Contributes to the stabilization of the junctional membrane complexes, which are common to excitable cells and mediate cross-talk between cell surface and intracellular ion channels. Probably acts by anchoring the plasma membrane and endoplasmic/sarcoplasmic reticulum. Contributes to the construction of skeletal muscle triad junctions, and plays an essential role in heart development.

Specifically expressed in skeletal muscle and heart.

Defects in JPH2 are the cause of cardiomyopathy familial hypertrophic type 17 (CMH17) [MIM:613873]. CMH17 is a hereditary heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death.

Belongs to the junctophilin family.
Contains 8 MORN repeats.

The MORN (membrane occupation and recognition nexus) repeats contribute to the plasma membrane binding, possibly by interacting with phospholipids.

Cell membrane. Endoplasmic reticulum membrane. Sarcoplasmic reticulum membrane. Localized predominantly on the plasma membrane. The transmembrane domain is anchored in endoplasmic/sarcoplasmic reticulum membrane, while the N-terminal part associates with the plasma membrane. In heart cells, it predominantly associates along Z lines within myocytes. In skeletal muscle, it is specifically localized at the junction of A and I bands.