title: Modulation of distinct isoforms of L-type calcium channels by G(q)-coupled receptors in Xenopus oocytes: antagonistic effects of Gβγ 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 α(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 α(1C) isoform by Gβγ. Gβγ inhibited whereas a Gβγ scavenger protein augmented the G(q)--but not phorbol ester-mediated enhancement of channel activity, suggesting that Gβγ acts upstream from PKC. In vitro binding experiments reveal binding of both Gβγ and PKC to α(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 α(1C) sensitive to PKC stimulation and to Gβγ scavenging. Our results suggest a complex antagonistic interplay between G(q)-activated PKC and Gβγ in regulation of L-VDCC, in which multiple cytosolic segments of α(1C) are involved.
authors.affiliation: Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. lahavsha@post.tau.ac.il
authors.forename: Sharon
authors.initials: S
authors.lastname: Weiss
authors.forename: Tal
authors.initials: T
authors.lastname: Keren-Raifman
authors.forename: Shimrit
authors.initials: S
authors.lastname: Oz
authors.forename: Adva
authors.initials: A
authors.lastname: Ben Mocha
authors.forename: Hannelore
authors.initials: H
authors.lastname: Haase
authors.forename: Nathan
authors.initials: N
authors.lastname: Dascal
mesh_terms: D000818:Animals; D001665:Binding Sites; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000378:metabolism*; D018118:Chloride Channels / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005091:Exons / Q000235:genetics; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D020746:Calcium Channels, L-Type; D018118:Chloride Channels; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D020033:Protein Isoforms; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D011976:Receptors, Muscarinic; D011493:Protein Kinase C; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D013755:Tetradecanoylphorbol Acetate