title: Truncation of murine CaV1.2 at Asp-1904 results in heart failure after birth.
abstract: The carboxyl-terminal intracellular tail of the L-type Ca(2+) channel CaV1.2 modulates various aspects of channel activity.For example, deletion of the carboxyl-terminal sequence at Ser-1905 increased CaV1.2 currents in an expression model. To verify this finding in an animal model, we inserted three stop codons at the corresponding Asp-1904 in the murine CaV1.2 gene. Mice homozygous for the Stop mutation (Stop/Stop mice)were born at a Mendelian ratio but died after birth. Stop/Stop hearts showed reduced beating frequencies and contractions.Surprisingly, Stop/Stop cardiomyocytes displayed reduced IBa and a minor expression of the CaV1.2Stop protein. In contrast,expression of the CaV1.2Stop protein was normal in pooled smooth muscle samples from Stop/Stop embryos. As the CaV1.2 channel exists in a cardiac and smooth muscle splice variant, HK1 and LK1, respectively, we analyzed the consequences of the deletion of the carboxyl terminus in the respective splice variant using the rabbit CaV1.2 clone expressed in HEK293 cells.HEK293 cells transfected with the HK1Stop channel showed a reduced IBa and CaV1.2 expression. Treatment with proteasome inhibitors increased the expression of HK1Stop protein and IBa in HEK293 cells and in Stop/Stop cardiomyocytes indicating that truncation of CaV1.2 containing the cardiac exon 1a amino terminus results in proteasomal degradation of the translated protein. In contrast, HEK293 cells transfected with the LK1Stop channel had normal IBa and CaV1.2 expression. These findings indicate that absence of the carboxyl-terminal tail differentially determines the fate of the cardiac and smooth muscle splice variant of the CaV1.2 channel in the mouse.
authors.affiliation: From the Forschergruppe 923, Institut für Pharmakologie und Toxikologie, Technische Universität München, Biedersteiner Strasse 29, 80802 München, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Domes
authors.forename: Jie
authors.initials: J
authors.lastname: Ding
authors.forename: Toni
authors.initials: T
authors.lastname: Lemke
authors.forename: Anne
authors.initials: A
authors.lastname: Blaich
authors.forename: Jörg W
authors.initials: JW
authors.lastname: Wegener
authors.forename: Julia
authors.initials: J
authors.lastname: Brandmayr
authors.forename: Sven
authors.initials: S
authors.lastname: Moosmang
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D018388:Codon, Terminator; D004195:Disease Models, Animal; D004622:Embryo, Mammalian / Q000378:metabolism; D057809:HEK293 Cells; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009200:Myocardial Contraction / Q000235:genetics; D032383:Myocytes, Cardiac / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009928:Organ Specificity / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011817:Rabbits
chemical_list: C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; D018388:Codon, Terminator; D046988:Proteasome Endopeptidase Complex