Binds specifically to phosphatidylinositol 3,4-diphosphate (PtdIns3,4P2), but not to other phosphoinositides. May recruit other proteins to the plasma membrane (By similarity). Binds MPDZ and PTPN13. Locates to the plasma membrane after treatments that stimulate the production of PtdIns3,4P2. Highly expressed in heart, kidney, spleen and peripheral blood leukocytes. Detected at lower levels in brain, skeletal muscle, colon, thymus, liver, small intestine, placenta and lung.