Fig. 7. A proposed scheme for the morphological changes elicited by the PAK-PIX-GIT1 complex. PIX is localized at the cell periphery, possibly by the localization signal found in the PIX coiled-coil C terminus or via formation of PIX dimers that interact with other proteins or phospholipids found at the plasma membrane-cytoskeleton interface. PAK is recruited to the focal complexes (FCs) through its binding to membrane-bound PIX, which also binds to GIT1, which in turn binds paxillin (Turner et al., 1999; Zhao et al., 2000a). Active PIX could then induce membrane ruffles by activating Rac1 as well as the formation of filopodium- and microvillus-like structures by activating Cdc42. Upon autophosphorylation, PAK dissociates from the PIX-GIT1 complex, whereas PIX-GIT1 remains at the cell periphery.