Abl interactor 1 (Abi1) is one of the major regulators of actin cytoskeleton reorganization through participation in several multiprotein complexes that either associate with actin filaments through spectrin or Eps8 or that regulate the dynamics of actin polymerization more indirectly, for instance through regulation of small GTPase activities of the Rho family. Rho GTPases are modulated by complexes of Abi1 with Eps8–Sos1 and downstream actin polymerization e.g. by N-WASP and WAVE complex.