Modulation of distinct isoforms of L-type calcium channels by G(q)-coupled receptors in Xenopus oocytes: antagonistic effects of G?? and protein kinase C.

ABSTRACT: L-type voltage dependent Ca(2+) channels (L-VDCCs; Ca(v)1.2) are crucial in cardiovascular physiology. In heart and smooth muscle, hormones and transmitters operating via G(q) enhance L-VDCC currents via essential protein kinase C (PKC) involvement. Heterologous reconstitution studies in Xenopus oocytes suggested that PKC and G(q)-coupled receptors increased L-VDCC currents only in cardiac long N-terminus (NT) isoforms of ?(1C), whereas known smooth muscle short-NT isoforms were inhibited by PKC and G(q) activators. We report a novel regulation of the long-NT ?(1C) isoform by G??. G?? inhibited whereas a G?? scavenger protein augmented the G(q)--but not phorbol ester-mediated enhancement of channel activity, suggesting that G?? acts upstream from PKC. In vitro binding experiments reveal binding of both G?? and PKC to ?(1C)-NT. However, PKC modulation was not altered by mutations of multiple potential phosphorylation sites in the NT, and was attenuated by a mutation of C-terminally located serine S1928. The insertion of exon 9a in intracellular loop 1 rendered the short-NT ?(1C) sensitive to PKC stimulation and to G?? scavenging. Our results suggest a complex antagonistic interplay between G(q)-activated PKC and G?? in regulation of L-VDCC, in which multiple cytosolic segments of ?(1C) are involved.

SUBMITTER: Weiss S 

PROVIDER: S-EPMC3536727 | biostudies-literature | 2012 Nov-Dec

REPOSITORIES: biostudies-literature