Cellular morphology is determined by the organization of the intracellular
actin cytoskeleton, which is influenced by external and internal cues. Foca
l adhesions are sites at which the actin cytoskeleton is linked to the extr
acellular matrix by integrin receptor complexes. In addition to providing s
tructural tethering points for cells, integrin receptor complexes transduce
signals that influence a broad range of cellular processes, including migr
ation, proliferation, transformation and apoptosis. The Cas proteins (p130C
as, HEF1/Cas-L and Efs/Sin), a family of docking proteins containing multip
le interaction domains, are important components of integrin receptor signa
lling and have been implicated in all of these processes.