OCR-2 (OSM-9 and Capsaicin Receptor-related 2) is a TRPV (Transient Receptor Potential Vanilloid) family cation channel subunit that functions as part of a heteromeric complex with OSM-9 in C. elegans sensory neurons. The OCR-2/OSM-9 heteromeric channel is essential for multiple sensory modalities including thermosensation, chemosensation, osmosensation, and nociception. The channel localizes to the sensory cilia of amphid neurons (including ADL, ASH, AWA, ADF) where it mediates sensory transduction. OCR-2/OSM-9 is directly activated by warming stimuli and functions as an accessorial warm receptor contributing to temperature acclimatization. The channel also regulates serotonin biosynthesis in ADF neurons. Neither OCR-2 nor OSM-9 alone is sufficient for heat-evoked currents; functional channels require co-expression of both subunits. The channel displays outward-rectifying current-voltage characteristics typical of TRPV channels.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005262
calcium channel activity
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: OCR-2/OSM-9 heteromeric TRPV channel conducts calcium and other cations. Electrophysiology in Xenopus oocytes demonstrates warming-evoked inward currents with outward-rectifying I-V relationships when both subunits are co-expressed (PMID:33122746). The channel is a member of the TRP-CC family per TCDB (1.A.4.3.3). While "calcium channel activity" is correct, the more specific term GO:0097604 (temperature-gated cation channel activity) better captures the functional mode of gating.
Reason: IBA annotation is phylogenetically appropriate for TRPV family membership. OCR-2 is a bona fide calcium-permeable channel as demonstrated by electrophysiology studies showing warming-evoked inward currents in oocytes co-expressing OSM-9 and OCR-2 (PMID:33122746). The UniProt record also indicates calcium channel and calcium transport keywords.
Supporting Evidence:
PMID:33122746
Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing OSM-9 and OCR-2
PMID:12160748
Both OSM-9 and OCR-2 are essential for several forms of sensory transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
|
|
GO:0005886
plasma membrane
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: OCR-2 localizes to the plasma membrane of sensory cilia. Studies show OCR-2 and OSM-9 co-localize in sensory cilia and promote each other's localization to cilia (PMID:12160748). More specifically, OCR-2 is found in the non-motile (sensory) cilia of amphid neurons.
Reason: IBA annotation is appropriate. OCR-2 is a multi-pass transmembrane protein that localizes to the plasma membrane of sensory cilia. The UniProt record confirms cell membrane localization with multi-pass membrane topology.
Supporting Evidence:
PMID:12160748
In neurons that express both OSM-9 and OCR-2, tagged OCR-2 and OSM-9 proteins reside in sensory cilia and promote each other's localization to cilia
PMID:15673683
OCR-2 function in 5-HT production and osmotic sensing is governed by its N-terminal region upstream of the ankyrin repeats domain
|
|
GO:0098703
calcium ion import across plasma membrane
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: As a calcium-permeable TRP channel in the plasma membrane, OCR-2/OSM-9 mediates calcium influx upon activation. This is consistent with the sensory transduction function where calcium entry is part of signal transduction.
Reason: IBA annotation is appropriate as a consequence of calcium channel activity at the plasma membrane. The warming-evoked inward currents observed in oocytes are consistent with cation (including calcium) influx (PMID:33122746).
Supporting Evidence:
PMID:33122746
Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing OSM-9 and OCR-2
|
|
GO:0005216
monoatomic ion channel activity
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: OCR-2 contains the Ion_trans domain (IPR005821) and functions as an ion channel. This general term is consistent with TRPV channel function but is redundant with more specific calcium channel activity annotation.
Reason: IEA based on InterPro domain annotation is correct but very general. The ion transport domain (Pfam PF00520) is present from residues 517-771 per UniProt. While redundant with calcium channel activity, this broad term is not incorrect.
|
|
GO:0005262
calcium channel activity
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: IEA based on UniProt keyword mapping. This duplicates the IBA annotation but through different evidence. The annotation is consistent with OCR-2's demonstrated function.
Reason: Redundant with IBA annotation but correct. UniProt keywords include "Calcium channel" which supports this mapping.
|
|
GO:0005886
plasma membrane
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: IEA based on UniProt subcellular location. Duplicates the IBA annotation.
Reason: Redundant with IBA annotation but correct. UniProt subcellular location states "Cell membrane; Multi-pass membrane protein."
|
|
GO:0006811
monoatomic ion transport
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: General ion transport term. OCR-2 transports cations including calcium as part of sensory signaling. This is a parent term of more specific transport processes.
Reason: While very general, this is not incorrect. OCR-2 mediates ion transport as a TRPV channel subunit. More specific annotations (calcium ion transport) also exist.
|
|
GO:0006816
calcium ion transport
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Calcium ion transport is a consequence of calcium channel activity. OCR-2/OSM-9 mediates calcium influx during sensory transduction.
Reason: Appropriate IEA based on UniProt calcium transport keyword. Consistent with calcium channel function.
|
|
GO:0016020
membrane
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Very general localization term based on transmembrane domains. OCR-2 has 6-7 transmembrane helices per UniProt feature annotations. This is redundant with more specific plasma membrane annotation.
Reason: While overly general, this is not incorrect. OCR-2 is a multi-pass membrane protein with transmembrane helices at positions 426-445, 517-538, 550-573, 585-606, 613-630, 636-654, and 738-760 per UniProt.
|
|
GO:0034220
monoatomic ion transmembrane transport
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Ion transmembrane transport is the expected outcome of ion channel activity. This is consistent with OCR-2 function.
Reason: Correct but general. OCR-2/OSM-9 channels mediate transmembrane ion flux during sensory signaling.
|
|
GO:0055085
transmembrane transport
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Very general transport term. OCR-2 mediates transmembrane transport of cations.
Reason: While overly general, this is not incorrect for a transmembrane channel protein. More specific annotations exist.
|
|
GO:0070588
calcium ion transmembrane transport
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Calcium ion transmembrane transport is the specific outcome of calcium channel activity at the plasma membrane.
Reason: Appropriate specificity level for a calcium-permeable channel. Consistent with demonstrated electrophysiology showing cation currents.
|
|
GO:0010286
heat acclimation
|
IDA
PMID:33122746 OSM-9 and OCR-2 TRPV channels are accessorial warm receptors... |
ACCEPT |
Summary: Ohnishi et al. (2020) demonstrated that OSM-9/OCR-2 TRPV channels function as accessorial warm receptors required for temperature acclimatization. TRPV mutants (osm-9, ocr-2) showed abnormal temperature acclimatization with elevated cold tolerance. The defect was partially rescued by expression of cDNA in ADL neurons.
Reason: Well-supported experimental evidence. The paper directly demonstrates OCR-2's role in temperature acclimatization through mutant analysis, rescue experiments, and functional reconstitution studies. This represents a core biological process function.
Supporting Evidence:
PMID:33122746
OSM-9/OCR-2 regulates temperature acclimatisation and acts as an accessorial warmth-sensing receptor in ADL neurons
PMID:33122746
The abnormally elevated cold tolerance of osm-9 and ocr-2 mutants was partially rescued by expression of osm-9 and ocr-2 cDNA in ADL, respectively
|
|
GO:0010286
heat acclimation
|
IMP
PMID:33122746 OSM-9 and OCR-2 TRPV channels are accessorial warm receptors... |
ACCEPT |
Summary: Mutant phenotype evidence for heat acclimation role. ocr-2 mutants show abnormal temperature acclimatization behavior with elevated cold tolerance compared to wild-type animals.
Reason: Valid IMP evidence from mutant analysis. The osm-9 and ocr-2 mutants display abnormal cold tolerance/temperature acclimatization phenotypes that are partially rescued by transgenic expression.
Supporting Evidence:
PMID:33122746
Caenorhabditis elegans TRPV channel mutants showed abnormal temperature acclimatisation
|
|
GO:0010286
heat acclimation
|
IGI
PMID:33122746 OSM-9 and OCR-2 TRPV channels are accessorial warm receptors... |
ACCEPT |
Summary: Genetic interaction evidence. OSM-9 and OCR-2 function cooperatively, and their combined activity is required for heat acclimation. Neither single subunit alone produces functional warming responses.
Reason: Valid IGI evidence demonstrating functional interaction between OCR-2 and OSM-9. The double mutant and reconstitution studies show cooperative function.
Supporting Evidence:
PMID:33122746
OSM-9 and OCR-2 cooperatively responded to warming; however, neither TRPV subunit alone was responsive to warming
|
|
GO:0097604
temperature-gated cation channel activity
|
IDA
PMID:33122746 OSM-9 and OCR-2 TRPV channels are accessorial warm receptors... |
ACCEPT |
Summary: Direct experimental evidence from electrophysiology in Xenopus oocytes and in vivo reconstitution. Co-expression of OSM-9 and OCR-2 produces warming-evoked currents. Ectopic expression in non-temperature-sensing neurons conferred temperature responsiveness.
Reason: This is the most precise molecular function annotation for OCR-2/OSM-9. The heterologous expression studies and in vivo reconstitution directly demonstrate temperature-gated channel activity. This should be considered the primary molecular function annotation.
Supporting Evidence:
PMID:33122746
Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing OSM-9 and OCR-2
PMID:33122746
Ectopic expression of OSM-9 and OCR-2 in non-warming-responsive gustatory neurons in C. elegans and Xenopus oocytes revealed that OSM-9 and OCR-2 cooperatively responded to warming
|
|
GO:0005886
plasma membrane
|
IDA
PMID:15673683 Polymodal sensory function of the Caenorhabditis elegans OCR... |
ACCEPT |
Summary: Sokolchik et al. (2005) characterized OCR-2 function in its native cellular environment, demonstrating polymodal sensory function at the plasma membrane of sensory neurons.
Reason: IDA evidence for plasma membrane localization from functional studies showing OCR-2 activity in membrane-associated sensory processes.
Supporting Evidence:
PMID:15673683
we identify the molecular basis for the polymodal function of OCR-2 in its native cellular environment
|
|
GO:0097730
non-motile cilium
|
IDA
PMID:15673683 Polymodal sensory function of the Caenorhabditis elegans OCR... |
ACCEPT |
Summary: OCR-2 localizes to non-motile sensory cilia of amphid neurons. The sensory cilia of C. elegans chemosensory and thermosensory neurons are non-motile primary cilia used for environmental sensing.
Reason: Appropriate localization annotation. C. elegans sensory neurons have non-motile cilia where TRPV channels reside. OCR-2 function in sensory transduction occurs at these ciliary structures.
Supporting Evidence:
PMID:12160748
In neurons that express both OSM-9 and OCR-2, tagged OCR-2 and OSM-9 proteins reside in sensory cilia and promote each other's localization to cilia
|
|
GO:0097730
non-motile cilium
|
IDA
PMID:12160748 Combinatorial expression of TRPV channel proteins defines th... |
ACCEPT |
Summary: Tobin et al. (2002) directly demonstrated that tagged OCR-2 and OSM-9 proteins reside in sensory cilia and promote each other's localization to cilia. This study established the ciliary localization paradigm for C. elegans TRPV channels.
Reason: Key primary evidence for ciliary localization. The study used tagged proteins to directly visualize OCR-2 in sensory cilia and showed that OCR-2 and OSM-9 are codependent for proper ciliary localization.
Supporting Evidence:
PMID:12160748
In neurons that express both OSM-9 and OCR-2, tagged OCR-2 and OSM-9 proteins reside in sensory cilia and promote each other's localization to cilia
PMID:12160748
In neurons that express only OSM-9, tagged OSM-9 protein resides in the cell body and acts in sensory adaptation rather than sensory transduction
|
|
GO:0007635
chemosensory behavior
|
IMP
PMID:12160748 Combinatorial expression of TRPV channel proteins defines th... |
NEW |
Summary: OCR-2 mutants have defects in chemosensory behaviors. Tobin et al. (2002) showed that OSM-9 and OCR-2 are essential for olfaction, chemosensation, and responses to chemical stimuli. The ocr-2 mutation affects response to diacetyl in AWA neurons.
Reason: Critical biological process annotation missing from existing GOA. The deep research clearly documents OCR-2's role in chemosensory behavior, particularly in AWA-mediated olfaction and ASH-mediated nociception to chemicals like 1-octanol.
Supporting Evidence:
PMID:12160748
Both OSM-9 and OCR-2 are essential for several forms of sensory transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
PMID:15673683
the diacetyl sensitivity is mediated by independent mechanisms
file:worm/ocr-2/ocr-2-deep-research-falcon.md
OCR-2 functions with OSM-9 in multiple sensory neurons. In ADL, OSM-9/OCR-2 mediate warmth responses... In nociceptive contexts, a heteromeric OSM-9/OCR-2 channel is required for aversive chemical responses such as to 1-octanol
|
|
GO:0009593
detection of chemical stimulus
|
IMP
PMID:15673683 Polymodal sensory function of the Caenorhabditis elegans OCR... |
NEW |
Summary: OCR-2 is a polymodal sensory channel that responds to multiple stimuli including temperature, chemicals, and osmotic changes. Sokolchik et al. (2005) demonstrated the polymodal nature of OCR-2 function in chemical detection.
Reason: This captures OCR-2's fundamental role in sensory transduction for chemical stimuli. Sokolchik et al. (2005) demonstrated the polymodal nature of OCR-2 function.
Supporting Evidence:
PMID:15673683
Caenorhabditis elegans OCR-2 (OSM-9 and capsaicin receptor-related) is a TRPV (vanilloid subfamily of transient receptor potential channel) protein that regulates serotonin (5-HT) biosynthesis in chemosensory neurons and also mediates olfactory and osmotic sensation
file:worm/ocr-2/ocr-2-deep-research-falcon.md
OCR-2 mediates olfactory and osmotic sensation through different molecular determinants
|
Q: What is the precise ionic selectivity of the OCR-2/OSM-9 heteromeric channel?
Q: How does OCR-2 contribute to the non-cell autonomous UPR signaling in sensory neurons?
Q: What is the stoichiometry of the OCR-2/OSM-9 heteromeric channel?
Q: Are there other OCR family members that can substitute for OCR-2 in different neurons?
Q: How does the N-terminal domain of OCR-2 specifically regulate osmosensation vs olfaction?
Experiment: Single-channel patch clamp recording to determine the conductance and selectivity of OCR-2/OSM-9 channels
Hypothesis: The OCR-2/OSM-9 heteromeric channel has specific ionic conductance and selectivity properties
Type: electrophysiology
Experiment: Cryo-EM structure determination of the OCR-2/OSM-9 heteromeric complex
Hypothesis: The heteromeric structure reveals the basis for cooperative channel function
Type: structural biology
Experiment: FRET or proximity ligation assays to confirm heteromeric assembly in native neurons
Hypothesis: OCR-2 and OSM-9 directly interact in sensory cilia
Type: microscopy
Experiment: Optogenetic activation experiments to distinguish OCR-2/OSM-9-dependent from independent pathways in ADL
Hypothesis: There are redundant temperature-sensing pathways in ADL neurons
Type: optogenetics
Experiment: Systematic domain swap experiments between OCR family members to map functional determinants
Hypothesis: Specific domains confer sensory modality specificity
Type: molecular genetics
provider: falcon
model: Edison Scientific Literature
cached: false
start_time: '2025-12-28T10:56:47.380247'
end_time: '2025-12-28T11:03:17.930893'
duration_seconds: 390.55
template_file: templates/gene_research_go_focused.md
template_variables:
organism: worm
gene_id: ocr-2
gene_symbol: ocr-2
uniprot_accession: O61220
protein_description: 'SubName: Full=Ion transport domain-containing protein {ECO:0000313|EMBL:CCD63561.1};'
gene_info: Name=ocr-2 {ECO:0000313|EMBL:CCD63561.1, ECO:0000313|WormBase:T09A12.3a};
ORFNames=CELE_T09A12.3 {ECO:0000313|EMBL:CCD63561.1}, T09A12.3 {ECO:0000313|WormBase:T09A12.3a};
organism_full: Caenorhabditis elegans.
protein_family: Not specified in UniProt
protein_domains: Ankyrin_rpt. (IPR002110); Ankyrin_rpt-contain_sf. (IPR036770);
Ion_trans_dom. (IPR005821); TRPV. (IPR024862); Ank_2 (PF12796)
provider_config:
timeout: 600
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parameters:
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temperature: 0.1
citation_count: 22
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'ocr-2' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene ocr-2 (gene ID: ocr-2, UniProt: O61220) in worm.
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.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'ocr-2' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene ocr-2 (gene ID: ocr-2, UniProt: O61220) in worm.
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.
Research plan and verification
We verified that the target is Caenorhabditis elegans ocr-2, a TRPV-subfamily ion channel subunit that functions with OSM-9; the organism and functional identity are consistent with experimental studies demonstrating OSM-9/OCR-2 as a heteromeric, warmth-responsive TRPV channel in C. elegans sensory neurons (particularly ADL) (ohnishi2020osm9andocr2 pages 1-2, ohnishi2020osm9andocr2 pages 8-9). The literature below focuses strictly on C. elegans OCR-2/OSM-9 biology per the mandate to avoid cross-organism symbol ambiguity.
1) Key concepts and definitions
- Molecular identity and family: ocr-2 encodes a transient receptor potential vanilloid (TRPV)-like channel subunit. Together with OSM-9, it forms a functional TRPV channel required for thermosensory signaling and multiple chemosensory modalities in C. elegans (ohnishi2020osm9andocr2 pages 1-2, ohnishi2020osm9andocr2 pages 8-9).
- Channel assembly: OSM-9 and OCR-2 act cooperatively; single subunits alone do not confer warming-evoked currents, whereas co-expression yields a functional, heat-responsive channel, consistent with heteromeric TRPV assembly (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12).
- Sensory cilia context: OCR-2/OSM-9 signals in sensory cilia. TRPV-family channels require intraflagellar transport (IFT) for vectorial movement within cilia, and the ciliary transition zone (TZ) functions as a diffusion/gating barrier controlling membrane protein entry/exit (burght2019signalingcompartmentat pages 19-22).
2) Recent developments and latest research (emphasis 2023–2024)
- Cilia trafficking controls response dynamics: A 2024 study dissected the roles of cilia structure and IFT in shaping chemosensory responses. Acute or prolonged IFT inhibition can generate ectopic periciliary membrane compartment (PCMC) branches that mislocalize ciliary signaling proteins including OSM-9, altering odorant response desensitization despite preserved primary responses in some contexts (AWA). These data highlight how trafficking/localization of TRPV components modulate sensory coding, even without gross cilia loss (PLOS Biology, Nov 26, 2024; https://doi.org/10.1371/journal.pbio.3002892) (philbrook2024ciliastructureand pages 10-11, philbrook2024ciliastructureand pages 16-18).
- Osmolarity and egg-laying inhibition: A 2024 preprint reported that hyperosmotic conditions inhibit egg-laying via both sensory and biophysical mechanisms; under their conditions, ocr-2(vs29) mutants were still inhibited, suggesting OCR-2 is not solely required for this form of inhibition (bioRxiv, Dec 31, 2024; https://doi.org/10.1101/2024.12.30.630790) (medrano2024osmolarityregulatesc. pages 28-33).
3) Current applications and real-world implementations
- Reconstitution of TRPV thermosensitivity: Co-expression of OSM-9 and OCR-2 in Xenopus oocytes demonstrated warming-evoked inward currents with outward-rectifying I–V relationships, establishing a tractable heterologous system to probe TRPV gating and ion conduction for the worm channel complex (Scientific Reports, Oct 2020; https://doi.org/10.1038/s41598-020-75302-3) (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12).
- Behavioral neurogenetics in C. elegans: Genetic rescue and neuron-specific expression were used to link OSM-9/OCR-2 function in ADL to warmth responses and temperature acclimatisation; ectopic expression in a non-warmth-sensing neuron (ASER) conferred warming responsiveness, a powerful application of in vivo functional reconstitution (ohnishi2020osm9andocr2 pages 5-6, ohnishi2020osm9andocr2 pages 1-2).
- Endocannabinoid modulation of TRP-dependent behaviors: In vivo pharmacology and genetics showed that 2-AG engages TRP channel–dependent pathways to stimulate monoamine (5-HT and DA) release and modulate locomotory behavior, demonstrating utility of C. elegans as a model for TRP-linked neuromodulation (J. Neurosci., May 2019; https://doi.org/10.1523/JNEUROSCI.2371-18.2019) (oakes2019cannabinoidsstimulatethe pages 3-4, oakes2019cannabinoidsstimulatethe pages 9-10).
4) Expert opinions and analyses from authoritative sources
- Ciliary transport and gating as a framework: A 2019 synthesis on ciliary signaling and IFT emphasizes that intraflagellar transport is required for vectorial movement of TRPV channels in the ciliary membrane and that the transition zone establishes a selective barrier controlling receptor/cargo trafficking—principles that frame OCR-2/OSM-9 localization and signaling in cilia (bioRxiv, 2020 posting of 2019 study; https://doi.org/10.1101/861955) (burght2019signalingcompartmentat pages 19-22).
5) Relevant statistics and data from recent studies
- Thermosensory currents and temperature range: Co-expression of OSM-9 and OCR-2 in oocytes produced warming-evoked inward currents upon heating to approximately 35–36°C, with outward-rectifying I–V curves; neither subunit alone was heat-responsive (Scientific Reports, 2020; https://doi.org/10.1038/s41598-020-75302-3) (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12).
- In vivo thermosensory phenotypes: osm-9 and ocr-2 single mutants exhibit reduced warming-evoked Ca2+ responses in ADL over ~13–27°C, rescued by cell-specific cDNA expression, supporting cell-autonomous roles; double/triple mutant responses suggest compensatory mechanisms (Scientific Reports, 2020; https://doi.org/10.1038/s41598-020-75302-3) (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 5-6).
- Endocannabinoid dose–response: 2-AG inhibited locomotion dose-dependently with an IC50 near 3 μM; inhibition required serotonergic and dopaminergic signaling and involved TRP-channel–dependent monoamine release, establishing quantitative neuromodulatory impact (J. Neurosci., 2019; https://doi.org/10.1523/JNEUROSCI.2371-18.2019) (oakes2019cannabinoidsstimulatethe pages 3-4, oakes2019cannabinoidsstimulatethe pages 9-10).
Detailed functional annotation of ocr-2
Primary molecular function and substrates
- Channel class: OCR-2 is a TRPV-subfamily ion channel subunit. In heteromer with OSM-9, it forms an ion channel that is directly heat-activated in both heterologous expression (oocytes) and in vivo reconstitution, with properties resembling vertebrate TRPVs (outward-rectifying I–V) (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12).
- Stimuli: Heat is a direct stimulus for the OSM-9/OCR-2 channel; OSM-9/OCR-2 acts as an accessorial warmth receptor in ADL neurons contributing to temperature acclimatisation (ohnishi2020osm9andocr2 pages 1-2, ohnishi2020osm9andocr2 pages 8-9). Genetic literature also supports roles in chemosensation and mechanosensation across neuron types, consistent with polymodal TRPV function (ohnishi2020osm9andocr2 pages 8-9).
- Ion selectivity: The oocyte recordings demonstrate macroscopic currents and outward rectification; specific ionic selectivity ratios were not provided in the excerpts, but the behavior and I–V features are consistent with cation-permeable TRPV channels (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12).
Subunit composition and codependence
- Heteromerization: Functional heat responses require co-expression of OSM-9 and OCR-2; each alone is insufficient. In vivo, ciliary colocalization is reported to be codependent, and single-mutant phenotypes/rescues support heteromeric channel function (ohnishi2020osm9andocr2 pages 8-9, ohnishi2020osm9andocr2 pages 5-6).
Cellular/subcellular localization and trafficking
- Sensory cilia localization: OCR-2/OSM-9 localize to sensory cilia, where TRPV channels are trafficked by IFT; a transition zone barrier modulates ciliary entry/exit (burght2019signalingcompartmentat pages 19-22).
- IFT dependence and mislocalization under trafficking stress: Conditional IFT inhibition or IFT mutants cause formation of PCMC branches and mislocalization of OSM-9 and other ciliary signaling proteins from cilia to PCMC branches in AWA, altering desensitization kinetics while sometimes sparing primary responses, highlighting the importance of precise localization for response dynamics (PLOS Biology, 2024; https://doi.org/10.1371/journal.pbio.3002892) (philbrook2024ciliastructureand pages 10-11, philbrook2024ciliastructureand pages 16-18).
Neuronal expression and organismal roles
- Neuron types and behaviors: OCR-2 functions with OSM-9 in multiple sensory neurons. In ADL, OSM-9/OCR-2 mediate warmth responses and contribute to temperature acclimatisation (ohnishi2020osm9andocr2 pages 1-2, ohnishi2020osm9andocr2 pages 5-6). In nociceptive contexts, a heteromeric OSM-9/OCR-2 channel is required for aversive chemical responses such as to 1-octanol, consistent with roles in ASH nociceptors (J. Neurosci., 2019; https://doi.org/10.1523/JNEUROSCI.2371-18.2019) (oakes2019cannabinoidsstimulatethe pages 9-10). More broadly, modeling and synthesis works list OCR-2 as a TRPV nociceptor subunit with roles in chemosensation and thermosensation across amphid neurons, though some of these are preprints (castano2025modelingtrpvlikereceptors pages 13-17, pieroni2025identificationofmolecular pages 27-29).
- Osmosensation and egg-laying context: Hyperosmotic environments inhibit egg-laying via sensory and mechanical pathways; one 2024 study reported that ocr-2(vs29) mutants remained inhibited under high osmolarity, suggesting that OCR-2 is not alone sufficient to mediate this inhibition (bioRxiv, 2024; https://doi.org/10.1101/2024.12.30.630790) (medrano2024osmolarityregulatesc. pages 28-33).
Modulation by endogenous and exogenous ligands
- Endocannabinoids: 2-AG engages TRP channel–dependent mechanisms to stimulate serotonin and dopamine release and modulate locomotory behavior. Although this work did not isolate OCR-2 specifically, it implicates TRPV-like channels in cannabinoid-dependent neuromodulation in C. elegans, intersecting with OCR-2/OSM-9–dependent aversive responses (J. Neurosci., 2019; https://doi.org/10.1523/JNEUROSCI.2371-18.2019) (oakes2019cannabinoidsstimulatethe pages 3-4, oakes2019cannabinoidsstimulatethe pages 9-10).
- Vanilloids/terpenes: Preprint and synthesis studies suggest vanilloid-like ligands (e.g., capsaicin analogues) and certain terpenes can modulate C. elegans nociceptive behaviors via TRPV-like channels including OCR-2/OSM-9; structural modeling favors OCR-2 as a primary vanilloid target in C. elegans (ChemRxiv, 2025; https://doi.org/10.26434/chemrxiv-2025-bhspb) (castano2025modelingtrpvlikereceptors pages 13-17). These insights are preliminary and should be interpreted cautiously pending peer review.
- Octopamine: Within the cannabinoid-modulation study, octopamine signaling components are discussed in the broader monoaminergic modulation of aversive behaviors; however, direct OCR-2 modulation by octopamine was not supported by the provided excerpts (oakes2019cannabinoidsstimulatethe pages 9-10, oakes2019cannabinoidsstimulatethe pages 3-4).
Embedded summary table of key findings
| Topic | Key finding | Neuron / Cells | Subcellular localization | Evidence type | Year & Source (URL) |
|---|---|---|---|---|---|
| Thermosensation: OSM-9/OCR-2 heteromeric warm receptor | OSM-9 and OCR-2 act cooperatively as an accessorial warmth-sensing TRPV complex required for temperature acclimatisation and ADL warming-evoked Ca2+ responses. | ADL (and sufficiency shown in reconstituted ASER) | Sensory cilia; codependent ciliary colocalisation | Genetic mutants, Ca2+ imaging, rescue, behavioral assays | 2020, Scientific Reports — https://doi.org/10.1038/s41598-020-75302-3 (ohnishi2020osm9andocr2 pages 8-9, ohnishi2020osm9andocr2 pages 5-6) |
| Heterologous electrophysiology: Xenopus oocyte currents require co-expression | Neither OSM-9 nor OCR-2 alone produced heat-evoked currents; co-expression yields warming-induced inward currents with outward-rectifying I–V, supporting heteromeric channel function. | Xenopus oocytes; ectopic expression in ASER | Heterologous membrane (oocyte) / reconstituted neuronal membrane | Two-electrode voltage-clamp electrophysiology; reconstitution experiments | 2020, Scientific Reports — https://doi.org/10.1038/s41598-020-75302-3 (ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12) |
| Ciliary localization & IFT dependence; mislocalization to PCMC branches (Philbrook 2024) | Acute inhibition of IFT or IFT mutants cause ectopic periciliary membrane compartment (PCMC) branches that mislocalize OSM-9 (and some OCR-2) away from cilia, altering response dynamics and desensitization. | AWA (also effects seen across chemosensory neurons such as ASH) | Cilia base/tip and ectopic PCMC branches; ciliary vs periciliary redistribution | Live imaging (tagged receptors), Ca2+ imaging, genetic IFT perturbation | 2024, PLOS Biology — https://doi.org/10.1371/journal.pbio.3002892 (philbrook2024ciliastructureand pages 10-11, philbrook2024ciliastructureand pages 16-18) |
| IFT & transition-zone (TZ) gating of TRPV channels (van der Burght 2019) | Intraflagellar transport is required for vectorial movement and enrichment of TRPV-type channels in cilia; transition zone acts as a diffusion/gating barrier controlling ciliary entry. | Ciliated sensory neurons broadly | Transition zone and ciliary axoneme (tip/middle) | IFT perturbation, localization studies, review/bioRxiv synthesis citing Qin 2005 and others | 2019, bioRxiv — https://doi.org/10.1101/861955 (burght2019signalingcompartmentat pages 19-22) |
| Aversive chemical sensitivity & cannabinoid-linked modulation (1-octanol, etc.) | Aversive chemical (e.g., 1-octanol) nocifensive responses require a heteromeric OSM-9/OCR-2 TRPV channel in sensory neurons; cannabinoids/endocannabinoid signaling can engage TRP channels to modulate monoamine release and behavior. | ASH nociceptors; monoaminergic neurons (serotonin/dopamine release) | Sensory cilia (TRPV localization in cilia) and monoaminergic terminals | Behavioral assays, pharmacology, genetic mutants, neurochemical assays | 2019, J. Neurosci. — https://doi.org/10.1523/JNEUROSCI.2371-18.2019 (oakes2019cannabinoidsstimulatethe pages 9-10, oakes2019cannabinoidsstimulatethe pages 3-4) |
| Osmolarity & egg‑laying inhibition; ocr-2 mutants (Medrano 2024) | Hyperosmotic conditions inhibit egg-laying via sensory and biophysical mechanisms; reported ocr-2(vs29) mutants remained inhibited in high osmolarity, suggesting OCR-2 is not solely required for this inhibition (possible brood-size/confound noted). | HSNs, uv1s and chemosensory neurons; broader egg‑laying circuit | Sensory cilia (uv1/other chemosensory neuron localization implicated) | Behavioral assays, optogenetics, mutant analysis (bioRxiv preprint) | 2024, bioRxiv — https://doi.org/10.1101/2024.12.30.630790 (medrano2024osmolarityregulatesc. pages 28-33) |
| TRPV structural/modeling & vanilloid interactions (preprint summary) | Structural modeling and MD docking suggest OCR-2 (and OSM-9) may interact with vanilloid-like ligands (capsaicin analogues) and support OCR-2 as a relevant antinociceptive target in C. elegans (preprint synthesis). | Nociceptive sensory neurons (general TRPV-expressing cells) | Predicted pore/ankyrin-repeat and ligand-interaction regions (modeled) | In silico modeling (AlphaFold3, docking, MD) and literature synthesis — preprint | 2025, ChemRxiv (preprint) — https://doi.org/10.26434/chemrxiv-2025-bhspb (castano2025modelingtrpvlikereceptors pages 13-17) |
| Neuron expression spectrum & alleles (functional characterization preprint) | OCR-2 is reported expressed in many amphid sensory neurons (ASH, AWA, AWC, ASE, ADF, ASI, ASJ, ASK, IL2s) with characterized loss‑of‑function/deletion alleles linked to altered nociceptive and chemosensory behaviors (preprint). | ASH, AWA, AWC, ASE, ADF, ASI, ASJ, ASK, IL2s (amphid neurons) | Sensory cilia (amphid channel localization) | Genetic alleles, behavioral phenotyping, functional assays — preprint | 2025, bioRxiv (preprint) — https://doi.org/10.1101/2025.08.19.670888 (pieroni2025identificationofmolecular pages 27-29, pieroni2025identificationofmolecular pages 19-20) |
Table: Compact table summarizing experimental and modeling evidence for C. elegans OCR-2 (TRPV) covering function, localization, neurons, evidence types and citations for rapid reference.
Synthesis and outlook
The strongest evidence defines OCR-2 as a TRPV-family subunit that, together with OSM-9, forms a heat-responsive cation channel in sensory cilia, shaping thermosensory signaling in ADL and contributing to chemosensory and nociceptive behaviors across neuron types. Recent work (2024) emphasizes that continuous IFT and precise spatial organization of ciliary signaling components—including TRPV subunits—critically tune sensory response dynamics, particularly desensitization and adaptation. Endocannabinoid-dependent modulation of TRP pathways provides a tractable entry point to dissect neuromodulatory control of TRPV-dependent behaviors in vivo. Open questions include precise ionic selectivity and pharmacology of native OSM-9/OCR-2 channels, neuron-by-neuron contributions in polymodal nociception and osmosensation, and the molecular logic by which the ciliary transition zone and IFT adaptively regulate TRPV trafficking and signaling.
Citations (URLs and dates provided above): (ohnishi2020osm9andocr2 pages 1-2, ohnishi2020osm9andocr2 pages 8-9, ohnishi2020osm9andocr2 pages 7-8, ohnishi2020osm9andocr2 pages 11-12, burght2019signalingcompartmentat pages 19-22, philbrook2024ciliastructureand pages 10-11, philbrook2024ciliastructureand pages 16-18, medrano2024osmolarityregulatesc. pages 28-33, ohnishi2020osm9andocr2 pages 5-6, oakes2019cannabinoidsstimulatethe pages 3-4, oakes2019cannabinoidsstimulatethe pages 9-10, castano2025modelingtrpvlikereceptors pages 13-17, pieroni2025identificationofmolecular pages 27-29)
References
(ohnishi2020osm9andocr2 pages 1-2): Kohei Ohnishi, Shigeru Saito, Toru Miura, Akane Ohta, Makoto Tominaga, Takaaki Sokabe, and Atsushi Kuhara. Osm-9 and ocr-2 trpv channels are accessorial warm receptors in caenorhabditis elegans temperature acclimatisation. Scientific Reports, Oct 2020. URL: https://doi.org/10.1038/s41598-020-75302-3, doi:10.1038/s41598-020-75302-3. This article has 42 citations and is from a peer-reviewed journal.
(ohnishi2020osm9andocr2 pages 8-9): Kohei Ohnishi, Shigeru Saito, Toru Miura, Akane Ohta, Makoto Tominaga, Takaaki Sokabe, and Atsushi Kuhara. Osm-9 and ocr-2 trpv channels are accessorial warm receptors in caenorhabditis elegans temperature acclimatisation. Scientific Reports, Oct 2020. URL: https://doi.org/10.1038/s41598-020-75302-3, doi:10.1038/s41598-020-75302-3. This article has 42 citations and is from a peer-reviewed journal.
(ohnishi2020osm9andocr2 pages 7-8): Kohei Ohnishi, Shigeru Saito, Toru Miura, Akane Ohta, Makoto Tominaga, Takaaki Sokabe, and Atsushi Kuhara. Osm-9 and ocr-2 trpv channels are accessorial warm receptors in caenorhabditis elegans temperature acclimatisation. Scientific Reports, Oct 2020. URL: https://doi.org/10.1038/s41598-020-75302-3, doi:10.1038/s41598-020-75302-3. This article has 42 citations and is from a peer-reviewed journal.
(ohnishi2020osm9andocr2 pages 11-12): Kohei Ohnishi, Shigeru Saito, Toru Miura, Akane Ohta, Makoto Tominaga, Takaaki Sokabe, and Atsushi Kuhara. Osm-9 and ocr-2 trpv channels are accessorial warm receptors in caenorhabditis elegans temperature acclimatisation. Scientific Reports, Oct 2020. URL: https://doi.org/10.1038/s41598-020-75302-3, doi:10.1038/s41598-020-75302-3. This article has 42 citations and is from a peer-reviewed journal.
(burght2019signalingcompartmentat pages 19-22): Servaas N. van der Burght, Suzanne Rademakers, Jacque-Lynne Johnson, Chunmei Li, Gert-Jan Kremers, Adriaan B. Houtsmuller, Michel R. Leroux, and Gert Jansen. Signaling compartment at the ciliary tip is formed and maintained by intraflagellar transport and functions as sensitive salt detector. bioRxiv, Dec 2019. URL: https://doi.org/10.1101/861955, doi:10.1101/861955. This article has 0 citations and is from a poor quality or predatory journal.
(philbrook2024ciliastructureand pages 10-11): Alison Philbrook, Michael P. O’Donnell, Laura Grunenkovaite, and Piali Sengupta. Cilia structure and intraflagellar transport differentially regulate sensory response dynamics within and between c. elegans chemosensory neurons. PLOS Biology, 22:e3002892, Nov 2024. URL: https://doi.org/10.1371/journal.pbio.3002892, doi:10.1371/journal.pbio.3002892. This article has 8 citations and is from a highest quality peer-reviewed journal.
(philbrook2024ciliastructureand pages 16-18): Alison Philbrook, Michael P. O’Donnell, Laura Grunenkovaite, and Piali Sengupta. Cilia structure and intraflagellar transport differentially regulate sensory response dynamics within and between c. elegans chemosensory neurons. PLOS Biology, 22:e3002892, Nov 2024. URL: https://doi.org/10.1371/journal.pbio.3002892, doi:10.1371/journal.pbio.3002892. This article has 8 citations and is from a highest quality peer-reviewed journal.
(medrano2024osmolarityregulatesc. pages 28-33): Emmanuel Medrano, Karen Jendrick, Julian McQuirter, Claire Moxham, Dominique Rajic, Lila Rosendorf, Liraz Stilman, Dontrel Wilright, and Kevin M. Collins. Osmolarity regulates c. elegans egg-laying behavior via parallel chemosensory and biophysical mechanisms. bioRxiv, Dec 2024. URL: https://doi.org/10.1101/2024.12.30.630790, doi:10.1101/2024.12.30.630790. This article has 1 citations and is from a poor quality or predatory journal.
(ohnishi2020osm9andocr2 pages 5-6): Kohei Ohnishi, Shigeru Saito, Toru Miura, Akane Ohta, Makoto Tominaga, Takaaki Sokabe, and Atsushi Kuhara. Osm-9 and ocr-2 trpv channels are accessorial warm receptors in caenorhabditis elegans temperature acclimatisation. Scientific Reports, Oct 2020. URL: https://doi.org/10.1038/s41598-020-75302-3, doi:10.1038/s41598-020-75302-3. This article has 42 citations and is from a peer-reviewed journal.
(oakes2019cannabinoidsstimulatethe pages 3-4): Mitchell Oakes, Wen Jing Law, and Richard Komuniecki. Cannabinoids stimulate the trp channel-dependent release of both serotonin and dopamine to modulate behavior in c. elegans. The Journal of Neuroscience, 39:4142-4152, Mar 2019. URL: https://doi.org/10.1523/jneurosci.2371-18.2019, doi:10.1523/jneurosci.2371-18.2019. This article has 46 citations.
(oakes2019cannabinoidsstimulatethe pages 9-10): Mitchell Oakes, Wen Jing Law, and Richard Komuniecki. Cannabinoids stimulate the trp channel-dependent release of both serotonin and dopamine to modulate behavior in c. elegans. The Journal of Neuroscience, 39:4142-4152, Mar 2019. URL: https://doi.org/10.1523/jneurosci.2371-18.2019, doi:10.1523/jneurosci.2371-18.2019. This article has 46 citations.
(castano2025modelingtrpvlikereceptors pages 13-17): Jesus Castaño, Félix Côté, and Francis Beaudry. Modeling trpv-like receptors in c. elegans: structural insights into osm-9 and ocr-2 role in nociception and vanilloid ligand interactions. ChemRxiv, Oct 2025. URL: https://doi.org/10.26434/chemrxiv-2025-bhspb, doi:10.26434/chemrxiv-2025-bhspb. This article has 0 citations.
(pieroni2025identificationofmolecular pages 27-29): E. M. Pieroni, V. O’Connor, L. Holden-Dye, Pamela Imperadore, G. Fiorito, and J. Dillon. Identification of molecular nociceptors in octopus vulgaris through functional characterisation in caenorhabditis elegans. bioRxiv, Aug 2025. URL: https://doi.org/10.1101/2025.08.19.670888, doi:10.1101/2025.08.19.670888. This article has 0 citations and is from a poor quality or predatory journal.
(pieroni2025identificationofmolecular pages 19-20): E. M. Pieroni, V. O’Connor, L. Holden-Dye, Pamela Imperadore, G. Fiorito, and J. Dillon. Identification of molecular nociceptors in octopus vulgaris through functional characterisation in caenorhabditis elegans. bioRxiv, Aug 2025. URL: https://doi.org/10.1101/2025.08.19.670888, doi:10.1101/2025.08.19.670888. This article has 0 citations and is from a poor quality or predatory journal.
id: O61220
gene_symbol: ocr-2
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:6239
label: Caenorhabditis elegans
description: 'OCR-2 (OSM-9 and Capsaicin Receptor-related 2) is a TRPV (Transient
Receptor Potential Vanilloid) family cation channel subunit that functions as part
of a heteromeric complex with OSM-9 in C. elegans sensory neurons. The OCR-2/OSM-9
heteromeric channel is essential for multiple sensory modalities including thermosensation,
chemosensation, osmosensation, and nociception. The channel localizes to the sensory
cilia of amphid neurons (including ADL, ASH, AWA, ADF) where it mediates sensory
transduction. OCR-2/OSM-9 is directly activated by warming stimuli and functions
as an accessorial warm receptor contributing to temperature acclimatization. The
channel also regulates serotonin biosynthesis in ADF neurons. Neither OCR-2 nor
OSM-9 alone is sufficient for heat-evoked currents; functional channels require
co-expression of both subunits. The channel displays outward-rectifying current-voltage
characteristics typical of TRPV channels.
'
existing_annotations:
- term:
id: GO:0005262
label: calcium channel activity
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'OCR-2/OSM-9 heteromeric TRPV channel conducts calcium and other cations.
Electrophysiology in Xenopus oocytes demonstrates warming-evoked inward currents
with outward-rectifying I-V relationships when both subunits are co-expressed
(PMID:33122746). The channel is a member of the TRP-CC family per TCDB (1.A.4.3.3).
While "calcium channel activity" is correct, the more specific term GO:0097604
(temperature-gated cation channel activity) better captures the functional mode
of gating.
'
action: ACCEPT
reason: 'IBA annotation is phylogenetically appropriate for TRPV family membership.
OCR-2 is a bona fide calcium-permeable channel as demonstrated by electrophysiology
studies showing warming-evoked inward currents in oocytes co-expressing OSM-9
and OCR-2 (PMID:33122746). The UniProt record also indicates calcium channel
and calcium transport keywords.
'
supported_by:
- reference_id: PMID:33122746
supporting_text: Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing
OSM-9 and OCR-2
- reference_id: PMID:12160748
supporting_text: Both OSM-9 and OCR-2 are essential for several forms of sensory
transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
- term:
id: GO:0005886
label: plasma membrane
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'OCR-2 localizes to the plasma membrane of sensory cilia. Studies show
OCR-2 and OSM-9 co-localize in sensory cilia and promote each other''s localization
to cilia (PMID:12160748). More specifically, OCR-2 is found in the non-motile
(sensory) cilia of amphid neurons.
'
action: ACCEPT
reason: 'IBA annotation is appropriate. OCR-2 is a multi-pass transmembrane protein
that localizes to the plasma membrane of sensory cilia. The UniProt record confirms
cell membrane localization with multi-pass membrane topology.
'
supported_by:
- reference_id: PMID:12160748
supporting_text: In neurons that express both OSM-9 and OCR-2, tagged OCR-2
and OSM-9 proteins reside in sensory cilia and promote each other's localization
to cilia
- reference_id: PMID:15673683
supporting_text: OCR-2 function in 5-HT production and osmotic sensing is governed
by its N-terminal region upstream of the ankyrin repeats domain
- term:
id: GO:0098703
label: calcium ion import across plasma membrane
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'As a calcium-permeable TRP channel in the plasma membrane, OCR-2/OSM-9
mediates calcium influx upon activation. This is consistent with the sensory
transduction function where calcium entry is part of signal transduction.
'
action: ACCEPT
reason: 'IBA annotation is appropriate as a consequence of calcium channel activity
at the plasma membrane. The warming-evoked inward currents observed in oocytes
are consistent with cation (including calcium) influx (PMID:33122746).
'
supported_by:
- reference_id: PMID:33122746
supporting_text: Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing
OSM-9 and OCR-2
- term:
id: GO:0005216
label: monoatomic ion channel activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: 'OCR-2 contains the Ion_trans domain (IPR005821) and functions as an
ion channel. This general term is consistent with TRPV channel function but
is redundant with more specific calcium channel activity annotation.
'
action: ACCEPT
reason: 'IEA based on InterPro domain annotation is correct but very general.
The ion transport domain (Pfam PF00520) is present from residues 517-771 per
UniProt. While redundant with calcium channel activity, this broad term is not
incorrect.
'
- term:
id: GO:0005262
label: calcium channel activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'IEA based on UniProt keyword mapping. This duplicates the IBA annotation
but through different evidence. The annotation is consistent with OCR-2''s demonstrated
function.
'
action: ACCEPT
reason: 'Redundant with IBA annotation but correct. UniProt keywords include "Calcium
channel" which supports this mapping.
'
- term:
id: GO:0005886
label: plasma membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: 'IEA based on UniProt subcellular location. Duplicates the IBA annotation.
'
action: ACCEPT
reason: 'Redundant with IBA annotation but correct. UniProt subcellular location
states "Cell membrane; Multi-pass membrane protein."
'
- term:
id: GO:0006811
label: monoatomic ion transport
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: 'General ion transport term. OCR-2 transports cations including calcium
as part of sensory signaling. This is a parent term of more specific transport
processes.
'
action: ACCEPT
reason: 'While very general, this is not incorrect. OCR-2 mediates ion transport
as a TRPV channel subunit. More specific annotations (calcium ion transport)
also exist.
'
- term:
id: GO:0006816
label: calcium ion transport
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'Calcium ion transport is a consequence of calcium channel activity.
OCR-2/OSM-9 mediates calcium influx during sensory transduction.
'
action: ACCEPT
reason: 'Appropriate IEA based on UniProt calcium transport keyword. Consistent
with calcium channel function.
'
- term:
id: GO:0016020
label: membrane
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: 'Very general localization term based on transmembrane domains. OCR-2
has 6-7 transmembrane helices per UniProt feature annotations. This is redundant
with more specific plasma membrane annotation.
'
action: ACCEPT
reason: 'While overly general, this is not incorrect. OCR-2 is a multi-pass membrane
protein with transmembrane helices at positions 426-445, 517-538, 550-573, 585-606,
613-630, 636-654, and 738-760 per UniProt.
'
- term:
id: GO:0034220
label: monoatomic ion transmembrane transport
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'Ion transmembrane transport is the expected outcome of ion channel activity.
This is consistent with OCR-2 function.
'
action: ACCEPT
reason: 'Correct but general. OCR-2/OSM-9 channels mediate transmembrane ion flux
during sensory signaling.
'
- term:
id: GO:0055085
label: transmembrane transport
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: 'Very general transport term. OCR-2 mediates transmembrane transport
of cations.
'
action: ACCEPT
reason: 'While overly general, this is not incorrect for a transmembrane channel
protein. More specific annotations exist.
'
- term:
id: GO:0070588
label: calcium ion transmembrane transport
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'Calcium ion transmembrane transport is the specific outcome of calcium
channel activity at the plasma membrane.
'
action: ACCEPT
reason: 'Appropriate specificity level for a calcium-permeable channel. Consistent
with demonstrated electrophysiology showing cation currents.
'
- term:
id: GO:0010286
label: heat acclimation
evidence_type: IDA
original_reference_id: PMID:33122746
review:
summary: 'Ohnishi et al. (2020) demonstrated that OSM-9/OCR-2 TRPV channels function
as accessorial warm receptors required for temperature acclimatization. TRPV
mutants (osm-9, ocr-2) showed abnormal temperature acclimatization with elevated
cold tolerance. The defect was partially rescued by expression of cDNA in ADL
neurons.
'
action: ACCEPT
reason: 'Well-supported experimental evidence. The paper directly demonstrates
OCR-2''s role in temperature acclimatization through mutant analysis, rescue
experiments, and functional reconstitution studies. This represents a core biological
process function.
'
supported_by:
- reference_id: PMID:33122746
supporting_text: OSM-9/OCR-2 regulates temperature acclimatisation and acts
as an accessorial warmth-sensing receptor in ADL neurons
- reference_id: PMID:33122746
supporting_text: The abnormally elevated cold tolerance of osm-9 and ocr-2 mutants
was partially rescued by expression of osm-9 and ocr-2 cDNA in ADL, respectively
- term:
id: GO:0010286
label: heat acclimation
evidence_type: IMP
original_reference_id: PMID:33122746
review:
summary: 'Mutant phenotype evidence for heat acclimation role. ocr-2 mutants show
abnormal temperature acclimatization behavior with elevated cold tolerance compared
to wild-type animals.
'
action: ACCEPT
reason: 'Valid IMP evidence from mutant analysis. The osm-9 and ocr-2 mutants
display abnormal cold tolerance/temperature acclimatization phenotypes that
are partially rescued by transgenic expression.
'
supported_by:
- reference_id: PMID:33122746
supporting_text: Caenorhabditis elegans TRPV channel mutants showed abnormal
temperature acclimatisation
- term:
id: GO:0010286
label: heat acclimation
evidence_type: IGI
original_reference_id: PMID:33122746
review:
summary: 'Genetic interaction evidence. OSM-9 and OCR-2 function cooperatively,
and their combined activity is required for heat acclimation. Neither single
subunit alone produces functional warming responses.
'
action: ACCEPT
reason: 'Valid IGI evidence demonstrating functional interaction between OCR-2
and OSM-9. The double mutant and reconstitution studies show cooperative function.
'
supported_by:
- reference_id: PMID:33122746
supporting_text: OSM-9 and OCR-2 cooperatively responded to warming; however,
neither TRPV subunit alone was responsive to warming
- term:
id: GO:0097604
label: temperature-gated cation channel activity
evidence_type: IDA
original_reference_id: PMID:33122746
review:
summary: 'Direct experimental evidence from electrophysiology in Xenopus oocytes
and in vivo reconstitution. Co-expression of OSM-9 and OCR-2 produces warming-evoked
currents. Ectopic expression in non-temperature-sensing neurons conferred temperature
responsiveness.
'
action: ACCEPT
reason: 'This is the most precise molecular function annotation for OCR-2/OSM-9.
The heterologous expression studies and in vivo reconstitution directly demonstrate
temperature-gated channel activity. This should be considered the primary molecular
function annotation.
'
supported_by:
- reference_id: PMID:33122746
supporting_text: Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing
OSM-9 and OCR-2
- reference_id: PMID:33122746
supporting_text: Ectopic expression of OSM-9 and OCR-2 in non-warming-responsive
gustatory neurons in C. elegans and Xenopus oocytes revealed that OSM-9 and
OCR-2 cooperatively responded to warming
- term:
id: GO:0005886
label: plasma membrane
evidence_type: IDA
original_reference_id: PMID:15673683
review:
summary: 'Sokolchik et al. (2005) characterized OCR-2 function in its native cellular
environment, demonstrating polymodal sensory function at the plasma membrane
of sensory neurons.
'
action: ACCEPT
reason: 'IDA evidence for plasma membrane localization from functional studies
showing OCR-2 activity in membrane-associated sensory processes.
'
supported_by:
- reference_id: PMID:15673683
supporting_text: we identify the molecular basis for the polymodal function
of OCR-2 in its native cellular environment
- term:
id: GO:0097730
label: non-motile cilium
evidence_type: IDA
original_reference_id: PMID:15673683
review:
summary: 'OCR-2 localizes to non-motile sensory cilia of amphid neurons. The sensory
cilia of C. elegans chemosensory and thermosensory neurons are non-motile primary
cilia used for environmental sensing.
'
action: ACCEPT
reason: 'Appropriate localization annotation. C. elegans sensory neurons have
non-motile cilia where TRPV channels reside. OCR-2 function in sensory transduction
occurs at these ciliary structures.
'
supported_by:
- reference_id: PMID:12160748
supporting_text: In neurons that express both OSM-9 and OCR-2, tagged OCR-2
and OSM-9 proteins reside in sensory cilia and promote each other's localization
to cilia
- term:
id: GO:0097730
label: non-motile cilium
evidence_type: IDA
original_reference_id: PMID:12160748
review:
summary: 'Tobin et al. (2002) directly demonstrated that tagged OCR-2 and OSM-9
proteins reside in sensory cilia and promote each other''s localization to cilia.
This study established the ciliary localization paradigm for C. elegans TRPV
channels.
'
action: ACCEPT
reason: 'Key primary evidence for ciliary localization. The study used tagged
proteins to directly visualize OCR-2 in sensory cilia and showed that OCR-2
and OSM-9 are codependent for proper ciliary localization.
'
supported_by:
- reference_id: PMID:12160748
supporting_text: In neurons that express both OSM-9 and OCR-2, tagged OCR-2
and OSM-9 proteins reside in sensory cilia and promote each other's localization
to cilia
- reference_id: PMID:12160748
supporting_text: In neurons that express only OSM-9, tagged OSM-9 protein resides
in the cell body and acts in sensory adaptation rather than sensory transduction
- term:
id: GO:0007635
label: chemosensory behavior
evidence_type: IMP
original_reference_id: PMID:12160748
review:
summary: 'OCR-2 mutants have defects in chemosensory behaviors. Tobin et al. (2002)
showed that OSM-9 and OCR-2 are essential for olfaction, chemosensation, and
responses to chemical stimuli. The ocr-2 mutation affects response to diacetyl
in AWA neurons.
'
action: NEW
reason: 'Critical biological process annotation missing from existing GOA. The
deep research clearly documents OCR-2''s role in chemosensory behavior, particularly
in AWA-mediated olfaction and ASH-mediated nociception to chemicals like 1-octanol.
'
supported_by:
- reference_id: PMID:12160748
supporting_text: Both OSM-9 and OCR-2 are essential for several forms of sensory
transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
- reference_id: PMID:15673683
supporting_text: the diacetyl sensitivity is mediated by independent mechanisms
- reference_id: file:worm/ocr-2/ocr-2-deep-research-falcon.md
supporting_text: OCR-2 functions with OSM-9 in multiple sensory neurons. In
ADL, OSM-9/OCR-2 mediate warmth responses... In nociceptive contexts, a heteromeric
OSM-9/OCR-2 channel is required for aversive chemical responses such as to
1-octanol
- term:
id: GO:0009593
label: detection of chemical stimulus
evidence_type: IMP
original_reference_id: PMID:15673683
review:
summary: 'OCR-2 is a polymodal sensory channel that responds to multiple stimuli
including temperature, chemicals, and osmotic changes. Sokolchik et al. (2005)
demonstrated the polymodal nature of OCR-2 function in chemical detection.
'
action: NEW
reason: 'This captures OCR-2''s fundamental role in sensory transduction for chemical
stimuli. Sokolchik et al. (2005) demonstrated the polymodal nature of OCR-2
function.
'
supported_by:
- reference_id: PMID:15673683
supporting_text: Caenorhabditis elegans OCR-2 (OSM-9 and capsaicin receptor-related)
is a TRPV (vanilloid subfamily of transient receptor potential channel) protein
that regulates serotonin (5-HT) biosynthesis in chemosensory neurons and also
mediates olfactory and osmotic sensation
- reference_id: file:worm/ocr-2/ocr-2-deep-research-falcon.md
supporting_text: OCR-2 mediates olfactory and osmotic sensation through different
molecular determinants
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings:
- statement: OCR-2 contains Ion_trans domain (IPR005821), TRPV family (IPR024862),
and Ankyrin repeats (IPR002110)
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings:
- statement: OCR-2 clusters with TRPV family channels supporting calcium channel
activity annotation
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings:
- statement: UniProt keywords include Calcium channel, Calcium transport, Ion transport,
Ion channel
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping
findings:
- statement: UniProt indicates cell membrane localization with multi-pass transmembrane
topology
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings:
- statement: Automated annotation combining multiple evidence sources
- id: PMID:12160748
title: Combinatorial expression of TRPV channel proteins defines their sensory functions
and subcellular localization in C. elegans neurons.
findings:
- statement: OCR-2 and OSM-9 co-localize in sensory cilia and promote each other's
ciliary localization
supporting_text: In neurons that express both OSM-9 and OCR-2, tagged OCR-2 and
OSM-9 proteins reside in sensory cilia and promote each other's localization
to cilia
- statement: Both OSM-9 and OCR-2 are essential for olfaction, osmosensation, mechanosensation,
and chemosensation
supporting_text: Both OSM-9 and OCR-2 are essential for several forms of sensory
transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
- statement: In neurons expressing only OSM-9, protein resides in cell body for
adaptation rather than transduction
supporting_text: In neurons that express only OSM-9, tagged OSM-9 protein resides
in the cell body and acts in sensory adaptation rather than sensory transduction
- statement: Heteromeric TRPV assembly is required for sensory transduction function
supporting_text: distinct sensory functions arise from different combinations
of OSM-9 and related OCR TRPV proteins
- id: PMID:15673683
title: Polymodal sensory function of the Caenorhabditis elegans OCR-2 channel arises
from distinct intrinsic determinants within the protein and is selectively conserved
in mammalian TRPV proteins.
findings:
- statement: OCR-2 regulates serotonin (5-HT) biosynthesis in ADF chemosensory neurons
supporting_text: OCR-2 (OSM-9 and capsaicin receptor-related) is a TRPV (vanilloid
subfamily of transient receptor potential channel) protein that regulates serotonin
(5-HT) biosynthesis in chemosensory neurons
- statement: OCR-2 mediates olfactory and osmotic sensation through different molecular
determinants
supporting_text: mediates olfactory and osmotic sensation. Here, we identify the
molecular basis for the polymodal function of OCR-2
- statement: N-terminal region governs 5-HT production and osmotic sensing
supporting_text: OCR-2 function in 5-HT production and osmotic sensing is governed
by its N-terminal region upstream of the ankyrin repeats domain
- statement: Diacetyl sensitivity mediated by independent mechanisms
supporting_text: the diacetyl sensitivity is mediated by independent mechanisms
- statement: G36E substitution (ocr-2(yz5)) eliminates osmosensation in ASH but
not diacetyl response in AWA
supporting_text: The G36E substitution causes dramatic downregulation of 5-HT
synthesis in the ADF neurons, eliminates osmosensation mediated by the ASH neurons,
but does not affect the response to the odorant diacetyl mediated by the AWA
neurons
- id: PMID:33122746
title: OSM-9 and OCR-2 TRPV channels are accessorial warm receptors in Caenorhabditis
elegans temperature acclimatisation.
findings:
- statement: OSM-9/OCR-2 heteromeric channel acts as accessorial warmth-sensing
receptor in ADL neurons
supporting_text: OSM-9/OCR-2 regulates temperature acclimatisation and acts as
an accessorial warmth-sensing receptor in ADL neurons
- statement: TRPV mutants show abnormal temperature acclimatization with elevated
cold tolerance
supporting_text: Caenorhabditis elegans TRPV channel mutants showed abnormal temperature
acclimatisation
- statement: Neither subunit alone produces warming-evoked currents; heteromerization
required
supporting_text: OSM-9 and OCR-2 cooperatively responded to warming; however,
neither TRPV subunit alone was responsive to warming
- statement: Warming-evoked inward currents with outward-rectifying I-V in Xenopus
oocytes
supporting_text: Thermal stimuli evoked inward currents in Xenopus oocytes co-expressing
OSM-9 and OCR-2
- statement: Ectopic expression in ASER neurons confers temperature responsiveness
supporting_text: Ectopic expression of OSM-9 and OCR-2 in non-warming-responsive
gustatory neurons in C. elegans and Xenopus oocytes revealed that OSM-9 and
OCR-2 cooperatively responded to warming
- statement: ADL responds to warming over approximately 13-27 degrees C range
supporting_text: warming stimuli in the osm-9 ocr-2; ocr-1 triple mutant revealed
decreased thermal responses compared with wild-type
core_functions:
- description: 'Primary molecular function. OCR-2 is a subunit of a temperature-gated
TRPV channel that requires heteromerization with OSM-9 for warmth-sensing activity.
This is demonstrated by electrophysiology in Xenopus oocytes and functional reconstitution
in vivo.
'
molecular_function:
id: GO:0097604
label: temperature-gated cation channel activity
directly_involved_in:
- id: GO:0010286
label: heat acclimation
locations:
- id: GO:0097730
label: non-motile cilium
- id: GO:0005886
label: plasma membrane
supported_by:
- reference_id: PMID:33122746
supporting_text: OSM-9 and OCR-2 cooperatively responded to warming; however,
neither TRPV subunit alone was responsive to warming
- description: 'Core molecular function as a calcium-permeable channel. As a TRPV
family channel, OCR-2/OSM-9 conducts calcium and other cations. The channel activity
underlies sensory transduction across multiple modalities including chemosensation.
'
molecular_function:
id: GO:0005262
label: calcium channel activity
directly_involved_in:
- id: GO:0007635
label: chemosensory behavior
- id: GO:0009593
label: detection of chemical stimulus
locations:
- id: GO:0097730
label: non-motile cilium
supported_by:
- reference_id: PMID:12160748
supporting_text: Both OSM-9 and OCR-2 are essential for several forms of sensory
transduction, including olfaction, osmosensation, mechanosensation, and chemosensation
- reference_id: PMID:15673683
supporting_text: OCR-2 (OSM-9 and capsaicin receptor-related) is a TRPV (vanilloid
subfamily of transient receptor potential channel) protein that regulates serotonin
(5-HT) biosynthesis in chemosensory neurons
proposed_new_terms: []
suggested_questions:
- question: What is the precise ionic selectivity of the OCR-2/OSM-9 heteromeric channel?
- question: How does OCR-2 contribute to the non-cell autonomous UPR signaling in
sensory neurons?
- question: What is the stoichiometry of the OCR-2/OSM-9 heteromeric channel?
- question: Are there other OCR family members that can substitute for OCR-2 in different
neurons?
- question: How does the N-terminal domain of OCR-2 specifically regulate osmosensation
vs olfaction?
suggested_experiments:
- description: Single-channel patch clamp recording to determine the conductance and
selectivity of OCR-2/OSM-9 channels
hypothesis: The OCR-2/OSM-9 heteromeric channel has specific ionic conductance and
selectivity properties
experiment_type: electrophysiology
- description: Cryo-EM structure determination of the OCR-2/OSM-9 heteromeric complex
hypothesis: The heteromeric structure reveals the basis for cooperative channel
function
experiment_type: structural biology
- description: FRET or proximity ligation assays to confirm heteromeric assembly in
native neurons
hypothesis: OCR-2 and OSM-9 directly interact in sensory cilia
experiment_type: microscopy
- description: Optogenetic activation experiments to distinguish OCR-2/OSM-9-dependent
from independent pathways in ADL
hypothesis: There are redundant temperature-sensing pathways in ADL neurons
experiment_type: optogenetics
- description: Systematic domain swap experiments between OCR family members to map
functional determinants
hypothesis: Specific domains confer sensory modality specificity
experiment_type: molecular genetics
tags:
- caeel-upr-stress