cdc42 is a member of the Rho family of small GTP-binding proteins, and plays roles in cytoskeletal Actin organization as well as transformation. Rac is activated downstream of cdc42, or independently by Ras signaling, and in turn Rac stimulates Rho. Activation of cdc42 stimulates filopodia formation, whereas Rac results in the formation of lamellipodia, and Rho stimulates formation of actin stress fibers. Effectors of the cdc42/Rac pathway include NADPH Oxidase (Phox) and the SAPK1/JNK family of kinases. The latter pathway is activated by the PAK kinases, which are direct targets of cdc42.
