Receptor for inositol 1,4,5-trisphosphate, a second messenger that mediates the release of intracellular calcium. Homotetramer. Interacts with TRPC1, TRPC3, TRPC4. Interacts with TRPV4 (By similarity). Interacts with SIGMAR1 (PubMed:11149946). Interacts with AKT1 and PML (PubMed:21030605). Interacts with IRAG2 (via coiled-coil domain) (PubMed:20071408). Interacts with CABP1 (By similarity). Interacts with TMBIM4/LFG4 (By similarity). Interacts with CEMIP (By similarity). Interacts with TESPA1 (PubMed:23650607). Interacts with TMEM203 (By similarity). Interacts with BOK; regulates ITPR3 expression (By similarity). Interacts with BCL2L10 (By similarity). 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. Phosphorylated on tyrosine residues (By similarity). Phosphorylated by AKT1 on serine and/or threonine residues. Belongs to the InsP3 receptor family.