Phosphatidylinositol Trisphosphate (PIP3)

Phosphatidylinositol (3,4,5)-trisphosphate is the product of the class I phosphoinositide 3-kinases (PI 3-kinases) phosphorylation on phosphatidylinositol (4,5)-bisphosphate (PIP₂). PIP₃ functions to activate downstream signaling components, most notably the protein kinase AKT, which activates downstream anabolic signaling pathways required for cell growth and survival.PtdIns(3,4,5)P₃ is dephophosphorylated by the phosphatase, PTEN on the 3 position, generating PI(4,5)P₂, and by SHIPs (SH2-containing inositol phosphatase) on the 5' position of the inositol ring, producing PI(3,4)P₂.

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.