REGULATION OF ACTIN CYTOSKELETON BY RHO-FAMILY GTPASES AND THEIR ASSOCIATED PROTEINS

Cdc42, Pac and Rho GTPase each regulates distinct morphological change s in response to specific growth factors. These changes which involve actin-containing cytoskeletal structures may underlie aspects of growt h and development. Proteins binding to the active GTP-bound form of th e GTPase including the Cdc42/Rac activated PAK, and the Rho associated kinase ROK can act as morphological effecters as can the RacGAP chima erin. In fibroblasts and neuronal-type cells, the growth factors evoke morphological changes by activating individual GTPase pathways or Rac -Rho and Cdc42-Rac hierarchical pathways. There is also evidence for C dc42-Rho antagonism. The morphological outcome will depend on the leve l of activation of the different GTPases by their stimulatory growth f actor. (C) 1996 Academic Press Ltd