Lectin binding to cell surfaces: comparisons between normal and migrating corneal epithelium

Comparisons were made between cell surfaces of normal and migrating corneal epithelium of the rat by localizing and/or quantifying concanavalin A (Con A) and wheat germ agglutinin (WGA) binding. Our results indicate that apical cell surfaces of the leading edge of a migrating sheet of epithelium differ from those of normal epithelium and that the various cell layers within the stratified normal epithelium have different lectin-binding characteristics. Three methods of monitoring lectin binding to cell surfaces were employed. Based on ferritin-conjugated Con A, ferritin-conjugated WGA, and [3H]Con A binding, apical cell membranes of migrating epithelia bind more Con A and WGA than do apical membranes of superficial cells of normal stratified epithelia. With both fluorescein isothiocyanate (FITC)-Con A and -WGA, membranes of all the cells of the leading edge of the migrating sheet fluoresce intensely. FITC-Con A binding of normal stratified epithelium is relatively uniform through all cell layers with no discernible staining of the apical membrane of superficial cells. With FITC-WGA, however, fluorescence is present only on basal cell layers but not on superficial cells. These data demonstrate that apical cell surface sugars on a sheet of epithelium migrating to cover a wound differ from the apical cell surface sugars of normal epithelium. As indicated by FITC-WGA binding, cells of the migrating sheet have cell surface characteristics similar to basal cells of normal epithelia. Perhaps, upon wounding, the leading edge of the migrating sheet is derived from the basal cell population of the normal stratified epithelium, or perhaps there is an alteration in cell surface glycoproteins as the cells become migratory.