CELL SPREADING ON EXTRACELLULAR-MATRIX PROTEINS INDUCES TYROSINE PHOSPHORYLATION OF TENSIN

A small number of proteins becomes tyrosine-phosphorylated in response to integrin-mediated cell adhesion to extracellular matrix proteins. Previous work has identified two of these tyrosine-phosphorylated prot eins as the focal adhesion kinase and paxillin. Here we identify a thi rd focal adhesion protein, tensin, that becomes tyrosine-phosphorylate d during cell adhesion to extracellular matrix proteins. The tyrosine phosphorylation of tensin does not occur when cells adhere to plastic or polylysine and is blocked when microfilament assembly and cell spre ading are inhibited with cytochalasin D. In addition, we show that oth er focal adhesion proteins such as talin and vinculin do not become ty rosine-phosphorylated under the same conditions of cell spreading on e xtracellular matrix proteins.