FIG. 8.

A model of PAK function in relation to known effectors of Rho-p21s. The targets of Cdc42, Rac, and Rho which have known morphological roles are shown. MRCK is the myotonin kinase-related Cdc42-binding kinase (26); p140mDia is the mammalian homolog of Drosophila diaphanous (58); the other Rho-binding kinase, PKN (59), has no known morphological function. PAK acts downstream of both Cdc42 and Rac to break down actin cytoskeletal structures and focal adhesions (FAs). This function could be particularly important in remodeling the cytoskeleton to allow dynamic events such as filopodial extension and subsequent formation of lamellipodia, ultimately leading to cell migration or growth cone extension (20). MLC, myosin light chain; MLCK, myosin light-chain kinase.