Plays a role in immunological synaptic F-actin density and architecture organization. Regulates actin reorganization in lymphocytes, possibly through the modulation of Rac1 activity. Required for the formation of membrane ruffles during macropinocytosis. Plays a role in cell migration and is required for the formation of cup-like structures during trans-endothelial migration of leukocytes. Binds phospholipids in an activation-dependent manner; thereby acting as an anchor for other proteins to the plasma membrane (PM). Plays a role in exocytosis of cytotoxic granules (CG) by lymphocytes/Component of the exocytosis machinery in natural killer (NK) and CD8+ T cells. Promotes the docking of cytotoxic granules (CG) to the plasma membrane through the interaction with UNC13D. Involved in the cytotoxic activity of lymphocytes/primary CD8+ T cells.