{"gene":"ODR4","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1998,"finding":"C. elegans ODR-4 encodes a novel membrane protein expressed exclusively on intracellular membranes of chemosensory neurons, where it acts cell-autonomously to facilitate odorant receptor folding or localization to olfactory cilia. Loss of odr-4 or odr-8 prevents localization of a subset of seven-transmembrane odorant receptors (but not ion channels, G-alpha proteins, or other receptor types) to cilia.","method":"Genetic loss-of-function (odr-4 and odr-8 mutants), cell-type-specific expression analysis, subcellular localization by imaging","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function with defined cellular phenotype, cell-autonomous rescue, localization experiments; foundational paper replicated by subsequent studies","pmids":["9590179"],"is_preprint":false},{"year":2000,"finding":"Mammalian ODR-4 (human homolog) facilitates trafficking of rat olfactory receptor U131 to the plasma membrane in odora and CHO cells, demonstrating a conserved role in GPCR trafficking from ER to plasma membrane across species.","method":"Heterologous expression of ODR-4 in odora and CHO cell lines, plasma membrane trafficking assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional trafficking assay in heterologous cells, single lab, multiple cell lines tested","pmids":["11060288"],"is_preprint":false},{"year":2002,"finding":"ODR-4 and ODR-8 are required for localizing sensory chemoreceptors to cilia in nociceptive neurons ASH and ADL, and odr-4 mutant social feeding phenotype is suppressed by osm-3 mutations, placing odr-4 upstream or in opposition to the osm-3 pathway in regulating social feeding behavior.","method":"Genetic epistasis (odr-4; osm-3 double mutants), neuron ablation, behavioral assays","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in C. elegans with defined behavioral readout, single lab","pmids":["12410303"],"is_preprint":false},{"year":2006,"finding":"ODR-4, together with TRP channel subunits OCR-2 and OSM-9, acts in nociceptive neurons ASH and ADL to promote avoidance of high O2 and aggregation behavior, supporting ODR-4's role in functional chemosensory receptor presentation at cilia.","method":"Genetic loss-of-function, behavioral assays (O2 avoidance, aggregation)","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined behavioral phenotype, single lab","pmids":["16581509"],"is_preprint":false},{"year":2014,"finding":"ODR-4 encodes a conserved tail-anchored transmembrane protein that physically interacts with ODR-8/UfSP2 (the C. elegans ortholog of Ufm1-specific protease 2) at the ER membrane. This ODR-4/ODR-8 complex promotes folding, maturation, or ER export of GPCRs such as ODR-10. ODR-4 also physically binds the GPCR ODR-10. The human orthologs ODR4 (C1orf27) and UfSP2 also physically interact, suggesting evolutionary conservation. The protease activity of ODR-8/UfSP2 is dispensable for GPCR trafficking, and ufm-1 deletion does not alter chemoreceptor cilia trafficking.","method":"Co-immunoprecipitation (physical interaction between ODR-4, ODR-8, and ODR-10 at ER), genetic rescue with catalytic-dead ODR-8 mutants, ufm-1 deletion epistasis, subcellular localization","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis with active-site mutagenesis, localization, and deletion of pathway component; multiple orthogonal methods in single study","pmids":["24603482"],"is_preprint":false},{"year":2005,"finding":"A full-length human cDNA homologous to C. elegans ODR-4 was isolated (C1orf27/FLJ20505), expressed in 41 of 44 human, mouse, and rat tissues, and shares predicted structural features with orthologs, suggesting a conserved ubiquitous function in GPCR trafficking.","method":"RecA-based gene enrichment, cDNA cloning, tissue expression analysis, bioinformatic structural comparison","journal":"Genomics","confidence":"Low","confidence_rationale":"Tier 4 / Weak — gene identification and expression survey without direct functional assay for the human protein","pmids":["15718105"],"is_preprint":false},{"year":2022,"finding":"Human C1orf27 (ODR4 ortholog) physically associates with α2A-adrenergic receptor (α2A-AR) specifically via its third intracellular loop and C-terminus. siRNA knockdown or CRISPR-Cas9 knockout of C1orf27 markedly impedes ER-to-Golgi export kinetics of newly synthesized α2A-AR (half-time prolonged >65%) and significantly inhibits surface transport of α2A-AR, β2-AR, and dopamine D2 receptor, but not epidermal growth factor receptor.","method":"siRNA knockdown, CRISPR-Cas9 knockout, RUSH (retention using selective hooks) ER-to-Golgi export assay, bioluminescence resonance energy transfer (BRET) assay, ELISA surface transport assay, co-immunoprecipitation mapping of interaction domains","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO+KD, RUSH kinetics, BRET, ELISA, Co-IP domain mapping) in single lab demonstrating specific GPCR trafficking function","pmids":["35551911"],"is_preprint":false},{"year":2026,"finding":"Human C1orf27 (ODR4) and UFSP2 form a complex at the ER membrane; UFSP2 requires C1orf27 for its ER recruitment. C1orf27, UFSP2, and cargo GPCRs form a multi-protein complex, and GPCR interaction with C1orf27 is required for their ER export and forward delivery to the Golgi and cell surface. UFSP2 catalytic activity is dispensable for ER recruitment but essential for ER export of GPCRs. Structural analysis indicates UFSP2 and C1orf27 are diverged from a C. elegans ODR8-like protein.","method":"Co-immunoprecipitation (multi-protein complex), UFSP2 recruitment assay, GPCR trafficking assays, catalytic mutant analysis, structural analysis","journal":"iScience","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP for complex formation, catalytic mutant epistasis, trafficking assays, structural analysis; multiple orthogonal methods","pmids":["42088365"],"is_preprint":false}],"current_model":"ODR4 (C1orf27) is a conserved tail-anchored ER transmembrane protein that forms a complex with UFSP2/UfSP2 (ODR-8 in C. elegans) at the ER membrane; this complex physically binds nascent GPCRs via their intracellular loops and C-terminus, directs them to the ufmylation system, and controls their ER-to-Golgi-to-surface anterograde transport in a manner that requires UFSP2 catalytic activity for ER export but not for ER recruitment, with the protease-independent scaffolding function being essential for GPCR biogenesis and cilia localization across species."},"narrative":{"mechanistic_narrative":"ODR4 (C1orf27) is a conserved tail-anchored ER transmembrane protein that functions as a dedicated biogenesis factor for G-protein-coupled receptors, controlling their folding and anterograde trafficking from the ER to the cell surface [PMID:9590179, PMID:24603482, PMID:35551911]. First identified in C. elegans, where loss of odr-4 selectively blocks delivery of a subset of seven-transmembrane chemoreceptors—but not ion channels or G-alpha proteins—to sensory cilia, it acts cell-autonomously on intracellular membranes of chemosensory neurons [PMID:9590179], and this requirement extends to chemoreceptor presentation underlying nociceptive and social-feeding behaviors [PMID:12410303, PMID:16581509]. ODR4 physically binds nascent GPCRs and partners with the Ufm1-specific protease UFSP2 (ODR-8 in C. elegans) in a complex at the ER membrane, where ODR4 is required to recruit UFSP2 to the ER [PMID:24603482, PMID:42088365]. In human cells, ODR4 associates with GPCRs via their third intracellular loop and C-terminus and is required for their ER-to-Golgi export and surface delivery: depletion markedly slows ER export of newly synthesized α2A-adrenergic receptor and inhibits surface transport of α2A-AR, β2-AR, and dopamine D2 receptor, but not EGFR [PMID:35551911]. The ODR4–UFSP2 complex incorporates cargo GPCRs into a multi-protein assembly in which UFSP2 catalytic activity is dispensable for ER recruitment of the complex but essential for GPCR ER export, establishing ODR4 itself as the scaffolding subunit whose GPCR-binding function drives biogenesis [PMID:42088365]. The conserved mammalian role was supported by heterologous trafficking of an olfactory receptor to the plasma membrane [PMID:11060288].","teleology":[{"year":1998,"claim":"Established that ODR-4 is a membrane protein required specifically for delivering seven-transmembrane odorant receptors to cilia, defining the first dedicated GPCR-class trafficking/folding factor.","evidence":"Genetic loss-of-function of odr-4/odr-8 with cell-autonomous rescue and subcellular localization imaging in C. elegans chemosensory neurons","pmids":["9590179"],"confidence":"High","gaps":["Molecular mechanism (folding vs. transport) not distinguished","No biochemical interaction partners identified","Human ortholog function untested"]},{"year":2000,"claim":"Showed the GPCR-trafficking role is conserved in mammals, as the human homolog promotes plasma membrane delivery of a rat olfactory receptor in heterologous cells.","evidence":"Heterologous expression of ODR-4 in odora and CHO cells with plasma membrane trafficking assay","pmids":["11060288"],"confidence":"Medium","gaps":["Single receptor tested in overexpression","No endogenous loss-of-function in mammalian cells","No interacting partners defined"]},{"year":2002,"claim":"Connected ODR-4-dependent chemoreceptor localization to physiological behavior by placing it genetically relative to the osm-3 pathway in social feeding.","evidence":"Genetic epistasis (odr-4; osm-3 double mutants), neuron ablation, and behavioral assays in C. elegans","pmids":["12410303"],"confidence":"Medium","gaps":["Behavioral readout does not resolve molecular trafficking step","Direct receptor cargoes not enumerated"]},{"year":2006,"claim":"Reinforced that ODR-4 enables functional chemosensory receptor presentation at cilia, here for O2 avoidance and aggregation via TRP channel-coupled neurons.","evidence":"Genetic loss-of-function and behavioral assays (O2 avoidance, aggregation) in C. elegans","pmids":["16581509"],"confidence":"Medium","gaps":["Mechanism of receptor presentation not biochemically defined","Does not address mammalian relevance"]},{"year":2014,"claim":"Defined ODR-4 as a tail-anchored ER protein that physically binds both its GPCR cargo and the protease UfSP2/ODR-8, and showed the protease's catalytic activity and the ufmylation pathway are dispensable for GPCR cilia trafficking.","evidence":"Reciprocal Co-IP of ODR-4/ODR-8/ODR-10 at the ER, genetic rescue with catalytic-dead ODR-8, ufm-1 deletion epistasis, and localization; conserved ODR4–UfSP2 interaction shown for human orthologs","pmids":["24603482"],"confidence":"High","gaps":["Why a protease partner is required if catalysis is dispensable left unresolved","Direction of ER export step not kinetically measured","Stoichiometry/structure of the complex unknown"]},{"year":2022,"claim":"Demonstrated endogenous human C1orf27 is required for ER-to-Golgi export and surface delivery of multiple GPCRs and mapped its binding to GPCR intracellular loop 3 and C-terminus, establishing cargo specificity.","evidence":"siRNA knockdown, CRISPR-Cas9 knockout, RUSH ER-to-Golgi kinetics, BRET, ELISA surface assays, and Co-IP domain mapping in human cells","pmids":["35551911"],"confidence":"High","gaps":["Role of UFSP2 in the human pathway not addressed in this study","Whether binding is direct vs. complex-mediated not fully separated","Structural basis of intracellular-loop recognition unknown"]},{"year":2026,"claim":"Integrated the human pathway by showing C1orf27 recruits UFSP2 to the ER, that C1orf27–UFSP2–GPCR form a multi-protein complex, and that UFSP2 catalysis is dispensable for recruitment but essential for GPCR ER export.","evidence":"Co-IP of the multi-protein complex, UFSP2 ER-recruitment assay, catalytic-mutant epistasis, GPCR trafficking assays, and structural analysis in human cells","pmids":["42088365"],"confidence":"High","gaps":["Substrate of the essential UFSP2 catalytic step during ER export not identified","High-resolution structure of the assembled complex not resolved","How cargo handoff to COPII export machinery occurs unknown"]},{"year":null,"claim":"It remains unknown what molecular event UFSP2 catalysis drives during GPCR ER export and how the ODR4 scaffold couples cargo binding to forward COPII-mediated transport.","evidence":"","pmids":[],"confidence":"High","gaps":["No identified catalytic substrate for the essential UFSP2 step","No structure of the ODR4–UFSP2–GPCR complex","Breadth of the GPCR cargo repertoire incompletely defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,6,7]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,7]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,4,7]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[6,7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,6]}],"complexes":["ODR4–UFSP2 ER complex (ODR-4/ODR-8 in C. elegans)"],"partners":["UFSP2","ODR-8","ODR-10","ADRA2A","ADRB2","DRD2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5SWX8","full_name":"Protein odr-4 homolog","aliases":["LAG1-interacting protein","Transactivated by transforming growth factor beta protein 1"],"length_aa":454,"mass_kda":51.1,"function":"May play a role in the trafficking of a subset of G-protein coupled receptors","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q5SWX8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ODR4","classification":"Not Classified","n_dependent_lines":290,"n_total_lines":1208,"dependency_fraction":0.24006622516556292},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SEC61B","stoichiometry":0.2},{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ODR4","total_profiled":1310},"omim":[{"mim_id":"609335","title":"ODR4 GPCR LOCALIZATION FACTOR HOMOLOG; ODR4","url":"https://www.omim.org/entry/609335"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ODR4"},"hgnc":{"alias_symbol":["FLJ20505","odr-4","TTG1"],"prev_symbol":["C1orf27"]},"alphafold":{"accession":"Q5SWX8","domains":[{"cath_id":"3.40.140.10","chopping":"5-53_66-174","consensus_level":"high","plddt":91.5813,"start":5,"end":174},{"cath_id":"-","chopping":"177-233_250-262_274-404","consensus_level":"high","plddt":87.7818,"start":177,"end":404}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5SWX8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5SWX8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5SWX8-F1-predicted_aligned_error_v6.png","plddt_mean":80.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ODR4","jax_strain_url":"https://www.jax.org/strain/search?query=ODR4"},"sequence":{"accession":"Q5SWX8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5SWX8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5SWX8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5SWX8"}},"corpus_meta":[{"pmid":"10202136","id":"PMC_10202136","title":"Molecular tinkering of G protein-coupled receptors: an evolutionary success.","date":"1999","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10202136","citation_count":1146,"is_preprint":false},{"pmid":"9590179","id":"PMC_9590179","title":"Odorant receptor localization to olfactory cilia is mediated by ODR-4, a novel membrane-associated protein.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9590179","citation_count":204,"is_preprint":false},{"pmid":"12410303","id":"PMC_12410303","title":"Social feeding in Caenorhabditis elegans is induced by neurons that detect aversive stimuli.","date":"2002","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/12410303","citation_count":195,"is_preprint":false},{"pmid":"16581509","id":"PMC_16581509","title":"Behavioral motifs and neural pathways coordinating O2 responses and aggregation in C. elegans.","date":"2006","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/16581509","citation_count":105,"is_preprint":false},{"pmid":"11060288","id":"PMC_11060288","title":"Olfactory receptor trafficking involves conserved regulatory steps.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11060288","citation_count":70,"is_preprint":false},{"pmid":"14502073","id":"PMC_14502073","title":"Trafficking prerogatives of olfactory receptors.","date":"2003","source":"Neuroreport","url":"https://pubmed.ncbi.nlm.nih.gov/14502073","citation_count":61,"is_preprint":false},{"pmid":"24603482","id":"PMC_24603482","title":"An ER complex of ODR-4 and ODR-8/Ufm1 specific protease 2 promotes GPCR maturation by a Ufm1-independent mechanism.","date":"2014","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24603482","citation_count":46,"is_preprint":false},{"pmid":"33251353","id":"PMC_33251353","title":"Identification of potential biomarkers for lung adenocarcinoma.","date":"2020","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/33251353","citation_count":12,"is_preprint":false},{"pmid":"35551911","id":"PMC_35551911","title":"Human C1orf27 protein interacts with α2A-adrenergic receptor and regulates its anterograde transport.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35551911","citation_count":8,"is_preprint":false},{"pmid":"15718105","id":"PMC_15718105","title":"Ubiquitously expressed GPCR membrane-trafficking orthologs.","date":"2005","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15718105","citation_count":6,"is_preprint":false},{"pmid":"25478641","id":"PMC_25478641","title":"Analysis of various types of single-polypeptide-chain (sc) heterodimeric A₂AR/D₂R complexes and their allosteric receptor-receptor interactions.","date":"2014","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25478641","citation_count":1,"is_preprint":false},{"pmid":"41543394","id":"PMC_41543394","title":"Surface Marker Identification to Capture Live Circulating Tumor Cells in Metastatic Triple-Negative Breast Cancer.","date":"2026","source":"Cancer research communications","url":"https://pubmed.ncbi.nlm.nih.gov/41543394","citation_count":1,"is_preprint":false},{"pmid":"42088365","id":"PMC_42088365","title":"The UFSP2-C1orf27 complex positions nascent GPCRs to the ufmylation system for ER export control.","date":"2026","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/42088365","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7771,"output_tokens":2267,"usd":0.028659,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9283,"output_tokens":2945,"usd":0.06002,"stage2_stop_reason":"end_turn"},"total_usd":0.088679,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"C. elegans ODR-4 encodes a novel membrane protein expressed exclusively on intracellular membranes of chemosensory neurons, where it acts cell-autonomously to facilitate odorant receptor folding or localization to olfactory cilia. Loss of odr-4 or odr-8 prevents localization of a subset of seven-transmembrane odorant receptors (but not ion channels, G-alpha proteins, or other receptor types) to cilia.\",\n      \"method\": \"Genetic loss-of-function (odr-4 and odr-8 mutants), cell-type-specific expression analysis, subcellular localization by imaging\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function with defined cellular phenotype, cell-autonomous rescue, localization experiments; foundational paper replicated by subsequent studies\",\n      \"pmids\": [\"9590179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Mammalian ODR-4 (human homolog) facilitates trafficking of rat olfactory receptor U131 to the plasma membrane in odora and CHO cells, demonstrating a conserved role in GPCR trafficking from ER to plasma membrane across species.\",\n      \"method\": \"Heterologous expression of ODR-4 in odora and CHO cell lines, plasma membrane trafficking assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional trafficking assay in heterologous cells, single lab, multiple cell lines tested\",\n      \"pmids\": [\"11060288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ODR-4 and ODR-8 are required for localizing sensory chemoreceptors to cilia in nociceptive neurons ASH and ADL, and odr-4 mutant social feeding phenotype is suppressed by osm-3 mutations, placing odr-4 upstream or in opposition to the osm-3 pathway in regulating social feeding behavior.\",\n      \"method\": \"Genetic epistasis (odr-4; osm-3 double mutants), neuron ablation, behavioral assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in C. elegans with defined behavioral readout, single lab\",\n      \"pmids\": [\"12410303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ODR-4, together with TRP channel subunits OCR-2 and OSM-9, acts in nociceptive neurons ASH and ADL to promote avoidance of high O2 and aggregation behavior, supporting ODR-4's role in functional chemosensory receptor presentation at cilia.\",\n      \"method\": \"Genetic loss-of-function, behavioral assays (O2 avoidance, aggregation)\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined behavioral phenotype, single lab\",\n      \"pmids\": [\"16581509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ODR-4 encodes a conserved tail-anchored transmembrane protein that physically interacts with ODR-8/UfSP2 (the C. elegans ortholog of Ufm1-specific protease 2) at the ER membrane. This ODR-4/ODR-8 complex promotes folding, maturation, or ER export of GPCRs such as ODR-10. ODR-4 also physically binds the GPCR ODR-10. The human orthologs ODR4 (C1orf27) and UfSP2 also physically interact, suggesting evolutionary conservation. The protease activity of ODR-8/UfSP2 is dispensable for GPCR trafficking, and ufm-1 deletion does not alter chemoreceptor cilia trafficking.\",\n      \"method\": \"Co-immunoprecipitation (physical interaction between ODR-4, ODR-8, and ODR-10 at ER), genetic rescue with catalytic-dead ODR-8 mutants, ufm-1 deletion epistasis, subcellular localization\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis with active-site mutagenesis, localization, and deletion of pathway component; multiple orthogonal methods in single study\",\n      \"pmids\": [\"24603482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A full-length human cDNA homologous to C. elegans ODR-4 was isolated (C1orf27/FLJ20505), expressed in 41 of 44 human, mouse, and rat tissues, and shares predicted structural features with orthologs, suggesting a conserved ubiquitous function in GPCR trafficking.\",\n      \"method\": \"RecA-based gene enrichment, cDNA cloning, tissue expression analysis, bioinformatic structural comparison\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — gene identification and expression survey without direct functional assay for the human protein\",\n      \"pmids\": [\"15718105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Human C1orf27 (ODR4 ortholog) physically associates with α2A-adrenergic receptor (α2A-AR) specifically via its third intracellular loop and C-terminus. siRNA knockdown or CRISPR-Cas9 knockout of C1orf27 markedly impedes ER-to-Golgi export kinetics of newly synthesized α2A-AR (half-time prolonged >65%) and significantly inhibits surface transport of α2A-AR, β2-AR, and dopamine D2 receptor, but not epidermal growth factor receptor.\",\n      \"method\": \"siRNA knockdown, CRISPR-Cas9 knockout, RUSH (retention using selective hooks) ER-to-Golgi export assay, bioluminescence resonance energy transfer (BRET) assay, ELISA surface transport assay, co-immunoprecipitation mapping of interaction domains\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO+KD, RUSH kinetics, BRET, ELISA, Co-IP domain mapping) in single lab demonstrating specific GPCR trafficking function\",\n      \"pmids\": [\"35551911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Human C1orf27 (ODR4) and UFSP2 form a complex at the ER membrane; UFSP2 requires C1orf27 for its ER recruitment. C1orf27, UFSP2, and cargo GPCRs form a multi-protein complex, and GPCR interaction with C1orf27 is required for their ER export and forward delivery to the Golgi and cell surface. UFSP2 catalytic activity is dispensable for ER recruitment but essential for ER export of GPCRs. Structural analysis indicates UFSP2 and C1orf27 are diverged from a C. elegans ODR8-like protein.\",\n      \"method\": \"Co-immunoprecipitation (multi-protein complex), UFSP2 recruitment assay, GPCR trafficking assays, catalytic mutant analysis, structural analysis\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP for complex formation, catalytic mutant epistasis, trafficking assays, structural analysis; multiple orthogonal methods\",\n      \"pmids\": [\"42088365\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ODR4 (C1orf27) is a conserved tail-anchored ER transmembrane protein that forms a complex with UFSP2/UfSP2 (ODR-8 in C. elegans) at the ER membrane; this complex physically binds nascent GPCRs via their intracellular loops and C-terminus, directs them to the ufmylation system, and controls their ER-to-Golgi-to-surface anterograde transport in a manner that requires UFSP2 catalytic activity for ER export but not for ER recruitment, with the protease-independent scaffolding function being essential for GPCR biogenesis and cilia localization across species.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ODR4 (C1orf27) is a conserved tail-anchored ER transmembrane protein that functions as a dedicated biogenesis factor for G-protein-coupled receptors, controlling their folding and anterograde trafficking from the ER to the cell surface [#0, #4, #6]. First identified in C. elegans, where loss of odr-4 selectively blocks delivery of a subset of seven-transmembrane chemoreceptors—but not ion channels or G-alpha proteins—to sensory cilia, it acts cell-autonomously on intracellular membranes of chemosensory neurons [#0], and this requirement extends to chemoreceptor presentation underlying nociceptive and social-feeding behaviors [#2, #3]. ODR4 physically binds nascent GPCRs and partners with the Ufm1-specific protease UFSP2 (ODR-8 in C. elegans) in a complex at the ER membrane, where ODR4 is required to recruit UFSP2 to the ER [#4, #7]. In human cells, ODR4 associates with GPCRs via their third intracellular loop and C-terminus and is required for their ER-to-Golgi export and surface delivery: depletion markedly slows ER export of newly synthesized α2A-adrenergic receptor and inhibits surface transport of α2A-AR, β2-AR, and dopamine D2 receptor, but not EGFR [#6]. The ODR4–UFSP2 complex incorporates cargo GPCRs into a multi-protein assembly in which UFSP2 catalytic activity is dispensable for ER recruitment of the complex but essential for GPCR ER export, establishing ODR4 itself as the scaffolding subunit whose GPCR-binding function drives biogenesis [#7]. The conserved mammalian role was supported by heterologous trafficking of an olfactory receptor to the plasma membrane [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that ODR-4 is a membrane protein required specifically for delivering seven-transmembrane odorant receptors to cilia, defining the first dedicated GPCR-class trafficking/folding factor.\",\n      \"evidence\": \"Genetic loss-of-function of odr-4/odr-8 with cell-autonomous rescue and subcellular localization imaging in C. elegans chemosensory neurons\",\n      \"pmids\": [\"9590179\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism (folding vs. transport) not distinguished\", \"No biochemical interaction partners identified\", \"Human ortholog function untested\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed the GPCR-trafficking role is conserved in mammals, as the human homolog promotes plasma membrane delivery of a rat olfactory receptor in heterologous cells.\",\n      \"evidence\": \"Heterologous expression of ODR-4 in odora and CHO cells with plasma membrane trafficking assay\",\n      \"pmids\": [\"11060288\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single receptor tested in overexpression\", \"No endogenous loss-of-function in mammalian cells\", \"No interacting partners defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected ODR-4-dependent chemoreceptor localization to physiological behavior by placing it genetically relative to the osm-3 pathway in social feeding.\",\n      \"evidence\": \"Genetic epistasis (odr-4; osm-3 double mutants), neuron ablation, and behavioral assays in C. elegans\",\n      \"pmids\": [\"12410303\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Behavioral readout does not resolve molecular trafficking step\", \"Direct receptor cargoes not enumerated\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Reinforced that ODR-4 enables functional chemosensory receptor presentation at cilia, here for O2 avoidance and aggregation via TRP channel-coupled neurons.\",\n      \"evidence\": \"Genetic loss-of-function and behavioral assays (O2 avoidance, aggregation) in C. elegans\",\n      \"pmids\": [\"16581509\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of receptor presentation not biochemically defined\", \"Does not address mammalian relevance\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined ODR-4 as a tail-anchored ER protein that physically binds both its GPCR cargo and the protease UfSP2/ODR-8, and showed the protease's catalytic activity and the ufmylation pathway are dispensable for GPCR cilia trafficking.\",\n      \"evidence\": \"Reciprocal Co-IP of ODR-4/ODR-8/ODR-10 at the ER, genetic rescue with catalytic-dead ODR-8, ufm-1 deletion epistasis, and localization; conserved ODR4–UfSP2 interaction shown for human orthologs\",\n      \"pmids\": [\"24603482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why a protease partner is required if catalysis is dispensable left unresolved\", \"Direction of ER export step not kinetically measured\", \"Stoichiometry/structure of the complex unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated endogenous human C1orf27 is required for ER-to-Golgi export and surface delivery of multiple GPCRs and mapped its binding to GPCR intracellular loop 3 and C-terminus, establishing cargo specificity.\",\n      \"evidence\": \"siRNA knockdown, CRISPR-Cas9 knockout, RUSH ER-to-Golgi kinetics, BRET, ELISA surface assays, and Co-IP domain mapping in human cells\",\n      \"pmids\": [\"35551911\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of UFSP2 in the human pathway not addressed in this study\", \"Whether binding is direct vs. complex-mediated not fully separated\", \"Structural basis of intracellular-loop recognition unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Integrated the human pathway by showing C1orf27 recruits UFSP2 to the ER, that C1orf27–UFSP2–GPCR form a multi-protein complex, and that UFSP2 catalysis is dispensable for recruitment but essential for GPCR ER export.\",\n      \"evidence\": \"Co-IP of the multi-protein complex, UFSP2 ER-recruitment assay, catalytic-mutant epistasis, GPCR trafficking assays, and structural analysis in human cells\",\n      \"pmids\": [\"42088365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate of the essential UFSP2 catalytic step during ER export not identified\", \"High-resolution structure of the assembled complex not resolved\", \"How cargo handoff to COPII export machinery occurs unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown what molecular event UFSP2 catalysis drives during GPCR ER export and how the ODR4 scaffold couples cargo binding to forward COPII-mediated transport.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No identified catalytic substrate for the essential UFSP2 step\", \"No structure of the ODR4–UFSP2–GPCR complex\", \"Breadth of the GPCR cargo repertoire incompletely defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 6, 7]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 4, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [6, 7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"complexes\": [\"ODR4–UFSP2 ER complex (ODR-4/ODR-8 in C. elegans)\"],\n    \"partners\": [\"UFSP2\", \"ODR-8\", \"ODR-10\", \"ADRA2A\", \"ADRB2\", \"DRD2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}