Calmodulin binding is dispensable for Rem-mediated Ca2+ channel inhibition.
GTPases of the Ras-related RGK family are negative regulators of high voltage-activated (HVA) Ca2+ channel activity. In this study, we examined the role of calmodulin (CaM) association in Rem-mediated Ca2+ channel inhibition. We found that the Rem/CaM interaction is Ca2+-dependent, and that truncation of the Rem C-terminus before position 277 prevents CaM binding. Serial mutagenesis of the Rem C-terminus between residues 265 and 276 to alanine generated two mutants (Rem(L271A) and Rem(L274A)) that displayed reduced CaM binding, and a subset of these mutants displayed significantly lower cell periphery localization than Rem(WT). However, reductions in CaM association or membrane trafficking did not affect function, as all Rem mutants could completely inhibit Ca2+ channels. The Rem(1-275) truncation mutant partially inhibited Ca2+ channel activity despite its inability to bind CaM. Taken together, these studies indicate that CaM association is not essential for either Rem-mediated Ca2+ channel inhibition or plasma membrane localization.
Correll
Robert N
RN
Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536-0509, USA. rncorr0@uky.edu
Pang
Chunyan
C
Niedowicz
Dana M
DM
Satin
Jonathan
J
Andres
Douglas A
DA
D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers; D015220:Calcium Channels / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D016296:Mutagenesis; D050505:Mutant Proteins / Q000378:metabolism; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002147:Calmodulin; D050505:Mutant Proteins; D020559:Monomeric GTP-Binding Proteins; D002118:Calcium