Roles of a membrane-localized beta subunit in the formation and targeting of functional L-type Ca2+ channels.
We report several unexpected findings that provide novel insights into the properties and interactions of the alpha 1 and beta subunits of dihydropyridine-sensitive L-type channels. First, the beta 2a subunit was expressed as multiple species of 68-72 kDa; the 70-72-kDa species arose from post-translational modification. Second, cell fractionation and immunocytochemical studies indicated that the hydrophilic beta 2a subunit, when expressed alone, was membrane-localized. Third, the beta 2a subunit increased the membrane localization of the alpha 1 subunit and the number of cells expressing L-type Ca2+ currents, without affecting the total amount of the expressed alpha 1C subunit. Expression of maximal currents in alpha 1C/beta 2a cotransfected cells paralleled the time course of expression of the beta subunit. Taken together, these results suggest that the beta subunit plays multiple roles in the formation, stabilization, targeting, and modulation of L-type channels.
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA.
A J
AJ
Chien
X
X
Zhao
R E
RE
Shirokov
T S
TS
Puri
C F
CF
Chang
D
D
Sun
E
E
Rios
M M
MM
Hosey
D000595:Amino Acid Sequence; D001483:Base Sequence; D015220:Calcium Channels / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology*; D020746:Calcium Channels, L-Type; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D003001:Cloning, Molecular; D003513:Cycloheximide / Q000494:pharmacology; D017931:DNA Primers; D005455:Fluorescent Antibody Technique; D005822:Genetic Vectors; D006801:Humans; D007668:Kidney; D007700:Kinetics; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D011994:Recombinant Proteins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D017931:DNA Primers; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D003513:Cycloheximide