Vinculin and alpha-catenin: shared and unique functions in adherens junctions.

Vinculin and alpha-catenin are two functionally related proteins of adherens junctions, structures in which cells make contacts to neighboring cells or to the extracellular matrix. At these sites, the actin cytoskeleton of animal cells is anchored to the plasma membrane. Junction assembly and disassembly are coordinated in processes as different as mitosis, cell movement and tissue formation. Since adherens junctions are assembled from a large number of proteins, these molecules have to be coordinately activated and spatially regulated. Vinculin and alpha-catenin have been characterized as tumor suppressors, suggesting that they have a regulatory function in addition to their structural role. Several possible modes of vinculin and alpha-catenin regulation are discussed here, as the published data favor the concept that no single model fully explains the complexity of adherens junctions. Most probably, cells select from a variety of possibilities to solve the problem of making specific contacts.