Active cell edge and movements of concanavalin A receptors of the surface of epithelial and fibroblastic cells.

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Abstract
Movements of the receptors of concanavalin A on various parts of the surfaces of substrate-attached cells were compared. Cultured mouse embryo cells of several types were used: epithelial kidney [MPTR] cells and normal and transformed fibroblasts [L cells]. Initial distribution of receptors was random on the cells of all types. Binding of concanavalin A induced patching of its receptors on all the cell parts. Directional centripetal movement of receptors was observed only on the surface of certain cell parts, i.e., only the surface of peripheral lamellar cytoplasm was cleared of the receptors. Clearing was always initiated in the zone of lamellar cytoplasm located near active cell edges. In epithelial sheets, clearing was not observed on the surface of central cells that had no lamellar cytoplasm. Concanavalin A receptors on the cleared areas of cell surface were gradually restored after the end of incubation. Anchoring of the patches of membrane receptors by cortical microfilaments may be possible only on the surface of pseudopods and of lamellar cytoplasm but not on the surface of other cell parts. Besides receptor movements, this hypothesis may also explain differences in the adhesive properties of various parts of the cell surface.