Snider L D, Corey J L, Rabindran S K, Stallcup M R
Department of Pathology, University of Southern California School of Medicine, Los Angeles 90033.
Mol Endocrinol. 1990 May;4(5):749-57. doi: 10.1210/mend-4-5-749.
Glucocorticoid hormone is required for complete posttranslational processing of the glycosylated mouse mammary tumor virus envelope precursor, Pr74env in the murine T-lymphosarcoma cell line, W7MG1. Metabolic labeling studies with [35S]methionine, [3H]galactose, and [3H]mannose, combined with enzymatic digestion analyses with a variety of endoglycosidases, demonstrated that both proteolytic processing and N-linked oligosaccharide maturation depended, either directly or indirectly, on glucocorticoid action. Pr74 is found in both control and hormone-treated cells. In both cases Pr74 molecules carry high mannose and/or hybrid, but not complex, oligosaccharide chains with very little or no sialic acid. When cells are grown with glucocorticoid, Pr74 is converted to gp52 and gp33 with greatly increased efficiency, and these mature glycoproteins carry complex oligosaccharides containing sialic acid. No O-linked carbohydrate was detected on any of these species. According to this evidence, the glucocorticoid-regulated step in this pathway must occur at or before the final mannose trimming step in the Golgi that is required for formation of complex carbohydrate chains.
糖皮质激素对于小鼠T淋巴细胞肉瘤细胞系W7MG1中糖基化小鼠乳腺肿瘤病毒包膜前体Pr74env的完全翻译后加工是必需的。用[35S]甲硫氨酸、[3H]半乳糖和[3H]甘露糖进行的代谢标记研究，结合用多种内切糖苷酶进行的酶消化分析，表明蛋白水解加工和N-连接寡糖成熟都直接或间接地依赖于糖皮质激素的作用。在对照细胞和激素处理的细胞中都发现了Pr74。在这两种情况下，Pr74分子都带有高甘露糖和/或杂合型而非复合型寡糖链，且唾液酸含量极少或没有。当细胞在糖皮质激素存在下生长时，Pr74以大大提高的效率转化为gp52和gp33，并且这些成熟糖蛋白带有含有唾液酸的复合型寡糖。在这些糖蛋白中均未检测到O-连接的碳水化合物。根据这些证据，该途径中糖皮质激素调节的步骤必定发生在高尔基体中形成复合碳水化合物链所需的最终甘露糖修剪步骤之时或之前。
