Affinage

PDHX

Pyruvate dehydrogenase protein X component, mitochondrial · UniProt O00330

Length
501 aa
Mass
54.1 kDa
Annotated
2026-06-10
21 papers in source corpus 10 papers cited in narrative 10 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

PDHX (E3-binding protein, E3BP) is a structural subunit of the human pyruvate dehydrogenase complex (PDC) that integrates into the heterogeneous E2/E3BP core and is required for the conversion of pyruvate to acetyl-CoA (PMID:21627584, PMID:24935220). Within the native core, PDHX assembles with E2 in a defined stoichiometry (48E2+12E3BP) that maximizes structural flexibility while balancing E1 and E3 binding for optimal catalysis, and it recruits E3 to the complex with 2:1 stoichiometry (PMID:21627584). Its lipoyl (L3) domain participates in the interaction with the regulatory kinases PDK1 and PDK2 within the intact E2·E3BP core (PMID:25436986). Loss-of-function mutations in PDHX cause pyruvate dehydrogenase complex deficiency, with absence of the E3BP subunit abolishing PDH activity (PMID:16843025). PDHX is required to maintain PDH activity and ATP production, and its expression is post-transcriptionally suppressed by miR-26a, miR-27b, and miR-181b-5p, each binding the PDHX 3′-UTR to shift metabolism toward glycolysis in cancer contexts (PMID:24935220, PMID:30012170, PMID:34485121, PMID:33964039). PDHX is also a frequent autoantibody target in primary biliary cirrhosis, with reactivity directed exclusively to its lipoic acid-binding domain (PMID:10094940).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 1999 Medium

    Established which structural element of E3BP is the immunodominant B-cell epitope in primary biliary cirrhosis, localizing autoreactivity to a specific domain rather than the whole protein.

    Evidence Recombinant lipoic domain expression, ELISA, immunoblot, and pre-absorption with PBC patient sera

    PMID:10094940

    Open questions at the time
    • Does not address how the lipoic domain becomes accessible/modified to trigger autoimmunity
    • Does not link the antibody target to disease causation
  2. 2006 Medium

    Demonstrated that PDHX loss-of-function causes pyruvate dehydrogenase complex deficiency, establishing the gene as essential for PDC function in humans.

    Evidence Western blot and PDHc activity assay in patient fibroblasts with a homozygous exon 10 deletion

    PMID:16843025

    Open questions at the time
    • Single case report
    • Does not resolve how absence of E3BP structurally disables the core
  3. 2006 Medium

    Clarified that, despite being a major antibody antigen in PBC, E3BP is not a dominant T-cell autoantigen, separating humoral from cellular autoimmune targeting.

    Evidence Peripheral blood T-cell proliferation assays with purified recombinant E2 and E3BP in patients and controls

    PMID:16629643

    Open questions at the time
    • Negative finding; does not explain the antibody/T-cell discordance mechanistically
  4. 2011 High

    Resolved the stoichiometry and assembly logic of the E2/E3BP core, showing the native 48E2+12E3BP arrangement optimizes flexibility and E1/E3 binding for catalysis.

    Evidence AUC, SANS, ITC, and mathematical modelling of recombinant and native PDC cores

    PMID:21627584

    Open questions at the time
    • Does not provide an atomic-resolution structure of the assembled human core
    • Heterogeneity of stoichiometry in vivo not directly quantified in tissue
  5. 2014 High

    Mapped how the E2·E3BP core engages the regulatory kinases, defining domain-specific PDK1/PDK2 binding and differential conformational effects.

    Evidence HDX-MS and NMR with truncated and intact E2·E3BP core proteins

    PMID:25436986

    Open questions at the time
    • Does not establish functional consequence of differential plasticity on kinase activity
    • PDK3/PDK4 interactions not addressed
  6. 2014 Medium

    Identified the first microRNA-mediated post-transcriptional control of PDHX, linking its suppression to a glycolytic metabolic shift in cancer.

    Evidence Dual-luciferase 3′-UTR reporter, Western blot/RT-PCR, and metabolite assays after miR-26a manipulation in colorectal cancer cells

    PMID:24935220

    Open questions at the time
    • Single lab and cell-line context
    • In vivo relevance not tested
  7. 2018 Medium

    Extended the miRNA-regulation model to breast cancer, tying PDHX suppression to a measurable glycolytic flux shift and proliferation.

    Evidence Luciferase 3′-UTR reporter, Seahorse flux analysis, metabolite and proliferation assays after miR-27b manipulation

    PMID:30012170

    Open questions at the time
    • Single lab
    • Does not isolate PDHX as the sole effector of the metabolic phenotype
  8. 2020 High

    Showed that the E3BP-analog assembly mechanism is not universal, with fungal protein X occupying an interior core site distinct from the mammalian E2-substituting arrangement.

    Evidence Cryo-EM reconstruction of Neurospora crassa PDC with symmetry analyses

    PMID:32938938

    Open questions at the time
    • Direct structural comparison to a human core at equivalent resolution not provided
    • Functional consequence of fungal-specific geometry not tested
  9. 2021 Medium

    Connected PDHX function to cancer stemness and growth, establishing that PDHX expression sustains PDH activity, ATP output, and tumor maintenance.

    Evidence siRNA knockdown, PDH activity and ATP assays, stem-cell proliferation assays, and xenografts in ESCC; plus miR-181b-5p 3′-UTR validation and metabolic rescue in gallbladder cancer

    PMID:33964039 PMID:34485121

    Open questions at the time
    • Co-amplification with CD44 leaves their independent contributions unresolved
    • Single lab per cancer context

Open questions

Synthesis pass · forward-looking unresolved questions
  • How PDHX integration and its regulation of kinase access dynamically tune PDC flux in different physiological and disease states remains unresolved.
  • No atomic-resolution structure of the assembled human E2/E3BP core with bound E3 and PDKs
  • Mechanism linking miRNA suppression to in vivo metabolic reprogramming not fully causally established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 2 GO:0005198 structural molecule activity 1
Localization
GO:0005739 mitochondrion 1
Pathway
R-HSA-1430728 Metabolism 3
Partners
DLATDLDPDK1PDK2
Complex memberships
pyruvate dehydrogenase complex (PDC)

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 The human PDC E2/E3BP core exists as a heterogeneous population of assemblies; recombinant core produced with excess E3BP yields 40E2+20E3BP stoichiometry, while native bovine core is 48E2+12E3BP. Both cores bind E3 with 2:1 stoichiometry, and mathematical modelling indicates 48E2+12E3BP maximizes flexibility while balancing E1 and E3 binding for optimal catalysis. Analytical ultracentrifugation, small-angle neutron scattering, isothermal titration calorimetry, and mathematical modelling of recombinant and native PDC core assemblies The Biochemical journal High 21627584
2014 The E2·E3BP core interacts with PDK1 and PDK2 at defined loci: the L2 lipoyl domain of E2 preferentially binds PDK2 over PDK1 in the context of the intact core; L3 of E3BP shows moderate interaction with both PDKs. The intact E2·E3BP core induces greater conformational plasticity in PDK1 than PDK2. H/D exchange mass spectrometry (HDX-MS) and NMR with truncated and intact E2·E3BP core proteins Biochemistry High 25436986
2020 In the fungal PDC ortholog, protein X (PX; functional analog of mammalian E3BP) is located interior to the PDC core rather than substituting E2 subunits as in mammals; steric occlusion limits PX binding, resulting in predominantly tetrahedral symmetry. The PX-binding site is conserved in and specific to fungi, distinct from the mammalian E3BP mechanism. Cryo-electron microscopy reconstruction of Neurospora crassa PDC Nature communications High 32938938
1999 Autoantibodies in primary biliary cirrhosis (PBC) directed against E3BP (PDHX) are targeted exclusively to its lipoic acid-binding domain; pre-absorption of patient sera with the E3BP lipoic domain completely abolished all reactivity with the full-length protein. Recombinant protein expression of E3BP lipoic domain, ELISA, immunoblotting, and pre-absorption experiments with PBC patient sera Hepatology (Baltimore, Md.) Medium 10094940
2014 miR-26a directly binds the 3′-UTR of PDHX mRNA and suppresses PDHX expression, resulting in reduced conversion of pyruvate to acetyl-CoA (decreased acetyl-CoA, increased pyruvate accumulation) in colorectal cancer cells. Dual-luciferase reporter assay for 3′-UTR targeting; Western blot and RT-PCR for protein/mRNA; metabolite assays (glucose consumption, lactate, pyruvate, acetyl-CoA) after miR-26a overexpression or inhibition in HCT116 cells BMC cancer Medium 24935220
2018 miR-27b directly targets PDHX mRNA via its 3′-UTR and suppresses PDHX protein expression in breast cancer cells, shifting metabolism toward glycolysis (increased lactate, decreased citrate and mitochondrial oxidation) and promoting cell proliferation. Luciferase 3′-UTR reporter assay; RT-PCR; Western blot; Seahorse metabolic flux analysis; metabolite assays; cell proliferation assays after miR-27b manipulation Molecular cancer Medium 30012170
2021 miR-181b-5p directly targets PDHX mRNA (validated by dual-luciferase reporter assay), and its inhibition upregulates PDHX protein, reversing hypoxia-induced increases in glucose consumption and lactate production in gallbladder cancer cells. Dual-luciferase reporter assay; Western blot; glucose and lactate metabolite assays; CCK-8 viability and Transwell migration assays after miR-181b-5p antagomir treatment Frontiers in oncology Medium 34485121
2021 PDHX expression is required for maintenance of pyruvate dehydrogenase (PDH) activity and ATP production in esophageal squamous cell carcinoma (ESCC); PDHX knockdown inhibits cancer stem cell proliferation and in vivo tumor growth. PDHX and CD44 are co-amplified at 11p13 and coordinately support cancer stemness. siRNA knockdown of PDHX; PDH activity assay; ATP production assay; cancer stem cell proliferation assay; in vivo xenograft tumor growth experiments Cancer science Medium 33964039
2006 Loss-of-function mutations in PDHX (encoding E3-binding protein/E3BP) cause pyruvate dehydrogenase complex deficiency; the E3BP subunit is undetectable by Western blot in patient fibroblasts carrying a homozygous deletion of exon 10 (3913 bp deletion in PDHX). Western blot of patient-derived fibroblasts; long-range PCR; direct sequencing of deletion breakpoints; PDHc activity assay Molecular genetics and metabolism Medium 16843025
2006 T-cell proliferative responses to PDC-E3BP (PDHX protein) are absent or secondary to E2 responses in PBC patients, demonstrating that E3BP is not a dominant T-cell autoantigen despite being a frequent antibody target. Peripheral blood T-cell proliferation assay with purified recombinant human PDC-E2 and PDC-E3BP in 20 PBC patients and 10 controls Liver international Medium 16629643

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 MicroRNA-26a regulates glucose metabolism by direct targeting PDHX in colorectal cancer cells. BMC cancer 98 24935220
2010 Identification of a systemic lupus erythematosus susceptibility locus at 11p13 between PDHX and CD44 in a multiethnic study. American journal of human genetics 67 21194677
1999 Autoepitope mapping and reactivity of autoantibodies to the dihydrolipoamide dehydrogenase-binding protein (E3BP) and the glycine cleavage proteins in primary biliary cirrhosis. Hepatology (Baltimore, Md.) 61 10094940
2018 Suppression of PDHX by microRNA-27b deregulates cell metabolism and promotes growth in breast cancer. Molecular cancer 57 30012170
2007 A large genomic deletion in the PDHX gene caused by the retrotranspositional insertion of a full-length LINE-1 element. Human mutation 44 17152059
2020 Arrangement and symmetry of the fungal E3BP-containing core of the pyruvate dehydrogenase complex. Nature communications 24 32938938
2011 Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly. The Biochemical journal 24 21627584
2006 Leigh's disease due to a new mutation in the PDHX gene. Annals of neurology 24 16566017
2020 miR-26a is Involved in Glycometabolism and Affects Boar Sperm Viability by Targeting PDHX. Cells 20 31936222
2021 Identification of PDHX as a metabolic target for esophageal squamous cell carcinoma. Cancer science 19 33964039
2021 Downregulation of miR-181b-5p Inhibits the Viability, Migration, and Glycolysis of Gallbladder Cancer by Upregulating PDHX Under Hypoxia. Frontiers in oncology 17 34485121
2014 Founder p.Arg 446* mutation in the PDHX gene explains over half of cases with congenital lactic acidosis in Roma children. Molecular genetics and metabolism 16 25087164
2021 Circular RNA_PDHX Promotes the Proliferation and Invasion of Prostate Cancer by Sponging MiR-378a-3p. Frontiers in cell and developmental biology 15 33634097
2023 Cuproptosis-related gene PDHX and heat stress-related HSPD1 as potential key drivers associated with cell stemness, aberrant metabolism and immunosuppression in esophageal carcinoma. International immunopharmacology 14 36889194
2014 Elucidation of the interaction loci of the human pyruvate dehydrogenase complex E2·E3BP core with pyruvate dehydrogenase kinase 1 and kinase 2 by H/D exchange mass spectrometry and nuclear magnetic resonance. Biochemistry 14 25436986
2012 Pyruvate dehydrogenase deficiency caused by a new mutation of PDHX gene in two Moroccan patients. European journal of medical genetics 11 22766002
2006 A novel gross deletion caused by non-homologous recombination of the PDHX gene in a patient with pyruvate dehydrogenase deficiency. Molecular genetics and metabolism 10 16843025
2016 Complex genetic findings in a female patient with pyruvate dehydrogenase complex deficiency: Null mutations in the PDHX gene associated with unusual expression of the testis-specific PDHA2 gene in her somatic cells. Gene 4 27343776
2024 An integrated multi-omics approach allowed ultra-rapid diagnosis of a deep intronic pathogenic variant in PDHX and precision treatment in a neonate critically ill with lactic acidosis. Mitochondrion 2 39413893
2006 PDC-E3BP is not a dominant T-cell autoantigen in primary biliary cirrhosis. Liver international : official journal of the International Association for the Study of the Liver 2 16629643
2026 Integrating multi-omics approaches reveals metabolic reprogramming and identifies PDHX as a candidate node in triptolide-treated non-small Cell lung cancer. Frontiers in pharmacology 0 42093886

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