Plasma Membrane Targeting of High-Voltage Activated Calcium Channels

Abstract

Rem2 is a small GTP-binding protein of the RGK family. It is targeted to the cell membrane where it interacts with the beta subunit of calcium channels and abolishes or reduces endogenous or exogenous calcium currents, and also has known interactions with calmodulin and 14-3-3. Rem2 is unique in the RGK family, being found predominantly in the brain and upregulated in response to stimulation. Knockdown of Rem2 in neuronal cultures results in fewer glutamatergic synapses. We have found that fluorescent-labeled Rem2 changes its subcellular localization in neurons from a diffuse to a punctuate distribution after neuronal stimulation or after activation of NMDA receptors. This rearrangement is calcium dependent and involves the C-terminal 30 residues, suggesting the presence of a self-association domain as well as an autoinhibitory domain that keeps Rem2 diffusely distributed until stimulation. A calmodulin-binding deficient mutant shows very little rearrangement upon stimulation, supporting a role for calcium in this phenomenon.