Receptor for inositol 1,4,5-trisphosphate, a second messenger that mediates the release of intracellular calcium. This release is regulated by cAMP both dependently and independently of PKA (By similarity). Homotetramer (By similarity). Interacts with CABP1 (PubMed:12032348). Interacts with BOK; regulates ITPR2 expression (By similarity). Interacts with BCL2L10 (PubMed:27995898). Interacts with TRPC4 (By similarity). Isoform Short is found in skeletal muscle and heart. 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 cAMP-dependent PKA on Ser-937 increases calcium release. The disease is caused by variants affecting the gene represented in this entry. Calcium appears to inhibit ligand binding to the receptor, most probably by interacting with a distinct calcium-binding protein which then inhibits the receptor. Belongs to the InsP3 receptor family.