Induction and subcellular localization of protein kinase C isozymes following renal ischemia

Background. We have previously reported that the expression of the receptor for activated C kinase (RACK1) is induced post-ischemia/preperfusion injury to the kidney, and activation of protein kinase C (PKC) protects renal cells from hypoxic injury. This study was done to determine whether the induced expression of RACK1 is accompanied by changes in the level of expression and subcellular distribution of PKC isozymes. Methods. Ischemia/reperfusion injury resulting in acute renal failure was induced by 60 minutes of bilateral renal artery clamping in rats. The expression levels and translocation of various PKC isozymes between soluble and particulate fractions in whole kidney homogenates were demonstrated by immunoblot analysis. The expression pattern of the various PKC isozymes in the kidney postinjury was performed by immunohistochemistry. Results. PKC α, βII, and ζ were induced and translocated from the soluble fraction to the particulate fraction post-injury. Immunolocalization showed PKC α, βII, and ζ expression to be induced in the proximal tubule epithelial cell (PTEC) at 0 to 30 minutes post-ischemia/reperfusion injury (IRI). At one-day postinjury, the α isozyme was translocated to the plasma membrane of the undamaged PTEC, while it was translocated to the nucleus in damaged PTEC. PKC βII expression was along the basal and lateral side of the undamaged PTEC, while it was distributed in the cytoplasm of sloughed cells in the damaged PTEC. PKC ζ expression at one day was along the apical side of the damaged PTEC. At seven-days postinjury, the expressions of the α and ζ isozymes were localized to the plasma membrane of the regenerating PTEC and the expression of PKC βII isozyme to certain interstitial cells. Conclusion. The induced expression, translocation, and the intracellular spatial distributions of the enzymes suggest that they may mediate multiple processes during IRI.