Coupling of excitation to Ca2+ release is modulated by dysferlin.

Abstract

KEY POINTS:

Dysferlin, the protein missing in limb girdle muscular dystrophy 2B and Miyoshi myopathy, concentrates in transverse tubules of skeletal muscle, where it stabilizes voltage-induced Ca2+ transients against loss after osmotic shock injury (OSI). Local expression of dysferlin in dysferlin-null myofibres increases transient amplitude to control levels and protects them from loss after OSI. Inhibitors of ryanodine receptors (RyR1) and L-type Ca2+ channels protect voltage-induced Ca2+ transients from loss; thus both proteins play a role in injury in dysferlin's absence. Effects of Ca2+ -free medium and S107, which inhibits SR Ca2+ leak, suggest the SR as the primary source of Ca2+ responsible for the loss of the Ca2+ transient upon injury. Ca2+ waves were induced by OSI and suppressed by exogenous dysferlin. We conclude that dysferlin prevents injury-induced SR Ca2+ leak.

ABSTRACT:

Dysferlin concentrates in the transverse tubules of skeletal muscle and stabilizes Ca2+ transients when muscle fibres are subjected to osmotic shock injury (OSI). We show here that voltage-induced Ca2+ transients elicited in dysferlin-null A/J myofibres were smaller than control A/WySnJ fibres. Regional expression of Venus-dysferlin chimeras in A/J fibres restored the full amplitude of the Ca2+ transients and protected against OSI. We also show that drugs that target ryanodine receptors (RyR1: dantrolene, tetracaine, S107) and L-type Ca2+ channels (LTCCs: nifedipine, verapamil, diltiazem) prevented the decrease in Ca2+ transients in A/J fibres following OSI. Diltiazem specifically increased transients by ∼20% in uninjured A/J fibres, restoring them to control values. The fact that both RyR1s and LTCCs were involved in OSI-induced damage suggests that damage is mediated by increased Ca2+ leak from the sarcoplasmic reticulum (SR) through the RyR1. Congruent with this, injured A/J fibres produced Ca2+ sparks and Ca2+ waves. S107 (a stabilizer of RyR1-FK506 binding protein coupling that reduces Ca2+ leak) or local expression of Venus-dysferlin prevented OSI-induced Ca2+ waves. Our data suggest that dysferlin modulates SR Ca2+ release in skeletal muscle, and that in its absence OSI causes increased RyR1-mediated Ca2+ leak from the SR into the cytoplasm.

• Authors: Valeriy Lukyanenko, Joaquin M Muriel, Robert J Bloch
• Journal: The Journal of physiology (J Physiol) Vol. 595 Issue 15 Pg. 5191-5207 (08 01 2017) ISSN: 1469-7793 [Electronic] England
• PMID: 28568606 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Chemical References

• Calcium Channels, L-Type
• Dysf protein, mouse
• Dysferlin
• Ryanodine Receptor Calcium Release Channel
• S-107 compound
• Thiazepines
• ryanodine receptor 1, mouse
• Calcium

Topics

• Animals
• Calcium (physiology)
• Calcium Channels, L-Type (physiology)
• Dysferlin (genetics, physiology)
• Mice, Knockout
• Muscle Fibers, Skeletal (physiology)
• Osmotic Pressure (physiology)
• Ryanodine Receptor Calcium Release Channel (physiology)
• Sarcoplasmic Reticulum (physiology)
• Thiazepines (pharmacology)