Lam M, Vimmerstedt L J, Schlatter L K, Hensold J O, Distelhorst C W
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH.
Blood. 1992 Jun 15;79(12):3285-92.
To investigate the mechanism of glucocorticoid-induced lymphocytolysis, we used two-dimensional gel electrophoresis to analyze the effect of dexamethasone on the synthesis of individual proteins in S49 mouse lymphoma cells. We found that synthesis of a 78-Kd protein is preferentially maintained following dexamethasone treatment, at a time when the synthesis of most other cellular proteins is decreased. Synthesis of this protein could also be induced by tunicamycin, suggesting that it might be the 78-Kd glucose-regulated protein (GRP78). The identity of the 78-Kd protein with GRP78 was confirmed by limited chymotryptic mapping and immunoprecipitation analysis. Preferential synthesis of GRP78 in dexamethasone-treated cells was not secondary to alterations in the glycosylation of cellular proteins. Significantly, steady-state levels of GRP78 mRNA were unchanged following dexamethasone treatment. Preferential synthesis of GRP78 in glucocorticoid-treated S49 cells may reflect the unique property of GRP78 mRNA to be translated under conditions that interfere with the translation of most other cellular mRNAs. GRP78 is a highly conserved protein that is essential for cell viability. Preferential synthesis of GRP78 may be a protective response to metabolic events that interfere with normal mRNA translation in glucocorticoid-treated mouse lymphoma cells.
为了研究糖皮质激素诱导淋巴细胞溶解的机制，我们使用二维凝胶电泳分析地塞米松对S49小鼠淋巴瘤细胞中单个蛋白质合成的影响。我们发现，在大多数其他细胞蛋白质合成减少的时候，地塞米松处理后一种78-Kd蛋白质的合成被优先维持。衣霉素也可诱导这种蛋白质的合成，这表明它可能是78-Kd葡萄糖调节蛋白（GRP78）。通过有限的胰凝乳蛋白酶图谱分析和免疫沉淀分析证实了78-Kd蛋白质与GRP78的一致性。地塞米松处理细胞中GRP78的优先合成并非细胞蛋白质糖基化改变的继发结果。值得注意的是，地塞米松处理后GRP78 mRNA的稳态水平未发生变化。糖皮质激素处理的S49细胞中GRP78的优先合成可能反映了GRP78 mRNA在干扰大多数其他细胞mRNA翻译的条件下仍能进行翻译的独特特性。GRP78是一种对细胞活力至关重要的高度保守蛋白质。GRP78的优先合成可能是对干扰糖皮质激素处理的小鼠淋巴瘤细胞中正常mRNA翻译的代谢事件的一种保护反应。
