Modulation of Cardiac Ca2+ Channel by Gq-activating Neurotransmitters Reconstituted in Xenopus Oocytes

Sharon Weiss, Thanh Doan, Kenneth E. Bernstein, Nathan Dascal

Research output: Contribution to journalArticlepeer-review

Abstract

L-type dihydropyridine-sensitive voltage dependent Ca2+ channels (L-VDCCs; α1C) are crucial in cardiovascular physiology. Currents via L-VDCCs are enhanced by hormones and transmitters operating via Gq, such as angiotensin II (AngII) and acetylcholine (ACh). It has been proposed that these modulations are mediated by protein kinase C (PKC). However, reports on effects of PKC activators on L-type channels are contradictory; inhibitory and/or enhancing effects have been observed. Attempts to reproduce the enhancing effect of AngII in heterologous expression systems failed. We previously found that PKC modulation of the channel depends on α1C isoform used; only a long N-terminal (NT) isoform was up-regulated. Here we report the reconstitution of the AngII- and ACh-induced enhancement of the long-NT isoform of L-VDCC expressed in Xenopus oocytes. The current initially increased over several minutes but later declined to below baseline levels. Using different NT deletion mutants and human short- and long-NT isoforms of the channel, we found the initial segment of the NT to be crucial for the enhancing, but not for the inhibitory, effect. Using blockers of PKC and of phospholipase C (PLC) and a mutated AngII receptor lacking Gq coupling, we demonstrate that the signaling pathway of the enhancing effect includes the activation of Gq, PLC, and PKC. The inhibitory modulation, present in both α1C isoforms, was Gq- and PLC-independent and Ca2+-dependent, but not Ca2+-mediated, as only basal levels of Ca2+ were essential. Reconstitution of AngII and ACh effects in Xenopus oocytes will advance the study of molecular mechanisms of these physiologically important modulations.

Original languageEnglish
Pages (from-to)12503-12510
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number13
DOIs
StatePublished - 26 Mar 2004

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