Abstract
We have previously identified a phorbol ester-induced PKCε (protein kinase Cε) interaction with the (∼18 kDa) COIV [CO (cytochrome c oxidase) subunit IV] in NCMs (neonatal cardiac myocytes). Since PKCε has been implicated as a key mediator of cardiac PC (preconditioning), we examined whether hypoxic PC could induce PKCε-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 PKCε-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 PKCε-selective antisera, we observed an 11.1-fold increase in PKCε-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 PKCε-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 PKCε-COIV interaction and an enhancement of CO activity occur in NCM hypoxic PC. We therefore propose novel mechanisms of PKCε-mediated PC involving enhanced energetics, decreased mitochondrial reactive oxygen species production and the preservation of COIV levels.
Original language | English (US) |
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Pages (from-to) | 191-199 |
Number of pages | 9 |
Journal | Biochemical Journal |
Volume | 393 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1 2006 |
Keywords
- Cardiac hypoxia
- Cytochrome c oxidase subunit IV (COIV)
- Electron-transport chain
- Mitochondria
- Preconditioning (PC)
- Protein kinase Cε (PKCε)
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology