title: Control of oxygen free radical formation from mitochondrial complex I: roles for protein kinase A and pyruvate dehydrogenase kinase.
abstract: Human NADH CoQ oxidoreductase is composed of a total of 43 subunits and has been demonstrated to be a major site for the production of superoxide by mitochondria. Incubation of rat heart mitochondria with ATP resulted in the phosphorylation of two mitochondrial membrane proteins, one with a M(r) of 6 kDa consistent with the NDUFA1 (MWFE), and one at 18kDa consistent with either NDUFS4 (AQDQ) or NDUFB7 (B18). Phosphorylation of both subunits was enhanced by cAMP derivatives and protein kinase A (PKA) and was inhibited by PKA inhibitors (PKAi). When mitochondrial membranes were incubated with pyruvate dehydrogenase kinase, phosphorylation of an 18kDa protein but not a 6kDa protein was observed. NADH cytochrome c reductase activity was decreased and superoxide production rates with NADH as substrate were increased. On the other hand, with protein kinase A-driven phosphorylation, NADH cytochrome c reductase was increased and superoxide production decreased. Overall there was a 4-fold variation in electron transport rates observable at the extremes of these phosphorylation events. This suggests that electron flow through complex I and the production of oxygen free radicals can be regulated by phosphorylation events. In light of these observations we discuss a potential model for the dual regulation of complex I and the production of oxygen free radicals by both PKA and PDH kinase.
authors.affiliation: The Hospital for Sick Children, Metabolism Research Programme, Toronto, ON, Canada.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Raha
authors.forename: A Tomoko
authors.initials: AT
authors.lastname: Myint
authors.forename: Leslie
authors.initials: L
authors.lastname: Johnstone
authors.forename: Brian H
authors.initials: BH
authors.lastname: Robinson
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D042967:Electron Transport Complex I; D004789:Enzyme Activation; D049454:Firefly Luciferin / Q000378:metabolism; D006801:Humans; D007093:Imidazoles; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010101:Oxygen Consumption; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases; D011719:Pyrazines / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D007093:Imidazoles; D008565:Membrane Proteins; C492251:Ndufa1 protein, mammalian; D047428:Protein Kinase Inhibitors; D011719:Pyrazines; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017382:Reactive Oxygen Species; D009243:NAD; D013481:Superoxides; C017144:coelenterazine; D049454:Firefly Luciferin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D009247:NADH, NADPH Oxidoreductases; D009245:NADH Dehydrogenase; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D042967:Electron Transport Complex I; C118736:NDUFA1 protein, human; C427643:NDUFS4 protein, human