title: Alternative splicing in intracellular loop connecting domains II and III of the alpha 1 subunit of Cav1.2 Ca2+ channels predicts two-domain polypeptides with unique C-terminal tails.
abstract: Novel splice variants of the alpha(1) subunit of the Ca(v)1.2 voltage-gated Ca(2+) channel were identified that predicted two truncated forms of the alpha(1) subunit comprising domains I and II generated by alternative splicing in the intracellular loop region linking domains II and III. In rabbit heart splice variant 1 (RH-1), exon 19 was deleted, which resulted in a reading frameshift of exon 20 with a premature termination codon and a novel 19-amino acid carboxyl-terminal tail. In the RH-2 variant, exons 17 and 18 were deleted, leading to a reading frameshift of exons 19 and 20 with a premature stop codon and a novel 62-amino acid carboxyl-terminal tail. RNase protection assays with RH-1 and RH-2 cRNA probes confirmed the expression in cardiac and neuronal tissue but not skeletal muscle. The deduced amino acid sequence from full-length cDNAs encoding the two variants predicted polypeptides of 99.0 and 99.2 kDa, which constituted domains I and II of the alpha(1) subunit of the Ca(v)1.2 channel. Antipeptide antibodies directed to sequences in the second intracellular loop between domains II and III identified the 240-kDa Ca(v)1.2 subunit in sarcolemmal and heavy sarcoplasmic reticulum (HSR) membranes and a 99-kDa polypeptide in the HSR. An antipeptide antibody raised against unique sequences in the RH-2 variant also identified a 99-kDa polypeptide in the HSR. These data reveal the expression of additional Ca(2+) channel structural units generated by alternative splicing of the Ca(v)1.2 gene.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Wielowieyski
authors.forename: J T
authors.initials: JT
authors.lastname: Wigle
authors.forename: M
authors.initials: M
authors.lastname: Salih
authors.forename: P
authors.initials: P
authors.lastname: Hum
authors.forename: B S
authors.initials: BS
authors.lastname: Tuana
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005091:Exons; D016368:Frameshift Mutation; D014644:Genetic Variation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D016296:Mutagenesis; D009206:Myocardium / Q000378:metabolism; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; C419385:L-type calcium channel alpha(1C); D021122:Protein Subunits