Enables GTPase activator activity. Involved in several processes, including regulation of actin filament polymerization; regulation of small GTPase mediated signal transduction; and small GTPase mediated signal transduction. Located in cytosol; nuclear speck; and plasma membrane. Part of cytoplasmic microtubule and ruffle. Implicated in schizophrenia. [provided by Alliance of Genome Resources, Apr 2022]