Malignant hyperthermia susceptibility arising from altered resting coupling between the skeletal muscle L-type Ca2+ channel and the type 1 ryanodine receptor

Jose Miguel Eltit, Roger A. Bannister, Ong Moua, Francisco Altamirano, Philip M. Hopkins, Isaac N Pessah, Tadeusz F. Molinski, Jose R. López, Kurt G. Beam, Paul D. Allen

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Malignant hyperthermia (MH) susceptibility is a dominantly inherited disorder in which volatile anesthetics trigger aberrant Ca2+ release in skeletal muscle and a potentially fatal rise in perioperative body temperature. Mutations causing MH susceptibility have been identified in two proteins critical for excitation-contraction (EC) coupling, the type 1 ryanodine receptor (RyR1) and CaV1.1, the principal subunit of the L-type Ca2+ channel. All of the mutations that have been characterized previously augment EC coupling and/or increase the rate of L-type Ca 2+ entry. The CaV1.1 mutation R174W associated with MH susceptibility occurs at the innermost basic residue of the IS4 voltage-sensing helix, a residue conserved among all CaV channels [Carpenter D, et al. (2009) BMC Med Genet 10:104-115.]. To define the functional consequences of this mutation, we expressed it in dysgenic (CaV1.1 null) myotubes. Unlike previously described MH-linked mutations in CaV1.1, R174W ablated the L-type current and had no effect on EC coupling. Nonetheless, R174W increased sensitivity of Ca2+ release to caffeine (used for MH diagnostic in vitro testing) and to volatile anesthetics. Moreover, in Ca V1.1 R174W-expressing myotubes, resting myoplasmic Ca2+ levels were elevated, and sarcoplasmic reticulum (SR) stores were partially depleted, compared with myotubes expressing wild-type CaV1.1. Our results indicate that CaV1.1 functions not only to activate RyR1 during EC coupling, but also to suppress resting RyR1-mediated Ca2+ leak from the SR, and that perturbation of CaV1.1 negative regulation of RyR1 leak identifies a unique mechanism that can sensitize muscle cells to MH triggers.

Original languageEnglish (US)
Pages (from-to)7923-7928
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number20
DOIs
StatePublished - May 15 2012

Keywords

  • α
  • 1,4-Dihydropyridine receptor

ASJC Scopus subject areas

  • General

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