{"gene":"MT-CO2","run_date":"2026-06-14T21:12:36+00:00","timeline":{"discoveries":[{"year":1995,"finding":"The nuclear-encoded MSS2 gene is required for expression of the mitochondrial cytochrome c oxidase subunit 2 (Cox2) protein in Saccharomyces cerevisiae; mss2-1 mutant cells lack Cox2 protein despite normal COX2 transcript synthesis and processing, placing MSS2 post-transcriptionally upstream of Cox2 production.","method":"Genetic epistasis / mutant analysis: COX2 transcripts present but Cox2 protein absent in mss2-1 mutant; MSS2 gene cloned and sequenced","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean genetic epistasis in yeast ortholog, single lab, single mutant analysis","pmids":["7857963"],"is_preprint":false},{"year":1991,"finding":"A point mutation in the Neurospora crassa COXII gene (Thr→Ile at residue 27 of the precursor / residue 15 of mature subunit 2) causes deficiency of cytochrome aa3 and reduced Cox2 protein levels, demonstrating that this conserved Thr/Ser residue is functionally critical for Cox2 stability or assembly.","method":"DNA sequencing of COXI and COXII in the [exn-5] mutant; mitochondrial translation product analysis; heterokaryon segregation analysis","journal":"Current genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — sequencing plus translation product analysis in fungal ortholog, single lab, multiple methods but no in vitro reconstitution","pmids":["1657411"],"is_preprint":false},{"year":2011,"finding":"NEIL2 and PNKP co-localize with MT-CO2 in human mitochondria and associate (by chromatin immunoprecipitation) with the MT-CO2 mitochondrial gene locus, establishing MT-CO2 as a marker for mitochondrial localization and demonstrating that the mt-BER/SSBR machinery operates at the MT-CO2 locus.","method":"Confocal co-localization with MT-CO2 as mitochondrial marker; ChIP showing NEIL2/PNKP association with MT-CO2 gene; proximity ligation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (confocal, ChIP, PLA) in single study; MT-CO2 used as validated mitochondrial marker","pmids":["22130663"],"is_preprint":false},{"year":2019,"finding":"In SH-SY5Y dopaminergic cells, exogenous α-synuclein upregulates MT-CO2 expression, and siRNA-mediated knockdown of MT-CO2 reverses α-synuclein-induced ATP depletion, mitochondrial membrane potential loss, and ROS elevation, indicating that MT-CO2 upregulation mediates α-synuclein-induced mitochondrial dysfunction. MT-CO2 knockdown also reduced cytochrome c release and altered BCL2-family protein levels.","method":"Gene microarray and western blot to detect MT-CO2 upregulation; siRNA knockdown of MT-CO2 with readouts of ATP, mitochondrial membrane potential, ROS, cytochrome c release, and BCL2-family proteins","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — siRNA loss-of-function with multiple phenotypic readouts, single lab, no in vitro reconstitution","pmids":["30776354"],"is_preprint":false},{"year":2022,"finding":"FBP1 overexpression in AML cells reduces MT-CO2 protein expression concomitant with impaired mitochondrial homeostasis and increased apoptosis, placing MT-CO2 downstream of FBP1-mediated metabolic reprogramming in leukemic cells.","method":"Lentiviral FBP1 overexpression in MV4-11 cells; western blot for MT-CO2 protein; measurements of mitochondrial oxygen consumption and PINK1 levels","journal":"International journal of molecular sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, western blot with functional correlate but no direct MT-CO2 manipulation to establish causality","pmids":["36232688"],"is_preprint":false},{"year":2022,"finding":"ρ0 pancreatic cancer cells (lacking mtDNA and therefore lacking MT-CO2 protein) show no mitochondrial oxygen consumption, confirming MT-CO2 as an obligate component of mitochondrial oxidative phosphorylation; these ρ0 cells are more resistant to pharmacological ascorbate-induced cell death than parental cells.","method":"Generation of ρ0 cells by mitochondrial overexpression of Y147A mutant uracil-N-glycosylase or HSV protein; MT-CO2 protein absence confirmed by western blot; oxygen consumption rate measured","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean loss-of-function model with direct MT-CO2 protein verification and oxygen consumption readout, single lab","pmids":["36581766"],"is_preprint":false}],"current_model":"MT-CO2 (cytochrome c oxidase subunit II) is an obligate mitochondrially encoded catalytic subunit of Complex IV (cytochrome c oxidase) that is essential for electron transfer from cytochrome c and mitochondrial oxygen consumption; its expression depends on nuclear-encoded factors (e.g., MSS2 in yeast), a conserved Thr/Ser residue at position 15 of the mature protein is critical for its stability/assembly, its upregulation mediates α-synuclein-induced mitochondrial dysfunction in dopaminergic cells, and it serves as a validated marker of the mitochondrial inner membrane whose locus is actively maintained by the mt-BER/SSBR machinery (NEIL2, PNKP)."},"narrative":{"mechanistic_narrative":"MT-CO2 (cytochrome c oxidase subunit II) is a mitochondrially encoded catalytic subunit of Complex IV that is obligatory for mitochondrial oxidative phosphorylation: ρ0 cells lacking mtDNA, and therefore MT-CO2 protein, show no mitochondrial oxygen consumption [PMID:36581766]. Production of the mature protein depends on dedicated nuclear-encoded factors acting post-transcriptionally, as shown in yeast where loss of MSS2 abolishes Cox2 protein despite normal COX2 transcript synthesis and processing [PMID:7857963], and a conserved Thr/Ser residue near the mature N-terminus is critical for subunit stability or assembly, since its mutation in the fungal ortholog reduces Cox2 levels and causes cytochrome aa3 deficiency [PMID:1657411]. In human cells MT-CO2 serves as a validated mitochondrial inner-membrane marker, and its gene locus is engaged by the mitochondrial base-excision/single-strand-break repair machinery NEIL2 and PNKP [PMID:22130663]. MT-CO2 expression is dynamically regulated in disease states: α-synuclein upregulates MT-CO2 in dopaminergic cells, and MT-CO2 knockdown reverses α-synuclein-induced ATP depletion, membrane-potential loss, ROS elevation, and cytochrome c release, linking it to mitochondrial dysfunction and apoptotic signaling [PMID:30776354].","teleology":[{"year":1991,"claim":"Identified a specific conserved residue whose integrity governs Cox2 stability, defining a sequence determinant of subunit assembly rather than catalysis.","evidence":"DNA sequencing and mitochondrial translation product analysis of a Neurospora crassa COXII Thr→Ile mutant","pmids":["1657411"],"confidence":"Medium","gaps":["Mechanism by which the residue stabilizes the subunit not resolved","Demonstrated in fungal ortholog, not human MT-CO2","No structural data on the affected region"]},{"year":1995,"claim":"Established that Cox2 protein production requires a dedicated nuclear-encoded factor acting after transcription, separating transcript availability from protein accumulation.","evidence":"Genetic epistasis in S. cerevisiae mss2-1 mutant: COX2 transcripts present but Cox2 protein absent","pmids":["7857963"],"confidence":"Medium","gaps":["Molecular step at which MSS2 acts (translation vs assembly) not defined","Human ortholog of MSS2 not addressed","No biochemical reconstitution"]},{"year":2011,"claim":"Placed the MT-CO2 mitochondrial locus under active surveillance by the mt-BER/SSBR machinery and validated MT-CO2 as a mitochondrial localization marker.","evidence":"Confocal co-localization, ChIP, and proximity ligation assay showing NEIL2/PNKP association with the MT-CO2 gene in human mitochondria","pmids":["22130663"],"confidence":"Medium","gaps":["Functional consequence of repair at this locus not measured","Whether MT-CO2 DNA is preferentially damaged unknown","No link to MT-CO2 protein output established"]},{"year":2019,"claim":"Connected MT-CO2 expression level to disease-relevant mitochondrial dysfunction, showing it is not merely a constitutive subunit but a regulated effector.","evidence":"Microarray/western showing α-synuclein upregulation of MT-CO2 and siRNA knockdown rescuing ATP, membrane potential, ROS, and cytochrome c phenotypes in SH-SY5Y cells","pmids":["30776354"],"confidence":"Medium","gaps":["Mechanism by which MT-CO2 upregulation causes dysfunction unclear","Single cell line, single lab","Relationship to Complex IV assembly not examined"]},{"year":2022,"claim":"Confirmed MT-CO2 as an obligate component of oxidative phosphorylation using a clean genetic-null model.","evidence":"ρ0 pancreatic cancer cells lacking mtDNA/MT-CO2 protein show abolished oxygen consumption; western blot confirmation","pmids":["36581766"],"confidence":"Medium","gaps":["ρ0 loss is not MT-CO2-specific (entire mtDNA absent)","Does not isolate MT-CO2 contribution from other subunits","Ascorbate resistance phenotype mechanism not defined"]},{"year":2022,"claim":"Positioned MT-CO2 protein abundance downstream of metabolic reprogramming, linking respiratory subunit levels to a regulatory transcription/metabolic axis.","evidence":"Lentiviral FBP1 overexpression in MV4-11 AML cells reduces MT-CO2 protein with impaired mitochondrial homeostasis and increased apoptosis","pmids":["36232688"],"confidence":"Low","gaps":["No direct MT-CO2 manipulation to establish causality","Correlative western blot only","FBP1→MT-CO2 mechanism unknown"]},{"year":null,"claim":"How MT-CO2 expression is regulated in human cells and how its level mechanistically controls Complex IV assembly and apoptotic signaling remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No human counterpart of yeast MSS2 characterized in the corpus","No structural or in vitro reconstitution data for human MT-CO2","Direct link between MT-CO2 level and Complex IV catalytic function not established"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[2,5]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5]}],"complexes":["cytochrome c oxidase (Complex IV)"],"partners":["NEIL2","PNKP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P00403","full_name":"Cytochrome c oxidase subunit 2","aliases":["Cytochrome c oxidase polypeptide II"],"length_aa":227,"mass_kda":25.6,"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/P00403/entry"},"depmap":{"release":"DepMap","has_data":false,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MT-CO2"},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MT-CO2","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"heart muscle","ntpm":214510.8}],"url":"https://www.proteinatlas.org/search/MT-CO2"},"hgnc":{"alias_symbol":["COX2","CO2"],"prev_symbol":["MTCO2"]},"alphafold":{"accession":"P00403","domains":[{"cath_id":"1.10.287.90","chopping":"14-87","consensus_level":"high","plddt":96.3997,"start":14,"end":87},{"cath_id":"2.60.40.420","chopping":"94-220","consensus_level":"high","plddt":96.0573,"start":94,"end":220}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P00403","model_url":"https://alphafold.ebi.ac.uk/files/AF-P00403-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P00403-F1-predicted_aligned_error_v6.png","plddt_mean":94.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MT-CO2","jax_strain_url":"https://www.jax.org/strain/search?query=MT-CO2"},"sequence":{"accession":"P00403","fasta_url":"https://rest.uniprot.org/uniprotkb/P00403.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P00403/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P00403"}},"corpus_meta":[{"pmid":"23790948","id":"PMC_23790948","title":"Thermogenesis is involved in the body-fat lowering effects of resveratrol in rats.","date":"2013","source":"Food chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23790948","citation_count":96,"is_preprint":false},{"pmid":"23274094","id":"PMC_23274094","title":"Hepatic lipid metabolic pathways modified by resveratrol in rats fed an obesogenic diet.","date":"2012","source":"Nutrition (Burbank, Los Angeles County, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/23274094","citation_count":83,"is_preprint":false},{"pmid":"22130663","id":"PMC_22130663","title":"Role of human DNA glycosylase Nei-like 2 (NEIL2) and single strand break repair protein polynucleotide kinase 3'-phosphatase in maintenance of mitochondrial genome.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22130663","citation_count":76,"is_preprint":false},{"pmid":"12496142","id":"PMC_12496142","title":"Reduced amount of mitochondrial DNA in aged human muscle.","date":"2002","source":"Journal of applied physiology (Bethesda, Md. : 1985)","url":"https://pubmed.ncbi.nlm.nih.gov/12496142","citation_count":71,"is_preprint":false},{"pmid":"9602159","id":"PMC_9602159","title":"Differences in gene expression between sleep and waking as revealed by mRNA differential display.","date":"1998","source":"Brain research. 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absent in mss2-1 mutant; MSS2 gene cloned and sequenced\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean genetic epistasis in yeast ortholog, single lab, single mutant analysis\",\n      \"pmids\": [\"7857963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"A point mutation in the Neurospora crassa COXII gene (Thr→Ile at residue 27 of the precursor / residue 15 of mature subunit 2) causes deficiency of cytochrome aa3 and reduced Cox2 protein levels, demonstrating that this conserved Thr/Ser residue is functionally critical for Cox2 stability or assembly.\",\n      \"method\": \"DNA sequencing of COXI and COXII in the [exn-5] mutant; mitochondrial translation product analysis; heterokaryon segregation analysis\",\n      \"journal\": \"Current genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — sequencing plus translation product analysis in fungal ortholog, single lab, multiple methods but no in vitro reconstitution\",\n      \"pmids\": [\"1657411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NEIL2 and PNKP co-localize with MT-CO2 in human mitochondria and associate (by chromatin immunoprecipitation) with the MT-CO2 mitochondrial gene locus, establishing MT-CO2 as a marker for mitochondrial localization and demonstrating that the mt-BER/SSBR machinery operates at the MT-CO2 locus.\",\n      \"method\": \"Confocal co-localization with MT-CO2 as mitochondrial marker; ChIP showing NEIL2/PNKP association with MT-CO2 gene; proximity ligation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (confocal, ChIP, PLA) in single study; MT-CO2 used as validated mitochondrial marker\",\n      \"pmids\": [\"22130663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In SH-SY5Y dopaminergic cells, exogenous α-synuclein upregulates MT-CO2 expression, and siRNA-mediated knockdown of MT-CO2 reverses α-synuclein-induced ATP depletion, mitochondrial membrane potential loss, and ROS elevation, indicating that MT-CO2 upregulation mediates α-synuclein-induced mitochondrial dysfunction. MT-CO2 knockdown also reduced cytochrome c release and altered BCL2-family protein levels.\",\n      \"method\": \"Gene microarray and western blot to detect MT-CO2 upregulation; siRNA knockdown of MT-CO2 with readouts of ATP, mitochondrial membrane potential, ROS, cytochrome c release, and BCL2-family proteins\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — siRNA loss-of-function with multiple phenotypic readouts, single lab, no in vitro reconstitution\",\n      \"pmids\": [\"30776354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FBP1 overexpression in AML cells reduces MT-CO2 protein expression concomitant with impaired mitochondrial homeostasis and increased apoptosis, placing MT-CO2 downstream of FBP1-mediated metabolic reprogramming in leukemic cells.\",\n      \"method\": \"Lentiviral FBP1 overexpression in MV4-11 cells; western blot for MT-CO2 protein; measurements of mitochondrial oxygen consumption and PINK1 levels\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, western blot with functional correlate but no direct MT-CO2 manipulation to establish causality\",\n      \"pmids\": [\"36232688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ρ0 pancreatic cancer cells (lacking mtDNA and therefore lacking MT-CO2 protein) show no mitochondrial oxygen consumption, confirming MT-CO2 as an obligate component of mitochondrial oxidative phosphorylation; these ρ0 cells are more resistant to pharmacological ascorbate-induced cell death than parental cells.\",\n      \"method\": \"Generation of ρ0 cells by mitochondrial overexpression of Y147A mutant uracil-N-glycosylase or HSV protein; MT-CO2 protein absence confirmed by western blot; oxygen consumption rate measured\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean loss-of-function model with direct MT-CO2 protein verification and oxygen consumption readout, single lab\",\n      \"pmids\": [\"36581766\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MT-CO2 (cytochrome c oxidase subunit II) is an obligate mitochondrially encoded catalytic subunit of Complex IV (cytochrome c oxidase) that is essential for electron transfer from cytochrome c and mitochondrial oxygen consumption; its expression depends on nuclear-encoded factors (e.g., MSS2 in yeast), a conserved Thr/Ser residue at position 15 of the mature protein is critical for its stability/assembly, its upregulation mediates α-synuclein-induced mitochondrial dysfunction in dopaminergic cells, and it serves as a validated marker of the mitochondrial inner membrane whose locus is actively maintained by the mt-BER/SSBR machinery (NEIL2, PNKP).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MT-CO2 (cytochrome c oxidase subunit II) is a mitochondrially encoded catalytic subunit of Complex IV that is obligatory for mitochondrial oxidative phosphorylation: ρ0 cells lacking mtDNA, and therefore MT-CO2 protein, show no mitochondrial oxygen consumption [#5]. Production of the mature protein depends on dedicated nuclear-encoded factors acting post-transcriptionally, as shown in yeast where loss of MSS2 abolishes Cox2 protein despite normal COX2 transcript synthesis and processing [#0], and a conserved Thr/Ser residue near the mature N-terminus is critical for subunit stability or assembly, since its mutation in the fungal ortholog reduces Cox2 levels and causes cytochrome aa3 deficiency [#1]. In human cells MT-CO2 serves as a validated mitochondrial inner-membrane marker, and its gene locus is engaged by the mitochondrial base-excision/single-strand-break repair machinery NEIL2 and PNKP [#2]. MT-CO2 expression is dynamically regulated in disease states: α-synuclein upregulates MT-CO2 in dopaminergic cells, and MT-CO2 knockdown reverses α-synuclein-induced ATP depletion, membrane-potential loss, ROS elevation, and cytochrome c release, linking it to mitochondrial dysfunction and apoptotic signaling [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Identified a specific conserved residue whose integrity governs Cox2 stability, defining a sequence determinant of subunit assembly rather than catalysis.\",\n      \"evidence\": \"DNA sequencing and mitochondrial translation product analysis of a Neurospora crassa COXII Thr→Ile mutant\",\n      \"pmids\": [\"1657411\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which the residue stabilizes the subunit not resolved\", \"Demonstrated in fungal ortholog, not human MT-CO2\", \"No structural data on the affected region\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Established that Cox2 protein production requires a dedicated nuclear-encoded factor acting after transcription, separating transcript availability from protein accumulation.\",\n      \"evidence\": \"Genetic epistasis in S. cerevisiae mss2-1 mutant: COX2 transcripts present but Cox2 protein absent\",\n      \"pmids\": [\"7857963\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular step at which MSS2 acts (translation vs assembly) not defined\", \"Human ortholog of MSS2 not addressed\", \"No biochemical reconstitution\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed the MT-CO2 mitochondrial locus under active surveillance by the mt-BER/SSBR machinery and validated MT-CO2 as a mitochondrial localization marker.\",\n      \"evidence\": \"Confocal co-localization, ChIP, and proximity ligation assay showing NEIL2/PNKP association with the MT-CO2 gene in human mitochondria\",\n      \"pmids\": [\"22130663\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of repair at this locus not measured\", \"Whether MT-CO2 DNA is preferentially damaged unknown\", \"No link to MT-CO2 protein output established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected MT-CO2 expression level to disease-relevant mitochondrial dysfunction, showing it is not merely a constitutive subunit but a regulated effector.\",\n      \"evidence\": \"Microarray/western showing α-synuclein upregulation of MT-CO2 and siRNA knockdown rescuing ATP, membrane potential, ROS, and cytochrome c phenotypes in SH-SY5Y cells\",\n      \"pmids\": [\"30776354\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which MT-CO2 upregulation causes dysfunction unclear\", \"Single cell line, single lab\", \"Relationship to Complex IV assembly not examined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed MT-CO2 as an obligate component of oxidative phosphorylation using a clean genetic-null model.\",\n      \"evidence\": \"ρ0 pancreatic cancer cells lacking mtDNA/MT-CO2 protein show abolished oxygen consumption; western blot confirmation\",\n      \"pmids\": [\"36581766\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ρ0 loss is not MT-CO2-specific (entire mtDNA absent)\", \"Does not isolate MT-CO2 contribution from other subunits\", \"Ascorbate resistance phenotype mechanism not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Positioned MT-CO2 protein abundance downstream of metabolic reprogramming, linking respiratory subunit levels to a regulatory transcription/metabolic axis.\",\n      \"evidence\": \"Lentiviral FBP1 overexpression in MV4-11 AML cells reduces MT-CO2 protein with impaired mitochondrial homeostasis and increased apoptosis\",\n      \"pmids\": [\"36232688\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct MT-CO2 manipulation to establish causality\", \"Correlative western blot only\", \"FBP1→MT-CO2 mechanism unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MT-CO2 expression is regulated in human cells and how its level mechanistically controls Complex IV assembly and apoptotic signaling remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No human counterpart of yeast MSS2 characterized in the corpus\", \"No structural or in vitro reconstitution data for human MT-CO2\", \"Direct link between MT-CO2 level and Complex IV catalytic function not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"cytochrome c oxidase (Complex IV)\"],\n    \"partners\": [\"NEIL2\", \"PNKP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win"}}