Ins(1)P1 is a member of the inositol phosphate (InsP) molecular family of second messengers that play a critical role in the transmission of cellular signals.{8344,8672} The most studied InsP, Ins(1,4,5)P3, is a second messenger produced in cells by PLC-mediated hydrolysis of phosphatidylinositol-4,5-biphosphate.{2429,5714} Binding of Ins(1,4,5)P3 to its receptor on the endoplasmic reticulum results in opening of the calcium channels and an increase in intracellular calcium.{5714,4096} Ins(1)P1 can be formed by PLC hydrolysis of phosphatidylinositol or by dephosphorylation of polyphosphate inositols such as Ins(1,3)P2 by inositol polyphosphate 3-phosphatase.{8344}