Janus kinase 2-A novel negative regulator of estrogen receptor α function
Janus kinase 2-A novel negative regulator of estrogen receptor α function
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DOI：
10.1016/j.cellsig.2011.08.016
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发表时间：
2012-01-01
影响因子：
4.8
通讯作者：
Mayer, Doris
中科院分区：
文献类型：
--
作者：
Gupta, Nibedita;Grebhardt, Sina;Mayer, Doris
雌激素受体 α (ER α.) 作为转录因子，调节多种细胞活动以响应 17 β-雌二醇 (E2)。 ER α 转录活性的调节非常复杂且尚未完全了解。在这方面，最近的研究强调了某些细胞蛋白激酶的重要性。为了鉴定调节 ER α 活性的新型蛋白激酶，我们在 ER α 阳性乳腺癌细胞系中结合荧光素酶报告基因测定进行了高通量 siRNA 筛选。在绝大多数潜在的正调节因子中，我们发现 Janus 激酶 2 (JAK2)（非受体酪氨酸激酶 Janus 激酶家族的成员）对 E2 诱导的荧光素酶活性具有负调节作用。此外，JAK2 的沉默导致内源 ER α 靶基因 pS2 和 GREB1 的表达增加。为了了解 JAK2 介导的 ER α 转录活性调节机制，我们发现 JAK2 负向调节 ER α 蛋白水平。基因表达分析显示JAK2对ERαmRNA水平没有显着影响。随后，分析了 JAK2 在调节 ER α 蛋白降解中的作用。溶酶体的抑制不会改变 JAK2 介导的 ER α 下调。相反，使用蛋白酶体抑制剂 MG132 和乳胞素，我们证明 JAK2 通过泛素-蛋白酶体途径控制 ER α 蛋白稳定性。与 JAK2 相比，在乳腺中表达的 JAK 家族的其他两个成员（JAK1 和 TYK2）对 ER α 功能没有影响。此外，我们发现延长 E2 治疗会上调 JAK2 mRNA 和蛋白质水平。这些结果表明 JAK2 在乳腺癌细胞中对 ERa 活性和蛋白质有一种新的负调节，并表明潜在的新交叉。 (C) 2011 Elsevier Inc. 保留所有权利。
Estrogen receptor alpha (ER alpha.) functions as a transcription factor to regulate a wide range of cellular activities in response to 17 beta-estradiol (E2). The regulation of ER alpha transcriptional activity is highly complex and not yet fully understood. In this respect, recent studies have highlighted the importance of certain cellular protein kinases. To identify novel protein kinases regulating ER alpha activity, we performed a high-throughput siRNA screening in combination with a luciferase reporter assay in an ER alpha positive breast cancer cell line. Among the vast majority of potential positive regulators, we found Janus kinase 2 (JAK2), a member of the Janus kinase family of non-receptor tyrosine kinases, to have a negative regulatory effect on E2 induced luciferase activity. In addition, silencing of JAK2 resulted in increased expression of endogenous ER alpha target genes, pS2 and GREB1. In an attempt to understand the mechanism underlying JAK2 mediated regulation of ER alpha transcriptional activity, we found that JAK2 negatively regulates ER alpha protein level. Gene expression analysis revealed no significant influence of JAK2 on ER alpha mRNA level. Subsequently, a role of JAK2 in regulating ER alpha protein degradation was analyzed. Inhibition of the lysosome did not alter JAK2 mediated downregulation of ER alpha. In contrast, using proteasome inhibitors MG132 and lactacystin, we demonstrated that JAK2 governs ER alpha protein stability via the ubiquitin-proteasome pathway. In contrast to JAK2, the two other members of the JAK family expressed in the breast (JAK1 and TYK2) had no influence on ER alpha function. In addition, we found that prolonged E2 treatment upregulates JAK2 mRNA and protein levels. These results suggest a novel negative regulation of ERa activity and protein by JAK2 in breast cancer cells and indicate a potential new cross-talk. (C) 2011 Elsevier Inc. All rights reserved.