Immunocharacterization of protein kinase C isoenzymes in rat kidney glomeruli, and cultured glomerular epithelial and mesangial cells.

Protein kinase C (PKC) is a key enzyme in the signalling pathways that regulate glomerular functions. To understand the role of PKC in renal homeostasis, the expression and localization of PKC isoenzymes have been investigated. The isoforms of PKC present in rat kidney glomeruli, primary cultures and cell lines of glomerular epithelial and mesangial cells, were identified by immunoblot analysis with isotype-specific antibodies. Glomeruli were isolated from rat kidney cortex by differential sieving and found to express five PKC isoenzymes, PKC-alpha, -beta, -delta, -epsilon and -zeta. No PKC-gamma isoenzyme was detected. Outgrowth of cells from isolated glomeruli after 5 days in culture, considered to be mainly epithelial in nature, displayed strong immunoreactivity to PKC-alpha, -delta, -epsilon and zeta isoenzymes. No PKC-beta and -gamma isoforms were detectable. Outgrowth from isolated glomeruli after 21 days of culture, considered to be mainly mesangial cells, similarly expressed PKC-alpha, -delta, -epsilon and -zeta isotypes, but not PKC-beta and -gamma isoforms. The PKC isoenzyme content of a stable cell line of rat kidney glomerular parietal epithelial cells was also characterized. We have demonstrated previously that a cloned rat mesangial cell line expresses PKC-alpha, -delta, -epsilon and -zeta isoenzymes. Here we report that a cloned parietal epithelial cell line also expressed PKC-alpha, -delta, -epsilon and -zeta isoforms. No beta- and gamma-isoenzymes of PKC were detected. Subcellular distribution of PKC isotypes displayed clear differences, depending on the cell type and the isoenzyme examined. Phorbol 12-myristate 13-acetate stimulation of PKC caused down-regulation of PKC-alpha, -delta and -epsilon isoenzymes in epithelial and mesangial cells.(ABSTRACT TRUNCATED AT 250 WORDS)