Integrin-mediated migration of murine B82L fibroblasts is dependent on theexpression of an intact epidermal growth factor receptor

To evaluate the mechanisms by which epidermal growth factor (EGF) regulates actin-based cellular processes such as cell migration, we first examined t he effects of EGF on cell adhesion, which is essential for cell migration. In mouse B82L fibroblasts transfected with the full-length EGF receptor, EG F promotes cell Pounding and attenuates cell spreading on fibronectin, lami nin, and vitronectin, and thus appears to reduce the strength of cell adhes ion. Moreover, EGF synergizes with multiple extracellular matrix (ECM) comp onents in the promotion of integrin-mediated cell migration of several diff erent cell types, including fibroblasts and various carcinoma and osteosarc oma cell lilies. Interestingly, co-presentation (co-positioning) of EGF wit h laminin or fibronectin is essential for EGF-stimulated migration. When EG F is mixed with the cells instead of the ECM components, it has little effe ct on cell migration. These results suggest that co-presentation of EGF wit h ECM components can enhance the polarization events required for direction al cell movement. To identify the EGF receptor elements critical for the EG F stimulation of cell migration, B82L fibroblasts were transfected with eit her mutated or wild-type EGF receptors, Surprisingly, we found that B82L-Pa rental cells that lack the EGF receptor are not able to migrate to fibronec tin, even though they can adhere to fibronectin. However, the introduction of wild-type EGF receptors into these fibroblasts enables them to migrate t oward fibronectin even in the absence of EGF, The requirement of the EGF re ceptor for cell migration does not appear to result from the secretion of E GF or TGF-alpha by the cells transfected with the EGF receptor. Furthermore , cells expressing EGF receptors that are kinase-inactive, or C-terminally truncated, exhibit little migration toward fibronectin, indicating that an intact EGF receptor kinase is required for fibronectin-induced cell migrati on. In addition, neutralizing anti-EGF receptor antibodies attenuate cell m igration in the presence of EGF, and inhibit migration to fibronectin or la minin alone. These results further suggest that the EGF receptor is downstr eam of integrin activation in the signal transduction pathways leading to f ibroblast migration.