TGF-β1 enhances βig-h3-mediated keratinocyte cell migration through the α3β1 integrin and PI3K

βig-h3 is an extracellular matrix (ECM) protein whose expression is highly induced by transforming growth factor beta1 (TGF-β1). We previously demonstrated that βig-h3 has two α3β1 integrin-interacting motifs, which promote adhesion, migration, and proliferation of human keratinocytes. Both βig-h3 and TGF-β1 have been suggested to play important roles in the healing of skin wounds. In this study, we demonstrate that TGF-β1 enhances keratinocyte adhesion and migration toward βig-h3 through the α3β1 integrin. TGF-β1 did not increase the amount of the α3β1 integrin on the cell surface, but rather increased its affinity for βig-h3. LY294002, an inhibitor of PI3K, blocked the basal and TGF-β1-enhanced cell migration but not adhesion to βig-h3. A constitutively active mutant of PI3K stimulated cell migration but not adhesion to βig-h3. The PI3K pathway is also not associated with the affinity of the α3β1 integrin to βig-h3. TGF-β1 induced phosphorylation of AKT and FAK. Taken together, these data suggest that TGF-β1 increases affinity of the α3β1 integrin to βig-h3, resulting in enhanced adhesion and migration of keratinocytes toward βig-h3. TGF-β1 also enhances migration through PI3K, but PI3K is not associated with either the binding affinity of the α3β1 integrin or its adhesion to βig-h3.