Stac3 has a direct role in skeletal muscle-type excitation-contraction coupling that is disrupted by a myopathy-causing mutation

Alexander Polster, Benjamin R. Nelson, Eric N. Olson, Kurt G. Beam

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

In skeletal muscle, conformational coupling between Cav 1.1 in the plasma membrane and type 1 ryanodine receptor (RyR1) in the sarcoplasmic reticulum (SR) is thought to underlie both excitation-contraction (EC) coupling Ca2+ release from the SR and retrograde coupling by which RyR1 increases the magnitude of the Ca2+ current via Cav 1.1. Recent work has shown that EC coupling fails in muscle from mice and fish null for the protein Stac3 (SH3 and cysteine-rich domain 3) but did not establish the functional role of Stac3 in the Cav 1.1-RyR1 interaction. We investigated this using both tsA201 cells and Stac3 KO myotubes. While confirming in tsA201 cells that Stac3 could support surface expression of Cav 1.1 (coexpressed with its auxiliary β1a and α21 subunits) and the generation of large Ca2+ currents, we found that without Stac3 the auxiliary γ1 subunit also supported membrane expression of Cav 1.1/β1a21 , but that this combination generated only tiny Ca2+ currents. In Stac3 KO myotubes, there was reduced, but still substantial Cav 1.1 in the plasma membrane. However, the Cav 1.1 remaining in Stac3 KO myotubes did not generate appreciable Ca2+ currents or EC coupling Ca2+ release. Expression of WT Stac3 in Stac3 KO myotubes fully restored Ca2+ currents and EC coupling Ca2+ release, whereas expression of Stac3w280s (containing the Native American myopathy mutation) partially restored Ca2+ currents but only marginally restored EC coupling. We conclude that membrane trafficking of Cav 1.1 is facilitated by, but does not require, Stac3, and that Stac3 is directly involved in conformational coupling between Cav 1.1 and RyR1.

Original languageEnglish (US)
Pages (from-to)10986-10991
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number39
DOIs
StatePublished - Sep 27 2016

Keywords

  • Excitation-contraction coupling
  • L-type ca channels
  • Stac3 protein

ASJC Scopus subject areas

  • General

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