ITPR3

Inositol 1,4,5-trisphosphate-gated calcium channel that, upon 1D-myo-inositol 1,4,5-trisphosphate binding, transports calcium from the endoplasmic reticulum lumen to cytoplasm, thus releasing the intracellular calcium and therefore participates in cellular calcium ion homeostasis (PubMed:32949214, PubMed:37898605, PubMed:8081734, PubMed:8288584). 1D-myo-inositol 1,4,5-trisphosphate binds to the ligand-free channel without altering its global conformation, yielding the low-energy resting state, then progresses through resting-to preactivated transitions to the higher energy preactivated state, which increases affinity for calcium, promoting binding of the low basal cytosolic calcium at the juxtamembrane domain (JD) site, favoring the transition through the ensemble of high-energy intermediate states along the trajectory to the fully-open activated state (PubMed:30013099, PubMed:35301323, PubMed:37898605). Upon opening, releases calcium in the cytosol where it can bind to the low-affinity cytoplasmic domain (CD) site and stabilizes the inhibited state to terminate calcium release (PubMed:30013099, PubMed:35301323, PubMed:37898605).