Caffeine and Halothane Sensitivity of Intracellular Ca2+ Release Is Altered by 15 Calcium Release Channel (Ryanodine Receptor) Mutations Associated with Malignant Hyperthermia and/or Central Core Disease

Jiefei Tong,Hideto Oyamada,Nicolas Demaurex,Sergio Grinstein,Tommie V Mccarthy,David H Maclennan

doi:10.1074/jbc.272.42.26332

Abstract

Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle in which a potentially fatal hypermetabolic crisis can be triggered by commonly used anesthetic agents. To date, 17 mutations in the human RYR1 gene encoding the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum (the ryanodine receptor) have been associated with MH and/or CCD. Although many of these mutations have been linked to MH and/or CCD, with high lod (log of the odds favoring linkage versus nonlinkage) scores, others have been found in single, small families. Independent biochemical evidence for a causal role for these mutations in MH is available for only two mutants. Mutations corresponding to the human MH mutations were made in a full-length rabbit RYR1 cDNA, and wild type and mutant cDNAs were transfected into HEK-293 cells. After about 48 h, intact cells were loaded with the fluorescent Ca2+ indicator, fura-2, and intracellular Ca2+ release, induced by caffeine or halothane, was measured by photometry. Ca2+ release in cells expressing MH or CCD mutant ryanodine receptors was invariably significantly more sensitive to low concentrations of caffeine and halothane than Ca2+ release in cells expressing wild type receptors or receptors mutated in other regions of the molecule. Linear regression analysis showed that there is a strong correlation (r = 0.95, p < 0.001) between caffeine sensitivity of different RYR1 mutants measured by the cellular Ca2+ photometry assay and by the clinical in vitro caffeine halothane contracture test (IVCT). The correlation was weaker, however, for halothane (r = 0.49, p > 0.05). Abnormal sensitivity in the Ca2+ photometry assay provides supporting evidence for a causal role in MH for each of 15 single amino acid mutations in the ryanodine receptor. The study demonstrates the usefulness of the cellular Ca2+ photometry assay in the assessment of the sensitivity to caffeine and halothane of specific ryanodine receptor mutants.

Highlights

Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle in which a potentially fatal hypermetabolic crisis can be triggered by commonly used anesthetic agents
Diagnosis of CCD is made on the basis of the lack of oxidative enzymatic activity in central regions of skeletal muscle fibers [6], the only accepted diagnostic test for MH susceptibility in humans is the North American caffeine halothane contracture test (CHCT) [7] or its European counterpart, the in vitro contracture test (IVCT) [8]
Discordance raises questions concerning the causal nature of such mutations, but other reasons for discordance include the possibility that two MH mutations might be segregating in one family or that the in vitro contracture test for MH susceptibility fails to provide a phenotypic diagnosis of MH with sufficient accuracy for genetic analysis [15]

Summary

Introduction

Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle in which a potentially fatal hypermetabolic crisis can be triggered by commonly used anesthetic agents. We have introduced each of 15 known MH mutations into a rabbit RYR1 cDNA, expressed each mutation in HEK-293 cells, and measured the intracellular responses of wild type and mutated channels to caffeine and halothane.

Results

Conclusion