Structure and Function of Inositol 1, 4, 5-Trisphosphate Receptor

Abstract

Generation of intracellular Ca²⁺ signals in response to Ca²⁺ -mobilizing stimuli is a critical event in the control of many cellular processes. Inositol 1, 4, 5-trisphosphate (IP₃)represents a dominant second messenger subserving the release of Ca²⁺ from intracellular store sites. The protein on the surface of which the IP₃ receptor is located comprises an IP₃-gated Ca²⁺ channel, and binding of IP₃ to this receptor triggers the release of Ca²⁺ through this channel. The receptor for IP₃ displays a close resemblance to the ryanodine receptor, another intracellular Ca²⁺ channel, in many molecular and physiological properties. Many lines of evidence strongly suggest the central role that the IP3 receptor plays in the conversion of numerous external stimuli to intracellular Ca²⁺ signals characterized by complex spatiotemporal patterns such as Ca²⁺ waves and oscillations. In this review, we shall summarize our current knowledge of the structure and function of the IP₃ receptor in order to understand the way how the activity of this important receptor is regulated to accomodate itself to the generation of diverse intracellular Ca²⁺ signals.