable fluorophores might have made the results across conditions easier to compare directly.
I have not yet followed up with this trend on social media. Personally, I find the hashtag as a pound sign symbol.
and neither of them eversaid what they meantand i guess nobody ever does
Title: Family / Memory
Significance: This is the highpoint of the poem. It represents the thesis of what is the legacy. In this section the author reveals that the legacy which is inherited is not a recipe for baking, but than manner in which the two protagonists express their deep caring and protectiveness of one another by not expressing these openly.
“i don’t want to know how to make no rolls”with her lips poked out
Topic: Identity / Belonging
Significance: On the surface, this quotation highlights a classic generational clash. The child's defensive stance ("lips poked out") shows her trying to assert an independence from grandmother's attempt to impose traditional expectations.
“i want chu to learn how to make rolls” said the oldwoman proudly
Topic - Cultural heritage / family
Why it matters: Baking the rolls is not just a cooking instruction but the grandmother expressing her domestic heritage and ensuring its survival with pride and identity she wants it to pass on because it is apart of her identity.
“yes, ma’am”
Label: Characterization / Dialogue
Explanation: Giovanni used “African American Vernacular English” and behavioral description also hence “lips poked out” to create a realistic and cultural interaction between the characters. The switch from polite 'yes, madam' shows a transition of attitude which suggests an emotional fear of eventual loss that the child is covering up using acts of independence.
“lordthese children”
Question: Is the grandmother's understanding to the girls actual motives highlighted by the reaction she gives? Is she angered by her stubbornness or secretly understood the emotional attachment and fear the girl has?
when the old one died she would be lessdependent on her spirit
Question: What do you understand by the word 'dependent'? What is being criticised, dependence of the childhood on the other or a beauty expression of spiritual relation that the child does not want to get damaged?
even if she couldn’t say it
Pattern 2: Repetition of Unspoken Thoughts ("say/said/meant")
Passage: even if she couldn’t say it, so she said, never said what they meant
Significance: Repeatedly used is a form of the word say that emphasizes the key irony of the poem: language is uttered, but there is no communication. Love is felt and acted on, yet it is never said.
and i guess nobody ever does
Label: Speaker / Tone
Explanation: The speaker is an omniscient, reflective observer, emerging only at the end and changes from a seemingly nostalgic memory of a distant past recounting to a slightly cynic but empathetic commentary on human loneliness and failure to communicate.
and the old woman wiped her hands
Module 2: Who gets to belong, speak, and succeed in society and who decides?
The text addresses the dialogue that happens when some people " speak" about themselves, others " listen" to them; with the tools they possess, either through the "African American Vernacular English" adopted by the grandmother or in the childhood expression of the daughter through " lips poked out" when society on hand dictates that certain speech must conform to formalized rules of diction. Not only are the terms of their conversation in their own little household their own choices and they are still left with broken conversation where they cannot express what they mean; true " belonging" becomes complicated where there is this gap; love, depending on the few terms society give, cannot be said.
i
Pattern 1: Lowercase Structure and Lack of Punctuation
Passage: He entire poem uses lowercase letters (even for "I") and avoids periods or commas until the final implied pause.
Significance: The conversational, stream-of-consciousness layout resembles the movement of memory as well as oration. The grandmother and granddaughter are depicted with no obvious lines or barriers which conveys how entangled are their, lives as well as their spirits, together their memories and legacies together.
Legacies
Prediction: Given the title "legacies", it is likely that the text deals with traditions, memories or emotional habits that continue to exist within a family throughout different generations, in spite of tensions or unwillingness among family members.
Question: Why did the author entirely lowercase the title and the text? What does this suggest about the tone/format of the memory?Bold
eLife Assessment
This valuable study investigates the neural basis for recovery of complex wheel running behaviour following a unilateral spinal cord injury in mice. By combining behavioural analyses, whole-brain mapping, and tracing techniques, the authors provide incomplete evidence that new cortico-medullary connections can drive effective motor recovery. The paper could be strengthened with manipulations to establish causality, a more fine-grained analysis of the behaviour, and some reorganisation of how the data are presented and discussed.
Reviewer #1 (Public review):
Summary:
The authors seek to understand and identify the neural plasticity that underlies recovery from precise unilateral hemi-pyramidotomy. The corticospinal tract is severed on one side in the pyramids below the exit of corticoreticular projections. Recovery from the injury is achieved with an intensive wheel running rehabilitation regime. The anatomical sites of plasticity, the importance of plasticity in different reticular areas<br /> to recovery, and the impact of the degree of plasticity observed on recovery as correlated predictors, are shown.
Strengths:
Refined anatomical analysis using mouse line and genetic and viral intersectional tracing identifies specific reticular targets of likely enhanced cortical control that correlate with recovery of locomotor skill.
Weaknesses:
(1) The study is correlational at this time. This does not undercut the value of the data and the identification of targets of plasticity achieved in the work.
(2) Generalization of motor gains beyond locomotion was not tested. Reach-to-grasp tasks for feeding were not tested.
(3) Some discussions and use of the terms fine motor and skilled motor are fuzzy, and the limitations of the study are not sufficiently clearly stated.
Reviewer #2 (Public review):
Summary:
Bonanno and colleagues combine unilateral pyramidotomy, continuous voluntary complex-wheel running, whole-brain intersectional CSN tracing, and c-Fos mapping to ask whether rehabilitation reorganizes the supraspinal collaterals of the intact corticospinal tract neurons. The study is technically ambitious and competent, the uPyX + complex-wheel + intersectional-tracing + BrainJ combination is smart and interesting, the behavioral effect is convincing, and the blinding and exclusion criteria are explicit. The central anatomical finding - a CSN-specific, whole-brain projectome comparison with subregional LPGi/GiA/MdV granularity - is a legitimate contribution that builds on Asboth 2018. However, the strength of evidence does not support the strongest causal wording in the current abstract, significance statement, and parts of the discussion: the results remain correlational, the MdV-behavior correlation is modest, and its significance is sensitive to the unit of analysis. A major revision is recommended, primarily of framing and quantitative robustness, rather than because the central dataset is unconvincing.
Strengths:
(1) Technically ambitious and technically competent study addressing a relevant gap: brain-wide mapping of intact-CSN reorganization under continuous voluntary rehabilitation.
(2) The combination of uPyX, complex-wheel running, intersectional tracing, and BrainJ whole-brain projection analysis is novel and well integrated.
(3) Behavioral effect is convincing, blinding, and exclusion criteria are explicit.
(4) The central anatomical finding (CSN-specific whole-brain projectome under rehab, with LPGi/GiA/MdV subregional resolution) is a legitimate contribution that builds on Asboth 2018. The closest recent works (Lemieux et al. 2024, Jeleva et al. 2026) study reticulospinal rather than CSN plasticity and are complementary rather than competing.
Weaknesses:
(1) Causal framing extends beyond what the current evidence supports.
The abstract and significance statement present MdV as a potential mediator, or even a central locus, through which rehabilitation re-establishes descending control of the impaired limb. This is stronger than the evidence. What the paper shows is that CSN collateral projection density in MdV has a mild-to-medium correlation with behavioral recovery, and that this region is already known from prior work (Esposito 2014) to be relevant for skilled forelimb function. That is an interesting anatomical correlation, not a demonstration of mediation. No manipulation of MdV or of MdV-projecting CST terminals is performed; there is no silencing, no pathway-specific perturbation during rehabilitation, and no test showing that the identified sprouting is necessary for recovery. The limitations section acknowledges this, but the prominent claims do not.
(2) The behavioral caveat on what is actually novel.
The cleanest way to state what is genuinely new, clearer than the abstract itself, is this: when a CSN population loses part of its spinal target domain (via contralateral uPyX denervating the opposite cord), some CSNs from the opposite cortex appear to redirect growth into brainstem collaterals (LPGi, GiA, MdV). The compensation is plausibly sufficient to restore gross descending drive to the impaired forelimb, but most probably inadequate for the fractionated, cortico-motoneuronal fine-grain control that the direct CST normally provides. That distinction - recovery of drive and even skilled locomotor control vs. recovery of fine precision - is consistent with the ladder-rung improvements the paper reports (footfall counts are an integrated gross-placement metric) and with the skilled-reaching literature (Esposito 2014 and similar), which suggests precision grip and digit individuation would not be fully recovered by an MdV-centered detour. This note is also translationally important when we ask what humans consider fine motor control, which is mostly object manipulation. Relatedly, the ladder task is "skilled" in the operational sense that it requires cortical control, but the motor output measured (gross paw placement, overreach) is not fine motor function in the sense of digit individuation, grip force modulation, or pellet manipulation. "Skilled" here does not even mean *acquired* skill: classical skilled reaching in rodents involves explicit training to acquire a novel motor program, whereas here mice are only habituated. The brainstem-compensation hypothesis is more comfortable with restoring cortex-dependent gross placement than with restoring acquired fine-motor skills.
(3) The anatomy sample is modest for the precision of the claims.
Projection analysis rests on n = 9 pooled controls, n = 5 uPyX−Rehab, and n = 5 uPyX+Rehab. For a whole-brain subregion analysis, this is not a large dataset, even with the sensible restriction to the Wang et al. spinally-projecting set. The three medullary hits are plausible, but some of the most specific conclusions rely on a relatively small number of animals for its most specific claims. This matters especially for the MdV-behavior correlation.
(4) Normalization enforces a zero-sum structure.
Projection density is normalized to the total CST tract signal. This is a reasonable way to control for tracing variability, but it imposes a relative structure on the data: an apparent increase in one region may partly force an apparent decrease elsewhere. This may matter and has to be looked into by the authors, because the manuscript interprets decreased density in some other targets as meaningful redistribution.
(5) The decision to merge PMn and MdV under a single "MdV" label needs more justification.
Since the discussion relies on prior literature assigning skilled forelimb function to MdV proper, the reader needs to know whether the signal truly localizes there or whether it may partly reflect a neighboring region grouped under the same atlas label. Related to this, laterality would be very informative: since the proposed compensatory route is anatomically directional, showing whether the increased signal is preferentially located on the expected side of the medulla would strengthen the interpretation.
(6) The c-Fos / Fig. 3 section goes beyond what the data directly support.
The section "Complex-wheel running recruits intact corticospinal neurons" and the figure title "Rehabilitation functionally recruits intact CSNs" go beyond the actual observation, which is that a higher fraction of CSNs in M1 and M2 are c-Fos+ in runners than in non-runners. "Functionally" is not supported: c-Fos is a transcriptional marker of recent activity, not a functional readout; it does not show that the CSN's output is used to drive behavior. "Rehabilitation" is not supported either: the contrast is runners vs non-runners, applied uniformly across Sham and uPyX groups - healthy Sham+Rehab animals are on wheels for leisure, and the c-Fos effect is present in them too. The finding is difficult to interpret without thinking of the simpler framing ("moving mice have more motor cortex activity than resting mice"), with no control for generic arousal or ambulation. This section is the softest link in the causal chain running - CSN activity - medullary sprouting - recovery.
(7) MdV-recovery correlation: unstated multiple-comparison correction and possible pseudoreplication.
The correlation (R² ≈ 0.33, p ≈ 0.01) is the backbone of the paper's "causal" claim. Panels L/M/N test three correlations (LPGi, GiA, MdV vs forelimb footfall recovery); only MdV is reported as significant. The Figure 5 legend applies Tukey adjustment to the t-tests in A-C but makes no analogous statement for the correlations in L-N. A 3-test Bonferroni (α = 0.017) would not flip the MdV result, but disclosure is warranted, and the three tested regions were pre-selected from the significant group contrasts in A-C, which, to a statistician, would further shrink effective α. More importantly, the figure legend states that closed and open circles represent CFA- and RFA-traced values, respectively, which suggests the correlation treats the two tracer channels per mouse as independent datapoints - doubling the apparent n (≈ 20 from 10 uPyX mice), with the result of a higher significance than one would have at the mouse level.
(8) Reporting issues.
The reader would benefit from judging statistical choices such as those above directly from a data table rather than interpreting the authors' choices. The SciScore rightfully flags multiple missing components of transparent reporting: missing RRIDs, no code availability, limited data availability, and no power calculation, among others.
Almost all these weaknesses can be addressed with a revision of the manuscript, especially in the framing of results.
Conclusion:
The core message - that rehabilitation is associated with a selective pattern of CSN collateral remodeling in the motor medulla, and that MdV projection density covaries with behavioral recovery - is defensible from the data and already a useful result. The current wording in parts of the abstract, significance statement, and discussion goes beyond this and implies a mechanistic conclusion (mediation, central locus, re-establishment of descending control) that the data do not yet establish. The manuscript would better match its evidence with "associated with", "correlates with", or "candidate locus" framing, unless a causal experiment is added.
Reviewer #3 (Public review):
Summary:
In this study, Bonanno et al. show that after a lesion of the corticospinal tract (CST), rehabilitation running in a complex wheel drives improvement in skilled forelimb performance in mice. Mice with unilateral CST injury can perform gross motor tasks (locomotion) at the same level as the non-injured mice, but injured mice still have deficits in another task involving fine motor control. Thus, it is well-suited to test the efficacy of locomotion-based rehabilitation in fine motor control. Mice that voluntarily engaged in the rehabilitation protocol improved in the fine motor control task more than those mice that did not perform any rehabilitation. Highlighting the role of rehabilitation in the recovery of motor function after the lesion.
The authors aimed to study rehabilitation-driven intact CST sprouting to supraspinal areas. They identified one area in the motor medulla where rehabilitation significantly changes the projection density from the intact cortical spinal neurons. Interestingly, this area has ipsilateral connections and thus could be a pathway to convey motor commands from the intact corticospinal tract to the denervated area. However, as the authors acknowledge in the discussion, they only found a correlation between the change in the synaptic projections from intact CST to the medulla and the recovery. Future work should study if indeed the area of the motor medulla identified here increases its ipsilateral projections to the denervated area, confirming the re-routing of motor commands from the intact cortico spinal tract to the denervated area. The paper is strong and, in general, claims are supported by the data.
Strengths:
In this study, Bonanno et al. show that after a unilateral corticospinal tract lesion (CST), locomotion rehabilitation can improve motor function and improvements generalized to tasks that require fine motor control. Moreover, it identifies a potential pathway that could be used for the intact corticospinal tract to convey motor commands to the denervated area. The pathway identified here could become a target for rehabilitation therapies.
Weaknesses:
As the authors acknowledge in the discussion of the study, the main limitation of this study is that the reorganization observed at the motor medulla is only correlational. Thus, it is possible that the adaptation to running with an injured limb of the intact CST to adapt to an injured limb rather than a re-routing of the intact CST inputs to the denervated area underlies the synaptic changes observed in the motor medulla.
The statistical analysis could be better described.
The generalization of skilled movement is limited to only locomotion tasks.
eLife Assessment
The worldwide decline in the health of coral reefs is well documented, and overgrowth by microbial consortia can be a contributing factor. Kelman and colleagues used metagenomic analysis to interrogate potential changes in phage-associated genes predicted to be involved in central carbon metabolism. The study addresses the hypothesis that metabolic genes associated with carbon metabolism that are encoded by viruses reflect the health of the corals. The study contributes a valuable perspective on the potential role of phages in coral health, although limitations of the data and analyses offer an exploratory examination rather than a definitive result. Overall, the evidence supporting the major findings is incomplete, in part because the conceptual model relies on qualitative assumptions rather than empirical data.
Reviewer #1 (Public review):
Summary:
Microbialization (bacterial overgrowth) is a recognized component of degraded, eutrophied coral reefs where there is a shift from coral to algal dominance on the benthos. In addition, previous work has demonstrated that virus communities shift from a lytic strategy dominated (kill-the-winner) to a temperate (lysogenic) strategy dominated with reef microbialization. Kelman et al. sought to leverage previously published virus metagenomes produced from the water column of healthy and degraded coral reefs to assess virus community metabolic shifts. The authors also produce a conceptual model to demonstrate the potential impact of the observed metabolism shifts on reef fates.
Strengths:
The main strength of the manuscript is the findings from their metagenomic analyses and results. The virus metagenomes were produced using established approaches in the field and yield sufficient data per sample for their analyses. Interesting results regarding the shift in the types of genes from anaplerotic to cataplerotic provide the foundation for testable hypotheses to determine the magnitude of impact virus strategies have on reef health. The introduction is also well written and sets up the scene very well.
Weaknesses:
(1) The methods text currently omits important information related to the sampling design. It is not clear how many metagenomes are from healthy and degraded communities. This impacts the interpretability and robustness of the statistical results. Furthermore, it is unclear if analyses are based on assembled contigs or read-based alignments. Improving the clarity and organization of the Methods is essential for reproducibility.
(2) Regarding the bioinformatics approach, normalization using the "percent known" approach within samples may not fully account for discovery bias related to sequencing depth. While Supplementary Table 1 shows variability in read counts, the lack of community-level metadata makes it difficult to determine if sequencing depth covaries with community type (healthy vs. degraded). The study would benefit from a rarefaction analysis or subsampling to ensure that gene frequency trends and Spearman correlations are biological signals rather than artifacts of sequencing effort.
(3) The qualitative model in Figure 5 is positioned as evidence for the role of viruses in reef health, but it does not provide independent support for the authors' hypotheses. Since the model is parameterized using "arbitrary units" to reflect the authors' assumptions rather than being derived from the empirical metagenomic data, it serves as a helpful illustration of a hypothesis but not as a validation of the findings.
(4) Results and discussion require revisions to improve readability and connectivity across sections. Ensuring a clear distinction between empirical data and model-based speculation would help the audience better appreciate the science.
Reviewer #2 (Public review):
Summary:
The manuscript by Kelman and coauthors investigates how viral communities differ in the genes they encode in healthy and degraded coral reef ecosystems. Across 19 viral metagenomes from Central Pacific reefs, the authors assess the frequency of integration/excision genes as a proxy for viral community temperateness and ask whether genes associated with central carbon metabolism covary with signatures of temperateness. The main finding is that viral communities with more temperate-related genes encode more genes from the Entner-Doudoroff pathway and other reactions interpreted as anaplerotic, whereas more lytic-associated viral communities show greater representation of some pentose phosphate pathway, TCA, and redox-associated genes interpreted as cataplerotic. The authors propose a model based on these patterns in which lytic viral metabolism helps suppress bacterial overgrowth on healthy reefs, while temperate viral metabolism may promote microbialization on degraded reefs. The study addresses an interesting and potentially important concept - that viral auxiliary metabolic genes are important components of microbial communities and can affect ecosystem functioning. Linking viral metabolism to coral reef microbialization is a creative conceptual advance. The manuscript is clearly written, and the reported enrichment of anaplerotic genes in temperate-associated viromes is an interesting pattern that could motivate future work on how viral metabolic potential varies across reef states.
Strengths:
(1) The study connects viral lifestyle, central carbon metabolism, bacterial overgrowth, and reef degradation in a framework that could be useful for future studies of coral reef ecosystems and viral ecology. This is an interesting synthesis that links viral auxiliary metabolism to broader questions about microbialization and reef state.
(2) The manuscript is generally clearly organized around a testable prediction: viral metabolic gene content should vary along a lytic-to-temperate viral community gradient. The reported enrichment of anaplerotic genes in viromes with a larger fraction of temperate viruses is a compelling result.
(3) The authors highlight several virus-encoded metabolic genes that may not have been previously reported in viral datasets or genomes. If supported by further validation, these observations could expand the known repertoire of viral metabolic potential.
(4) The modeling helps clarify the feedbacks the authors propose may connect viral lifestyle, bacterial metabolism, and coral reef degradation. It provides a foundation for generating hypotheses about how viral metabolic genes could influence reef microbial dynamics.
Weaknesses:
(1) The main limitation is that the evidence for several key claims remains indirect. The core analysis is based on correlations between metabolic gene frequencies and integration/excision-related genes. This does not demonstrate that the metabolic genes occur in temperate viral genomes, are physically linked to lysogeny genes, are expressed during infection, or alter host metabolism. Thus, the data support an association between VLP-associated metabolic annotations and a community-level temperateness proxy, but not a direct link between temperate phages and these metabolic functions.
(2) It is important not to equate community-level gene frequencies with genome-level or infection-level metabolic programs. A virome may contain more anaplerotic genes overall, but that does not demonstrate that individual viruses reprogram their hosts in an anaplerotic manner nor that infection produces a net anaplerotic effect. Individual viruses may encode both anaplerotic and cataplerotic genes, and a smaller number of cataplerotic genes could have stronger metabolic consequences depending on expression, enzyme efficiency, pathway position, and host context. This is an important limitation that should be acknowledged and, if possible, addressed with contig- or genome-level analyses.
(3) The ecological interpretation assumes that viral infection is strong enough to influence reef-scale bacterial population dynamics. However, the study does not directly measure infection frequency, lysis rates, viral production, burst size, lysogeny frequency, prophage induction, gene expression, or bacterial mortality. If viral mortality or lysogenic conversion were rare in these systems, the observed gene-frequency patterns could have limited ecosystem-level consequences. This makes claims about viral metabolism suppressing bacterial overgrowth, accelerating microbialization, or acting as a conservation lever more speculative than suggested.
(4) There are statistical limitations related to the use of relative gene frequencies. Because genes are normalized as percentages of known genes, the data are compositional. Apparent increases in some categories may partly reflect decreases in others. Bootstrapped Spearman correlations are useful for assessing the robustness of these associations, but they do not address compositionality or multiple testing.
(5) The anaplerotic/cataplerotic classification is central to the manuscript's conclusions and would benefit from more support. The framework is useful, but it depends on both annotation confidence and biochemical context. Sequence-similarity annotations alone may be vulnerable to misannotation, especially for central metabolic enzymes that share conserved domains across functionally distinct proteins. Stronger evidence that key genes contain key functional domains and/or are phylogenetically related to characterized enzymes would help support the proposed functions. In addition, many central carbon enzymes are reversible or context-dependent, so a clearer rationale for each classification would strengthen the interpretation.
Overall, the manuscript presents a valuable hypothesis and highlights new ecological patterns in coral reef viral metagenomes, but falls short of the evidence needed for the strongest claims. The work would be strengthened by analyses that directly link metabolic genes to viral genomes or lysogeny markers, address compositional effects, validate key annotations, and more clearly distinguish observed gene-frequency associations from hypothesized effects on infection, host metabolism, and reef state.
forcefully situates Indigenous tribes as people of the Holocene who are in an inevitable de-cline, thereby projecting onto them a fantasy of finitud
Settler apocalypticism projects the problem to a "fantasy" due to the nature of looking at it as post-apocylptic, therefore unable to be saved
a historic one that is still unfolding. “
Climate crisis is not a future problem, it is a problem we need to deal with now
climate crisis is an intensification of the already operative epistemologicaland environmental perturbations of colonial territorialization and resource extraction.
an argument from the paper
epistemology
the branch of philosophy concerned with the nature, origin, and limits of human knowledge
The “symbolic” value of his photograph does not lie in the question of whether or not itdemonstrates an exceptional variance in scientific terms; it represents the immediacy andurgency of a global ecological reality.
The point of the photograph
Setting
I need to notice setting because place and time shape the mood, conflict, and choices.
Plot
I need to follow the plot closely because event order explains the conflict and turning points.
Character
I need to study character because actions, speech, and choices show who a person really is.
Tone
I need to watch tone because it shows the writer's attitude and changes how a scene feels.
The kinematics of the system are given by
Notation here is incredibly confusing. x is used as a 4D full dimensional state vector in the form of [x, theta, x_dot, theta_dot] while x_1 and x_2 are the position vectors for the cart and pendulum in [x, y]. This isn't explained anywhere and is left to the reader to figure out.
o your author; try to become him. Be
This reminds me that reading should be open-minded, trying to understand the writer before judging the story.
SIM-Based Telecalling CRM?
Explore why a SIM-based telecalling CRM outperforms VoIP dialers in India. Learn how it improves call quality, reliability, compliance & sales team productivity.
Know More: https://callyzer.co/blog/why-sim-based-telecalling-crm-is-better-than-voip-dialer-india/
Need to have a meeting to discuss on the SecEng SecAd process
(PARKDALE & LYBDALE)
stolen pictures
Figure 5a shows the results of this analysis, with the locations of the transcriptomic crests observed by Shen et al. (24) indicated. While the null results do not perfectly recapitulate the reported iPOP transcriptomic waves, it is notable that despite the lack of any true signal, two clear crests are apparent in our null study, one in the early 40s and one in the early 60s. Also notable is the correlation between the sample size in the sliding window and the number of changing molecules that are reported (Figure 5B); this phenomenon applies to both LOESS+DE-SWAN and DE-SWAN alone and is discussed further in Section 4. The appearance of two crests at these time points based on random noise calls into question the validity of the conclusion that they represent true biological trends.
There is a recent comment on pubpeer showing that the original Shen et al., paper replaces the real participant ages with fabricated ages during the LOESS step which is responsible for the "waves" https://pubpeer.com/publications/D2C91E5E2E55CE7452B12E44EBE844#2
Was this analysis done using the corrected code or the same code from the original paper. The authors may want to look into this and address it.
weakening
test
Mount-VHD
对于Mount-VHD有可能你会遇到CommandNotFound错误,这种情况下可以从【磁盘管理】中看到这个磁盘的编号,或者用wmic diskdrive list brief (来自 https://is.gd/yrMw8K )查到——当然,都得先在磁盘管理中把这个vhdx给attach上去
How to ask for help from people who don't know you
Core Principle:
Establish You Are Worth Helping (People Before Projects):
Keep Context Concise and Connected:
Make the Request Easy to Accept:
Make it Easy to Say No:
Ultimate Boundary Condition:
I ported Kubernetes to the browser
kubelet binary.webernetes project is much lighter at ~140KiB gzipped.Map), adding unrequested helper functions, and omitting cases in table tests.webernetes and a real k3s cluster using the official kubernetes-client/javascript library.Best AI Note Takers — 2026
Overview of the AI Audio/Note-Taker Category
Two Key Product Dimensions
Triggered Recording Tools (The Currently Practical Category)
Always-Listening Devices (The "Second Brain" Category)
Legal, Ethical, and Social Boundaries
Future Market Trends
stochastic parrots
The examples are solid. these groups barely show up in the data to begin with, and then the filters go and strip out what little they did post.
with her gender (nurse, teacher)
Gender-job stat's a solid example. nobody coded that bias in, the model just picked it up from the training text. Bringing in Stochastic Parrots is a nice touch since it ties this to a real scandal, not just theory. Also looking back to the Gramsci point, train on existing culture, you inherit its biases.
large language models
it's a fascinating analogy, taking a theory from nearly a century ago and applying it to LLMs feels genuinely fresh. The author invited us to look at what "cultural hegemony" might look like in the age of AI.
because of cultural hegemony.
I agree that culture plays an important role in keeping social systems in place. Schools, the media, and other institutions shape the way people think about society and what they see as "common sense." As a result, people may accept the existing system without even realizing how much these cultural influences affect their views.
who weren’t exposed to much media or culture.
I agree that Europe had a rich cultural tradition, but I think the author's description of Russia may be an oversimplification. Even though many people were illiterate and had limited access to mass media, they were still influenced by local culture, religion, and community networks. Culture is broader than formal education or the media.
cement hegemonic values
Internet is already a non-stop mass "advertisement" that is already so entangled into our every day lives. Think about the number times an elementary classroom might use YouTube and expose students to ads. They suggest to young students who haven't clearly developed their sense of self how they should live, value, buy, eat, exercise, and so on. The focus on consumerism is something we may never get away from and have long term serious consequences to the world.
rank of the 42,458th
To be able to quantify someone's contribution to the LLM is a scary thought! And because LLM is using such vast number of texts to train AI without any checks and balances we will never truly understand the influence of all these views and values on people as we move forward.
‘average human’
How should we define view of "average human"? Who gets to make that decision of "average human"? What is "average"? Traditionally, the word average often referred to the largest number. So do we go by largest population number or largest religious beliefs or largest popular beliefs. If so, what happens to everyone else's views?
controversial political topics
We are already living in a world where it is not clear where the information we are reading about many of the political topics are coming from and who is behind the information. There's been a lot of speculations about the information manipulations related to elections and politics. AI will only add to that mass entanglement of information and misinformation.
One implication
Many young students (who grew up with the internet and constant devices around them) are consumers of the internet where they don't always think about what they are reading and the influence on them. AI based web searches further encourages this by providing only a "snippet" summary of information.
dominant English
Not only is English the more dominant language in AI models, but AI platforms tend to be built by newcomers. Forbes estimated that approximately 65% of AI companies in the US were founded by newcomers in 2023, but English was still the language the models were trained in. Language is such an important part of someone's culture and identity, and it is becoming a popular translation tool, but as it has been discussed there are limitations and biases towards "smaller languages."
superhuman intelligence
I find the term "superhuman intelligence" interesting because is it "superhuman" if it is artificially made?
the voices of people
AI as a conformity tool to try and align everyone with the cis, white, European/American, male perspective. I wonder/fear how this may impact newcomers to Canada and the US? From my Masters thesis, different academic cultures use AI differently. Some are more over-reliant on AI, some it is not usable. When someone comes to a new country that encourages the use of AI in some ways, plus the impacts on enculturation, the pressures of assimilation, etc., the biases that AI have towards marginalized group could be internalized or exacerbated? I'm curious to know other peoples thoughts on this!
fairness and justice
Piggy backing off the other comment on this section! We must ask what is the definition of "fairness" and "justice" but also in the larger scale (when it comes to policy/procedures/laws/etc.) who is creating that definition? Are there multiple perspectives at the table from diverse backgrounds? Or are these definitions being created by the ruling class and ultimately maintaining the existing inequitable structures/systems?
–
Several of you have added commentary to this, which I agree with them all! I would like to add that it's also important to ask who developed and implemented these "interlocking structures." To me, this sentence reads as these are separate structures that got caught up in cultural hegemony, but I think that it's important to note that these structures were also created by the ruling class (white, European, male).
LLMs are inherently conservative technologies
The author argues that LLMs mainly reproduce dominant cultural values because they are trained on existing texts. Using Gramsci's concept of the historic bloc, the author explains that these values become embedded in AI models and are difficult to change. However, I wonder if this is always the case, if LLMs will continue to evolve through updated data, and user interactions, if so, they seem to be shaped not only by the past but also by continuous social and technological change.
This Maori ML
I think this is an example of how AI can be used positively by supporting cultural survival when it is built with consent, local institutions, and linguistic diversity in mind.
“We must stop this brain from functioning for twenty years.”
This quote is incredibly telling. Nothing challenges hegemony more than diversity of thought.
This attack on diversity of thought is paralleled by the political climate we are witnessing in the united states under this administration.
It seems that there is a mounting war on knowledge (and diversity in all of its manifestations; race, nationality, gender, sexual orientation, and diversity of thought**). Both covertly and overtly attempting to silence and defund post-secondary institutions while also threatening our public's opportunity for development and access to objective and subjective information. Completely erasing all progress in EDI(ID) going as far as DOGE deleting archival photographs and records of aircrafts with the word gay in it's name.
This same sentiment seems to be echoing across boarders. Alberta and Ontario are also under attack in a multitude of ways. Ontario is now moving toward a one year program for training teachers, while the standard for the professional certification in other jurisdictions remains a 60 credit hour program including 24 weeks of practicum. Alberta teachers are experiencing unprecedented working conditions with enrollment outpacing new teaching positions, resulting in ballooning class sizes and the teacher strike in 2025
how machine learning models worked
I wonder if Mahelona explained the damage to the environment that is also caused by these learning models. I feel mentioning the repercussions on the planet would have made convincing the elders a little more difficult. Its a wonderful thing that the Maori language will survive this culling of minority human languages but something about the whole ordeal feels unfair. Like the Maori community is forced to participate in this multi-facetted situation (technological advancement, degradation of environment, commodification of human knowledge wherein the profits are given to those who didn't produce it) or become forgotten/irrelevant in the world being created by a careless few.
fragile
I find this fragility to be true for many of the social constructs we live with in society today. Whether it be gender norms, capitalism, or nationalism all are concepts that are held in place through institutional and social pressures. I often think about this when I have to make students stand for the national anthem each morning, why must I also participate in the enforcement of nationalism in my students, creating invisible boarders between "us" and "them"? But I also see resistance against other constructs like the "give-and-take" philosophy of capitalism, when students inherently come to their peer's aid or give away their snacks without expecting anything in return to ensure their friend doesn't go hungry for the day.
Timnit Gebru
Timnit Gebru was a co-lead researcher in Ethical AI at Google who was fired in 2020 for raising issues of discrimination in the workplace. I am connecting to Kimberly Krenshaw's views on intersectionality in that prior to this year, I did not recognize her name; despite Timnit being named as Nature’s Ten people who helped shape science and one of TIME 100’s most influential people.
I am reminded of the importance of seeking out diverse perspectives and scholars of colour is more important than ever, in the age of AI and the distillation of information.
Takiej kawy nie pij ⚠️ Powoduje raka żołądka (badanie 2026)
Time of Consumption & Cardiovascular Health
Temperature-Related Cancer Risks
Impact on Sleep Quality
Individual Variations & Metabolic Factors
Empty Stomach Consumption (Fasting)
Blood Pressure Concerns
Brewing Methods & Cholesterol Levels
29 tys. zł miesięcznie? Te zawody należą do najlepiej płatnych
(nil)
(nil) es el valor que representa null o nada en el lenguaje de programación Ruby.
the first packet defined without any ID_ITEMS is a "catch-all" packet that matches all incoming data (even if the data lengths don't match).
Normalmente, el sistema espera que un paquete de telemetría tenga una estructura exacta definida en el archivo tlm.txt. Esto incluye una longitud específica de datos y una lista específica de elementos (ID_ITEM) que se extraerán de esos datos. Si los datos que llegan del hardware tienen una longitud diferente o un formato no esperado, el sistema normalmente rechazaría el paquete o fallaría al intentar leerlo.
La Solución del "Catch-All" (Red de Seguridad): Si defines un paquete en tu configuración sin incluir ningún ID_ITEM (es decir, no dices qué campos específicos extraer), COSMOS trata ese paquete como un "recipiente genérico" o catch-all.
Id items are used to take unidentified blobs of bytes and determine which packet they are.
Un blob (abreviatura de Binary Large Object u objeto binario grande) es un conjunto de datos almacenados como un único elemento binario, sin que el sistema tenga que interpretar su contenido interno
In addition, reproductive justice demands sexual autonomy and gender freedom for every human being. The problem is not defining reproductive justice but achieving it"
Everyone should have the freedom to make their own choices about their body.
She added that Arab women were simultaneously exotified and “othered,” being asked if she knew how to belly dance and often mistaken as Muslim, even though she is Christian (p. 293).
People made wrong ideas about Arab women because of stereotypes.
In these ways, Delgado Bernal points to epistemology, “how we know what we know” as the popular definition says. Student of color epistemologies are not valued in schools often not beyond superficial celebrating of differences that also do not delve deeper into issues of discrimination due to the differences and other issues of inequities. Such epistemologies are exemplified by Delgado Bernal when she writes, What are often perceived as deficits for Chicana/Chicano students within a Eurocentric epistemological framework—limited English proficiency, Chicano and/or Mexicano cultural practices, or too many nonuniversity-related responsibilities—can be understood within a Chicana feminist perspective as cultural assets or resources that Chicana/Chicano students bring to formal educational environments (2013, p. 397).
Students of color have knowledge and strengths that schools often do not value.
Paulo Freire (1970) describes dehumanization as when people are considered less-than-human and that their status as humans is different than what it should be. Being humanized means they should have the ability to pursue their hopes and dreams, some of the very things that make them so human (p. 44).
Treating people like they are less than human is wrong. Everyone deserves respect.
places. Next ?~ir own city park. Now_ . ." ._the Negroes' only weapon of defense has faded, the ballot. ... Politicians no longer fear the wrath f the Negro vote.
Another book I am reminded of from this reading is Ralph Ellison’s The Invisible Man. In it Ellison has this passage: “ these white folks have newspapers, magazines, radios, spokesman to get their ideas across. If they want to tell the world, a lie, they can tell it so well that it becomes the truth; And if I tell them that you’re lying, they’ll tell the world, even if you prove you’re telling the truth. Because it’s the kind of lie they want to hear.” I think this quote is fitting for how racism in its many forms persists. They tell themselves lies and disguise them as facts. Such as with the case of segregation and taking away a vote. They tell themselves that it is “fairer” to both white and black folk, and people believe it because they want to believe it. Believing a pretty lie is much easier than accepting the ugly truth.
Other school districts also used racial gerrymandering to preserve racial separation.
I believe gerrymandering is racially charged to this day. If districts are formed around the poorest of poor and richest of rich, the poorer districts receive less funding than the more wealthy districts. Take the case of Texas unlawful gerrymandering of 2025 in which the “Texas’s GOP-controlled legislature aggressively redrew its congressional map to target the political power of communities of color and try to create 5 more Republican seats in time for the 2026 midterms.” Not only does this affect voting but it affects education. It effects education funding but also how those votes are now distributed to silence people of colors voice on educational decisions in our government.
Although some racial separation was due to the burgeon-ing residential segregation of northern cities, much of it resulted from specific actions taken by local school officials to preserve racial sepa-ration.
As I continue reading about the once (mostly) unsegregated states shifted to segregation I am somewhat bewildered by how much racism is exacerbated by outside contexts like the war or economy. Richard Wright wrote in 1945 in his book Black Boy, “ watching the white people eat would make my stomach churn and I would grow vaguely angry. Why could I not eat when I was hungry? Why did I always have to wait until others were through? I could not understand why some people had enough food and others did not.” Wrights question fits with the circumstances of why and how racism is intensified by things like the economy. It comes down to greed, and fairly obviously power. White supremacy elevates the needs of white people and their hunger above black peoples. It is a system that tells them to “wait their turn” and that serves white people first in every way (whether that be educationally, economically, or industrially).
The arrival of soutl1ern blac~s provoked profound a~1xiety in many northern whites.
About a year ago I read a book called 12 Million Black Voices by Richard Wright. The book went into heavy detail about the Great Migration and the different Key “personae” that impacted the black community as well as overlapped in terms of economic context as Black people did. In the book there is the Black community, the lords of the land (descendants of the slave owning class who still make the formerly enslaved work as sharecroppers on their plantation), bosses of the business (business owners/apartment complex owners), as well as the poor white. The poor whites were the ones situational context overlapped the most to the black community. They held power due to their whiteness, yet like black folk (to a degree) lacked economic power. This lack of economic power and inability to grow wealth made the poor whites fear and segregate the Black community. The bosses of the building liked it this way, because, rather than the poor whites blaming them it made Black people the “enemy.” This affected education too, because White people knew that education was a primary way to get into industry.
on-prem servers
On-prem servers (abreviatura de on-premises servers o servidores locales)
It also directs the Department of Justice, which currently pays several million dollars in user fees annually, to continue to pay PACER access fees
lol
“The reality is that if they don’t trust you, No. . . ay.”is going to happen anyw
Trust is important and I believe that part of that trust is that they know that you'll have good intentions and not evaluate their performance in a disciplinary way.
have
I tried to highlight this whole sentence!
What is our responsible/respectful/productive action when we face supervisors in this way? I'm growing in a way that focuses on controlling myself and nothing more and this is making me think about supervisors I've had who don't want to change and I can't make them. I can't force someone to show me respect, so I think to would be interesting to read more about what we can do to manage through some of these challenges. Of course I'm happy to do this reading to continue to work on myself as a supervisor as well.
mon écologie à moi, cela ne sera pas l’écologie des symboles, cela sera l’écologie à impact : l’énergie décarbonée avec le nucléaire et le renouvelable, la transformation de nos villes pour réduire les îlots de chaleur, la rénovation des logements, des hôpitaux, des écoles. Le chantier est immense. Je ne donne de leçons à personne.
Et donc, quel programme ?
Egrenant les futurs sujets de sa campagne, le candidat d’Horizons a également évoqué l’immigration, pour laquelle il promet de « sauver le droit d’asile en écartant fermement toutes celles et ceux qui l’utilisent à contre-emploi ».
Qu'est-ce que ça signifie ?
conférer davantage d’autonomie aux directeurs d’établissement scolaire pour en faire des « patrons »
ça j'aime moins...
chaque élève de France ait accès à un soutien scolaire universel, combinant assistant IA personnalisé et brigades de professeurs, voire d’anciens professeurs et d’étudiants volontaires
Comment techniquement le faire, et partout ? Même en outre-mer ?
M. Philippe « assume » en revanche de dire aux retraités qu’ils devront « contribuer davantage au financement de notre modèle social », « aux cadres et aux employés du secteur public et privé qu’il faudra travailler plus longtemps » et « à l’Etat, à ses agences, aux collectivités, que les Français attendent d’eux qu’ils se serrent la ceinture et donnent l’exemple ».
Personnellement, je trouve ça courageux, et ça, je respecte.
indicates more investigation, and the score was taken as the mean of the four aligned components (Figure 4).
Make sure Figures refer to figure and sub figure letter
Sony IMX708, wide-field-of-view varian
Also specify NoIR so that recordings can occur in low light conditions (under read light)
Pose estimation
Add a figure showing key points on the body (pose estimation skeleton)
For each session, ethanol intake was computed as grams of ethanol per kilogram of body weight (g/kg),
Body weight was measured before the first, fourth, and seventh sessions
Bottles were introduced into their home cages three hours into the dark phase, and ethanol was presented at the full 15% concentration from the first session without a graded ramp-up
Two water bottles were initially put into the cages after EPM so that mice could acclimate before drinking. EtOH bottles were put on around 1pm everyday
Mice were given 24 h access to 15% (v/v) ethanol versus water on Monday, Wednesday, and Friday across three weeks, for nine IA sessions total.
Rephrase to something not Monday Wednesday and Friday because it started on Tuesday and there was no weekend break like we usually do
CFW
Define CFW
three of which were significantly altered between the two groups
Should be 1 for resilient/susceptible and 2 for ctrl/sds
Note: This response was posted by the corresponding author to Review Commons. The content has not been altered except for formatting.
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Reviewer #1 (Evidence, reproducibility and clarity (Required)):
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
- Having said so, I realize that while they give information on the statistical test used, i.e. one-way ANOVA they miss to explain the post-test used to assess significance (i.e. Bonferroni, Fishers LSD, whatsoever). Please add this information.
We thank the reviewer for this comment. The figure legends have been updated to include more details of all the statistical tests used.
- Another issue that might underestimate the effects of HIV-1 infection on SNAT7 levels and vice versa of SNAT7 KD on HIV-1 replication is the non-single cell approach employed, i.e. WBlots. I assume that HIV-1 infection rates in macrophages are not super high, usually not exceeding 20-30%. So indeed the effects the authors observe could be much higher, when checking at the single cell level. I do not know about the SNAT7 ab, but all the other reagents should work via flow cytometry and could hence improve the readout a lot.
We agree with the reviewer and indeed, in previous studies on HIV-1 infection of human macrophages performed in the lab, we observed via immunofluorescence that the proportion of infected cells ranged from 20 to 40 %. At the time of submission, we did not have the possibility to label the native SNAT7 protein by immunofluorescence, as the commercial antibody used only works for western blotting.
In the meantime, we have been validating a new antibody (Proteintech) targeting SNAT7 for immunofluorescence. If this is confirmed, we will be able to detect and quantify HIV-1 p24 by immunofluorescence in SNAT7-depleted human macrophages and control cells, thus confirming our results in single-cell analysis.
Flow cytometry analyses are difficult to perform on primary human macrophages because these cells are highly adherent and must be detached first. The process induces significant cell death and damage. This is why we would prefer to carry out these analyses using immunofluorescence and microscopy on adhered cells. This option will be undoubtedly pursued.
- Furthermore the authors never commented about a dose-response effect in terms of HIV-1 infection levels. There is a MOI dependency described for Suppl.Fig.1 C-F, unfortunately the data is missing in the manuscript.
We apologize for this omission. The figures showing the increase in SNAT7 protein expression following HIV-1 infection at MOIs ranging from 0.05 to 0.5 were added to the new version of the manuscript (Supp. Fig. 1 C-F).
- Figure1: specify circulating T lymphocytes. I would expect to see levels of SNAT7 in PHA or CD3/CD28 activated lymphocytes versus resting T cells and a time course of SNAT7 levels upon activation. I think even though SNAT7 levels in T cells might be low, they could also be increased by HIV-1 infection and it is essential that the authors test for this. If not, the result is a valid negative control. For this they should employ HIV-1 primary strains with a tropism for T cells, or at least lab-adapted HIV-1 NL4-3
We thank the reviewer for this comment. Circulating T lymphocytes isolated from the blood of healthy donors are now referred to resting lymphocytes in the new version of the manuscript, as opposed to activated T lymphocytes stimulated with IL2 and PHA-P for several days (Fig. 1 A-C).
The expression levels of SNAT7, both at the gene and protein levels, are lower in resting or IL2/PHA-P-activated T cells than in macrophages from the same donors. As suggested, we will perform a kinetic of T-cell activation upon HIV-1 infection to investigate how SNAT7 expression varies in these conditions.
- Figure 2 again single cell measurements could reveal much more pronounced effects; it is a bit counterintuitive that siRNA #2 is more efficient in SNAT7 KD but has higher levels of HIV-1 replication in terms of Gag levels. I assume when looking at the stats it is always a comparison to the Ctl treated cells (C-G), but this is not entirely clear. Unify labeling as compared to the stats in Fig.2 I (this also applies for all the other figs).
We thank the reviewer for this comment. Fig. 2B indeed shows one of the different donors analyzed. However, protein quantification across six different donors shows that SNAT7 is more depleted with siRNA #2 (Fig. 2C), and that Gag Pr55 protein levels are consequently more reduced, than with siRNA #1 (Fig. 2D).
We use GraphPad Prism software to perform statistical analysis. Depending on the test used, the software automatically plots the comparison bar and displays the p-value above it. We changed the representation of statistics as suggested.
Figure 3: It is a bit odd that they finally conclude on RT as essential step that is reduced in the absence of SNAT7 and then they fail to provide statistical significance for this (Fig.3 panels F and G). One would expect that RT is much more affected given the huge effects on HIV-1 capsid and particle production shown in Fig.2 F, G and I.
The reviewer is right in pointing that we observed a stronger effect during the later stages of the viral cycle, from transcription of viral RNAs (Fig. 2I and Supp. Fig. 2G) to the production of viral particles in the supernatant (Fig. 2D-G), than during the earlier stage of reverse transcription (Fig. 3F, G). Also, it is also possible that we might have missed the peak in ERT/LRT production, which is transient.
It should be noted that SAMHD1 exhibits both dNTPase (Goldstone et al., 2011) and nuclease (Beloglazova et al., 2013) activities. The ability of SAMHD1 to restrict the virus, through dephosphorylation at T592, is mediated by its RNase activity (Ryoo et al., 2014), and not by the dNTPase activity (Welbourn et al., 2013; White et al., 2013).This could explain why SNAT7 exhibit a stronger impact on viral transcription than on reverse transcription.
Figure 4; again single cell flow measurements of SAMHD1, pSAMHD1 and p24 /SNAT7 might help to more clearly discriminate effects that are specifically induced upon infection or happen in virally infected cells. Maybe alternatively IF?
We thank the reviewer for this suggestion. As mentioned under comment #2, flow cytometry analyses are difficult to perform on strongly adherent primary human macrophages.
With regard to immunofluorescence, there is a technical limitation based on the species in which the antibodies are produced. The antibody that targets the native SNAT7 protein, which is currently being validated in our laboratory, is produced in rabbits. An anti-CAp24 antibody produced in goats can be used. It will then be necessary to co-label the cells with anti SAMHD1 and phospho-SAMHD1produced in mouse. We will try to find options to co-label the cells.
The wblot shown in panel D does not really reflect the point the authors want to make by the quantification in panels G-I. Primary data (D) suggests that SNAT7 KD reduces HIV-1 production even in the absence of SAMHD1. The quantification rather indicates that SNAT7 KD does not affect HIV-1 production in the absence of SAMHD1. This needs clarification/corroboration by orthogonal approaches.
We respectfully disagree with the reviewer.
Figure 4D shows a representative blot of the six donors analysed. As mentioned, the depletion of SNAT7 in the absence of SAMHD1 reduces the production of the viral proteins GagPr55 and CAp24 (see Fig. 4D). This is illustrated by the quantifications (Fig. 4G–I). Following treatment with Vpx, GagPr55 protein expression in SNAT7 KD macrophages is reduced by a factor of 2.6 for siRNA #1 (mean = 1.48, light grey bar) and by a factor of 1.83 for siRNA #2 (mean = 2.13, orange bar), compared to the control (mean = 3.9, pink bar) (Fig. 4G). Similarly, CAp24 protein expression was reduced by a factor of 2.2 for siRNA #1 (mean = 2.05, light grey bar) and by a factor of 1.36 for siRNA #2 (mean = 3.34, orange bar), compared to the control (mean = 4.52, pink bar) (Fig. 4H).
These differences are therefore consistent between the Western blot and the quantifications. However, they are not significantly different to those observed in cells treated with Vpx and depleted with control siRNA, suggesting that the viral restriction observed in SNAT7 KD cells is primarily due to SAMHD1.
Figure 5: show SAMHD1 and pSAMHD1 levels upon glutamine supplementation.
We thank the reviewer for this comment, we will perform the suggested experiment.
- I think the discussion is very thin, mainly summarizing the results; but fails to give broader context or critically discuss the limitations and further directions.
We thank the reviewer for this comment. The discussion will be modified further accordingly.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics. We respectfully disagree with the reviewer.
The cells used here imply greater variability than a cell line, but are also more relevant.
Indeed, the effects observed in the late stages of HIV-1 production are:
~80 % decrease in viral transcription compared to the control (Fig. 2I),
~85 % decrease in CAp24 protein expression compared to the control, as quantified by western blot (Fig. 2E), or ~90 % by ELISA measurement (Fig. 2F),
a reduction of more than 90 % in the release of infectious particles (Fig. 2G).
These results were all significant across donors, while SNAT7 depletion was always partial (Fig. 2C, between 31 to 62 % of depletion compared to the control in infected cells).
Therefore, the data were obtained from a mixture of depleted and non-depleted macrophages. This means that the results may be underestimated.
Together, our results show that SNAT7 is necessary for HIV-1 production.
However, reading the comments, we realized that our conclusions regarding reverse transcription were too strong. SNAT7 depletion does not affect viral fusion and reverse transcription. The manuscript was modified accordingly.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future.
For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes? We thank the reviewer for these questions.
To address the role of accessory viral proteins, we have already performed one experiment infecting hMDM with HIV-1 strains deleted for genes such as Nef, Vpr, Vpu and Vif, and have found no clear effect on SNAT7 protein expression compared to WT strains. As an alternative experiment, we could overexpress individual viral genes, such as Nef or Vpr, in HeLa cells and analyze their impact on SNAT7 expression by Western blot.
It is also possible that SNAT7 expression and recycling of lysosomal glutamine are modulated by the macrophage intrinsic immunity in response to HIV-1 infection.
The Thr592 motif of the SAMHD1 protein is phosphorylated by Cyclin A2/CDK1 and type 1 IFN in non-cycling cells, such as MDMs (Cribier et al., 2013). For now, the relationship between SNAT7 and SAMHD1 remains unclear. However, (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This has been added to the discussion to explain the relationship between the 3 partners.
**Referees cross-commenting** I think the comments from the other referees are reasonable and consistent with my assessment
Reviewer #1 (Significance (Required)):
Strength and limitations see above;
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
- Figure 1: SNAT7 expression was selectively enhanced upon differentiation of monocytes into macrophages but absent in CD4+ T cells. Though there is a claim of enhancement of SNAT7 expression upon HIV-1 infection of macrophages, RT-qPCR analysis shows the opposite trend (Fig 1E) and SNAT7 protein expression changes are modest. Statistical analysis in Fig. 1H needs to be revisited. The number of replicates vary for the lysates harvested at different day post infection, which might have an impact on the statistical test. To determine if SNAT7 expression enhancement is dependent on establishment of virus infection, as the authors imply, control lysates of virus infections in presence of replication inhibitors should be included.
We thank the reviewer for this comment. Indeed, there is a modest, but statistically significant increase in SNAT7 protein expression upon HIV-1 infection over time (Fig. 1G, H), without any modulation of SNAT7 gene expression (Fig. 1E). This indicates that the regulation of SNAT7 expression in this context is only at the translation level (i.e. increase of translation or stabilization of the SNAT7 protein).
As mentioned, Fig. 1H aggregates between 3 to 7 independent experiments on different donors depending on the infection time point. SNAT7 protein expression is increased already at 1 day post-infection and until 8 days. The statistical test used here, i.e. 2 way-ANOVA, compared Mock-infected and HIV-1-infected condition for each time point with the same number of donors. In this figure, the comparison is statistically different only at day 6 of the time course (7 donors). We agree that increasing the number of donors of the other time points could help to improve the statistical difference between control and infection condition.
We thank the reviewer for the suggestion mentioning the use of replication inhibitors in this experiment. We plan to use inhibitors of reverse transcription (Nevirapin) and integration (Dolutegravir).
The authors rely exclusively on western blot analysis for HIV-1 Gag expression in cell lysates as a measure of effects of SNAT7 on virus replication. Single cell analysis such as intracellular p24gag analysis by FACS should be included; this will provide a better measure of effects of SNAT7 onHIV-1 infection establishment.
We respectfully disagree with the reviewer for this question. Indeed, to evaluate the effects of SNAT7 on HIV-1 replication, we measured Gag Pr55 and Cap24 using a Western blot approach (Fig. 2B, D and E), but also assessed the quantity of Cap24 in the supernatants and lysates using an ELISA measurement, the quantity of infectious particles using TZM reporter cells, and total viral transcription or more specifically Gag Pr55 transcription using qPCR (Fig. 2F, G and I and Supp. Fig. 2G).
Regarding the quantification of CAp24 at the cell single level, please refer to comment #2 under Reviewer #1.
Knockdown of SNAT7 in MDMs was partial at best; only 30-50% decrease in expression (Fig 2C), but the effects on viral gene expression (Fig. 2I), p24 release and infectious particle production is dramatic (Fig. 2F and G). This discrepancy is not addressed. Does SNAT7 knock-down negatively impact virus particle release? Please note that the representative WB in Fig 2B does not correlate with the quantification in Fig. 2D. There are no p55gag or p24gag bands in SNAT7#1 siRNA condition (Fig. 2B)? Data could also be rearranged to follow the logical sequence of virus replication cycle (viral RNa expression followed by Gag expression, and then release).
We thank the reviewer for this comment. Our samples are indeed a mixture of SNAT7-depleted and non-depleted macrophages and RNA interference in these cells often leads to a decrease of 50 % of the protein expression.
To determine whether SNAT7 is involved in the release of particles, we quantified Cap24 in cell lysates and in the cell culture medium separately, and normalized the results to the total protein content. The absence of SNAT7 reduced the amount of Cap24 measured by ELISA in both samples to the same extent, showing that there is no storage of Cap24-positive viral particles inside the infected macrophages. These data were initially pooled in one graph (Fig. 2F), but separate graphs are now provided in new Supp. Fig. 2 E, F.
Regarding the western blot shown in Fig. 2B, please refer to comment #5 under Reviewer #1.
In the new version of the manuscript, we arranged the figures and placed the later stages of the viral cycle in Fig. 2 and the earlier stages, such as fusion, reverse transcription and transcription, in Fig. 3.
Data interpretation would be greatly improved by including infection controls (RT or integrase inhibitors) to confirm that measurements of viral RNA and Gag are indeed modulated by SNAT7 expression.
We thank the reviewer for this suggestion to include inhibitors of viral replication as controls. In our experiments, cells were Mock-infected in parallel as a negative control of viral detection. We provide the results in the new version of the manuscript to show that (i) there is no detection of viral or Gag RNA in the absence of the virus, (ii) the expression of viral genes measured in HIV-1-infected SNAT7-depleted cells is not different from Mock-infected cells, indicating almost complete inhibition of viral transcription (Fig. 3H and Supp. Fig. 3B), also confirmed at the protein level (Fig. 2B, D-F).
Figure 3: Decrease in SNAT7 expression in macrophages resulted in lower levels of early reverse transcripts. But surprisingly, LRT levels were not as affected by decreases in SNAT7 expression. The authors go on to suggest that decreases in early RT are due to loss of phospho-SAMHD1 and increases in catalytically active form of SAMHD1. Mechanistically this does not make sense: LRT should be similarly affected by increase in catalytically active SAMHD1. dNTP concentrations should be measured to determine if the rescue of RT is dependent on SAMHD1 dNTPase activity.
We thank the reviewer for this comment. LRT concentrations are very low in human macrophages and more challenging to detect than ERT concentrations. This might explain why the differences observed between the SNAT7-depleted and control conditions appear less pronounced for LRT than for ERT.
Furthermore, we cannot rule out the possibility that SNAT7 has a cumulative effect throughout the viral cycle. While reverse transcription remains statistically unaltered, and despite the reduced levels of ERT and LRT in SNAT7-depleted macrophages (Fig. 3 F, G), there is a significant impact on the transcription of viral RNAs (Fig. 2I) and Gag (Supp. Fig. 2G). This step may also be altered by the ribonuclease activity of SAMHD1 (Beloglazova et al., 2013; Ryoo et al., 2014).
Finally, with the help of Dr Baek Kim in Atlanta, we attempted to quantify dNTP concentrations in our human macrophages. Unfortunately, it was not possible to draw any conclusions, as the concentrations of dNTPs extracted from our cells were far too low.
Furthermore, it should be noted that SAMHD1 viral restriction through its phosphorylation at T592 is not correlated with its dNTPase activity (Welbourn et al., 2013; White et al., 2013), but with its ribonuclease activity (Beloglazova et al., 2013; Ryoo et al., 2014). This is supporting why SNAT7, by modulating the ribonuclease activity of SAMHD1, could have a greater effect on viral transcription than on reverse transcription.
There is lack of consistency in the data: p24 release upon SNAT7 depletion is highly variable. While there is a dramatic >90-95% decrease in p24 release (Fig. 2G), the effects are much more moderate in Fig. 4H (50-60% attenuation), even though siRNA-mediated depletion was similar across the data sets. The authors should comment on the variability in their findings.
We thank the reviewer for this comment, but believe that Figure 2E rather than Figure 2G is to be mentioned regarding the quantification of CAp24 by Western blot and to be compared with Figure 4H.
In Fig. 2E, we observed an average reduction of 85 % in CAp24 expression normalized to Clathrin HC expression across different donors for both siRNAs targeting SNAT7. For Fig. 4H, there was a 73 % reduction in CAp24 levels for siRNA #1 and a 56 % reduction for siRNA #2. In addition, it should be noted that the reduction in Gag levels is greater in Fig. 4G (between 77 % and 83 %) than in Fig. 2D (between 55 % and 72 %).
Therefore, there is some variation in the results obtained with the different donors, which could be explained by variations in Gag cleavage among donors, but this does not impact the conclusions for both figures.
SNAT7 is postulated to affect 2 steps in the virus life cycle: reverse transcription and viral transcription. But Vpx-mediated SAMHD1 degradation reversed both. Its not clear to me as to how SAMHD1 degradation impacts the role of SNAT7 in viral transcription. No explanation is provided.
We thank the reviewer for this comment. As suggested, we will perform experiments to assess the impact of Vpx-mediated SAMHD1 degradation on viral transcription.
Exogenous addition of glutamine only partially restored Gag synthesis and p24 release, which could be attributed to increased cytoplasmic levels and viral protein synthesis. What about effects on reverse transcription and viral gene expression?
We thank the reviewer for this comment. We will perform the suggested experiments to assess the impact of glutamine supplementation on viral transcription.
Reviewer #2 (Significance (Required)):
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Reviewer #3 (Evidence, reproducibility and clarity (Required)):
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn. Major Concerns: 1. The mechanistic depth is insufficient. The authors do not elucidate how glutamine regulates SAMHD1 T592 phosphorylation, whether through metabolite‑mediated control of kinases/phosphatases or via indirect effects.
We thank the reviewer for this comment. It is worth noting that (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity using drugs decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This is now further discussed in the discussion section of the manuscript.
The authors do not measure intracellular dNTP levels upon SNAT7 knockdown, which is the key functional substrate of SAMHD1. They also do not directly demonstrate that glutamine supplementation restores dNTP pools.
We thank the reviewer for this comment. Please, refer to comment #5 under Reviewer #2.
Extracellular glutamine only partially rescues viral production, implying the existence of transport‑independent functions of SNAT7 or additional pathways. This important observation is not discussed.
We thank the reviewer for this comment. The discussion has been modified accordingly.
It is suggested that the key findings be validated in immortalized THP‑1 cells differentiated into macrophage‑like cells by PMA.
We thank the reviewer for this suggestion but don’t really understand why this would strengthen our conclusions. Indeed, despite the known variability between donors and technical limitations to transduce cells, we chose human blood monocyte-derived macrophages as a relevant non-transformed model for HIV-1 infection of macrophages. They also represent to some extent the human diversity.
The Discussion section should be expanded to include the potential translational implications and limitations of the present study.
We thank the reviewer for this comment. The discussion points to some elements of potential translation and limitations of the study.
Reviewer #3 (Significance (Required)):
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience:This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
Reviewer #1 (Evidence, reproducibility and clarity (Required)):
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
- Having said so, I realize that while they give information on the statistical test used, i.e. one-way ANOVA they miss to explain the post-test used to assess significance (i.e. Bonferroni, Fishers LSD, whatsoever). Please add this information.
We thank the reviewer for this comment. The figure legends have been updated to include more details of all the statistical tests used.
- Another issue that might underestimate the effects of HIV-1 infection on SNAT7 levels and vice versa of SNAT7 KD on HIV-1 replication is the non-single cell approach employed, i.e. WBlots. I assume that HIV-1 infection rates in macrophages are not super high, usually not exceeding 20-30%. So indeed the effects the authors observe could be much higher, when checking at the single cell level. I do not know about the SNAT7 ab, but all the other reagents should work via flow cytometry and could hence improve the readout a lot.
We agree with the reviewer and indeed, in previous studies on HIV-1 infection of human macrophages performed in the lab, we observed via immunofluorescence that the proportion of infected cells ranged from 20 to 40 %. At the time of submission, we did not have the possibility to label the native SNAT7 protein by immunofluorescence, as the commercial antibody used only works for western blotting.
In the meantime, we have been validating a new antibody (Proteintech) targeting SNAT7 for immunofluorescence. If this is confirmed, we will be able to detect and quantify HIV-1 p24 by immunofluorescence in SNAT7-depleted human macrophages and control cells, thus confirming our results in single-cell analysis.
Flow cytometry analyses are difficult to perform on primary human macrophages because these cells are highly adherent and must be detached first. The process induces significant cell death and damage. This is why we would prefer to carry out these analyses using immunofluorescence and microscopy on adhered cells. This option will be undoubtedly pursued.
- Furthermore the authors never commented about a dose-response effect in terms of HIV-1 infection levels. There is a MOI dependency described for Suppl.Fig.1 C-F, unfortunately the data is missing in the manuscript.
We apologize for this omission. The figures showing the increase in SNAT7 protein expression following HIV-1 infection at MOIs ranging from 0.05 to 0.5 were added to the new version of the manuscript (Supp. Fig. 1 C-F).
- Figure1: specify circulating T lymphocytes. I would expect to see levels of SNAT7 in PHA or CD3/CD28 activated lymphocytes versus resting T cells and a time course of SNAT7 levels upon activation. I think even though SNAT7 levels in T cells might be low, they could also be increased by HIV-1 infection and it is essential that the authors test for this. If not, the result is a valid negative control. For this they should employ HIV-1 primary strains with a tropism for T cells, or at least lab-adapted HIV-1 NL4-3
We thank the reviewer for this comment. Circulating T lymphocytes isolated from the blood of healthy donors are now referred to resting lymphocytes in the new version of the manuscript, as opposed to activated T lymphocytes stimulated with IL2 and PHA-P for several days (Fig. 1 A-C).
The expression levels of SNAT7, both at the gene and protein levels, are lower in resting or IL2/PHA-P-activated T cells than in macrophages from the same donors. As suggested, we will perform a kinetic of T-cell activation upon HIV-1 infection to investigate how SNAT7 expression varies in these conditions.
- Figure 2 again single cell measurements could reveal much more pronounced effects; it is a bit counterintuitive that siRNA #2 is more efficient in SNAT7 KD but has higher levels of HIV-1 replication in terms of Gag levels. I assume when looking at the stats it is always a comparison to the Ctl treated cells (C-G), but this is not entirely clear. Unify labeling as compared to the stats in Fig.2 I (this also applies for all the other figs).
We thank the reviewer for this comment. Fig. 2B indeed shows one of the different donors analyzed. However, protein quantification across six different donors shows that SNAT7 is more depleted with siRNA #2 (Fig. 2C), and that Gag Pr55 protein levels are consequently more reduced, than with siRNA #1 (Fig. 2D).
We use GraphPad Prism software to perform statistical analysis. Depending on the test used, the software automatically plots the comparison bar and displays the p-value above it. We changed the representation of statistics as suggested.
Figure 3: It is a bit odd that they finally conclude on RT as essential step that is reduced in the absence of SNAT7 and then they fail to provide statistical significance for this (Fig.3 panels F and G). One would expect that RT is much more affected given the huge effects on HIV-1 capsid and particle production shown in Fig.2 F, G and I.
The reviewer is right in pointing that we observed a stronger effect during the later stages of the viral cycle, from transcription of viral RNAs (Fig. 2I and Supp. Fig. 2G) to the production of viral particles in the supernatant (Fig. 2D-G), than during the earlier stage of reverse transcription (Fig. 3F, G). Also, it is also possible that we might have missed the peak in ERT/LRT production, which is transient.
It should be noted that SAMHD1 exhibits both dNTPase (Goldstone et al., 2011) and nuclease (Beloglazova et al., 2013) activities. The ability of SAMHD1 to restrict the virus, through dephosphorylation at T592, is mediated by its RNase activity (Ryoo et al., 2014), and not by the dNTPase activity (Welbourn et al., 2013; White et al., 2013).This could explain why SNAT7 exhibit a stronger impact on viral transcription than on reverse transcription.
Figure 4; again single cell flow measurements of SAMHD1, pSAMHD1 and p24 /SNAT7 might help to more clearly discriminate effects that are specifically induced upon infection or happen in virally infected cells. Maybe alternatively IF?
We thank the reviewer for this suggestion. As mentioned under comment #2, flow cytometry analyses are difficult to perform on strongly adherent primary human macrophages.
With regard to immunofluorescence, there is a technical limitation based on the species in which the antibodies are produced. The antibody that targets the native SNAT7 protein, which is currently being validated in our laboratory, is produced in rabbits. An anti-CAp24 antibody produced in goats can be used. It will then be necessary to co-label the cells with anti SAMHD1 and phospho-SAMHD1produced in mouse. We will try to find options to co-label the cells.
The wblot shown in panel D does not really reflect the point the authors want to make by the quantification in panels G-I. Primary data (D) suggests that SNAT7 KD reduces HIV-1 production even in the absence of SAMHD1. The quantification rather indicates that SNAT7 KD does not affect HIV-1 production in the absence of SAMHD1. This needs clarification/corroboration by orthogonal approaches.
We respectfully disagree with the reviewer.
Figure 4D shows a representative blot of the six donors analysed. As mentioned, the depletion of SNAT7 in the absence of SAMHD1 reduces the production of the viral proteins GagPr55 and CAp24 (see Fig. 4D). This is illustrated by the quantifications (Fig. 4G–I). Following treatment with Vpx, GagPr55 protein expression in SNAT7 KD macrophages is reduced by a factor of 2.6 for siRNA #1 (mean = 1.48, light grey bar) and by a factor of 1.83 for siRNA #2 (mean = 2.13, orange bar), compared to the control (mean = 3.9, pink bar) (Fig. 4G). Similarly, CAp24 protein expression was reduced by a factor of 2.2 for siRNA #1 (mean = 2.05, light grey bar) and by a factor of 1.36 for siRNA #2 (mean = 3.34, orange bar), compared to the control (mean = 4.52, pink bar) (Fig. 4H).
These differences are therefore consistent between the Western blot and the quantifications. However, they are not significantly different to those observed in cells treated with Vpx and depleted with control siRNA, suggesting that the viral restriction observed in SNAT7 KD cells is primarily due to SAMHD1.
Figure 5: show SAMHD1 and pSAMHD1 levels upon glutamine supplementation.
We thank the reviewer for this comment, we will perform the suggested experiment.
- I think the discussion is very thin, mainly summarizing the results; but fails to give broader context or critically discuss the limitations and further directions.
We thank the reviewer for this comment. The discussion will be modified further accordingly.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics. We respectfully disagree with the reviewer.
The cells used here imply greater variability than a cell line, but are also more relevant.
Indeed, the effects observed in the late stages of HIV-1 production are:
~80 % decrease in viral transcription compared to the control (Fig. 2I),
~85 % decrease in CAp24 protein expression compared to the control, as quantified by western blot (Fig. 2E), or ~90 % by ELISA measurement (Fig. 2F),
a reduction of more than 90 % in the release of infectious particles (Fig. 2G).
These results were all significant across donors, while SNAT7 depletion was always partial (Fig. 2C, between 31 to 62 % of depletion compared to the control in infected cells).
Therefore, the data were obtained from a mixture of depleted and non-depleted macrophages. This means that the results may be underestimated.
Together, our results show that SNAT7 is necessary for HIV-1 production.
However, reading the comments, we realized that our conclusions regarding reverse transcription were too strong. SNAT7 depletion does not affect viral fusion and reverse transcription. The manuscript was modified accordingly.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future.
For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes? We thank the reviewer for these questions.
To address the role of accessory viral proteins, we have already performed one experiment infecting hMDM with HIV-1 strains deleted for genes such as Nef, Vpr, Vpu and Vif, and have found no clear effect on SNAT7 protein expression compared to WT strains. As an alternative experiment, we could overexpress individual viral genes, such as Nef or Vpr, in HeLa cells and analyze their impact on SNAT7 expression by Western blot.
It is also possible that SNAT7 expression and recycling of lysosomal glutamine are modulated by the macrophage intrinsic immunity in response to HIV-1 infection.
The Thr592 motif of the SAMHD1 protein is phosphorylated by Cyclin A2/CDK1 and type 1 IFN in non-cycling cells, such as MDMs (Cribier et al., 2013). For now, the relationship between SNAT7 and SAMHD1 remains unclear. However, (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This has been added to the discussion to explain the relationship between the 3 partners.
**Referees cross-commenting** I think the comments from the other referees are reasonable and consistent with my assessment
Reviewer #1 (Significance (Required)):
Strength and limitations see above;
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
- Figure 1: SNAT7 expression was selectively enhanced upon differentiation of monocytes into macrophages but absent in CD4+ T cells. Though there is a claim of enhancement of SNAT7 expression upon HIV-1 infection of macrophages, RT-qPCR analysis shows the opposite trend (Fig 1E) and SNAT7 protein expression changes are modest. Statistical analysis in Fig. 1H needs to be revisited. The number of replicates vary for the lysates harvested at different day post infection, which might have an impact on the statistical test. To determine if SNAT7 expression enhancement is dependent on establishment of virus infection, as the authors imply, control lysates of virus infections in presence of replication inhibitors should be included.
We thank the reviewer for this comment. Indeed, there is a modest, but statistically significant increase in SNAT7 protein expression upon HIV-1 infection over time (Fig. 1G, H), without any modulation of SNAT7 gene expression (Fig. 1E). This indicates that the regulation of SNAT7 expression in this context is only at the translation level (i.e. increase of translation or stabilization of the SNAT7 protein).
As mentioned, Fig. 1H aggregates between 3 to 7 independent experiments on different donors depending on the infection time point. SNAT7 protein expression is increased already at 1 day post-infection and until 8 days. The statistical test used here, i.e. 2 way-ANOVA, compared Mock-infected and HIV-1-infected condition for each time point with the same number of donors. In this figure, the comparison is statistically different only at day 6 of the time course (7 donors). We agree that increasing the number of donors of the other time points could help to improve the statistical difference between control and infection condition.
We thank the reviewer for the suggestion mentioning the use of replication inhibitors in this experiment. We plan to use inhibitors of reverse transcription (Nevirapin) and integration (Dolutegravir).
The authors rely exclusively on western blot analysis for HIV-1 Gag expression in cell lysates as a measure of effects of SNAT7 on virus replication. Single cell analysis such as intracellular p24gag analysis by FACS should be included; this will provide a better measure of effects of SNAT7 onHIV-1 infection establishment.
We respectfully disagree with the reviewer for this question. Indeed, to evaluate the effects of SNAT7 on HIV-1 replication, we measured Gag Pr55 and Cap24 using a Western blot approach (Fig. 2B, D and E), but also assessed the quantity of Cap24 in the supernatants and lysates using an ELISA measurement, the quantity of infectious particles using TZM reporter cells, and total viral transcription or more specifically Gag Pr55 transcription using qPCR (Fig. 2F, G and I and Supp. Fig. 2G).
Regarding the quantification of CAp24 at the cell single level, please refer to comment #2 under Reviewer #1.
Knockdown of SNAT7 in MDMs was partial at best; only 30-50% decrease in expression (Fig 2C), but the effects on viral gene expression (Fig. 2I), p24 release and infectious particle production is dramatic (Fig. 2F and G). This discrepancy is not addressed. Does SNAT7 knock-down negatively impact virus particle release? Please note that the representative WB in Fig 2B does not correlate with the quantification in Fig. 2D. There are no p55gag or p24gag bands in SNAT7#1 siRNA condition (Fig. 2B)? Data could also be rearranged to follow the logical sequence of virus replication cycle (viral RNa expression followed by Gag expression, and then release).
We thank the reviewer for this comment. Our samples are indeed a mixture of SNAT7-depleted and non-depleted macrophages and RNA interference in these cells often leads to a decrease of 50 % of the protein expression.
To determine whether SNAT7 is involved in the release of particles, we quantified Cap24 in cell lysates and in the cell culture medium separately, and normalized the results to the total protein content. The absence of SNAT7 reduced the amount of Cap24 measured by ELISA in both samples to the same extent, showing that there is no storage of Cap24-positive viral particles inside the infected macrophages. These data were initially pooled in one graph (Fig. 2F), but separate graphs are now provided in new Supp. Fig. 2 E, F.
Regarding the western blot shown in Fig. 2B, please refer to comment #5 under Reviewer #1.
In the new version of the manuscript, we arranged the figures and placed the later stages of the viral cycle in Fig. 2 and the earlier stages, such as fusion, reverse transcription and transcription, in Fig. 3.
Data interpretation would be greatly improved by including infection controls (RT or integrase inhibitors) to confirm that measurements of viral RNA and Gag are indeed modulated by SNAT7 expression.
We thank the reviewer for this suggestion to include inhibitors of viral replication as controls. In our experiments, cells were Mock-infected in parallel as a negative control of viral detection. We provide the results in the new version of the manuscript to show that (i) there is no detection of viral or Gag RNA in the absence of the virus, (ii) the expression of viral genes measured in HIV-1-infected SNAT7-depleted cells is not different from Mock-infected cells, indicating almost complete inhibition of viral transcription (Fig. 3H and Supp. Fig. 3B), also confirmed at the protein level (Fig. 2B, D-F).
Figure 3: Decrease in SNAT7 expression in macrophages resulted in lower levels of early reverse transcripts. But surprisingly, LRT levels were not as affected by decreases in SNAT7 expression. The authors go on to suggest that decreases in early RT are due to loss of phospho-SAMHD1 and increases in catalytically active form of SAMHD1. Mechanistically this does not make sense: LRT should be similarly affected by increase in catalytically active SAMHD1. dNTP concentrations should be measured to determine if the rescue of RT is dependent on SAMHD1 dNTPase activity.
We thank the reviewer for this comment. LRT concentrations are very low in human macrophages and more challenging to detect than ERT concentrations. This might explain why the differences observed between the SNAT7-depleted and control conditions appear less pronounced for LRT than for ERT.
Furthermore, we cannot rule out the possibility that SNAT7 has a cumulative effect throughout the viral cycle. While reverse transcription remains statistically unaltered, and despite the reduced levels of ERT and LRT in SNAT7-depleted macrophages (Fig. 3 F, G), there is a significant impact on the transcription of viral RNAs (Fig. 2I) and Gag (Supp. Fig. 2G). This step may also be altered by the ribonuclease activity of SAMHD1 (Beloglazova et al., 2013; Ryoo et al., 2014).
Finally, with the help of Dr Baek Kim in Atlanta, we attempted to quantify dNTP concentrations in our human macrophages. Unfortunately, it was not possible to draw any conclusions, as the concentrations of dNTPs extracted from our cells were far too low.
Furthermore, it should be noted that SAMHD1 viral restriction through its phosphorylation at T592 is not correlated with its dNTPase activity (Welbourn et al., 2013; White et al., 2013), but with its ribonuclease activity (Beloglazova et al., 2013; Ryoo et al., 2014). This is supporting why SNAT7, by modulating the ribonuclease activity of SAMHD1, could have a greater effect on viral transcription than on reverse transcription.
There is lack of consistency in the data: p24 release upon SNAT7 depletion is highly variable. While there is a dramatic >90-95% decrease in p24 release (Fig. 2G), the effects are much more moderate in Fig. 4H (50-60% attenuation), even though siRNA-mediated depletion was similar across the data sets. The authors should comment on the variability in their findings.
We thank the reviewer for this comment, but believe that Figure 2E rather than Figure 2G is to be mentioned regarding the quantification of CAp24 by Western blot and to be compared with Figure 4H.
In Fig. 2E, we observed an average reduction of 85 % in CAp24 expression normalized to Clathrin HC expression across different donors for both siRNAs targeting SNAT7. For Fig. 4H, there was a 73 % reduction in CAp24 levels for siRNA #1 and a 56 % reduction for siRNA #2. In addition, it should be noted that the reduction in Gag levels is greater in Fig. 4G (between 77 % and 83 %) than in Fig. 2D (between 55 % and 72 %).
Therefore, there is some variation in the results obtained with the different donors, which could be explained by variations in Gag cleavage among donors, but this does not impact the conclusions for both figures.
SNAT7 is postulated to affect 2 steps in the virus life cycle: reverse transcription and viral transcription. But Vpx-mediated SAMHD1 degradation reversed both. Its not clear to me as to how SAMHD1 degradation impacts the role of SNAT7 in viral transcription. No explanation is provided.
We thank the reviewer for this comment. As suggested, we will perform experiments to assess the impact of Vpx-mediated SAMHD1 degradation on viral transcription.
Exogenous addition of glutamine only partially restored Gag synthesis and p24 release, which could be attributed to increased cytoplasmic levels and viral protein synthesis. What about effects on reverse transcription and viral gene expression?
We thank the reviewer for this comment. We will perform the suggested experiments to assess the impact of glutamine supplementation on viral transcription.
Reviewer #2 (Significance (Required)):
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Reviewer #3 (Evidence, reproducibility and clarity (Required)):
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn. Major Concerns: 1. The mechanistic depth is insufficient. The authors do not elucidate how glutamine regulates SAMHD1 T592 phosphorylation, whether through metabolite‑mediated control of kinases/phosphatases or via indirect effects.
We thank the reviewer for this comment. It is worth noting that (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity using drugs decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This is now further discussed in the discussion section of the manuscript.
The authors do not measure intracellular dNTP levels upon SNAT7 knockdown, which is the key functional substrate of SAMHD1. They also do not directly demonstrate that glutamine supplementation restores dNTP pools.
We thank the reviewer for this comment. Please, refer to comment #5 under Reviewer #2.
Extracellular glutamine only partially rescues viral production, implying the existence of transport‑independent functions of SNAT7 or additional pathways. This important observation is not discussed.
We thank the reviewer for this comment. The discussion has been modified accordingly.
It is suggested that the key findings be validated in immortalized THP‑1 cells differentiated into macrophage‑like cells by PMA.
We thank the reviewer for this suggestion but don’t really understand why this would strengthen our conclusions. Indeed, despite the known variability between donors and technical limitations to transduce cells, we chose human blood monocyte-derived macrophages as a relevant non-transformed model for HIV-1 infection of macrophages. They also represent to some extent the human diversity.
The Discussion section should be expanded to include the potential translational implications and limitations of the present study.
We thank the reviewer for this comment. The discussion points to some elements of potential translation and limitations of the study.
Reviewer #3 (Significance (Required)):
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience:This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
Reviewer #1 (Evidence, reproducibility and clarity (Required)):
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
- Having said so, I realize that while they give information on the statistical test used, i.e. one-way ANOVA they miss to explain the post-test used to assess significance (i.e. Bonferroni, Fishers LSD, whatsoever). Please add this information.
We thank the reviewer for this comment. The figure legends have been updated to include more details of all the statistical tests used.
- Another issue that might underestimate the effects of HIV-1 infection on SNAT7 levels and vice versa of SNAT7 KD on HIV-1 replication is the non-single cell approach employed, i.e. WBlots. I assume that HIV-1 infection rates in macrophages are not super high, usually not exceeding 20-30%. So indeed the effects the authors observe could be much higher, when checking at the single cell level. I do not know about the SNAT7 ab, but all the other reagents should work via flow cytometry and could hence improve the readout a lot.
We agree with the reviewer and indeed, in previous studies on HIV-1 infection of human macrophages performed in the lab, we observed via immunofluorescence that the proportion of infected cells ranged from 20 to 40 %. At the time of submission, we did not have the possibility to label the native SNAT7 protein by immunofluorescence, as the commercial antibody used only works for western blotting.
In the meantime, we have been validating a new antibody (Proteintech) targeting SNAT7 for immunofluorescence. If this is confirmed, we will be able to detect and quantify HIV-1 p24 by immunofluorescence in SNAT7-depleted human macrophages and control cells, thus confirming our results in single-cell analysis.
Flow cytometry analyses are difficult to perform on primary human macrophages because these cells are highly adherent and must be detached first. The process induces significant cell death and damage. This is why we would prefer to carry out these analyses using immunofluorescence and microscopy on adhered cells. This option will be undoubtedly pursued.
- Furthermore the authors never commented about a dose-response effect in terms of HIV-1 infection levels. There is a MOI dependency described for Suppl.Fig.1 C-F, unfortunately the data is missing in the manuscript.
We apologize for this omission. The figures showing the increase in SNAT7 protein expression following HIV-1 infection at MOIs ranging from 0.05 to 0.5 were added to the new version of the manuscript (Supp. Fig. 1 C-F).
- Figure1: specify circulating T lymphocytes. I would expect to see levels of SNAT7 in PHA or CD3/CD28 activated lymphocytes versus resting T cells and a time course of SNAT7 levels upon activation. I think even though SNAT7 levels in T cells might be low, they could also be increased by HIV-1 infection and it is essential that the authors test for this. If not, the result is a valid negative control. For this they should employ HIV-1 primary strains with a tropism for T cells, or at least lab-adapted HIV-1 NL4-3
We thank the reviewer for this comment. Circulating T lymphocytes isolated from the blood of healthy donors are now referred to resting lymphocytes in the new version of the manuscript, as opposed to activated T lymphocytes stimulated with IL2 and PHA-P for several days (Fig. 1 A-C).
The expression levels of SNAT7, both at the gene and protein levels, are lower in resting or IL2/PHA-P-activated T cells than in macrophages from the same donors. As suggested, we will perform a kinetic of T-cell activation upon HIV-1 infection to investigate how SNAT7 expression varies in these conditions.
- Figure 2 again single cell measurements could reveal much more pronounced effects; it is a bit counterintuitive that siRNA #2 is more efficient in SNAT7 KD but has higher levels of HIV-1 replication in terms of Gag levels. I assume when looking at the stats it is always a comparison to the Ctl treated cells (C-G), but this is not entirely clear. Unify labeling as compared to the stats in Fig.2 I (this also applies for all the other figs).
We thank the reviewer for this comment. Fig. 2B indeed shows one of the different donors analyzed. However, protein quantification across six different donors shows that SNAT7 is more depleted with siRNA #2 (Fig. 2C), and that Gag Pr55 protein levels are consequently more reduced, than with siRNA #1 (Fig. 2D).
We use GraphPad Prism software to perform statistical analysis. Depending on the test used, the software automatically plots the comparison bar and displays the p-value above it. We changed the representation of statistics as suggested.
Figure 3: It is a bit odd that they finally conclude on RT as essential step that is reduced in the absence of SNAT7 and then they fail to provide statistical significance for this (Fig.3 panels F and G). One would expect that RT is much more affected given the huge effects on HIV-1 capsid and particle production shown in Fig.2 F, G and I.
The reviewer is right in pointing that we observed a stronger effect during the later stages of the viral cycle, from transcription of viral RNAs (Fig. 2I and Supp. Fig. 2G) to the production of viral particles in the supernatant (Fig. 2D-G), than during the earlier stage of reverse transcription (Fig. 3F, G). Also, it is also possible that we might have missed the peak in ERT/LRT production, which is transient.
It should be noted that SAMHD1 exhibits both dNTPase (Goldstone et al., 2011) and nuclease (Beloglazova et al., 2013) activities. The ability of SAMHD1 to restrict the virus, through dephosphorylation at T592, is mediated by its RNase activity (Ryoo et al., 2014), and not by the dNTPase activity (Welbourn et al., 2013; White et al., 2013).This could explain why SNAT7 exhibit a stronger impact on viral transcription than on reverse transcription.
Figure 4; again single cell flow measurements of SAMHD1, pSAMHD1 and p24 /SNAT7 might help to more clearly discriminate effects that are specifically induced upon infection or happen in virally infected cells. Maybe alternatively IF?
We thank the reviewer for this suggestion. As mentioned under comment #2, flow cytometry analyses are difficult to perform on strongly adherent primary human macrophages.
With regard to immunofluorescence, there is a technical limitation based on the species in which the antibodies are produced. The antibody that targets the native SNAT7 protein, which is currently being validated in our laboratory, is produced in rabbits. An anti-CAp24 antibody produced in goats can be used. It will then be necessary to co-label the cells with anti SAMHD1 and phospho-SAMHD1produced in mouse. We will try to find options to co-label the cells.
The wblot shown in panel D does not really reflect the point the authors want to make by the quantification in panels G-I. Primary data (D) suggests that SNAT7 KD reduces HIV-1 production even in the absence of SAMHD1. The quantification rather indicates that SNAT7 KD does not affect HIV-1 production in the absence of SAMHD1. This needs clarification/corroboration by orthogonal approaches.
We respectfully disagree with the reviewer.
Figure 4D shows a representative blot of the six donors analysed. As mentioned, the depletion of SNAT7 in the absence of SAMHD1 reduces the production of the viral proteins GagPr55 and CAp24 (see Fig. 4D). This is illustrated by the quantifications (Fig. 4G–I). Following treatment with Vpx, GagPr55 protein expression in SNAT7 KD macrophages is reduced by a factor of 2.6 for siRNA #1 (mean = 1.48, light grey bar) and by a factor of 1.83 for siRNA #2 (mean = 2.13, orange bar), compared to the control (mean = 3.9, pink bar) (Fig. 4G). Similarly, CAp24 protein expression was reduced by a factor of 2.2 for siRNA #1 (mean = 2.05, light grey bar) and by a factor of 1.36 for siRNA #2 (mean = 3.34, orange bar), compared to the control (mean = 4.52, pink bar) (Fig. 4H).
These differences are therefore consistent between the Western blot and the quantifications. However, they are not significantly different to those observed in cells treated with Vpx and depleted with control siRNA, suggesting that the viral restriction observed in SNAT7 KD cells is primarily due to SAMHD1.
Figure 5: show SAMHD1 and pSAMHD1 levels upon glutamine supplementation.
We thank the reviewer for this comment, we will perform the suggested experiment.
- I think the discussion is very thin, mainly summarizing the results; but fails to give broader context or critically discuss the limitations and further directions.
We thank the reviewer for this comment. The discussion will be modified further accordingly.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics. We respectfully disagree with the reviewer.
The cells used here imply greater variability than a cell line, but are also more relevant.
Indeed, the effects observed in the late stages of HIV-1 production are:
~80 % decrease in viral transcription compared to the control (Fig. 2I),
~85 % decrease in CAp24 protein expression compared to the control, as quantified by western blot (Fig. 2E), or ~90 % by ELISA measurement (Fig. 2F),
a reduction of more than 90 % in the release of infectious particles (Fig. 2G).
These results were all significant across donors, while SNAT7 depletion was always partial (Fig. 2C, between 31 to 62 % of depletion compared to the control in infected cells).
Therefore, the data were obtained from a mixture of depleted and non-depleted macrophages. This means that the results may be underestimated.
Together, our results show that SNAT7 is necessary for HIV-1 production.
However, reading the comments, we realized that our conclusions regarding reverse transcription were too strong. SNAT7 depletion does not affect viral fusion and reverse transcription. The manuscript was modified accordingly.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future.
For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes? We thank the reviewer for these questions.
To address the role of accessory viral proteins, we have already performed one experiment infecting hMDM with HIV-1 strains deleted for genes such as Nef, Vpr, Vpu and Vif, and have found no clear effect on SNAT7 protein expression compared to WT strains. As an alternative experiment, we could overexpress individual viral genes, such as Nef or Vpr, in HeLa cells and analyze their impact on SNAT7 expression by Western blot.
It is also possible that SNAT7 expression and recycling of lysosomal glutamine are modulated by the macrophage intrinsic immunity in response to HIV-1 infection.
The Thr592 motif of the SAMHD1 protein is phosphorylated by Cyclin A2/CDK1 and type 1 IFN in non-cycling cells, such as MDMs (Cribier et al., 2013). For now, the relationship between SNAT7 and SAMHD1 remains unclear. However, (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This has been added to the discussion to explain the relationship between the 3 partners.
**Referees cross-commenting** I think the comments from the other referees are reasonable and consistent with my assessment
Reviewer #1 (Significance (Required)):
Strength and limitations see above;
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
- Figure 1: SNAT7 expression was selectively enhanced upon differentiation of monocytes into macrophages but absent in CD4+ T cells. Though there is a claim of enhancement of SNAT7 expression upon HIV-1 infection of macrophages, RT-qPCR analysis shows the opposite trend (Fig 1E) and SNAT7 protein expression changes are modest. Statistical analysis in Fig. 1H needs to be revisited. The number of replicates vary for the lysates harvested at different day post infection, which might have an impact on the statistical test. To determine if SNAT7 expression enhancement is dependent on establishment of virus infection, as the authors imply, control lysates of virus infections in presence of replication inhibitors should be included.
We thank the reviewer for this comment. Indeed, there is a modest, but statistically significant increase in SNAT7 protein expression upon HIV-1 infection over time (Fig. 1G, H), without any modulation of SNAT7 gene expression (Fig. 1E). This indicates that the regulation of SNAT7 expression in this context is only at the translation level (i.e. increase of translation or stabilization of the SNAT7 protein).
As mentioned, Fig. 1H aggregates between 3 to 7 independent experiments on different donors depending on the infection time point. SNAT7 protein expression is increased already at 1 day post-infection and until 8 days. The statistical test used here, i.e. 2 way-ANOVA, compared Mock-infected and HIV-1-infected condition for each time point with the same number of donors. In this figure, the comparison is statistically different only at day 6 of the time course (7 donors). We agree that increasing the number of donors of the other time points could help to improve the statistical difference between control and infection condition.
We thank the reviewer for the suggestion mentioning the use of replication inhibitors in this experiment. We plan to use inhibitors of reverse transcription (Nevirapin) and integration (Dolutegravir).
The authors rely exclusively on western blot analysis for HIV-1 Gag expression in cell lysates as a measure of effects of SNAT7 on virus replication. Single cell analysis such as intracellular p24gag analysis by FACS should be included; this will provide a better measure of effects of SNAT7 onHIV-1 infection establishment.
We respectfully disagree with the reviewer for this question. Indeed, to evaluate the effects of SNAT7 on HIV-1 replication, we measured Gag Pr55 and Cap24 using a Western blot approach (Fig. 2B, D and E), but also assessed the quantity of Cap24 in the supernatants and lysates using an ELISA measurement, the quantity of infectious particles using TZM reporter cells, and total viral transcription or more specifically Gag Pr55 transcription using qPCR (Fig. 2F, G and I and Supp. Fig. 2G).
Regarding the quantification of CAp24 at the cell single level, please refer to comment #2 under Reviewer #1.
Knockdown of SNAT7 in MDMs was partial at best; only 30-50% decrease in expression (Fig 2C), but the effects on viral gene expression (Fig. 2I), p24 release and infectious particle production is dramatic (Fig. 2F and G). This discrepancy is not addressed. Does SNAT7 knock-down negatively impact virus particle release? Please note that the representative WB in Fig 2B does not correlate with the quantification in Fig. 2D. There are no p55gag or p24gag bands in SNAT7#1 siRNA condition (Fig. 2B)? Data could also be rearranged to follow the logical sequence of virus replication cycle (viral RNa expression followed by Gag expression, and then release).
We thank the reviewer for this comment. Our samples are indeed a mixture of SNAT7-depleted and non-depleted macrophages and RNA interference in these cells often leads to a decrease of 50 % of the protein expression.
To determine whether SNAT7 is involved in the release of particles, we quantified Cap24 in cell lysates and in the cell culture medium separately, and normalized the results to the total protein content. The absence of SNAT7 reduced the amount of Cap24 measured by ELISA in both samples to the same extent, showing that there is no storage of Cap24-positive viral particles inside the infected macrophages. These data were initially pooled in one graph (Fig. 2F), but separate graphs are now provided in new Supp. Fig. 2 E, F.
Regarding the western blot shown in Fig. 2B, please refer to comment #5 under Reviewer #1.
In the new version of the manuscript, we arranged the figures and placed the later stages of the viral cycle in Fig. 2 and the earlier stages, such as fusion, reverse transcription and transcription, in Fig. 3.
Data interpretation would be greatly improved by including infection controls (RT or integrase inhibitors) to confirm that measurements of viral RNA and Gag are indeed modulated by SNAT7 expression.
We thank the reviewer for this suggestion to include inhibitors of viral replication as controls. In our experiments, cells were Mock-infected in parallel as a negative control of viral detection. We provide the results in the new version of the manuscript to show that (i) there is no detection of viral or Gag RNA in the absence of the virus, (ii) the expression of viral genes measured in HIV-1-infected SNAT7-depleted cells is not different from Mock-infected cells, indicating almost complete inhibition of viral transcription (Fig. 3H and Supp. Fig. 3B), also confirmed at the protein level (Fig. 2B, D-F).
Figure 3: Decrease in SNAT7 expression in macrophages resulted in lower levels of early reverse transcripts. But surprisingly, LRT levels were not as affected by decreases in SNAT7 expression. The authors go on to suggest that decreases in early RT are due to loss of phospho-SAMHD1 and increases in catalytically active form of SAMHD1. Mechanistically this does not make sense: LRT should be similarly affected by increase in catalytically active SAMHD1. dNTP concentrations should be measured to determine if the rescue of RT is dependent on SAMHD1 dNTPase activity.
We thank the reviewer for this comment. LRT concentrations are very low in human macrophages and more challenging to detect than ERT concentrations. This might explain why the differences observed between the SNAT7-depleted and control conditions appear less pronounced for LRT than for ERT.
Furthermore, we cannot rule out the possibility that SNAT7 has a cumulative effect throughout the viral cycle. While reverse transcription remains statistically unaltered, and despite the reduced levels of ERT and LRT in SNAT7-depleted macrophages (Fig. 3 F, G), there is a significant impact on the transcription of viral RNAs (Fig. 2I) and Gag (Supp. Fig. 2G). This step may also be altered by the ribonuclease activity of SAMHD1 (Beloglazova et al., 2013; Ryoo et al., 2014).
Finally, with the help of Dr Baek Kim in Atlanta, we attempted to quantify dNTP concentrations in our human macrophages. Unfortunately, it was not possible to draw any conclusions, as the concentrations of dNTPs extracted from our cells were far too low.
Furthermore, it should be noted that SAMHD1 viral restriction through its phosphorylation at T592 is not correlated with its dNTPase activity (Welbourn et al., 2013; White et al., 2013), but with its ribonuclease activity (Beloglazova et al., 2013; Ryoo et al., 2014). This is supporting why SNAT7, by modulating the ribonuclease activity of SAMHD1, could have a greater effect on viral transcription than on reverse transcription.
There is lack of consistency in the data: p24 release upon SNAT7 depletion is highly variable. While there is a dramatic >90-95% decrease in p24 release (Fig. 2G), the effects are much more moderate in Fig. 4H (50-60% attenuation), even though siRNA-mediated depletion was similar across the data sets. The authors should comment on the variability in their findings.
We thank the reviewer for this comment, but believe that Figure 2E rather than Figure 2G is to be mentioned regarding the quantification of CAp24 by Western blot and to be compared with Figure 4H.
In Fig. 2E, we observed an average reduction of 85 % in CAp24 expression normalized to Clathrin HC expression across different donors for both siRNAs targeting SNAT7. For Fig. 4H, there was a 73 % reduction in CAp24 levels for siRNA #1 and a 56 % reduction for siRNA #2. In addition, it should be noted that the reduction in Gag levels is greater in Fig. 4G (between 77 % and 83 %) than in Fig. 2D (between 55 % and 72 %).
Therefore, there is some variation in the results obtained with the different donors, which could be explained by variations in Gag cleavage among donors, but this does not impact the conclusions for both figures.
SNAT7 is postulated to affect 2 steps in the virus life cycle: reverse transcription and viral transcription. But Vpx-mediated SAMHD1 degradation reversed both. Its not clear to me as to how SAMHD1 degradation impacts the role of SNAT7 in viral transcription. No explanation is provided.
We thank the reviewer for this comment. As suggested, we will perform experiments to assess the impact of Vpx-mediated SAMHD1 degradation on viral transcription.
Exogenous addition of glutamine only partially restored Gag synthesis and p24 release, which could be attributed to increased cytoplasmic levels and viral protein synthesis. What about effects on reverse transcription and viral gene expression?
We thank the reviewer for this comment. We will perform the suggested experiments to assess the impact of glutamine supplementation on viral transcription.
Reviewer #2 (Significance (Required)):
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Reviewer #3 (Evidence, reproducibility and clarity (Required)):
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn. Major Concerns: 1. The mechanistic depth is insufficient. The authors do not elucidate how glutamine regulates SAMHD1 T592 phosphorylation, whether through metabolite‑mediated control of kinases/phosphatases or via indirect effects.
We thank the reviewer for this comment. It is worth noting that (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity using drugs decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This is now further discussed in the discussion section of the manuscript.
The authors do not measure intracellular dNTP levels upon SNAT7 knockdown, which is the key functional substrate of SAMHD1. They also do not directly demonstrate that glutamine supplementation restores dNTP pools.
We thank the reviewer for this comment. Please, refer to comment #5 under Reviewer #2.
Extracellular glutamine only partially rescues viral production, implying the existence of transport‑independent functions of SNAT7 or additional pathways. This important observation is not discussed.
We thank the reviewer for this comment. The discussion has been modified accordingly.
It is suggested that the key findings be validated in immortalized THP‑1 cells differentiated into macrophage‑like cells by PMA.
We thank the reviewer for this suggestion but don’t really understand why this would strengthen our conclusions. Indeed, despite the known variability between donors and technical limitations to transduce cells, we chose human blood monocyte-derived macrophages as a relevant non-transformed model for HIV-1 infection of macrophages. They also represent to some extent the human diversity.
The Discussion section should be expanded to include the potential translational implications and limitations of the present study.
We thank the reviewer for this comment. The discussion points to some elements of potential translation and limitations of the study.
Reviewer #3 (Significance (Required)):
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience:This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
Reviewer #1 (Evidence, reproducibility and clarity (Required)):
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
- Having said so, I realize that while they give information on the statistical test used, i.e. one-way ANOVA they miss to explain the post-test used to assess significance (i.e. Bonferroni, Fishers LSD, whatsoever). Please add this information.
We thank the reviewer for this comment. The figure legends have been updated to include more details of all the statistical tests used.
- Another issue that might underestimate the effects of HIV-1 infection on SNAT7 levels and vice versa of SNAT7 KD on HIV-1 replication is the non-single cell approach employed, i.e. WBlots. I assume that HIV-1 infection rates in macrophages are not super high, usually not exceeding 20-30%. So indeed the effects the authors observe could be much higher, when checking at the single cell level. I do not know about the SNAT7 ab, but all the other reagents should work via flow cytometry and could hence improve the readout a lot.
We agree with the reviewer and indeed, in previous studies on HIV-1 infection of human macrophages performed in the lab, we observed via immunofluorescence that the proportion of infected cells ranged from 20 to 40 %. At the time of submission, we did not have the possibility to label the native SNAT7 protein by immunofluorescence, as the commercial antibody used only works for western blotting.
In the meantime, we have been validating a new antibody (Proteintech) targeting SNAT7 for immunofluorescence. If this is confirmed, we will be able to detect and quantify HIV-1 p24 by immunofluorescence in SNAT7-depleted human macrophages and control cells, thus confirming our results in single-cell analysis.
Flow cytometry analyses are difficult to perform on primary human macrophages because these cells are highly adherent and must be detached first. The process induces significant cell death and damage. This is why we would prefer to carry out these analyses using immunofluorescence and microscopy on adhered cells. This option will be undoubtedly pursued.
- Furthermore the authors never commented about a dose-response effect in terms of HIV-1 infection levels. There is a MOI dependency described for Suppl.Fig.1 C-F, unfortunately the data is missing in the manuscript.
We apologize for this omission. The figures showing the increase in SNAT7 protein expression following HIV-1 infection at MOIs ranging from 0.05 to 0.5 were added to the new version of the manuscript (Supp. Fig. 1 C-F).
- Figure1: specify circulating T lymphocytes. I would expect to see levels of SNAT7 in PHA or CD3/CD28 activated lymphocytes versus resting T cells and a time course of SNAT7 levels upon activation. I think even though SNAT7 levels in T cells might be low, they could also be increased by HIV-1 infection and it is essential that the authors test for this. If not, the result is a valid negative control. For this they should employ HIV-1 primary strains with a tropism for T cells, or at least lab-adapted HIV-1 NL4-3
We thank the reviewer for this comment. Circulating T lymphocytes isolated from the blood of healthy donors are now referred to resting lymphocytes in the new version of the manuscript, as opposed to activated T lymphocytes stimulated with IL2 and PHA-P for several days (Fig. 1 A-C).
The expression levels of SNAT7, both at the gene and protein levels, are lower in resting or IL2/PHA-P-activated T cells than in macrophages from the same donors. As suggested, we will perform a kinetic of T-cell activation upon HIV-1 infection to investigate how SNAT7 expression varies in these conditions.
- Figure 2 again single cell measurements could reveal much more pronounced effects; it is a bit counterintuitive that siRNA #2 is more efficient in SNAT7 KD but has higher levels of HIV-1 replication in terms of Gag levels. I assume when looking at the stats it is always a comparison to the Ctl treated cells (C-G), but this is not entirely clear. Unify labeling as compared to the stats in Fig.2 I (this also applies for all the other figs).
We thank the reviewer for this comment. Fig. 2B indeed shows one of the different donors analyzed. However, protein quantification across six different donors shows that SNAT7 is more depleted with siRNA #2 (Fig. 2C), and that Gag Pr55 protein levels are consequently more reduced, than with siRNA #1 (Fig. 2D).
We use GraphPad Prism software to perform statistical analysis. Depending on the test used, the software automatically plots the comparison bar and displays the p-value above it. We changed the representation of statistics as suggested.
Figure 3: It is a bit odd that they finally conclude on RT as essential step that is reduced in the absence of SNAT7 and then they fail to provide statistical significance for this (Fig.3 panels F and G). One would expect that RT is much more affected given the huge effects on HIV-1 capsid and particle production shown in Fig.2 F, G and I.
The reviewer is right in pointing that we observed a stronger effect during the later stages of the viral cycle, from transcription of viral RNAs (Fig. 2I and Supp. Fig. 2G) to the production of viral particles in the supernatant (Fig. 2D-G), than during the earlier stage of reverse transcription (Fig. 3F, G). Also, it is also possible that we might have missed the peak in ERT/LRT production, which is transient.
It should be noted that SAMHD1 exhibits both dNTPase (Goldstone et al., 2011) and nuclease (Beloglazova et al., 2013) activities. The ability of SAMHD1 to restrict the virus, through dephosphorylation at T592, is mediated by its RNase activity (Ryoo et al., 2014), and not by the dNTPase activity (Welbourn et al., 2013; White et al., 2013).This could explain why SNAT7 exhibit a stronger impact on viral transcription than on reverse transcription.
Figure 4; again single cell flow measurements of SAMHD1, pSAMHD1 and p24 /SNAT7 might help to more clearly discriminate effects that are specifically induced upon infection or happen in virally infected cells. Maybe alternatively IF?
We thank the reviewer for this suggestion. As mentioned under comment #2, flow cytometry analyses are difficult to perform on strongly adherent primary human macrophages.
With regard to immunofluorescence, there is a technical limitation based on the species in which the antibodies are produced. The antibody that targets the native SNAT7 protein, which is currently being validated in our laboratory, is produced in rabbits. An anti-CAp24 antibody produced in goats can be used. It will then be necessary to co-label the cells with anti SAMHD1 and phospho-SAMHD1produced in mouse. We will try to find options to co-label the cells.
The wblot shown in panel D does not really reflect the point the authors want to make by the quantification in panels G-I. Primary data (D) suggests that SNAT7 KD reduces HIV-1 production even in the absence of SAMHD1. The quantification rather indicates that SNAT7 KD does not affect HIV-1 production in the absence of SAMHD1. This needs clarification/corroboration by orthogonal approaches.
We respectfully disagree with the reviewer.
Figure 4D shows a representative blot of the six donors analysed. As mentioned, the depletion of SNAT7 in the absence of SAMHD1 reduces the production of the viral proteins GagPr55 and CAp24 (see Fig. 4D). This is illustrated by the quantifications (Fig. 4G–I). Following treatment with Vpx, GagPr55 protein expression in SNAT7 KD macrophages is reduced by a factor of 2.6 for siRNA #1 (mean = 1.48, light grey bar) and by a factor of 1.83 for siRNA #2 (mean = 2.13, orange bar), compared to the control (mean = 3.9, pink bar) (Fig. 4G). Similarly, CAp24 protein expression was reduced by a factor of 2.2 for siRNA #1 (mean = 2.05, light grey bar) and by a factor of 1.36 for siRNA #2 (mean = 3.34, orange bar), compared to the control (mean = 4.52, pink bar) (Fig. 4H).
These differences are therefore consistent between the Western blot and the quantifications. However, they are not significantly different to those observed in cells treated with Vpx and depleted with control siRNA, suggesting that the viral restriction observed in SNAT7 KD cells is primarily due to SAMHD1.
Figure 5: show SAMHD1 and pSAMHD1 levels upon glutamine supplementation.
We thank the reviewer for this comment, we will perform the suggested experiment.
- I think the discussion is very thin, mainly summarizing the results; but fails to give broader context or critically discuss the limitations and further directions.
We thank the reviewer for this comment. The discussion will be modified further accordingly.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics. We respectfully disagree with the reviewer.
The cells used here imply greater variability than a cell line, but are also more relevant.
Indeed, the effects observed in the late stages of HIV-1 production are:
~80 % decrease in viral transcription compared to the control (Fig. 2I),
~85 % decrease in CAp24 protein expression compared to the control, as quantified by western blot (Fig. 2E), or ~90 % by ELISA measurement (Fig. 2F),
a reduction of more than 90 % in the release of infectious particles (Fig. 2G).
These results were all significant across donors, while SNAT7 depletion was always partial (Fig. 2C, between 31 to 62 % of depletion compared to the control in infected cells).
Therefore, the data were obtained from a mixture of depleted and non-depleted macrophages. This means that the results may be underestimated.
Together, our results show that SNAT7 is necessary for HIV-1 production.
However, reading the comments, we realized that our conclusions regarding reverse transcription were too strong. SNAT7 depletion does not affect viral fusion and reverse transcription. The manuscript was modified accordingly.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future.
For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes? We thank the reviewer for these questions.
To address the role of accessory viral proteins, we have already performed one experiment infecting hMDM with HIV-1 strains deleted for genes such as Nef, Vpr, Vpu and Vif, and have found no clear effect on SNAT7 protein expression compared to WT strains. As an alternative experiment, we could overexpress individual viral genes, such as Nef or Vpr, in HeLa cells and analyze their impact on SNAT7 expression by Western blot.
It is also possible that SNAT7 expression and recycling of lysosomal glutamine are modulated by the macrophage intrinsic immunity in response to HIV-1 infection.
The Thr592 motif of the SAMHD1 protein is phosphorylated by Cyclin A2/CDK1 and type 1 IFN in non-cycling cells, such as MDMs (Cribier et al., 2013). For now, the relationship between SNAT7 and SAMHD1 remains unclear. However, (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This has been added to the discussion to explain the relationship between the 3 partners.
**Referees cross-commenting** I think the comments from the other referees are reasonable and consistent with my assessment
Reviewer #1 (Significance (Required)):
Strength and limitations see above;
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
- Figure 1: SNAT7 expression was selectively enhanced upon differentiation of monocytes into macrophages but absent in CD4+ T cells. Though there is a claim of enhancement of SNAT7 expression upon HIV-1 infection of macrophages, RT-qPCR analysis shows the opposite trend (Fig 1E) and SNAT7 protein expression changes are modest. Statistical analysis in Fig. 1H needs to be revisited. The number of replicates vary for the lysates harvested at different day post infection, which might have an impact on the statistical test. To determine if SNAT7 expression enhancement is dependent on establishment of virus infection, as the authors imply, control lysates of virus infections in presence of replication inhibitors should be included.
We thank the reviewer for this comment. Indeed, there is a modest, but statistically significant increase in SNAT7 protein expression upon HIV-1 infection over time (Fig. 1G, H), without any modulation of SNAT7 gene expression (Fig. 1E). This indicates that the regulation of SNAT7 expression in this context is only at the translation level (i.e. increase of translation or stabilization of the SNAT7 protein).
As mentioned, Fig. 1H aggregates between 3 to 7 independent experiments on different donors depending on the infection time point. SNAT7 protein expression is increased already at 1 day post-infection and until 8 days. The statistical test used here, i.e. 2 way-ANOVA, compared Mock-infected and HIV-1-infected condition for each time point with the same number of donors. In this figure, the comparison is statistically different only at day 6 of the time course (7 donors). We agree that increasing the number of donors of the other time points could help to improve the statistical difference between control and infection condition.
We thank the reviewer for the suggestion mentioning the use of replication inhibitors in this experiment. We plan to use inhibitors of reverse transcription (Nevirapin) and integration (Dolutegravir).
The authors rely exclusively on western blot analysis for HIV-1 Gag expression in cell lysates as a measure of effects of SNAT7 on virus replication. Single cell analysis such as intracellular p24gag analysis by FACS should be included; this will provide a better measure of effects of SNAT7 onHIV-1 infection establishment.
We respectfully disagree with the reviewer for this question. Indeed, to evaluate the effects of SNAT7 on HIV-1 replication, we measured Gag Pr55 and Cap24 using a Western blot approach (Fig. 2B, D and E), but also assessed the quantity of Cap24 in the supernatants and lysates using an ELISA measurement, the quantity of infectious particles using TZM reporter cells, and total viral transcription or more specifically Gag Pr55 transcription using qPCR (Fig. 2F, G and I and Supp. Fig. 2G).
Regarding the quantification of CAp24 at the cell single level, please refer to comment #2 under Reviewer #1.
Knockdown of SNAT7 in MDMs was partial at best; only 30-50% decrease in expression (Fig 2C), but the effects on viral gene expression (Fig. 2I), p24 release and infectious particle production is dramatic (Fig. 2F and G). This discrepancy is not addressed. Does SNAT7 knock-down negatively impact virus particle release? Please note that the representative WB in Fig 2B does not correlate with the quantification in Fig. 2D. There are no p55gag or p24gag bands in SNAT7#1 siRNA condition (Fig. 2B)? Data could also be rearranged to follow the logical sequence of virus replication cycle (viral RNa expression followed by Gag expression, and then release).
We thank the reviewer for this comment. Our samples are indeed a mixture of SNAT7-depleted and non-depleted macrophages and RNA interference in these cells often leads to a decrease of 50 % of the protein expression.
To determine whether SNAT7 is involved in the release of particles, we quantified Cap24 in cell lysates and in the cell culture medium separately, and normalized the results to the total protein content. The absence of SNAT7 reduced the amount of Cap24 measured by ELISA in both samples to the same extent, showing that there is no storage of Cap24-positive viral particles inside the infected macrophages. These data were initially pooled in one graph (Fig. 2F), but separate graphs are now provided in new Supp. Fig. 2 E, F.
Regarding the western blot shown in Fig. 2B, please refer to comment #5 under Reviewer #1.
In the new version of the manuscript, we arranged the figures and placed the later stages of the viral cycle in Fig. 2 and the earlier stages, such as fusion, reverse transcription and transcription, in Fig. 3.
Data interpretation would be greatly improved by including infection controls (RT or integrase inhibitors) to confirm that measurements of viral RNA and Gag are indeed modulated by SNAT7 expression.
We thank the reviewer for this suggestion to include inhibitors of viral replication as controls. In our experiments, cells were Mock-infected in parallel as a negative control of viral detection. We provide the results in the new version of the manuscript to show that (i) there is no detection of viral or Gag RNA in the absence of the virus, (ii) the expression of viral genes measured in HIV-1-infected SNAT7-depleted cells is not different from Mock-infected cells, indicating almost complete inhibition of viral transcription (Fig. 3H and Supp. Fig. 3B), also confirmed at the protein level (Fig. 2B, D-F).
Figure 3: Decrease in SNAT7 expression in macrophages resulted in lower levels of early reverse transcripts. But surprisingly, LRT levels were not as affected by decreases in SNAT7 expression. The authors go on to suggest that decreases in early RT are due to loss of phospho-SAMHD1 and increases in catalytically active form of SAMHD1. Mechanistically this does not make sense: LRT should be similarly affected by increase in catalytically active SAMHD1. dNTP concentrations should be measured to determine if the rescue of RT is dependent on SAMHD1 dNTPase activity.
We thank the reviewer for this comment. LRT concentrations are very low in human macrophages and more challenging to detect than ERT concentrations. This might explain why the differences observed between the SNAT7-depleted and control conditions appear less pronounced for LRT than for ERT.
Furthermore, we cannot rule out the possibility that SNAT7 has a cumulative effect throughout the viral cycle. While reverse transcription remains statistically unaltered, and despite the reduced levels of ERT and LRT in SNAT7-depleted macrophages (Fig. 3 F, G), there is a significant impact on the transcription of viral RNAs (Fig. 2I) and Gag (Supp. Fig. 2G). This step may also be altered by the ribonuclease activity of SAMHD1 (Beloglazova et al., 2013; Ryoo et al., 2014).
Finally, with the help of Dr Baek Kim in Atlanta, we attempted to quantify dNTP concentrations in our human macrophages. Unfortunately, it was not possible to draw any conclusions, as the concentrations of dNTPs extracted from our cells were far too low.
Furthermore, it should be noted that SAMHD1 viral restriction through its phosphorylation at T592 is not correlated with its dNTPase activity (Welbourn et al., 2013; White et al., 2013), but with its ribonuclease activity (Beloglazova et al., 2013; Ryoo et al., 2014). This is supporting why SNAT7, by modulating the ribonuclease activity of SAMHD1, could have a greater effect on viral transcription than on reverse transcription.
There is lack of consistency in the data: p24 release upon SNAT7 depletion is highly variable. While there is a dramatic >90-95% decrease in p24 release (Fig. 2G), the effects are much more moderate in Fig. 4H (50-60% attenuation), even though siRNA-mediated depletion was similar across the data sets. The authors should comment on the variability in their findings.
We thank the reviewer for this comment, but believe that Figure 2E rather than Figure 2G is to be mentioned regarding the quantification of CAp24 by Western blot and to be compared with Figure 4H.
In Fig. 2E, we observed an average reduction of 85 % in CAp24 expression normalized to Clathrin HC expression across different donors for both siRNAs targeting SNAT7. For Fig. 4H, there was a 73 % reduction in CAp24 levels for siRNA #1 and a 56 % reduction for siRNA #2. In addition, it should be noted that the reduction in Gag levels is greater in Fig. 4G (between 77 % and 83 %) than in Fig. 2D (between 55 % and 72 %).
Therefore, there is some variation in the results obtained with the different donors, which could be explained by variations in Gag cleavage among donors, but this does not impact the conclusions for both figures.
SNAT7 is postulated to affect 2 steps in the virus life cycle: reverse transcription and viral transcription. But Vpx-mediated SAMHD1 degradation reversed both. Its not clear to me as to how SAMHD1 degradation impacts the role of SNAT7 in viral transcription. No explanation is provided.
We thank the reviewer for this comment. As suggested, we will perform experiments to assess the impact of Vpx-mediated SAMHD1 degradation on viral transcription.
Exogenous addition of glutamine only partially restored Gag synthesis and p24 release, which could be attributed to increased cytoplasmic levels and viral protein synthesis. What about effects on reverse transcription and viral gene expression?
We thank the reviewer for this comment. We will perform the suggested experiments to assess the impact of glutamine supplementation on viral transcription.
Reviewer #2 (Significance (Required)):
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Reviewer #3 (Evidence, reproducibility and clarity (Required)):
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn. Major Concerns: 1. The mechanistic depth is insufficient. The authors do not elucidate how glutamine regulates SAMHD1 T592 phosphorylation, whether through metabolite‑mediated control of kinases/phosphatases or via indirect effects.
We thank the reviewer for this comment. It is worth noting that (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity using drugs decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This is now further discussed in the discussion section of the manuscript.
The authors do not measure intracellular dNTP levels upon SNAT7 knockdown, which is the key functional substrate of SAMHD1. They also do not directly demonstrate that glutamine supplementation restores dNTP pools.
We thank the reviewer for this comment. Please, refer to comment #5 under Reviewer #2.
Extracellular glutamine only partially rescues viral production, implying the existence of transport‑independent functions of SNAT7 or additional pathways. This important observation is not discussed.
We thank the reviewer for this comment. The discussion has been modified accordingly.
It is suggested that the key findings be validated in immortalized THP‑1 cells differentiated into macrophage‑like cells by PMA.
We thank the reviewer for this suggestion but don’t really understand why this would strengthen our conclusions. Indeed, despite the known variability between donors and technical limitations to transduce cells, we chose human blood monocyte-derived macrophages as a relevant non-transformed model for HIV-1 infection of macrophages. They also represent to some extent the human diversity.
The Discussion section should be expanded to include the potential translational implications and limitations of the present study.
We thank the reviewer for this comment. The discussion points to some elements of potential translation and limitations of the study.
Reviewer #3 (Significance (Required)):
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience:This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
2.15.1.0 Reviewer #1 (Evidence, reproducibility and clarity (Required)):
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
- Having said so, I realize that while they give information on the statistical test used, i.e. one-way ANOVA they miss to explain the post-test used to assess significance (i.e. Bonferroni, Fishers LSD, whatsoever). Please add this information.
We thank the reviewer for this comment. The figure legends have been updated to include more details of all the statistical tests used.
- Another issue that might underestimate the effects of HIV-1 infection on SNAT7 levels and vice versa of SNAT7 KD on HIV-1 replication is the non-single cell approach employed, i.e. WBlots. I assume that HIV-1 infection rates in macrophages are not super high, usually not exceeding 20-30%. So indeed the effects the authors observe could be much higher, when checking at the single cell level. I do not know about the SNAT7 ab, but all the other reagents should work via flow cytometry and could hence improve the readout a lot.
We agree with the reviewer and indeed, in previous studies on HIV-1 infection of human macrophages performed in the lab, we observed via immunofluorescence that the proportion of infected cells ranged from 20 to 40 %. At the time of submission, we did not have the possibility to label the native SNAT7 protein by immunofluorescence, as the commercial antibody used only works for western blotting.
In the meantime, we have been validating a new antibody (Proteintech) targeting SNAT7 for immunofluorescence. If this is confirmed, we will be able to detect and quantify HIV-1 p24 by immunofluorescence in SNAT7-depleted human macrophages and control cells, thus confirming our results in single-cell analysis.
Flow cytometry analyses are difficult to perform on primary human macrophages because these cells are highly adherent and must be detached first. The process induces significant cell death and damage. This is why we would prefer to carry out these analyses using immunofluorescence and microscopy on adhered cells. This option will be undoubtedly pursued.
- Furthermore the authors never commented about a dose-response effect in terms of HIV-1 infection levels. There is a MOI dependency described for Suppl.Fig.1 C-F, unfortunately the data is missing in the manuscript.
We apologize for this omission. The figures showing the increase in SNAT7 protein expression following HIV-1 infection at MOIs ranging from 0.05 to 0.5 were added to the new version of the manuscript (Supp. Fig. 1 C-F).
- Figure1: specify circulating T lymphocytes. I would expect to see levels of SNAT7 in PHA or CD3/CD28 activated lymphocytes versus resting T cells and a time course of SNAT7 levels upon activation. I think even though SNAT7 levels in T cells might be low, they could also be increased by HIV-1 infection and it is essential that the authors test for this. If not, the result is a valid negative control. For this they should employ HIV-1 primary strains with a tropism for T cells, or at least lab-adapted HIV-1 NL4-3
We thank the reviewer for this comment. Circulating T lymphocytes isolated from the blood of healthy donors are now referred to resting lymphocytes in the new version of the manuscript, as opposed to activated T lymphocytes stimulated with IL2 and PHA-P for several days (Fig. 1 A-C).
The expression levels of SNAT7, both at the gene and protein levels, are lower in resting or IL2/PHA-P-activated T cells than in macrophages from the same donors. As suggested, we will perform a kinetic of T-cell activation upon HIV-1 infection to investigate how SNAT7 expression varies in these conditions.
- Figure 2 again single cell measurements could reveal much more pronounced effects; it is a bit counterintuitive that siRNA #2 is more efficient in SNAT7 KD but has higher levels of HIV-1 replication in terms of Gag levels. I assume when looking at the stats it is always a comparison to the Ctl treated cells (C-G), but this is not entirely clear. Unify labeling as compared to the stats in Fig.2 I (this also applies for all the other figs).
We thank the reviewer for this comment. Fig. 2B indeed shows one of the different donors analyzed. However, protein quantification across six different donors shows that SNAT7 is more depleted with siRNA #2 (Fig. 2C), and that Gag Pr55 protein levels are consequently more reduced, than with siRNA #1 (Fig. 2D).
We use GraphPad Prism software to perform statistical analysis. Depending on the test used, the software automatically plots the comparison bar and displays the p-value above it. We changed the representation of statistics as suggested.
Figure 3: It is a bit odd that they finally conclude on RT as essential step that is reduced in the absence of SNAT7 and then they fail to provide statistical significance for this (Fig.3 panels F and G). One would expect that RT is much more affected given the huge effects on HIV-1 capsid and particle production shown in Fig.2 F, G and I.
The reviewer is right in pointing that we observed a stronger effect during the later stages of the viral cycle, from transcription of viral RNAs (Fig. 2I and Supp. Fig. 2G) to the production of viral particles in the supernatant (Fig. 2D-G), than during the earlier stage of reverse transcription (Fig. 3F, G). Also, it is also possible that we might have missed the peak in ERT/LRT production, which is transient.
It should be noted that SAMHD1 exhibits both dNTPase (Goldstone et al., 2011) and nuclease (Beloglazova et al., 2013) activities. The ability of SAMHD1 to restrict the virus, through dephosphorylation at T592, is mediated by its RNase activity (Ryoo et al., 2014), and not by the dNTPase activity (Welbourn et al., 2013; White et al., 2013).This could explain why SNAT7 exhibit a stronger impact on viral transcription than on reverse transcription.
Figure 4; again single cell flow measurements of SAMHD1, pSAMHD1 and p24 /SNAT7 might help to more clearly discriminate effects that are specifically induced upon infection or happen in virally infected cells. Maybe alternatively IF?
We thank the reviewer for this suggestion. As mentioned under comment #2, flow cytometry analyses are difficult to perform on strongly adherent primary human macrophages.
With regard to immunofluorescence, there is a technical limitation based on the species in which the antibodies are produced. The antibody that targets the native SNAT7 protein, which is currently being validated in our laboratory, is produced in rabbits. An anti-CAp24 antibody produced in goats can be used. It will then be necessary to co-label the cells with anti SAMHD1 and phospho-SAMHD1produced in mouse. We will try to find options to co-label the cells.
The wblot shown in panel D does not really reflect the point the authors want to make by the quantification in panels G-I. Primary data (D) suggests that SNAT7 KD reduces HIV-1 production even in the absence of SAMHD1. The quantification rather indicates that SNAT7 KD does not affect HIV-1 production in the absence of SAMHD1. This needs clarification/corroboration by orthogonal approaches.
We respectfully disagree with the reviewer.
Figure 4D shows a representative blot of the six donors analysed. As mentioned, the depletion of SNAT7 in the absence of SAMHD1 reduces the production of the viral proteins GagPr55 and CAp24 (see Fig. 4D). This is illustrated by the quantifications (Fig. 4G–I). Following treatment with Vpx, GagPr55 protein expression in SNAT7 KD macrophages is reduced by a factor of 2.6 for siRNA #1 (mean = 1.48, light grey bar) and by a factor of 1.83 for siRNA #2 (mean = 2.13, orange bar), compared to the control (mean = 3.9, pink bar) (Fig. 4G). Similarly, CAp24 protein expression was reduced by a factor of 2.2 for siRNA #1 (mean = 2.05, light grey bar) and by a factor of 1.36 for siRNA #2 (mean = 3.34, orange bar), compared to the control (mean = 4.52, pink bar) (Fig. 4H).
These differences are therefore consistent between the Western blot and the quantifications. However, they are not significantly different to those observed in cells treated with Vpx and depleted with control siRNA, suggesting that the viral restriction observed in SNAT7 KD cells is primarily due to SAMHD1.
- Figure 5: show SAMHD1 and pSAMHD1 levels upon glutamine supplementation.
We thank the reviewer for this comment, we will perform the suggested experiment.
- I think the discussion is very thin, mainly summarizing the results; but fails to give broader context or critically discuss the limitations and further directions.
We thank the reviewer for this comment. The discussion will be modified further accordingly.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics. We respectfully disagree with the reviewer.
The cells used here imply greater variability than a cell line, but are also more relevant.
Indeed, the effects observed in the late stages of HIV-1 production are:
~80 % decrease in viral transcription compared to the control (Fig. 2I),
~85 % decrease in CAp24 protein expression compared to the control, as quantified by western blot (Fig. 2E), or ~90 % by ELISA measurement (Fig. 2F),
a reduction of more than 90 % in the release of infectious particles (Fig. 2G).
These results were all significant across donors, while SNAT7 depletion was always partial (Fig. 2C, between 31 to 62 % of depletion compared to the control in infected cells).
Therefore, the data were obtained from a mixture of depleted and non-depleted macrophages. This means that the results may be underestimated.
Together, our results show that SNAT7 is necessary for HIV-1 production.
However, reading the comments, we realized that our conclusions regarding reverse transcription were too strong. SNAT7 depletion does not affect viral fusion and reverse transcription. The manuscript was modified accordingly.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future.
For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes? We thank the reviewer for these questions.
To address the role of accessory viral proteins, we have already performed one experiment infecting hMDM with HIV-1 strains deleted for genes such as Nef, Vpr, Vpu and Vif, and have found no clear effect on SNAT7 protein expression compared to WT strains. As an alternative experiment, we could overexpress individual viral genes, such as Nef or Vpr, in HeLa cells and analyze their impact on SNAT7 expression by Western blot.
It is also possible that SNAT7 expression and recycling of lysosomal glutamine are modulated by the macrophage intrinsic immunity in response to HIV-1 infection.
The Thr592 motif of the SAMHD1 protein is phosphorylated by Cyclin A2/CDK1 and type 1 IFN in non-cycling cells, such as MDMs (Cribier et al., 2013). For now, the relationship between SNAT7 and SAMHD1 remains unclear. However, (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This has been added to the discussion to explain the relationship between the 3 partners.
**Referees cross-commenting** I think the comments from the other referees are reasonable and consistent with my assessment
Reviewer #1 (Significance (Required)):
Strength and limitations see above;
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
- Figure 1: SNAT7 expression was selectively enhanced upon differentiation of monocytes into macrophages but absent in CD4+ T cells. Though there is a claim of enhancement of SNAT7 expression upon HIV-1 infection of macrophages, RT-qPCR analysis shows the opposite trend (Fig 1E) and SNAT7 protein expression changes are modest. Statistical analysis in Fig. 1H needs to be revisited. The number of replicates vary for the lysates harvested at different day post infection, which might have an impact on the statistical test. To determine if SNAT7 expression enhancement is dependent on establishment of virus infection, as the authors imply, control lysates of virus infections in presence of replication inhibitors should be included.
We thank the reviewer for this comment. Indeed, there is a modest, but statistically significant increase in SNAT7 protein expression upon HIV-1 infection over time (Fig. 1G, H), without any modulation of SNAT7 gene expression (Fig. 1E). This indicates that the regulation of SNAT7 expression in this context is only at the translation level (i.e. increase of translation or stabilization of the SNAT7 protein).
As mentioned, Fig. 1H aggregates between 3 to 7 independent experiments on different donors depending on the infection time point. SNAT7 protein expression is increased already at 1 day post-infection and until 8 days. The statistical test used here, i.e. 2 way-ANOVA, compared Mock-infected and HIV-1-infected condition for each time point with the same number of donors. In this figure, the comparison is statistically different only at day 6 of the time course (7 donors). We agree that increasing the number of donors of the other time points could help to improve the statistical difference between control and infection condition.
We thank the reviewer for the suggestion mentioning the use of replication inhibitors in this experiment. We plan to use inhibitors of reverse transcription (Nevirapin) and integration (Dolutegravir).
The authors rely exclusively on western blot analysis for HIV-1 Gag expression in cell lysates as a measure of effects of SNAT7 on virus replication. Single cell analysis such as intracellular p24gag analysis by FACS should be included; this will provide a better measure of effects of SNAT7 onHIV-1 infection establishment.
We respectfully disagree with the reviewer for this question. Indeed, to evaluate the effects of SNAT7 on HIV-1 replication, we measured Gag Pr55 and Cap24 using a Western blot approach (Fig. 2B, D and E), but also assessed the quantity of Cap24 in the supernatants and lysates using an ELISA measurement, the quantity of infectious particles using TZM reporter cells, and total viral transcription or more specifically Gag Pr55 transcription using qPCR (Fig. 2F, G and I and Supp. Fig. 2G).
Regarding the quantification of CAp24 at the cell single level, please refer to comment #2 under Reviewer #1.
Knockdown of SNAT7 in MDMs was partial at best; only 30-50% decrease in expression (Fig 2C), but the effects on viral gene expression (Fig. 2I), p24 release and infectious particle production is dramatic (Fig. 2F and G). This discrepancy is not addressed. Does SNAT7 knock-down negatively impact virus particle release? Please note that the representative WB in Fig 2B does not correlate with the quantification in Fig. 2D. There are no p55gag or p24gag bands in SNAT7#1 siRNA condition (Fig. 2B)? Data could also be rearranged to follow the logical sequence of virus replication cycle (viral RNa expression followed by Gag expression, and then release).
We thank the reviewer for this comment. Our samples are indeed a mixture of SNAT7-depleted and non-depleted macrophages and RNA interference in these cells often leads to a decrease of 50 % of the protein expression.
To determine whether SNAT7 is involved in the release of particles, we quantified Cap24 in cell lysates and in the cell culture medium separately, and normalized the results to the total protein content. The absence of SNAT7 reduced the amount of Cap24 measured by ELISA in both samples to the same extent, showing that there is no storage of Cap24-positive viral particles inside the infected macrophages. These data were initially pooled in one graph (Fig. 2F), but separate graphs are now provided in new Supp. Fig. 2 E, F.
Regarding the western blot shown in Fig. 2B, please refer to comment #5 under Reviewer #1.
In the new version of the manuscript, we arranged the figures and placed the later stages of the viral cycle in Fig. 2 and the earlier stages, such as fusion, reverse transcription and transcription, in Fig. 3.
Data interpretation would be greatly improved by including infection controls (RT or integrase inhibitors) to confirm that measurements of viral RNA and Gag are indeed modulated by SNAT7 expression.
We thank the reviewer for this suggestion to include inhibitors of viral replication as controls. In our experiments, cells were Mock-infected in parallel as a negative control of viral detection. We provide the results in the new version of the manuscript to show that (i) there is no detection of viral or Gag RNA in the absence of the virus, (ii) the expression of viral genes measured in HIV-1-infected SNAT7-depleted cells is not different from Mock-infected cells, indicating almost complete inhibition of viral transcription (Fig. 3H and Supp. Fig. 3B), also confirmed at the protein level (Fig. 2B, D-F).
Figure 3: Decrease in SNAT7 expression in macrophages resulted in lower levels of early reverse transcripts. But surprisingly, LRT levels were not as affected by decreases in SNAT7 expression. The authors go on to suggest that decreases in early RT are due to loss of phospho-SAMHD1 and increases in catalytically active form of SAMHD1. Mechanistically this does not make sense: LRT should be similarly affected by increase in catalytically active SAMHD1. dNTP concentrations should be measured to determine if the rescue of RT is dependent on SAMHD1 dNTPase activity.
We thank the reviewer for this comment. LRT concentrations are very low in human macrophages and more challenging to detect than ERT concentrations. This might explain why the differences observed between the SNAT7-depleted and control conditions appear less pronounced for LRT than for ERT.
Furthermore, we cannot rule out the possibility that SNAT7 has a cumulative effect throughout the viral cycle. While reverse transcription remains statistically unaltered, and despite the reduced levels of ERT and LRT in SNAT7-depleted macrophages (Fig. 3 F, G), there is a significant impact on the transcription of viral RNAs (Fig. 2I) and Gag (Supp. Fig. 2G). This step may also be altered by the ribonuclease activity of SAMHD1 (Beloglazova et al., 2013; Ryoo et al., 2014).
Finally, with the help of Dr Baek Kim in Atlanta, we attempted to quantify dNTP concentrations in our human macrophages. Unfortunately, it was not possible to draw any conclusions, as the concentrations of dNTPs extracted from our cells were far too low.
Furthermore, it should be noted that SAMHD1 viral restriction through its phosphorylation at T592 is not correlated with its dNTPase activity (Welbourn et al., 2013; White et al., 2013), but with its ribonuclease activity (Beloglazova et al., 2013; Ryoo et al., 2014). This is supporting why SNAT7, by modulating the ribonuclease activity of SAMHD1, could have a greater effect on viral transcription than on reverse transcription.
There is lack of consistency in the data: p24 release upon SNAT7 depletion is highly variable. While there is a dramatic >90-95% decrease in p24 release (Fig. 2G), the effects are much more moderate in Fig. 4H (50-60% attenuation), even though siRNA-mediated depletion was similar across the data sets. The authors should comment on the variability in their findings.
We thank the reviewer for this comment, but believe that Figure 2E rather than Figure 2G is to be mentioned regarding the quantification of CAp24 by Western blot and to be compared with Figure 4H.
In Fig. 2E, we observed an average reduction of 85 % in CAp24 expression normalized to Clathrin HC expression across different donors for both siRNAs targeting SNAT7. For Fig. 4H, there was a 73 % reduction in CAp24 levels for siRNA #1 and a 56 % reduction for siRNA #2. In addition, it should be noted that the reduction in Gag levels is greater in Fig. 4G (between 77 % and 83 %) than in Fig. 2D (between 55 % and 72 %).
Therefore, there is some variation in the results obtained with the different donors, which could be explained by variations in Gag cleavage among donors, but this does not impact the conclusions for both figures.
SNAT7 is postulated to affect 2 steps in the virus life cycle: reverse transcription and viral transcription. But Vpx-mediated SAMHD1 degradation reversed both. Its not clear to me as to how SAMHD1 degradation impacts the role of SNAT7 in viral transcription. No explanation is provided.
We thank the reviewer for this comment. As suggested, we will perform experiments to assess the impact of Vpx-mediated SAMHD1 degradation on viral transcription.
Exogenous addition of glutamine only partially restored Gag synthesis and p24 release, which could be attributed to increased cytoplasmic levels and viral protein synthesis. What about effects on reverse transcription and viral gene expression?
We thank the reviewer for this comment. We will perform the suggested experiments to assess the impact of glutamine supplementation on viral transcription.
Reviewer #2 (Significance (Required)):
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Reviewer #3 (Evidence, reproducibility and clarity (Required)):
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn. Major Concerns: 1. The mechanistic depth is insufficient. The authors do not elucidate how glutamine regulates SAMHD1 T592 phosphorylation, whether through metabolite‑mediated control of kinases/phosphatases or via indirect effects.
We thank the reviewer for this comment. It is worth noting that (Meng et al., 2022) demonstrated that SNAT7 positively regulates mTORC1 activity at the lysosomal membrane through release of lysosomal glutamine, and (Dias et al., 2024) showed that inhibiting mTORC1 activity using drugs decreases SAMHD1 Thr592 phosphorylation in hMDM. Therefore, we could speculate that the absence of SNAT7 down-regulates mTORC1 activity, which then leads to decreased SAMHD1 phosphorylation. This is now further discussed in the discussion section of the manuscript.
The authors do not measure intracellular dNTP levels upon SNAT7 knockdown, which is the key functional substrate of SAMHD1. They also do not directly demonstrate that glutamine supplementation restores dNTP pools.
We thank the reviewer for this comment. Please, refer to comment #5 under Reviewer #2.
Extracellular glutamine only partially rescues viral production, implying the existence of transport‑independent functions of SNAT7 or additional pathways. This important observation is not discussed.
We thank the reviewer for this comment. The discussion has been modified accordingly.
It is suggested that the key findings be validated in immortalized THP‑1 cells differentiated into macrophage‑like cells by PMA.
We thank the reviewer for this suggestion but don’t really understand why this would strengthen our conclusions. Indeed, despite the known variability between donors and technical limitations to transduce cells, we chose human blood monocyte-derived macrophages as a relevant non-transformed model for HIV-1 infection of macrophages. They also represent to some extent the human diversity.
The Discussion section should be expanded to include the potential translational implications and limitations of the present study.
We thank the reviewer for this comment. The discussion points to some elements of potential translation and limitations of the study.
Reviewer #3 (Significance (Required)):
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience:This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
2.15.1.0
Note: This preprint has been reviewed by subject experts for Review Commons. Content has not been altered except for formatting.
Learn more at Review Commons
This study investigates the role of the lysosomal glutamine transporter SLC38A7/SNAT7 in HIV‑1 replication in primary human macrophages. The authors demonstrate that SNAT7 is highly expressed in macrophages and upregulated upon HIV‑1 infection. They show that SNAT7 depletion inhibits HIV‑1 production at the reverse transcription step without affecting viral fusion or global cellular translation/transcription. Mechanistically, SNAT7 knockdown reduces the inhibitory phosphorylation of SAMHD1 at T592, and degradation of SAMHD1 by Vpx fully rescues viral replication. Extracellular glutamine supplementation partially restores HIV‑1 production in SNAT7‑deficient cells. Overall, the authors report interesting observations; however, the mechanistic investigation remains preliminary, raising concerns about whether the data fully support all the conclusions drawn.
Major Concerns
General assessment: This study identifies the lysosomal glutamine transporter SLC38A7/SNAT7 as a novel host dependency factor for HIV‑1 replication in primary human macrophages. The major strengths include the use of physiologically relevant primary macrophage models, a well-organized experimental pipeline from expression profiling to functional validation, and the establishment of a link between SNAT7, glutamine metabolism, and the HIV restriction factor SAMHD1.
Advance: It extends current understanding of HIV‑1 host dependency factors and immunometabolism by revealing a compartment‑specific metabolic pathway that supports viral reverse transcription.
Audience: This work will primarily interest specialized researchers in HIV‑1 biology, host-virus interactions, restriction factors, and antiviral innate immunity.
Note: This preprint has been reviewed by subject experts for Review Commons. Content has not been altered except for formatting.
Learn more at Review Commons
In this report, Herit and colleagues describe the role of a HIV-1 dependency factor that promotes virus replication in macrophages. The authors suggest that the lysosomal membrane-associated SNAT7 glutamine transporter is a HIV dependency factor, that promotes virus replication by enhancing reverse transcription and Gag synthesis. The authors use transient knock-down approaches in primary macrophages to identify that SNAT7 depletion does not impact viral entry but inhibits early reverse transcription which was reversed by exogenous glutamine addition. While reverse transcription enhancement was likely due to selective increase in phosho-SAMHD1 expression, mechanisms by which SNAT7 enhanced viral gene expression were not clearly defined. These are well-controlled studies that pinpoint the role of SNAT7 in the early steps of viral life cycle and highlight the intricate interplay between macrophage metabolism and HIV-1 replication. While the question that is addressed is important, and the hypothesis overall sound, the data presented needs to be strengthened to support the conclusions. There are numerous weaknesses in data interpretation as well.
This is a novel finding, as there are limited number of studies on amino acid transporters and HIV-1 replication enhancement in macrophages. Most of the previous work has focused on CD4 T cells. These studies on SNAT7 and HIV-1 infection establishment in macrophages might better inform the influences of macrophage metabolism on HIV-1 persistence and inflammatory responses.
Note: This preprint has been reviewed by subject experts for Review Commons. Content has not been altered except for formatting.
Learn more at Review Commons
This study from the Niedergang lab establishes SNAT7 as a host-dependency factor in human macrophages that supports HIV-1 replication. They show a modest increase in SNAT7 levels HIV-1 infected macrophages and suggest that SNAT7 levels are transiently increased. Employing siRNA against SNAT7 they show reduction in HIV-1 protein levels and viral RNAs and claim that there is a block of reverse transcription in SNAT7 KD cells. Focusing on a known HIV-1 restriction factor in macrophages, SAMHD1, they interconnect the SNAT7 depletion with a reduction in phosphorylated, i.e. catalytical inactive SAMHD1 arguing that SNAT7 regulates the phosphorylation and thereby antiviral activity of SAMHD1. Since SNAT7 is a glutamine transporter that provides this AA from lysosomes, they lastly supplement glutamine and this somehow rescues the reduction of HIV-1 production in SNAT7 KD cells.
Major comments:
The strength of this manuscript is the clear focus on primary human macrophages that are HIV-1 infected and the interconnection of HIV-1 replication to the SNAT7 siRNA KD experiments in combination with SAMHD1 depletion and lastly glutamine supplementation. This establishes a stringent and coherent story line. The effects reported are modest; high variability is not a problem since using primary hMDM this is expected and can be addressed by testing several donors and applying stringent statistics.
Looking at the data as a whole, I think the results support a modest functional importance of SNAT7 for HIV-1 production in macrophages. I acknowledge that the experiments in primary macrophages are prone to high variability in different donors and the authors transparently depicted their data. However clearly, I would advice the authors to tune down the extend in which they claim SNAT7-dependency given this huge variability and the sometimes-borderline statistics.
On top, there are a lot of optional experiments I am sure the authors are aware of that should be done at least in the future. For instance, how does HIV-1 upregulate SNAT7, is a viral accessory protein involved? What is the mechanism of SNAT7 dependent SAMHD1 phosphorylation? Does SNAT7 (or glutamine) regulate the activity of the SAMHD1 associated kinase / phosphatase) If so, does this impact on other targets of these enzymes?
Referees cross-commenting
I think the comments from the other referees are reasonable and consistent with my assessment
Strength and limitations see above
Significance: I think this work is of high interest for virologists working in the field of HIV-1 and infection of myeloid cells. In case SNAT7 (and hence glutamine) indeed regulates the phosphorylation of SAMHD1, there could potentially be broad relevance of this work. However unfortunately, this aspect remains underdeveloped and is also not discussed
Field of expertise: HIV-1, immunology, cell biology
The difference between us and the people we were trying to serve: they probably had less food than we did.
Speaks volumes about the significance of the experiments objective
Food became an obsession for the participants.
powerful wording and description of how much food took over their lives.
As semistarvation progressed,
The next 4 paragraphs truly visualizes starvation syndrome, how your body goes into survival mode and the psychological effects that can occur.
KevinNetwork
RIP KevinNetwork
nalist
add 2026 no?
inboxes the filter decided to fill “Same deal. Different tolerance.”
no way this is accessible. too small
Three signals at once. This mailbox opened twice last quarter, then went quiet for 74 days. Decay, not death. The domain moved mailbox providers in April, so the old reputation does not carry over. And subscribers who joined the same way, same webinar, have started marking us spam. A va
is this accessible? to read and see. ? is the font the issue or the size?
Vy
fourth
Kat
put her third
Find the one figure that decides it, then give your recommendation with that figure. For two options of different sizes, that figure is the price per unit.
Identify the figure that should be compared, then base your recommendation on that figure. If the options come in different sizes, compare their price per unit before deciding.
someone should tell bill gates that the optimal human nutrition is the carnivore diet ("a pound beef a day keeps the doctor away"), with the smallest ecological footprint, because ruminant animals (cows, sheep, goats) only need grass and water.
source: shawn baker - the carnivore diet (2019)
but apparently, bill gates is too busy expanding hell on earth, trying to preserve human overpopulation and hightech at all cost... i just hope that he fails as soon as possible, to minimize the side-effects of his stupid experiment (war on nature, luciferianism)
Find how many pesos Herminia saves by choosing the cheaper supplier.
After calculating the total cost from each supplier, how many pesos will Herminia save by choosing the lower-cost supplier?
Do not sign, pay, or pass the document on. Recheck your own math once, then raise the difference with the person who issued the figure. Say both numbers: "The receipt prints PHP 2,320, but the items add to PHP 2,220."
Do not sign, approve, pay, or forward the document until the discrepancy has been resolved. Recheck your calculations once, then report the difference to the person who prepared the document. Clearly state both figures, for example: "The receipt shows PHP 2,320, but the line items total PHP 2,220."
Summary:
"Gas Town helps you with the tedium of running lots of Claude Code instances."
"Claude Code is just a building block, and it’s going to be all about AI workflows and 'Kubernetes for agents'."
"If you’re not at least Stage 7, or maybe Stage 6 and very brave, then you will not be able to use Gas Town."
"You are a Product Manager, and Gas Town is an Idea Compiler."
"The town (Go binary
gt) manages and orchestrates all the workers across all your rigs."
"Beads are the atomic unit of work in Gas Town."
"If there is work on your hook, YOU MUST RUN IT."
"Sessions are ephemeral; they are the 'cattle' in the Kubernetes 'pets vs cattle' metaphor."
"Molecules are workflows, chained with Beads."
"Even though the path is fully nondeterministic, the outcome — the workflow you wanted to run — eventually finishes."
"Everything in Gas Town, all work, rolls up into a Convoy."
"The focus is throughput: creation and correction at the speed of thought."
Concepts & Tools:
gt, gt sling, gt nudge, gt seance, gt handoff, bd create, bd show.References:

💻/thinkpad/🧊/me/📓/2026/7/0/5/=/lindy.learn
This article has been published in Scientific Reports on 04 May 2026 (https://doi.org/10.1038/s41598-026-51310-7). (from Siqi Xia)
OSSは世界中のセキュリティベンダーや研究者が安全性を検証しています
ここまで書いて大丈夫かな?全部をやっているわけではないし保証できないと思うので、本記事と関係が薄い内容なので、以下の様な表現でも良いかなって思いました。 「OSSはリリース後、多くの人たちによって検証されてたり、セキュリティベンダーなどのより検証してくれています。リリース後しばらく時間をおくことでマルウェアなどが仕込まれている可能性が低くなり、安全性を高めることができます。」くらいでどうかな?
prek runでフックを手動実行
これは、 pre-commitにない機能? prekの特徴であればその事を書いておくと良いかも
prekに移行しています
そうなんだー。これは注目ですね。
カスタムスクリプトはGitの管理対象外
対象外とは?? コミットできない? コミットしない? そもそも .git/ 配下だからpullしても共有されないって意味? Gitフックを使っていないのでこの部分の意図がわからなかったです。
Paradigm Design
https://bafybeiedbtomg2udebl5sgoc7eyraxduotlphicybbffvbkuwz7bttu7zm.ipfs.inbrowser.link/?filename=%3Dmetadesigners.network.outlining.metadesign.html#Paradigm_Design
Paradigms are
Paradigms are - complex, self-perpetuating systems
that are co-sustained by habitual processes
that are part of the prevailing social, cultural, economic, aesthetic, psychological, technological and linguistic milieu.
As these factors reinforce one another, they - fiercely resist change - unless they can be addressed in a comprehensive and joined-up way.
Humans Are Form-Givers
humans are form givers
combine that with time binding capacity
new affordances that make things work in a pleasing and effective way.
affordances.work.effective.pleasing
need radical reform
need radical reform of - the existing economic and - political system
Addgene:47108
DOI: 10.1016/j.stemcr.2026.102980
Resource: RRID:Addgene_47108
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SciCrunch record: RRID:Addgene_47108
Addgene:42230
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Resource: RRID:Addgene_42230
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Addgene:11349
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Resource: RRID:Addgene_11349
Curator: @nmaralla
SciCrunch record: RRID:Addgene_11349
RRID: AB_796155
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Sigma-Aldrich Cat# L7543, RRID:AB_796155)
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RRID: AB_10861551
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Resource: (Abcam Cat# ab109199, RRID:AB_10861551)
Curator: @nmaralla
SciCrunch record: RRID:AB_10861551
RRID: AB_2737282
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Curator: @nmaralla
SciCrunch record: RRID:AB_2737282
RRID: AB_2757076
DOI: 10.1016/j.stemcr.2026.102979
Resource: (ABclonal Cat# A0263, RRID:AB_2757076)
Curator: @nmaralla
SciCrunch record: RRID:AB_2757076
RRID: AB_2938687
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Abcam Cat# ab179695, RRID:AB_2938687)
Curator: @nmaralla
SciCrunch record: RRID:AB_2938687
RRID: AB_446161
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Abcam Cat# ab21286, RRID:AB_446161)
Curator: @nmaralla
SciCrunch record: RRID:AB_446161
RRID: AB_2941028
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Abcam Cat# ab268020, RRID:AB_2941028)
Curator: @nmaralla
SciCrunch record: RRID:AB_2941028
RRID: AB_11129103
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Abcam Cat# ab124964, RRID:AB_11129103)
Curator: @nmaralla
SciCrunch record: RRID:AB_11129103
RRID: AB_561053
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Cell Signaling Technology Cat# 2118, RRID:AB_561053)
Curator: @nmaralla
SciCrunch record: RRID:AB_561053
RRID: AB_796188
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Sigma-Aldrich Cat# A0731, RRID:AB_796188)
Curator: @nmaralla
SciCrunch record: RRID:AB_796188
RRID: AB_10854564
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Thermo Fisher Scientific Cat# 14-5698-82, RRID:AB_10854564)
Curator: @nmaralla
SciCrunch record: RRID:AB_10854564
RRID: AB_10000511
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Novus Cat# NB600-408, RRID:AB_10000511)
Curator: @nmaralla
SciCrunch record: RRID:AB_10000511
RRID: AB_262054
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Sigma-Aldrich Cat# A5228, RRID:AB_262054)
Curator: @nmaralla
SciCrunch record: RRID:AB_262054
RRID: AB_477585
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Sigma-Aldrich Cat# T6793, RRID:AB_477585)
Curator: @nmaralla
SciCrunch record: RRID:AB_477585
RRID: SCR_003070
DOI: 10.1016/j.stemcr.2026.102979
Resource: ImageJ (RRID:SCR_003070)
Curator: @nmaralla
SciCrunch record: RRID:SCR_003070
RRID: SCR_018771
DOI: 10.1016/j.stemcr.2026.102979
Resource: DoubletFinder (RRID:SCR_018771)
Curator: @nmaralla
SciCrunch record: RRID:SCR_018771
RRID: SCR_022206
DOI: 10.1016/j.stemcr.2026.102979
Resource: Harmony (RRID:SCR_022206)
Curator: @nmaralla
SciCrunch record: RRID:SCR_022206
RRID: SCR_007322
DOI: 10.1016/j.stemcr.2026.102979
Resource: SEURAT (RRID:SCR_007322)
Curator: @nmaralla
SciCrunch record: RRID:SCR_007322
RRID: SCR_017344
DOI: 10.1016/j.stemcr.2026.102979
Resource: Cell Ranger (RRID:SCR_017344)
Curator: @nmaralla
SciCrunch record: RRID:SCR_017344
RRID: CVCL_0298
DOI: 10.1016/j.stemcr.2026.102979
Resource: (ATCC Cat# CCL-153, RRID:CVCL_0298)
Curator: @nmaralla
SciCrunch record: RRID:CVCL_0298
RRID: AB_141607
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Thermo Fisher Scientific Cat# A-21202, RRID:AB_141607)
Curator: @nmaralla
SciCrunch record: RRID:AB_141607
RRID: AB_2535794
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Thermo Fisher Scientific Cat# A-21208, RRID:AB_2535794)
Curator: @nmaralla
SciCrunch record: RRID:AB_2535794
RRID: AB_141633
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Molecular Probes Cat# A-21203, RRID:AB_141633)
Curator: @nmaralla
SciCrunch record: RRID:AB_141633
RRID: AB_2535792
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Thermo Fisher Scientific Cat# A-21206, RRID:AB_2535792)
Curator: @nmaralla
SciCrunch record: RRID:AB_2535792
RRID: AB_2535795
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Thermo Fisher Scientific Cat# A-21209, RRID:AB_2535795)
Curator: @nmaralla
SciCrunch record: RRID:AB_2535795
RRID: AB_2925789
DOI: 10.1016/j.stemcr.2026.102979
Resource: RRID:AB_2925789
Curator: @nmaralla
SciCrunch record: RRID:AB_2925789
RRID: AB_141637
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Molecular Probes Cat# A-21207, RRID:AB_141637)
Curator: @nmaralla
SciCrunch record: RRID:AB_141637
RRID: AB_2099233
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Cell Signaling Technology Cat# 7074, RRID:AB_2099233)
Curator: @nmaralla
SciCrunch record: RRID:AB_2099233
RRID: AB_330924
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Cell Signaling Technology Cat# 7076, RRID:AB_330924)
Curator: @nmaralla
SciCrunch record: RRID:AB_330924
RRID: AB_1841066
DOI: 10.1016/j.stemcr.2026.102979
Resource: (Sigma-Aldrich Cat# P0068, RRID:AB_1841066)
Curator: @nmaralla
SciCrunch record: RRID:AB_1841066
RRID: AB_3750426
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3750426
Curator: @nmaralla
SciCrunch record: RRID:AB_3750426
RRID: AB_430833
DOI: 10.1016/j.stem.2026.05.012
Resource: (Promega Cat# W4011, RRID:AB_430833)
Curator: @nmaralla
SciCrunch record: RRID:AB_430833
Jackson LaboratoryStrain#035670
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:IMSR_JAX:035670
Curator: @nmaralla
SciCrunch record: RRID:IMSR_JAX:035670
Jackson LaboratoryStrain#027139
DOI: 10.1016/j.stem.2026.05.012
Resource: (IMSR Cat# JAX_027139,RRID:IMSR_JAX:027139)
Curator: @nmaralla
SciCrunch record: RRID:IMSR_JAX:027139
Jackson LaboratoryStrain#028867
DOI: 10.1016/j.stem.2026.05.012
Resource: (IMSR Cat# JAX_028867,RRID:IMSR_JAX:028867)
Curator: @nmaralla
SciCrunch record: RRID:IMSR_JAX:028867
American Type Culture CollectionStrain#CRL-3216
DOI: 10.1016/j.stem.2026.05.012
Resource: (RRID:CVCL_0063)
Curator: @nmaralla
SciCrunch record: RRID:CVCL_0063
RRID: AB_696697
DOI: 10.1016/j.stem.2026.05.012
Resource: (Millipore Cat# 657012-100UL, RRID:AB_696697)
Curator: @nmaralla
SciCrunch record: RRID:AB_696697
RRID: AB_141637
DOI: 10.1016/j.stem.2026.05.012
Resource: (Molecular Probes Cat# A-21207, RRID:AB_141637)
Curator: @nmaralla
SciCrunch record: RRID:AB_141637
RRID: AB_2078082
DOI: 10.1016/j.stem.2026.05.012
Resource: (Cell Signaling Technology Cat# 2466, RRID:AB_2078082)
Curator: @nmaralla
SciCrunch record: RRID:AB_2078082
RRID: AB_2535792
DOI: 10.1016/j.stem.2026.05.012
Resource: (Molecular Probes Cat# A-21206, RRID:AB_2535792)
Curator: @nmaralla
SciCrunch record: RRID:AB_2535792
Jackson LaboratoryStrain#016963
DOI: 10.1016/j.stem.2026.05.012
Resource: (IMSR Cat# JAX_016963,RRID:IMSR_JAX:016963)
Curator: @nmaralla
SciCrunch record: RRID:IMSR_JAX:016963
RRID: AB_1904176
DOI: 10.1016/j.stem.2026.05.012
Resource: (Cell Signaling Technology Cat# 4466, RRID:AB_1904176)
Curator: @nmaralla
SciCrunch record: RRID:AB_1904176
RRID: AB_2223172
DOI: 10.1016/j.stem.2026.05.012
Resource: (Cell Signaling Technology Cat# 4970, RRID:AB_2223172)
Curator: @nmaralla
SciCrunch record: RRID:AB_2223172
RRID: AB_2936428
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_2936428
Curator: @nmaralla
SciCrunch record: RRID:AB_2936428
RRID: AB_3712409
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3712409
Curator: @nmaralla
SciCrunch record: RRID:AB_3712409
RRID: AB_3750425
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3750425
Curator: @nmaralla
SciCrunch record: RRID:AB_3750425
RRID: AB_3750424
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3750424
Curator: @nmaralla
SciCrunch record: RRID:AB_3750424
RRID: AB_3750423
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3750423
Curator: @nmaralla
SciCrunch record: RRID:AB_3750423
RRID: AB_3750422
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3750422
Curator: @nmaralla
SciCrunch record: RRID:AB_3750422
RRID: AB_2936887
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_2936887
Curator: @nmaralla
SciCrunch record: RRID:AB_2936887
RRID: AB_3722983
DOI: 10.1016/j.stem.2026.05.012
Resource: RRID:AB_3722983
Curator: @nmaralla
SciCrunch record: RRID:AB_3722983
RRID:SCR_006281
DOI: 10.1016/j.molcel.2026.06.019
Resource: ScriptManager (RRID:SCR_021797)
Curator: @nmaralla
SciCrunch record: RRID:SCR_021797
RRID: SCR_021797
DOI: 10.1016/j.molcel.2026.06.019
Resource: ScriptManager (RRID:SCR_021797)
Curator: @nmaralla
SciCrunch record: RRID:SCR_021797
RRID: AB_10892860
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Cell Signaling Technology Cat# 5127, RRID:AB_10892860)
Curator: @nmaralla
SciCrunch record: RRID:AB_10892860
RRID: AB_2800208
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Cell Signaling Technology Cat# 93702, RRID:AB_2800208)
Curator: @nmaralla
SciCrunch record: RRID:AB_2800208
RRID: AB_2043797
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Thermo Fisher Scientific Cat# 12-1178-42, RRID:AB_2043797)
Curator: @nmaralla
SciCrunch record: RRID:AB_2043797
RRID: AB_10668830
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Thermo Fisher Scientific Cat# 11-9886-42, RRID:AB_10668830)
Curator: @nmaralla
SciCrunch record: RRID:AB_10668830
RRID: AB_2535792
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Molecular Probes Cat# A-21206 (also A21206), RRID:AB_2535792)
Curator: @nmaralla
SciCrunch record: RRID:AB_2535792
RRID: AB_11180865
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Thermo Fisher Scientific Cat# A10037, RRID:AB_11180865)
Curator: @nmaralla
SciCrunch record: RRID:AB_11180865
RRID: AB_2534017
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Thermo Fisher Scientific Cat# A10042, RRID:AB_2534017)
Curator: @nmaralla
SciCrunch record: RRID:AB_2534017
RRID: AB_90456
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Millipore Cat# AP124P, RRID:AB_90456)
Curator: @nmaralla
SciCrunch record: RRID:AB_90456
RRID: AB_141607
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Thermo Fisher Scientific Cat# A-21202, RRID:AB_141607)
Curator: @nmaralla
SciCrunch record: RRID:AB_141607
RRID: AB_772206
DOI: 10.1016/j.molcel.2026.06.003
Resource: (GE Healthcare Cat# NA934, RRID:AB_772206)
Curator: @nmaralla
SciCrunch record: RRID:AB_772206
RRID: AB_1550038
DOI: 10.1016/j.molcel.2026.06.003
Resource: (Cell Signaling Technology Cat# 3900, RRID:AB_1550038)
Curator: @nmaralla
SciCrunch record: RRID:AB_1550038
RRID: AB_2562415
DOI: 10.1016/j.immuni.2026.06.006
Resource: (BioLegend Cat# 117334, RRID:AB_2562415)
Curator: @nmaralla
SciCrunch record: RRID:AB_2562415
RRID: AB_2564590
DOI: 10.1016/j.immuni.2026.06.006
Resource: (BioLegend Cat# 103149, RRID:AB_2564590)
Curator: @nmaralla
SciCrunch record: RRID:AB_2564590