Abstract

The Rad, Rem, Rem2, and Gem/Kir (RGK) sub-family of small GTP-binding proteins are crucial in regulating high voltage-activated (HVA) calcium channels. RGK proteins inhibit calcium current by either promoting endocytosis or reducing channel activity. They all can associate directly with Ca2+ channel b subunit (CaV beta), and the binding between Ca-V alpha 1/Ca-V beta appears essential for the endocytic promotion of Ca(V)1.X, Ca(V)2.1, and Ca(V)2.2 channels. In this study, we investigated the inhibition of Ca(V)2.3 channels by RGK proteins in the absence of CaV beta. To this end, Xenopus laevis oocytes expressing Ca(V)2.3 channels devoid of auxiliary subunit were injected with purified Gem and Rem and found that only Gem had an effect. Ca currents and charge movements were reduced by injection of Gem, pointing to a reduction in the number of channels in the plasma membrane. Since this reduction was ablated by co-expression of the dominant-negative mutant of dynamin K44A, enhanced endocytosis appears to mediate this reduction in the number of channels. Thus, Gem inhibition of Ca(V)2.3 channels would be the only example of a Ca-V beta independent promotion of dynamin-dependent endocytosis. (C) 2021 Elsevier Inc. All rights reserved.