Evidence for functional role of epsilonPKC isozyme in the regulation of cardiac Ca(2+) channels.
Limited information is available regarding the effects of protein kinase C (PKC) isozyme(s) in the regulation of L-type Ca(2+) channels due to lack of isozyme-selective modulators. To dissect the role of individual PKC isozymes in the regulation of cardiac Ca(2+) channels, we used the recently developed novel peptide activator of the epsilonPKC, epsilonV1-7, to assess the role of epsilonPKC in the modulation of L-type Ca(2+) current (I(Ca,L)). Whole cell I(Ca,L) was recorded using patch-clamp technique from rat ventricular myocytes. Intracellular application of epsilonV1-7 (0.1 microM) resulted in a significant inhibition of I(Ca,L) by 27.9 +/- 2.2% (P < 0.01, n = 8) in a voltage-independent manner. The inhibitory effect of epsilonV1-7 on I(Ca,L) was completely prevented by the peptide inhibitor of epsilonPKC, epsilonV1-2 [5.2 +/- 1.7%, not significant (NS), n = 5] but not by the peptide inhibitors of cPKC, alphaC2-4 (31.3 +/- 2.9%, P < 0.01, n = 6) or betaC2-2 plus betaC2-4 (26.1 +/- 2.9%, P < 0.01, n = 5). In addition, the use of a general inhibitor (GF-109203X, 10 microM) of the catalytic activity of PKC also prevented the inhibitory effect of epsilonV1-7 on I(Ca,L) (7.5 +/- 2.1%, NS, n = 6). In conclusion, we show that selective activation of epsilonPKC inhibits the L-type Ca channel in the heart.
Hu
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Molecular and Cellular Cardiology Program, Veterans Affairs New York Harbor Healthcare System, Brooklyn, New York 11209, USA.
Mochly-Rosen
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Boutjdir
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D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D015737:Nisoldipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D051381:Rats; D017208:Rats, Wistar
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D010455:Peptides; D015737:Nisoldipine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C497257:Prkce protein, rat; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; C070515:bisindolylmaleimide I