Fig. 4

ECM mediated FAK activation in cells requires linkage of paxillin LD4 to the FAT-H23 site. FAK-WT or FAK mutated in the FAT H23 paxillin binding site were stably expressed into FAK-/- MEFs. ECM mediated FAK activation was induced by keeping cells in suspension (Susp) prior to plating them on fibronectin (FN). FAK activation was monitored by western blot using two phosphospecific antibodies, one to detect FAK autophosphorylation on Y397 and one for phosphorylation of FAK activation loop residues Y576 and Y577. A representative experiment is shown in the left panel and the quantification is plotted in the right panel. For quantifications signals were normalized to FAK-WT in MEFs on FN. Error bars represent SD from three independent experiments. *p = 0.02 (unpaired Student t test)