nlp-29 encodes a small (73-residue) secreted precursor of the YARP (YGGW-amide related peptide) / NLP-CNC antimicrobial-peptide family in Caenorhabditis elegans. The precursor carries an N-terminal signal peptide and is predicted to be processed on pairs of basic residues into several short, glycine/tyrosine-rich, C-terminally amidated peptides (QWGYGGY-amide, GYGGYGGY-amide and repeated GMYGGY/GMYGGW-amide motifs). It is produced in the epidermis (hyp7 syncytium), where its transcription is strongly and rapidly induced by infection with the natural fungal pathogen Drechmeria coniospora, by bacterial infection (Serratia marcescens), by sterile wounding, and by osmotic stress. Infection- and wound-induced expression requires an epidermal signaling cassette (a GPCR/G-protein and PKCdelta/TPA-1 input converging on the TIR-1/SARM-NSY-1-SEK-1-PMK-1 p38 MAPK cascade and the STAT-like factor STA-2 with SNF-12 and the GATA factor ELT-3), whereas the osmotic response is largely p38-independent. nlp-29 lies in a rapidly evolving, positively selected multigene cluster (nlp-27 to nlp-34) of co-regulated antimicrobial peptides that contribute to antifungal host defense. Beyond its role as a putative immune effector, secreted NLP-29 also acts as a cross-tissue signaling ligand for the neuronal orphan G protein-coupled receptor NPR-12, promoting protective sleep after wounding or infection and driving age- and infection-associated dendrite degeneration of PVD and FLP sensory neurons.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005576
extracellular region
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: Localization to the extracellular region, mapped from the UniProt "Secreted" subcellular-location keyword. Consistent with the N-terminal signal peptide (residues 1-22) and with experimental evidence that epidermally produced NLP-29 acts non-cell-autonomously on distant neurons, implying it is secreted.
Reason: NLP-29 is a signal-peptide-bearing secreted peptide; the SubCell-derived extracellular annotation is well supported. Secretion is corroborated experimentally because epidermally expressed NLP-29 must reach neurons expressing its receptor NPR-12 to signal.
Supporting Evidence:
PMID:29301098
direct access to the epidermis was required for NPR-12 to receive NLP-29
|
|
GO:0003674
molecular_function
|
ND
GO_REF:0000015 |
REMOVE |
Summary: Root molecular_function with the ND ("no biological data") evidence code, a WormBase placeholder recorded in 2019 indicating no molecular-function data were curated at that time.
Reason: The ND root placeholder is uninformative and is now superseded: a specific molecular function (neuropeptide receptor binding, GO:0071855) is annotated and has since been experimentally corroborated by demonstration that NLP-29 is a ligand/agonist of the neuronal GPCR NPR-12. Per GO ND conventions, the root "no data" placeholder should be removed once informative molecular-function evidence exists.
Supporting Evidence:
PMID:29301098
we conclude that NPR-12 is the receptor for NLP-29 in mediating aging-associated PVD dendrite degeneration
|
|
GO:0005576
extracellular region
|
ISM
PMID:11717458 Identification of neuropeptide-like protein gene families in... |
ACCEPT |
Summary: Sequence-model (ISM) prediction of extracellular localization, based on the preproprotein/signal-peptide architecture identified for the nlp genes. Redundant with the SubCell-derived IEA annotation but biologically valid.
Reason: The prediction is sound: NLP-29 has a cleavable signal peptide and is a processed, secreted peptide, consistent with an extracellular location. Retained as a valid duplicate of the SubCell IEA annotation.
Supporting Evidence:
PMID:11717458
peptidergic neurotransmitters are encoded as preproproteins that are posttranslationally processed to yield bioactive neuropeptides
|
|
GO:0071855
neuropeptide receptor binding
|
ISM
PMID:11717458 Identification of neuropeptide-like protein gene families in... |
ACCEPT |
Summary: Neuropeptide receptor binding, originally a family-based sequence-model prediction (NLP-29 was named for its similarity to YGGWamide neuropeptides). This prediction is now directly corroborated: synthetic NLP-29 activates the neuronal orphan GPCR NPR-12 (calcium mobilization in NPR-12-transfected cells, specific relative to the related peptide NLP-31 and to NPR-32/beta2-AR), and genetic epistasis places NLP-29 upstream of NPR-12 in both protective-sleep and dendrite-degeneration signaling.
Reason: This is the single molecular activity of NLP-29 with direct experimental support and represents a core function. The ISM annotation remains formally correct, and later work identifies NPR-12 as a bona fide NLP-29 receptor, upgrading confidence in the term without changing it. Retained as core.
Supporting Evidence:
PMID:29301098
induced a significant elevation of calcium, while the solvent-only control did not cause any changes
PMID:33259791
it acts through the neuropeptide receptor NPR-12 in locomotion-controlling neurons that are presynaptic to RIS and that depolarize this neuron to induce sleep
|
|
GO:0050832
defense response to fungus
|
IEP
PMID:18636113 Anti-fungal innate immunity in C. elegans is enhanced by evo... |
NEW |
Summary: nlp-29 is strongly and specifically induced in the epidermis by the natural fungal pathogen Drechmeria coniospora and belongs to a co-regulated antimicrobial-peptide cluster whose overexpression increases resistance to D. coniospora, supporting involvement in antifungal defense. This antifungal role is the flagship, most-studied aspect of nlp-29 biology and is captured by UniProt only as a keyword-derived IEA.
Reason: A defense-response-to-fungus annotation for nlp-29 is well motivated by infection-induced expression plus cluster-level gain-of-function resistance, and matches the UniProt keyword annotation. Added as an expression/genetics-based (IEP) annotation. Important caveat: the nlp-29 single-gene null shows no marked resistance phenotype, so this is an involvement, not a demonstration of individual necessity (see knowledge gaps).
Supporting Evidence:
PMID:18636113
These results indicate that the nlp genes can contribute in vivo to increased resistance to fungal infection, but probably not to osmotic stress.
PMID:15048112
We report here the identification of infection-inducible antimicrobial peptides in Caenorhabditis elegans.
|
|
GO:0007218
neuropeptide signaling pathway
|
IMP
PMID:33259791 Innate Immunity Promotes Sleep through Epidermal Antimicrobi... |
NEW |
Summary: NLP-29 acts as a secreted neuropeptide-like ligand in a cross-tissue signaling pathway: it activates the neuronal GPCR NPR-12, and nlp-29/npr-12 genetic epistasis places NLP-29 upstream of NPR-12 in sleep-promoting and dendrite-degeneration signaling.
Reason: The neuropeptide-signaling role is now experimentally supported (direct NPR-12 activation by synthetic NLP-29 and loss-of-function/epistasis phenotypes for sleep and dendrite degeneration), and matches the UniProt keyword-derived annotation. Added to capture the demonstrated signaling function alongside the antimicrobial-effector role.
Supporting Evidence:
PMID:33259791
it acts through the neuropeptide receptor NPR-12 in locomotion-controlling neurons that are presynaptic to RIS and that depolarize this neuron to induce sleep
PMID:29301098
we conclude that NPR-12 is the receptor for NLP-29 in mediating aging-associated PVD dendrite degeneration
|
Q: Do the individual mature amidated NLP-29 peptides have intrinsic microbicidal activity against D. coniospora or S. marcescens in vitro, and if so by what mechanism?
Suggested experts: Nathalie Pujol, Jonathan J. Ewbank
Q: Is any single nlp gene in the nlp-29 cluster individually required for pathogen resistance, or is the effector function fully redundant?
Suggested experts: Nathalie Pujol, Jonathan J. Ewbank
Experiment: Synthesize each predicted amidated NLP-29 peptide and the full-length mature peptide, and test dose-dependent inhibition of D. coniospora hyphal growth and S. marcescens viability in standard microbicidal/MIC assays, with membrane-permeabilization and nucleic-acid-binding readouts.
Hypothesis: The mature NLP-29 peptides directly inhibit or kill fungi/bacteria.
Type: in vitro antimicrobial assay
Experiment: Generate precise single and higher-order CRISPR deletions across the nlp-27 to nlp-34 cluster and compare survival after D. coniospora infection, distinguishing single-gene necessity from cluster-level redundancy.
Hypothesis: nlp-29 contributes non-redundantly to antifungal survival only in combination with its cluster paralogs.
Type: combinatorial genetics / survival assay
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: Whether the mature amidated NLP-29 peptides themselves directly kill or inhibit microbes, and by what mechanism (membrane permeabilization, DNA binding as reported for the paralog NLP-31, or another target), has not been demonstrated. Every C. elegans study uses nlp-29 as an induced-expression readout, and the in-vivo antifungal evidence comes from overexpression of the whole nlp-29 cluster rather than a purified-peptide killing assay for NLP-29.
OPEN BIOLOGYONTOLOGY MF_DARK
What is known: nlp-29 is a bona fide secreted AMP-family gene, strongly induced in the epidermis by fungal/bacterial infection and wounding, and overexpression of the nlp-29 cluster increases resistance to D. coniospora. Its one biochemically demonstrated molecular activity is as a ligand/agonist of the neuronal GPCR NPR-12, not a microbicidal activity.
Significance: This is why nlp-29 carries no molecular-function annotation for antimicrobial activity: such activity is both unproven for NLP-29 itself and lacks an adequate GO molecular-function term. Closing it would define the effector arm of the flagship C. elegans epidermal immune pathway.
What would resolve it: In vitro microbicidal, membrane-permeabilization and nucleic-acid-binding assays with the individual synthetic mature NLP-29 peptides against D. coniospora and S. marcescens, plus structural characterization.
Provenance (the field's own admissions):
Proposed term (ontology gap):
Gap: The specific contribution of nlp-29 alone to pathogen resistance and survival is undetermined: the nlp-29(tm1931) null shows no marked change in resistance to D. coniospora, consistent with functional redundancy within the nlp-27 to nlp-34 cluster, so single-gene loss-of-function has not established necessity.
OPEN BIOLOGY RESIDUAL_SUBGAP
What is known: Loss of upstream regulators (e.g. tir-1, pmk-1, sta-2) abolishes nlp-29 induction and reduces antifungal resistance, and cluster overexpression increases resistance; but these manipulate the signaling pathway or the whole AMP cluster, not nlp-29 individually.
Significance: Determines whether nlp-29 is an individually important effector or a redundant member of a buffered AMP battery, which is central to interpreting the widely used Pnlp-29 immune reporter.
What would resolve it: Higher-order combinatorial deletions across the cluster and quantitative survival assays of precise single and compound nlp mutants under D. coniospora and S. marcescens challenge.
Provenance (the field's own admissions):
Gap: It is unknown which of the several distinct amidated peptides cleaved from the NLP-29 precursor mediate antimicrobial activity versus which engage NPR-12, and the predicted proprotein processing and C-terminal amidation have not been directly demonstrated for NLP-29.
OPEN BIOLOGY MF_DARK
What is known: The precursor sequence, signal peptide, predicted cleavage on paired basic residues and the Tyr/Trp-amidation motifs are annotated by UniProt sequence analysis; synthetic full-length NLP-29 peptide activates NPR-12 and induces dendrite degeneration, whereas the related NLP-31 does not.
Significance: Distinguishing effector peptides from signaling peptides within a single precursor would clarify whether the antimicrobial and neuroimmune functions of NLP-29 are molecularly separable.
What would resolve it: Mass-spectrometric identification of the endogenous mature peptides and structure-activity assays of individual synthetic peptides against microbes and against NPR-12.
Provenance (the field's own admissions):
Gap: Whether NLP-29's antimicrobial action is receptor-mediated or a direct physicochemical effect on microbes is unresolved. NPR-12 is the only demonstrated receptor and mediates host neuroimmune signaling (sleep, dendrite degeneration), not microbial killing, so any receptor or target underlying an effector function is unidentified.
OPEN BIOLOGY MF_DARK
What is known: NPR-12 is a validated NLP-29 receptor for cross-tissue host signaling and is expressed in neurons, not microbes; no microbial or host target for a direct antimicrobial effect is known.
Significance: Clarifies whether the same peptide uses distinct molecular mechanisms for host signaling versus pathogen defense.
What would resolve it: Target-identification (pulldown/photo-crosslinking) with labeled NLP-29 peptides on microbial and host membranes, and testing whether antimicrobial protection requires any host receptor.
Provenance (the field's own admissions):
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Gene: nlp-29 (B0213.4) | UniProt: O44664 | Organism: Caenorhabditis elegans
NLP-29 (Neuropeptide-Like Protein 29) is an antimicrobial peptide (AMP) encoded by the nlp-29 gene on chromosome V of C. elegans. It belongs to the YARP (YGGW-amide related peptide) family and is synthesized as a precursor protein that is proteolytically processed to yield multiple mature amidated peptides, including QWGYGGY-amide, GYGGYGGY-amide, GMYGGY-amide, and GMYGGW-amide. The NLP-29 precursor contains an N-terminal signal peptide characteristic of secreted proteins (dierking2016antimicrobialeffectorsin pages 4-5). The mature NLP-29 peptide is 51 amino acids long with the sequence QWGYGGYGRGYGGYGGYGRGMYGGYGRGMYGGYGRGMYGGYGRGMYGGWGK, which is notably rich in glycine, tyrosine, and aromatic residues (e2018anantimicrobialpeptide pages 17-19). These structural features β a basic charge, glycine/tyrosine-rich composition, and C-terminal amidation β are hallmarks of antimicrobial peptides in the NLP class (dierking2016antimicrobialeffectorsin pages 4-5).
The primary function of NLP-29 is as an antimicrobial effector molecule in the epidermal innate immune response of C. elegans. NLP-29 is one of six AMP genes (nlp-27, nlp-28, nlp-29, nlp-30, nlp-31, and nlp-34) in the "nlp-29 cluster," which spans less than 12 kb on chromosome V (pujol2008antifungalinnateimmunity pages 2-3, dierking2016antimicrobialeffectorsin pages 4-5). Expression of these genes is strongly upregulated in the epidermis upon infection by the natural fungal pathogen Drechmeria coniospora (pujol2008antifungalinnateimmunity pages 10-11, pujol2012theoriginand pages 1-2). Transgenic worms carrying a cosmid that spans the nlp-29 locus demonstrated significantly increased resistance to D. coniospora infection compared to non-transgenic siblings (p < 0.001 survival difference over 6 days), establishing that the nlp-29 cluster enhances pathogen resistance in vivo (pujol2008antifungalinnateimmunity pages 10-11). Overexpression of nlp AMPs more broadly also leads to increased resistance to fungal infection (pujol2012theoriginand pages 1-2).
While direct antimicrobial assays on NLP-29 itself are limited, the closely related cluster member NLP-31 has been extensively characterized. Synthetic NLP-31 at 200 Β΅M completely inhibits hyphal growth of D. coniospora in vitro, confirming direct antifungal activity (dierking2016antimicrobialeffectorsin pages 3-4). NLP-31 also demonstrates antibacterial activity against both Gram-positive (Micrococcus luteus) and Gram-negative (E. coli, Burkholderia pseudomallei) bacteria in a dose-dependent manner (lim2016nematodepeptideswith pages 8-9). Mechanistically, NLP-31 acts through a non-membranolytic mechanism: rather than disrupting cell membranes, the peptide binds DNA and interferes with bacterial DNA synthesis machinery, as evidenced by gel retardation assays and induction of cellular filamentation in treated bacteria (lim2016nematodepeptideswith pages 5-7, lim2016nematodepeptideswith pages 9-11). This DNA-binding activity is consistent with the glycine/tyrosine-rich composition shared across the nlp-29 cluster peptides (lim2016nematodepeptideswith pages 9-11).
NLP-29 is predominantly expressed in the C. elegans epidermis, specifically in the hyp7 syncytium, which comprises nearly all of the epidermal surface (pujol2008distinctinnateimmune pages 3-4, pujol2008distinctinnateimmune pages 2-3). This localization is significant because the epidermis is the first barrier tissue encountered by fungal pathogens such as D. coniospora, which infect through the cuticle (dierking2016antimicrobialeffectorsin pages 4-5). Using a pnlp-29::GFP fluorescent reporter construct, researchers have demonstrated that nlp-29 expression is induced in epidermal cells after both infection and wounding (pujol2008antifungalinnateimmunity pages 6-7, pujol2008distinctinnateimmune pages 2-3). After epidermal injury, GFP fluorescence appears within approximately 1 hour and is sustained for several hours before declining (pujol2008distinctinnateimmune pages 2-3).
The presence of a signal peptide at the N-terminus indicates that NLP-29 is secreted from epidermal cells (dierking2016antimicrobialeffectorsin pages 4-5). Experimental evidence strongly supports its secreted nature: epidermally-produced NLP-29 acts non-cell-autonomously on distant PVD sensory neurons via the receptor NPR-12, and on locomotion-controlling interneurons in sleep circuits (e2018anantimicrobialpeptide pages 5-6, e2018anantimicrobialpeptide pages 7-8, sinner2021innateimmunitypromotes pages 1-4). Epidermis-specific expression using the col-19 promoter is sufficient to rescue nlp-29 mutant phenotypes, confirming that the epidermis is the functionally relevant tissue of origin (e2018anantimicrobialpeptide pages 5-6).
The regulation of nlp-29 involves a well-characterized signaling cascade that is among the best-studied innate immune pathways in C. elegans. Multiple stimuli β fungal infection, sterile wounding, and osmotic stress β induce nlp-29 through overlapping but distinct signaling branches.
Upon fungal infection or epidermal damage, the endogenous ligand 4-hydroxyphenyllactic acid (HPLA) is detected by DCAR-1, a G protein-coupled receptor (GPCR) expressed in the epidermis (dierking2016antimicrobialeffectorsin pages 4-5, taffoni2015mechanismsofinnate pages 5-6, zugasti2016aquantitativegenomewide pages 5-6). DCAR-1 activates the GΞ± protein GPA-12 and the scaffolding protein RACK-1, which in turn activate TPA-1, a PKCΞ΄ family protein kinase (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12). TPA-1 signals downstream to the TIR-1 adaptor protein (an ortholog of mammalian SARM), which activates the core p38 MAPK cascade consisting of NSY-1 (MAP3K) β SEK-1 (MAP2K) β PMK-1 (p38 MAPK) (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12, pujol2008antifungalinnateimmunity pages 3-5, pujol2008distinctinnateimmune pages 3-4). This pathway acts cell-autonomously within the epidermis; expression of sek-1 specifically in the epidermis is sufficient to restore nlp-29::GFP expression in sek-1 mutants (pujol2008distinctinnateimmune pages 4-5).
At the transcriptional level, the STAT-like transcription factor STA-2 is a critical effector downstream of PMK-1 and is a potential direct substrate of activated PMK-1 (kim2018signalinginthe pages 9-12). STA-2 inactivation completely abolishes infection-induced nlp-29 and cnc-2 upregulation (zhang2015structuraldamagein pages 6-7). The GATA transcription factor ELT-3 is also required for nlp transcription (taffoni2015mechanismsofinnate pages 5-6). Interestingly, STA-2 has been found to localize to apical membrane attachment structures (hemidesmosomes/CeHDs) in the epidermis, where it may serve as a sensor of structural integrity; upon structural damage, STA-2 is released to activate AMP gene expression (zhang2015structuraldamagein pages 6-7).
The Tribbles-like kinase NIPI-3 is required specifically for infection-induced nlp-29 expression but is dispensable for wound-induced expression, thereby distinguishing infection from damage responses (pujol2008distinctinnateimmune pages 4-5, pujol2008distinctinnateimmune pages 3-4). NIPI-3 acts upstream of both TPA-1 and the p38 MAPK pathway specifically upon fungal infection (taffoni2015mechanismsofinnate pages 5-6). Mutants in nipi-3 show reduced resistance to fungal infection and shortened lifespan (pujol2008distinctinnateimmune pages 4-5).
A parallel regulatory input comes from the neuronally-derived TGF-Ξ² ligand DBL-1 signaling through a noncanonical pathway. This pathway, described by Zugasti and Ewbank (2009) in Nature Immunology, primarily regulates the cnc (caenacin) class of AMP genes rather than the nlp-29 cluster itself. Notably, dbl-1 is not required for upregulation of nlp-29 cluster genes following D. coniospora infection (zugasti2009neuroimmuneregulationof pages 5-11). However, both the p38 MAPK pathway and the DBL-1/TGF-Ξ²-SMAD signaling pathway contribute to sleep-promoting functions downstream of AMP expression (sinner2021innateimmunitypromotes pages 8-9). The TGF-Ξ² pathway component SMA-6 must function in the epidermis for proper AMP gene regulation (zugasti2009neuroimmuneregulationof pages 5-11, taffoni2015mechanismsofinnate pages 5-6).
Osmotic stress also induces nlp-29 expression, but this response is independent of the p38 MAPK cascade (PMK-1) (pujol2008antifungalinnateimmunity pages 10-11). Importantly, ELT-3 is still required for osmotic-stress-induced nlp-29 expression, indicating that the osmotic and infection pathways converge at the level of transcription factors even though they diverge upstream (taffoni2015mechanismsofinnate pages 5-6).
The following table summarizes the components of the signaling pathway regulating nlp-29:
| Component | Type/Function | Role in nlp-29 regulation | Specificity (infection/wounding/osmotic stress) |
|---|---|---|---|
| HPLA | Endogenous damage-associated ligand (4-hydroxyphenyllactic acid) | Activates the upstream receptor DCAR-1 to trigger epidermal innate immune signaling leading to AMP induction including nlp-29 (dierking2016antimicrobialeffectorsin pages 4-5, taffoni2015mechanismsofinnate pages 5-6) | Infection and wounding; not established as the osmotic-stress signal for nlp-29 (dierking2016antimicrobialeffectorsin pages 4-5, taffoni2015mechanismsofinnate pages 5-6) |
| DCAR-1 | GPCR receptor | Functions at the top of the epidermal AMP pathway; acts upstream of GPA-12/RACK-1 and TPA-1 to induce nlp-29 after fungal infection or epidermal injury (taffoni2015mechanismsofinnate pages 5-6, zugasti2016aquantitativegenomewide pages 5-6) | Infection and wounding; not implicated in the p38-independent osmotic-stress branch (taffoni2015mechanismsofinnate pages 5-6, zugasti2016aquantitativegenomewide pages 5-6) |
| GPA-12 | GΞ± protein | Acts downstream of DCAR-1 and upstream of TPA-1/TIR-1-p38 MAPK; epidermal activation is sufficient to promote nlp-29 expression (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12) | Infection and wounding; no evidence here for osmotic-stress-specific control (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12) |
| RACK-1 | Scaffolding/signaling adaptor | Acts with/near GPA-12 upstream of TPA-1 in the epidermal signaling cascade that induces nlp AMP genes including nlp-29 (taffoni2015mechanismsofinnate pages 5-6) | Infection and wounding; osmotic-stress role not defined in the cited evidence (taffoni2015mechanismsofinnate pages 5-6) |
| TPA-1 | PKCΞ΄ family protein kinase | Key upstream kinase required to relay GPCR/G protein signaling to the TIR-1βNSY-1βSEK-1βPMK-1 cascade for nlp-29 induction (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12) | Infection and wounding; not part of the known p38-independent osmotic branch (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12) |
| NIPI-3 | Tribbles-like kinase/regulator | Infection-specific regulator acting upstream of both TPA-1 and the p38 MAPK cassette; required for full nlp-29 induction after fungal infection but dispensable for wound-induced expression (taffoni2015mechanismsofinnate pages 5-6, pujol2008distinctinnateimmune pages 4-5, pujol2008distinctinnateimmune pages 3-4) | Infection-specific; not required for wounding response; no osmotic-stress role established here (taffoni2015mechanismsofinnate pages 5-6, pujol2008distinctinnateimmune pages 4-5, pujol2008distinctinnateimmune pages 3-4) |
| TIR-1 | TIR-domain adaptor protein | Adaptor upstream of NSY-1/SEK-1/PMK-1; essential for epidermal innate immune induction of nlp-29 after infection and wounding (kim2018signalinginthe pages 9-12, pujol2008antifungalinnateimmunity pages 3-5, pujol2008distinctinnateimmune pages 3-4) | Infection and wounding; not required for the p38-independent osmotic response (by inference from pathway separation) (kim2018signalinginthe pages 9-12, pujol2008antifungalinnateimmunity pages 3-5) |
| NSY-1 | MAP3K | MAP kinase kinase kinase in the core p38 cascade downstream of TIR-1; required for nlp-29 induction (taffoni2015mechanismsofinnate pages 5-6, pujol2008antifungalinnateimmunity pages 3-5) | Infection and wounding; not part of the osmotic-stress branch (taffoni2015mechanismsofinnate pages 5-6, pujol2008antifungalinnateimmunity pages 3-5) |
| SEK-1 | MAP2K | MAP kinase kinase in the p38 pathway; acts cell-autonomously in the epidermis and is sufficient there to restore nlp-29 reporter induction in mutants (pujol2008distinctinnateimmune pages 4-5, pujol2008distinctinnateimmune pages 3-4) | Infection and wounding; no evidence for osmotic-stress dependence (pujol2008distinctinnateimmune pages 4-5, pujol2008distinctinnateimmune pages 3-4) |
| PMK-1 | p38 MAPK | Terminal MAPK of the core innate immune cascade; required for infection- and wound-induced nlp-29 expression, and high constitutive nlp-29 in epidermal damage backgrounds is largely PMK-1-dependent (pujol2008antifungalinnateimmunity pages 10-11, kim2018signalinginthe pages 9-12, pujol2008antifungalinnateimmunity pages 3-5) | Infection and wounding; notably dispensable for osmotic-stress-induced nlp-29 expression (pujol2008antifungalinnateimmunity pages 10-11, kim2018signalinginthe pages 9-12) |
| STA-2 | STAT-like transcription factor | Essential transcriptional effector downstream of/with PMK-1 for nlp-29 expression; also mediates AMP induction after structural epidermal damage and can be regulated at apical attachment structures (taffoni2015mechanismsofinnate pages 5-6, kim2018signalinginthe pages 9-12, zhang2015structuraldamagein pages 6-7) | Infection and wounding/structural damage; no specific osmotic-stress role established in the cited evidence (taffoni2015mechanismsofinnate pages 5-6, zhang2015structuraldamagein pages 6-7) |
| ELT-3 | GATA transcription factor | Required transcription factor for nlp AMP transcription, including nlp-29; notably shared between fungus-induced and osmotic-stress-induced regulation, even though the latter is PMK-1-independent (taffoni2015mechanismsofinnate pages 5-6, pujol2008antifungalinnateimmunity pages 10-11) | Infection and osmotic stress; likely contributes to wound-responsive epidermal AMP transcription as a shared epidermal regulator (taffoni2015mechanismsofinnate pages 5-6, pujol2008antifungalinnateimmunity pages 10-11) |
Table: This table summarizes the best-supported epidermal signaling cascade controlling nlp-29 expression in C. elegans, from upstream ligand/receptor inputs to downstream transcription factors. It also distinguishes which components are specific to fungal infection or wounding versus the separate osmotic-stress branch.
Beyond its direct antimicrobial function, NLP-29 has emerged as an important neuroimmune signaling molecule with at least two well-characterized downstream functions:
E et al. (2018) demonstrated in Neuron that epidermally secreted NLP-29 promotes age- and infection-associated degeneration of PVD sensory neuron dendrites. NLP-29 acts through the neuropeptide receptor NPR-12, which is expressed on PVD neurons (e2018anantimicrobialpeptide pages 10-11). The NLP-29βNPR-12 interaction activates autophagy pathways cell-autonomously in neurons, leading to dendritic morphology changes (e2018anantimicrobialpeptide pages 10-11). Epidermis-specific knockdown of nlp-29 delayed PVD dendrite degeneration, while epidermal overexpression using the col-19 promoter induced early-onset degeneration (e2018anantimicrobialpeptide pages 5-6, e2018anantimicrobialpeptide pages 7-8). This finding reveals that the progressive upregulation of nlp-29 during aging contributes to neuronal aging phenotypes.
Sinner et al. (2021) showed that NLP-29 functions as a somnogen β a sleep-promoting molecule. Upon immune activation, wounding, or during developmental lethargus (larval sleep), epidermally-produced AMPs including NLP-29 are released and signal through NPR-12 on locomotion-controlling interneurons (PVC, RIM) that synapse onto the RIS sleep-active neuron (sinner2021innateimmunitypromotes pages 1-4, sinner2021innateimmunitypromotes pages 10-11). NLP-29 overexpression increased movement quiescence to 93.3%, and this effect was suppressed by approximately 50% when NPR-12 was knocked out (sinner2021innateimmunitypromotes pages 10-11). The sleep-promoting function requires EGFR signaling in neurons (sinner2021innateimmunitypromotes pages 10-11). Animals lacking multiple nlp and cnc AMP genes showed both impaired sleep and significantly reduced survival after injury, indicating that AMP-mediated sleep promotion is adaptive (sinner2021innateimmunitypromotes pages 11-12). NLP-29 expression correlates with sleep duration, and the NAS-38 metalloprotease promotes sleep by increasing epidermal AMP expression including nlp-29 through both the p38 MAPK and DBL-1/TGF-Ξ²-SMAD pathways (sinner2021innateimmunitypromotes pages 8-9, sinner2021innateimmunitypromotes pages 5-8).
The following table summarizes the major biological functions of NLP-29:
| Function | Description | Key Evidence | References |
|---|---|---|---|
| Antimicrobial defense | NLP-29 is an epidermally induced antimicrobial peptide (AMP) in the nlp-29 cluster that contributes to antifungal defense, especially against the natural pathogen Drechmeria coniospora. The primary function supported by genetics is host defense after epidermal infection. | The nlp-29 cluster is strongly induced by fungal infection; transgenic worms carrying a cosmid spanning the nlp-29 locus showed significantly increased resistance to D. coniospora infection in vivo. Reviews of nematode AMPs classify NLP-29 as a bona fide AMP in epidermal innate immunity. | (pujol2008antifungalinnateimmunity pages 10-11, pujol2012theoriginand pages 1-2, dierking2016antimicrobialeffectorsin pages 4-5) |
| Dendrite degeneration regulation | Beyond host defense, secreted epidermal NLP-29 functions as a neuroimmune signal that promotes age- and infection-associated degeneration of PVD sensory dendrites by acting on the neuronal receptor NPR-12. | Epidermis-specific knockdown of nlp-29 delayed PVD dendrite degeneration, whereas epidermal expression restored the phenotype. Exogenous or overexpressed NLP-29 induced degeneration through NPR-12 and downstream autophagy-related mechanisms in neurons. | (e2018anantimicrobialpeptide pages 10-11, e2018anantimicrobialpeptide pages 5-6, e2018anantimicrobialpeptide pages 7-8) |
| Sleep promotion | NLP-29 also acts as a somnogenic immune signal: epidermally produced NLP-29 promotes movement quiescence/sleep by signaling through NPR-12 in neurons upstream of the RIS sleep neuron. | Overexpression of nlp-29 increased movement quiescence, and loss of npr-12 substantially suppressed this effect. Immune activation and wounding induce AMP expression, including nlp-29, and animals lacking AMP genes show reduced sleep and reduced survival after injury. | (sinner2021innateimmunitypromotes pages 8-9, sinner2021innateimmunitypromotes pages 11-12, sinner2021innateimmunitypromotes pages 9-10, sinner2021innateimmunitypromotes pages 10-11) |
| Wound response | nlp-29 is rapidly induced in the epidermis after sterile epidermal injury, making it part of the acute wound-response program as well as the infection response. | A pnlp-29::GFP reporter is induced within about 1 hour after epidermal wounding and remains elevated for several hours. The wound-induced response occurs in epidermal cells/hyp7 and depends on the epidermal p38 MAPK immune pathway. | (pujol2008antifungalinnateimmunity pages 6-7, pujol2008distinctinnateimmune pages 3-4, pujol2008distinctinnateimmune pages 2-3) |
| Osmotic stress response | nlp-29 is also activated by osmotic stress and epidermal damage states, showing that it is a broader epidermal stress-response effector, not only an infection marker. This osmotic-stress induction is largely independent of the canonical PMK-1/p38 infection pathway but still requires epidermal transcriptional control. | The nlp-29 cluster is induced under high osmolarity conditions; this induction differs from fungus-induced expression because it does not require the p38 MAPK cascade, while shared epidermal regulators such as ELT-3 remain important. nlp-28 and nlp-29 are specifically highlighted as strongly osmotic-stress inducible members of the cluster. | (pujol2012theoriginand pages 1-2, taffoni2015mechanismsofinnate pages 5-6, pujol2008antifungalinnateimmunity pages 7-9) |
Table: This table summarizes the major experimentally supported biological functions of NLP-29 in C. elegans, spanning innate immunity, neuroimmune signaling, wound responses, and stress responses. It is useful for distinguishing NLP-29's primary antimicrobial role from its later-discovered signaling functions.
The nlp-29 gene cluster has undergone rapid evolutionary diversification driven by natural selection from pathogen pressure. In C. elegans, the ancestral nlp-27 gene expanded to five genes (nlp-28 through nlp-31), while in C. briggsae the ancestral nlp-34 expanded to three genes (pujol2008antifungalinnateimmunity pages 7-9). Comparative analysis across C. elegans, C. briggsae, C. remanei, and C. japonica reveals species-specific patterns of gene duplication and loss, with C. japonica having 10 predicted paralogs from a single C. remanei gene (pujol2012theoriginand pages 1-2). Phylogenetic analysis using dN/dS ratios demonstrates that non-synonymous changes are favored over synonymous changes in several branches, indicative of positive Darwinian selection (pujol2008antifungalinnateimmunity pages 10-10). The nlp-28 and nlp-29 genes are C. elegans-specific and show distinctive regulation, being upregulated by infection, wounding, and osmotic stress (pujol2008antifungalinnateimmunity pages 7-9). This rapid evolutionary diversification, driven by intra-genomic gene duplication and adaptive sequence evolution, suggests that selective pressure from pathogens has shaped the AMP repertoire (pujol2008antifungalinnateimmunity pages 1-2).
NLP-29 is a multifunctional glycine/tyrosine-rich antimicrobial peptide produced in the C. elegans epidermis. Its primary function is as an effector of epidermal innate immunity against fungal pathogens, where it contributes to host defense as part of a cluster of co-regulated AMPs. Expression of nlp-29 is controlled by a well-defined signaling cascade: the GPCR DCAR-1 detects the damage-associated ligand HPLA, activating GPA-12/RACK-1 β TPA-1 β TIR-1 β NSY-1 β SEK-1 β PMK-1 (p38 MAPK), culminating in STA-2 and ELT-3-mediated transcription in the epidermis. The infection-specific kinase NIPI-3 provides an additional layer of specificity. Beyond antimicrobial defense, secreted NLP-29 acts as a long-range neuroimmune signal through the NPR-12 receptor, promoting dendrite degeneration during aging and sleep after immune activation or injury. The nlp-29 gene cluster has undergone rapid evolutionary diversification through gene duplication and positive selection across Caenorhabditis species, reflecting ongoing selective pressure from fungal pathogens. These findings position NLP-29 at the intersection of innate immunity, neuroimmune communication, and organismal homeostasis in C. elegans.
References
(dierking2016antimicrobialeffectorsin pages 4-5): Katja Dierking, Wentao Yang, and Hinrich Schulenburg. Antimicrobial effectors in the nematode caenorhabditis elegans: an outgroup to the arthropoda. Philosophical Transactions of the Royal Society B: Biological Sciences, 371:20150299, May 2016. URL: https://doi.org/10.1098/rstb.2015.0299, doi:10.1098/rstb.2015.0299. This article has 107 citations and is from a domain leading peer-reviewed journal.
(e2018anantimicrobialpeptide pages 17-19): Lezi E, Ting Zhou, Sehwon Koh, Marian Chuang, Ruchira Sharma, Nathalie Pujol, Andrew D. Chisholm, Cagla Eroglu, Hiroaki Matsunami, and Dong Yan. An antimicrobial peptide and its neuronal receptor regulate dendrite degeneration in aging and infection. Neuron, 97:125-138.e5, Jan 2018. URL: https://doi.org/10.1016/j.neuron.2017.12.001, doi:10.1016/j.neuron.2017.12.001. This article has 112 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 2-3): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 10-11): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(pujol2012theoriginand pages 1-2): Nathalie Pujol, Paul A. Davis, and Jonathan J. Ewbank. The origin and function of anti-fungal peptides in c. elegans: open questions. Frontiers in Immunology, Aug 2012. URL: https://doi.org/10.3389/fimmu.2012.00237, doi:10.3389/fimmu.2012.00237. This article has 38 citations and is from a peer-reviewed journal.
(dierking2016antimicrobialeffectorsin pages 3-4): Katja Dierking, Wentao Yang, and Hinrich Schulenburg. Antimicrobial effectors in the nematode caenorhabditis elegans: an outgroup to the arthropoda. Philosophical Transactions of the Royal Society B: Biological Sciences, 371:20150299, May 2016. URL: https://doi.org/10.1098/rstb.2015.0299, doi:10.1098/rstb.2015.0299. This article has 107 citations and is from a domain leading peer-reviewed journal.
(lim2016nematodepeptideswith pages 8-9): Mei-Perng Lim, Mohd Firdaus-Raih, and Sheila Nathan. Nematode peptides with host-directed anti-inflammatory activity rescue caenorhabditis elegans from a burkholderia pseudomallei infection. Frontiers in Microbiology, Sep 2016. URL: https://doi.org/10.3389/fmicb.2016.01436, doi:10.3389/fmicb.2016.01436. This article has 20 citations and is from a peer-reviewed journal.
(lim2016nematodepeptideswith pages 5-7): Mei-Perng Lim, Mohd Firdaus-Raih, and Sheila Nathan. Nematode peptides with host-directed anti-inflammatory activity rescue caenorhabditis elegans from a burkholderia pseudomallei infection. Frontiers in Microbiology, Sep 2016. URL: https://doi.org/10.3389/fmicb.2016.01436, doi:10.3389/fmicb.2016.01436. This article has 20 citations and is from a peer-reviewed journal.
(lim2016nematodepeptideswith pages 9-11): Mei-Perng Lim, Mohd Firdaus-Raih, and Sheila Nathan. Nematode peptides with host-directed anti-inflammatory activity rescue caenorhabditis elegans from a burkholderia pseudomallei infection. Frontiers in Microbiology, Sep 2016. URL: https://doi.org/10.3389/fmicb.2016.01436, doi:10.3389/fmicb.2016.01436. This article has 20 citations and is from a peer-reviewed journal.
(pujol2008distinctinnateimmune pages 3-4): Nathalie Pujol, Sophie Cypowyj, Katja Ziegler, Anne Millet, Aline Astrain, Alexandr Goncharov, Yishi Jin, Andrew D. Chisholm, and Jonathan J. Ewbank. Distinct innate immune responses to infection and wounding in the c. elegans epidermis. Current Biology, 18:481-489, Apr 2008. URL: https://doi.org/10.1016/j.cub.2008.02.079, doi:10.1016/j.cub.2008.02.079. This article has 388 citations and is from a highest quality peer-reviewed journal.
(pujol2008distinctinnateimmune pages 2-3): Nathalie Pujol, Sophie Cypowyj, Katja Ziegler, Anne Millet, Aline Astrain, Alexandr Goncharov, Yishi Jin, Andrew D. Chisholm, and Jonathan J. Ewbank. Distinct innate immune responses to infection and wounding in the c. elegans epidermis. Current Biology, 18:481-489, Apr 2008. URL: https://doi.org/10.1016/j.cub.2008.02.079, doi:10.1016/j.cub.2008.02.079. This article has 388 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 6-7): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(e2018anantimicrobialpeptide pages 5-6): Lezi E, Ting Zhou, Sehwon Koh, Marian Chuang, Ruchira Sharma, Nathalie Pujol, Andrew D. Chisholm, Cagla Eroglu, Hiroaki Matsunami, and Dong Yan. An antimicrobial peptide and its neuronal receptor regulate dendrite degeneration in aging and infection. Neuron, 97:125-138.e5, Jan 2018. URL: https://doi.org/10.1016/j.neuron.2017.12.001, doi:10.1016/j.neuron.2017.12.001. This article has 112 citations and is from a highest quality peer-reviewed journal.
(e2018anantimicrobialpeptide pages 7-8): Lezi E, Ting Zhou, Sehwon Koh, Marian Chuang, Ruchira Sharma, Nathalie Pujol, Andrew D. Chisholm, Cagla Eroglu, Hiroaki Matsunami, and Dong Yan. An antimicrobial peptide and its neuronal receptor regulate dendrite degeneration in aging and infection. Neuron, 97:125-138.e5, Jan 2018. URL: https://doi.org/10.1016/j.neuron.2017.12.001, doi:10.1016/j.neuron.2017.12.001. This article has 112 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 1-4): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(taffoni2015mechanismsofinnate pages 5-6): Clara Taffoni and Nathalie Pujol. Mechanisms of innate immunity in c. elegans epidermis. Tissue Barriers, 3:e1078432, Oct 2015. URL: https://doi.org/10.1080/21688370.2015.1078432, doi:10.1080/21688370.2015.1078432. This article has 75 citations and is from a peer-reviewed journal.
(zugasti2016aquantitativegenomewide pages 5-6): Olivier Zugasti, Nishant Thakur, JΓ©rΓ΄me Belougne, Barbara Squiban, C. LΓ©opold Kurz, Julien SoulΓ©, Shizue Omi, Laurent Tichit, Nathalie Pujol, and Jonathan J. Ewbank. A quantitative genome-wide rnai screen in c. elegans for antifungal innate immunity genes. BMC Biology, Apr 2016. URL: https://doi.org/10.1186/s12915-016-0256-3, doi:10.1186/s12915-016-0256-3. This article has 69 citations and is from a domain leading peer-reviewed journal.
(kim2018signalinginthe pages 9-12): Dennis H. Kim and J. Ewbank. Signaling in the innate immune response. WormBook : the online review of C. elegans biology, 2018:1-35, Aug 2018. URL: https://doi.org/10.1895/wormbook.1.83.2, doi:10.1895/wormbook.1.83.2. This article has 152 citations.
(pujol2008antifungalinnateimmunity pages 3-5): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(pujol2008distinctinnateimmune pages 4-5): Nathalie Pujol, Sophie Cypowyj, Katja Ziegler, Anne Millet, Aline Astrain, Alexandr Goncharov, Yishi Jin, Andrew D. Chisholm, and Jonathan J. Ewbank. Distinct innate immune responses to infection and wounding in the c. elegans epidermis. Current Biology, 18:481-489, Apr 2008. URL: https://doi.org/10.1016/j.cub.2008.02.079, doi:10.1016/j.cub.2008.02.079. This article has 388 citations and is from a highest quality peer-reviewed journal.
(zhang2015structuraldamagein pages 6-7): Yun Zhang, Wenna Li, Linfeng Li, Yuanbao Li, Rong Fu, Yi Zhu, Jie Li, Yanfeng Zhou, Sidong Xiong, and Huimin Zhang. Structural damage in the c. elegans epidermis causes release of sta-2 and induction of an innate immune response. Immunity, 42 2:309-320, Feb 2015. URL: https://doi.org/10.1016/j.immuni.2015.01.014, doi:10.1016/j.immuni.2015.01.014. This article has 86 citations and is from a highest quality peer-reviewed journal.
(zugasti2009neuroimmuneregulationof pages 5-11): Olivier Zugasti and Jonathan J Ewbank. Neuroimmune regulation of antimicrobial peptide expression by a noncanonical tgf-Ξ² signaling pathway in caenorhabditis elegans epidermis. Nature Immunology, 10:249-256, Mar 2009. URL: https://doi.org/10.1038/ni.1700, doi:10.1038/ni.1700. This article has 260 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 8-9): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(e2018anantimicrobialpeptide pages 10-11): Lezi E, Ting Zhou, Sehwon Koh, Marian Chuang, Ruchira Sharma, Nathalie Pujol, Andrew D. Chisholm, Cagla Eroglu, Hiroaki Matsunami, and Dong Yan. An antimicrobial peptide and its neuronal receptor regulate dendrite degeneration in aging and infection. Neuron, 97:125-138.e5, Jan 2018. URL: https://doi.org/10.1016/j.neuron.2017.12.001, doi:10.1016/j.neuron.2017.12.001. This article has 112 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 10-11): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 11-12): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 5-8): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(sinner2021innateimmunitypromotes pages 9-10): Marina P. Sinner, Florentin Masurat, Jonathan J. Ewbank, Nathalie Pujol, and Henrik Bringmann. Innate immunity promotes sleep through epidermal antimicrobial peptides. Feb 2021. URL: https://doi.org/10.1016/j.cub.2020.10.076, doi:10.1016/j.cub.2020.10.076. This article has 72 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 7-9): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 10-10): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
(pujol2008antifungalinnateimmunity pages 1-2): Nathalie Pujol, Olivier Zugasti, Daniel Wong, Carole Couillault, C. LΓ©opold Kurz, Hinrich Schulenburg, and Jonathan J. Ewbank. Anti-fungal innate immunity in c. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathogens, 4:e1000105, Jul 2008. URL: https://doi.org/10.1371/journal.ppat.1000105, doi:10.1371/journal.ppat.1000105. This article has 300 citations and is from a highest quality peer-reviewed journal.
UniProt: O44664 (NLP29_CAEEL). WormBase: WBGene00003767 / B0213.4. Chromosome V.
Gene: neuropeptide-like protein 29. Part of the nlp-29 cluster (nlp-27..nlp-34) of the
YARP (YGGW-amide related peptide) family. Flagship project: CAEEL_SURVEILLANCE_IMMUNITY.
This is a small, secreted, infection/wounding-inducible antimicrobial-peptide (AMP) precursor.
Notes below separate what is KNOWN (with provenance) from what is NOT known (the deliverable
for a "dark" effector peptide).
nlp-29 is an infection- and damage-inducible epidermal (hypodermal) AMP gene. It is the
canonical transcriptional readout of the C. elegans epidermal antifungal immune pathway.
dozen-AMP module PMID:33259791. (UniProt records this as
"Transcriptionally regulated by the transcription factor sta-2".)
Beyond being an effector, secreted NLP-29 peptide has a demonstrated cross-tissue signaling
function: after wounding/infection it promotes protective sleep.
Direct microbicidal activity & mechanism (MF-dark). Whether the mature amidated NLP-29
peptides themselves directly kill or inhibit microbes β and by what mechanism (membrane
permeabilization? specific target?) β is not established in the cached primary literature.
Every C. elegans study above uses nlp-29 as an induced-expression readout; the "antibacterial
against S. marcescens / antifungal against D. coniospora" statements in UniProt FUNCTION are
attributed to PMID:15048112/PMID:19380113, which demonstrate infection-dependent induction
and genetic requirement of the pathway, not a purified-peptide killing assay for NLP-29.
(The related family member NLP-31 has been the one more often tested biochemically in the
literature; NLP-29 itself is comparatively unassayed.) β BIOLOGY gap, MF_DARK.
NOTE: this is exactly why GO MF for nlp-29 is essentially only the family-predicted
"neuropeptide receptor binding"; there is no curated MF term capturing "antimicrobial peptide
activity".
In-vivo necessity of nlp-29 itself. Because nlp-29 sits in a redundant multigene AMP
cluster (nlp-27β34, plus the cnc caenacins), the phenotypic contribution of nlp-29 alone
(single-gene loss of function) to pathogen resistance/survival is not cleanly established in
the cached literature β most functional genetics manipulates upstream regulators or the whole
cluster. β BIOLOGY gap (redundancy).
Which mature peptide does what. The precursor yields β₯6 distinct amidated peptides; which
one(s) mediate antimicrobial activity vs which engage NPR-12 (the somnogen role) is unknown.
The processing itself (proprotein convertase, amidation) is predicted, not directly shown for
NLP-29. β BIOLOGY gap.
Receptor scope. NPR-12 is the only demonstrated receptor (sleep role, PMID:33259791).
Whether NLP-29 peptides have additional receptors/targets in the antimicrobial context, or act
receptor-independently as a microbicide, is unresolved. β BIOLOGY gap.
BP terms present in UniProt DR-GO but NOT in the GOA TSV (dropped after GO_REF:0000043 SPKW
retirement): defense response to bacterium (GO:0042742), defense response to fungus (GO:0050832),
killing of cells of another organism (GO:0031640), neuropeptide signaling pathway (GO:0007218) β
all IEA:UniProtKB-KW. These are biologically well-motivated but are not in existing_annotations
(only GOA annotations are reviewed here); captured instead in core_functions/knowledge_gaps.
The five core-pathway primary publications (11717458, 15048112, 18394898, 19380113, 33259791)
are cached ABSTRACT-ONLY (full_text_available: false). Reviews must therefore not REMOVE
experimental-style annotations on the basis of abstract wording alone; where the abstract does not
let me verify a specific claim I defer (ACCEPT/UNDECIDED) rather than overrule curators. THREE
publications are cached FULL-TEXT (full_text_available: true) and were used for verbatim provenance:
PMID:18636113 (Pujol 2008 PLoS Pathogens), PMID:29301098 (E 2018 Neuron), PMID:22870075 (Pujol 2012
Front Immunol, open-questions review).
just validate worm nlp-29, validate-references, and validate-terms all pass.id: O44664
gene_symbol: nlp-29
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:6239
label: Caenorhabditis elegans
description: >-
nlp-29 encodes a small (73-residue) secreted precursor of the YARP (YGGW-amide
related peptide) / NLP-CNC antimicrobial-peptide family in Caenorhabditis elegans.
The precursor carries an N-terminal signal peptide and is predicted to be processed
on pairs of basic residues into several short, glycine/tyrosine-rich, C-terminally
amidated peptides (QWGYGGY-amide, GYGGYGGY-amide and repeated GMYGGY/GMYGGW-amide
motifs). It is produced in the epidermis (hyp7 syncytium), where its transcription
is strongly and rapidly induced by infection with the natural fungal pathogen
Drechmeria coniospora, by bacterial infection (Serratia marcescens), by sterile
wounding, and by osmotic stress. Infection- and wound-induced expression requires an
epidermal signaling cassette (a GPCR/G-protein and PKCdelta/TPA-1 input converging on
the TIR-1/SARM-NSY-1-SEK-1-PMK-1 p38 MAPK cascade and the STAT-like factor STA-2 with
SNF-12 and the GATA factor ELT-3), whereas the osmotic response is largely p38-independent.
nlp-29 lies in a rapidly evolving, positively selected multigene cluster (nlp-27 to
nlp-34) of co-regulated antimicrobial peptides that contribute to antifungal host
defense. Beyond its role as a putative immune effector, secreted NLP-29 also acts as a
cross-tissue signaling ligand for the neuronal orphan G protein-coupled receptor NPR-12,
promoting protective sleep after wounding or infection and driving age- and
infection-associated dendrite degeneration of PVD and FLP sensory neurons.
references:
- id: GO_REF:0000015
title: Use of the ND evidence code for Gene Ontology (GO) terms
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping, accompanied by conservative changes to GO terms applied by
UniProt
findings: []
- id: PMID:11717458
title: Identification of neuropeptide-like protein gene families in Caenorhabditiselegans
and other species.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Bioinformatic identification of the 32 C. elegans nlp genes and the YGGWamide
family; this is the sequence-model (ISM) basis for the extracellular-region and
neuropeptide-receptor-binding annotations. PubMed-verified; note its general
"most nlp expression is in neurons" statement does NOT apply to epidermal nlp-29.
- id: PMID:15048112
title: TLR-independent control of innate immunity in Caenorhabditis elegans by the
TIR domain adaptor protein TIR-1, an ortholog of human SARM.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Identifies NLP-29/NLP-31 as infection-inducible AMPs differentially regulated by
fungal vs bacterial infection and controlled in part by tir-1. Establishes nlp-29 as
an immune-inducible effector; does not itself assay purified-peptide microbicidal
activity. Abstract-only in cache.
- id: PMID:18394898
title: Distinct innate immune responses to infection and wounding in the C. elegans
epidermis.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Shows nlp-29 is induced by sterile wounding as well as infection and that a p38 MAPK
cascade is required in the epidermis for both; NIPI-3 is required only for the
infection response. Abstract-only in cache.
- id: PMID:18636113
title: Anti-fungal innate immunity in C. elegans is enhanced by evolutionary diversification
of antimicrobial peptides.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Full-text verified. Key source for the in-vivo host-defense evidence and its limits:
the nlp-29(tm1931) single null shows no marked change in D. coniospora resistance
(redundancy), and the direct in-vivo antifungal effect is demonstrated only by
overexpression of the whole nlp-29 cluster. Anchors the in-vivo-necessity and
direct-microbicidal knowledge gaps.
- id: PMID:19380113
title: 'Antifungal innate immunity in C. elegans: PKCdelta links G protein signaling
and a conserved p38 MAPK cascade.'
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Forward screen for mutants failing to express nlp-29 after fungal infection; places
G-protein signaling and PKCdelta (tpa-1, with pkc-3) and nipi-3 upstream of the p38
cascade that drives nlp-29. Regulation of nlp-29, not its biochemical activity.
Abstract-only in cache.
- id: PMID:29301098
title: An Antimicrobial Peptide and Its Neuronal Receptor Regulate Dendrite Degeneration
in Aging and Infection.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Full-text verified. Provides the direct experimental evidence that NLP-29 is a ligand
for the neuronal GPCR NPR-12 (calcium mobilization in NPR-12-transfected HEK293T cells,
specific relative to NLP-31/NPR-32/beta2-AR) and that synthetic/overexpressed NLP-29
drives NPR-12- and autophagy-dependent PVD/FLP dendrite degeneration. Upgrades the ISM
neuropeptide-receptor-binding annotation.
- id: PMID:22870075
title: 'The Origin and Function of Anti-Fungal Peptides in C. elegans: Open Questions.'
findings: []
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: >-
Full-text review by the group that characterized these genes; explicitly frames the
precise mode of action of the NLP/CNC AMPs and possible regulatory (receptor) roles as
open questions ("Future studies should yield more insights into ... their precise mode of
action ..."), corroborating that the mechanistic knowledge gaps are real, not merely
uncurated.
- id: PMID:33259791
title: Innate Immunity Promotes Sleep through Epidermal Antimicrobial Peptides.
findings: []
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Shows epidermal AMPs act as cross-tissue somnogens and that NLP-29 specifically acts
through NPR-12 in locomotion-controlling neurons presynaptic to the sleep-active RIS
neuron. Corroborates the NPR-12 signaling-ligand function. Abstract-only in cache.
existing_annotations:
- term:
id: GO:0005576
label: extracellular region
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: >-
Localization to the extracellular region, mapped from the UniProt "Secreted"
subcellular-location keyword. Consistent with the N-terminal signal peptide (residues
1-22) and with experimental evidence that epidermally produced NLP-29 acts
non-cell-autonomously on distant neurons, implying it is secreted.
action: ACCEPT
reason: >-
NLP-29 is a signal-peptide-bearing secreted peptide; the SubCell-derived extracellular
annotation is well supported. Secretion is corroborated experimentally because
epidermally expressed NLP-29 must reach neurons expressing its receptor NPR-12 to signal.
supported_by:
- reference_id: PMID:29301098
supporting_text: direct access to the epidermis was required for NPR-12 to receive NLP-29
reference_section_type: RESULTS
- term:
id: GO:0003674
label: molecular_function
evidence_type: ND
original_reference_id: GO_REF:0000015
qualifier: enables
review:
summary: >-
Root molecular_function with the ND ("no biological data") evidence code, a WormBase
placeholder recorded in 2019 indicating no molecular-function data were curated at
that time.
action: REMOVE
reason: >-
The ND root placeholder is uninformative and is now superseded: a specific molecular
function (neuropeptide receptor binding, GO:0071855) is annotated and has since been
experimentally corroborated by demonstration that NLP-29 is a ligand/agonist of the
neuronal GPCR NPR-12. Per GO ND conventions, the root "no data" placeholder should be
removed once informative molecular-function evidence exists.
supported_by:
- reference_id: PMID:29301098
supporting_text: we conclude that NPR-12 is the receptor for NLP-29 in mediating aging-associated
PVD dendrite degeneration
reference_section_type: RESULTS
- term:
id: GO:0005576
label: extracellular region
evidence_type: ISM
original_reference_id: PMID:11717458
qualifier: located_in
review:
summary: >-
Sequence-model (ISM) prediction of extracellular localization, based on the
preproprotein/signal-peptide architecture identified for the nlp genes. Redundant with
the SubCell-derived IEA annotation but biologically valid.
action: ACCEPT
reason: >-
The prediction is sound: NLP-29 has a cleavable signal peptide and is a processed,
secreted peptide, consistent with an extracellular location. Retained as a valid
duplicate of the SubCell IEA annotation.
supported_by:
- reference_id: PMID:11717458
supporting_text: peptidergic neurotransmitters are encoded as preproproteins that are
posttranslationally processed to yield bioactive neuropeptides
reference_section_type: ABSTRACT
- term:
id: GO:0071855
label: neuropeptide receptor binding
evidence_type: ISM
original_reference_id: PMID:11717458
qualifier: enables
review:
summary: >-
Neuropeptide receptor binding, originally a family-based sequence-model prediction
(NLP-29 was named for its similarity to YGGWamide neuropeptides). This prediction is now
directly corroborated: synthetic NLP-29 activates the neuronal orphan GPCR NPR-12
(calcium mobilization in NPR-12-transfected cells, specific relative to the related
peptide NLP-31 and to NPR-32/beta2-AR), and genetic epistasis places NLP-29 upstream of
NPR-12 in both protective-sleep and dendrite-degeneration signaling.
action: ACCEPT
reason: >-
This is the single molecular activity of NLP-29 with direct experimental support and
represents a core function. The ISM annotation remains formally correct, and later work
identifies NPR-12 as a bona fide NLP-29 receptor, upgrading confidence in the term
without changing it. Retained as core.
supported_by:
- reference_id: PMID:29301098
supporting_text: induced a significant elevation of calcium, while the solvent-only control
did not cause any changes
reference_section_type: RESULTS
- reference_id: PMID:33259791
supporting_text: it acts through the neuropeptide receptor NPR-12 in locomotion-controlling
neurons that are presynaptic to RIS and that depolarize this neuron to induce sleep
reference_section_type: ABSTRACT
additional_reference_ids:
- PMID:29301098
- PMID:33259791
- term:
id: GO:0050832
label: defense response to fungus
evidence_type: IEP
original_reference_id: PMID:18636113
qualifier: involved_in
review:
summary: >-
nlp-29 is strongly and specifically induced in the epidermis by the natural fungal
pathogen Drechmeria coniospora and belongs to a co-regulated antimicrobial-peptide
cluster whose overexpression increases resistance to D. coniospora, supporting
involvement in antifungal defense. This antifungal role is the flagship, most-studied
aspect of nlp-29 biology and is captured by UniProt only as a keyword-derived IEA.
action: NEW
reason: >-
A defense-response-to-fungus annotation for nlp-29 is well motivated by infection-induced
expression plus cluster-level gain-of-function resistance, and matches the UniProt
keyword annotation. Added as an expression/genetics-based (IEP) annotation. Important
caveat: the nlp-29 single-gene null shows no marked resistance phenotype, so this is an
involvement, not a demonstration of individual necessity (see knowledge gaps).
supported_by:
- reference_id: PMID:18636113
supporting_text: These results indicate that the nlp genes can contribute in vivo to
increased resistance to fungal infection, but probably not to osmotic stress.
reference_section_type: RESULTS
- reference_id: PMID:15048112
supporting_text: We report here the identification of infection-inducible antimicrobial
peptides in Caenorhabditis elegans.
reference_section_type: ABSTRACT
- term:
id: GO:0007218
label: neuropeptide signaling pathway
evidence_type: IMP
original_reference_id: PMID:33259791
qualifier: involved_in
review:
summary: >-
NLP-29 acts as a secreted neuropeptide-like ligand in a cross-tissue signaling pathway:
it activates the neuronal GPCR NPR-12, and nlp-29/npr-12 genetic epistasis places NLP-29
upstream of NPR-12 in sleep-promoting and dendrite-degeneration signaling.
action: NEW
reason: >-
The neuropeptide-signaling role is now experimentally supported (direct NPR-12 activation
by synthetic NLP-29 and loss-of-function/epistasis phenotypes for sleep and dendrite
degeneration), and matches the UniProt keyword-derived annotation. Added to capture the
demonstrated signaling function alongside the antimicrobial-effector role.
supported_by:
- reference_id: PMID:33259791
supporting_text: it acts through the neuropeptide receptor NPR-12 in locomotion-controlling
neurons that are presynaptic to RIS and that depolarize this neuron to induce sleep
reference_section_type: ABSTRACT
- reference_id: PMID:29301098
supporting_text: we conclude that NPR-12 is the receptor for NLP-29 in mediating aging-associated
PVD dendrite degeneration
reference_section_type: RESULTS
additional_reference_ids:
- PMID:29301098
core_functions:
- description: >-
Secreted epidermal antimicrobial peptide of the NLP/YARP cluster whose expression is
induced by fungal (D. coniospora) and bacterial infection, wounding and osmotic stress;
contributes to antifungal host defense as a member of the co-regulated nlp-27 to nlp-34
cluster. Direct microbicidal activity of the mature NLP-29 peptides has not itself been
demonstrated, so there is no molecular-function term capturing an antimicrobial activity
(see knowledge gaps).
directly_involved_in:
- id: GO:0050832
label: defense response to fungus
locations:
- id: GO:0005576
label: extracellular region
supported_by:
- reference_id: PMID:18636113
supporting_text: These results indicate that the nlp genes can contribute in vivo to
increased resistance to fungal infection, but probably not to osmotic stress.
reference_section_type: RESULTS
- reference_id: PMID:15048112
supporting_text: Expression of two of these peptides, NLP-29 and NLP-31, was differentially
regulated by fungal and bacterial infection and was controlled in part by tir-1
reference_section_type: ABSTRACT
- description: >-
Secreted NLP-29 also functions as a signaling ligand for the neuronal orphan GPCR NPR-12.
This receptor interaction is demonstrated directly (calcium mobilization in NPR-12-expressing
cells and genetic epistasis) and mediates cross-tissue neuroimmune signaling: it promotes
protective sleep after wounding/infection and drives age- and infection-associated sensory
dendrite degeneration.
molecular_function:
id: GO:0071855
label: neuropeptide receptor binding
directly_involved_in:
- id: GO:0007218
label: neuropeptide signaling pathway
locations:
- id: GO:0005576
label: extracellular region
supported_by:
- reference_id: PMID:29301098
supporting_text: induced a significant elevation of calcium, while the solvent-only control
did not cause any changes
reference_section_type: RESULTS
- reference_id: PMID:33259791
supporting_text: it acts through the neuropeptide receptor NPR-12 in locomotion-controlling
neurons that are presynaptic to RIS and that depolarize this neuron to induce sleep
reference_section_type: ABSTRACT
proposed_new_terms: []
knowledge_gaps:
- gap_statement: >-
Whether the mature amidated NLP-29 peptides themselves directly kill or inhibit microbes,
and by what mechanism (membrane permeabilization, DNA binding as reported for the paralog
NLP-31, or another target), has not been demonstrated. Every C. elegans study uses nlp-29
as an induced-expression readout, and the in-vivo antifungal evidence comes from
overexpression of the whole nlp-29 cluster rather than a purified-peptide killing assay
for NLP-29.
boundary: >-
nlp-29 is a bona fide secreted AMP-family gene, strongly induced in the epidermis by
fungal/bacterial infection and wounding, and overexpression of the nlp-29 cluster increases
resistance to D. coniospora. Its one biochemically demonstrated molecular activity is as a
ligand/agonist of the neuronal GPCR NPR-12, not a microbicidal activity.
gap_kind:
- BIOLOGY
- ONTOLOGY
dark_aspect: MF_DARK
status: OPEN
significance: >-
This is why nlp-29 carries no molecular-function annotation for antimicrobial activity: such
activity is both unproven for NLP-29 itself and lacks an adequate GO molecular-function term.
Closing it would define the effector arm of the flagship C. elegans epidermal immune pathway.
resolution: >-
In vitro microbicidal, membrane-permeabilization and nucleic-acid-binding assays with the
individual synthetic mature NLP-29 peptides against D. coniospora and S. marcescens, plus
structural characterization.
provenance:
- reference_id: PMID:18636113
supporting_text: These results indicate that the nlp genes can contribute in vivo to
increased resistance to fungal infection, but probably not to osmotic stress.
reference_section_type: RESULTS
proposed_terms:
- proposed_name: antimicrobial peptide activity
proposed_definition: >-
A molecular function of a small secreted peptide that directly inhibits the growth of or
kills microorganisms, for example by permeabilizing microbial membranes or binding a
microbial macromolecular target, distinct from the biological process 'defense response'
and from receptor-mediated host signaling functions of the same peptide.
justification: >-
Antimicrobial peptides such as NLP-29 and its cluster paralogs have no adequate GO
molecular-function term for their effector activity; they are annotatable only at the
process level (defense response) or as the uninformative 'protein binding', leaving them
MF-dark despite a well-defined defensive role.
proposed_parent:
id: GO:0003674
label: molecular_function
- gap_statement: >-
The specific contribution of nlp-29 alone to pathogen resistance and survival is
undetermined: the nlp-29(tm1931) null shows no marked change in resistance to D. coniospora,
consistent with functional redundancy within the nlp-27 to nlp-34 cluster, so single-gene
loss-of-function has not established necessity.
boundary: >-
Loss of upstream regulators (e.g. tir-1, pmk-1, sta-2) abolishes nlp-29 induction and
reduces antifungal resistance, and cluster overexpression increases resistance; but these
manipulate the signaling pathway or the whole AMP cluster, not nlp-29 individually.
gap_kind:
- BIOLOGY
dark_aspect: RESIDUAL_SUBGAP
status: OPEN
significance: >-
Determines whether nlp-29 is an individually important effector or a redundant member of a
buffered AMP battery, which is central to interpreting the widely used Pnlp-29 immune reporter.
resolution: >-
Higher-order combinatorial deletions across the cluster and quantitative survival assays of
precise single and compound nlp mutants under D. coniospora and S. marcescens challenge.
provenance:
- reference_id: PMID:18636113
supporting_text: When we assayed the survival of the null mutant strain nlp-29(tm1931),
which cannot make any NLP-29, we saw no marked change in its resistance to D. coniospora
infection nor its lifespan in the absence of infection
reference_section_type: RESULTS
- reference_id: PMID:18636113
supporting_text: this could reflect a redundancy in the function of single nlp genes in the
nlp-29 cluster
reference_section_type: RESULTS
- gap_statement: >-
It is unknown which of the several distinct amidated peptides cleaved from the NLP-29
precursor mediate antimicrobial activity versus which engage NPR-12, and the predicted
proprotein processing and C-terminal amidation have not been directly demonstrated for NLP-29.
boundary: >-
The precursor sequence, signal peptide, predicted cleavage on paired basic residues and the
Tyr/Trp-amidation motifs are annotated by UniProt sequence analysis; synthetic full-length
NLP-29 peptide activates NPR-12 and induces dendrite degeneration, whereas the related NLP-31
does not.
gap_kind:
- BIOLOGY
dark_aspect: MF_DARK
status: OPEN
significance: >-
Distinguishing effector peptides from signaling peptides within a single precursor would
clarify whether the antimicrobial and neuroimmune functions of NLP-29 are molecularly separable.
resolution: >-
Mass-spectrometric identification of the endogenous mature peptides and structure-activity
assays of individual synthetic peptides against microbes and against NPR-12.
provenance:
- reference_id: PMID:29301098
supporting_text: To further confirm the essential role of NLP-29 in PVD dendrite degeneration,
we microinjected synthetic NLP-29 peptide into control animals
reference_section_type: RESULTS
- gap_statement: >-
Whether NLP-29's antimicrobial action is receptor-mediated or a direct physicochemical effect
on microbes is unresolved. NPR-12 is the only demonstrated receptor and mediates host
neuroimmune signaling (sleep, dendrite degeneration), not microbial killing, so any receptor
or target underlying an effector function is unidentified.
boundary: >-
NPR-12 is a validated NLP-29 receptor for cross-tissue host signaling and is expressed in
neurons, not microbes; no microbial or host target for a direct antimicrobial effect is known.
gap_kind:
- BIOLOGY
dark_aspect: MF_DARK
status: OPEN
significance: >-
Clarifies whether the same peptide uses distinct molecular mechanisms for host signaling versus
pathogen defense.
resolution: >-
Target-identification (pulldown/photo-crosslinking) with labeled NLP-29 peptides on microbial
and host membranes, and testing whether antimicrobial protection requires any host receptor.
provenance:
- reference_id: PMID:29301098
supporting_text: we conclude that NPR-12 is the receptor for NLP-29 in mediating aging-associated
PVD dendrite degeneration
reference_section_type: RESULTS
suggested_questions:
- question: >-
Do the individual mature amidated NLP-29 peptides have intrinsic microbicidal activity against
D. coniospora or S. marcescens in vitro, and if so by what mechanism?
experts:
- Nathalie Pujol
- Jonathan J. Ewbank
- question: >-
Is any single nlp gene in the nlp-29 cluster individually required for pathogen resistance, or
is the effector function fully redundant?
experts:
- Nathalie Pujol
- Jonathan J. Ewbank
suggested_experiments:
- hypothesis: >-
The mature NLP-29 peptides directly inhibit or kill fungi/bacteria.
description: >-
Synthesize each predicted amidated NLP-29 peptide and the full-length mature peptide, and test
dose-dependent inhibition of D. coniospora hyphal growth and S. marcescens viability in standard
microbicidal/MIC assays, with membrane-permeabilization and nucleic-acid-binding readouts.
experiment_type: in vitro antimicrobial assay
- hypothesis: >-
nlp-29 contributes non-redundantly to antifungal survival only in combination with its cluster paralogs.
description: >-
Generate precise single and higher-order CRISPR deletions across the nlp-27 to nlp-34 cluster and
compare survival after D. coniospora infection, distinguishing single-gene necessity from
cluster-level redundancy.
experiment_type: combinatorial genetics / survival assay