Uniaxial Cyclic Stretch Induces Focal Adhesion Kinase (FAK) Tyrosine Phosphorylation Followed by Mitogen-Activated Protein Kinase (MAPK) Activation

We investigated the role of tyrosine phosphorylation of FAK in the stretch-induced MAPKs (extracellular signal-regulated kinase (ERK), p38MAPK) activation in mutant FAK-transfected fibroblasts. In response to uniaxial cyclic stretch (1 Hz, 120% in length), the levels of tyrosine phosphorylation of the Tyr-397 and Tyr-925 of FAK in control cells increased and peaked at 5 min (2.75 ± 0.51, n = 3), and 20 min (2.98 ± 0.58, n = 3), respectively, and the activities of MAPKs increased and peaked at approximately 10 min. On the other hand, in the mutant FAK-transfected cells, the stretch-induced MAPKs activation was significantly inhibited. The stretch-induced activation of MAPKs was also significantly abolished by either treatment with Gd3+ or extracellular Ca2+ removal which may inhibit intracellular Ca2+ increase caused by the activation of cation selective (Ca2+-permeable) stretch activated (SACatC) channels. These results suggest that the stretch-induced tyrosine-phosphorylation of FAK via SACatC activation is critical for the stretch-induced MAPKs activation.