Abstract 1482: Combined Proteomic and Metabolomic Analysis of Protein Kinase C Epsilon Transgenic Hearts
Background. Activation of protein kinase C (PKC) epsilon and inhibition of PKC delta are known to be cardioprotective against ischemia/reperfusion injury, but the mechanistic link between the two PKC isoforms remains unknown. Using a combined proteomic and metabolomic approach, we demonstrated previously that loss of PKC delta alters glucose metabolism in murine hearts. In the present study, we evaluated the effect of activated PKC epsilon on cardiac metabolism.
Methods and Results. Mitochondrial and cytosolic proteins from control and transgenic hearts with constitutive active or dominant negative PKC epsilon were analyzed using difference in-gel electrophoresis. Among the differentially expressed proteins identified by tandem mass spectrometry were mitofilin, an inner mitochondrial membrane protein and key regulator of metabolic flux. Moreover, transgenic activation of PKC epsilon resulted in differential expression of creatine kinase, pyruvate kinase, lactate dehydrogenase as well as aspartate amino transferase and cytosolic malate dehydrogenase, the two enzymatic components of the malate aspartate shuttle required for the import of reducing equivalents from glycolysis across the inner mitochondrial membrane. These enzymatic changes appeared to be dependent on PKC epsilon activity, as they were not observed in mice expressing inactive PKC epsilon. High-resolution nuclear magnetic resonance spectroscopy confirmed a pronounced effect of PKC epsilon activation on cardiac metabolism: normoxic hearts with constitutive active PKC epsilon had significantly lower concentrations of glucose, lactate, glutamine and creatine, but higher levels of choline, glutamate and total adenosine nucleotides. While metabolite concentrations were almost identical in transgenic and control hearts during ischemia, glucose and energy metabolites recovered faster upon reperfusion in transgenic hearts with constitutive active PKC epsilon.
Conclusions. Our findings provide the first evidence that PKC epsilon activity modulates cardiac glucose metabolism and suggest a synergistic metabolic effect of PKC delta inhibition and PKC epsilon activation in cardioprotection.