Affinage

COXFA4

Cytochrome c oxidase subunit FA4 · UniProt O00483

Length
81 aa
Mass
9.4 kDa
Annotated
2026-06-09
32 papers in source corpus 16 papers cited in narrative 16 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

COXFA4 (formerly NDUFA4) encodes a nuclear-encoded subunit of mitochondrial Complex IV (cytochrome c oxidase), reassigned from Complex I after proteomic, genetic, and biochemical analysis established that its loss selectively impairs CIV function and biogenesis without perturbing Complex I (PMID:22902835). It physically associates with the COX enzyme complex, and its absence yields catalytically deficient COX lacking abnormal subassemblies, identifying it as a late-stage assembly subunit (PMID:23746447, PMID:42218136). Functionally, COXFA4 supports oxidative phosphorylation: its depletion lowers oxygen consumption, ATP, CIV activity, and levels of COX6C and COX5B (PMID:36307669). Biallelic loss-of-function variants cause isolated cytochrome c oxidase deficiency in humans, and in patient fibroblasts complete loss of COXFA4 protein is partly buffered by upregulation of the paralog COXFA4L2 (PMID:23746447, PMID:42218136). COXFA4 occupancy of CIV is itself regulated by paralog competition: C15ORF48 uses a C-terminal α-helical domain to displace COXFA4 from the complex and target it for degradation, thereby restraining colonocyte metabolism and NF-κB-driven inflammation (PMID:38917002). Loss of COXFA4 triggers mitochondrial stress with downstream consequences including mtDNA leakage and type I interferon activation (PMID:36206731), VDAC1 upregulation driving ER stress and neuronal apoptosis through a direct COXFA4–VDAC1 interaction (PMID:42181741), and deficiency of the ornithine decarboxylase/polyamine pathway underlying cardiac phenotypes (PMID:39967265). Its expression is post-transcriptionally tuned by multiple microRNAs and an m6A writer–reader axis, coupling COXFA4 abundance to metabolic state in cancer and tissue-injury contexts (PMID:35977935, PMID:37211637, PMID:32258168).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 2012 High

    Resolved which respiratory complex COXFA4 belongs to, overturning its assignment to Complex I and establishing it as a Complex IV component.

    Evidence Proteomics, genetic deletion, biochemistry and evolutionary analysis

    PMID:22902835

    Open questions at the time
    • Did not define whether it is a structural subunit or assembly factor
    • Stoichiometry within CIV not resolved
  2. 2013 High

    Established that COXFA4 loss causes human disease, linking its function to isolated CIV deficiency and confirming physical association with the COX complex.

    Evidence Homozygosity mapping, exome sequencing, BN-PAGE and Western blot on patient muscle

    PMID:23746447

    Open questions at the time
    • Mechanism of how COX assembles without COXFA4 not detailed
    • No compensatory pathway identified at this stage
  3. 2017 Low

    Raised the question of whether COXFA4 is a stable structural subunit or an assembly factor in terminally differentiated tissues.

    Evidence Reanalysis of CcO composition from adult tissue and published data

    PMID:28988874

    Open questions at the time
    • Single-lab reanalysis without reconstitution or mutagenesis
    • Contradicts stronger multi-method subunit evidence
    • Does not directly test assembly-factor model
  4. 2020 Medium

    Showed paralog substitution within CIV, with COXFA4 replacing Coxfa4l3/C15orf48 in a developmentally regulated, mutually exclusive manner during spermatogenesis.

    Evidence Sequence comparison, localization, and stage-resolved expression analysis

    PMID:32045714

    Open questions at the time
    • Functional consequence of paralog swap on CIV activity not quantified
    • Regulatory trigger for the switch unknown
  5. 2020 Medium

    Demonstrated post-transcriptional control of COXFA4 by an exosomal microRNA linking macrophage signaling to adipocyte CIV activity and glucose uptake.

    Evidence Dual-luciferase reporter, RNA pull-down, and overexpression rescue in adipocytes

    PMID:32258168

    Open questions at the time
    • In vivo relevance to metabolic disease not established
    • Single-lab target validation
  6. 2022 Medium

    Quantified COXFA4's contribution to oxidative phosphorylation, showing it drives OXPHOS and CIV subunit abundance bidirectionally.

    Evidence siRNA knockdown/overexpression, OCR, ATP and CIV activity assays, xenograft in pancreatic cancer

    PMID:36307669

    Open questions at the time
    • Mechanism by which COXFA4 affects COX6C/COX5B levels unclear
    • Cancer-specific generality not tested
  7. 2022 Medium

    Linked COXFA4 loss to innate immune activation, defining a mitochondrial-stress-to-interferon axis with antiviral consequences.

    Evidence hiPSC GWAS, isogenic loss-of-function lines, mtDNA leakage and interferon readouts

    PMID:36206731

    Open questions at the time
    • Route of mtDNA release not mechanistically dissected
    • Connection to disease pathology not established
  8. 2022 Medium

    Identified an m6A-based regulatory mechanism (METTL3/IGF2BP1) controlling COXFA4 expression and downstream glycolysis and mitochondrial fission in cancer.

    Evidence RIP, OCR/ECAR, flow cytometry and knockdown in gastric cancer cells

    PMID:35977935

    Open questions at the time
    • How COXFA4 promotes fission mechanistically unresolved
    • Single-lab finding
  9. 2022 Medium

    Reported a physical partner, REEP1, that preserves CIV integrity and links COXFA4 to motor neuron survival.

    Evidence Co-IP and in vivo REEP1 overexpression in SOD1G93A mice

    PMID:36520405

    Open questions at the time
    • Reciprocal Co-IP not specified
    • Direct vs indirect association unclear
  10. 2023 Medium

    Connected COXFA4 to a neuronal regulatory axis, showing its knockout impairs brain histology and learning through a miR-145a-5p/Homer1/Ccnd2 pathway.

    Evidence Knockout mice, microRNA profiling, luciferase target validation, behavioral testing

    PMID:36763283

    Open questions at the time
    • How a CIV subunit controls miRNA expression unexplained
    • Mitochondrial vs non-mitochondrial mechanism not separated
  11. 2023 Medium

    Showed COXFA4 repression by miR-147 drives renal tubular mitochondrial dysfunction and that restoring it protects against transplant injury.

    Evidence Luciferase assay, anti-miRNA, overexpression in mouse kidney transplant model

    PMID:37211637

    Open questions at the time
    • Therapeutic translatability not tested
    • Single-lab validation
  12. 2024 Medium

    Defined the molecular basis of paralog competition, showing C15ORF48 displaces COXFA4 from CIV via a C-terminal helix to suppress metabolism and NF-κB inflammation.

    Evidence Mouse knockout, CIV fractionation, domain analysis, NF-κB assays and colitis model

    PMID:38917002

    Open questions at the time
    • Structural detail of the displacement interface not resolved
    • Generality beyond colonocytes untested
  13. 2024 Medium

    Linked COXFA4/CIV dysfunction to polyamine metabolism, identifying ornithine decarboxylase pathway deficiency as a druggable downstream node for cardiac phenotypes.

    Evidence Xenopus loss-of-function model, transcriptomics, pharmacological rescue

    PMID:39967265

    Open questions at the time
    • Mechanistic link between CIV loss and polyamine pathway unclear
    • Human relevance not confirmed
  14. 2026 High

    Established COXFA4 as a late-stage COX assembly subunit and identified COXFA4L2 upregulation as a partial compensatory mechanism in patients.

    Evidence 12-family biallelic-variant cohort, fibroblast protein analysis, COX activity and paralog expression

    PMID:42218136

    Open questions at the time
    • Regulation of COXFA4L2 compensation not defined
    • Why compensation is only partial unexplained
  15. 2026 Medium

    Identified VDAC1 as a direct interactor whose upregulation upon COXFA4 loss drives ER stress and neuronal apoptosis.

    Evidence iTRAQ-MS, reciprocal co-localization and Co-IP, knockout mice and VDAC1 knockdown rescue

    PMID:42181741

    Open questions at the time
    • Whether interaction is constitutive or stress-induced unclear
    • Single-lab finding

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved whether COXFA4 functions purely as a structural CIV subunit or also as a transient assembly factor, and how a respiratory subunit mechanistically governs microRNA networks, polyamine metabolism, and innate immune signaling.
  • No structural model of COXFA4 within CIV in the corpus
  • Mechanism coupling CIV status to nuclear/cytoplasmic regulatory pathways unknown
  • Tissue-specific roles of paralog competition not integrated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3
Localization
GO:0005739 mitochondrion 4
Pathway
R-HSA-1430728 Metabolism 2
Partners
C15ORF48COX5BCOX6CCOXFA4L2REEP1VDAC1
Complex memberships
Complex IV (cytochrome c oxidase)

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2012 NDUFA4 (COXFA4) is a subunit of cytochrome c oxidase (Complex IV), not Complex I as previously assumed. Deletion of NDUFA4 does not perturb Complex I activity, but proteomic, genetic, evolutionary, and biochemical analyses demonstrate it plays a role in CIV function and biogenesis. Proteomic analysis, genetic deletion, biochemical assays, evolutionary analysis Cell metabolism High 22902835
2013 Homozygous splice donor site mutations in NDUFA4 cause loss-of-function and isolated cytochrome c oxidase (Complex IV) deficiency in humans. 1D and 2D blue-native PAGE confirmed physical interaction of NDUFA4 with the COX enzyme complex in control muscle, and COX complex without NDUFA4 was detectable with no abnormal subassemblies in patient muscle. Homozygosity mapping, whole-exome sequencing, Western blot, immunocytochemistry, blue-native PAGE Cell reports High 23746447
2017 Re-examination of CcO composition in adult animal tissues suggests NDUFA4 may function as an assembly factor for CcO or respirasomes rather than as a stable 14th structural subunit of CcO in terminally differentiated tissues, challenging its universal classification as a CIV subunit. Biochemical analysis of CcO composition from adult tissue, review and reanalysis of published data Trends in endocrinology and metabolism: TEM Low 28988874
2020 COXFA4 (Coxfa4) is an accessory protein of mitochondrial electron transport chain Complex IV, and its expression during spermatogenesis is mutually exclusive with that of the paralog Coxfa4l3 (C15orf48/Nmes1), indicating Coxfa4 replaces Coxfa4l3 in Complex IV after meiosis. Amino acid sequence comparison, intracellular localization, protein expression analysis during spermatogenesis Mitochondrion Medium 32045714
2022 Loss of NDUFA4 causes mitochondrial stress, leading to leakage of mitochondrial DNA (mtDNA) and upregulation of type I interferon signaling, thereby reducing susceptibility to Zika virus, dengue virus, and SARS-CoV-2 infection in hiPSC-derived cells. GWAS using hiPSC arrays, isogenic loss-of-function cell lines, mechanistic follow-up with mtDNA leakage assays and interferon signaling measurement Cell stem cell Medium 36206731
2022 METTL3 increases m6A methylation of NDUFA4 mRNA via the m6A reader IGF2BP1, promoting NDUFA4 expression. Elevated NDUFA4 promotes glycolysis and mitochondrial fission in gastric cancer cells, and inhibition of mitochondrial fission reverses NDUFA4-induced metabolic effects. RNA immunoprecipitation (RIP), oxygen consumption rate, extracellular acidification rate, flow cytometry, knockdown experiments Cell death & disease Medium 35977935
2022 NDUFA4 knockdown decreases oxygen consumption rate, cellular ATP levels, mitochondrial Complex IV activity, and protein levels of COX6C and COX5B in pancreatic adenocarcinoma cells, demonstrating that NDUFA4 promotes oxidative phosphorylation. Overexpression exerts the opposite effects. siRNA knockdown, oxygen consumption rate measurement, ATP assay, Complex IV activity assay, Western blot, xenograft tumor model Journal of bioenergetics and biomembranes Medium 36307669
2022 REEP1 physically associates with NDUFA4 and plays an important role in preserving the integrity of mitochondrial Complex IV; forced REEP1 expression in SOD1G93A mice augments mitochondrial function and alleviates motor neuron loss. Co-immunoprecipitation (inferred from 'associates with'), in vivo overexpression in transgenic mice, mitochondrial function assays Neuroscience bulletin Medium 36520405
2023 miR-147 directly targets NDUFA4 mRNA (validated by luciferase assay); repression of NDUFA4 by miR-147 induces mitochondrial dysfunction and renal tubular cell death. Overexpression of NDUFA4 prevents miR-147-induced cell death and mitochondrial dysfunction and alleviates cold storage kidney transplant injury in mice. Luciferase reporter assay, anti-miRNA treatment, NDUFA4 overexpression in mouse kidney transplant model, in vitro mitochondrial dysfunction assays Journal of the American Society of Nephrology Medium 37211637
2024 C15ORF48 protein, a structural paralog of NDUFA4, contains a unique C-terminal α-helical domain required for displacing NDUFA4 from Complex IV and promoting its subsequent degradation, thereby suppressing colonocyte metabolism and NF-κB signaling-dependent inflammation. Gene knockout in mice, biochemical fractionation of CIV, domain analysis, NF-κB signaling assays, colitis model Proceedings of the National Academy of Sciences of the United States of America Medium 38917002
2024 Loss of COXFA4 function in Xenopus models leads to downstream deficiency in the ornithine decarboxylase (polyamine) pathway, and small-molecule modulation of this pathway ameliorates cardiac phenotypes caused by coxfa4 loss, linking COXFA4/CIV dysfunction to polyamine metabolism. Xenopus loss-of-function model, transcriptomic analysis, pharmacological modulation of ornithine decarboxylase pathway, cardiac function assessment HGG advances Medium 39967265
2026 NDUFA4 is a late-stage assembly subunit of cytochrome c oxidase (COX). In patients with biallelic COXFA4 pathogenic variants, complete loss of COXFA4 protein is accompanied by upregulation of the paralog COXFA4L2, which partially compensates for residual COX activity in patient-derived fibroblasts. Patient cohort with biallelic variants, protein analysis of fibroblasts, COX activity assays, paralog expression analysis Nature communications High 42218136
2026 NDUFA4 deletion upregulates VDAC1, leading to mitochondrial damage, ER stress, and neuronal apoptosis. NDUFA4 and VDAC1 co-localize and physically interact (co-immunoprecipitation) in cerebellar cells and mouse cerebellar tissue. VDAC1 knockdown partially reverses the cellular damage caused by NDUFA4 deletion. iTRAQ tandem mass spectrometry, co-immunoprecipitation, immunofluorescence, NDUFA4 knockout mice, siRNA knockdown, flow cytometry, Western blot Human mutation Medium 42181741
2023 Ndufa4 inhibits miR-145a-5p expression in cerebellum and neurons; miR-145a-5p directly targets and inhibits Homer1 and Ccnd2 (cyclin D2), suppressing neuronal proliferation and promoting apoptosis. Ndufa4 knockout mice show abnormal brain histology and impaired spatial learning, operating through this miR-145a-5p/Homer1/Ccnd2 axis. Ndufa4 overexpression/shRNA in vitro, Ndufa4 knockout mice, microRNA profiling, luciferase reporter assays for miR-145a-5p targets, behavioral testing Molecular neurobiology Medium 36763283
2020 miR-210 derived from macrophage exosomes directly binds NDUFA4 mRNA (validated by dual-luciferase reporter and pull-down assays), suppressing its expression and impairing mitochondrial Complex IV (CIV) activity and glucose uptake in adipocytes. NDUFA4 overexpression offsets the inhibition of glucose uptake and CIV activity caused by macrophage exosomes. Dual-luciferase reporter assay, RNA pull-down, NDUFA4 overexpression rescue, ELISA for CIV activity, fluorometric glucose uptake assay Journal of diabetes research Medium 32258168
2025 NOC2L decreases expression of NDUFA4 by suppressing histone acetylation at the NDUFA4 locus, remodeling energy metabolism toward aerobic glycolysis and promoting paclitaxel resistance in ovarian cancer cells. Gene expression datasets, loss- and gain-of-function experiments, histone acetylation analysis, metabolic profiling Molecular cancer therapeutics Low 40036166

Source papers

Stage 0 corpus · 32 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 NDUFA4 is a subunit of complex IV of the mammalian electron transport chain. Cell metabolism 315 22902835
2013 NDUFA4 mutations underlie dysfunction of a cytochrome c oxidase subunit linked to human neurological disease. Cell reports 109 23746447
2022 m6A RNA methylation-mediated NDUFA4 promotes cell proliferation and metabolism in gastric cancer. Cell death & disease 83 35977935
2018 LncRNA MAFG-AS1 promotes the progression of colorectal cancer by sponging miR-147b and activation of NDUFA4. Biochemical and biophysical research communications 77 30348529
2020 miR-210 in Exosomes Derived from Macrophages under High Glucose Promotes Mouse Diabetic Obesity Pathogenesis by Suppressing NDUFA4 Expression. Journal of diabetes research 73 32258168
2017 Regulation of Mammalian 13-Subunit Cytochrome c Oxidase and Binding of other Proteins: Role of NDUFA4. Trends in endocrinology and metabolism: TEM 56 28988874
2018 Long non-coding RNA MIF-AS1 promotes gastric cancer cell proliferation and reduces apoptosis to upregulate NDUFA4. Cancer science 50 30238562
2016 Targeted Expression of miR-7 Operated by TTF-1 Promoter Inhibited the Growth of Human Lung Cancer through the NDUFA4 Pathway. Molecular therapy. Nucleic acids 47 28325285
2023 miR-147 Represses NDUFA4, Inducing Mitochondrial Dysfunction and Tubular Damage in Cold Storage Kidney Transplantation. Journal of the American Society of Nephrology : JASN 31 37211637
2015 NDUFA4 expression in clear cell renal cell carcinoma is predictive for cancer-specific survival. American journal of cancer research 21 26609487
2021 MiR-210-3p Enhances Cardiomyocyte Apoptosis and Mitochondrial Dysfunction by Targeting the NDUFA4 Gene in Sepsis-Induced Myocardial Dysfunction. International heart journal 20 33994501
2020 Coxfa4l3, a novel mitochondrial electron transport chain Complex 4 subunit protein, switches from Coxfa4 during spermatogenesis. Mitochondrion 20 32045714
2018 A novel mutation in the NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 4 (Ndufa4) gene links mitochondrial dysfunction to the development of diabetes in a rodent model. Disease models & mechanisms 20 30361421
2022 A human iPSC-array-based GWAS identifies a virus susceptibility locus in the NDUFA4 gene and functional variants. Cell stem cell 17 36206731
1997 Cloning of the human cDNA sequence encoding the NADH:ubiquinone oxidoreductase MLRQ subunit. Biochemistry and molecular biology international 13 9352085
2022 NDUFA4 promotes cell proliferation by enhancing oxidative phosphorylation in pancreatic adenocarcinoma. Journal of bioenergetics and biomembranes 11 36307669
2022 REEP1 Preserves Motor Function in SOD1G93A Mice by Improving Mitochondrial Function via Interaction with NDUFA4. Neuroscience bulletin 10 36520405
2024 The epithelial C15ORF48/miR-147-NDUFA4 axis is an essential regulator of gut inflammation, energy metabolism, and the microbiome. Proceedings of the National Academy of Sciences of the United States of America 9 38917002
2010 Sex-specific genetic dissection of diabetes in a rodent model identifies Ica1 and Ndufa4 as major candidate genes. Physiological genomics 9 20530722
2024 Biallelic NDUFA4 Deletion Causes Mitochondrial Complex IV Deficiency in a Patient with Leigh Syndrome. Genes 8 38674434
2023 NDUFA4 promotes the progression of head and neck paraganglioma by inhibiting ferroptosis. Biochemistry and cell biology = Biochimie et biologie cellulaire 8 37602474
2018 NDUFA4 enhances neuron growth by triggering growth factors and inhibiting neuron apoptosis through Bcl-2 and cytochrome C mediated signaling pathway. American journal of translational research 8 29423002
2025 MiR-147b-3p promotes osteogenesis by targeting NDUFA4 and PI3K/AKT pathway. Journal of orthopaedic surgery and research 7 40038790
2023 Ndufa4 Regulates the Proliferation and Apoptosis of Neurons via miR-145a-5p/Homer1/Ccnd2. Molecular neurobiology 7 36763283
2024 Sesquiterpene lactone from Artemisia argyi inhibited cancer proliferation by inducing apoptosis and ferroptosis via key cell metabolism enzyme NDUFA4. Phytomedicine : international journal of phytotherapy and phytopharmacology 6 39671784
2025 NOC2L Promotes Paclitaxel Resistance in Various Types of Ovarian Cancers by Decreasing NDUFA4 through Histone Acetylation Suppression. Molecular cancer therapeutics 5 40036166
2024 Mitochondrial respiratory chain component NDUFA4: a promising therapeutic target for gastrointestinal cancer. Cancer cell international 4 38443961
2025 Polyamine metabolism is dysregulated in COXFA4-related mitochondrial disease. HGG advances 2 39967265
2023 Isogenic human trophectoderm cells demonstrate the role of NDUFA4 and associated variants in ZIKV infection. iScience 1 37534130
2026 NDUFA4 Deletion Upregulates VDAC1 to Promote Mitochondrial Damage, Endoplasmic Reticulum Expansion, and Neuronal Apoptosis. Human mutation 0 42181741
2026 COXFA4L2 upregulation preserves residual cytochrome c oxidase activity in COXFA4-related Leigh-like encephalopathy. Nature communications 0 42218136
2005 [Expression of MLRQ subunit gene of NADH oxidoreductase and its clinical significance in malignant tumors of digestive system]. Zhonghua yi xue za zhi 0 15949352

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