Electric field-directed cell motility involves up-regulated expression andasymmetric redistribution of the epidermal growth factor receptors and is enhanced by fibronectin and laminin

Wounding corneal epithelium establishes a laterally oriented, DC electric f ield (EF). Corneal epithelial cells (CECs) cultured in similar physiologica l EFs migrate cathodally, but this requires serum growth factors. Migration depends also on the substrate. On fibronectin (FN) or laminin (LAM) substr ates in EF, cells migrated faster and more directly cathodally. This also w as serum dependent. Epidermal growth factor (EGF) restored cathodal-directe d migration in serum-free medium. Therefore, the hypothesis that EGF is a s erum constituent underlying both field-directed migration and enhanced migr ation on ECM molecules was tested. We: used immunofluorescence, flow cytome try, and confocal microscopy and report that 1) EF exposure up-regulated th e EGF receptor (EGFR); so also did growing cells on substrates of FN or LAM ; and 2) EGFRs and actin accumulated in the cathodal-directed half of CECs, within 10 min in EF. The cathodal asymmetry of EGFR and actin staining was correlated, being most marked at the cell-substrate interface and showing similar patterns of asymmetry at various levels through a cell. At the cell -substrate interface, EGFRs and actin frequently colocalized as interdigita ted, punctate spots resembling tank tracks. Cathodal accumulation of EGFR a nd actin did not occur in the absence of serum but were restored by adding ligand to serum-free medium. inhibition of MAPK, one second messenger engag ed by EGF, si,significantly reduced EF-directed cell migration. Transformin g growth factor beta and fibroblast growth factor also restored cathodal-di rected cell migration in serum-free medium. However, longer EF exposure was needed to show clear asymmetric distribution of the receptors for transfor ming growth factor beta and fibroblast growth factor. We propose that up-re gulated expression and redistribution of EGFRs underlie cathodal-directed m igration of CECs and directed migration induced by EF on FN and LAM.