{"gene":"ELMOD1","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2007,"finding":"ELMOD1 was identified as having GTPase-activating protein (GAP) activity toward ARL2, consistent with its ELMO domain. It was purified alongside ELMOD2 from bovine testis and shown to stimulate GTP hydrolysis on ARL2.","method":"In vitro GAP activity assay with purified protein from bovine testis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct biochemical GAP assay on purified protein, foundational discovery paper","pmids":["17452337"],"is_preprint":false},{"year":2012,"finding":"The ELMO domain of ELMOD1 contains a conserved arginine residue critical for GAP activity toward ARF family GTPases. Mutagenesis of this residue abolished both biochemical and cellular GAP activity. ELMOD1 was also shown to function as an ARF family GAP at the Golgi.","method":"Phylogenetic analysis, sequence alignment, three independent GAP activity assays, active-site mutagenesis, cellular localization studies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal biochemical and cellular assays plus mutagenesis in a single study","pmids":["23014990"],"is_preprint":false},{"year":2012,"finding":"Loss-of-function mutations in mouse Elmod1 (rda and rda2J alleles) cause elongation and fusion of inner hair cell stereocilia and progressive degeneration of outer hair cell stereocilia, linking ELMOD1-mediated small GTPase signaling to actin cytoskeleton dynamics in hair cell stereocilia.","method":"Positional cloning of spontaneous mouse mutants, morphological analysis of hair cell stereocilia in mutant mice","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — genetic loss-of-function with clear cellular phenotype, independent alleles confirming specificity","pmids":["22558334"],"is_preprint":false},{"year":2014,"finding":"Recombinant ELMOD1, ELMOD2, and ELMOD3 display distinct specificities as GAPs for six ARF family members. The sigma-1 receptor (S1R) was identified as a novel regulator of ELMOD1 GAP activity: direct binding of S1R to ELMOD1 results in loss of GAP activity.","method":"Overexpression in HEK293T cells, purification, in vitro GAP activity assays, direct binding assay (S1R–ELMOD1 interaction)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct biochemical reconstitution with purified proteins, multiple substrates tested, inhibition by binding partner demonstrated","pmids":["24616099"],"is_preprint":false},{"year":2017,"finding":"ELMOD1 acts as a GAP for ARF6 specifically in vestibular hair cells. In Elmod1-null (rda/rda) mice, the ARF6 GTP/GDP ratio was significantly elevated; cuticular plates degenerated with vesicle invasion; apical membranes lifted and stereocilia elongated and fused. Membrane trafficking measured by FM1-43 dye was altered, consistent with ELMOD1 converting ARF6 to its GDP-bound form to stabilize apical actin and membrane structures.","method":"Knockout mouse analysis (rda/rda), ARF6 GTP/GDP ratio measurement, FM1-43 membrane trafficking assay, morphological analysis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1–2 — direct measurement of ARF6 activation state in vivo combined with multiple cellular phenotype readouts","pmids":["29222402"],"is_preprint":false},{"year":2021,"finding":"Deletion of Elmod1 in immortalized mouse embryonic fibroblasts reduces primary cilia formation, causes loss of a subset of ciliary proteins from cilia, and leads to accumulation of ciliary proteins at the Golgi, indicating compromised Golgi-to-cilia trafficking. These phenotypes are reversed by expression of activating mutants of ARL3 or ARL16, placing ELMOD1 upstream of ARL3/ARL16 in ciliogenesis regulation.","method":"CRISPR/Cas9 knockout MEFs, immunofluorescence for ciliary markers, epistasis with constitutively active ARL3/ARL16","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype plus genetic epistasis placing ELMOD1 in pathway","pmids":["34818063"],"is_preprint":false},{"year":2021,"finding":"GP130 interacts with APLNR at the plasma membrane of glioblastoma stem-like cells and mediates APLNR surface availability via ELMOD1, implicating ELMOD1 in ARF-mediated endovesicular trafficking at the plasma membrane.","method":"Co-immunoprecipitation, functional receptor surface assays in glioblastoma stem-like cells","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 3 — single study with co-IP and functional readout but mechanistic role of ELMOD1 only partially characterized","pmids":["34287648"],"is_preprint":false},{"year":2023,"finding":"The C. elegans ELMOD1-3 ortholog ELMD-1, together with WDR-31 and RP-2, regulates intraflagellar transport (IFT) complex assembly and BBSome entry/exit at cilia. Triple loss-of-function causes accumulation of IFT-B components and KIF17 kinesin in cilia, increased anterograde IFT speed in the middle segment, and leakage of non-ciliary protein into cilia.","method":"C. elegans genetics (triple mutant), IFT particle tracking by live imaging, immunofluorescence for ciliary components","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in C. elegans ortholog with live IFT imaging, but triple mutant complicates attribution to ELMD-1 alone","pmids":["37208194"],"is_preprint":false}],"current_model":"ELMOD1 is an ELMO-domain-containing GTPase-activating protein (GAP) that stimulates GTP hydrolysis on ARF family GTPases (principally ARF6, and also ARL2 and other ARFs) via a conserved catalytic arginine residue; in hair cells it converts ARF6 to its GDP-bound form to stabilize apical actin structures and the hair bundle, while in fibroblasts it acts at the Golgi and cilia to promote Golgi-to-cilia protein trafficking and ciliogenesis, with its GAP activity negatively regulated by direct binding of the sigma-1 receptor."},"narrative":{"teleology":[{"year":2007,"claim":"Establishing that ELMOD1 possesses intrinsic GAP activity toward ARL2 answered the fundamental question of whether ELMO-domain proteins are bona fide GTPase-activating proteins rather than scaffolding factors.","evidence":"In vitro GAP assay with protein purified from bovine testis","pmids":["17452337"],"confidence":"High","gaps":["Substrate specificity across the broader ARF family was untested","Catalytic residues were not yet identified","Physiological relevance in cells or tissues was unknown"]},{"year":2012,"claim":"Identification of a conserved catalytic arginine essential for GAP activity and demonstration that ELMOD1 functions as an ARF-family GAP at the Golgi defined the enzymatic mechanism and a cellular site of action.","evidence":"Phylogenetic analysis, active-site mutagenesis abolishing GAP activity in biochemical and cellular assays, Golgi localization studies","pmids":["23014990"],"confidence":"High","gaps":["Which specific ARF substrates are engaged at the Golgi was not resolved","No structural model of the ELMO domain–ARF interface existed"]},{"year":2012,"claim":"Positional cloning of two independent mouse mutant alleles (rda, rda2J) linked ELMOD1 loss to stereocilia elongation, fusion, and progressive hair cell degeneration, establishing the first in vivo function for ELMOD1 in actin-based hair bundle morphogenesis.","evidence":"Spontaneous mouse mutant mapping, morphological analysis of inner and outer hair cell stereocilia","pmids":["22558334"],"confidence":"High","gaps":["The specific GTPase substrate in hair cells was not identified","Whether actin defects were cell-autonomous was not determined"]},{"year":2014,"claim":"Demonstration that ELMOD1–3 have distinct ARF-family substrate specificities, and that the sigma-1 receptor directly binds and inhibits ELMOD1 GAP activity, revealed a regulatory mechanism controlling ELMOD1 function.","evidence":"Purified recombinant proteins from HEK293T cells, in vitro GAP assays against six ARFs, direct binding assay for S1R–ELMOD1","pmids":["24616099"],"confidence":"High","gaps":["Physiological contexts where S1R regulates ELMOD1 in vivo were not defined","Structural basis of S1R-mediated inhibition was not resolved"]},{"year":2017,"claim":"Direct measurement of elevated ARF6-GTP in Elmod1-null hair cells, combined with cuticular plate degeneration and altered membrane trafficking, identified ARF6 as the critical physiological substrate and linked GAP activity to apical membrane and actin stabilization.","evidence":"Knockout mouse (rda/rda), ARF6 GTP/GDP ratio measurement, FM1-43 membrane trafficking assay, ultrastructural analysis","pmids":["29222402"],"confidence":"High","gaps":["Whether other ARF substrates contribute to the hair cell phenotype was not excluded","Downstream effectors of ARF6-GDP in hair cells were not identified"]},{"year":2021,"claim":"ELMOD1 deletion in fibroblasts revealed a second major cellular function—promoting ciliogenesis by enabling Golgi-to-cilia protein trafficking—and epistasis with activated ARL3/ARL16 placed ELMOD1 upstream in this pathway.","evidence":"CRISPR/Cas9 knockout MEFs, immunofluorescence for ciliary markers, rescue by constitutively active ARL3 and ARL16","pmids":["34818063"],"confidence":"High","gaps":["Whether ELMOD1 acts directly as a GAP for ARL3 or ARL16 in this context was not shown","The identity of the cargo trapped at the Golgi was only partially characterized"]},{"year":2021,"claim":"Identification of ELMOD1 as a mediator of APLNR surface availability downstream of GP130 extended its role to receptor endovesicular trafficking at the plasma membrane in glioblastoma stem-like cells.","evidence":"Co-immunoprecipitation and receptor surface assays in glioblastoma stem-like cells","pmids":["34287648"],"confidence":"Medium","gaps":["ELMOD1's direct interaction with GP130 or APLNR was not demonstrated","The specific ARF substrate mediating this trafficking event was not identified","Findings are from a single study in a specialized cell type"]},{"year":2023,"claim":"Work in C. elegans showed the ELMOD1-3 ortholog ELMD-1 cooperates with WDR-31 and RP-2 to regulate IFT complex assembly and BBSome-dependent ciliary gating, broadening ELMOD1's ciliary role to intraflagellar transport control.","evidence":"C. elegans triple mutant genetics, live IFT particle tracking, immunofluorescence for ciliary components","pmids":["37208194"],"confidence":"Medium","gaps":["Triple mutant design complicates attribution of phenotypes to ELMD-1 alone","Whether this IFT regulatory role is conserved in mammalian ELMOD1 has not been tested"]},{"year":null,"claim":"Key open questions include the structural basis of ELMOD1 GAP activity and S1R-mediated inhibition, whether ELMOD1 directly acts as a GAP for ARL3/ARL16 in the ciliogenesis pathway, and the identity of downstream effectors linking ARF6-GDP to actin stabilization in hair cells.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure of ELMOD1 or its complex with any ARF substrate","Direct GAP activity of ELMOD1 toward ARL3 or ARL16 has not been biochemically demonstrated","Downstream actin effectors in hair cells remain unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3,4]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1,5]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[5,7]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[2,4]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[4,5,6]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[5,7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,3,4]}],"complexes":[],"partners":["ARF6","ARL2","SIGMAR1","ARL3","ARL16"],"other_free_text":[]},"mechanistic_narrative":"ELMOD1 is an ELMO-domain-containing GTPase-activating protein (GAP) that stimulates GTP hydrolysis on ARF family GTPases—principally ARF6 and ARL2—through a conserved catalytic arginine residue, thereby controlling actin cytoskeleton integrity, membrane trafficking, and ciliogenesis [PMID:17452337, PMID:23014990, PMID:24616099]. In vestibular and cochlear hair cells, ELMOD1 converts ARF6 to its GDP-bound form to stabilize the cuticular plate and stereocilia; loss-of-function mutations in mice cause elevated ARF6-GTP, stereocilia elongation and fusion, cuticular plate degeneration, and progressive hearing loss [PMID:22558334, PMID:29222402]. In fibroblasts, ELMOD1 deletion impairs primary cilia formation by blocking Golgi-to-cilia trafficking of ciliary proteins, a phenotype rescued by activated ARL3 or ARL16, placing ELMOD1 upstream of these GTPases in the ciliogenesis pathway [PMID:34818063]. The sigma-1 receptor directly binds ELMOD1 and inhibits its GAP activity, providing a mechanism for regulated control of ARF-family signaling [PMID:24616099]."},"prefetch_data":{"uniprot":{"accession":"Q8N336","full_name":"ELMO domain-containing protein 1","aliases":[],"length_aa":334,"mass_kda":39.1,"function":"Acts as a GTPase-activating protein (GAP) toward guanine nucleotide exchange factors like ARL2, ARL3, ARF1 and ARF6, but not for GTPases outside the Arf family","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8N336/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ELMOD1","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ELMOD1","total_profiled":1310},"omim":[{"mim_id":"615456","title":"ELMO/CED12 DOMAIN-CONTAINING PROTEIN 1; ELMOD1","url":"https://www.omim.org/entry/615456"},{"mim_id":"615427","title":"ELMO/CED12 DOMAIN-CONTAINING PROTEIN 3; ELMOD3","url":"https://www.omim.org/entry/615427"},{"mim_id":"601175","title":"ADP-RIBOSYLATION FACTOR-LIKE GTPase 2; ARL2","url":"https://www.omim.org/entry/601175"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":51.8},{"tissue":"pituitary gland","ntpm":20.0},{"tissue":"retina","ntpm":30.2},{"tissue":"skin 1","ntpm":27.3}],"url":"https://www.proteinatlas.org/search/ELMOD1"},"hgnc":{"alias_symbol":["DKFZp547C176"],"prev_symbol":[]},"alphafold":{"accession":"Q8N336","domains":[{"cath_id":"-","chopping":"35-124","consensus_level":"high","plddt":95.1494,"start":35,"end":124},{"cath_id":"-","chopping":"129-334","consensus_level":"high","plddt":90.5897,"start":129,"end":334},{"cath_id":"1.20.5","chopping":"2-28","consensus_level":"medium","plddt":86.7519,"start":2,"end":28}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N336","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N336-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N336-F1-predicted_aligned_error_v6.png","plddt_mean":90.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ELMOD1","jax_strain_url":"https://www.jax.org/strain/search?query=ELMOD1"},"sequence":{"accession":"Q8N336","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N336.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N336/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N336"}},"corpus_meta":[{"pmid":"24523945","id":"PMC_24523945","title":"Functionally enigmatic genes: a case study of the brain ignorome.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24523945","citation_count":78,"is_preprint":false},{"pmid":"17452337","id":"PMC_17452337","title":"ELMOD2 is an Arl2 GTPase-activating protein that also acts on Arfs.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17452337","citation_count":73,"is_preprint":false},{"pmid":"23014990","id":"PMC_23014990","title":"ELMO domains, evolutionary and functional characterization of a novel GTPase-activating protein (GAP) domain for Arf protein family GTPases.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23014990","citation_count":55,"is_preprint":false},{"pmid":"24616099","id":"PMC_24616099","title":"Characterization of recombinant ELMOD (cell engulfment and motility domain) proteins as GTPase-activating proteins (GAPs) for ARF family GTPases.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24616099","citation_count":47,"is_preprint":false},{"pmid":"22558334","id":"PMC_22558334","title":"Mutations of the mouse ELMO domain containing 1 gene (Elmod1) link small GTPase signaling to actin cytoskeleton dynamics in hair cell stereocilia.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22558334","citation_count":32,"is_preprint":false},{"pmid":"33893326","id":"PMC_33893326","title":"Elevated expression of the adhesion GPCR ADGRL4/ELTD1 promotes endothelial sprouting angiogenesis without activating canonical GPCR signalling.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33893326","citation_count":27,"is_preprint":false},{"pmid":"32814070","id":"PMC_32814070","title":"The Rac2 GTPase contributes to cathepsin H-mediated protection against cytokine-induced apoptosis in insulin-secreting cells.","date":"2020","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/32814070","citation_count":16,"is_preprint":false},{"pmid":"35065650","id":"PMC_35065650","title":"Genome-wide analysis of cell-Free DNA methylation profiling with MeDIP-seq identified potential biomarkers for colorectal cancer.","date":"2022","source":"World journal of surgical oncology","url":"https://pubmed.ncbi.nlm.nih.gov/35065650","citation_count":15,"is_preprint":false},{"pmid":"29222402","id":"PMC_29222402","title":"ELMOD1 Stimulates ARF6-GTP Hydrolysis to Stabilize Apical Structures in Developing Vestibular Hair Cells.","date":"2017","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/29222402","citation_count":12,"is_preprint":false},{"pmid":"34818063","id":"PMC_34818063","title":"The ARF GAPs ELMOD1 and ELMOD3 act at the Golgi and cilia to regulate ciliogenesis and ciliary protein traffic.","date":"2021","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/34818063","citation_count":11,"is_preprint":false},{"pmid":"39725721","id":"PMC_39725721","title":"High-resolution DNA methylation changes reveal biomarkers of heart failure with preserved ejection fraction versus reduced ejection fraction.","date":"2024","source":"Basic research in cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/39725721","citation_count":10,"is_preprint":false},{"pmid":"31327155","id":"PMC_31327155","title":"ELMO Domain Containing 1 (ELMOD1) Gene Mutation Is Associated with Mental Retardation and Autism Spectrum Disorder.","date":"2019","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/31327155","citation_count":8,"is_preprint":false},{"pmid":"37208194","id":"PMC_37208194","title":"WDR31 displays functional redundancy with GTPase-activating proteins (GAPs) ELMOD and RP2 in regulating IFT complex and recruiting the BBSome to cilium.","date":"2023","source":"Life science alliance","url":"https://pubmed.ncbi.nlm.nih.gov/37208194","citation_count":5,"is_preprint":false},{"pmid":"34287648","id":"PMC_34287648","title":"The glycoprotein GP130 governs the surface presentation of the G protein-coupled receptor APLNR.","date":"2021","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/34287648","citation_count":4,"is_preprint":false},{"pmid":"37437553","id":"PMC_37437553","title":"Genome-Wide Association Studies for Albuminuria of Nondiabetic Taiwanese Population.","date":"2023","source":"American journal of nephrology","url":"https://pubmed.ncbi.nlm.nih.gov/37437553","citation_count":3,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9177,"output_tokens":1968,"usd":0.028525},"stage2":{"model":"claude-opus-4-6","input_tokens":5244,"output_tokens":2368,"usd":0.12813},"total_usd":0.156655,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"ELMOD1 was identified as having GTPase-activating protein (GAP) activity toward ARL2, consistent with its ELMO domain. It was purified alongside ELMOD2 from bovine testis and shown to stimulate GTP hydrolysis on ARL2.\",\n      \"method\": \"In vitro GAP activity assay with purified protein from bovine testis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biochemical GAP assay on purified protein, foundational discovery paper\",\n      \"pmids\": [\"17452337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The ELMO domain of ELMOD1 contains a conserved arginine residue critical for GAP activity toward ARF family GTPases. Mutagenesis of this residue abolished both biochemical and cellular GAP activity. ELMOD1 was also shown to function as an ARF family GAP at the Golgi.\",\n      \"method\": \"Phylogenetic analysis, sequence alignment, three independent GAP activity assays, active-site mutagenesis, cellular localization studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal biochemical and cellular assays plus mutagenesis in a single study\",\n      \"pmids\": [\"23014990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Loss-of-function mutations in mouse Elmod1 (rda and rda2J alleles) cause elongation and fusion of inner hair cell stereocilia and progressive degeneration of outer hair cell stereocilia, linking ELMOD1-mediated small GTPase signaling to actin cytoskeleton dynamics in hair cell stereocilia.\",\n      \"method\": \"Positional cloning of spontaneous mouse mutants, morphological analysis of hair cell stereocilia in mutant mice\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with clear cellular phenotype, independent alleles confirming specificity\",\n      \"pmids\": [\"22558334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Recombinant ELMOD1, ELMOD2, and ELMOD3 display distinct specificities as GAPs for six ARF family members. The sigma-1 receptor (S1R) was identified as a novel regulator of ELMOD1 GAP activity: direct binding of S1R to ELMOD1 results in loss of GAP activity.\",\n      \"method\": \"Overexpression in HEK293T cells, purification, in vitro GAP activity assays, direct binding assay (S1R–ELMOD1 interaction)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biochemical reconstitution with purified proteins, multiple substrates tested, inhibition by binding partner demonstrated\",\n      \"pmids\": [\"24616099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ELMOD1 acts as a GAP for ARF6 specifically in vestibular hair cells. In Elmod1-null (rda/rda) mice, the ARF6 GTP/GDP ratio was significantly elevated; cuticular plates degenerated with vesicle invasion; apical membranes lifted and stereocilia elongated and fused. Membrane trafficking measured by FM1-43 dye was altered, consistent with ELMOD1 converting ARF6 to its GDP-bound form to stabilize apical actin and membrane structures.\",\n      \"method\": \"Knockout mouse analysis (rda/rda), ARF6 GTP/GDP ratio measurement, FM1-43 membrane trafficking assay, morphological analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct measurement of ARF6 activation state in vivo combined with multiple cellular phenotype readouts\",\n      \"pmids\": [\"29222402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Deletion of Elmod1 in immortalized mouse embryonic fibroblasts reduces primary cilia formation, causes loss of a subset of ciliary proteins from cilia, and leads to accumulation of ciliary proteins at the Golgi, indicating compromised Golgi-to-cilia trafficking. These phenotypes are reversed by expression of activating mutants of ARL3 or ARL16, placing ELMOD1 upstream of ARL3/ARL16 in ciliogenesis regulation.\",\n      \"method\": \"CRISPR/Cas9 knockout MEFs, immunofluorescence for ciliary markers, epistasis with constitutively active ARL3/ARL16\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype plus genetic epistasis placing ELMOD1 in pathway\",\n      \"pmids\": [\"34818063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GP130 interacts with APLNR at the plasma membrane of glioblastoma stem-like cells and mediates APLNR surface availability via ELMOD1, implicating ELMOD1 in ARF-mediated endovesicular trafficking at the plasma membrane.\",\n      \"method\": \"Co-immunoprecipitation, functional receptor surface assays in glioblastoma stem-like cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single study with co-IP and functional readout but mechanistic role of ELMOD1 only partially characterized\",\n      \"pmids\": [\"34287648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The C. elegans ELMOD1-3 ortholog ELMD-1, together with WDR-31 and RP-2, regulates intraflagellar transport (IFT) complex assembly and BBSome entry/exit at cilia. Triple loss-of-function causes accumulation of IFT-B components and KIF17 kinesin in cilia, increased anterograde IFT speed in the middle segment, and leakage of non-ciliary protein into cilia.\",\n      \"method\": \"C. elegans genetics (triple mutant), IFT particle tracking by live imaging, immunofluorescence for ciliary components\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in C. elegans ortholog with live IFT imaging, but triple mutant complicates attribution to ELMD-1 alone\",\n      \"pmids\": [\"37208194\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ELMOD1 is an ELMO-domain-containing GTPase-activating protein (GAP) that stimulates GTP hydrolysis on ARF family GTPases (principally ARF6, and also ARL2 and other ARFs) via a conserved catalytic arginine residue; in hair cells it converts ARF6 to its GDP-bound form to stabilize apical actin structures and the hair bundle, while in fibroblasts it acts at the Golgi and cilia to promote Golgi-to-cilia protein trafficking and ciliogenesis, with its GAP activity negatively regulated by direct binding of the sigma-1 receptor.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ELMOD1 is an ELMO-domain-containing GTPase-activating protein (GAP) that stimulates GTP hydrolysis on ARF family GTPases—principally ARF6 and ARL2—through a conserved catalytic arginine residue, thereby controlling actin cytoskeleton integrity, membrane trafficking, and ciliogenesis [PMID:17452337, PMID:23014990, PMID:24616099]. In vestibular and cochlear hair cells, ELMOD1 converts ARF6 to its GDP-bound form to stabilize the cuticular plate and stereocilia; loss-of-function mutations in mice cause elevated ARF6-GTP, stereocilia elongation and fusion, cuticular plate degeneration, and progressive hearing loss [PMID:22558334, PMID:29222402]. In fibroblasts, ELMOD1 deletion impairs primary cilia formation by blocking Golgi-to-cilia trafficking of ciliary proteins, a phenotype rescued by activated ARL3 or ARL16, placing ELMOD1 upstream of these GTPases in the ciliogenesis pathway [PMID:34818063]. The sigma-1 receptor directly binds ELMOD1 and inhibits its GAP activity, providing a mechanism for regulated control of ARF-family signaling [PMID:24616099].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing that ELMOD1 possesses intrinsic GAP activity toward ARL2 answered the fundamental question of whether ELMO-domain proteins are bona fide GTPase-activating proteins rather than scaffolding factors.\",\n      \"evidence\": \"In vitro GAP assay with protein purified from bovine testis\",\n      \"pmids\": [\"17452337\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Substrate specificity across the broader ARF family was untested\",\n        \"Catalytic residues were not yet identified\",\n        \"Physiological relevance in cells or tissues was unknown\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of a conserved catalytic arginine essential for GAP activity and demonstration that ELMOD1 functions as an ARF-family GAP at the Golgi defined the enzymatic mechanism and a cellular site of action.\",\n      \"evidence\": \"Phylogenetic analysis, active-site mutagenesis abolishing GAP activity in biochemical and cellular assays, Golgi localization studies\",\n      \"pmids\": [\"23014990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Which specific ARF substrates are engaged at the Golgi was not resolved\",\n        \"No structural model of the ELMO domain–ARF interface existed\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Positional cloning of two independent mouse mutant alleles (rda, rda2J) linked ELMOD1 loss to stereocilia elongation, fusion, and progressive hair cell degeneration, establishing the first in vivo function for ELMOD1 in actin-based hair bundle morphogenesis.\",\n      \"evidence\": \"Spontaneous mouse mutant mapping, morphological analysis of inner and outer hair cell stereocilia\",\n      \"pmids\": [\"22558334\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The specific GTPase substrate in hair cells was not identified\",\n        \"Whether actin defects were cell-autonomous was not determined\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstration that ELMOD1–3 have distinct ARF-family substrate specificities, and that the sigma-1 receptor directly binds and inhibits ELMOD1 GAP activity, revealed a regulatory mechanism controlling ELMOD1 function.\",\n      \"evidence\": \"Purified recombinant proteins from HEK293T cells, in vitro GAP assays against six ARFs, direct binding assay for S1R–ELMOD1\",\n      \"pmids\": [\"24616099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological contexts where S1R regulates ELMOD1 in vivo were not defined\",\n        \"Structural basis of S1R-mediated inhibition was not resolved\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Direct measurement of elevated ARF6-GTP in Elmod1-null hair cells, combined with cuticular plate degeneration and altered membrane trafficking, identified ARF6 as the critical physiological substrate and linked GAP activity to apical membrane and actin stabilization.\",\n      \"evidence\": \"Knockout mouse (rda/rda), ARF6 GTP/GDP ratio measurement, FM1-43 membrane trafficking assay, ultrastructural analysis\",\n      \"pmids\": [\"29222402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether other ARF substrates contribute to the hair cell phenotype was not excluded\",\n        \"Downstream effectors of ARF6-GDP in hair cells were not identified\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"ELMOD1 deletion in fibroblasts revealed a second major cellular function—promoting ciliogenesis by enabling Golgi-to-cilia protein trafficking—and epistasis with activated ARL3/ARL16 placed ELMOD1 upstream in this pathway.\",\n      \"evidence\": \"CRISPR/Cas9 knockout MEFs, immunofluorescence for ciliary markers, rescue by constitutively active ARL3 and ARL16\",\n      \"pmids\": [\"34818063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ELMOD1 acts directly as a GAP for ARL3 or ARL16 in this context was not shown\",\n        \"The identity of the cargo trapped at the Golgi was only partially characterized\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identification of ELMOD1 as a mediator of APLNR surface availability downstream of GP130 extended its role to receptor endovesicular trafficking at the plasma membrane in glioblastoma stem-like cells.\",\n      \"evidence\": \"Co-immunoprecipitation and receptor surface assays in glioblastoma stem-like cells\",\n      \"pmids\": [\"34287648\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"ELMOD1's direct interaction with GP130 or APLNR was not demonstrated\",\n        \"The specific ARF substrate mediating this trafficking event was not identified\",\n        \"Findings are from a single study in a specialized cell type\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Work in C. elegans showed the ELMOD1-3 ortholog ELMD-1 cooperates with WDR-31 and RP-2 to regulate IFT complex assembly and BBSome-dependent ciliary gating, broadening ELMOD1's ciliary role to intraflagellar transport control.\",\n      \"evidence\": \"C. elegans triple mutant genetics, live IFT particle tracking, immunofluorescence for ciliary components\",\n      \"pmids\": [\"37208194\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Triple mutant design complicates attribution of phenotypes to ELMD-1 alone\",\n        \"Whether this IFT regulatory role is conserved in mammalian ELMOD1 has not been tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the structural basis of ELMOD1 GAP activity and S1R-mediated inhibition, whether ELMOD1 directly acts as a GAP for ARL3/ARL16 in the ciliogenesis pathway, and the identity of downstream effectors linking ARF6-GDP to actin stabilization in hair cells.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of ELMOD1 or its complex with any ARF substrate\",\n        \"Direct GAP activity of ELMOD1 toward ARL3 or ARL16 has not been biochemically demonstrated\",\n        \"Downstream actin effectors in hair cells remain unidentified\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 3, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ARF6\",\n      \"ARL2\",\n      \"SIGMAR1\",\n      \"ARL3\",\n      \"ARL16\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}