Identification of the components controlling inactivation of voltage-gated Ca2+ channels.
Ca(2+)-dependent inactivation (CDI) of L-type voltage-gated Ca(2+) channels limits Ca(2+) entry into neurons, thereby regulating numerous cellular events. Here we present the isolation and purification of the Ca(2+)-sensor complex, consisting of calmodulin (CaM) and part of the channel's pore-forming alpha(1C) subunit, and demonstrate the Ca(2+)-dependent conformational shift that underlies inactivation. Dominant-negative CaM mutants that prevent CDI block the sensor's Ca(2+)-dependent conformational change. We show how Ile1654 in the CaM binding IQ motif of alpha(1C) forms the link between the Ca(2+) sensor and the downstream inactivation machinery, using the alpha(1C) EF hand motif as a signal transducer to activate the putative pore-occluder, the alpha(1C) I-II intracellular linker.
Kim
James
J
Department of Pharmacology, College of Physicians and Surgeons, of Columbia University, 630 West 168th Street, PH 7W 318, New York, NY 10032 USA.
Ghosh
Smita
S
Nunziato
Deborah A
DA
Pitt
Geoffrey S
GS
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002121:Calcium Channel Blockers / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D005260:Female; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D014981:Xenopus
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002147:Calmodulin