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)

2001 ◽  
Vol 360 (1) ◽  
pp. 97-105 ◽  
Author(s):  
Guo Guang DU ◽  
Hideto OYAMADA ◽  
Vijay K. KHANNA ◽  
David H. MacLENNAN
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Malignant Hyperthermia ◽  
Ryanodine Receptor ◽  
Atp Binding ◽  
Regulatory Domain ◽  
Wild Type ◽  
Release Channel ◽  
Binding Motifs ◽  
Channel Opening

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 Ca2+-release channel of skeletal-muscle sarcoplasmic reticulum (ryanodine receptor or RyR1). Activation of [3H]ryanodine binding by Ca2+, caffeine and ATP (adenosine 5′-[β,γ-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 Ca2+ release in HEK-293 cells expressing wild-type and mutant channels. Equilibrium [3H]ryanodine-binding properties and EC50 values for Ca2+ activation of high-affinity [3H]ryanodine binding were similar between wild-type RyR1 and mutants. In the presence of 1mM AMP-PCP, Ca2+-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.

Site-specific modification of calmodulin Ca2+ affinity tunes the skeletal muscle ryanodine receptor activation profile

2010 ◽  
Vol 432 (1) ◽  
pp. 89-99 ◽  
Author(s):  
Jie Jiang ◽  
Yubin Zhou ◽  
Jin Zou ◽  
Yanyi Chen ◽  
Priya Patel ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Binding Affinity ◽  
Ryanodine Receptor ◽  
Receptor Activation ◽  
Release Channel ◽  
Domain Specific ◽  
Terminal Domain ◽  
Channel Opening ◽  
Activation Profile ◽  
Ef Hands

The skeletal muscle isoform of the ryanodine receptor Ca2+-release channel (RyR1) is regulated by Ca2+ and CaM (calmodulin). CaM shifts the biphasic Ca2+-dependence of RyR1 activation leftward, effectively increasing channel opening at low Ca2+ and decreasing channel opening at high Ca2+. The conversion of CaM from a RyR1 activator into an inhibitor is due to the binding of Ca2+ to CaM; however, which of CaM's four Ca2+-binding sites serves as the switch for this conversion is unclear. We engineered a series of mutant CaMs designed to individually increase the Ca2+ affinity of each of CaM's EF-hands by increasing the number of acidic residues in Ca2+-chelating positions. Domain-specific Ca2+ affinities of each CaM variant were determined by equilibrium fluorescence titration. Mutations in sites I (T26D) or II (N60D) in CaM's N-terminal domain had little effect on CaM Ca2+ affinity and regulation of RyR1. However, the site III mutation N97D increased the Ca2+-binding affinity of CaM's C-terminal domain and caused CaM to inhibit RyR1 at a lower Ca2+ concentration than wild-type CaM. Conversely, the site IV mutation Q135D decreased the Ca2+-binding affinity of CaM's C-terminal domain and caused CaM to inhibit RyR1 at higher Ca2+ concentrations. These results support the hypothesis that Ca2+ binding to CaM's C-terminal acts as the switch converting CaM from a RyR1 activator into a channel inhibitor. These results indicate further that targeting CaM's Ca2+ affinity may be a valid strategy to tune the activation profile of CaM-regulated ion channels.

scholarly journals Malignant hyperthermia-associated mutations in the S2-S3 cytoplasmic loop of type 1 ryanodine receptor calcium channel impair calcium-dependent inactivation

2016 ◽  
Vol 311 (5) ◽  
pp. C749-C757 ◽  
Author(s):  
Angela C. Gomez ◽  
Timothy W. Holford ◽  
Naohiro Yamaguchi
Keyword(s):  
Skeletal Muscle ◽  
Malignant Hyperthermia ◽  
Ryanodine Receptor ◽  
Wild Type ◽  
Cytoplasmic Loop ◽  
Muscle Diseases ◽  
Calcium Dependent ◽  
Transmembrane Segments ◽  
Channel Regulation ◽  
Dependent Inactivation

Channel activities of skeletal muscle ryanodine receptor (RyR1) are activated by micromolar Ca2+ and inactivated by higher (∼1 mM) Ca2+. To gain insight into a mechanism underlying Ca2+-dependent inactivation of RyR1 and its relationship with skeletal muscle diseases, we constructed nine recombinant RyR1 mutants carrying malignant hyperthermia or centronuclear myopathy-associated mutations and determined RyR1 channel activities by [3H]ryanodine binding assay. These mutations are localized in or near the RyR1 domains which are responsible for Ca2+-dependent inactivation of RyR1. Four RyR1 mutations (F4732D, G4733E, R4736W, and R4736Q) in the cytoplasmic loop between the S2 and S3 transmembrane segments (S2–S3 loop) greatly reduced Ca2+-dependent channel inactivation. Activities of these mutant channels were suppressed at 10–100 μM Ca2+, and the suppressions were relieved by 1 mM Mg2+. The Ca2+- and Mg2+-dependent regulation of S2–S3 loop RyR1 mutants are similar to those of the cardiac isoform of RyR (RyR2) rather than wild-type RyR1. Two mutations (T4825I and H4832Y) in the S4–S5 cytoplasmic loop increased Ca2+ affinities for channel activation and decreased Ca2+ affinities for inactivation, but impairment of Ca2+-dependent inactivation was not as prominent as those of S2–S3 loop mutants. Three mutations (T4082M, S4113L, and N4120Y) in the EF-hand domain showed essentially the same Ca2+-dependent channel regulation as that of wild-type RyR1. The results suggest that nine RyR1 mutants associated with skeletal muscle diseases were differently regulated by Ca2+ and Mg2+. Four malignant hyperthermia-associated RyR1 mutations in the S2–S3 loop conferred RyR2-type Ca2+- and Mg2+-dependent channel regulation.

scholarly journals Increased sensitivity of the ryanodine receptor to halothane-induced oligomerization in malignant hyperthermia-susceptible human skeletal muscle

2004 ◽  
Vol 96 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Louise Glover ◽  
James J. A. Heffron ◽  
Kay Ohlendieck
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Malignant Hyperthermia ◽  
Ryanodine Receptor ◽  
Human Skeletal Muscle ◽  
Dihydropyridine Receptor ◽  
Threshold Concentration ◽  
Release Channel ◽  
Functional Dynamics ◽  
Increased Sensitivity

Mutations in the skeletal muscle RyR1 isoform of the ryanodine receptor (RyR) Ca2+-release channel confer susceptibility to malignant hyperthermia, which may be triggered by inhalational anesthetics such as halothane. Using immunoblotting, we show here that the ryanodine receptor, calmodulin, junctin, calsequestrin, sarcalumenin, calreticulin, annexin-VI, sarco(endo)plasmic reticulum Ca2+-ATPase, and the dihydropyridine receptor exhibit no major changes in their expression level between normal human skeletal muscle and biopsies from individuals susceptible to malignant hyperthermia. In contrast, protein gel-shift studies with halothane-treated sarcoplasmic reticulum vesicles from normal and susceptible specimens showed a clear difference. Although the α2-dihydropyridine receptor and calsequestrin were not affected, clustering of the Ca2+-ATPase was induced at comparable halothane concentrations. In the concentration range of 0.014–0.35 mM halothane, anesthetic-induced oligomerization of the RyR1 complex was observed at a lower threshold concentration in the sarcoplasmic reticulum from patients with malignant hyperthermia. Thus the previously described decreased Ca2+-loading ability of the sarcoplasmic reticulum from susceptible muscle fibers is probably not due to a modified expression of Ca2+-handling elements, but more likely a feature of altered quaternary receptor structure or modified functional dynamics within the Ca2+-regulatory apparatus. Possibly increased RyR1 complex formation, in conjunction with decreased Ca2+ uptake, is of central importance to the development of a metabolic crisis in malignant hyperthermia.

Reconstitution of abnormalities in the malignant hyperthermia-susceptible pig ryanodine receptor

1993 ◽  
Vol 264 (1) ◽  
pp. C125-C135 ◽  
Author(s):  
N. H. Shomer ◽  
C. F. Louis ◽  
M. Fill ◽  
L. A. Litterer ◽  
J. R. Mickelson
Keyword(s):  
Malignant Hyperthermia ◽  
Ryanodine Receptor ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Primary Defect ◽  
Open Probability ◽  
Release Channel ◽  
Malignant Hyperthermia Susceptible ◽  
Channel Opening ◽  
Kd Values

Malignant hyperthermia-susceptible (MHS) pigs homozygous for the Cys615 ryanodine receptor allele demonstrate altered sarcoplasmic reticulum (SR) ryanodine binding and Ca2+ release channel regulatory properties when compared with normal pigs homozygous for the Arg615 allele. While solubilized in 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, the purified MHS and normal ryanodine receptors had a similar dissociation constant (Kd) for ryanodine, maximum binding, and Ca2+ concentration for half-maximal stimulation and inhibition of ryanodine binding (Ca2+(0.5)); however, after reconstitution into proteoliposomes, the purified MHS and normal receptors had Kd values for ryanodine of 75 and 150 nM, respectively, which were significantly different. The purified MHS and normal porcine ryanodine receptors also had similar single-channel Cs+ conductance, optimal cis-Ca2+ for channel opening, and cis-Ca2+(0.5) for channel activation. Significantly, at inactivating levels of cis-Ca2+ (> 0.1 mM), MHS channels had a greater open probability, a higher cis-Ca2+(0.5) for inhibition of channel opening (250 vs. 75 microM for MHS and normal, respectively), longer mean open times, and shorter mean closed times than did normal channels. We conclude that the mutation at residue 615 causes a detectable alteration in ryanodine receptor/Ca2+ channel activity and thus may represent the primary defect responsible for the altered SR Ca2+ regulation characteristic of MHS porcine muscle.

Altered binding site for Ca2+ in the ryanodine receptor of human malignant hyperthermia

1991 ◽  
Vol 261 (2) ◽  
pp. C237-C245 ◽  
Author(s):  
H. H. Valdivia ◽  
K. Hogan ◽  
R. Coronado
Keyword(s):  
Skeletal Muscle ◽  
Malignant Hyperthermia ◽  
Binding Site ◽  
Ryanodine Receptor ◽  
Human Skeletal Muscle ◽  
Scatchard Analysis ◽  
Dependent Manner ◽  
Binding Properties ◽  
Release Channel ◽  
Planar Bilayers

The binding properties of [3H]ryanodine, a specific ligand of the receptor complex that forms the Ca2+ release channel of sarcoplasmic reticulum, were studied in normal (N) and malignant hyperthermia-susceptible (MH) human skeletal muscle. Integrity of the solubilized ryanodine receptor was demonstrated by single-channel recordings in planar bilayers and by the changes produced by activators and inhibitors of the Ca2+ release channel on the binding properties of [3H]ryanodine. N and MH receptors were capable of binding [3H]ryanodine in a Ca(2+)-dependent manner. Scatchard analysis showed that a single binding site for [3H]ryanodine was present in either N or MH muscle. Binding affinity was approximately the same in N and MH (Kd approximately 7 nM), when the Ca2+ concentration was greater than 30 microM. At 0.3 microM Ca2+, MH receptors displayed a higher affinity for [3H]ryanodine (Kd = 4.1 +/- 1.0 nM) than N receptors (Kd = 7.1 +/- 0.8 nM). The presence of a single Kd for [3H]ryanodine in MH muscle, distinct from that of N muscle, indicated that MH muscle does not have detectable levels of N receptors. Ca2+ dependence of [3H]ryanodine binding further suggested that MH receptors had a higher affinity for Ca2+ (Kd[Ca2+] = 120 +/- 50 nM) than N receptors (Kd[Ca2+] = 250 +/- 80 nM). Caffeine increased [3H]ryanodine binding at submicromolar [Ca2+], and the effect was larger in MH. Apparent affinity constants for caffeine were 13 +/- 1.8 mM in N and 6 +/- 0.8 mM in MH receptors. Evidently, the ryanodine receptor of MH-susceptible human skeletal muscle has an unusually high sensitivity to Ca2+ which is augmented by caffeine.(ABSTRACT TRUNCATED AT 250 WORDS)

Skeletal Muscle Ryanodine Receptor Mutations Associated with Malignant Hyperthermia Showed Enhanced Intensity and Sensitivity to Triggering Drugs when Expressed in Human Embryonic Kidney Cells

2013 ◽  
Vol 119 (1) ◽  
pp. 111-118 ◽  
Author(s):  
Keisaku Sato ◽  
Cornelia Roesl ◽  
Neil Pollock ◽  
Kathryn M. Stowell
Keyword(s):  
Skeletal Muscle ◽  
Malignant Hyperthermia ◽  
Calcium Channel ◽  
Ryanodine Receptor ◽  
Ex Vivo ◽  
Simian Virus 40 ◽  
T Antigen ◽  
Wild Type ◽  
Human Embryonic Kidney ◽  
Higher Sensitivity

Abstract Background: Mutations within the gene encoding the skeletal muscle calcium channel ryanodine receptor can result in malignant hyperthermia. Although it is important to characterize the functional effects of candidate mutations to establish a genetic test for diagnosis, ex vivo methods are limited because of the low incidence of the disorder and sample unavailability. More than 250 candidate mutations have been identified, but only a few mutations have been functionally characterized. Methods: The human skeletal muscle ryanodine receptor complementary DNA was cloned with or without a disease-related variant. Wild-type and mutant calcium channel proteins were transiently expressed in human embryonic kidney-293 cells expressing the large T-antigen of simian virus 40, and functional analysis was carried out using calcium imaging with fura-2 AM. Six human malignant hyperthermia-related mutants such as R44C, R163C, R401C, R533C, R533H, and H4833Y were analyzed. Cells were stimulated with a specific ryanodine receptor agonist 4-chloro-m-cresol, and intracellular calcium mobility was analyzed to determine the functional aspects of mutant channels. Results: Mutant proteins that contained a variant linked to malignant hyperthermia showed higher sensitivity to the agonist. Compared with the wild type (EC50 = 453.2 µm, n = 18), all six mutants showed a lower EC50 (21.2–170.4 µm, n = 12–23), indicating susceptibility against triggering agents. Conclusions: These six mutations cause functional abnormality of the calcium channel, leading to higher sensitivity to a specific agonist, and therefore could be considered potentially causative of malignant hyperthermia reactions.

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