STIMULATION OF TYROSINE-PHOSPHORYLATION AND SERINE-PHOSPHORYLATION OFFOCAL ADHESION KINASE IN MOUSE 3T3 CELLS BY FIBRONECTIN AND FIBROBLAST GROWTH-FACTOR

Phosphorylation of both tyrosine and serine residues of focal adhesion kinase (FAK) was stimulated by the adhesion of BALB/c mouse 3T3 cells to fibronectin, but phosphorylation of threonine was not detectable. Acidic and basic fibroblast growth factors also stimulated the phospho rylation of serine and tyrosine of FAK in cells adhered to poly-L-lysi ne, but epidermal growth factor and platelet-derived growth factor did not. A fusion protein of fibronectin and basic fibroblast growth fact or effectively induced the phosphorylation of FAK. Phosphorylation of FAK in the rat myoblast L-6 cell line, which lacks fibroblast growth f actor receptors, was not stimulated by fibroblast growth factors, sugg esting that the interaction of fibroblast growth factors with their re ceptors might cause the phosphorylation of FAK.