a multi-pass endoplasmic reticulum membrane receptor for inositol 1,4,5-trisphosphate, a second messenger that mediates the release of intracellular calcium. Plays a role in ER stress-induced apoptosis. Cytoplasmic calcium released from the ER triggers apoptosis by the activation of CaMKII, eventually leading to the activation of downstream apoptosis pathways. Part of a cGMP kinase signaling complex that includes alpha-actin, calponin H1, phospholamban, PKG1 and IP3R1. Widely expressed. The receptor contains a calcium channel in its C-terminal extremity. Its large N-terminal cytoplasmic region has the ligand-binding site in the N-terminus and modulatory sites in the middle portion immediately upstream of the channel region. Phosphorylation by PKA prevents the ligand-induced opening of the calcium channels. Belongs to the ryanodine-inositol 1,4,5-triphosphate receptor ca(2+) channel (rir-cac) family. Eight alternatively spliced isoforms have been described. Note: This description may include information from UniProtKB.
Molecular Function: calcium channel inhibitor activity; calcium ion binding; calcium ion transmembrane transporter activity; calcium-release channel activity; inositol 1,4,5-triphosphate-sensitive calcium-release channel activity; phosphoinositide binding; protein binding
Biological Process: negative regulation of calcium-mediated signaling; platelet activation; regulation of autophagy; regulation of insulin secretion; release of sequestered calcium ion into cytosol; response to hypoxia