Coordinated integrin and growth factor regulation of primary keratinocyte migration mediated through extracellular signal regulated kinase and phosphoinositide 3-kinase

We have examined coordinated integrin and growth factor regulation of primary keratinocyte migration mediated by phosphoinositide 3-kinase (PI3K) and mitogen-activated extracellular-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK). On collagen I and fibronectin substrates, both epidermal growth factor (EGF) and hepatocyte growth factor (HGF) stimulated chemokinetic (random) and chemotactic (directional) migration. On provisional matrix, a combination of fibronectin and fibrin found in the early phase of wound healing, EGF and HGF-stimulated significant chemotactic but little or no chemokinetic cell movement. Blocking mAbs to integrin α2β1 and α5β1 effectively inhibited EGF- and HGF-stimulated chemokinetic and chemotactic cell movement on collagen I and fibronectin, respectively; however, HGF-stimulated chemotactic migration on collagen I was only partially inhibited by α2β1 blocking mAb. Differentiated keratinocytes underwent reduced chemokinetic and chemotactic migration compared with undifferentiated keratinocytes; however, EGF-stimulated migration was reduced more than HGF-stimulated migration. When the migratory response on collagen I and fibronectin was assessed in the presence of the MEK-specific inhibitor PD98059, EGF- and HGF-stimulated chemotaxis was significantly reduced, whereas PD98059 had little effect on the stimulated chemokinesis. PI3K-specific inhibitor LY294002 reduced EGF- and HGF-stimulated chemokinesis and chemotaxis on collagen I and fibronectin. Thus β1 integrins acted in concert with EGF and HGF to regulate migration of primary keratinocytes on extracellular matrix components via PI3K and MEK/ERK.