title: Inactivation and reactivation of the mitochondrial α-ketoglutarate dehydrogenase complex.
abstract: Reduced brain metabolism is an invariant feature of Alzheimer Disease (AD) that is highly correlated to the decline in brain functions. Decreased activities of key tricarboxylic acid cycle (TCA) cycle enzymes may underlie this abnormality and are highly correlated to the clinical state of the patient. The activity of the α-ketoglutarate dehydrogenase complex (KGDHC), an arguably rate-limiting enzyme of the TCA cycle, declines with AD, but the mechanism of inactivation and whether it can be reversed remains unknown. KGDHC consists of multiple copies of three subunits. KGDHC is sensitive to oxidative stress, which is pervasive in AD brain. The present studies tested the mechanism for the peroxynitrite-induced inactivation and subsequent reactivation of purified and cellular KGDHC. Peroxynitrite inhibited purified KGDHC activity in a dose-dependent manner and reduced subunit immunoreactivity and increased nitrotyrosine immunoreactivity. Nano-LC-MS/MS showed that the inactivation was related to nitration of specific tyrosine residues in the three subunits. GSH diminished the nitrotyrosine immunoreactivity of peroxynitrite-treated KGDHC, restored the activity and the immunoreactivity for KGDHC. Nano-LC-MS/MS showed this was related to de-nitration of specific tyrosine residues, suggesting KGDHC may have a denitrase activity. Treatment of N2a cells with peroxynitrite for 5 min followed by recovery of cells for 24 h reduced KGDHC activity and increased nitrotyrosine immunoreactivity. Increasing cellular GSH in peroxynitrite-treated cells rescued KGDHC activity to the control level. The results suggest that restoring KGDHC activity is possible and may be a useful therapeutic approach in neurodegenerative diseases.
authors: Department of Neurology & Neuroscience, Weill Cornell Medical College/Burke Medical Research Institute, White Plains, New York 10605, USA.
authors: Qingli
authors: Q
authors: Shi
authors: Hui
authors: H
authors: Xu
authors: Haiqiang
authors: H
authors: Yu
authors: Nawei
authors: N
authors: Zhang
authors: Yaozu
authors: Y
authors: Ye
authors: Alvaro G
authors: AG
authors: Estevez
authors: Haiteng
authors: H
authors: Deng
authors: Gary E
authors: GE
authors: Gibson
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology / Q000628:therapy; D001921:Brain / Q000201:enzymology; D002460:Cell Line; D002952:Citric Acid Cycle / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007655:Ketoglutarate Dehydrogenase Complex / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
chemical_list: D024101:Mitochondrial Proteins; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D007655:Ketoglutarate Dehydrogenase Complex