Junctophilins contribute to the formation of junctional membrane complexes (JMCs) which link the plasma membrane with the endoplasmic or sarcoplasmic reticulum in excitable cells. Provides a structural foundation for functional cross-talk between the cell surface and intracellular calcium release channels. JPH3 is brain-specific and appears to have an active role in certain neurons involved in motor coordination and memory. Localized predominantly on the plasma membrane. The transmembrane domain is anchored in endoplasmic reticulum membrane, while the N-terminal part associates with the plasma membrane (By similarity). Additional isoforms seem to exist. Specifically expressed in brain. The MORN (membrane occupation and recognition nexus) repeats contribute to the plasma membrane binding, possibly by interacting with phospholipids. Isoform 2 length of the poly-Ala region is variable (6 to 27 CTG/CAG triplets) in the normal population and may be expanded (41 to 58 CTG/CAG triplets) in patients suffering from Huntington disease-like type 2. The disease is caused by variants affecting the gene represented in this entry. Belongs to the junctophilin family.