Phosphatidylinositol 3,5-bisphosphate

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Phosphatidylinositol (3,5)-bisphosphate (PtdIns(3,5)P2 or PI(3,5)P2) is a minor phospholipid component of cell membranes, yet important in distinguishing cell compartments. The generation of PtdIns(3,5)P2 in intracellular membranes by the lipid kinase PIKfyve recruits a number of important proteins involved in regulating intracellular trafficking.

PtdIns(3,5)P2 is dephophosphorylated at the 5 position by the phosphatase FIG4, and by members of the myotubularin lipid phosphatase family at the 3 position of the inositol ring generating Phosphatidylinositol 5-phosphate (PtdIns5P).

The phosphoinositide-binding domain in a number of proteins binds to PtdIns(3,5)P2, including the PH domain in centaurin-β2, the PX domain of SNX1 , and a WD40 repeat domain in Atg18p.