Delta Protein Kinase C Interacts with the d Subunit of the F1F0 ATPase in Neonatal Cardiac Myocytes Exposed to Hypoxia or Phorbol Ester IMPLICATIONS FOR F1F0 ATPase REGULATION

Mitochondrial protein kinase C isozymes have been reported to mediate both cardiac ischemic preconditioning and ischemia/reperfusion injury. In addition, cardiac preconditioning improves the recovery of ATP levels after ischemia/reperfusion injury. We have, therefore, evaluated protein kinase C modulation of the F1F0 ATPase in neonatal cardiac myocytes. Exposure of cells to 3 or 100 nM 4 beta-phorbol 12-myristate-13-acetate induced co-immunoprecipitation of delta protein kinase C (but not alpha,epsilon,or zeta protein kinase C) with the d subunit of the F1F0 ATPase. This co-immunoprecipitation correlated with 40 +/- 3% and 72 +/- 9% inhibitions of oligomycin-sensitive F1F0 ATPase activity, respectively. We observed prominent expression of delta protein kinase C in cardiac myocyte mitochondria, which was enhanced following a 4-h hypoxia exposure. In contrast, hypoxia decreased mitochondrial zeta PKC levels by 85 +/- 1%. Following 4 h of hypoxia, F1F0 ATPase activity was inhibited by 75 +/- 9% and delta protein kinase C co-immunoprecipitated with the d subunit of F1F0 ATPase. In vitro incubation of protein kinase C with F1F0 ATPase enhanced F1F0 activity in the absence of protein kinase C activators and inhibited it in the presence of activators. Recombinant delta protein kinase C also inhibited F1F0 ATPase activity. Protein kinase C overlay assays revealed delta protein kinase C binding to the d subunit of F1F0 ATPase, which was modulated by diacylglycerol, phosphatidylserine, and cardiolipin. Our results suggest a novel regulation of the F1F0 ATPase by the delta protein kinase C isozyme.