SWAP70 functions as a guanine nucleotide exchange factor for Rac and RhoA regulating F-actin cytoskeletal rearrangements and playing a crucial role in mammalian cell activation, migration, adhesion, and invasion. Rearrangements of the actin cytoskeleton are regulated in part by dynamic localized activation and inactivation of Rho family small GTPases. SWAP70 binds to and activates the small GTPase RAC1 as well as binding to filamentous actin and PIP3. SWAP70 adopts a distinct conformation at the plasma membrane, which in migrating glioma cells is enriched at the leading edge but does not always associate with its PIP3 -dependent translocation to the membrane. NRL1 interacts in yeast and in planta with a guanine nucleotide exchange factor called SWAP70. SWAP70 associates with endosomes and is a positive regulator of immunity.