title: Mice with cardiac-specific sequestration of the beta-subunit of the L-type calcium channel.
abstract: The beta subunit of the L-type voltage-dependent calcium channel modifies the properties of the channel complex by both allosteric modulation of the alpha1 subunit function and by chaperoning the translocation of the alpha1 subunit to the plasma membrane. The goal of this study was to investigate the functional effect of changing the in vivo stoichiometry between the alpha1 and beta subunits by creating a dominant negative expression system in a transgenic mouse model. The high affinity beta subunit-binding domain of the alpha1 subunit was overexpressed in a cardiac-specific manner to act as a beta subunit trap. We found that the predominant beta isoform was located primarily in the membrane bound fraction of heart protein, whereas the beta1 and beta3 were mostly cytosolic. There was a significant diminution of the amount of beta2 in the membrane fraction of the transgenic animals, resulting in a decrease in contractility of the heart and a decrease in L-type calcium current density in the myocyte. However, there were no distinguishable differences in beta1 and beta3 protein expression levels in the membrane bound fraction between transgenic and non-transgenic animals. Since the beta1 and beta3 isoforms only make up a small portion of the total beta subunit in the heart, slight changes in this fraction are not detectable using Western analysis. In contrast, beta1 and beta3 in skeletal muscle and brain, the predominant isoforms in these tissues, respectively, are membrane bound.
authors.affiliation: Department of Surgery, Institute of Molecular Pharmacology and Biophysics, University of Cincinnati, College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0828, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Serikov
authors.forename: Ilona
authors.initials: I
authors.lastname: Bodi
authors.forename: Sheryl E
authors.initials: SE
authors.lastname: Koch
authors.forename: James N
authors.initials: JN
authors.lastname: Muth
authors.forename: Gabor
authors.initials: G
authors.lastname: Mikala
authors.forename: Sergey G
authors.initials: SG
authors.lastname: Martinov
authors.forename: Hannelore
authors.initials: H
authors.lastname: Haase
authors.forename: Arnold
authors.initials: A
authors.lastname: Schwartz
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004594:Electrophysiology; D005799:Genes, Dominant; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D014018:Tissue Distribution
chemical_list: D020746:Calcium Channels, L-Type; D020033:Protein Isoforms