Temperature and RyR1 Regulate the Activation Rate of Store-Operated Ca^sup 2+^ Entry Current in Myotubes

• Published in: Biophysical journal Vol. 103; no. 2; p. 202
• Main Authors: Yarotskyy, Viktor, Dirksen, Robert T
• Format: Journal Article
• Language: English
• Published: New York Biophysical Society 18.07.2012
• Subjects: Calcium; Cells; Musculoskeletal system; Protein folding; Rodents
• ISSN: 0006-3495; 1542-0086

Store-operated calcium entry (SOCE) is an important ... entry pathway in skeletal muscle. However, direct electrophysiological recording and full characterization of the underlying SOCE current in skeletal muscle cells (ISkCRAC) has not been reported. Here, we characterized the biophysical properties, pharmacological profile, and molecular identity of ISkCRAC in skeletal myotubes, as well as the regulation of its rate of activation by temperature and the type I ryanodine receptor (RyR1). ISkCRAC exhibited many hallmarks of ... release activated ... currents (ICRAC): store dependence, strong inward rectification, positive reversal potential, limited cesium permeability, and sensitivity to SOCE channel blockers. ISkCRAC was reduced by siRNA knockdown of stromal interaction molecule 1 and expression of dominant negative Orai1. Average ISkCRAC current density at -80mV was 1.00 ± 0.05 pA/pF. In the presence of 20 mM intracellular EGTA, ISkCRAC activation occurred over tens of seconds during repetitive depolarization at 0.5Hz and was inhibited by treatment with 100 ...M ryanodine. The rate of SOCE activation was reduced threefold in myotubes from RyR1-null mice and increased 4.6-fold at physiological temperatures (35-37...C). These results show that ISkCRAC exhibits similar biophysical, pharmacological, and molecular properties as ICRAC in nonexcitable cells and its rate of activation during repetitive depolarization is strongly regulated by temperature and RyR1 activity. (ProQuest: ... denotes formulae/symbols omitted.)