Purpose: Migration of corneal epithelial cells is an important step in the corneal wound healing. The role of extracellular signal regulated kinase (ERK) for the regulation of cell migration during wound closure was examined.
Methods: Scratch wounds were introduced into human corneal epithelial cells in the absence or presence of PD98059, an ERK signaling inhibitor. The phosphorylation and localization of ERK during wound closure were examined by immunoblot and immunofluorescence analyses. The tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin, as well as the association of FAK with paxillin and ERK, were evaluated by immunoprecipitation and immunoblot analysis. The effect of a mutant form of MEK1 on cell migration and proliferation was determined by transfection.
Results: PD98059 inhibited cell migration in a concentration- and time-dependent manner. Wounding increased the phosphorylation of ERK as well as the tyrosine phosphorylation of FAK and paxillin in a manner sensitive to PD98059. Furthermore, wounding induced the formation of an ERK-FAK-paxillin complex and this effect as well as the wounding-induced formation of focal adhesions, membrane ruffles, and bundles of F-actin, were inhibited by PD98059. Phosphorylated ERK localized at the wound margin, and such localization was not observed in the presence of PD98059. Expression of dominant negative mutant form of MEK1 inhibited cell migration during wound closure without the effect of cell proliferation.
Conclusions: ERK regulates cell migration during wound healing in vitro by modulating the phosphorylation of FAK and paxillin and the consequent formation of focal adhesions. An ERK-FAK-paxillin signaling pathway may play an important role in corneal epithelial wound healing in vivo.