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Updated: Aug 18, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Peptide and protein modulation of local Ca2+ release events in permeabilized skeletal muscle fibers
Martin F Schneider1, George G Rodney
1Dept. of Biochemistry and Molecular Biology and Interdisciplinary Program in Muscle Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA. mschneid@umaryland.edu
Abstract:
Local discrete elevations in myoplasmic Ca2+ (Ca2+ sparks) arise from the opening of a small group of RyRs. Summation of a large number of Ca2+ sparks gives rise to the whole cell Ca2+ transient necessary for muscle contraction, Unlike sarcoplasmic reticulum vesicle preparations and isolated single channels in artificial membranes, the study of Ca2+ sparks provides a means to understand the regulation of a small group of RyRs in the environment of a functionally intact triad and in the presence of endogenous regulatory proteins. To gain insight into the mechanisms that regulate the gating of RyRs we have utilized laser scanning confocal microscopy to measure Ca2+ sparks in permeabilized frog skeletal muscle fibers. This review summarizes our recent studies using both exogenous (ImperatoxinA and domain peptides) and endogenous (calmodulin) modulators of RyR to gain insight into the number of RyR Ca2+ release channels underlying a Ca2+ spark, how domain-domain interactions within RyR regulate the functional state of the channel as well as gating mechanisms of RyR in living muscle fibers.
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