β1 Integrin is Required for the Dynamic Turnover of Cell-surface Adhesive Contacts

To move naturally within a tissue during development and differentiation, or in response to injury, mammalian cells utilize transmembrane integrin receptors to make and break contacts with their underlying substratum composed of extracellular matrix ligands. On the inside surface of the cell, the cytoplasmic tails of β-integrins form complexes with other proteins and with the actin-myosin cytoskeleton. In the resting state, thick actinomyosin cables anchor to robust integrin-mediated focal contacts, and cells adhere tightly to their substratum. To move, this network must be turned over, a process whose regulation involves the focal adhesion kinase (FAK).

β1 integrin is essential for efficient focal adhesion turnover. Here, we show that when β1 integrin is genetically mutated in epidermal keratinocytes, robust cell surface adhesive contacts form, which are not turned over efficiently. As a consequence, the knockout (KO) cells adhere tightly to the dish, and can't move effectively. In contrast, wild-type (WT) cells make and break contacts continuously. The actin network is labeled in green with GFP-actin; the integrin-containing focal adhesions are labeled in red with RFP-zyxin. Both the KO and WT cells express β6 integrin, but this integrin needs to work in conjunction with β1 integrin to regulate the focal adhesions.

 β1 Integrin is Required for the Dynamic Turnover of Cell-surface Adhesive ContactsTo move naturally within a tissue during development and differentiation, or in response to injury,