title: A new phosphorylation site in cardiac L-type Ca2+ channels (Cav1.2) responsible for its cAMP-mediated modulation.
abstract: Cardiac L-type Ca(2+) channels are modulated by phosphorylation by protein kinase A (PKA). To explore the PKA-targeted phosphorylation site(s), five potential phosphorylation sites in the carboxyl (COOH) terminal region of the α1C-subunit of the guinea pig Cav1.2 Ca(2+) channel were mutated by replacing serine (S) or threonine (T) residues with alanine (A): S1574A (C1 site), S1626A (C2), S1699A (C3), T1908A, (C4), S1927A (C5), and their various combinations. The wild-type Ca(2+) channel activity was enhanced three- to fourfold by the adenylyl cyclase activator forskolin (Fsk, 5 μM), and that of mutants at C3, C4, C5, and combination of these sites was also significantly increased by Fsk. However, Fsk did not modulate the activity of the C1 and C2 mutants and mutants of combined sites involving the C1 site. Three peptides of the COOH-terminal tail of α1C, termed CT1 [corresponding to amino acids (aa) 1509-1789, containing sites C1-3], CT2 (aa 1778-2003, containing sites C4 and C5), and CT3 (aa 1942-2169), were constructed, and their phosphorylation by PKA was examined. CT1 and CT2, but not CT3, were phosphorylated in vitro by PKA. Three CT1 mutants at two sites of C1-C3 were also phosphorylated by PKA, but the mutant at all three sites was not. The CT2 mutant at the C4 site was phosphorylated by PKA, but the mutant at C5 sites was not. These results suggest that Ser(1574) (C1 site) may be a potential site for the channel modulation mediated by PKA.
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan;
authors.forename: Etsuko
authors.initials: E
authors.lastname: Minobe
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan; Department of Cellular Physiology and Signal Transduction, Sapporo Medical University School of Medicine, Sapporo, Japan; and.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Maeda
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan;
authors.forename: Jianjun
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan; Department of Pharmaceutical Toxicology, School of Pharmaceutical Sciences, China Medical University, Shenyang, China.
authors.forename: Liying
authors.initials: L
authors.lastname: Hao
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan;
authors.forename: Asako
authors.initials: A
authors.lastname: Kameyama
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Kagoshima, Japan; kame@m.kufm.kagoshima-u.ac.jp.
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
mesh_terms: D026962:Amino Acid Transport System ASC / Q000235:genetics / Q000378:metabolism; D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D007413:Intestinal Mucosa / Q000166:cytology; D017998:Leukotriene D4 / Q000494:pharmacology; D049488:Phosphatidylethanolamine Binding Protein / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors; D051381:Rats
chemical_list: D026962:Amino Acid Transport System ASC; D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); C550693:PEBP1 protein, rat; D049488:Phosphatidylethanolamine Binding Protein; C420504:Slc1a4 protein, rat; D017998:Leukotriene D4; D000242:Cyclic AMP; D019908:Proto-Oncogene Proteins c-raf
keywords: adenosine 3′,5′-cyclic monophosphate; calcium channels; protein kinase A