Protein kinase Cepsilon interacts with cytochrome c oxidase subunit IV and enhances cytochrome c oxidase activity in neonatal cardiac myocyte preconditioning.
We have previously identified a phorbol ester-induced PKCepsilon (protein kinase Cepsilon) interaction with the ( approximately 18 kDa) COIV [CO (cytochrome c oxidase) subunit IV] in NCMs (neonatal cardiac myocytes). Since PKCepsilon has been implicated as a key mediator of cardiac PC (preconditioning), we examined whether hypoxic PC could induce PKCepsilon-COIV interactions. Similar to our recent study with phorbol esters [Ogbi, Chew, Pohl, Stuchlik, Ogbi and Johnson (2004) Biochem. J. 382, 923-932], we observed a time-dependent increase in the in vitro phosphorylation of an approx. 18 kDa protein in particulate cell fractions isolated from NCMs subjected to 1-60 min of hypoxia. Introduction of a PKCepsilon-selective translocation inhibitor into cells attenuated this in vitro phosphorylation. Furthermore, when mitochondria isolated from NCMs exposed to 30 min of hypoxia were subjected to immunoprecipitation analyses using PKCepsilon-selective antisera, we observed an 11.1-fold increase in PKCepsilon-COIV co-precipitation. In addition, we observed up to 4-fold increases in CO activity after brief NCM hypoxia exposures that were also attenuated by introducing a PKCepsilon-selective translocation inhibitor into the cells. Finally, in Western-blot analyses, we observed a >2-fold PC-induced protection of COIV levels after 9 h index hypoxia. Our studies suggest that a PKCepsilon-COIV interaction and an enhancement of CO activity occur in NCM hypoxic PC. We therefore propose novel mechanisms of PKCepsilon-mediated PC involving enhanced energetics, decreased mitochondrial reactive oxygen species production and the preservation of COIV levels.
Ogbi
Mourad
M
Department of Pharmacology and Toxicology, School of Medicine and the Program in Regenerative Medicine, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912-2300, USA.
Johnson
John A
JA
D000818:Animals; D000831:Animals, Newborn; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D000860:Hypoxia; D019157:Ischemic Preconditioning, Myocardial; D008929:Mitochondria, Heart / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000201:enzymology*; D011485:Protein Binding; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species
D017382:Reactive Oxygen Species; D003576:Electron Transport Complex IV; D051744:Protein Kinase C-epsilon