This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.107.116467v1 94/7/2631    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bannister, R. A. Articles by Beam, K. G. Search for Related Content PubMed PubMed Citation Articles by Bannister, R. A. Articles by Beam, K. G.

Rem Inhibits Skeletal Muscle EC Coupling by Reducing the Number of Functional L-Type Ca²⁺ Channels

R. A. Bannister ^*, H. M. Colecraft  and K. G. Beam ^*

^* Department of Physiology and Biophysics, University of Colorado-Denver, Aurora, Colorado; and Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York

Correspondence: Address reprint requests to K. G. Beam, Dept. of Physiology and Biophysics, University of Colorado-Denver, P.O. Box 6511, Mail Stop F8307, Aurora, CO 80045. Tel.: 303-724-4542; Fax: 303-724-4501; E-mail: kurt.beam{at}uchsc.edu.

In skeletal muscle, the L-type voltage-gated Ca²⁺ channel (1,4-dihydropyridine receptor) serves as the voltage sensor for excitation-contraction (EC) coupling. In this study, we examined the effects of Rem, a member of the RGK (Rem, Rem2, Rad, Gem/Kir) family of Ras-related monomeric GTP-binding proteins, on the function of the skeletal muscle L-type Ca²⁺ channel. EC coupling was found to be weakened in myotubes expressing Rem tagged with enhanced yellow fluorescent protein (YFP-Rem), as assayed by electrically evoked contractions and myoplasmic Ca²⁺ transients. This impaired EC coupling was not a consequence of altered function of the type 1 ryanodine receptor, or of reduced Ca²⁺ stores, since the application of 4-chloro-m-cresol, a direct type 1 ryanodine receptor activator, elicited myoplasmic Ca²⁺ release in YFP-Rem-expressing myotubes that was not distinguishable from that in control myotubes. However, YFP-Rem reduced the magnitude of L-type Ca²⁺ current by 75% and produced a concomitant reduction in membrane-bound charge movements. Thus, our results indicate that Rem negatively regulates skeletal muscle EC coupling by reducing the number of functional L-type Ca²⁺ channels in the plasma membrane.