Signal transduction from the extracellular matrix--a role for the focal adhesion protein-tyrosine kinase FAK.

The proliferation and differentiation of cells in higher organisms requires specific external signals. These can be presented to target cells in the form of soluble peptide hormones, proteins retained on the surface of adjacent cells, or as part of the extracellular matrix (ECM). Manygrowth factors activate membrane-associated receptor protein-tyrosine kinases (PTKs), which in turn stimulate intracellular signal transduction pathways. Whereas muchprogress has been made in characterizing growth factor receptor PTKs signal transduction, less is known about the mechanisms by which signals from the extracellular matrix are transduced into the interior of the cell. Extracellular matrix proteins such as fibronectin,