Affinage

COX7A2L

Cytochrome c oxidase subunit 7A2-like, mitochondrial · UniProt O14548

Length
114 aa
Mass
12.6 kDa
Annotated
2026-06-09
14 papers in source corpus 11 papers cited in narrative 11 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

COX7A2L is a mitochondrial inner-membrane protein that governs the assembly of respiratory chain supercomplexes by binding preferentially to free complex III and, to a lesser extent, complex IV, thereby specifically promoting formation and stabilization of the III2+IV supercomplex (PMID:27545886). Its action is selective rather than essential: COX7A2L is dispensable for the biogenesis, stability, and function of individual OXPHOS complexes, and the bulk of respirasomes (I+III2+IV) assemble independently of it, with roughly 70% of wild-type respirasomes incorporating complex IV via COX7A2 rather than COX7A2L (PMID:27545886, PMID:30428348, PMID:33727070). Consistent with this, knockout cells lose SC III2+IV and the largest megacomplexes while retaining near-normal respiration, and mice lacking functional COX7A2L still form respirasomes (PMID:30428348, PMID:27997587). The functional relevance of COX7A2L lies in dose-dependent modulation of supercomplex abundance: a 3' UTR insertion variant that raises mRNA stability and expression increases supercomplexes and respiration in human myotubes, and reconstituting Cox7a2l in deficient mice raises maximal oxygen consumption, lean mass, and energy expenditure, with expression induced in muscle by exercise (PMID:36253618). Sustained elevation of COX7A2L raises ATP and NAD+ levels, lowers ROS and cellular senescence markers, and extends lifespan in transgenic mice (PMID:41253741). COX7A2L is also recruited into the COX complex under metabolic stress and supports proliferation and energy production in breast cancer and mammary epithelial cells (PMID:27550821).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2014 High

    Established that respirasome and complex IV-supercomplex organization can proceed independently of COX7A2L isoform status, challenging the idea that COX7A2L is an obligate respirasome assembly factor.

    Evidence BN-PAGE, respirometry, and Lrpprc knockout across mouse strains differing in Cox7a2l isoform

    PMID:25470551

    Open questions at the time
    • Did not resolve which supercomplex species specifically depend on COX7A2L
    • Mouse strain isoform differences confounded with other background variation
  2. 2016 High

    Defined the specific molecular role of COX7A2L as a factor that binds free complex III to stabilize the III2+IV supercomplex without affecting individual complexes or respirasomes, narrowing its function to a discrete assembly step.

    Evidence Native gel electrophoresis, co-immunoprecipitation, and functional respiratory assays in human and mouse cells; complementary BN-PAGE in C57BL/6 liver mitochondria lacking functional SCAFI

    PMID:27545886 PMID:27997587

    Open questions at the time
    • Structural basis of preferential complex III versus complex IV binding not resolved
    • Physiological consequence of losing III2+IV supercomplex unclear
  3. 2016 Medium

    Linked COX7A2L to stress-induced energy metabolism and a pro-proliferative phenotype, indicating context-dependent functional importance beyond baseline assembly.

    Evidence Gain/loss-of-function with OCR/ECAR energy assays and proliferation/invasion assays in breast cancer and mammary epithelial cells

    PMID:27550821

    Open questions at the time
    • Mechanism connecting supercomplex assembly to proliferation not defined
    • Single cancer context; generality untested
  4. 2018 High

    Showed via clean CRISPR knockout that loss of COX7A2L removes SC III2+IV and megacomplexes but leaves complex III, complex IV biogenesis, and respiration normal, establishing it as dispensable for baseline OXPHOS function.

    Evidence CRISPR-Cas9 knockout, BN-PAGE, in-gel activity, pulse-chase assembly, and Seahorse respirometry under stress in two cell lines

    PMID:30428348

    Open questions at the time
    • Why III2+IV stabilization is functionally non-essential in these cells unexplained
    • Possible tissue- or stress-specific requirement not addressed
  5. 2021 High

    Resolved the structural heterogeneity of respirasomes, demonstrating that COX7A2 and COX7A2L define distinct co-existing supercomplex populations, with COX7A2-based respirasomes predominating.

    Evidence SILAC-based complexome profiling and quantitative mass spectrometry of CRISPR knockout HEK293T cells

    PMID:33727070

    Open questions at the time
    • Functional differences between COX7A2- and COX7A2L-defined respirasomes unknown
    • Regulation of the choice between COX7A2 and COX7A2L not addressed
  6. 2022 High

    Connected COX7A2L expression dosage to whole-organism physiology, showing a 3' UTR variant raises expression, supercomplexes, and respiration, and that reconstitution improves metabolic phenotypes and exercise responsiveness.

    Evidence cis-eQTL mapping, mRNA stability assays, human myotube respirometry, Cox7a2l reconstitution in mice with metabolic phenotyping and BN-PAGE

    PMID:36253618

    Open questions at the time
    • Causal chain from supercomplex abundance to energy expenditure not fully traced
    • Whether exercise induction is transcriptional or post-transcriptional unresolved
  7. 2024 Medium

    Provided human in vivo evidence that COX7A2L incorporation into III2+IV1 supercomplexes is exercise-mode-specific, linking the assembly mechanism to physiological adaptation.

    Evidence Quantitative complexome profiling of human skeletal muscle biopsies after sprint-interval versus moderate-intensity training (preprint)

    PMID:bio_10.1101_2024.12.19.629456

    Open questions at the time
    • Preprint, not peer-reviewed
    • Mechanism of training-mode specificity unknown
  8. 2024 Low

    Implicated transcriptional control of COX7A2L by TCF4 with downstream effects on Wnt/β-catenin signaling and apoptosis under hypoxia/reoxygenation.

    Evidence Overexpression/knockdown and rescue with Western blotting for Wnt pathway proteins and apoptosis assays in vitro

    PMID:39499704

    Open questions at the time
    • No direct demonstration of TCF4 binding to the COX7A2L promoter
    • Single lab, in vitro only
    • Mechanistic link between supercomplex protein and Wnt signaling unexplained
  9. 2025 Medium

    Tested whether COX7A2L drives aging-related metabolic benefits, showing transgenic elevation raises ATP and NAD+, lowers ROS and senescence, and extends lifespan.

    Evidence Transgenic mouse model with ATP/NAD+/ROS biochemistry, senescence-associated β-galactosidase assay, and snRNA-seq of white adipose tissue

    PMID:41253741

    Open questions at the time
    • Single lab, no independent replication
    • Causal mechanism from supercomplex assembly to SASP downregulation not established
  10. 2025 Medium

    Tested cardiomyocyte dependence on COX7A2L and found no measurable effect on viability or mitochondrial respiration, reinforcing tissue/context-specificity of its functional importance.

    Evidence Validated overexpression/knockdown with MTT viability and Seahorse Mito Stress Test under isoproterenol stimulation in AC16 cardiomyocytes

    PMID:40560843

    Open questions at the time
    • Negative result in a single cell type does not exclude effects elsewhere
    • No assessment of supercomplex assembly in this model

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how COX7A2L-defined supercomplexes confer the organismal metabolic, fitness, and longevity benefits despite being dispensable for baseline respiration in many cellular contexts.
  • No mechanistic link between III2+IV supercomplex abundance and ATP/NAD+/ROS phenotypes
  • Tissue-specific functional requirement not systematically mapped
  • Structural basis of preferential complex III binding undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-1430728 Metabolism 3
Complex memberships
cytochrome c oxidase (complex IV)respirasome (I+III2+IV)respiratory supercomplex III2+IV

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2016 COX7A2L binds primarily to free mitochondrial complex III and, to a minor extent, to complex IV, specifically promoting stabilization of the III2+IV supercomplex without affecting respirasome (I+III2+IV) formation or the biogenesis, stabilization, and function of individual OXPHOS complexes. Native gel electrophoresis, co-immunoprecipitation, and functional respiratory assays in human and mouse cells Cell reports High 27545886
2014 The short COX7a2l isoform present in C57BL/6 mice does not prevent formation of complex IV-containing supercomplexes or respirasomes; supercomplex organization is independent of COX7a2l isoforms in mice. Loss of complex IV (via Lrpprc knockout) compromises respirasome formation. Multiple complementary experimental approaches including BN-PAGE, respirometry, and mouse knockout of Lrpprc in mice with different COX7a2l isoforms Cell metabolism High 25470551
2018 COX7A2L-knockout (KO) HEK293T and U87 cells lack SC III2+IV but show enhanced complex III steady-state levels, activity, and assembly rate, normal de novo complex IV biogenesis, and delayed but ultimately normal respirasome steady-state levels; only larger megacomplexes (SCs I1-2+III2+IV2-n) were absent. Functional substrate-driven competition assays showed normal mitochondrial respiration under standard and stress conditions in COX7A2L-KO cells. CRISPR-Cas9 knockout, BN-PAGE, in-gel activity assays, radioactive pulse-chase assembly assays, Seahorse respirometry under multiple stress conditions Cell reports High 30428348
2021 SILAC-based complexome profiling of SCAFI (COX7A2L) knockout HEK293T cells showed preferential loss of SC III2+IV and a minor subset of respirasomes, without affecting OXPHOS function. Approximately 70% of respirasomes in wild-type cells contain COX7A2 (not SCAFI) and are present at similar levels in SCAFI-KO cells, demonstrating co-existence of structurally distinct respirasomes defined by preferential binding of complex IV via COX7A2 rather than SCAFI. SILAC-based complexome profiling, CRISPR-Cas9 knockout, quantitative mass spectrometry Biochimica et biophysica acta. Bioenergetics High 33727070
2016 In liver mitochondria of C57BL/6 mice (which lack functional SCAFI/COX7A2L protein due to a 6-bp deletion), complex IV is mainly present as monomers and dimers with only low amounts found in combination with complexes I and III, and the main supercomplex comprises only complexes I and III — supporting a role for COX7A2L/SCAFI in incorporating complex IV into supercomplexes. SCAFI heterozygosity reduced SCAFI protein but did not affect respirasome assembly. BN-PAGE, immunoblotting, comparison of mice with different SCAFI isoforms on Bcs1l mutant background PloS one Medium 27997587
2016 COX7AR (COX7A2L) is incorporated into the mitochondrial COX complex under cellular stress that stimulates energy metabolism. Gain- and loss-of-function analysis demonstrated that COX7AR is required for human breast cancer cells to maintain higher rates of proliferation, clone formation, and invasion, and promotes cellular energy production in human mammary epithelial cells. Gain- and loss-of-function (overexpression/siRNA knockdown), cellular energy production assays (OCR/ECAR), proliferation/invasion assays Scientific reports Medium 27550821
2022 A 10-bp insertion in the COX7A2L 3' UTR increases mRNA stability and expression; human myotubes harboring this insertion have more supercomplexes and increased respiration. Specific reconstitution of Cox7a2l expression in C57BL/6J mice leads to higher maximal oxygen consumption, increased lean mass, and increased energy expenditure. Cox7a2l expression is induced specifically in mouse muscle upon exercise. cis-eQTL mapping, mRNA stability assays, Seahorse respirometry in human myotubes, Cox7a2l reconstitution in mice with metabolic phenotyping, BN-PAGE for supercomplex quantification Nature metabolism High 36253618
2025 COX7RP (COX7A2L)-transgenic mice show elevated ATP and NAD+ levels, reduced ROS production, decreased senescence-associated β-galactosidase levels, and significant lifespan extension. snRNA-seq revealed downregulation of senescence-associated secretory phenotype (SASP) genes in old COX7RP-Tg white adipose tissue adipocytes. Transgenic mouse model, metabolic biochemistry (ATP, NAD+, ROS), β-galactosidase senescence assay, single-nucleus RNA sequencing Aging cell Medium 41253741
2024 COX7A2L protein significantly accumulates in III2+IV1 respiratory supercomplexes specifically following sprint-interval training (SIT) but not moderate-intensity continuous training (MICT) in human skeletal muscle, indicating exercise-mode-specific regulation of COX7A2L incorporation into supercomplexes. Quantitative proteomics/complexome profiling of human skeletal muscle biopsies after 8-week training interventions bioRxivpreprint Medium bio_10.1101_2024.12.19.629456
2024 TCF4 transcriptionally regulates COX7A2L expression; TCF4 overexpression increases COX7A2L levels, and COX7A2L knockdown counteracts TCF4-induced promotion of Wnt/β-catenin signaling pathway proteins (c-myc, β-catenin, cyclin D1) and apoptosis in hypoxia/reoxygenation-treated cells. Overexpression and knockdown experiments, rescue assays, Western blotting for Wnt/β-catenin pathway proteins, apoptosis and proliferation assays PloS one Low 39499704
2025 Overexpression and knockdown of COX7A2L in human AC16 cardiomyocytes did not significantly affect cell viability or mitochondrial function (oxygen consumption rate parameters), even under isoproterenol-stimulated increased energy demand — a negative result. Overexpression and knockdown validated by sandwich ELISA, MTT assay, Seahorse XF Cell Mito Stress Test with isoproterenol stimulation PloS one Medium 40560843

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2016 COX7A2L Is a Mitochondrial Complex III Binding Protein that Stabilizes the III2+IV Supercomplex without Affecting Respirasome Formation. Cell reports 98 27545886
2014 The respiratory chain supercomplex organization is independent of COX7a2l isoforms. Cell metabolism 83 25470551
2018 Human COX7A2L Regulates Complex III Biogenesis and Promotes Supercomplex Organization Remodeling without Affecting Mitochondrial Bioenergetics. Cell reports 57 30428348
2016 COX7AR is a Stress-inducible Mitochondrial COX Subunit that Promotes Breast Cancer Malignancy. Scientific reports 32 27550821
2022 COX7A2L genetic variants determine cardiorespiratory fitness in mice and human. Nature metabolism 29 36253618
2021 SILAC-based complexome profiling dissects the structural organization of the human respiratory supercomplexes in SCAFIKO cells. Biochimica et biophysica acta. Bioenergetics 19 33727070
2020 Overexpression of COX7RP promotes tumor growth and metastasis by inducing ROS production in hepatocellular carcinoma cells. American journal of cancer research 16 32509385
2016 COX7A2L/SCAFI and Pre-Complex III Modify Respiratory Chain Supercomplex Formation in Different Mouse Strains with a Bcs1l Mutation. PloS one 16 27997587
2022 Emerging Roles of COX7RP and Mitochondrial Oxidative Phosphorylation in Breast Cancer. Frontiers in cell and developmental biology 11 35178385
2020 Coexisting of COX7A2L-ALK, LINC01210-ALK, ATP13A4-ALK and Acquired SLCO2A1-ALK in a Lung Adenocarcinoma with Rearrangements Loss During the Treatment of Crizotinib and Ceritinib: A Case Report. OncoTargets and therapy 7 32903930
2024 TCF4 promotes apoptosis and Wnt/β-catenin signaling pathway in acute kidney injury via transcriptional regulation of COX7A2L. PloS one 2 39499704
2023 [Ceritinib as First-line Treatment for Advanced Lung Adenocarcinoma 
with COX7A2L-ALK Fusion: A Case Report and Literature Review]. Zhongguo fei ai za zhi = Chinese journal of lung cancer 1 37183647
2025 Investigating the cardiorespiratory fitness gene COX7A2L in cardiomyocytes: Viability and mitochondrial function. PloS one 0 40560843
2025 Mitochondrial Respiratory Supercomplex Assembly Factor COX7RP Contributes to Lifespan Extension in Mice. Aging cell 0 41253741

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