Junctophilins: molecular components contributing junctional membrane complexes between the cell-surface membrane and endoplasmic/sarcoplasmic reticulum

The junctional membrane complex between the plasma membrane (PM) and endoplasmic/sarcoplasmic reticulum (ER/SR) is an important structural foundation for functional crosstalk between ionic channels. In cardiac myocytes, functional coupling between cell-surface and intracellular Ca(2+) channels produces Ca(2+) transients for contraction. Junctophilins, a novel family of junctional membrane complex proteins, contribute to the stabilization of the junctional membrane complex by anchoring the ER/SR and interacting with the PM. Mutant mice lacking the cardiac-type junctophilin exhibited embryonic lethality due to heart failure, and the mutant cardiac myocytes showed deficiency of the junctional membrane complexes and abnormal Ca(2+) signaling.