Gamou S, Hirai M, Rikimaru K, Enomoto S, Shimizu N
Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan.
Cell Struct Funct. 1988 Feb;13(1):25-38. doi: 10.1247/csf.13.25.
The biosynthesis of the EGF receptor was examined in the epidermoid carcinoma cell line A431 and five novel cell lines from human squamous cell carcinomas possessing high numbers of EGF receptors. Newly synthesized EGF receptors were visualized by labeling with [35S]methionine and immunoprecipitation with a monoclonal anti-EGF receptor antibody. In addition, the processing of the EGF receptor and its intracellular transport was analyzed by distinguishing cell surface receptors from intracellular receptors and by treating cells with inhibitors such as tunicamycin, monensin and brefeldin A. These analyses revealed that in all the tumor cell lines the EGF receptor is synthesized as a glycosylated protein of Mr 160,000 which is converted to the receptor of Mr 170,000 through posttranslational glycosylation. The receptors of Mr 160,000 and 170,000 appeared to possess high mannose type oligosaccharide chains because endoglycosidase H treatment reduced their molecular weights by approximately 30,000. A431 was the only tumor cell line studied that secreted the truncated EGF receptor of Mr 110,000. In A431 cells, the truncated EGF receptor was generated from a protein of Mr 60,000 through tunicamycin- and monensin-sensitive glycosylation. A431 cells treated with monensin secreted the truncated receptor as a Mr 95,000 form.
在表皮样癌细胞系A431和五种来自人鳞状细胞癌且具有大量表皮生长因子（EGF）受体的新型细胞系中，研究了EGF受体的生物合成。通过用[35S]甲硫氨酸标记并用单克隆抗EGF受体抗体进行免疫沉淀来观察新合成的EGF受体。此外，通过区分细胞表面受体和细胞内受体以及用衣霉素、莫能菌素和布雷菲德菌素A等抑制剂处理细胞，分析了EGF受体的加工过程及其细胞内运输。这些分析表明，在所有肿瘤细胞系中，EGF受体均作为分子量为160,000的糖基化蛋白合成，该蛋白通过翻译后糖基化转化为分子量为170,000的受体。分子量为160,000和170,000的受体似乎具有高甘露糖型寡糖链，因为内切糖苷酶H处理使其分子量降低了约30,000。A431是所研究的唯一分泌分子量为110,000的截短型EGF受体的肿瘤细胞系。在A431细胞中，截短型EGF受体由分子量为60,000的蛋白质通过对衣霉素和莫能菌素敏感的糖基化产生。用莫能菌素处理的A431细胞分泌截短型受体，其形式为分子量95,000。
