Fig. 7. Cdc42 controls two distinct polarity pathways in migrating cells. Microtubule cytoskeleton polarization occurs through activation of Par6/aPKC and subsequent inhibition of GSK-3, whereas Pak controls the localization, though not the activity, of the Rac-GEF ßPIX, allowing the polarization of actin-rich, Rac-dependent protrusions.