Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UNIPROT:P21817 (RyR1)
1,154 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Malignant hyperthermia is an inherited autosomal disorder of skeletal muscle in which certain volatile anesthetics and depolarizing muscle relaxants trigger an abnormally high release of Ca2+ from the intracellular Ca2+ store, the sarcoplasmic reticulum. In about 50% of cases, malignant hyperthermia susceptibility is linked to the gene encoding the skeletal muscle ryanodine receptor/Ca2+ release channel (RYR1). To date, eight point mutations have been identified in human RYR1. Although these mutations are thought to lead to an increased caffeine and halothane sensitivity in the contractile response of skeletal muscle, their functional consequences have not been investigated on the molecular level. In the present study, we provide the first functional characterization of a point mutation located in the central part of RYR1, Gly2434 --> Arg. Using high affinity [3H]ryanodine binding as the experimental approach, we show that this mutation enhances the sensitivity of RYR1 to activating concentrations of Ca2+ and to the exogenous and diagnostically used ligands caffeine and 4-chloro-m-cresol. In parallel, the sensitivity to inhibiting concentrations of Ca2+ and calmodulin was reduced, transferring the mutant Ca2+ release channel into a hyperexcitable state.
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PMID:Functional characterization of a distinct ryanodine receptor mutation in human malignant hyperthermia-susceptible muscle. 903 May 97

The potential role in Ca2+ release channel function of highly conserved, polar, and small amino acids in predicted transmembrane sequences in the rabbit skeletal muscle ryanodine receptor (RyR1) was investigated through mutagenesis. Acidic amino acids Asp3987, Glu4032, Asp4815, Asp4917, Asp4938, and Asp4969 and amidated residues Asn4034, Asn4037, Asn4574, Asn4805, Asn4806, and Gln4933, and Gly4033 were mutated to Ala, and Ala3988 was mutated to Val. When expressed in HEK-293 cells and challenged with either caffeine or 4-chloro-m-cresol, mutants E4032A, N4806A, D4815A, and D4917A did not respond, indicating that Ca2+ release channel function was impaired. None of these mutants exhibited specific binding of [3H]ryanodine. Mutants N4805A and Q4933A showed a diminished response to both caffeine and 4-chloro-m-cresol, but [3H]ryanodine binding was not altered. Other mutant responses and the responses of mutants E4032D, N4806Q or D, D4815N or E, and D4938N or E were unaltered when compared with RyR1. However, mutants E4032Q, D4917N or E, and Q4933N or E displayed neither caffeine nor 4-chloro-m-cresol response nor [3H]ryanodine binding. Sedimentation assays indicated that the nonfunctional mutants did contain tetrameric complexes, implying that defects in the assembly of a functional channel did not occur with specific mutations in transmembrane sequences. These results support the view that amino acids Glu4032 (M2), Asn4806 (M7), Asp4815 (M7), Asp4917 (M10), and Gln4933 (M10) are involved in channel function and regulation.
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PMID:Functional consequences of mutations of conserved, polar amino acids in transmembrane sequences of the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum. 982 55

Of the three known ryanodine receptor (RyR) isoforms expressed in muscle, RyR1 and RyR2 have well-defined roles in contraction. However, studies on mammalian RyR3 have been difficult because of low expression levels relative to RyR1 or RyR2. Using the herpes simplex virus 1 (HSV-1) helper-free amplicon system, we expressed either RyR1 or RyR3 in 1B5 RyR-deficient myotubes. Western blot analysis revealed that RyR1- or RyR3-transduced cells expressed the appropriate RyR isoform of the correct molecular mass. Although RyR1 channels exhibited the expected unitary conductance for Cs(+) in bilayer lipid membranes, 74 of 88 RyR3 channels exhibited pronounced subconductance behavior. Western blot analysis with an FKBP12/12.6-selective antibody reveals that differences in gating behavior exhibited by RyR1 and RyR3 may be, in part, the result of lower affinity of RyR3 for FKBP12. In calcium imaging studies, RyR1 restored skeletal-type excitation-contraction coupling, whereas RyR3 did not. Although RyR3-expressing myotubes were more sensitive to caffeine than those expressing RyR1, they were much less sensitive to 4-chloro-m-cresol (CMC). In RyR1-expressing cells, regenerative calcium oscillations were observed in response to caffeine and CMC but were never seen in RyR3-expressing 1B5 cells. In [(3)H]ryanodine binding studies, only RyR1 exhibited sensitivity to CMC, but both RyR isoforms responded to caffeine. These functional differences between RyR1 and RyR3 expressed in a mammalian muscle context may reflect differences in association with accessory proteins, especially FKBP12, as well as structural differences in modulator binding sites.
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PMID:Divergent functional properties of ryanodine receptor types 1 and 3 expressed in a myogenic cell line. 1105 26

Malignant hyperthermia (MH) is a pharmacogenetic disease triggered by volatile anesthetics and succinylcholine in genetically predisposed individuals. The underlying feature of MH is a hypersensitivity of the calcium release machinery of the sarcoplasmic reticulum, and in many cases this is a result of point mutations in the skeletal muscle ryanodine receptor calcium release channel (RYR1). RYR1 is mainly expressed in skeletal muscle, but a recent report demonstrated the existence of this isoform in human B-lymphocytes. As B-cells can produce a number of cytokines, including endogenous pyrogens, we investigated whether some of the symptoms seen during MH could be related to the involvement of the immune system. Our results show that (i) Epstein-Barr virus-immortalized B-cells from MH-susceptible individuals carrying the V2168M RYR1 gene mutation were more sensitive to the RYR activator 4-chloro-m-cresol and (ii) their peripheral blood leukocytes produce more interleukin (IL)-1beta after treatment with the RYR activators caffeine and 4-chloro-m-cresol, compared with cells from healthy controls. Our result demonstrate that RYR1-mediated calcium signaling is involved in release of IL-1beta from B-lymphocytes and suggest that some of the symptoms seen during an MH episode may be due to IL-1beta production.
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PMID:B-lymphocytes from malignant hyperthermia-susceptible patients have an increased sensitivity to skeletal muscle ryanodine receptor activators. 1167 62

Ryanodine receptor (RYR) is a Ca(2+) channel that mediates Ca(2+) release from intracellular stores. We have used RT-PCR analysis and examined its expression in primary peripheral mononuclear cells (PBMCs) and in 164 hemopoietic cell lines. In PBMCs, type 1 RYR (RYR1) was expressed in CD19(+) B lymphocytes, but less frequently in CD3(+) T lymphocytes and in CD14(+) monocytes. Type 2 RYR (RYR2) was mainly detected in CD3(+) T cells. Induction of RYR1 and/or RYR2 mRNA was found after treatment with stromal cell-derived factor 1, macrophage-inflammatory protein-1alpha (MIP1alpha) or TGF-beta. Type 3 RYR (RYR3) was not detected in PBMCs. Many hemopoietic cell lines expressed not only RYR1 or RYR2 but also RYR3. The expression of the isoforms was not associated with specific cell lineage. We showed that the RYR-stimulating agent 4-chloro-m-cresol (4CmC) induced Ca(2+) release and thereby confirmed functional expression of the RYR in the cell lines expressing RYR mRNA. Moreover, concordant induction of RYR mRNA with Ca(2+) channel function was found in Jurkat T cells. In untreated Jurkat T cells, 4CmC (>1 mM) had no effect on Ca(2+) release, whereas 4CmC (<400 microM) caused Ca(2+) release after the induction of RYR2 and RYR3 that occurred after treatment with stromal cell-derived factor 1, macrophage-inflammatory protein-1alpha, or TGF-beta. Our results demonstrate expression of all three isoforms of RYR mRNA in hemopoietic cells. Induction of RYRs in response to chemokines and TGF-beta suggests roles in regulating Ca(2+)-mediated cellular responses during the immune response.
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PMID:Expression of the ryanodine receptor isoforms in immune cells. 1167 93

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

Ca(2+) signaling plays an important role in the function of dendritic cells (DC), the specialized antigen-presenting cells of the immune system. Here we describe functional ryanodine receptor (RyR) Ca(2+) release channels in murine, bone marrow-derived DC. RT-PCR analysis identified selective expression of the type 1 RyR, with higher levels detected in immature rather than mature DC. The RyR activators caffeine, FK506, ryanodine and 4-chloro-m-cresol mobilized Ca(2+) in DC, and responses to 4-chloro-m-cresol were inhibited by dantrolene. Furthermore, activation of RyRs both inhibited subsequent inositol trisphosphate-mediated Ca(2+) release and provoked store-operated Ca(2+) entry, suggesting a functional interaction between these intracellular Ca(2+) channels. Thus, the RyR1 channel may play an intrinsic role in Ca(2+) signaling in DC.
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PMID:Identification of functional type 1 ryanodine receptors in mouse dendritic cells. 1185 53

Calmodulin is a ubiquitous Ca(2+) binding protein that modulates the in vitro activity of the skeletal muscle ryanodine receptor (RyR1). Residues 3614-3643 of RyR1 comprise the CaM binding domain and mutations within this region result in a loss of both high-affinity Ca(2+)-bound calmodulin (CaCaM) and Ca(2+)-free CaM (apoCaM) binding (L3624D) or only CaCaM binding (W3620A). To investigate the functional role of CaM binding to this region of RyR1 in intact skeletal muscle, we compared the ability of RyR1, L3624D, and W3620A to restore excitation-contraction (EC) coupling after expression in RyR1-deficient (dyspedic) myotubes. W3620A-expressing cells responded normally to 10 mM caffeine and 500 microM 4-chloro-m-cresol (4-cmc). Interestingly, L3624D-expressing cells displayed a bimodal response to caffeine, with a large proportion of cells ( approximately 44%) showing a greatly attenuated response to caffeine. However, high and low caffeine-responsive L3624D-expressing myotubes exhibited Ca(2+) transients of similar magnitude after activation by 4-cmc (500 microM) and electrical stimulation. Expression of either L3624D or W3620A in dyspedic myotubes restored both L-type Ca(2+) currents (retrograde coupling) and voltage-gated SR Ca(2+) release (orthograde coupling) to a similar degree as that observed for wild-type RyR1, although L-current density was somewhat larger and activated at more hyperpolarized potentials in W3620A-expressing myotubes. The results indicate that CaM binding to the 3614-3643 region of RyR1 is not essential for voltage sensor activation of RyR1.
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PMID:Calmodulin binding to the 3614-3643 region of RyR1 is not essential for excitation-contraction coupling in skeletal myotubes. 1219 90

Malignant hyperthermia (MH) is an autosomal-dominant disorder of skeletal muscle, triggered by volatile anaesthetics and depolarizing muscle relaxants. The causative defect lies in the control of Ca(2+) release from the sarcoplasmic reticulum in skeletal muscle. Numerous mutations have been detected in the ryanodine receptor 1 (RyR1) gene, but so far an MH-causative role has only been confirmed for 16 human RyR1 mutations. In this report we show that myotubes derived from individuals carrying the RyR1 Thr2206Met (C6617T) mutation have an abnormal response of the intracellular calcium concentration to 4-chloro-m-cresol and to caffeine. Satellite cells were obtained from muscle biopsies of patients referred for diagnosing MH. The intracellular calcium concentration in response to 4-chloro-m-cresol and to caffeine was investigated by fluorescence calcium imaging. In myotubes the half-maximal activation concentration (EC(50)) for 4-chloro-m-cresol was reduced from 203 micro m (wild type) to 98 micro m (Thr2206Met), and for caffeine from 3.8 mm to 1.8 mm. From the reduction of EC(50) we conclude that the RyR1 Thr2206Met mutation is pathogenic for MH.
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PMID:Increased sensitivity to 4-chloro-m-cresol and caffeine in primary myotubes from malignant hyperthermia susceptible individuals carrying the ryanodine receptor 1 Thr2206Met (C6617T) mutation. 1222 Apr 51

Patients with myasthenia gravis can have antibodies against skeletal muscle ryanodine receptor (Ry1), the sarcoplasmic reticulum calcium-release channel, which plays a crucial role in excitation-contraction coupling. We have screened a panel of overlapping Ry1 fusion proteins with Ry1 antibody-containing myasthenia gravis sera to identify the main immunogenic region. The pc2 Ry1 fusion protein representing a Ry1 region close to the N-terminus (residues 799-1172) was identified as the main immunogenic region for the antibodies. The binding kinetics of the Ry1 antibodies to the pc2 Ry1 fusion protein were tested using an optical biosensor. Ry1 antibodies in the IgG fraction from sera of patients with myasthenia gravis bound with high affinity and with a stoichiometry of 1:1. The functional effect of these Ry1 antibodies was tested in an in vitro Ca2+-release assay. The Ry1 antibodies induced a twofold increase of the half-maximal concentration for 4-Cl-m-cresol-induced Ca2+ release from terminal cisternae vesicles but had no effect on V(max). The effect on 4-Cl-m-cresol-induced Ca2+ release was specific, as preincubation of the active IgG fraction with the pc2 Ry1 fusion protein abolished the inhibition. These data suggest that the Ry1 sequence defined by residues 799-1172 is involved in the regulation of Ry1 function, and that this regulation could be functionally affected in vivo in patients with myasthenia gravis.
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PMID:Ryanodine receptor antibodies in myasthenia gravis: epitope mapping and effect on calcium release in vitro. 1250 99


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