Fig. 9. Model for role of 3ß1 in the establishment of polarity by migrating wound-edge keratinocytes. (A) In quiescent epidermis, 6ß4-containing hemidesmosomes mediate stable adhesion of basal keratinocytes to the basement membrane, whereas 3ß1 is localized primarily to cell-cell borders. (B) Upon wounding, growth factors and cytokines in the wound bed stimulate actin polymerization and the formation of an initial protrusion. These initial protrusions contain 3ß1 that interacts with newly deposited LN-5 (C), stabilizing the protrusion and subsequently stimulating Rac1 activity. Rac1 activation leads to growth of a stable leading lamellipodium.