Fig. 1. Focal adhesions provide both a structural and signaling link between the extracellular matrix and the actin cytoskeleton.

Cell adhesion to the extracellular matrix, via transmembrane integrin αβ heterodimers, leads to integrin activation and the recruitment of numerous intracellular proteins to the plasma membrane. Focal adhesions now comprise over 125 proteins (only selected examples are depicted), including both structural and regulatory molecules that mediate a physical link to the actin cytoskeleton and also play a major role in regulating actin dynamics necessary for productive cell migration. Molecules such as paxillin serve as scaffold proteins to facilitate the functional integration of these different categories of focal adhesion proteins.