Functions as a GTPase-activating protein for the small GTPases RHOA, RHOB, RHOC and CDC42, terminating their downstream signaling. This induces morphological changes and detachment through cytoskeletal reorganization, playing a critical role in biological processes such as cell migration and proliferation. Also functions in vivo as an activator of the phospholipase PLCD1. Active DLC1 increases cell migration velocity but reduces directionality (By similarity). Interacts with EF1A1, facilitates EF1A1 distribution to the membrane periphery and ruffles upon growth factor stimulation and suppresses cell migration. Colocalizes with EF1A1 at actin-rich regions in the cell periphery. Widely expressed with the highest levels in heart, liver and lung. The SAM domain mediates interaction with EF1A1, and functions as an autoinhibitory regulator of RhoGAP Activity. The polybasic cluster is required for activation and mediates binding to phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)) containing membranes.