{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nOGDH, a central enzyme of the mitochondrial 2‑oxoglutarate dehydrogenase complex (KGDHC), serves as a rate‐limiting step in the tricarboxylic acid (TCA) cycle. One study showed that loss of OGDH complex activity leads to an accumulation of L‑2‑hydroxyglutarate, which in turn inhibits HIFα prolyl hydroxylases and 2‑oxoglutarate–dependent dioxygenases, thereby stabilizing HIF1α under aerobic conditions and linking mitochondrial metabolism to oxygen sensing and broad epigenetic regulation in tumorigenesis."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nDeficiencies in OGDH activity are implicated in neurological and developmental disorders. Reduced activity of the KGDHC in Alzheimer’s disease brains perturbs mitochondrial substrate‑level phosphorylation and calcium homeostasis, contributing to neuronal dysfunction. In parallel, human genetic studies have linked homozygous loss‑of‑function variants in OGDH to global developmental delay, movement disorders, and metabolic decompensation, while exercise studies further correlate enhanced OGDH activity with improved mitochondrial oxidative capacity. Moreover, modulation of OGDH complex subunit levels has been shown to affect cellular reactive oxygen species and vulnerability to oxidative stress, underscoring its pivotal role in neuronal bioenergetics."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "2", "end_ref": "7"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nOGDH activity is tightly regulated by post‑translational modifications and alternative splicing. For instance, ubiquitin‑mediated degradation of a key E2 component of the OGDH complex by the RING finger ligase Siah2 can diminish enzyme levels, while lysine desuccinylation of OGDH by SIRT5 suppresses complex activity—leading to altered mitochondrial membrane potential, ATP production, and redox balance in gastric cancer cells. In addition, distinct tissue‑specific splice variants of the enzyme’s E1 subunit have been identified that render the complex insensitive to Ca²⁺, thereby tuning OGDH responsiveness to the diverse metabolic and signaling needs of different cell types."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "10"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nOGDH also plays a critical role in the metabolic reprogramming observed in cancer. In oncogenic PIK3CA‑mutant cancers, OGDH sustains aspartate production and NAD⁺ regeneration via the malate‑aspartate shuttle, and its suppression causes 2‑oxoglutarate accumulation that depletes aspartate, selectively impairing cell proliferation. Furthermore, frameshift mutations in OGDH have been detected exclusively in microsatellite instability‐high gastrointestinal tumors, and targeted inhibition of OGDH (with agents such as CPI‑613) has been shown to synergize with Bcl‑xL inhibitors to induce an integrated stress response and kill glioblastoma cells."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "11", "end_ref": "13"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nFinally, the metabolic versatility of OGDH is further highlighted by its participation in hybrid dehydrogenase complexes. In settings such as glutaric aciduria type 1, a hybrid complex incorporating DHTKD1 and OGDH broadens substrate specificity to include metabolites like 2‑oxoadipate, thereby linking lysine degradation and fatty acid β‑oxidation to the TCA cycle."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "14"}]}, {"type": "t", "text": ""}]}]}]}]}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Stephen P Burr, Ana S H Costa, Guinevere L Grice, et al. 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