ITPR3 encodes a receptor for inositol 1,4,5-trisphosphate, a second messenger that mediates the release of intracellular calcium. The receptor contains a calcium channel at the C-terminus and the ligand-binding site at the N-terminus. Knockout studies in mice suggest that type 2 and type 3 inositol 1,4,5-trisphosphate receptors play a key role in exocrine secretion underlying energy metabolism and growth. ITP3 channels serve an important role in the taste transduction pathway of sweet, bitter and umami tastes the gustatory system. ITP3 channels allow the flow of Calcium out of the endoplasmic reticulum in response to IP3. Calcium cations result in the activation of TRPM5 which leads to a depolarisation generating potential and an action potential.