Structural basis for activation and gating of IP3 receptor calcium channels

Calcium (Ca2+) is a universal and versatile cellular messenger used to regulate numerous cellular processes in response to external or internal stimuli. A pivotal component of the Ca2+ signaling toolbox in cells is the inositol 1,4,5-triphosphate (IP3) receptors (IP3Rs). IP3Rs are intracellular Ca2+ channels, predominantly localized to the ER and activated by the binding of IP3 generated in response to external stimulation of G-protein coupled receptors. Opening of the IP3Rs results in the rapid release of Ca2+ from the ER into the cytoplasm triggering diverse signaling cascades to regulate physiological processes such as learning, fertilization, gene expression, and apoptosis.