The CASQ2 gene encodes a calcium binding protein called calsequestrin 2 that stores calcium, which is vital for the functionality of muscles. This protein is found in the sarcoplasmic reticulum in cardiac and slow skeletal muscle cells. Within myocytes, the calsequestrin 2 protein acts as a storage center for calcium ions in the sarcoplasmic reticulum; most of these ions bind by clusters of acidic residues at the protein surface. The Calsequestrin 2 protein also regulates the release of lumenal Ca(2+) through the RYR2 channel; this plays an essential role in triggering muscle contractions including these involved in the heart rhythm. Defects in this protein have been associated with catecholaminergic polymorphic ventricular tachycardia type 2, a disease characterized by adrenergically induced ventricular tachycardia (VT) that may lead to sudden death due to cardiac arrest.