Baumann H, Held W A
J Biol Chem. 1981 Oct 10;256(19):10145-55.
Exposure of rat hepatoma tissue culture cells to dexamethasone results in appearance of a new glycoprotein, gp35-50 (Mr = 35,000 to 50,000) and increased synthesis of another glycoprotein, gp50 (Mr = 50,000). The glycoproteins synthesized in a fractionated cell-free translation system (containing dog pancreas microsomes) appear as a well separated series of spots on two-dimensional polyacrylamide gels which differ in size and charge. Glycoproteins synthesized by glucose-starved cells show similar size and charge heterogeneity. The size heterogeneity consists of a series of spots, each differing in molecular weights by about 3,000, which could be almost completely abolished by treatment with endo-beta-N-acetylglucosaminidase H. Our results indicate that unglycosylated gp50 (Mr = 42,000) typically acquires 3 N-glycan units, whereas gp35-50 (Mr = 22,000) possesses eight N-glycosylation sites. Analysis of the cell-free translation products directed by mRNA from hepatoma tissue culture cells grown in tissue culture, from hepatoma tissue, and from normal liver tissue indicated that administration of dexamethasone causes a pronounced increase in gp35-50 mRNA in all three tissues. A similar increase was observed in liver after inflammation which along with other biochemical properties suggests that gp35-50 may be alpha 1-acid protein. In contrast, mRNA coding for gp50 was not increased by dexamethasone in tumor tissue and no protein structurally related to gp50 was detected in the liver mRNA translation products. Thus, gp35-50 is expressed in normal liver, whereas gp50 is expressed in hepatoma cells and is differentially regulated by steroid hormones depending on whether the cells are grown in tissue culture or as a tumor in the rat.
将大鼠肝癌组织培养细胞暴露于地塞米松会导致一种新的糖蛋白gp35 - 50（分子量 = 35,000至50,000）出现，并使另一种糖蛋白gp50（分子量 = 50,000）的合成增加。在无细胞分级翻译系统（包含犬胰腺微粒体）中合成的糖蛋白在二维聚丙烯酰胺凝胶上呈现为一系列分离良好的斑点，其大小和电荷不同。葡萄糖饥饿细胞合成的糖蛋白表现出类似的大小和电荷异质性。大小异质性由一系列斑点组成，每个斑点的分子量相差约3,000，用内切β - N - 乙酰葡糖胺糖苷酶H处理几乎可以完全消除这种差异。我们的结果表明，未糖基化的gp50（分子量 = 42,000）通常获得3个N - 聚糖单元，而gp35 - 50（分子量 = 22,000）拥有8个N - 糖基化位点。对来自组织培养中生长的肝癌组织培养细胞、肝癌组织和正常肝组织的mRNA所指导的无细胞翻译产物的分析表明，给予地塞米松会使所有这三种组织中的gp35 - 50 mRNA显著增加。炎症后肝脏中也观察到类似的增加，这与其他生化特性一起表明gp35 - 50可能是α1 - 酸性蛋白。相比之下，肿瘤组织中地塞米松不会增加编码gp50的mRNA，并且在肝脏mRNA翻译产物中未检测到与gp50结构相关的蛋白质。因此，gp35 - 50在正常肝脏中表达，而gp50在肝癌细胞中表达，并且根据细胞是在组织培养中生长还是在大鼠体内作为肿瘤生长，其受到类固醇激素的差异调节。
