5 ISOENZYMES OF PROTEIN-KINASE-C ARE EXPRESSED IN NORMAL AND STZ-DIABETIC RAT HEPATOCYTES - EFFECT OF PHORBOL 12-MYRISTATE 13-ACETATE

Using isoenzyme-specific antisera, five Protein Kinase Cs (PKCs) were detected in cytosol and membrane hepatocytes from normal rats: PKC alp ha (80 kDa), PKC beta II (40, 50, 55, 85 kDa), PKC delta (74, 76 kDa), PKC epsilon (95 kDa), PKC zeta (65, 70 kDa). STZ-diabetes induced a l ower expression of the five PKCs, a higher localization in the cytosol , a preferential expression of PKC delta as the 76 kDa phosphorylated species and a decreased kinase activity towards Histone III-S. A 1 mu M phorbol 12-myristate 13-acetate (PMA) incubation induced similar tra nslocation to the membrane of PKCs alpha, native 85 kDa beta II and ep silon. The 74 kDa PKC delta was switched to the 76 kDa species, the no rmal form in STZ-diabetic cells. The truncated PKC beta II and PKC eps ilon were unchanged.