Conformational coupling of DHPR and RyR1 in skeletal myotubes is influenced by long-range allosterism: Evidence for a negative regulatory module

Eun Hui Lee, J. Rafael Lopez, Jingzi Li, Feliciano Protasi, Isaac N Pessah, Do Han Kim, P. D. Allen

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

Four ryanodine receptor type 1 and 2 chimeras (R4, R9, R10, and R16) and their respective wild-type ryanodine receptors (type 1 and 2; wtRyR1 and wtRyR2) were expressed in dyspedic 1B5 to identify possible negative regulatory modules of the Ca2+ release channel that are under the influence of the dihydropyridine receptor (DHPR). Responses of intact 1B5 myotubes expressing each construct to caffeine in the absence or presence of either La3+ and Cd2+ or the organic DHPR blocker nifedipine were determined by imaging single 1B5 myotubes loaded with fluo 4. The presence of La3+ and Cd2+ or nifedipine in the external medium at concentrations known to block Ca2+ entry through the DHPRs significantly decreased the caffeine EC50 of wtRyR1 (2.80 ± 0.12 to 0.83 ± 0.09 mM; P < 0.05). On the other hand, DHPR blockade did not significantly alter the caffeine EC50 values of wtRyR2, chimeras R10 and R16, whereas the caffeine EC50 values of chimeras R4 and R9 were significantly increased (1.27 ± 0.05 to 2.60 ± 0. 16 mM, and 1.15 ± 0.03 to 2.11 ± 0.32 mM, respectively; P < 0.05). Despite the fact that all the chimeras form fully functional Ca 2+ release channels in situ, sarcoplasmic reticulum (SR) containing R4, R10, and R16 did not possess high-affinity binding of [ 3H]ryanodine regardless of Ca2+ concentration. These results suggest the presence of an interaction between RyR1 and the DHPR, which is not present in RyR2, that contributes negative control of SR Ca2+ release induced by direct agonists such as caffeine. Although we were unable to define the negative module using RyR1-RyR2 chimeras, they further demonstrated that the RyR is very sensitive to long-range allosterism.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume286
Issue number1 55-1
StatePublished - Jan 2004

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Keywords

  • Dihydropyridine receptor
  • Excitation-contraction coupling
  • Negative module
  • Ryanodine receptor type 1

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

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