Facilitation of murine cardiac L-type Ca(v)1.2 channel is modulated by calmodulin kinase II-dependent phosphorylation of S1512 and S1570.
Activity-dependent means of altering calcium (Ca(2)(+)) influx are assumed to be of great physiological consequence, although definitive tests of this assumption have only begun to emerge. Facilitation and inactivation offer two opposing, activity-dependent means of altering Ca(2+) influx via cardiac Ca(v)1.2 calcium channels. Voltage- and frequency-dependent facilitation of Ca(v)1.2 has been reported to depend on Calmodulin (CaM) and/or the activity of Calmodulin kinase II (CaMKII). Several sites within the cardiac L-type calcium channel complex have been proposed as the targets of CaMKII. Here, we generated mice with knockin mutations of alpha(1)1.2 S1512 and S1570 phosphorylation sites [sine facilitation (SF) mice]. Homocygote SF mice were viable and reproduced in a Mendelian ratio. Voltage-dependent facilitation in ventricular cardiomyocytes carrying the SF mutation was decreased from 1.58- to 1.18-fold. The CaMKII inhibitor KN-93 reduced facilitation to 1.28 in control cardiomyocytes. SF mutation negatively shifted the voltage-dependent inactivation and slowed recovery from inactivation, thereby making fewer channels available for activation. Telemetric ECG recordings at different heart rates showed that QT time decreased significantly more in SF than in control mice at higher rates. Our results strongly support the notion that CaMKII-dependent phosphorylation of Cav1.2 at S1512 and S1570 mediates Ca(2+) current facilitation in the murine heart.
Blaich
Anne
A
Forschergruppe 923, Munich Center for Integrated Protein Science, and Institut für Pharmakologie und Toxikologie, Technische Universität München, 80802 Munich, Germany.
Welling
Andrea
A
Fischer
Stefanie
S
Wegener
Jörg Werner
JW
Köstner
Katharina
K
Hofmann
Franz
F
Moosmang
Sven
S
D019943:Amino Acid Substitution; D000818:Animals; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D015640:Ion Channel Gating; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D021122:Protein Subunits
C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; D050505:Mutant Proteins; D021122:Protein Subunits; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2