Co-capping of insulin, epidermal growth factor and concanavalin A surface receptors with each other and with cytoplasmic actin.

Concanavalin A (Con A), insulin and epidermal growth factor (EGF) surface membrane receptors on cultured bovine odontogenic epithelial cells, were demonstrated by immunofluorescent reactivity with fluorescein-isothiocyanate (FITC) conjugated Con A, FITC-insulin, or EGF and anti-EGF, traced with FITC goat anti-rabbit globulin. Con A, insulin and EGF receptors co-capped with each other and with cytoplasmic actin; the latter was demonstrated by anti-actin antibody (AAA) traced with fluorescein or rhodamine-labelled goat anti-human globulin. Capping of receptors was promoted by prior treatment of cells with cytochalasin B or colchicine, but inhibited by the presence of the drugs throughout the experimental procedure. Binding of a ligand to its receptor promoted capping of an unrelated ligand-bound receptor, a phenomenon that was inhibited by cytochalasin B or colchicine. These results suggest that surface receptors for insulin, EGF and Con A interact with each other and with cytoplasmic actin.