Roles of a membrane-localized β subunit in the formation and targeting of functional L-type Ca2+ channels

Abstract

We report several unexpected findings that provide novel insights into the properties and interactions of the α1 and β subunits of dihydropyridine-sensitive L-type channels. First, the β2a 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 β2a subunit, when expressed alone, was membrane-localized. Third, the β2a subunit increased the membrane localization of the α1 subunit and the number of cells expressing L-type Ca2+ currents, without affecting the total amount of the expressed α1C subunit. Expression of maximal currents in α1C/β2a co-transfected cells paralleled the time course of expression of the β subunit. Taken together, these results suggest that the β subunit plays multiple roles in the formation, stabilization, targeting, and modulation of L-type channels.