Chemical structure of sn-1-stearoyl-2-arachidonoyl phosphatidylinositol 3,4,5-trisphosphate

Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P₃) commonly abbreviated to PIP₃ is the product of the class I phosphoinositide 3-kinases (PI 3-kinases) activity on phosphatidylinositol (4,5)-bisphosphate.

PtdIns(3,4,5)P₃ is dephophosphorylated by the phosphatase, PTEN on the 3 position and by SHIPs (SH2-containing inositol phosphatase) on the 5' position of the inositol ring.

The PH domain in a number of proteins binds to PtdIns(3,4,5)P₃. Such proteins include Akt/PKB, PDK1, Btk1 and ARNO. The generation of PtdIns(3,4,5)P₃ at the plasma membrane upon the activation of class I PI 3-kinases causes these proteins to translocate to the plasma membrane and accordingly affects their activity.

The PH domain allows binding between PtdIns(3,4,5)P₃ and G-protein coupled receptor kinases (GRKs). This enhances the binding of the GRK to the plasma membrane.

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