Cloning of the beta(2a) subunit of the voltage-dependent calcium channel from human heart: Cooperative effect of alpha(2)/delta and beta(2a) on the membrane expression of the alpha(1c) subunit

Expression and membrane localization of an epitope-tagged human Ca2+ channe l alpha(1C) subunit were monitored in Xenopus oocytes by confocal microscop y and electrophysiological recording. When alpha(2)/delta and beta(2a) were separately coexpressed with the alpha(1C) subunit, assessment by confocal microscopy showed an 86 and 225% increase of the channel density, respectiv ely. Simultaneous coexpression of alpha(2)/delta and beta(2a) subunits resu lted in a cooperative (470%) increase. Electrophysiological measurements pe rformed in parallel revealed that the current augmentation by the alpha(2)/ delta subunit is totally attributable to an increase in channel density, wh ereas the beta(2a) subunit, in addition to increasing channel density, also facilitates channel opening, (C) 2000 Academic Press.