Triadin: Proteins and Enzymes

The junction between the transverse tubules (T-tubules) and the sarcoplasmic reticulum (SR) of skeletal muscle is called the triad. At the triad, dihydropyridine receptors (DHPR®s) of the T-tubule serve as voltage sensors in excitation-contraction coupling, while ryanodine receptors (RyR®s), the calcium release channels, exist in the membrane of the terminal cisternae of the SR. It is thought that during slow phase depolarization of the T-tubule, a third protein, Triadin (MW 95 kDa) transmits electrochemical signals to the SR through direct interaction with both DHPR®s and RyR®s. Though its exact role in this signaling process is unclear, triadin has been shown to co-localize with both DHPR and RYR at the junctional face of the terminal cisternae.