Differential regulation of protein kinase C isoforms in isolated neonatal and adult rat cardiomyocytes.
We have immunologically identified the isoforms of protein kinase C (PKC) present in neonatal and adult rat cardiomyocytes and examined their regulation by hormones and phorbol ester. Both cell types express the Ca(2+)-dependent alpha-PKC and the Ca(2+)-independent epsilon- and delta-PKC isoforms. The atypical zeta-PKC isoform is also expressed in neonatal, but only weakly in adult cells. Stimulation of the alpha 1-adrenergic or purinergic receptor with phenylephrine or ATP, respectively, increases membrane-associated immunoreactivity of both epsilon- and delta-PKC in neonatal and adult cells; endothelin and carbachol are also effective in adult cells. In contrast, none of the agonists leads to increases in membrane-associated alpha-PKC in cardiomyocytes. PKC zeta is also unaffected by receptor stimulation. The phorbol ester phorbol 12-myristate 13-acetate causes redistribution and subsequently down-regulation of alpha-, epsilon-, and delta- but not zeta-PKC. The three isoforms are down-regulated at distinctively different rates, with alpha-PKC being the most rapid and epsilon-PKC the slowest. We used selective down-regulation of alpha-, epsilon-, and delta-PKC to investigate the role of these isoforms in PKC phosphorylation-dependent events in neonatal myocytes. Our findings suggest that epsilon-PKC is responsible for the phenylephrine-induced phosphorylation of MARCKS, an endogenous PKC-specific substrate. In contrast, agonist-induced c-fos expression is unlikely to be mediated by epsilon-PKC since the response is rapidly down-regulated and apparently Ca(2+)-dependent. Our finding that the PKC isoforms are differentially responsive to neurohormones suggests that they play distinct and specific roles in cardiac function.
Pucéat
M
M
Department of Pharmacology, University of California at San Diego, La Jolla 92093-0636.
Hilal-Dandan
R
R
Strulovici
B
B
Brunton
L L
LL
Brown
J H
JH
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D016762:Genes, fos / Q000187:drug effects; D006321:Heart / Q000254:growth & development; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007527:Isoenzymes; D010750:Phosphoproteins; D016760:Proto-Oncogene Proteins c-fos; D004533:Egtazic Acid; D002217:Carbachol; D011433:Propranolol; D011493:Protein Kinase C; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D013755:Tetradecanoylphorbol Acetate