Activation of integrins in the extracellular matrix (ECM) of eukaryotic cells
promotes the formation of membrane adhesion complexes, known as focal
adhesions, which can include cytoskeletal proteins and protein tyrosine
kinases, such as focal adhesion kinase (FAK). Phosphorylation events occurring
within focal adhesions influence numerous processes that include mitogenic
signaling, cell survival and cell motility. FAK is a non-receptor tyrosine
kinase that is ubiquitously expressed and highly conserved between species.
FAK is recruited by integrin clusters and variably phosphorylated depending
on the effector molecules present in the focal adhesion. Phosphorylation of
FAK Tyr 397 decreases during serum starvation, contact inhibition and cell
cycle arrest, all conditions under which activating FAK Tyr 407 phosphorylation
increases.