title: Function of a truncated dihydropyridine receptor as both voltage sensor and calcium channel.
abstract: The skeletal muscle dihydropyridine (DHP) receptor serves dual functions, as a voltage sensor for excitation-contraction coupling and as an L-type calcium channel. Biochemical analysis indicates the presence of two forms of the DHP receptor polypeptide in skeletal muscle, a full-length translation product present as a minor species and a much more abundant form that has a truncated carboxy-terminus. On the basis of these and other observations, it has been proposed that, in skeletal muscle, only the full-length DHP receptor can function as a calcium channel and that the truncated form can only function as a voltage sensor for excitation-contraction coupling. To resolve this issue, we have now constructed a complementary DNA (pC6 delta 1) encoding a protein corresponding to the truncated DHP receptor in skeletal muscle. Expression of pC6 delta 1 in dysgenic myotubes fully restores both excitation-contraction coupling and calcium current, consistent with the idea that a single class of DHP receptors performs both functions.
authors.affiliation: Department of Physiology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins 80523.
authors.forename: K G
authors.initials: KG
authors.lastname: Beam
authors.forename: B A
authors.initials: BA
authors.lastname: Adams
authors.forename: T
authors.initials: T
authors.lastname: Niidome
authors.forename: S
authors.initials: S
authors.lastname: Numa
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000502:physiology*; D004594:Electrophysiology; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000502:physiology; D016296:Mutagenesis; D011817:Rabbits
chemical_list: D015220:Calcium Channels; D002118:Calcium