RYR2 and Arrhythmia: Last, the cardiac ryanodine receptor (RYR2) plays a key role in excitation-contraction coupling, whereby sarcoplasmic reticulum release of calcium through the RYR2 allows for calcium to interact with cytosolic contractile proteins, and both gain and loss of function RYR2 mutations can promote arrhythmias and sudden cardiac death (Gomez and Richard, 2004).