Regulation of protein kinase C-epsilon and its age-dependence

Protein kinase C (PKC) is an important mediator in the cardioprotection of ischemic preconditioning and has been shown to translocate to mitochondria upon activation. However, little is known about the cellular signaling underlying the translocation of PKC isoforms to mitochondria and its age-dependence. The present study aimed to explore whether adenosine-induced translocation of PKC epsilon to mitochondria is mediated by caveolin-3 and/or adenosine A2B receptor/PI3 kinase mediated signaling, and whether the mitochondria(targeting of PKCe is age-related. Immunofluorescence imaging of isolated mitochondria from cardiomyocytes and H9c2 cells showed that while adenosine-induced increase in mitochondrial PKC epsilon was inhibited by adenosine A1 receptor blocker, pretreatment with adenosine A2B receptor specific inhibitor MRS 1754 or PI3K inhibitor Wortmannin did not significantly reduce adenosine-mediated increase in mitochondrial PKC epsilon. Interestingly, adenosine-induced increase in mitochondria( translocation of PKCs was significantly blocked by suppressing caveolin-3 expression with specific siRNA. When compared to that in young adult rat hearts, the level of mitochondrial PKCs in middle-aged rat hearts was significantly lower at the basal condition and in response to adenosine treatment, along with largely decreased mitochondrial HSP90 and TOM70 protein expression. We demonstrate that adenosine induced translocation of PKCe to mitochondria is mediated by a caveolin-3-dependent mechanism and this process is age-related, possibly in part, through regulation of HSP90 and TOM70 expression. These results point out a novel mechanism in regulating PKC function in mitochondria. (C) 2016 Elsevier Inc. All rights reserved.