Inositol Phosphates

Inositol phosphates are important intracellular second messengers in eukaryotic cells. Inositol, a cyclic molecule with six hydroxyl groups, forms the hydrophobic head group of membrane inositol phospholipids. The actions of lipid kinases and phosphatases on the inositol ring of inositol phospholipids generate a variety of phosphoinositol phospholipids. As a result of upstream signaling events, specific phospholipases are activated, cleave phosphoinositol phospholipids, and release intracellular inositol phosphate second messenger molecules. The most studied inositol phosphate second messenger is inositol 1,4,5-trisphosphate (IP₃). IP₃ is released from phosphatidylinositol 4,5-bisphosphate (PIP₂) by the action of phospholipase C-b and is responsible for the release of calcium ions from intracellular stores in the endoplasmic reticulum.

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References:

Irvine, R.F., and Schell, M.J., Back in the water: the return of inositol phosphates. Nat. Rev. Mol. Cell Biol., 2, 327-338 (2001).

Shears, S.B., Assessing the omnipotence of inositol hexakisphosphate. Cell. Signal., 13, 151-158 (2001).