Stimulation and inhibition of cellular functions by glucocorticoids. Correlations with rapid influences on chromatin structure.
Stimulation and inhibition of cellular functions by glucocorticoids. Correlations with rapid influences on chromatin structure.
复制标题
糖皮质激素刺激和抑制细胞功能。
DOI：
10.1016/s0021-9258(18)36016-2
复制
发表时间：
1979
期刊：
影响因子：
--
通讯作者：
J. Baxter
中科院分区：
文献类型：
--
作者：
L. Johnson;N. Lan;J. Baxter
培养基条件对糖皮质激素反应的影响已在三种类型的培养细胞中进行了检查。在大鼠垂体肿瘤细胞（GC细胞）中，提供新鲜培养基（富集培养基条件），糖皮质激素刺激生长激素的产生。相反，如果将地塞米松添加到没有新鲜培养基的培养物中3天（耗尽培养基条件），则无法诱导或抑制生长激素的合成。对于人皮肤成纤维细胞，皮质醇在富集条件下刺激[3H]胸苷结合，但在缺乏条件下抑制这种反应。在小鼠淋巴瘤（S49）细胞中，富集培养基条件显著延迟了对糖皮质激素的杀伤反应（24小时后杀伤20%，而贫培养基条件下24小时后杀伤90%）。因此，糖皮质激素反应的大小和在某些情况下的方向对细胞暴露的条件很敏感。在所有三种细胞类型中，类固醇也迅速改变了染色质结构（在无细胞条件下，通过大肠杆菌RNA聚合酶起始位点数量的变化检测到，15分钟可检测到，2小时最大）。这种早期核反应可能是积极的，也可能是消极的，也受培养条件的影响；富集的培养基倾向于类固醇对起始位点的积极或较少的消极影响，而耗尽的培养基倾向于类固醇诱导的对该染色质功能的抑制。在S49和GC细胞中，染色质变化的动力学和幅度与受体密切相关。当从培养基中去除地塞米松时，糖皮质激素复合物与细胞核结合的效果迅速消失（1/2 =大约20分钟），同时细胞核中结合激素的损失也随之消失。在抗糖皮质激素突变体S49细胞系中，没有观察到糖皮质激素对染色质的影响。一条线（R-）缺乏可检测到的糖皮质激素受体；另一种细胞系（Nti）通常具有结合激素的受体，但受体。糖皮质激素复合物更容易与细胞核结合。这些结果表明该受体参与了对染色质的刺激和抑制作用。在Nti细胞中的发现以及受体的核结合和起始位点改变之间的轻微滞后表明，除了核结合本身外，某些受体特性对染色质的影响也有责任。这些结果讨论了一个模型，其中类固醇激素启动其作用的影响，改变染色质结构的反应。这种反应的方向和强度及其对特定基因表达的影响取决于细胞的代谢状态和分化。
The effect of media conditions on the glucocorticoid response has been examined in three types of cultured cells. In rat pituitary tumor cells (GC cells) growth hormone production was stimulated by glucocorticoids provided fresh culture media was present (enriched media conditions). In contrast, dexamethasone either failed to induce or deinduce growth hormone synthesis if added to cultures which had not received fresh media for 3 days (depleted media condition). With human skin fibroblasts, cortisol stimulated [3H]thymidine incorporation in the enriched condition but inhibited this response in the depleted condition. In mouse lymphoma (S49) cells the enriched media conditions significantly delayed the killing response to glucocorticoids (20% killing after 24 h versus 90% killing after 24 h for the depleted condition). Thus, the magnitude and in some cases, the direction of the glucocorticoid response are sensitive to the conditions to which the cells are exposed. In all three cell types the steroid also rapidly (detectable by 15 min, maximal by 2 h) altered chromatin structure as detected by a change in the number of initiation sites for Escherichia coli RNA polymerase assayed under cell-free conditions. This early nuclear response could be in a positive or negative direction and was also affected by the culture conditions; enriched media favored a positive or less negative effect on the initiation sites by the steroid, while depleted media favored a steroid-induced inhibition of this chromatin function. In S49 and GC cells the kinetics and magnitude of the change in chromatin closely followed receptor . glucocorticoid complex binding to nuclei while removal of dexamethasone from the culture media resulted in a rapid (t 1/2 = approximately 20 min) disappearance of the effect which paralleled loss of bound hormone from the nucleus. The glucocorticoid effect on chromatin was not observed in two lines of glucocorticoid-resistant mutant S49 cells. One line (R-) lacks detectable glucocorticoid receptors; the other line (Nti) has receptors that bind the hormone normally, but the receptor . glucocorticoid complexes bind more avidly to the nucleus. These results suggest that the receptor is involved in both the stimulatory and the inhibitory effects on chromatin. The findings in the Nti cells and of a slight lag between nuclear binding of receptors and initiation site alteration implies that some receptor property, in addition to nuclear binding per se, is responsible for the influence on chromatin. These results are discussed in terms of a model in which steroid hormones initiate their actions by influencing a reaction that modifies chromatin structure. The direction and magnitude of the reaction, and its effect on the expression of specific genes, are dictated by the metabolic state and differentiation of the cell.