Immunolocalization of protein kinase C isoenzymes alpha, beta I and beta II in rat kidney

Protein kinase C (PKC) significantly contributes to the control of renal fu nction, but little is known about the renal function or localization of PKC isoenzymes. Therefore, the localization of PKC isoenzymes alpha, beta I, a nd beta II was studied in rat kidney. Immunoblot analysis identified immuno reactive bands corresponding to PKC alpha, beta I, and beta II in total cel l extracts of both renal cortex and medulla. Immunohistochemistry using con focal laser scanning microscopy revealed immunostaining for PKC alpha withi n the glomerulus including podocytes and mesangial cells. PKC beta I was de tected in mesangial cells, whereas anti-PKC beta II labeled neither podocyt es nor mesangial cells. PKC beta II, however, was detected in cells within the mesangial area, which expressed MHC II, a marker for antigen-presenting cells. None of the three isoforms was detected in glomerular endothelial c ells. A prominent immunostaining with anti-PKC alpha and beta I was localiz ed to the brush border of S2 and S3 segments of proximal tubule, whereas S1 segments were not stained. Along the loop of Henle, both PKC alpha and PKC beta I were found in the luminal membrane of cortical and medullary thick ascending limb. In addition, anti-PKC beta I labeled the luminal membrane o f thin limbs. In the cortical collecting duct (CCD), immunofluorescence for PKC alpha was observed at the apical membrane of both peanut agglutinin (P NA)-negative cells and part of PNA-positive cells, whereas in the medullary collecting duct (MCD), PKC alpha was detected at the basolateral membrane. In comparison, PKC beta I was localized at the luminal membrane of PNA-pos itive cells only in CCD and at the luminal membrane of MCD. Unlike PKC alph a or beta I, there was (I) no detectable immunostaining with anti-PKC beta II in the proximal tubule, the loop of Henle, or the CCD and (2) a distinct staining for PKC beta II of interstitial cells in cortex and medulla (incl uding MHC II-positive dendritic cells). Furthermore, PKC beta II was detect ed in the luminal membrane of MCD. In summary, a distinct and differential expression pattern for PKC alpha, beta I, and beta II was shown in rat kidn ey, which may contribute to a better understanding of the specific role of these isoenzymes in the control of renal function.