Abstract

The long term objective of this research is to define the molecular basis of the defects that are responsible for the pharmacogenetic syndrome Malignant Hyperthermia (MH). In this anesthetic reaction that occurs in susceptible individuals during surgery, certain anesthetic agents and depolarizing muscle relaxants trigger a rise in body temperature and muscle rigidity. Using a purebred strain of MH susceptible (MHS) Pietrain pigs, it has been demonstrated that the altered control of sarcoplasmic Ca2+ in MHS in skeletal muscle likely results from specific defects in the sarcoplasmic reticulum (SR) and transverse tubule (TT) membranes. The first hypothesis to be tested in this project is that an abnormality in the SR calcium release channel/ryanodine receptor (Ca/RyR) is responsible for the abnormal calcium regulation in MHS muscle. To this end, rapid calcium release from calcium-filled MHS and normal SR vesicles will be examined. These results will be correlated with both the binding of the high affinity ligand ryanodine, and the single channel kinetics of the Ca/RyR to define the defect in the MHS SR Ca/RyR. The second hypothesis to be tested in this study is that an altered TT dihydropyridine (DHP) receptor contributes to the abnormal sarcoplasmic Ca regulation in MH muscle. It will be determined whether the decreased Bmax for DHP binding to MHS TT is due either to a decreased content of the receptor protein in MHS TT, or to a defect in the DHP receptor of MHS TT such that its regulation of excitation-contraction coupling is altered in MHS muscle. Should these data indicated an altered conformation of the DHP receptor in MHS TT, the single calcium channel kinetics of this receptor in the two types of TT will be characterized. Since volatile anesthetics and dantrolene (which blocks the MH response) may interact with both SR Ca/RyR and the TT DHP receptor, it will also be appropriate to examine the effect of these agents on the single calcium channel kinetics of these two components in MHS and normal TT membranes. An understanding of the nature of MH will be of great assistance in the future identification, management and treatment of MHS individuals; will provide basic information regarding the protein complexes that effect excitation-contraction in normal skeletal muscle; and will be important in the future elucidation of the etiology of many other muscle diseases in which excitation-contraction or calcium regulation is abnormal.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM031382-09
Application #
3279365
Study Section
Surgery, Anesthesiology and Trauma Study Section (SAT)
Project Start
1984-04-01
Project End
1995-03-31
Budget Start
1992-04-01
Budget End
1993-03-31
Support Year
9
Fiscal Year
1992
Total Cost
Indirect Cost

  Institution

Name
University of Minnesota Twin Cities
Department
Type
Schools of Veterinary Medicine
DUNS #
168559177
City
Minneapolis
State
MN
Country
United States
Zip Code
55455

  Publications

Fruen, Bradley R; Balog, Edward M; Schafer, Janet et al. (2005) Direct detection of calmodulin tuning by ryanodine receptor channel targets using a Ca2+-sensitive acrylodan-labeled calmodulin. Biochemistry 44:278-84
Fruen, Bradley R; Black, D J; Bloomquist, Rachel A et al. (2003) Regulation of the RYR1 and RYR2 Ca2+ release channel isoforms by Ca2+-insensitive mutants of calmodulin. Biochemistry 42:2740-7
Balog, Edward M; Norton, Laura E; Bloomquist, Rachel A et al. (2003) Calmodulin oxidation and methionine to glutamine substitutions reveal methionine residues critical for functional interaction with ryanodine receptor-1. J Biol Chem 278:15615-21
Louis, C F; Balog, E M; Fruen, B R (2001) Malignant hyperthermia: an inherited disorder of skeletal muscle Ca+ regulation. Biosci Rep 21:155-68
Balog, E M; Fruen, B R; Shomer, N H et al. (2001) Divergent effects of the malignant hyperthermia-susceptible Arg(615)-->Cys mutation on the Ca(2+) and Mg(2+) dependence of the RyR1. Biophys J 81:2050-8
Zhao, F; Li, P; Chen, S R et al. (2001) Dantrolene inhibition of ryanodine receptor Ca2+ release channels. Molecular mechanism and isoform selectivity. J Biol Chem 276:13810-6
Balog, E M; Fruen, B R; Kane, P K et al. (2000) Mechanisms of P(i) regulation of the skeletal muscle SR Ca(2+) release channel. Am J Physiol Cell Physiol 278:C601-11
Palnitkar, S S; Mickelson, J R; Louis, C F et al. (1997) Pharmacological distinction between dantrolene and ryanodine binding sites: evidence from normal and malignant hyperthermia-susceptible porcine skeletal muscle. Biochem J 326 ( Pt 3):847-52
Fruen, B R; Mickelson, J R; Louis, C F (1997) Dantrolene inhibition of sarcoplasmic reticulum Ca2+ release by direct and specific action at skeletal muscle ryanodine receptors. J Biol Chem 272:26965-71
Fruen, B R; Kane, P K; Mickelson, J R et al. (1996) Chloride-dependent sarcoplasmic reticulum Ca2+ release correlates with increased Ca2+ activation of ryanodine receptors. Biophys J 71:2522-30

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