Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P21817 (RyR1)
 1,154 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type-specific manner in fish skeletal muscle (11). In this study, we compare [(3)H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [(3)H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (P(o)) of RyR1-slow was threefold less than the maximum P(o) of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest P(o) of all the RyR channels and displayed less inhibition at millimolar Ca(2+). The addition of 5 mM Mg-ATP or 2.5 mM beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) to the channels increased the P(o) and [(3)H]ryanodine binding of both RyR1s but also caused a shift in the Ca(2+) dependency curve of RyR1-slow such that Ca(2+)-dependent inactivation was attenuated. [(3)H]ryanodine binding data also showed that Mg(2+)-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca(2+) is regulated in these muscle types.
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PMID:Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle. 1104 75

Dantrolene is a skeletal muscle relaxant which acts by inhibiting intracellular Ca(2+) release from sarcoplasmic reticulum (SR). It is used primarily in the treatment of malignant hyperthermia (MH), a pharmacogenetic sensitivity to volatile anesthetics resulting in massive intracellular Ca(2+) release. Determination of the site and mechanism of action of dantrolene should contribute to the understanding of the regulation of intracellular Ca(2+) release in skeletal muscle. Photoaffinity labeling of porcine SR with [(3)H]azidodantrolene, a photoactivatable analogue of dantrolene, has identified a 160 kDa SR protein with immunologic cross-reactivity to skeletal muscle ryanodine receptor (RyR) as a possible target [Palnitkar et al. (1999) J. Med. Chem. 42, 1872-1880]. Here we demonstrate specific, AMP-PCP-enhanced, [(3)H]azidodantrolene photolabeling of both the RyR monomer and a 160 or 172 kDa protein in porcine and rabbit SR, respectively. The 160/172 kDa protein is shown to be the NH(2)-terminus of the RyR cleaved from the monomer by an endogenous protease activity consistent with that of n-calpain. MALDI-mass spectrometric analysis of the porcine 160 kDa protein identifies it as the 1400 amino acid NH(2)-terminal fragment of the skeletal muscle RyR reportedly generated by n-calpain [Shevchenko et al. (1998) J. Membr. Biol. 161, 33-34]. Immunoprecipitation of solubilized, [(3)H]azidodantrolene-photolabeled SR protein reveals that the cleaved 160/172 kDa protein remains associated with the C-terminal, 410 kDa portion of the RyR. [(3)H]Dantrolene binding to both the intact and the n-calpain-cleaved channel RyR is similarly enhanced by AMP-PCP. n-Calpain cleavage of the RyR does not affect [(3)H]dantrolene binding in the presence of AMP-PCP, but depresses drug binding in the absence of nucleotide. These results demonstrate that the NH(2)-terminus of the RyR is a molecular target for dantrolene, and suggest a regulatory role for both n-calpain activity and ATP in the interaction of dantrolene with the RyR in vivo.
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PMID:The skeletal muscle ryanodine receptor identified as a molecular target of [3H]azidodantrolene by photoaffinity labeling. 1114 48

Mutations G2370A, G2372A, G2373A, G2375A, Y3937A, S3938A, G3939A and K3940A were made in two potential ATP-binding motifs (amino acids 2370-2375 and 3937-3940) in the Ca(2+)-release channel of skeletal-muscle sarcoplasmic reticulum (ryanodine receptor or RyR1). Activation of [(3)H]ryanodine binding by Ca(2+), caffeine and ATP (adenosine 5'-[beta,gamma-methylene]triphosphate, AMP-PCP) was used as an assay for channel opening, since ryanodine binds only to open channels. Caffeine-sensitivity of channel opening was also assayed by caffeine-induced Ca(2+) release in HEK-293 cells expressing wild-type and mutant channels. Equilibrium [(3)H]ryanodine-binding properties and EC(50) values for Ca(2+) activation of high-affinity [(3)H]ryanodine binding were similar between wild-type RyR1 and mutants. In the presence of 1 mM AMP-PCP, Ca(2+)-activation curves were shifted to higher affinity and maximal binding was increased to a similar extent for wild-type RyR1 and mutants. ATP sensitivity of channel opening was also similar for wild-type and mutants. These observations apparently rule out sequences 2370-2375 and 3937-3940 as ATP-binding motifs. Caffeine or 4-chloro-m-cresol sensitivity, however, was decreased in mutants G2370A, G2373A and G2375A, whereas the other mutants retained normal sensitivity. Amino acids 2370-2375 lie within a sequence (amino acids 2163-2458) in which some eight RyR1 mutations have been associated with malignant hyperthermia and shown to be hypersensitive to caffeine and 4-chloro-m-cresol activation. By contrast, mutants G2370A, G2373A and G2375A are hyposensitive to caffeine and 4-chloro-m-cresol. Thus amino acids 2163-2458 form a regulatory domain (malignant hyperthermia regulatory domain 2) that regulates caffeine and 4-chloro-m-cresol sensitivity of RyR1.
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PMID:Mutations to Gly2370, Gly2373 or Gly2375 in malignant hyperthermia domain 2 decrease caffeine and cresol sensitivity of the rabbit skeletal-muscle Ca2+-release channel (ryanodine receptor isoform 1). 1169 96