|
|
||||||||
1 Department of Zoology, La Trobe University, Bundoora, Victoria 3086, Australia; and 2 Boston Biomedical Research Institute, Watertown, Massachusetts 02472
Mutations in the central domain of the skeletal muscle ryanodine receptor (RyR) cause malignant hyperthermia (MH). A synthetic peptide (DP4) in this domain (Leu-2442-Pro-2477) produces enhanced ryanodine binding and sensitized Ca2+ release in isolated sarcoplasmic reticulum, similar to the properties in MH, possibly because the peptide disrupts the normal interdomain interactions that stabilize the closed state of the RyR (Yamamoto T, El-Hayek R, and Ikemoto N. J Biol Chem 275: 11618-11625, 2000). Here, DP4 was applied to mechanically skinned fibers of rat muscle that had the normal excitation-contraction coupling mechanism still functional to determine whether muscle fiber responsiveness was enhanced. DP4 (100 µM) substantially potentiated the Ca2+ release and force response to caffeine (8 mM) and to low [Mg2+] (0.2 mM) in every fiber examined, with no significant effect on the properties of the contractile apparatus. DP4 also potentiated the response to submaximal depolarization of the transverse tubular system by ionic substitution. Importantly, DP4 did not significantly alter the size of the twitch response elicited by action potential stimulation. These results support the proposal that DP4 causes an MH-like aberration in RyR function and are consistent with the voltage sensor triggering Ca2+ release by destabilizing the closed state of the RyRs.
excitation-contraction coupling; voltage sensor; action potential; malignant hyperthermia; caffeine
This article has been cited by other articles:
![]() |
S. E. Lehnart, X. H.T. Wehrens, and A. R. Marks Defective Ryanodine Receptor Interdomain Interactions May Contribute to Intracellular Ca2+ Leak: A Novel Therapeutic Target in Heart Failure Circulation, June 28, 2005; 111(25): 3342 - 3346. [Full Text] [PDF] |
||||
![]() |
T. Murayama, T. Oba, S. Kobayashi, N. Ikemoto, and Y. Ogawa Postulated role of interdomain interactions within the type 1 ryanodine receptor in the low gain of Ca2+-induced Ca2+ release activity of mammalian skeletal muscle sarcoplasmic reticulum Am J Physiol Cell Physiol, June 1, 2005; 288(6): C1222 - C1230. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. M. Gallant, J. Hart, K. Eager, S. Curtis, and A. F. Dulhunty Caffeine sensitivity of native RyR channels from normal and malignant hyperthermic pigs: effects of a DHPR II-III loop peptide Am J Physiol Cell Physiol, April 1, 2004; 286(4): C821 - C830. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |