Note: This response was posted by the corresponding author to Review Commons. The content has not been altered except for formatting.
Learn more at Review Commons
Reply to the reviewers
Reviewer #1 (Evidence, reproducibility and clarity (Required)):
__
In this manuscript, the authors describe the discovery of a molecular regulator of the immune transcriptional program, which is activated by intestinal distension upon bacterial colonization of the C. elegans intestine. Taking advantage of the fact that inhibition of aex-5 is known to cause intestinal distension and a C-type lectin gene clec-60 as a marker for the immune response to intestinal distension (clec-60p::gfp), the authors performed a forward genetic screen for suppressors of the immune response activation. Of the two mutants isolated, they focused on the stronger suppressor, which corresponded to a cysteine-type DUB, the Ubiquitin Specific Peptidase-14 (usp-14). Through rescue experiments, phenocopy analyses, and quantitative RT-PCR, they validated usp-14 as the causal gene and initiated characterization of its role in immune response activation. To this end, the authors investigated the tissue of action, identifying the intestine as the tissue in which usp-14 mediates the regulation of the immune response.
Through transcriptomic analyses, they found that the signalling pathway likely regulated by usp-14 in response to intestinal distension is the Wnt pathway, as they have observed reduction in the transcriptional level of some of the Wnt pathway components in usp-4(tm1481), in response to infection with S. aureus. Additionally, transcriptomic data indicate that usp-14 plays a role in immunity regulation even in the absence of infection. Based on these findings, the authors propose that usp-14 has a dual role in immune regulation: one in surveillance immunity, preventing overactivation of immune responses, and another as a mediator of pathogen-induced responses, such as those triggered by P. aeruginosa or S. aureus. The experiments are rigorous and the results robust; however, some points would benefit from further investigation or clarification.
__Response: We thank the reviewer for an excellent summary of our work and for the valuable feedback.
Comment: The expression domain of usp-14 appears to be quite expanded based on single cell RNAseq data (e.g. PMID: 28818938) therefore it is likely that the transgenes used for expression analysis are lacking key regulatory information. Alternative methods like smFISH would be more appropriate to characterise the spatiotemporal pattern of usp-14 expression in more detail.
Response: We thank the reviewer for this valuable suggestion. In the original version of the manuscript, we used a 714 bp region upstream of the usp-14 start codon to generate the transcriptional reporter. In the revised manuscript, we reconstructed the reporter using a longer 1924 bp upstream promoter region together with a portion of exon 1. Using this updated reporter, we observed substantially broader expression of usp-14, particularly during the early larval stages. These results are described on page 6, lines 148-153: “We next examined the spatiotemporal expression pattern of usp-14 in C. elegans. To this end, we generated transgenic worms expressing GFP under the control of the usp-14 promoter (usp-14p::gfp). During early larval development, usp-14 was broadly expressed across multiple tissues (Figure 3A). However, in L4 larvae and adult animals, expression became more restricted and was predominantly observed in the intestine and a subset of neuronal cells. Notably, both intestinal and neuronal expression persisted throughout development (Figure 3A).”
Comment: __The mutation mapped in usp-14(jsn19) is a missense mutation (E122K) that suppresses the immune response to a degree comparable to the usp-14(tm1481) deletion allele. However, the authors do not show the functional domains in Fig. 1E potentially affected by this missense mutation.
__Response: We have now updated Figure 1E to include the functional domains of USP-14 and mapped both the usp-14(jsn19) missense allele and the usp-14(tm1481) deletion allele onto the protein schematic.
Comment: __How USP-14 regulates Wnt and how Wnt signalling relates to activation of immune responses is not fully supported. Are the Wnt components mentioned in the study induced specifically in the intestine upon infection and does USP-14 act in the intestine in the context of this regulation? How do the authors interpret that both Wnt ligands and receptors are induced ? Does Wnt signalling appear as a GO term in the transcriptomic analysis? The authors can include Wnt signalling components in the analysis of the transcriptomic results.
__Response: We thank the reviewer for these insightful comments. Previous studies have shown that the Wnt pathway components examined in our study are induced in the intestine upon infection and function within the intestine to regulate host defense against bacterial pathogens (PMID: 29768179; PMID: 36323254).
We did not observe significant enrichment of Wnt signaling terms in the GO analysis of our transcriptomic dataset. We believe this is likely due to the stringent thresholds used for differential expression analysis (fold change > 2 and p At present, the precise mechanism by which USP-14 regulates Wnt pathway components remains unclear. One possibility is that USP-14 influences Wnt signaling indirectly through additional substrates or interacting proteins that regulate transcriptional outputs. We have now clarified this point in the Discussion (page 13, lines 344–349): “These observations raise the possibility that additional USP-14 substrates or interacting proteins modulate transcriptional outputs downstream of intestinal distension. Future studies aimed at identifying the direct substrates of USP-14 and defining how USP-14 interfaces with neuronal ACC-4 signaling and other distension-responsive pathways will provide important mechanistic insight into how intestinal distension is coupled to innate immune activation.”
Regarding the simultaneous induction of Wnt ligands and receptors, we interpret this as a potential amplification or reinforcement mechanism that enhances Wnt/β-catenin signaling during infection-induced intestinal distension. However, further studies will be required to determine the mechanistic significance of this coordinated transcriptional regulation.
Comment: __Overall, in most of the figures, the micrographs are in general quite dark and exhibit poor contrast between signal and background, particularly in Fig. 1, panels B and J, and Fig. 2, panels B and F (upper rows). Even though these panels are intended to show absence of response, the outlines of the worms are difficult to discern.
__Response: We thank the reviewer for the feedback. We have now improved the image presentation throughout the manuscript by either increasing the intensity or adding dotted outlines to more clearly indicate worm positions.
Comment: __In Figure S3, panels A and B, the pmk-1(km25); usp-14(tm1481) animals subjected to aex-5 RNAi show some level of fluorescence/response induction comparable to pmk-1(km25) alone. This observation is not discussed in the text.
__Response: We have now discussed this observation in the text. These results are described on page 9, lines 244-248: “Although pmk-1(km25);usp-14(tm1481) worms displayed relatively higher GFP levels than usp-14(tm1481) single mutants upon aex-5 RNAi treatment, this effect likely reflects the elevated basal GFP expression observed in pmk-1(km25) mutants (Figure S4B). Importantly, pmk-1(km25);usp-14(tm1481) animals still exhibited significantly lower GFP levels than pmk-1(km25) single mutants.”
Reviewer #1 (Significance (Required)):
__
__Comment: __The work is interesting because it expands some previous work in the field demonstrating immune response induction as a consequence of intestinal distension even in the absence of bacterial infection. This is known to be mediated by the neuronal acetylcholine receptor ACC-4, which signals to the intestine where it regulates immune genes via the Wnt pathway. However, how USP-14 relates to ACC-4 is currently unclear and whether USP-14 function is really required in the intestine to control Wnt signalling is not demonstrated. The authors should include a model to describe how their findings relate to the previous literature and how USP-14 may link mechanistically to Wnt signalling pathway activation.
__Response: We thank the reviewer for this insightful comment. We agree that the relationship between USP-14, ACC-4, and Wnt signaling requires further clarification. As suggested by the reviewer, we have now included a model summarizing the current understanding of intestinal distension-induced immune activation and integrating our findings with previous literature (Figure 6H).
Comment: __It remains also unclear whether usp-14 is the only deubiquitinase involved in intestinal distension-induced signalling via the Wnt pathway, or whether other paralog usp genes might also contribute to regulation of immune-responsive transcription. Notably, several mammalian deubiquitinases have established roles in cancer suppression and inflammatory response and innate immunity in other systems so this would increase the potential significance of the work.
__Response: We thank the reviewer for this valuable suggestion. To systematically examine whether additional DUBs contribute to intestinal distension-induced immune activation, we performed an RNAi screen targeting all DUBs available in the Ahringer RNAi library using the aex-5(sa23);clec-60p::gfp reporter strain. Among the DUBs tested, knockdown of usp-14 produced the strongest suppression of clec-60p::gfp expression. Although knockdown of usp-5 also partially suppressed GFP induction, usp-5 RNAi did not affect survival during P. aeruginosa infection, suggesting that usp-5 is not required for host defense under these conditions. Together, these findings identify USP-14 as the major DUB required for intestinal distension-induced immune activation in our experimental system. These results are now included in Figure 1G, H, and Figure S2.
Reviewer #2 (Evidence, reproducibility and clarity (Required)):
__
Summary
C. elegans are soil-dwelling nematodes that feed on bacteria and fungi and thus must be able to distinguish between innocuous and pathogenic species of microbes to survive. Though they lack adaptive immunity, these animals have an ancient version of an innate immune system that has no circulating sentinel or phagocytic cells yet can still mount a response to pathogen exposure. A consequence of the mode of infection of some ingested bacterial pathogens is intestinal distension which by itself, even in the absence of pathogens, is sufficient to trigger the expression of genes encoding immune effectors, including proteins that are bactericidal. The complete mechanistic scheme connecting intestinal distension to the expression of immunity genes has not been resolved, motivating the authors to perform a forward genetic screen for additional components of this pathway. One mutant that the authors isolated was usp-14, encoding an evolutionarily conserved deubiqutinating enzyme. Functional analysis revealed that usp-14 confers protection from microbial pathogens and that the intestine is its primary site of action for its role in host defense. The authors' data indicate that while USP-14 regulates the expression of innate immunity genes that are induced by intestinal distension, surprisingly it functions independently of several canonical innate immune signaling pathways, including the pmk-1/p38 MAPK pathway. Instead, USP-14 appears to act through Wnt signaling to regulate immune effectors by upregulating the expression of several components of that pathway, including the C. elegans ß-catenin ortholog bar-1. This places usp-14 within a gut-brain axis previously shown to control the C. elegans innate immune response through acetylcholine-mediated activation of Wnt signaling. The authors' findings provide new mechanistic insight to this pathway and add to the understanding of ubiqutination as an immune regulatory module.
__Response: We thank the reviewer for providing an excellent summary of our work.
Major comments
__1. There are three types of experiments in which the authors use the same set of controls across several different figure panels, as stated in the legend to Figure 2. First, when quantifying GFP levels of clec-60::gfp in RNAi-treated animals, the authors use the same clec-60p::gfp and usp-14(jsn19);clec-60p::gfp controls for Fig. 1K, 2C, and 2G. For infection assays with S. aureus NCTC8325, the survival plots for the clec-60p::gfp and usp-14(jsn19);clec-60p::gfp controls shown in Fig. 2E are the same as the ones used in Fig. 1M. Similarly, for infection assays with P. aeruginosa PA14, the survival plots for the clec-60p::gfp and usp-14(jsn19);clec-60p::gfp controls shown in Fig. 2I is the same as was used for Fig 1I. In each case, if the authors in fact collected all of the data for each strain that they studied at the same time but then chose to parse larger datasets into separate figure panels to make it more clear to the reader, then this approach is valid but the authors need to explicitly state that this is what they did. However, if the data pertaining to the control strains were collected at a different time or if it comes from a separate biological replicate, then re-using data from the controls is not appropriate because it would not accurately reflect the specific conditions of the experiment to which the data are being compared. If this is indeed the scenario, then the authors will need to repeat these experiments and include the appropriate control in each iteration.
__Response: While preparing the manuscript, these experiments were performed simultaneously. Therefore, all panels that share controls have results from experiments performed simultaneously and represent the same biological replicate. We have added this additional information in the relevant figure legends.
Comment: __2. From the legends describing figure panels that include data pertaining to clec-60p::gfp expression levels as assessed by fluorescence microscopy it seems that, in general, the authors measured GFP fluorescence in about 30 animals to produce quantitative data. How many biological replicates of these types of experiments were carried out? This is not explicitly stated in the section describing fluorescence imaging in the Methods section. Following the description of their methodology regarding statistical analysis of survival curves from microbial infection assays, however, the authors state that, "[a]ll experiments were performed independently at least three times unless otherwise noted." Does this statement apply to microscopy or only to experiments involving infection assays? If the data reporting quantitation of GFP signal is based on only 30 animals, then additional biological replicates are necessary, along with appropriate statistical analyses.
__Response: The quantified GFP fluorescence data are derived from three independent biological replicates. In each experiment, we typically imaged and quantified approximately 10 worms per condition, yielding a total of ~30 worms analyzed per genotype or treatment across all replicates (except Figure S1B, where we had two independent replicates). We have added the number of experiments in the figure legends for these data.
Comment: __3. The authors have made all of the RNASeq data publicly available on the Sequence Read Archive, and they include data from several pairwise comparisons for differential gene expression analysis in their supplemental files. One of the most important facts to come out of the authors' Gene Ontology analyses of their RNASeq data is that the genes that are upregulated in a usp-14-dependent manner upon intestinal distension are enriched for those whose products play a role in innate immunity/host defense. The authors should say more about these genes. Are there any commonalities between them with regard to function? Are any of them targets of transcription factors that are known to function in C. elegans innate immunity? If so, this could provide clues as to what the substrates of USP-14 might be. Importantly, the specific identity of the genes assigned in the GO analyses to biological processes pertaining to innate immunity and host defense should be revealed in a supplemental file, and designated as being dependent on or independent of usp-14 for their expression during intestinal distension.
__Response: We thank the reviewer for this insightful suggestion. We have now expanded the Results section to describe the functional categories enriched among the USP-14-dependent intestinal distension-induced immune genes, including C-type lectins, ShK toxin domain-containing proteins, and lysozymes (page 7, lines 194-196).
In addition, we compared our transcriptomic dataset with previously published transcription factor-regulated gene sets using WormExp analysis and identified a substantial overlap with genes regulated by the GATA transcription factor ELT-2. These new analyses are described on page 7, lines 197-210: “To identify transcription factors potentially involved in intestinal distension-induced immune activation, we performed transcription factor enrichment analysis using WormExp on genes upregulated in N2 worms following aex-5 RNAi treatment. This analysis revealed a substantial overlap between aex-5 RNAi-induced genes and genes regulated by the GATA transcription factor ELT-2 (Figure S3D). We next examined whether USP-14-dependent immune genes overlapped with ELT-2-dependent immunity genes induced by intestinal distension. To this end, we identified innate immune genes common to both ELT-2-regulated gene sets and aex-5 RNAi-induced genes. Strikingly, these ELT-2-dependent intestinal distension-induced immune genes showed substantial overlap with USP-14-dependent immune genes (Figure S3E and Table S5), suggesting that USP-14 may regulate distension-induced immunity, at least in part, through ELT-2-dependent transcriptional programs. Consistent with this possibility, RNAi-mediated knockdown of elt-2 did not further increase the susceptibility of usp-14(tm1481) worms to P. aeruginosa infection relative to wild-type worms (Figure S3F), supporting a model in which USP-14-mediated immune responses require ELT-2 activity.”
Finally, we have created a new table (Table S5) that specifies the identity of the genes assigned in the GO analyses to biological processes pertaining to innate immunity and host defense, for USP-14-dependent and independent genes.
Comment: __4. The authors' data suggest that in response to bacterial infection USP-14 upregulates the expression of bar-1, along with other components of the Wnt signaling pathway, which in turn upregulates innate immunity genes. This could be further substantiated by directly demonstrating that there are USP-14-regulated innate immunity genes whose induced expression in the presence of microbial pathogens also requires bar-1. Along those lines, an initial test would be to assess clec-60p::gfp expression in bar-1 animals versus bar-1;usp-14 double mutants, similar to the experiment whose results are reported in Fig. S4. If generating the bar-1;usp-14 double mutant is not feasible, then RNAi could be used to knockdown bar-1 expression in clec-60p::gfp;usp-14(tm1481) animals. To expand this analysis, the expression of the six innate immunity genes shown to be regulated upon intestinal distension in usp-14-dependent manner could be measured in the presence and absence of intestinal distension or microbial infection in bar-1 and bar-1;usp-14 animals by qRT-PCR. At a minimum, the authors should conduct a bioinformatics analysis to compare the USP-14-regulated innate immunity genes identified in their RNAseq studies to lists of known BAR-1 transcriptional targets to look for potential overlap.
__Response: We agree that extending these analyses to qRT-PCR experiments examining additional immune genes would be informative. However, both bar-1 mutants and bar-1 RNAi-treated worms exhibited severe developmental and physiological defects, including sick and dead animals during development, likely reflecting the pleiotropic developmental roles of BAR-1. Although fluorescence imaging and survival assays could be performed by selectively transferring surviving adults, we were concerned that bulk collection of worms for qRT-PCR analyses would introduce confounding effects arising from developmental defects and reduced viability.
To further address the reviewer’s suggestion, we carried out a comparative analysis between USP-14-dependent intestinal distension-induced immune genes and previously identified BAR-1-dependent immune genes. Although transcriptome-wide datasets for BAR-1-dependent pathogen-induced immune genes are not currently available, an earlier study identified seven immune response genes regulated by BAR-1 during infection (PMID: 18981407). We found that six of these genes overlap with the USP-14-dependent intestinal distension-induced immune genes identified in our study. These analyses have now been added to the Results section and included in Table S5.
Comment: __5. While in their Discussion section the authors mention evolutionarily conserved roles for protein ubiquitination as means of immunomodulation, there are few if any comments regarding ubiqutination as a regulatory scheme in C. elegans innate immunity or how their findings enhance our understanding of this phenomenon. Ubiquitination affects C. elegans immunity at multiple levels, from avoidance behavior to gene regulation, and it seems appropriate for the authors to address this in order to more fully contextualize their findings.
__Response: We thank the reviewer for the suggestion. We have now added a new paragraph to the Discussion that places our findings in the context of the existing literature on ubiquitination, deubiquitination, and innate immunity in C. elegans. The discussion is added on pages 11-12, lines 299-312: “Although ubiquitin-mediated signaling has emerged as a central regulator of innate immunity across metazoans (Jiang & Chen, 2011; Mello-Vieira & Dikic, 2026), the contribution of DUBs to host defense in C. elegans remains poorly understood. Previous studies in C. elegans have shown that ubiquitin-dependent processes regulate diverse aspects of immunity, including immune surveillance, xenophagy, and pathogen tolerance (Garcia-Sanchez et al, 2021). Perturbations in proteasome function have also been shown to activate surveillance immunity (Ghosh & Singh, 2026; Troemel et al, 2026), highlighting the importance of ubiquitin-associated pathways in sensing pathogen-induced cellular damage. However, most prior studies have focused on ubiquitin ligases, proteasome-associated pathways, or global ubiquitin signaling rather than on specific DUBs directly regulating antibacterial immune responses. To our knowledge, our study provides the first direct evidence that a specific DUB regulates antibacterial innate immunity in C. elegans. Thus, our findings establish USP-14 as a previously unrecognized regulator of host defense and identify deubiquitination as an important regulatory layer in intestinal distension-mediated immunity.”
__Minor comments
__1. In the Results section, the authors state that "[k]nockdown of cec-10 led to only a marginal decrease in survival during P. aeruginosa infection" (lines 92 and 93) and that cec-10 "has minimal impact on C. elegans survival during infection" (lines 93 and 94). However, as reported in Supplemental Table 5 the magnitude of the calculated difference in mean survival time between animals treated with RNAi targeting cec-10 and untreated control animals (-20% to -24% and statistically significant in 3/3 replicates) closely approximates the difference in mean survival between usp-14 mutants and controls (-19% to -28% and statistically significant in 3/3 replicates), which the authors clearly find to be significant. If by this metric usp-14 is important for host defense, then so too is cec-10. In light of this, the authors should use different language to describe the impact of cec-10 knockdown on the susceptibility of C. elegans to microbial infection and the potential role of cec-10 in immunity.
Response: We chose not to pursue cec-10 further primarily because it lacks a clear human homolog and because the mutant exhibited reduced expression of the co-injection marker, raising the possibility of broader transgene-related effects. We have modified the text on page 4, lines 93-97: “Knockdown of cec-10 resulted in a significant reduction in survival during P. aeruginosa infection (Figure S1C). However, we did not pursue cec-10 further for two reasons: (i) cec-10(jsn20) mutants exhibited a modest but significant reduction in the myo-2p::mCherry co-injection marker (Figure 1D), raising the possibility of broader transgene-related defects, and (ii) cec-10 lacks a clear human homolog.”
Comment: __2. All of the micrographs in Fig. 1B appear very dark. The GFP expression in the control animals appears dim, making it difficult for the reader to compare the signal in those animals to the GFP expression levels in the mutants. I recommend adjusting the brightness level in an equivalent manner across all of the micrographs to account for this.
__Response: We have increased the brightness of all the images, as suggested by the reviewer.
__Comment: __3. Fig. 1E depicts a gene structure diagram for usp-14 with the position of the point mutation in the jsn19 allele isolated in the authors' forward genetic screen indicated by the amino acid substitution symbol drawn over the second exon. Instead of mixing gene- and protein-level information about the jsn19 allele, I recommend replacing the gene structure diagram with a domain structure diagram of the USP-14 protein that depicts the conserved C19 peptidase and ubiquitin-like domains. The relative position of the E122K substitution should still be noted.
__Response: __We have now updated Figure 1E to include the functional domains of USP-14 and mapped both the usp-14(jsn19) missense allele and the usp-14(tm1481) deletion allele onto the protein schematic.
Comment: __4. Since all of the information in Fig. 1F appears elsewhere in the text, I recommend eliminating this panel.
__Response: We have removed it.
Comment: __5. Regarding the RNAseq analysis, the authors state that 1241 genes are upregulated upon aex-5 knockdown (line 162). The authors then ask which of these genes are regulated by usp-14 in the context of intestinal distension and find that 633 are upregulated a usp-14-dependent manner when aex-5 is targeted by RNAi and that 595 are upregulated even in the absence of usp-14 (Fig. 3D). This accounts for 1228 genes in total, not 1241. Can the authors explain this discrepancy?
__Response: We thank the reviewer for carefully noting this discrepancy. The difference arises from the criteria used to classify genes into the categories shown in Figure 5D (previously Figure 3D). Specifically, genes uniquely upregulated in usp-14(tm1481) worms were defined as genes that were either exclusively induced in usp-14(tm1481) worms or expressed at levels more than 2-fold higher in usp-14(tm1481) worms compared to N2 worms. During this classification, 13 genes that were initially identified as upregulated in N2 worms following aex-5 RNAi were found to be expressed at levels more than 2-fold higher in usp-14(tm1481) worms than in N2 worms (Table S4). These genes were therefore reassigned to the “usp-14(tm1481)-specific” category in the Venn diagram. Consequently, the total number of genes represented in the Venn diagram becomes 1228 instead of 1241. To clarify this point, we have now added an explanation to the figure legend.
Comment: __6. For the sake of clarity, in the legend to Fig. 3D I recommend expanding the description of the categories of genes depicted in the Venn diagram by using the same language as in the first worksheet of Supplemental Table 4.
__Response: We thank the reviewer for the suggestion. We have now added these details to the legend of Figure 5D (previously Figure 3D). The legend reads: “(D) Venn diagram showing the overlap between genes upregulated upon aex-5 RNAi in N2 and usp-14(tm1481) worms. The GO analyses for the biological processes of unique and common genes are shown. USP-14-dependent genes were defined as genes that were either exclusively upregulated in N2 worms or expressed at levels greater than 2-fold higher in N2 worms than in usp-14(tm1481) worms. USP-14-independent genes were defined as genes upregulated in both N2 and usp-14(tm1481) worms with expression differences of less than 2-fold between the two strains. Genes uniquely upregulated in usp-14(tm1481) worms were defined as genes that were either exclusively induced in usp-14(tm1481) worms or expressed at levels greater than 2-fold higher in usp-14(tm1481) worms than in N2 worms. Thirteen genes classified as upregulated in N2 worms were more than 2-fold higher in usp-14(tm1481) worms than in N2 worms (Table S4) and were therefore included in the usp-14(tm1481)-specific category.”
Comment: __7. In Fig. 4B, the authors' annotation indicates that there is a statistically significant difference (**, p
__Comment: __8. In Fig. S5, the shade of blue used to represent the data from the nhr-49(nr2041);usp-14(tm1481);clec60p::gfp animals in panel E is different from that used to represent data from the same animals in panel B. This breaks the pattern of all of the other panels of this figure in which the data pertaining to a given phenotype are depicted in the same color. Also, in the symbol key in panel E there is an extra semi-colon before clec-60p::gfp that should be eliminated in the second genotype notation.
__Response: We thank the reviewer for carefully examining the figure and for bringing these issues to our attention. We have made the changes.
Comment: __9. The authors' data show that USP-14 regulates bar-1 expression, and in the Discussion section they mention that in mammals beta-catenin is a substrate of USP14. Can the authors comment on the possibility of/evidence for BAR-1 autoregulation in C. elegans and the prospect of it being facilitated by USP-14? This could be a minor point to add to the Discussion.
__Response: In both contexts, USP-14 appears to stabilize BAR-1 by regulating it at either the transcriptional or post-translational level. However, it is currently unknown whether BAR-1 regulates USP-14 expression and thereby participates in an autoregulatory mechanism. Nevertheless, we have added to the Discussion that USP14 may regulate the Wnt pathway through both transcriptional and post-translational mechanisms, depending on the biological context.
__Reviewer #2 (Significance (Required)):
__
The study described in this manuscript ties in to the findings from two prior genetic screens carried out in C. elegans that aimed to identify immune regulators (Ren et al., Cell Reports, 2022 and Labed et al., Immunity, 2018). Though their strategies differed, both of these previous studies uncovered a role for acetylcholine receptors in modulating the response to ingested microbial pathogens, especially when infection is associated with intestinal distension, indicating that a neuron-to-gut axis controls innate immunity in C. elegans. Labed and colleagues were the first to show that activation of this pathway results in the upregulation of genes encoding Wnt signaling pathway components, including the worm ortholog of beta-catenin called bar-1, which are necessary for the expression of immune effectors in the intestine. The Labed study also revealed that protein ubiquitination could contribute to regulating host defense gene induction because knockdown of lin-23, the substate binding subunit of a ubiquitin ligase complex that mediates BAR-1 degradation, results in constitutive expression of clec-60p::gfp, the same transcription reporter used by Ghosh and Singh as a readout for the expression of innate immunity genes. In their screen that revisits the Ren et al. approach, Ghosh and Singh find that another protein implicated in regulating protein stability via ubiquitination status, USP-14, also controls the expression of innate immunity genes in response to intestinal distension. Interestingly, their data indicate that it does so by upregulating bar-1. This discovery therefore adds an element of mechanistic detail regarding the regulation of Wnt signaling in immunity. While the Labed data suggest that ubiquitination may regulate BAR-1 at the post-translational level, Ghosh and Singhs' results indicate a second layer of regulation of bar-1 at the transcriptional level that also appears to involve ubiquitination. In this case, USP-14 is predicted to modulate the ubiquitination status of a yet-to-be-identified substrate that directly or indirectly governs bar-1 expression. The authors' findings thus bring the field closer to having a complete picture of the Ach-Wnt pathway in C. elegans. As they point out in the Discussion section of their manuscript, ubiquitination is an evolutionarily conserved yet complex means of tuning the immune system. The work described here helps to shed light on this important immune regulatory mode and could have implications for aspects of epithelial immunity that are in common to both invertebrates and vertebrates.
Response: We thank the reviewer for providing such a thoughtful overview of the field and for placing our findings in the context of previous studies on intestinal distension-induced immunity in C. elegans. We also sincerely appreciate the reviewer’s constructive feedback and insightful comments, which have helped us improve the quality and clarity of the manuscript.
My research interest and specific area of expertise pertains to evolutionarily conserved genetic pathways that control healthspan through affecting cellular resilience later in life. Using C. elegans as a surrogate for aging humans, my group studies age-dependent changes in the activity of regulatory modules that protect older animals from the molecular damage associated with intrinsic and extrinsic sources of cellular stress, with a particular emphasis on microbial infection and oxidative stress.