Cellular regulation by soluble inositol phosphate messengers has yielded surprising knowledge that reaches well beyond the rigorously characterized regulation of Ca2+ release by inositol 1,4,5-trisphosphate (IP3), the best-known inositol phosphate. Inositol pyrophosphates belong to the diverse family of inositol polyphosphate species that have a range of signaling functions. The best-characterized ...