TGF-beta1 enhances betaig-h3-mediated keratinocyte cell migration through the alpha3beta1 integrin and PI3K

Abstract

betaig-h3 is an extracellular matrix (ECM) protein whose expression is highly induced by transforming growth factor beta1 (TGF-beta1). We previously demonstrated that betaig-h3 has two alpha3beta1 integrin-interacting motifs, which promote adhesion, migration, and proliferation of human keratinocytes. Both betaig-h3 and TGF-beta1 have been suggested to play important roles in the healing of skin wounds. In this study, we demonstrate that TGF-beta1 enhances keratinocyte adhesion and migration toward betaig-h3 through the alpha3beta1 integrin. TGF-beta1 did not increase the amount of the alpha3beta1 integrin on the cell surface, but rather increased its affinity for betaig-h3. LY294002, an inhibitor of PI3K, blocked the basal and TGF-beta1-enhanced cell migration but not adhesion to betaig-h3. A constitutively active mutant of PI3K stimulated cell migration but not adhesion to betaig-h3. The PI3K pathway is also not associated with the affinity of the alpha3beta1 integrin to betaig-h3. TGF-beta1 induced phosphorylation of AKT and FAK. Taken together, these data suggest that TGF-beta1 increases affinity of the alpha3beta1 integrin to betaig-h3, resulting in enhanced adhesion and migration of keratinocytes toward betaig-h3. TGF-beta1 also enhances migration through PI3K, but PI3K is not associated with either the binding affinity of the alpha3beta1 integrin or its adhesion to betaig-h3.