FIGURE 18-53 Independent Cdc42 regulation of microfilaments and microtubules to polarize a migrating cell. Active Cdc42·GTP at the front of the cell leads to Rac and WASP activation, which results in the assembly of a microfilament-based leading edge (step 1). Independently, Cdc42·GTP also leads to the capture of microtubule (+) ends and the activation of dynein (step 2). Dynein pulls on microtubules to orient the centrosome (step 3) toward the front of the cell. This reorientation reorganizes the secretory pathway for the delivery of adhesion molecules carried in secretory vesicles along microtubules to the front of the cell (step 4). See S. Etienne-Manneville et al., 2005, J. Cell Biol. 170:895–901.