Anomalous binding of epidermal growth factor to A431 cells is due to the effect of high receptor densities and a saturable endocytic system.

• DOI: 10.1083/jcb.107.2.801
• Publication Date: 2004-05-15T00:18:20Z
• Authors: H S Wiley
• Keywords: Internalization; A431 cells; Cell surface receptor; Transferrin receptor

This study was conducted to determine how extraordinarily high numbers of epidermal growth factor receptors (EGF-R) affected the binding and internalization EGF in transformed cell line A431. I found that at low concentrations, kinetics behaved as a nonsaturable, first-order process showing no evidence multiple-affinity classes receptors. However, dissociation rates were strongly dependent on degree receptor occupancy both intact cells isolated membranes. occupancy-dependent appears be due diffusion-limited binding. EGF-induced rapid first order when absolute number occupied below 4 x 10(3) min-1. higher occupancies specific rate progressively declined final limiting value 20% normal. The saturation EGF-R endocytosis since transferrin not by concentrations either or EGF. Saturation probably involves component endocytic pathway fluid phase increased coordinately with occupancy. conclude there are several aspects dynamics A431 neither similar behavior other types nor reported hormone Although have an extraordinary EGF-R, they do seem corresponding levels least two crucial surface components: one mediates attenuates membrane responses. These factors, addition presence responsible for appearance this type.