Actin-binding adapter protein. May act as a common effector of antigen receptor-signaling pathways in leukocytes. Its association with dynamin suggests that it may also connect the actin cytoskeleton to endocytic function. Acts as a key component of the immunological synapse that regulates T-cell activation by bridging TCRs and the actin cytoskeleton to gene activation and endocytic processes. Binds to F-actin but is not involved in actin polymerization, capping or bundling. Does not bind G-actin.