Myotubularin-related protein 9

Acts as an adapter for myotubularin-related phosphatases. Increases lipid phosphatase MTMR6 catalytic activity, specifically towards phosphatidylinositol 3,5-bisphosphate and MTMR6 binding affinity for phosphorylated phosphatidylinositols. Positively regulates lipid phosphatase MTMR7 catalytic activity (By similarity). Increases MTMR8 catalytic activity towards phosphatidylinositol 3-phosphate. The formation of the MTMR6-MTMR9 complex, stabilizes both MTMR6 and MTMR9 protein levels. Stabilizes MTMR8 protein levels. Plays a role in the late stages of macropinocytosis possibly by regulating MTMR6-mediated dephosphorylation of phosphatidylinositol 3-phosphate in membrane ruffles. Negatively regulates autophagy, in part via its association with MTMR8. Negatively regulates DNA damage-induced apoptosis, in part via its association with MTMR6. Does not bind mono-, di- and tri-phosphorylated phosphatidylinositols, phosphatidic acid and phosphatidylserine.