The calmodulin binding region of the skeletal ryanodine receptor acts as a self-modulatory domain

Xinsheng Zhu, Jyothi Ghanta, Jeffrey W. Walker, Paul D. Allen, Héctor H. Valdivia

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

A synthetic peptide (CaMBP) matching amino acids 3614-3643 of the skeletal ryanodine receptor (RyR1) binds to both Ca2+-free calmodulin (CaM) and Ca2+-bound CaM with nanomolar affinity [J. Biol. Chem. 276 (2001) 2069]. We report here that CaMBP increases [3H]ryanodine binding to RyR1 in a dose- and Ca2+-dependent manner; it also induces Ca2+ release from SR vesicles, and increases open probability (Po) of single RyR channels reconstituted in planar lipid bilayers. Further, CaMBP removes CaM associated with SR vesicles and increases [3H]ryanodine binding to purified RyR1, suggesting that its mechanism of action is two-fold: it removes endogenous inhibitors and also interacts directly with complementary regions in RyR1. Remarkably, the N-terminus of CaMBP activates RyRs while the C-terminus of CaMBP inhibits RyR activity, suggesting the presence of two discrete functional subdomains within this region. A ryr1 mutant lacking this region, RyR1-Δ3614-3643, was constructed and expressed in dyspedic myoblasts (RyR1-knockout). The depolarization-, caffeine-and 4-chloro-m-cresol (4-CmC)-induced Ca2+ transients in these cells were dramatically reduced compared with cells expressing wild type RyR1. Deletion of the 3614-3643 region also resulted in profound changes in unitary conductance and channel gating. We thus propose that the RyR1 3614-3643 region acts not only as the CaM binding site, but also as an important modulatory domain for RyR1 function.

Original languageEnglish (US)
Pages (from-to)165-177
Number of pages13
JournalCell Calcium
Volume35
Issue number2
DOIs
StatePublished - Feb 2004
Externally publishedYes

Keywords

  • Ca release channel
  • Calmodulin
  • Excitation-contraction coupling
  • Sarcoplasmic reticulum

ASJC Scopus subject areas

  • Cell Biology
  • Endocrinology

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