Ryanodine receptor

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RyR domain
Identifiers
SymbolRyR
PfamPF02026
InterProIPR003032
TCDB1.A.3
 
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RyR domain
Identifiers
SymbolRyR
PfamPF02026
InterProIPR003032
TCDB1.A.3

Ryanodine receptors (RyRs) form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons. It is the major cellular mediator of calcium-induced calcium release (CICR) in animal cells.

Etymology[edit]

Ryanodine

The ryanodine receptors are named after the plant alkaloid ryanodine, to which they show high affinity:

Isoforms[edit]

There are multiple isoforms of ryanodine receptors:

ryanodine receptor 1 (skeletal)
Identifiers
SymbolRYR1
Alt. symbolsMHS, MHS1, CCO
Entrez6261
HUGO10483
OMIM180901
RefSeqNM_000540
UniProtP21817
Other data
LocusChr. 19 q13.1
ryanodine receptor 2 (cardiac)
Identifiers
SymbolRYR2
Entrez6262
HUGO10484
OMIM180902
RefSeqNM_001035
UniProtQ92736
Other data
LocusChr. 1 q42.1-q43
ryanodine receptor 3
Identifiers
SymbolRYR3
Entrez6263
HUGO10485
OMIM180903
RefSeqNM_001036
UniProtQ15413
Other data
LocusChr. 15 q14-q15

Physiology[edit]

Ryanodine receptors mediate the release of calcium ions from the sarcoplasmic reticulum, an essential step in muscle contraction. In skeletal muscle, it is thought that activation occurs via a physical coupling to the dihydropyridine receptor, whereas, in cardiac muscle, the primary mechanism is calcium-induced calcium release from the sarcoplasmic reticulum.[2]

It has been shown that calcium release from a number of ryanodine receptors in a ryanodine receptor cluster results in a spatiotemporally restricted rise in cytosolic calcium that can be visualised as a calcium spark.[3] Ryanodine receptors are very close to mitochondria and calcium release from RyR has been shown to regulate ATP production in heart and pancreas cells.[4][5][6]

Ryanodine receptors are similar to the inositol trisphosphate (IP3) receptor, and stimulated to transport Ca2+ into the cytosol by recognizing Ca2+ on its cytosolic side, thus establishing a positive feedback mechanism; a small amount of Ca2+ in the cytosol near the receptor will cause it to release even more Ca2+ (calcium-induced calcium release/CICR).[1]

RyRs are especially important in neurons and muscle cells. In heart and pancreas cells, another second messenger (cyclic ADP-ribose) takes part in the receptor activation.

The localized and time-limited activity of Ca2+ in the cytosol is also called a Ca2+ wave. The building of the wave is done by

Associated proteins[edit]

RyRs form docking platforms for a multitude of proteins and small molecule ligands. The cardiac-specific isoform of the receptor (RyR2) is known to form a quaternary complex with luminal calsequestrin, junctin, and triadin.[7] Calsequestrin has multiple Ca2+ binding sites and binds Ca2+ ions with very low affinity so they can be easily released.



Pharmacology[edit]

A variety of other molecules may interact with and regulate ryanodine receptor. For example: dimerized Homer physical tether linking inositol trisphosphate receptors (IP3R) and ryanodine receptors on the intracellular calcium stores with cell surface group 1 metabotropic glutamate receptors and the Alpha-1D adrenergic receptor[11]

Ryanodine[edit]

The plant alkaloid ryanodine, for which this receptor was named, has become an invaluable investigative tool. It can block the phasic release of calcium, but at low doses may not block the tonic cumulative calcium release. The binding of ryanodine to RyRs is use-dependent, that is the channels have to be in the activated state. At low (<10 MicroMolar, works even at nanomolar) concentrations, ryanodine binding locks the RyRs into a long-lived subconductance (half-open) state and eventually depletes the store, while higher (~100 MicroMolar) concentrations irreversibly inhibit channel-opening.

Caffeine[edit]

RyRs are activated by millimolar caffeine concentrations. High (greater than 5 mmol/L) caffeine concentrations cause a pronounced increase (from micromolar to picomolar) in the sensitivity of RyRs to Ca2+ in the presence of caffeine, such that basal Ca2+ concentrations become activatory. At low millimolar caffeine concentrations, the receptor opens in a quantal way, but has complicated behavior in terms of repeated use of caffeine or dependence on cytosolic or luminal calcium concentrations.

Role in disease[edit]

RyR1 mutations are associated with malignant hyperthermia and central core disease. RyR2 mutations play a role in stress-induced polymorphic ventricular tachycardia (a form of cardiac arrhythmia) and ARVD.[1] It has also been shown that levels of type RyR3 are greatly increased in PC12 cells overexpressing mutant human Presenilin 1, and in brain tissue in knockin mice that express mutant Presenilin 1 at normal levels,[citation needed] and thus may play a role in the pathogenesis of neurodegenerative diseases, like Alzheimer's disease.[citation needed]

The presence of antibodies against ryanodine receptors in blood serum has also been associated with myasthenia gravis.[citation needed]

See also[edit]

References[edit]

  1. ^ a b c Zucchi R, Ronca-Testoni S (March 1997). "The sarcoplasmic reticulum Ca2+ channel/ryanodine receptor: modulation by endogenous effectors, drugs and disease states". Pharmacol. Rev. 49 (1): 1–51. PMID 9085308. 
  2. ^ Fabiato A (1983). "Calcium-induced calcium release of calcium from the cardiac sarcoplasmic reticulum". Am J Physiol 245 (1): C1–C14. PMID 6346892. 
  3. ^ Cheng H, Lederer WJ, Cannell MB (1993). "Calcium sparks: elementary events underlying excitation-contraction coupling in heart muscle". Science 262 (5134): 740–744. doi:10.1126/science.8235594. PMID 8235594. 
  4. ^ Bround MJ, Wambolt R, Luciani DS, Kulpa JE, Rodrigues B, Brownsey RW, Allard MF, Johnson JD (May 2013). "Cardiomyocyte ATP production, metabolic flexibility, and survival require calcium flux through cardiac ryanodine receptors in vivo". J. Biol. Chem. 288 (26): 18975–86. doi:10.1074/jbc.M112.427062. PMID 23678000. 
  5. ^ Tsuboi T, da Silva Xavier G, Holz GG, Jouaville LS, Thomas AP, Rutter GA (January 2003). "Glucagon-like peptide-1 mobilizes intracellular Ca2+ and stimulates mitochondrial ATP synthesis in pancreatic MIN6 beta-cells". Biochem. J. 369 (Pt 2): 287–99. doi:10.1042/BJ20021288. PMC 1223096. PMID 12410638. 
  6. ^ Dror V, Kalynyak TB, Bychkivska Y, Frey MH, Tee M, Jeffrey KD, Nguyen V, Luciani DS, Johnson JD (April 2008). "Glucose and endoplasmic reticulum calcium channels regulate HIF-1beta via presenilin in pancreatic beta-cells". J. Biol. Chem. 283 (15): 9909–16. doi:10.1074/jbc.M710601200. PMID 18174159. 
  7. ^ Kranias, Evangelia. "Dr. Evangelia Kranias Lab: Calsequestrin". Retrieved 22 May 2014. 
  8. ^ Vites A, Pappano A (1994). "Distinct modes of inhibition by ruthenium red and ryanodine of calcium-induced calcium release in avian atrium". J Pharmacol Exp Ther 268 (3): 1476–84. PMID 7511166. 
  9. ^ Xu L, Tripathy A, Pasek D, Meissner G (1998). "Potential for pharmacology of ryanodine receptor/calcium release channels". Ann N Y Acad Sci 853: 130–48. doi:10.1111/j.1749-6632.1998.tb08262.x. PMID 10603942. 
  10. ^ Wang Y, Zheng Y, Mei Q, Wang Q, Collier M, Fleischer S, Xin H, Kotlikoff M (2004). "FKBP12.6 and cADPR regulation of Ca2+ release in smooth muscle cells". Am J Physiol Cell Physiol 286 (3): C538–46. doi:10.1152/ajpcell.00106.2003. PMID 14592808. 
  11. ^ Tu J, Xiao B, Yuan J, Lanahan A, Leoffert K, Li M, Linden D, Worley P (1998). "Homer binds a novel proline-rich motif and links group 1 metabotropic glutamate receptors with IP3 receptors". Neuron 21 (4): 717–26. doi:10.1016/S0896-6273(00)80589-9. PMID 9808459. 

External links[edit]