Translocation of protein kinase C isoforms to subcellular targets in ischemic and anesthetic preconditioning

Abstract

Background: Translocation of protein kinase C (PKC) to subcellular targets is a pivotal signaling step in ischemic preconditioning (IPC). However, to date, it is unknown whether PKC isoforms translocate in anesthetic preconditioning (ARC). Methods: The PKC blockers chelerythrine and rottlerin and the adenosine triphosphate-dependent potassium (KATP) channel blockers HMR-1098 and 5-hydroxydecanoate were used to assess the role of PKC and KATP channels in isolated perfused rat hearts subjected to IPC or APC (1.5 minimum alveolar concentration isoflurane) followed by 40 min of ischemia and 30 min of reperfusion. Immunohistochemical techniques were used to visualize PKC translocation after preconditioning. In addition, the phosphorylation status of PKC isoforms was assessed. Results: Chelerythrine, rottlerin, and 5-hydroxydecanoate blocked IPC and APC with respect to functional recovery, albeit IPC at higher concentrations. HMR-1098 did not affect IPC or APC. PKCδ and PKCε translocated to nuclei in both IPC and APC, which was inhibited by chelerythrine and rottlerin. PKCδ translocated to mitochondria but not to the sarcolemma, and PKCε translocated to the sarcolemma and intercalated disks but not to mitochondria. Interestingly, PKCε was accumulated at the intercalated disks in control and preconditioned hearts. Phosphorylation of PKCδ on serine643 was increased in IPC and APC and blocked by chelerythrine and rottlerin, whereas phosphorylation of PKCδ on threonine505 was increased only in IPC and not blocked by chelerythrine or rottlerin. PKCε on serine729 did not change its phosphorylation status. Conclusions: This study indicates that translocation of PKCδ plays a pivotal role in IPC and APC and suggests that phosphorylation of PKCδ on serine643 may be of particular relevance in transferring the APC stimulus to mitochondrial KATP channels.