title: The negative impact of α-ketoglutarate dehydrogenase complex deficiency on matrix substrate-level phosphorylation.
abstract: A decline in α-ketoglutarate dehydrogenase complex (KGDHC) activity has been associated with neurodegeneration. Provision of succinyl-CoA by KGDHC is essential for generation of matrix ATP (or GTP) by substrate-level phosphorylation catalyzed by succinyl-CoA ligase. Here, we demonstrate ATP consumption in respiration-impaired isolated and in situ neuronal somal mitochondria from transgenic mice with a deficiency of either dihydrolipoyl succinyltransferase (DLST) or dihydrolipoyl dehydrogenase (DLD) that exhibit a 20-48% decrease in KGDHC activity. Import of ATP into the mitochondrial matrix of transgenic mice was attributed to a shift in the reversal potential of the adenine nucleotide translocase toward more negative values due to diminished matrix substrate-level phosphorylation, which causes the translocase to reverse prematurely. Immunoreactivity of all three subunits of succinyl-CoA ligase and maximal enzymatic activity were unaffected in transgenic mice as compared to wild-type littermates. Therefore, decreased matrix substrate-level phosphorylation was due to diminished provision of succinyl-CoA. These results were corroborated further by the finding that mitochondria from wild-type mice respiring on substrates supporting substrate-level phosphorylation exhibited ~30% higher ADP-ATP exchange rates compared to those obtained from DLST(+/-) or DLD(+/-) littermates. We propose that KGDHC-associated pathologies are a consequence of the inability of respiration-impaired mitochondria to rely on "in-house" mitochondrial ATP reserves.
authors.affiliation: Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Gergely
authors.initials: G
authors.lastname: Kiss
authors.forename: Csaba
authors.initials: C
authors.lastname: Konrad
authors.forename: Judit
authors.initials: J
authors.lastname: Doczi
authors.forename: Anatoly A
authors.initials: AA
authors.lastname: Starkov
authors.forename: Hibiki
authors.initials: H
authors.lastname: Kawamata
authors.forename: Giovanni
authors.initials: G
authors.lastname: Manfredi
authors.forename: Steven F
authors.initials: SF
authors.lastname: Zhang
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gibson
authors.forename: M Flint
authors.initials: MF
authors.lastname: Beal
authors.forename: Vera
authors.initials: V
authors.lastname: Adam-Vizi
authors.forename: Christos
authors.initials: C
authors.lastname: Chinopoulos
mesh_terms: D000217:Acyltransferases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D000592:Amino Acid Metabolism, Inborn Errors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D008058:Dihydrolipoamide Dehydrogenase / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D005260:Female; D007655:Ketoglutarate Dehydrogenase Complex / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010766:Phosphorylation; D013379:Substrate Specificity
chemical_list: D007655:Ketoglutarate Dehydrogenase Complex; D008058:Dihydrolipoamide Dehydrogenase; D000217:Acyltransferases; C021515:dihydrolipoamide succinyltransferase
keywords: F0–F1 ATP synthase; adenine nucleotide translocase; reversal potential; succinyl-CoA ligase