Molecular characterization of the EGF receptor and involvement of glycosyl moieties in the binding of EGF to its receptor on a clonal osteosarcoma cell line, UMR 106-06.

The epidermal growth factor receptor in cells of the UMR 106-06 clonal osteoblast line has been shown to be structurally similar to that previously characterized in other cell lines. A specific receptor component of approximately 165,000-185,000 Mr has been identified by polyacrylamide gel electrophoresis using the chemical crosslinker disuccinimidyl suberate to crosslink 125I-EGF to its receptor. Tunicamycin treatment of cells resulted in a dose-dependent loss of binding suggesting involvement of glycosyl moieties in EGF binding to its receptor. Competitive binding studies carried out using wheat germ lectin (WGL), concanavalin A (CON.A.), soybean lectin (SBL), and lentil lectin (ILL) to compete for binding of 125I-EGF revealed that CON A, WGL, and to a lesser extent LL could inhibit EGF binding; SBL was without effect. Treatment of the cells with neuraminidase which cleaves terminal sialic acid residues resulted in total loss of binding while alpha-glucosidase, beta-N-acetylglucosaminidase and alpha-mannosidase were without effect. These data indicate a specific interaction of EGF with terminal sialic acid residues of the EGF receptor. However, it would seem that the mannose residues which appeared to modify EGF binding were not available for the action of the above enzymes due to the presence of sialic acid.