{"gene":"COX6B1","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2008,"finding":"A disease-associated mutation in COX6B1, a nuclear-encoded structural subunit of cytochrome c oxidase (Complex IV), causes severe COX deficiency, establishing COX6B1 as an essential structural component of the enzyme whose loss is compatible with extra-uterine survival.","method":"Patient mutation identification, biochemical COX activity assay, genetic analysis","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient mutation with biochemical enzymatic activity confirmation, single study but direct functional consequence demonstrated","pmids":["18499082"],"is_preprint":false},{"year":2014,"finding":"A missense p.R20C mutation in COX6B1 causes undetectable COX enzymatic activity in muscle and fibroblasts; complementation with wild-type COX6B1 cDNA via lentiviral construct restores COX activity, confirming the structural and functional necessity of COX6B1 for Complex IV activity.","method":"Enzymatic activity assay, lentiviral complementation, Western blot (protein detection in mitochondria)","journal":"European journal of human genetics : EJHG","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — enzymatic activity assay plus rescue complementation experiment, two orthogonal methods in a single study confirming functional role","pmids":["24781756"],"is_preprint":false},{"year":2015,"finding":"Yeast Cox12 (ortholog of human COX6B1) physically interacts with Cox2 and Coa6, and simultaneous deletion of Coa6 and Cox12 completely abrogates Cox2 biogenesis; overexpression of Cox12 partially rescues the coa6Δ phenotype, revealing a previously unidentified role for COX6B1/Cox12 in Cox2 (CcO subunit 2) biogenesis and copper delivery to Complex IV.","method":"Genetic epistasis (double-mutant yeast), co-immunoprecipitation (physical interaction between Coa6, Cox2, Cox12), overexpression rescue","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — genetic epistasis combined with biochemical Co-IP demonstrating physical interactions, multiple orthogonal methods","pmids":["26669719"],"is_preprint":false},{"year":2015,"finding":"Overexpression of Cox6b1 in NIH3T3 cells increases its incorporation into mitochondrial supercomplexes (III2IV1, III2IV2), increases COX activity, oxygen consumption, and intracellular ATP, demonstrating that Cox6b1 promotes formation of respiratory chain supercomplexes and enhances mitochondrial respiration.","method":"Blue native PAGE with immunoblotting, oxygen consumption rate assay, COX activity assay, ATP measurement in Cox6b1-overexpressing cells","journal":"Age (Dordrecht, Netherlands)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts (BN-PAGE, oxygen consumption, COX activity, ATP) in overexpression model, single lab","pmids":["25929654"],"is_preprint":false},{"year":2018,"finding":"COX6B1 overexpression in neonatal rat cardiomyocytes subjected to hypoxia/reoxygenation reduces mPTP opening, maintains mitochondrial membrane potential, reduces ROS production, retains cytochrome c within mitochondria, and suppresses caspase-3/9 cleavage, demonstrating a role for COX6B1 in maintaining mitochondrial integrity under ischemic stress.","method":"COX6B1 overexpression in primary cardiomyocytes, JC-1 assay (membrane potential), mPTP assay, Annexin-V/PI apoptosis assay, Western blot for cytochrome c and caspase cleavage","journal":"Biotechnology letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts in primary cells, single lab, overexpression model without KO confirmation","pmids":["30311029"],"is_preprint":false},{"year":2019,"finding":"COX6B1 overexpression in rat hippocampal neurons subjected to oxygen-glucose deprivation/reoxygenation increases cell viability, reduces cytosolic Ca2+ accumulation, retains cytochrome c in mitochondria, increases BCL-2 expression, and decreases BAX and cytosolic caspase activation, identifying a protective role for COX6B1 in neuronal ischemia/reperfusion injury.","method":"COX6B1 overexpression in primary hippocampal neurons, flow cytometry (apoptosis, Ca2+), Western blot (BCL-2, BAX, cytochrome c, caspases), cell viability assay","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts in primary neuronal cells, single lab, overexpression only without KO rescue","pmids":["31059068"],"is_preprint":false},{"year":2022,"finding":"miR-30b-3p directly targets and binds the 3′UTR of COX6B1 (validated by dual-luciferase assay), reducing COX6B1 protein levels in lung adenocarcinoma A549 cells; COX6B1 upregulation reverses the anti-proliferative and anti-invasive effects of miR-30b-3p overexpression, establishing COX6B1 as a downstream effector of miR-30b-3p in lung adenocarcinoma cell proliferation and invasion.","method":"Dual-luciferase reporter assay, Western blot, EdU proliferation assay, Transwell invasion assay, rescue experiment","journal":"Zhongguo fei ai za zhi = Chinese journal of lung cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dual-luciferase assay validates direct miRNA-target binding, rescue experiment confirms pathway placement, single lab","pmids":["36002193"],"is_preprint":false},{"year":2025,"finding":"COX6B1 knockout in human cells causes total loss of Complex IV (cIV) assembly, not merely destabilization; using COX6B1 KO cells expressing alternative oxidase and pathogenic COX6B1 variants, COX6B1 was shown to be required for redox-sensitive early cIV assembly steps in addition to late-stage stabilization. Partially assembled cIV modules were shown to incorporate directly into supercomplex structures, supporting a cooperative assembly model.","method":"CRISPR KO cell line, alternative oxidase expression, pathogenic variant complementation, BN-PAGE/SDS-PAGE assembly analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — KO cell line with multiple complementation experiments (alternative oxidase, pathogenic variants), multiple orthogonal methods revealing mechanism at early and late assembly stages","pmids":["41419202"],"is_preprint":false}],"current_model":"COX6B1 is a nuclear-encoded structural subunit of mitochondrial cytochrome c oxidase (Complex IV) located in the intermembrane space-facing region, required for both redox-sensitive early assembly steps and late-stage stabilization of cIV; it physically interacts with COX2 and assembly factor COA6 to facilitate copper delivery to COX2, promotes incorporation of cIV into respiratory chain supercomplexes to enhance mitochondrial respiration, and its loss—whether through pathogenic missense mutations or knockout—results in total cIV deficiency."},"narrative":{"mechanistic_narrative":"COX6B1 is a nuclear-encoded structural subunit of mitochondrial cytochrome c oxidase (Complex IV) that is essential for the enzyme's assembly and catalytic activity [PMID:24781756, PMID:41419202]. Beyond serving as a static structural component, COX6B1 participates in COX2 biogenesis and copper delivery to Complex IV through physical interaction with COX2 and the assembly factor COA6, as established in the yeast ortholog Cox12, where combined loss of Cox12 and Coa6 abolishes Cox2 biogenesis [PMID:26669719]. COX6B1 is required for redox-sensitive early assembly steps as well as late-stage stabilization of Complex IV, and partially assembled cIV modules incorporate directly into respiratory chain supercomplexes, consistent with a cooperative assembly model [PMID:41419202]; its overexpression increases incorporation of Complex IV into III2IV1/III2IV2 supercomplexes and elevates COX activity, oxygen consumption, and ATP [PMID:25929654]. Loss of COX6B1 — through pathogenic missense mutations such as p.R20C or genetic knockout — causes total Complex IV deficiency, and re-expression of wild-type COX6B1 restores COX activity, directly linking the gene to human COX-deficiency disease [PMID:18499082, PMID:24781756, PMID:41419202]. In stress models, COX6B1 overexpression preserves mitochondrial integrity, retaining cytochrome c, maintaining membrane potential, and suppressing apoptotic signaling under ischemic conditions [PMID:30311029, PMID:31059068].","teleology":[{"year":2008,"claim":"Established that COX6B1 is an essential structural subunit of Complex IV by showing a disease-associated mutation produces severe COX deficiency compatible with extra-uterine survival.","evidence":"Patient mutation identification with biochemical COX activity assay","pmids":["18499082"],"confidence":"Medium","gaps":["Single patient/study without complementation rescue","Mechanism by which loss causes deficiency not defined","Whether defect is assembly versus stability not addressed"]},{"year":2014,"claim":"Demonstrated functional necessity of COX6B1 for Complex IV activity by showing the p.R20C mutation abolishes COX activity and wild-type cDNA complementation restores it.","evidence":"Enzymatic activity assay plus lentiviral complementation in patient fibroblasts/muscle","pmids":["24781756"],"confidence":"High","gaps":["Does not resolve which assembly step requires COX6B1","No direct interaction partners identified","Structural basis of the R20C defect unknown"]},{"year":2015,"claim":"Identified a previously unrecognized role for COX6B1/Cox12 in COX2 biogenesis and copper delivery, moving it beyond a purely structural subunit.","evidence":"Yeast genetic epistasis (cox12Δ/coa6Δ double mutant), Co-IP of Cox12 with Cox2 and Coa6, overexpression rescue","pmids":["26669719"],"confidence":"High","gaps":["Direct copper-delivery role inferred from genetic interaction, not biochemically reconstituted","Human COX6B1 interactions inferred from yeast ortholog","Stoichiometry and timing of the interaction undefined"]},{"year":2015,"claim":"Showed COX6B1 promotes supercomplex formation and enhances respiration, linking subunit levels to assembly into higher-order respiratory structures.","evidence":"Cox6b1 overexpression in NIH3T3 cells with BN-PAGE, oxygen consumption, COX activity, and ATP measurements","pmids":["25929654"],"confidence":"Medium","gaps":["Overexpression model without loss-of-function confirmation","Single lab","Mechanism of supercomplex incorporation not defined"]},{"year":2018,"claim":"Connected COX6B1 to maintenance of mitochondrial integrity under ischemic stress, indicating a cytoprotective function beyond steady-state respiration.","evidence":"COX6B1 overexpression in neonatal rat cardiomyocytes under hypoxia/reoxygenation with mPTP, membrane potential, ROS, cytochrome c, and caspase assays","pmids":["30311029"],"confidence":"Medium","gaps":["Overexpression only, no knockout rescue","Whether protection is direct or secondary to improved respiration unclear","Single lab"]},{"year":2019,"claim":"Extended the cytoprotective role of COX6B1 to neurons, showing it limits apoptosis and calcium dysregulation during ischemia/reperfusion.","evidence":"COX6B1 overexpression in primary rat hippocampal neurons under oxygen-glucose deprivation with apoptosis, Ca2+, and BCL-2/BAX assays","pmids":["31059068"],"confidence":"Medium","gaps":["Overexpression model without endogenous loss-of-function","Causal link between respiration and anti-apoptotic effect not dissected","Single lab"]},{"year":2022,"claim":"Placed COX6B1 as a downstream effector of miR-30b-3p in lung adenocarcinoma, tying its expression to cancer cell proliferation and invasion.","evidence":"Dual-luciferase reporter, Western blot, EdU/Transwell assays, and rescue experiment in A549 cells","pmids":["36002193"],"confidence":"Medium","gaps":["Mechanism connecting COX6B1 to proliferation/invasion not defined","Single cell line and lab","Whether effect depends on respiratory function unknown"]},{"year":2025,"claim":"Resolved that COX6B1 acts at redox-sensitive early assembly steps as well as late stabilization, and that partial cIV modules feed directly into supercomplexes, refining the assembly model.","evidence":"CRISPR KO human cells with alternative oxidase expression and pathogenic variant complementation, BN-PAGE/SDS-PAGE assembly analysis","pmids":["41419202"],"confidence":"High","gaps":["Molecular nature of the redox-sensitive step not fully defined","Structural snapshot of the early assembly intermediate lacking","How specific pathogenic variants map to early versus late defects incompletely resolved"]},{"year":null,"claim":"How COX6B1 mechanistically couples copper delivery to COX2 with redox-sensitive early assembly, and whether its cytoprotective and cancer-associated roles are direct consequences of its assembly function, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted biochemistry of COX6B1-mediated copper handling in human cells","Cytoprotective and oncogenic phenotypes rest on overexpression models","No structural model of the early redox-sensitive assembly intermediate"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,7]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[1,3,4]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,3,7]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[2,7]}],"complexes":["cytochrome c oxidase (Complex IV)","respiratory chain supercomplex (III2IV1/III2IV2)"],"partners":["COX2","COA6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P14854","full_name":"Cytochrome c oxidase subunit 6B1","aliases":["Cytochrome c oxidase subunit VIb isoform 1","COX VIb-1"],"length_aa":86,"mass_kda":10.2,"function":"Component of the cytochrome c oxidase, the last enzyme in the mitochondrial electron transport chain which drives oxidative phosphorylation. The respiratory chain contains 3 multisubunit complexes succinate dehydrogenase (complex II, CII), ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate to transfer electrons derived from NADH and succinate to molecular oxygen, creating an electrochemical gradient over the inner membrane that drives transmembrane transport and the ATP synthase. Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Electrons originating from reduced cytochrome c in the intermembrane space (IMS) are transferred via the dinuclear copper A center (CU(A)) of subunit 2 and heme A of subunit 1 to the active site in subunit 1, a binuclear center (BNC) formed by heme A3 and copper B (CU(B)). The BNC reduces molecular oxygen to 2 water molecules using 4 electrons from cytochrome c in the IMS and 4 protons from the mitochondrial matrix","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/P14854/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COX6B1","classification":"Not Classified","n_dependent_lines":408,"n_total_lines":1208,"dependency_fraction":0.33774834437086093},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/COX6B1","total_profiled":1310},"omim":[{"mim_id":"619051","title":"MITOCHONDRIAL COMPLEX IV DEFICIENCY, NUCLEAR TYPE 7; MC4DN7","url":"https://www.omim.org/entry/619051"},{"mim_id":"618127","title":"CYTOCHROME C OXIDASE, SUBUNIT 6B2; COX6B2","url":"https://www.omim.org/entry/618127"},{"mim_id":"220110","title":"MITOCHONDRIAL COMPLEX IV DEFICIENCY, NUCLEAR TYPE 1; MC4DN1","url":"https://www.omim.org/entry/220110"},{"mim_id":"124089","title":"CYTOCHROME c OXIDASE, SUBUNIT 6B1; COX6B1","url":"https://www.omim.org/entry/124089"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"},{"location":"Principal piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"tongue","ntpm":2287.9}],"url":"https://www.proteinatlas.org/search/COX6B1"},"hgnc":{"alias_symbol":["COXG"],"prev_symbol":["COX6B"]},"alphafold":{"accession":"P14854","domains":[{"cath_id":"1.10.10.140","chopping":"26-86","consensus_level":"medium","plddt":96.7146,"start":26,"end":86}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P14854","model_url":"https://alphafold.ebi.ac.uk/files/AF-P14854-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P14854-F1-predicted_aligned_error_v6.png","plddt_mean":95.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=COX6B1","jax_strain_url":"https://www.jax.org/strain/search?query=COX6B1"},"sequence":{"accession":"P14854","fasta_url":"https://rest.uniprot.org/uniprotkb/P14854.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P14854/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P14854"}},"corpus_meta":[{"pmid":"18499082","id":"PMC_18499082","title":"Severe infantile encephalomyopathy caused by a mutation in COX6B1, a nucleus-encoded subunit of cytochrome c oxidase.","date":"2008","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18499082","citation_count":141,"is_preprint":false},{"pmid":"24781756","id":"PMC_24781756","title":"Mitochondrial complex IV deficiency, caused by mutated COX6B1, is associated with encephalomyopathy, hydrocephalus and cardiomyopathy.","date":"2014","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/24781756","citation_count":78,"is_preprint":false},{"pmid":"26669719","id":"PMC_26669719","title":"Mitochondrial disease genes COA6, COX6B and SCO2 have overlapping roles in COX2 biogenesis.","date":"2015","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26669719","citation_count":44,"is_preprint":false},{"pmid":"25929654","id":"PMC_25929654","title":"Upregulation of cytochrome c oxidase subunit 6b1 (Cox6b1) and formation of mitochondrial supercomplexes: implication of Cox6b1 in the effect of calorie restriction.","date":"2015","source":"Age (Dordrecht, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/25929654","citation_count":24,"is_preprint":false},{"pmid":"30311029","id":"PMC_30311029","title":"COX6B1 relieves hypoxia/reoxygenation injury of neonatal rat cardiomyocytes by regulating mitochondrial function.","date":"2018","source":"Biotechnology letters","url":"https://pubmed.ncbi.nlm.nih.gov/30311029","citation_count":22,"is_preprint":false},{"pmid":"31059068","id":"PMC_31059068","title":"Overexpression of COX6B1 protects against I/R‑induced neuronal injury in rat hippocampal neurons.","date":"2019","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/31059068","citation_count":16,"is_preprint":false},{"pmid":"38842388","id":"PMC_38842388","title":"A novel homozygous pathogenic missense variant in COX6B1: Further delineation of the phenotype.","date":"2024","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/38842388","citation_count":3,"is_preprint":false},{"pmid":"36002193","id":"PMC_36002193","title":"[miR-30b-3p Inhibits the Proliferation and Invasion of Lung Adenocarcinoma 
by Targeting COX6B1].","date":"2022","source":"Zhongguo fei ai za zhi = Chinese journal of lung cancer","url":"https://pubmed.ncbi.nlm.nih.gov/36002193","citation_count":3,"is_preprint":false},{"pmid":"40407326","id":"PMC_40407326","title":"GSNOR plays roles in growth, pathogenicity, and stress resistance by modulating mitochondrial protein COX6B S-nitrosylation in Colletotrichum gloeosporioides.","date":"2025","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/40407326","citation_count":2,"is_preprint":false},{"pmid":"40673312","id":"PMC_40673312","title":"[LncRNA SNHG15 promotes proliferation, migration and invasion of lung adenocarcinoma cells by regulating COX6B1 through sponge adsorption of miR-30b-3p].","date":"2025","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/40673312","citation_count":1,"is_preprint":false},{"pmid":"41419202","id":"PMC_41419202","title":"The cytochrome c oxidase subunit COX6B1 is required for redox-sensitive early assembly and late stabilization of complex IV.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41419202","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.01.679889","title":"Association of cytochrome c oxidase dysfunction with amyloidosis in Alzheimer’s disease and patient-derived cerebral organoids","date":"2025-10-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.01.679889","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.25.645161","title":"COX6B1 secures a redox-sensitive step in early cytochrome  <i>c</i>  oxidase assembly","date":"2025-03-26","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.25.645161","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9284,"output_tokens":2124,"usd":0.029856,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9222,"output_tokens":2972,"usd":0.060205,"stage2_stop_reason":"end_turn"},"total_usd":0.090061,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"A disease-associated mutation in COX6B1, a nuclear-encoded structural subunit of cytochrome c oxidase (Complex IV), causes severe COX deficiency, establishing COX6B1 as an essential structural component of the enzyme whose loss is compatible with extra-uterine survival.\",\n      \"method\": \"Patient mutation identification, biochemical COX activity assay, genetic analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient mutation with biochemical enzymatic activity confirmation, single study but direct functional consequence demonstrated\",\n      \"pmids\": [\"18499082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A missense p.R20C mutation in COX6B1 causes undetectable COX enzymatic activity in muscle and fibroblasts; complementation with wild-type COX6B1 cDNA via lentiviral construct restores COX activity, confirming the structural and functional necessity of COX6B1 for Complex IV activity.\",\n      \"method\": \"Enzymatic activity assay, lentiviral complementation, Western blot (protein detection in mitochondria)\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — enzymatic activity assay plus rescue complementation experiment, two orthogonal methods in a single study confirming functional role\",\n      \"pmids\": [\"24781756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Yeast Cox12 (ortholog of human COX6B1) physically interacts with Cox2 and Coa6, and simultaneous deletion of Coa6 and Cox12 completely abrogates Cox2 biogenesis; overexpression of Cox12 partially rescues the coa6Δ phenotype, revealing a previously unidentified role for COX6B1/Cox12 in Cox2 (CcO subunit 2) biogenesis and copper delivery to Complex IV.\",\n      \"method\": \"Genetic epistasis (double-mutant yeast), co-immunoprecipitation (physical interaction between Coa6, Cox2, Cox12), overexpression rescue\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — genetic epistasis combined with biochemical Co-IP demonstrating physical interactions, multiple orthogonal methods\",\n      \"pmids\": [\"26669719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Overexpression of Cox6b1 in NIH3T3 cells increases its incorporation into mitochondrial supercomplexes (III2IV1, III2IV2), increases COX activity, oxygen consumption, and intracellular ATP, demonstrating that Cox6b1 promotes formation of respiratory chain supercomplexes and enhances mitochondrial respiration.\",\n      \"method\": \"Blue native PAGE with immunoblotting, oxygen consumption rate assay, COX activity assay, ATP measurement in Cox6b1-overexpressing cells\",\n      \"journal\": \"Age (Dordrecht, Netherlands)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts (BN-PAGE, oxygen consumption, COX activity, ATP) in overexpression model, single lab\",\n      \"pmids\": [\"25929654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"COX6B1 overexpression in neonatal rat cardiomyocytes subjected to hypoxia/reoxygenation reduces mPTP opening, maintains mitochondrial membrane potential, reduces ROS production, retains cytochrome c within mitochondria, and suppresses caspase-3/9 cleavage, demonstrating a role for COX6B1 in maintaining mitochondrial integrity under ischemic stress.\",\n      \"method\": \"COX6B1 overexpression in primary cardiomyocytes, JC-1 assay (membrane potential), mPTP assay, Annexin-V/PI apoptosis assay, Western blot for cytochrome c and caspase cleavage\",\n      \"journal\": \"Biotechnology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts in primary cells, single lab, overexpression model without KO confirmation\",\n      \"pmids\": [\"30311029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"COX6B1 overexpression in rat hippocampal neurons subjected to oxygen-glucose deprivation/reoxygenation increases cell viability, reduces cytosolic Ca2+ accumulation, retains cytochrome c in mitochondria, increases BCL-2 expression, and decreases BAX and cytosolic caspase activation, identifying a protective role for COX6B1 in neuronal ischemia/reperfusion injury.\",\n      \"method\": \"COX6B1 overexpression in primary hippocampal neurons, flow cytometry (apoptosis, Ca2+), Western blot (BCL-2, BAX, cytochrome c, caspases), cell viability assay\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts in primary neuronal cells, single lab, overexpression only without KO rescue\",\n      \"pmids\": [\"31059068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-30b-3p directly targets and binds the 3′UTR of COX6B1 (validated by dual-luciferase assay), reducing COX6B1 protein levels in lung adenocarcinoma A549 cells; COX6B1 upregulation reverses the anti-proliferative and anti-invasive effects of miR-30b-3p overexpression, establishing COX6B1 as a downstream effector of miR-30b-3p in lung adenocarcinoma cell proliferation and invasion.\",\n      \"method\": \"Dual-luciferase reporter assay, Western blot, EdU proliferation assay, Transwell invasion assay, rescue experiment\",\n      \"journal\": \"Zhongguo fei ai za zhi = Chinese journal of lung cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual-luciferase assay validates direct miRNA-target binding, rescue experiment confirms pathway placement, single lab\",\n      \"pmids\": [\"36002193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"COX6B1 knockout in human cells causes total loss of Complex IV (cIV) assembly, not merely destabilization; using COX6B1 KO cells expressing alternative oxidase and pathogenic COX6B1 variants, COX6B1 was shown to be required for redox-sensitive early cIV assembly steps in addition to late-stage stabilization. Partially assembled cIV modules were shown to incorporate directly into supercomplex structures, supporting a cooperative assembly model.\",\n      \"method\": \"CRISPR KO cell line, alternative oxidase expression, pathogenic variant complementation, BN-PAGE/SDS-PAGE assembly analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — KO cell line with multiple complementation experiments (alternative oxidase, pathogenic variants), multiple orthogonal methods revealing mechanism at early and late assembly stages\",\n      \"pmids\": [\"41419202\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COX6B1 is a nuclear-encoded structural subunit of mitochondrial cytochrome c oxidase (Complex IV) located in the intermembrane space-facing region, required for both redox-sensitive early assembly steps and late-stage stabilization of cIV; it physically interacts with COX2 and assembly factor COA6 to facilitate copper delivery to COX2, promotes incorporation of cIV into respiratory chain supercomplexes to enhance mitochondrial respiration, and its loss—whether through pathogenic missense mutations or knockout—results in total cIV deficiency.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COX6B1 is a nuclear-encoded structural subunit of mitochondrial cytochrome c oxidase (Complex IV) that is essential for the enzyme's assembly and catalytic activity [#1, #7]. Beyond serving as a static structural component, COX6B1 participates in COX2 biogenesis and copper delivery to Complex IV through physical interaction with COX2 and the assembly factor COA6, as established in the yeast ortholog Cox12, where combined loss of Cox12 and Coa6 abolishes Cox2 biogenesis [#2]. COX6B1 is required for redox-sensitive early assembly steps as well as late-stage stabilization of Complex IV, and partially assembled cIV modules incorporate directly into respiratory chain supercomplexes, consistent with a cooperative assembly model [#7]; its overexpression increases incorporation of Complex IV into III2IV1/III2IV2 supercomplexes and elevates COX activity, oxygen consumption, and ATP [#3]. Loss of COX6B1 — through pathogenic missense mutations such as p.R20C or genetic knockout — causes total Complex IV deficiency, and re-expression of wild-type COX6B1 restores COX activity, directly linking the gene to human COX-deficiency disease [#0, #1, #7]. In stress models, COX6B1 overexpression preserves mitochondrial integrity, retaining cytochrome c, maintaining membrane potential, and suppressing apoptotic signaling under ischemic conditions [#4, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that COX6B1 is an essential structural subunit of Complex IV by showing a disease-associated mutation produces severe COX deficiency compatible with extra-uterine survival.\",\n      \"evidence\": \"Patient mutation identification with biochemical COX activity assay\",\n      \"pmids\": [\"18499082\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single patient/study without complementation rescue\",\n        \"Mechanism by which loss causes deficiency not defined\",\n        \"Whether defect is assembly versus stability not addressed\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated functional necessity of COX6B1 for Complex IV activity by showing the p.R20C mutation abolishes COX activity and wild-type cDNA complementation restores it.\",\n      \"evidence\": \"Enzymatic activity assay plus lentiviral complementation in patient fibroblasts/muscle\",\n      \"pmids\": [\"24781756\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Does not resolve which assembly step requires COX6B1\",\n        \"No direct interaction partners identified\",\n        \"Structural basis of the R20C defect unknown\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified a previously unrecognized role for COX6B1/Cox12 in COX2 biogenesis and copper delivery, moving it beyond a purely structural subunit.\",\n      \"evidence\": \"Yeast genetic epistasis (cox12Δ/coa6Δ double mutant), Co-IP of Cox12 with Cox2 and Coa6, overexpression rescue\",\n      \"pmids\": [\"26669719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct copper-delivery role inferred from genetic interaction, not biochemically reconstituted\",\n        \"Human COX6B1 interactions inferred from yeast ortholog\",\n        \"Stoichiometry and timing of the interaction undefined\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed COX6B1 promotes supercomplex formation and enhances respiration, linking subunit levels to assembly into higher-order respiratory structures.\",\n      \"evidence\": \"Cox6b1 overexpression in NIH3T3 cells with BN-PAGE, oxygen consumption, COX activity, and ATP measurements\",\n      \"pmids\": [\"25929654\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression model without loss-of-function confirmation\",\n        \"Single lab\",\n        \"Mechanism of supercomplex incorporation not defined\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected COX6B1 to maintenance of mitochondrial integrity under ischemic stress, indicating a cytoprotective function beyond steady-state respiration.\",\n      \"evidence\": \"COX6B1 overexpression in neonatal rat cardiomyocytes under hypoxia/reoxygenation with mPTP, membrane potential, ROS, cytochrome c, and caspase assays\",\n      \"pmids\": [\"30311029\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression only, no knockout rescue\",\n        \"Whether protection is direct or secondary to improved respiration unclear\",\n        \"Single lab\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended the cytoprotective role of COX6B1 to neurons, showing it limits apoptosis and calcium dysregulation during ischemia/reperfusion.\",\n      \"evidence\": \"COX6B1 overexpression in primary rat hippocampal neurons under oxygen-glucose deprivation with apoptosis, Ca2+, and BCL-2/BAX assays\",\n      \"pmids\": [\"31059068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression model without endogenous loss-of-function\",\n        \"Causal link between respiration and anti-apoptotic effect not dissected\",\n        \"Single lab\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed COX6B1 as a downstream effector of miR-30b-3p in lung adenocarcinoma, tying its expression to cancer cell proliferation and invasion.\",\n      \"evidence\": \"Dual-luciferase reporter, Western blot, EdU/Transwell assays, and rescue experiment in A549 cells\",\n      \"pmids\": [\"36002193\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism connecting COX6B1 to proliferation/invasion not defined\",\n        \"Single cell line and lab\",\n        \"Whether effect depends on respiratory function unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved that COX6B1 acts at redox-sensitive early assembly steps as well as late stabilization, and that partial cIV modules feed directly into supercomplexes, refining the assembly model.\",\n      \"evidence\": \"CRISPR KO human cells with alternative oxidase expression and pathogenic variant complementation, BN-PAGE/SDS-PAGE assembly analysis\",\n      \"pmids\": [\"41419202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular nature of the redox-sensitive step not fully defined\",\n        \"Structural snapshot of the early assembly intermediate lacking\",\n        \"How specific pathogenic variants map to early versus late defects incompletely resolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How COX6B1 mechanistically couples copper delivery to COX2 with redox-sensitive early assembly, and whether its cytoprotective and cancer-associated roles are direct consequences of its assembly function, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No reconstituted biochemistry of COX6B1-mediated copper handling in human cells\",\n        \"Cytoprotective and oncogenic phenotypes rest on overexpression models\",\n        \"No structural model of the early redox-sensitive assembly intermediate\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [1, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 3, 7]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"complexes\": [\n      \"cytochrome c oxidase (Complex IV)\",\n      \"respiratory chain supercomplex (III2IV1/III2IV2)\"\n    ],\n    \"partners\": [\n      \"COX2\",\n      \"COA6\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}