title: Facilitation and Ca2+-dependent inactivation are modified by mutation of the Ca(v)1.2 channel IQ motif.
abstract: The heart muscle responds to physiological needs with a short-term modulation of cardiac contractility. This process is determined mainly by properties of the cardiac L-type Ca(2+) channel (Ca(v)1.2), including facilitation and Ca(2+)-dependent inactivation (CDI). Both facilitation and CDI involve the interaction of calmodulin with the IQ motif of the Ca(v)1.2 channel, especially with Ile-1624. To verify this hypothesis, we created a mouse line in which Ile-1624 was mutated to Glu (Ca(v)1.2(I1624E) mice). Homozygous Ca(v)1.2(I1624E) mice were not viable. Therefore, we inactivated the floxed Ca(v)1.2 gene of heterozygous Ca(v)1.2(I1624E) mice by the α-myosin heavy chain-MerCreMer system. The resulting I/E mice were studied at day 10 after treatment with tamoxifen. Electrophysiological recordings in ventricular cardiomyocytes revealed a reduced Ca(v)1.2 current (I(Ca)) density in I/E mice. Steady-state inactivation and recovery from inactivation were modified in I/E versus control mice. In addition, voltage-dependent facilitation was almost abolished in I/E mice. The time course of I(Ca) inactivation in I/E mice was not influenced by the use of Ba(2+) as a charge carrier. Using 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid as a chelating agent for intracellular Ca(2+), inactivation of I(Ca) was slowed down in control but not I/E mice. The results show that the I/E mutation abolishes Ca(2+)/calmodulin-dependent regulation of Ca(v)1.2. The Ca(v)1.2(I1624E) mutation transforms the channel to a phenotype mimicking CDI.
authors.affiliation: Forschergruppe 923, Institut für Pharmakologie und Toxikologie, Technische Universität München, 80802 Munich, Germany.
authors.forename: Montatip
authors.initials: M
authors.lastname: Poomvanicha
authors.forename: Jörg W
authors.initials: JW
authors.lastname: Wegener
authors.forename: Anne
authors.initials: A
authors.lastname: Blaich
authors.forename: Stefanie
authors.initials: S
authors.lastname: Fischer
authors.forename: Katrin
authors.initials: K
authors.lastname: Domes
authors.forename: Sven
authors.initials: S
authors.lastname: Moosmang
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D018931:Antineoplastic Agents, Hormonal; C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; D013629:Tamoxifen; D002118:Calcium