title: L-type calcium channel β subunit modulates angiotensin II responses in cardiomyocytes.
abstract: Angiotensin II regulation of L-type calcium currents in cardiac muscle is controversial and the underlying signaling events are not completely understood. Moreover, the possible role of auxiliary subunit composition of the channels in Angiotensin II modulation of L-type calcium channels has not yet been explored. In this work we study the role of Ca(v)β subunits and the intracellular signaling responsible for L-type calcium current modulation by Angiotensin II. In cardiomyocytes, Angiotensin II exposure induces rapid inhibition of L-type current with a magnitude that is correlated with the rate of current inactivation. Semi-quantitative PCR of cardiomyocytes at different days of culture reveals changes in the Ca(v)β subunits expression pattern that are correlated with the rate of current inactivation and with Angiotensin II effect. Over-expression of individual b subunits in heterologous systems reveals that the magnitude of Angiotensin II inhibition is dependent on the Ca(v)β subunit isoform, with Ca(v)β(1b) containing channels being more strongly regulated. Ca(v)β(2a) containing channels were insensitive to modulation and this effect was partially due to the N-terminal palmitoylation sites of this subunit. Moreover, PLC or diacylglycerol lipase inhibition prevents the Angiotensin II effect on L-type calcium channels, while PKC inhibition with chelerythrine does not, suggesting a role of arachidonic acid in this process. Finally, we show that in intact cardiomyocytes the magnitude of calcium transients on spontaneous beating cells is modulated by Angiotensin II in a Ca(v)β subunit-dependent manner. These data demonstrate that Ca(v)β subunits alter the magnitude of inhibition of L-type current by Angiotensin II.
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.
authors.forename: Tamara
authors.initials: T
authors.lastname: Hermosilla
authors.forename: Cristian
authors.initials: C
authors.lastname: Moreno
authors.forename: Mircea
authors.initials: M
authors.lastname: Itfinca
authors.forename: Christophe
authors.initials: C
authors.lastname: Altier
authors.forename: Ricardo
authors.initials: R
authors.lastname: Armisén
authors.forename: Andres
authors.initials: A
authors.lastname: Stutzin
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
authors.forename: Diego
authors.initials: D
authors.lastname: Varela
mesh_terms: D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016718:Arachidonic Acid / Q000378:metabolism; D053119:Benzophenanthridines / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D008071:Lipoprotein Lipase / Q000494:pharmacology; D054878:Lipoylation / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D054801:Phosphoinositide Phospholipase C / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D053119:Benzophenanthridines; D020746:Calcium Channels, L-Type; D009124:Muscle Proteins; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D016718:Arachidonic Acid; C016299:chelerythrine; D011493:Protein Kinase C; D008071:Lipoprotein Lipase; D054801:Phosphoinositide Phospholipase C