Six tyrosine phosphorylation sites in focal adhesion kinase 1 (FAK1) serve to modulate FAK1 kinase activity or mediate FAK1 interaction with SH2-domain containing proteins. These are Y397, Y407, Y576, Y577, Y861 and Y925 (Mitra et al. 2005). They are differentially phosphorylated by diverse agonists and implicated in transmitting different signals and effects (Ciccimaro et al. 2006, Le Boeuf et al. 2004,2006). Y397 is the major autophosphorylation site present upstream of the FAK kinase domain (Schaller et al. 1994). In response to VEGF stimulation FAK1 is recruited and autophosphorylated at Y397. This phosphorylated tyrosine then creates a binding site for other signaling proteins that link FAK1 to downstream signaling pathways and the actin cytoskeleton (Toutant et al. 2002).