Evidence for functional role of epsilonPKC isozyme in the regulation of cardiac Na(+) channels.
Investigation of the role of individual protein kinase C (PKC) isozymes in the regulation of Na(+) channels has been largely limited by the lack of isozyme-selective modulators. Here we used a novel peptide-specific activator (epsilonV1-7) of epsilonPKC and other peptide isozyme-specific inhibitors in addition to the general PKC activator phorbol 12-myristate 13-acetate (PMA) to dissect the role of individual PKCs in the regulation of the human cardiac Na(+) channel hH1, heterologously expressed in Xenopus oocytes. Peptides were injected individually or in combination into the oocyte. Whole cell Na(+) current (I(Na)) was recorded using two-electrode voltage clamp. epsilonV1-7 (100 nM) and PMA (100 nM) inhibited I(Na) by 31 +/- 5% and 44 +/- 8% (at -20 mV), respectively. These effects were not seen with the scrambled peptide for epsilonV1-7 (100 nM) or the PMA analog 4alpha-phorbol 12,13-didecanoate (100 nM). However, epsilonV1-7- and PMA-induced I(Na) inhibition was abolished by epsilonV1-2, a peptide-specific antagonist of epsilonPKC. Furthermore, PMA-induced I(Na) inhibition was not altered by 100 nM peptide-specific inhibitors for alpha-, beta-, delta-, or etaPKC. PMA and epsilonV1-7 induced translocation of epsilonPKC from soluble to particulate fraction in Xenopus oocytes. This translocation was antagonized by epsilonV1-2. In native rat ventricular myocytes, PMA and epsilonV1-7 also inhibited I(Na); this inhibition was antagonized by epsilonV1-2. In conclusion, the results provide evidence for selective regulation of cardiac Na(+) channels by epsilonPKC isozyme.
Xiao
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GQ
Molecular and Cellular Cardiology Program, Veterans Affairs New York Harbor Healthcare System, State University of New York Health Science Center, Brooklyn, New York 11209, USA.
Qu
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Sun
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ZQ
Mochly-Rosen
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Boutjdir
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D000818:Animals; D002469:Cell Separation; D003001:Cloning, Molecular; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000502:physiology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D018075:RNA, Complementary / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D062687:Sodium Channel Agonists; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014981:Xenopus
D007527:Isoenzymes; D010455:Peptides; D018075:RNA, Complementary; D062687:Sodium Channel Agonists; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate