Diabetes induces selective alterations in the expression of protein kinase C isoforms in hepatocytes.
Membrane and cytosol fractions from hepatocytes of both normal and streptozotocin-induced diabetic animals were probed with a panel of polyclonal anti-peptide antisera in order to identify protein kinase C (PKC) isoforms. Immunoreactive species were noted with antisera specific for alpha (approximately 81 kDa), beta-II (approximately 82 kDA), epsilon (approximately 95 kDa) and epsilon (approximately 79 kDa). In addition, a species migrating with an apparent size of approximately 94 kDa was also detected in cytosol fractions using an antiserum specific for PKC-alpha. Each of these species was specifically displaced when the PKC-isoform specific peptide was included in the immunodetection system. No immunoreactive species consistent with the presence of the beta-I, gamma, delta and eta isoforms of protein kinase C was observed. Induction of diabetes using streptozotocin invoked selective alterations in the expression of PKC isoforms which were reversed upon insulin therapy. In the cytosol fraction, marked increases of approximately 3-fold occurred in levels of the beta-II isoform and the approximately 90 kDa (upper) form of PKC-alpha, with no apparent/little change in the levels of the approximately 81 kDa (lower) form of PKC-alpha and those of PKC-zeta. Diabetes induction also appeared to have elicited the translocation of PKC-beta-II and the approximately 81 kDa (lower) form of PKC-alpha to the membrane fraction where immunoreactivity for these species was now apparent. The level of PKC-epsilon, which was noted only in membrane fractions, was also increased upon induction of diabetes. It is suggested that the selective alterations in the expression of PKC isoforms occurring upon streptozotocin-induced diabetes may lead to altered cellular functioning and underly defects in inhibitory G-protein functioning and insulin action which characterise this animal model of diabetes.
Tang
E Y
EY
Department of Biochemistry, University of Glasgow, Scotland, UK.
Parker
P J
PJ
Beattie
J
J
Houslay
M D
MD
D000818:Animals; D000911:Antibodies, Monoclonal; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000201:enzymology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D015151:Immunoblotting; D007328:Insulin / Q000627:therapeutic use; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000911:Antibodies, Monoclonal; D007328:Insulin; D007527:Isoenzymes; D011493:Protein Kinase C; D019204:GTP-Binding Proteins