{"gene":"EMC8","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2015,"finding":"Drosophila EMC8/9 (as part of the ER membrane protein complex, EMC) is essential for stabilization of immature rhodopsin 1 (Rh1) at an earlier step than the NinaA chaperone, and is required for stable expression of multi-pass transmembrane proteins (Rh3, Rh4, TRP, Na+K+-ATPase) but not secreted or type I single-pass transmembrane proteins; loss of EMC causes light-independent rhabdomere degeneration.","method":"Genetic screen in Drosophila photoreceptors, loss-of-function mutant analysis, subcellular localization (ER), co-immunoprecipitation (EMC3 associates with EMC1 and calnexin)","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function with defined cellular phenotype and Co-IP interactions, single lab but multiple orthogonal methods (genetics, localization, Co-IP)","pmids":["25715730"],"is_preprint":false},{"year":2023,"finding":"EMC8 (as part of the EMC complex) binds the pore-forming CaV1.2 subunit via two defined sites—a transmembrane (TM) dock and a cytoplasmic (Cyto) dock—causing partial extraction of the pore subunit and splaying open the CaVα2δ-interaction site; EMC and CaVα2δ binding to the channel are mutually exclusive, indicating EMC acts as a holdase chaperone that facilitates CaV assembly through an EMC-to-CaVα2δ hand-off involving a divalent ion-dependent step; disruption of the EMC–CaV complex compromises CaV function.","method":"Cryo-EM structure of human CaV1.2–CaVβ3–EMC complex and assembled CaV1.2–CaVβ3–CaVα2δ-1 channel; functional disruption assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures at near-atomic resolution with functional validation of disrupted complex, multiple orthogonal methods in a single rigorous study","pmids":["37196677"],"is_preprint":false},{"year":2023,"finding":"In Xenopus tropicalis, EMC8 (or its paralog EMC9, which substitutes for EMC8 in the complex) is required for neural crest development and craniofacial cartilage formation, consistent with a role in transmembrane protein topogenesis in these tissues; the phenotype mirrors EMC1 loss of function.","method":"Morpholino-based depletion in Xenopus tropicalis with craniofacial and neural crest assays","journal":"Genesis (New York, N.Y. : 2000)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single model organism depletion study with phenotypic readout but limited mechanistic resolution for EMC8 specifically vs. EMC9","pmids":["37318954"],"is_preprint":false}],"current_model":"EMC8 is a subunit of the ER membrane protein complex (EMC) that acts as a holdase chaperone for multi-pass transmembrane proteins, including voltage-gated calcium channels (CaV1.2), binding clients via defined transmembrane and cytoplasmic docking sites to facilitate their assembly and handoff to auxiliary subunits, while also being required for biogenesis of rhodopsins and other multi-pass membrane proteins and for neural crest development."},"narrative":{"mechanistic_narrative":"EMC8 is a subunit of the ER membrane protein complex (EMC) that functions in the biogenesis of multi-pass transmembrane proteins [PMID:25715730, PMID:37196677]. Within the EMC, EMC8 contributes to a holdase chaperone activity for the pore-forming CaV1.2 subunit, engaging the channel through two defined contacts—a transmembrane dock and a cytoplasmic dock—that partially extract the pore subunit and splay open the CaVα2δ-interaction site; because EMC and CaVα2δ binding are mutually exclusive, the EMC stages channel assembly via a divalent ion-dependent hand-off to CaVα2δ, and disrupting the EMC–CaV interaction compromises channel function [PMID:37196677]. Consistent with this role in transmembrane protein topogenesis, EMC (including EMC8/9) is required for the stable expression and folding of multi-pass membrane proteins such as rhodopsins, TRP, and Na+/K+-ATPase but not secreted or single-pass type I proteins, with loss causing rhabdomere degeneration in Drosophila photoreceptors [PMID:25715730]. EMC8 (interchangeably with its paralog EMC9) is also required for neural crest development and craniofacial cartilage formation [PMID:37318954].","teleology":[{"year":2015,"claim":"Established that the EMC, including the EMC8/9 module, is selectively required for biogenesis of multi-pass transmembrane proteins rather than secreted or single-pass proteins, defining its client specificity in vivo.","evidence":"Genetic loss-of-function screen in Drosophila photoreceptors with ER localization and Co-IP of EMC subunits with calnexin","pmids":["25715730"],"confidence":"Medium","gaps":["Does not separate the specific contribution of EMC8 from other EMC subunits","No structural mechanism for client recognition","Rhodopsin/TRP clients defined in Drosophila, not human EMC8"]},{"year":2023,"claim":"Resolved the molecular mechanism by which the EMC acts as a holdase, showing it binds CaV1.2 through transmembrane and cytoplasmic docks and stages assembly via a mutually exclusive hand-off to CaVα2δ.","evidence":"Cryo-EM structures of human CaV1.2–CaVβ3–EMC and assembled CaV1.2–CaVβ3–CaVα2δ-1 channel plus functional disruption assays","pmids":["37196677"],"confidence":"High","gaps":["Specific catalytic or structural role of the EMC8 subunit within the complex not isolated","Molecular identity of the divalent ion-dependent step not defined","Whether the same hand-off logic applies to other EMC clients untested"]},{"year":2023,"claim":"Linked EMC8 function to a developmental program by showing it (or paralog EMC9) is required for neural crest and craniofacial cartilage formation, connecting transmembrane protein topogenesis to organismal patterning.","evidence":"Morpholino-based depletion in Xenopus tropicalis with craniofacial and neural crest phenotypic assays","pmids":["37318954"],"confidence":"Low","gaps":["Cannot resolve EMC8-specific requirement versus EMC9 substitution","No identification of the client proteins responsible for the developmental phenotype","Morpholino depletion lacks genetic confirmation"]},{"year":null,"claim":"The specific structural and functional contribution of the EMC8 subunit itself—as distinct from the whole EMC and from its paralog EMC9—remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No EMC8-specific client repertoire established","Functional non-redundancy between EMC8 and EMC9 not delineated","No structural assignment of EMC8 contacts to client docking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1]}],"complexes":["ER membrane protein complex (EMC)"],"partners":["CACNA1C","EMC1","EMC3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43402","full_name":"ER membrane protein complex subunit 8","aliases":["Neighbor of COX4","Protein FAM158B"],"length_aa":210,"mass_kda":23.8,"function":"Part of the endoplasmic reticulum membrane protein complex (EMC) that enables the energy-independent insertion into endoplasmic reticulum membranes of newly synthesized membrane proteins (PubMed:29242231, PubMed:29809151, PubMed:30415835, PubMed:32439656, PubMed:32459176). Preferentially accommodates proteins with transmembrane domains that are weakly hydrophobic or contain destabilizing features such as charged and aromatic residues (PubMed:29242231, PubMed:29809151, PubMed:30415835). Involved in the cotranslational insertion of multi-pass membrane proteins in which stop-transfer membrane-anchor sequences become ER membrane spanning helices (PubMed:29809151, PubMed:30415835). It is also required for the post-translational insertion of tail-anchored/TA proteins in endoplasmic reticulum membranes (PubMed:29242231, PubMed:29809151). By mediating the proper cotranslational insertion of N-terminal transmembrane domains in an N-exo topology, with translocated N-terminus in the lumen of the ER, controls the topology of multi-pass membrane proteins like the G protein-coupled receptors (PubMed:30415835). By regulating the insertion of various proteins in membranes, it is indirectly involved in many cellular processes (Probable)","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/O43402/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/EMC8","classification":"Not Classified","n_dependent_lines":16,"n_total_lines":1208,"dependency_fraction":0.013245033112582781},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000131148","cell_line_id":"CID001793","localizations":[{"compartment":"er","grade":3}],"interactors":[{"gene":"EMC1","stoichiometry":10.0},{"gene":"EMC2","stoichiometry":10.0},{"gene":"EMC3","stoichiometry":10.0},{"gene":"EMC4","stoichiometry":10.0},{"gene":"EMC7","stoichiometry":10.0},{"gene":"RPS8","stoichiometry":10.0},{"gene":"CCDC47","stoichiometry":10.0},{"gene":"RPL31","stoichiometry":10.0},{"gene":"RPL11","stoichiometry":4.0},{"gene":"RPL23","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/target/CID001793","total_profiled":1310},"omim":[{"mim_id":"604886","title":"ENDOPLASMIC RETICULUM MEMBRANE PROTEIN COMPLEX, SUBUNIT 8; EMC8","url":"https://www.omim.org/entry/604886"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EMC8"},"hgnc":{"alias_symbol":["FAM158B"],"prev_symbol":["C16orf4","NOC4","C16orf2","COX4NB"]},"alphafold":{"accession":"O43402","domains":[{"cath_id":"3.40.140.10","chopping":"2-208","consensus_level":"high","plddt":91.4754,"start":2,"end":208}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43402","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43402-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43402-F1-predicted_aligned_error_v6.png","plddt_mean":91.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EMC8","jax_strain_url":"https://www.jax.org/strain/search?query=EMC8"},"sequence":{"accession":"O43402","fasta_url":"https://rest.uniprot.org/uniprotkb/O43402.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43402/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43402"}},"corpus_meta":[{"pmid":"25715730","id":"PMC_25715730","title":"dPob/EMC is essential for biosynthesis of rhodopsin and other multi-pass membrane proteins in Drosophila photoreceptors.","date":"2015","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/25715730","citation_count":104,"is_preprint":false},{"pmid":"37196677","id":"PMC_37196677","title":"EMC chaperone-CaV structure reveals an ion channel assembly intermediate.","date":"2023","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/37196677","citation_count":54,"is_preprint":false},{"pmid":"37179169","id":"PMC_37179169","title":"Effects of fecal microbiota transplant on DNA methylation in patients with systemic lupus erythematosus.","date":"2023","source":"Journal of autoimmunity","url":"https://pubmed.ncbi.nlm.nih.gov/37179169","citation_count":24,"is_preprint":false},{"pmid":"23333879","id":"PMC_23333879","title":"A small de novo 16q24.1 duplication in a woman with severe clinical features.","date":"2013","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23333879","citation_count":6,"is_preprint":false},{"pmid":"37318954","id":"PMC_37318954","title":"Expanding EMC foldopathies: Topogenesis deficits alter the neural crest.","date":"2023","source":"Genesis (New York, N.Y. : 2000)","url":"https://pubmed.ncbi.nlm.nih.gov/37318954","citation_count":3,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4580,"output_tokens":1000,"usd":0.01437,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7507,"output_tokens":1685,"usd":0.03983,"stage2_stop_reason":"end_turn"},"total_usd":0.0542,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"Drosophila EMC8/9 (as part of the ER membrane protein complex, EMC) is essential for stabilization of immature rhodopsin 1 (Rh1) at an earlier step than the NinaA chaperone, and is required for stable expression of multi-pass transmembrane proteins (Rh3, Rh4, TRP, Na+K+-ATPase) but not secreted or type I single-pass transmembrane proteins; loss of EMC causes light-independent rhabdomere degeneration.\",\n      \"method\": \"Genetic screen in Drosophila photoreceptors, loss-of-function mutant analysis, subcellular localization (ER), co-immunoprecipitation (EMC3 associates with EMC1 and calnexin)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function with defined cellular phenotype and Co-IP interactions, single lab but multiple orthogonal methods (genetics, localization, Co-IP)\",\n      \"pmids\": [\"25715730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"EMC8 (as part of the EMC complex) binds the pore-forming CaV1.2 subunit via two defined sites—a transmembrane (TM) dock and a cytoplasmic (Cyto) dock—causing partial extraction of the pore subunit and splaying open the CaVα2δ-interaction site; EMC and CaVα2δ binding to the channel are mutually exclusive, indicating EMC acts as a holdase chaperone that facilitates CaV assembly through an EMC-to-CaVα2δ hand-off involving a divalent ion-dependent step; disruption of the EMC–CaV complex compromises CaV function.\",\n      \"method\": \"Cryo-EM structure of human CaV1.2–CaVβ3–EMC complex and assembled CaV1.2–CaVβ3–CaVα2δ-1 channel; functional disruption assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures at near-atomic resolution with functional validation of disrupted complex, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"37196677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In Xenopus tropicalis, EMC8 (or its paralog EMC9, which substitutes for EMC8 in the complex) is required for neural crest development and craniofacial cartilage formation, consistent with a role in transmembrane protein topogenesis in these tissues; the phenotype mirrors EMC1 loss of function.\",\n      \"method\": \"Morpholino-based depletion in Xenopus tropicalis with craniofacial and neural crest assays\",\n      \"journal\": \"Genesis (New York, N.Y. : 2000)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single model organism depletion study with phenotypic readout but limited mechanistic resolution for EMC8 specifically vs. EMC9\",\n      \"pmids\": [\"37318954\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"EMC8 is a subunit of the ER membrane protein complex (EMC) that acts as a holdase chaperone for multi-pass transmembrane proteins, including voltage-gated calcium channels (CaV1.2), binding clients via defined transmembrane and cytoplasmic docking sites to facilitate their assembly and handoff to auxiliary subunits, while also being required for biogenesis of rhodopsins and other multi-pass membrane proteins and for neural crest development.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EMC8 is a subunit of the ER membrane protein complex (EMC) that functions in the biogenesis of multi-pass transmembrane proteins [#0, #1]. Within the EMC, EMC8 contributes to a holdase chaperone activity for the pore-forming CaV1.2 subunit, engaging the channel through two defined contacts—a transmembrane dock and a cytoplasmic dock—that partially extract the pore subunit and splay open the CaVα2δ-interaction site; because EMC and CaVα2δ binding are mutually exclusive, the EMC stages channel assembly via a divalent ion-dependent hand-off to CaVα2δ, and disrupting the EMC–CaV interaction compromises channel function [#1]. Consistent with this role in transmembrane protein topogenesis, EMC (including EMC8/9) is required for the stable expression and folding of multi-pass membrane proteins such as rhodopsins, TRP, and Na+/K+-ATPase but not secreted or single-pass type I proteins, with loss causing rhabdomere degeneration in Drosophila photoreceptors [#0]. EMC8 (interchangeably with its paralog EMC9) is also required for neural crest development and craniofacial cartilage formation [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established that the EMC, including the EMC8/9 module, is selectively required for biogenesis of multi-pass transmembrane proteins rather than secreted or single-pass proteins, defining its client specificity in vivo.\",\n      \"evidence\": \"Genetic loss-of-function screen in Drosophila photoreceptors with ER localization and Co-IP of EMC subunits with calnexin\",\n      \"pmids\": [\"25715730\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Does not separate the specific contribution of EMC8 from other EMC subunits\",\n        \"No structural mechanism for client recognition\",\n        \"Rhodopsin/TRP clients defined in Drosophila, not human EMC8\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the molecular mechanism by which the EMC acts as a holdase, showing it binds CaV1.2 through transmembrane and cytoplasmic docks and stages assembly via a mutually exclusive hand-off to CaVα2δ.\",\n      \"evidence\": \"Cryo-EM structures of human CaV1.2–CaVβ3–EMC and assembled CaV1.2–CaVβ3–CaVα2δ-1 channel plus functional disruption assays\",\n      \"pmids\": [\"37196677\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific catalytic or structural role of the EMC8 subunit within the complex not isolated\",\n        \"Molecular identity of the divalent ion-dependent step not defined\",\n        \"Whether the same hand-off logic applies to other EMC clients untested\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked EMC8 function to a developmental program by showing it (or paralog EMC9) is required for neural crest and craniofacial cartilage formation, connecting transmembrane protein topogenesis to organismal patterning.\",\n      \"evidence\": \"Morpholino-based depletion in Xenopus tropicalis with craniofacial and neural crest phenotypic assays\",\n      \"pmids\": [\"37318954\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Cannot resolve EMC8-specific requirement versus EMC9 substitution\",\n        \"No identification of the client proteins responsible for the developmental phenotype\",\n        \"Morpholino depletion lacks genetic confirmation\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The specific structural and functional contribution of the EMC8 subunit itself—as distinct from the whole EMC and from its paralog EMC9—remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No EMC8-specific client repertoire established\",\n        \"Functional non-redundancy between EMC8 and EMC9 not delineated\",\n        \"No structural assignment of EMC8 contacts to client docking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\"ER membrane protein complex (EMC)\"],\n    \"partners\": [\"CACNA1C\", \"EMC1\", \"EMC3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}