title: Characterization of auto-regulation of the human cardiac alpha1 subunit of the L-type calcium channel: importance of the C-terminus.
abstract: The carboxyl terminal of the L-type calcium channel alpha1C subunit comprises approximately one third of the primary structure of the alpha1 subunit (> 700 amino acids residues). This region is sensitive to limited posttranslational processing. In heart and brain the alpha1C subunits are found to be truncated but the C-terminal domain remains functionally present. Based on our previous data we hypothesized that the distal C-terminus (approximately residues 1650-1950) harbors an important, predominantly inhibitory domain. We generated C-terminal-truncated alpha1C mutants, and after expressing them in combination with a beta3 subunit in HEK-293 cells, electrophysiological experiments were carried out. In order to dissect the important inhibitory part of the C-terminus, trypsin was dialyzed into the cells. The data provide evidence that there are multiple residues within the inhibitory domain that are crucial to the inhibitory process as well as to the enhancement of expressed current by intracellular application of proteases. In addition, the expression of the chimeric mutant alpha(1C)delta1673-DRK1 demonstrated that the C-terminal is specific for the heart channel.
authors.affiliation: Institute of Molecular Pharmacology and Biophysics, Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0828, USA.
authors.forename: Gabor
authors.initials: G
authors.lastname: Mikala
authors.forename: Ilona
authors.initials: I
authors.lastname: Bodi
authors.forename: Udo
authors.initials: U
authors.lastname: Klockner
authors.forename: Maria
authors.initials: M
authors.lastname: Varadi
authors.forename: Gyula
authors.initials: G
authors.lastname: Varadi
authors.forename: Sheryl E
authors.initials: SE
authors.lastname: Koch
authors.forename: Arnold
authors.initials: A
authors.lastname: Schwartz
mesh_terms: D017398:Alternative Splicing; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism; D020746:Calcium Channels, L-Type; D002460:Cell Line; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
chemical_list: C079146:CACNA1C protein, human; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D012313:RNA; D014357:Trypsin