Regulation of focal adhesion-associated protein tyrosine kinase by both cellular adhesion and oncogenic transformation

INCREASING evidence indicates that the integrin family of cell adhesion receptors can transduce biochemical signals from the extracellular matrix to the cell interior to modulate cell growth and differentiation¹. We have shown that integrin/ligand interactions can trigger tyrosine phosphorylation of a protein of M_r 120,000 (pp120), so it is possible that signal transduction by integrins might involve activation of intracellular protein tyrosine kinases as an early event in cell binding to the extracellular matrix². Here we report that pp120 is identical to the focal adhesion-associated protein tyrosine kinase pp!25^FAK (refs 3,4). We show that tyrosine phosphorylation of this protein is modulated both by cell adhesion and transformation by pp60^v-src, and that these changes in phosphorylation are correlated with increased pp125^FAKtyrosine kinase activity. A model is proposed to relate these findings to the molecular basis of anchorage-independent growth of transformed cells.