8.A.110. The Junctophilin (JP) Family
Junctophilins contribute to the formation of junctional membrane complexes (JMCs) which link the plasma membrane with the endoplasmic or sarcoplasmic reticulum in excitable cells. They provide a structural foundation for functional cross-talk between the cell surface and intracellular calcium release channels. JPH1 contributes to the construction of the skeletal muscle triad by linking the t-tubule (transverse-tubule) and SR (sarcoplasmic reticulum) membranes.
Close physical association of CaV1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling (ECC) in skeletal muscle (Nakada et al. 2018). Junctophilin 1 (JP1) and JP2 stabilize the JM by bridging the sarcolemmal and SR membranes. JPs recruit LTCCs to the JM through physical interaction and ensure robust ECC at triads in skeletal muscle (Barone et al. 2015).