The role of microfilaments in the capping of epidermal growth factor receptor in A431 cells

Capping of the EGF receptor (EGF-R) on the surface of suspended and adherent epidermoid carcinoma cells, A431, is studied. It was induced at 20 degrees C after treating cells with monoclonal antibody to the EGF receptor followed by the second antibody conjugated with FITC. Accumulation of cortical actin under the caps was detected by rhodamine-phalloidin. Destruction of the actin stress-fiber-like bundles was observed during incubation of cells with the ligands at 0 degrees C. Two processes appear to take place at 20 degrees C: redistribution of the EGF-R with cortical actin into the caps within 15-30 min and reconstruction of cytoplasmic actin bundles over 45-60 min. Dihydrocytochalasin B prevented cap formation in adherent cells, but small patches of EGF-R colocalized with actin aggregates under plasma membrane were observed. The function of different actin-containing cytoskeleton structures in the process of capping is discussed.