The structure and regulation of vinculin

Vinculin is a ubiquitously expressed actin-binding protein frequently used as a marker for both cell-cell and cell-extracellular matrix (focal adhesion) adherens-type junctions, but its function has remained elusive. Vinculin is made up of a globular head linked to a tail domain by a short proline-rich sequence, and an intramolecular interaction between the head and tail masks the numerous ligand-binding sites in the protein. Determination of the crystal structure of vinculin has shed new light on the way that these ligand-binding sites are regulated. The picture that emerges is one in which vinculin stabilizes focal adhesions and thereby suppresses cell migration, an effect that is relieved by transient changes in the local concentrations of inositol phospholipids. However, the finding that vinculin modulates the signalling pathways involved in apoptosis suggests that additional roles for vinculin remain to be discovered.