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Transient loss of voltage control of Ca2+ release in the presence of maurocalcine in skeletal muscle

Abstract : In skeletal muscle, sarcoplasmic reticulum (SR) calcium release is controlled by the plasma membrane voltage through interactions between the voltage-sensing dihydropyridine receptor (DHPr) and the ryanodine receptor (RYr) calcium release channel. Maurocalcine (MCa), a scorpion toxin peptide presenting some homology with a segment of a cytoplasmic loop of the DHPr, has been previously shown to strongly affect the activity of the isolated RYr. We injected MCa into mouse skeletal muscle fibers and measured intracellular calcium under voltage-clamp conditions. Voltage-activated calcium transients exhibited similar properties in control and in MCa-injected fibers during the depolarizing pulses, and the voltage dependence of calcium release was similar under the two conditions. However, MCa was responsible for a pronounced sustained phase of Ca(2+) elevation that proceeded for seconds following membrane repolarization, with no concurrent alteration of the membrane current. The magnitude of the underlying uncontrolled extra phase of Ca(2+) release correlated well with the peak calcium release during the pulse. Results suggest that MCa binds to RYr that open on membrane depolarization and that this interaction specifically alters the process of repolarization-induced closure of the channels.
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https://www.hal.inserm.fr/inserm-00381709
Contributor : Marco Canepari <>
Submitted on : Monday, November 2, 2009 - 4:15:08 PM
Last modification on : Tuesday, November 19, 2019 - 2:37:36 AM
Long-term archiving on: : Thursday, June 10, 2010 - 9:01:07 PM

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Sandrine Pouvreau, Laszlo Csernoch, Bruno Allard, Jean-Marc Sabatier, Michel de Waard, et al.. Transient loss of voltage control of Ca2+ release in the presence of maurocalcine in skeletal muscle. Biophysical Journal, Biophysical Society, 2006, 91 (6), pp.2206-2215. ⟨10.1529/biophysj.105.078089⟩. ⟨inserm-00381709⟩

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