A glucocorticoid-resistant rat hepatoma cell variant contains functional glucocorticoid receptor.
A glucocorticoid-resistant rat hepatoma cell variant contains functional glucocorticoid receptor.
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糖皮质激素耐药的大鼠肝癌细胞变体含有功能性糖皮质激素受体。
DOI：
10.1016/s0021-9258(19)39145-8
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
J
中科院分区：
文献类型：
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作者：
Yu Dong;William Cairns;S. Okret;J
在含有低水平糖皮质激素受体的大鼠肝癌细胞变体（6.10.2）中研究了糖皮质激素抵抗的机制。这些细胞似乎已经失去了糖皮质激素诱导的转录反应，如通过诱导稳定整合的小鼠乳腺肿瘤病毒基因和内源性酪氨酸转氨酶基因的表达，以及糖皮质激素受体基因表达的转录抑制所测量的。然而，在6.10.2细胞中糖皮质激素抗性的表征显示，该受体在激素结合和对非特异性和特异性DNA序列的亲和力方面与野生型受体没有区别。在6.10.2细胞中发现的受体mRNA和总免疫反应性蛋白的水平约为野生型细胞中发现的水平的20%。对6.10.2细胞的进一步分析表明，该受体确实具有生物学功能。首先，用8-溴-cAMP处理6.10.2细胞使内源性糖皮质激素受体水平升高2倍，并恢复对糖皮质激素的反应性。其次，放线菌酮预处理的细胞也导致收购的细胞对糖皮质激素的反应。我们认为，糖皮质激素受体存在一个反应所需的“阈值”水平，并且在正常培养条件下，6.10.2细胞中糖皮质激素受体的水平低于该阈值。然而，糖皮质激素的反应性可以通过用8-溴-cAMP将糖皮质激素受体水平提高到阈值以上，或者通过用放线菌酮去除阈值屏障来恢复。
The mechanism of glucocorticoid resistance was studied in a rat hepatoma cell variant (6.10.2) which contains low levels of glucocorticoid receptor. These cells seem to have lost glucocorticoid-induced transcriptional responses as measured by the induction of expression of stably integrated mouse mammary tumor virus gene and the endogenous tyrosine aminotransferase gene, as well as the transcriptional suppression of glucocorticoid receptor gene expression. However, characterization of the glucocorticoid resistance in 6.10.2 cells revealed that the receptor is indistinguishable from the wild-type receptor with respect to hormone binding and affinity for both nonspecific and specific DNA sequences. The levels of the receptor mRNA and the total immunoreactive protein found in 6.10.2 cells were about 20% of those found in wild-type cells. Further analysis of 6.10.2 cells demonstrated that the receptor was indeed biologically functional. First, treatment of 6.10.2 cells with 8-bromo-cAMP elevated the endogenous glucocorticoid receptor levels 2-fold and restored responsiveness to glucocorticoids. Second, pretreatment of the cells with cycloheximide also led to acquisition of cellular responsiveness to glucocorticoids. We propose that there exists a "threshold" level of glucocorticoid receptor which is required for responsiveness and that under normal culture conditions, the level of glucocorticoid receptor in 6.10.2 cells is below this threshold. However, glucocorticoid responsiveness can be restored by raising the glucocorticoid receptor level above the threshold with 8-bromo-cAMP or, alternatively, by removing the threshold barrier with cycloheximide.