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Imperatoxin a enhances Ca(2+) release in developing skeletal muscle containing ryanodine receptor type 3
Thomas Nabhani1, Xinsheng Zhu, Ilenia Simeoni
1Department of Physiology and Biophysics, University of Illinois at Chicago College of Medicine, Chicago, Illinois 60607, USA.
Biophysical Journal
|February 28, 2002
Summary
Ryanodine receptor 3 (RyR3) amplifies calcium release in muscle cells by working with RyR1. This interaction enhances muscle excitation-contraction coupling, particularly when stimulated by imperatoxin A.
Area of Science:
- Muscle physiology
- Molecular biology
- Calcium signaling
Background:
- Adult mammalian skeletal muscles primarily express ryanodine receptor 1 (RyR1), crucial for excitation-contraction coupling.
- Neonatal muscles express both RyR1 and RyR3, but the specific role of RyR3 remains unclear.
Purpose of the Study:
- To investigate the functional role of RyR3 in calcium release within myotubes.
- To determine if RyR3 contributes to excitation-contraction coupling and how it interacts with RyR1.
Main Methods:
- Studied calcium release in wild-type and RyR3 knockout myotubes.
- Utilized imperatoxin A (IpTxa) to stimulate ryanodine receptors.
- Performed electrophysiological recordings and radioligand binding assays.
Main Results:
- IpTxa significantly increased calcium release amplitude and rate in wild-type myotubes but not in RyR3 knockout myotubes.
- IpTxa enhanced [(3)H]ryanodine binding to both RyR1 and RyR3.
- IpTxa altered single RyR1 and RyR3 channel gating and conductance.
Conclusions:
- RyR3 is functional in myotubes and can amplify calcium release signals initiated by RyR1.
- IpTxa interacts with both RyR1 and RyR3, suggesting a modulatory role in calcium handling.
- RyR3's amplification of RyR1-mediated calcium release may involve calcium-induced mechanisms.