Focal adhesions (FAs), also known as ‘focal contacts’, are specialized, extracellular matrix (ECM) attachment and signaling organelles, usually measuring a few square microns, located along the ventral plasma membrane of adherent cultured cells. Interference reflection microscopy, electron microscopy and micro-mechanical measurements indicate that the cell membrane in these sites is tightly connected with the substrate surface and that the gap remaining is only ∼10-15 nm. At their cytoplasmic aspects, FAs are associated with bundles of actin microfilaments and apparently play an important role in cell spreading and migration.
FAs are transmembrane anchorage sites, in which the ECM is indirectly linked to the actin cytoskeleton via a web of submembrane ‘anchor proteins’. Thus, characterization of the molecular components of these adhesions and their precise organization appears to be important if we are to understand the function of FAs in both the mechanical interaction with the matrix and the generation and transduction...
