Protein kinase Cε targets respiratory chain and mitochondrial membrane potential but not F0F1-ATPase in renal cells injured by oxidant: NOWAK and BAKAJSOVA-TAKACSOVA

: We have previously shown that protein kinase Ce (PKCe) is involved in mitochondrial dysfunction in renal proximal tubular cells (RPTC). This study examined mitochondrial targets of active PKCe in RPTC injured by the model oxidant tert-butyl hydroperoxide (TBHP). TBHP exposure augmented the levels of phosphorylated (active) PKCe in mitochondria, which suggested translocation of PKCe to mitochondria after oxidant exposure. Oxidant injury decreased state 3 respiration, adenosine triphosphate (ATP) production, ATP content, and complex I activity. Further, TBHP exposure increased ΔΨm and production of reactive oxygen species (ROS), and induced mitochondrial fragmentation and RPTC death. PKCe activation by overexpressing constitutively active PKCe exacerbated decreases in state 3 respiration, complex I activity, ATP content, and augmented RPTC death. In contrast, inhibition of PKCe by overexpressing dnPKCe mutant restored state 3 respiration, respiratory control ratio, complex I activity, ΔΨm , and ATP production and content, but did not prevent decreases in F0 F1 -ATPase activity. Inhibition of PKCe prevented oxidant-induced production of ROS and mitochondrial fragmentation, and reduced RPTC death. We conclude that activation of PKCe mediates: (a) oxidant-induced changes in ΔΨm , decreases in mitochondrial respiration, complex I activity, and ATP content; (b) mitochondrial fragmentation; and (c) RPTC death. In contrast, oxidant-induced inhibition of F0 F1 -ATPase activity is not mediated by PKCe. These results show that, in contrast to the protective effects of PKCe in the heart, PKCe activation is detrimental to mitochondrial function and viability in RPTC and mediates oxidant-induced injury.