Ryanodine receptor

Ryanodine receptors (RyRs) form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons. There are three major isoforms of the ryanodine receptor, which are found in different tissues and participate in different signaling pathways involving calcium release from intracellular organelles. The RYR2 ryanodine receptor isoform is the major cellular mediator of calcium-induced calcium release (CICR) in animal cells.

Etymology

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

Isoforms

There are multiple isoforms of ryanodine receptors:

RyR1 is primarily expressed in skeletal muscle

RyR2 is primarily expressed in myocardium (heart muscle)

RyR3 is expressed more widely, but especially in the brain.

Non-mammalian vertebrates typically express two RyR isoforms, referred to as RyR-alpha and RyR-beta.

Many invertebrates, including the model organisms Drosophila melanogaster (fruitfly) and Caenorhabditis elegans only have a single isoform. In non-metazoan species, calcium-release channels with sequence homology to RyRs can be found, but they are shorter than the mammalian ones and may be closer to IP3 Receptors.

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RYR1

Ryanodine receptor 1 (RYR-1) also known as skeletal muscle calcium release channel or skeletal muscle-type ryanodine receptor is a protein found primarily in skeletal muscle. In humans, it is encoded by the RYR1 gene.

Function

RYR1 functions as a calcium release channel in the sarcoplasmic reticulum, as well as a connection between the sarcoplasmic reticulum and the transverse tubule.

Clinical significance

Mutations in the RYR1 gene are associated with malignant hyperthermia susceptibility, central core disease, minicore myopathy with external ophthalmoplegia and samaritan myopathy, a benign congenital myopathy. Alternatively spliced transcripts encoding different isoforms have been demonstrated.Dantrolene may be the only known drug that is effective during cases of malignant hyperthermia.