title: Apparent lack of physical or functional interaction between CaV1.1 and its distal C terminus.
abstract: CaV1.1 acts as both the voltage sensor that triggers excitation-contraction coupling in skeletal muscle and as an L-type Ca(2+) channel. It has been proposed that, after its posttranslational cleavage, the distal C terminus of CaV1.1 remains noncovalently associated with proximal CaV1.1, and that tethering of protein kinase A to the distal C terminus is required for depolarization-induced potentiation of L-type Ca(2+) current in skeletal muscle. Here, we report that association of the distal C terminus with proximal CaV1.1 cannot be detected by either immunoprecipitation of mouse skeletal muscle or by colocalized fluorescence after expression in adult skeletal muscle fibers of a CaV1.1 construct labeled with yellow fluorescent protein (YFP) and cyan fluorescent protein on the N and C termini, respectively. We found that L-type Ca(2+) channel activity was similar after expression of constructs that either did (YFP-CaV1.11860) or did not (YFP-CaV1.11666) contain coding sequence for the distal C-terminal domain in dysgenic myotubes null for endogenous CaV1.1. Furthermore, in response to strong (up to 90 mV) or long-lasting prepulses (up to 200 ms), tail current amplitudes and decay times were equally increased in dysgenic myotubes expressing either YFP-CaV1.11860 or YFP-CaV1.11666, suggesting that the distal C-terminal domain was not required for depolarization-induced potentiation. Thus, our experiments do not support the existence of either biochemical or functional interactions between proximal CaV1.1 and the distal C terminus.
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Ohrtman
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.
authors.forename: Christin F
authors.initials: CF
authors.lastname: Romberg
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.
authors.forename: Ong
authors.initials: O
authors.lastname: Moua
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.
authors.forename: Roger A
authors.initials: RA
authors.lastname: Bannister
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.
authors.forename: S Rock
authors.initials: SR
authors.lastname: Levinson
authors.affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045 kurt.beam@ucdenver.edu.
authors.forename: Kurt G
authors.initials: KG
authors.lastname: Beam
mesh_terms: D000200:Action Potentials; D000595:Amino Acid Sequence; D000818:Animals; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D015640:Ion Channel Gating; D051379:Mice; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: C529218:CACNA1S protein, mouse; D020746:Calcium Channels, L-Type