The Rockefeller University Press

Integrins are transmembrane extracellular matrix receptors that not only mediate physical attachment between a cell and its environment, but also permit transduction of signals to control shape, motility, and the cell cycle in response to environmental cues. Integrin adhesions exist in multiple forms in cells, for example focal complexes, focal adhesions, and fibrillar adhe-sions, and many of the major components of these have now been identified. The assembly of multiprotein complexes initi-ated by integrin engagement and clustering is critical to their function, and thus controls motility and proliferation. Some mechanisms of integrin activation—its linkage to the actin cytoskeleton and cell motility—have been elucidated, and our knowledge of how cell structure, actin/adhesion dynamics, and cell motility are coordinated with control of proliferation and survival is increasing. Yet we still lack detail on the sequenc