Subtype-Specific Regulation of Inositol 1,4,5-Trisphosphate Receptors: Controlling Calcium Signals in Time and Space

A rise in intracellular calcium ([Ca²⁺]_i) in response to binding of inositol 1,4,5 trisphosphate (InsP₃) to its receptors is a ubiquitous signaling system, which is implicated in the control of a myriad of cellular functions (Berridge 1993). Three distinct InsP₃ receptors are expressed to varying degrees in individual cell types (Wojcikiewicz 1995). Activation of these receptors results in [Ca²⁺]_i signals that display impressive fidelity, frequently manifested through a complex array of temporal and spatial characteristics. [Ca²⁺]_i signals in nonexcitable cells are initiated in defined regions (Kasai and Augustine 1990; Rooney et al. 1990); can be spatially limited to a portion of a cell (Kasai et al. 1993) or alternatively spread as repetitive, global, oscillatory waves throughout an...