Fig. 10. Laminin 5 deposits direct processive migration on collagen. Step 1. Deposition contacts: rapid switch of adhesion from exogenous collagen (blue) and integrin 2 (open ovals) to laminin 5 deposits (green ovals) and integrin 3ß1 (red bars). Deposition of laminin 5 down onto the substratum is regulated differently than apical secretion of laminin 5, fibronectin, laminin 1 and thrombospondin into the culture medium. Step 2. Polarization: integrin 3-laminin 5 interactions mediate polarization. Focal complexes form under the lamellipodia with exogenous ligand while laminin 5 deposits are restricted to the rear of the cell. Step 3. Processive migration removes exogenous collagen at precise sites of laminin 5 deposits that are restricted to the rear of the cell. Persistence of linear migration is not in response to a chemotactic gradient.