ABSTRACT
Integrin-mediated contact of cells with extracellular matrices promotes not only adhesion, spreading, and cytoskeletal organization, but also regulates a variety of cell functions. Several groups have reported that adhesion of cells to extracellular matrix (ECM) or treatment with antibodies to integrins stimulates expression of specific genes. Several members of the src family of nonreceptor tyrosine kinases, as well as much of the cellular phosphotyrosine, localize by immunohistochemistry to sites of cell-ECM and cell-cell contact. In a number of instances where ECM proteins regulate cell functions, exogenous activators of protein kinase C (PKC) can replace the need for adhesion. The papers have reported ostensibly direct effects of ECM on inositol lipid breakdown. Whatever the mechanism, PKC activation could trigger activation of leukocytes, focal adhesion formation, gene expression, and other events induced by ECM. PKC also seems to be involved in the formation of focal contacts. PKC could be activated if integrins triggered phospholipase C.
