Signal transduction and actin filament organization.

Small GTP-binding proteins of the Rho family appear to integrate extracellular signals from diverse receptor types and initiate rearrangements of F-actin. Active members of the Rho family, Rho and Rac, are now joined by Cdc42 which induces filopodia. Downstream of the Rho family proteins, actin polymerization may be induced by an increase in the availability of actin filament barbed ends. Actin organization may be affected by exposure of actin-binding sites on proteins such as vinculin and ezrin.