REGULATION OF INTEGRIN FUNCTION

Cells communicate with their environment through several kinds of cell surface receptor One of the most important families of cell adhesion receptors are the integrins, which include receptors that mediate cell -cell as well as cell-extracellular matrix interactions. A distinctive feature of integrins is their variable adhesive competence that is re versibly modified depending on the state of cell differentiation and/o r activation or in response to environmental signals. The acquisition of adhesive function by integrins may be a consequence of conformation al changes in, these receptors that result in an, increased ligand bin ding affinity. In addition, cells can control integrin-mediated adhesi on through other mechanisms, including receptor clustering and associa tion to cytoskeleton, phenomena that regulate the avidity of integrins for ligand molecules without altering their monovalent affinity. Thes e phenomena have collectively been designated as 'post-receptor occupa ncy events'. These two interesting aspects of the regulation of integr in function are reviewed.