Allosterically coupled calcium and magnesium binding sites are unmasked by ryanodine receptor chimeras

Andrew A. Voss, Paul D. Allen, Isaac N Pessah, Claudio F. Perez

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

We studied cation regulation of wild-type ryanodine receptor type 1 (WTRyR1), type 3 (WTRyR3), and RyR3/RyR1 chimeras (Ch) expressed in 1B5 dyspedic myotubes. Using [3H]ryanodine binding to sarcoplasmic reticulum (SR) membranes, Ca2+ titrations with WTRyR3 and three chimeras show biphasic activation that is allosterically coupled to an attenuated inhibition relative to WTRyR1. Chimeras show biphasic Mg2+ inhibition profiles at 3 and 10 μM Ca2+, no observable inhibition at 20 μM Ca2+ and monophasic inhibition at 100 μM Ca2+. Ca2+ imaging of intact myotubes expressing Ch-4 exhibit caffeine-induced Ca2+ transients with inhibition kinetics that are significantly slower than those expressing WTRyR1 or WTRyR3. Four new aspects of RyR regulation are evident: (1) high affinity (H) activation and low affinity (L) inhibition sites are allosterically coupled, (2) Ca2+ facilitates removal of the inherent Mg2+ block, (3) WTRyR3 exhibits reduced cooperativity between H activation sites when compared to WTRyR1, and (4) uncoupling of these sites in Ch-4 results in decreased rates of inactivation of caffeine-induced Ca2+ transients.

Original languageEnglish (US)
Pages (from-to)988-993
Number of pages6
JournalBiochemical and Biophysical Research Communications
Volume366
Issue number4
DOIs
StatePublished - Feb 22 2008

Keywords

  • Calcium-induced calcium release
  • Channel regulation
  • Regulation of calcium signaling
  • Ryanodine receptors
  • Skeletal muscle

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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