title: Adenylyl cyclase/cAMP-PKA-mediated phosphorylation of basal L-type Ca(2+) channels in mouse embryonic ventricular myocytes.
abstract: In fetal mammalian heart, constitutive adenylyl cyclase/cyclic AMP-dependent protein kinase A (cAMP-PKA)-mediated phosphorylation, independent of β-adrenergic receptor stimulation, could under such circumstances play an important role in sustaining the L-type calcium channel current (I(Ca,L)) and regulating other PKA dependent phosphorylation targets. In this study, we investigated the regulation of L-type Ca(2+) channel (LTCC) in murine embryonic ventricles. The data indicated a higher phosphorylation state of LTCC at early developmental stage (EDS, E9.5-E11.5) than late developmental stage (LDS, E16.5-E18.5). An intrinsic adenylyl cyclase (AC) activity, PKA activity and basal cAMP concentration were obviously higher at EDS than LDS. The cAMP increase in the presence of isobutylmethylxanthine (IBMX, nonselective phosphodiesterase inhibitor) was further augmented at LDS but not at EDS by chelation of intracellular Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)-acetoxymethyl ester (BAPTA-AM). Furthermore, I(Ca,L) increased with time after patch rupture in LDS cardiomyocytes dialyzed with pipette solution containing BAPTA whereas not at EDS. Thus we conclude that the high basal level of LTCC phosphorylation is due to the high intrinsic PKA activity and the high intrinsic AC activity at EDS. The latter is possibly owing to the little or no effect of Ca(2+) influx via LTCCs on AC activity, leading to the inability to inhibit AC.
authors.affiliation: Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Xisheng
authors.initials: X
authors.lastname: Yan
authors.forename: Shijun
authors.initials: S
authors.lastname: Gao
authors.forename: Ming
authors.initials: M
authors.lastname: Tang
authors.forename: Jiaoya
authors.initials: J
authors.lastname: Xi
authors.forename: Linlin
authors.initials: L
authors.lastname: Gao
authors.forename: Minjie
authors.initials: M
authors.lastname: Zhu
authors.forename: Hongyan
authors.initials: H
authors.lastname: Luo
authors.forename: Xinwu
authors.initials: X
authors.lastname: Hu
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Zheng
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hescheler
authors.forename: Huamin
authors.initials: H
authors.lastname: Liang
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D022062:Electrophysiologic Techniques, Cardiac; D004622:Embryo, Mammalian; D047108:Embryonic Development; D006352:Heart Ventricles / Q000473:pathology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation
chemical_list: D020746:Calcium Channels, L-Type; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine