Abstract
We applied a combined proteomic and metabolomic approach to obtain novel mechanistic insights in PKCvarepsilon-mediated cardioprotection. Mitochondrial and cytosolic proteins from control and transgenic hearts with constitutively active or dominant negative PKCvarepsilon were analyzed using difference in-gel electrophoresis (DIGE). Among the differentially expressed proteins were creatine kinase, pyruvate kinase, lactate dehydrogenase, and the cytosolic isoforms of aspartate amino transferase and malate dehydrogenase, the two enzymatic components of the malate aspartate shuttle, which are required for the import of reducing equivalents from glycolysis across the inner mitochondrial membrane. These enzymatic changes appeared to be dependent on PKCvarepsilon activity, as they were not observed in mice expressing inactive PKCvarepsilon. High-resolution proton nuclear magnetic resonance ((1)H-NMR) spectroscopy confirmed a pronounced effect of PKCvarepsilon activity on cardiac glucose and energy metabolism: normoxic hearts with constitutively active PKCvarepsilon had significantly lower concentrations of glucose, lactate, glutamine and creatine, but higher levels of choline, glutamate and total adenosine nucleotides. Moreover, the depletion of cardiac energy metabolites was slower during ischemia/reperfusion injury and glucose metabolism recovered faster upon reperfusion in transgenic hearts with active PKCvarepsilon. Notably, inhibition of PKCvarepsilon resulted in compensatory phosphorylation and mitochondrial translocation of PKCdelta. Taken together, our findings are the first evidence that PKCvarepsilon activity modulates cardiac glucose metabolism and provide a possible explanation for the synergistic effect of PKCdelta and PKCvarepsilon in cardioprotection.