Immunolocalization of protein kinase C isoenzymes alpha, beta I, beta II, delta, and epsilon in mouse kidney.

Localization of protein kinase C (PKC) isoenzymes alpha, beta I, beta II, delta, and epsilon was studied employing Western blot analysis and immunohistochemical methods including confocal laser-scanning microscopy in the kidney of two mice strains, namely, C57BL/6 and 129/Sv, which have recently been used as genetic backgrounds for respective knockout mice. Immunoblot analysis identified immunoreactive bands for each isoenzyme in total kidney cell extracts. Isoenzyme expression sites were identical for both strains. Glomeruli expressed PKC-alpha, -beta I, and -epsilon. The latter isoenzyme was also detected in apical aspects of proximal convoluted but not in proximal straight tubules. In contrast to rats, neither PKC-alpha nor PKC-beta I was detectable in the proximal tubule. Immunofluorescence was observed in luminal membranes of medullary (MTAL) and cortical thick ascending limbs for PKC-beta I and in MTAL for PKC-epsilon. The cortical collecting duct expressed PKC-alpha, -beta I, and -delta in intercalated cells only. In the outer medullary collecting duct, PKC-alpha and -beta I were detectable in principal cells, whereas PKC-delta was found in intercalated cells. In the inner medullary collecting duct, PKC-alpha, -beta I, and -beta II were detected. As described for the rat, the expression of PKC-beta II was otherwise restricted to cortical and medullary interstitial cells. The specificity of all labeling was confirmed in respective PKC isoenzyme knockout mice. In summary, distinct expression patterns were shown for PKC isoenzymes alpha, beta I, beta II, delta, and epsilon in the mouse kidney.