Cloning of the β2a subunit of the voltage-dependent calcium channel from human heart:: Cooperative effect of α2/δ and β2a on the membrane expression of the α1c subunit

Expression and membrane localization of an epitope-tagged human Ca2+ channel alpha(1C) subunit were monitored in Xenopus oocytes by confocal microscopy 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, respectively. Simultaneous coexpression of alpha(2)/delta and beta(2a) subunits resulted in a cooperative (470%) increase. Electrophysiological measurements performed in parallel revealed that the current augmentation by the alpha(2)/delta subunit is totally attributable to an increase in channel density, whereas the beta(2a) subunit, in addition to increasing channel density, also facilitates channel opening, (C) 2000 Academic Press.