The Wnt/β-catenin signaling pathway is a prolific regulator of cell-to-cell communication and gene expression. Canonical Wnt/β-catenin signaling involves partnering of β-catenin with members of the TCF/LEF family of transcription factors (TCF1, TCF3, TCF4, LEF1) to regulate gene expression. IL-6 is a key cytokine involved in inflammation and is particularly a hallmark of inflammation in the brain. Astrocytes, specialized glial cells in the brain, secrete IL-6. How astrocytes regulate IL-6 expression is not entirely clear, although in other cells NFκB and C/EBP pathways play a role. We evaluated here the interface between β-catenin, TCFs/LEF and C/EBP and NF-κB in relation to IL-6 gene regulation in astrocytes. We performed molecular loss and/or gain of function studies of β-catenin, TCF/LEF, NFκB, and C/EBP to assess IL-6 regulation in human astrocytes. Specifically, siRNA mediated target gene knockdown, cDNA over expression of target gene, and pharmacological agents for regulation of target proteins were used. IL-6 levels was evaluated by real time quantitative PCR and ELISA. We also cloned the IL-6 promoter under a firefly luciferase reporter and used bioinformatics, site directed mutagenesis, and chromatin immunoprecipitation to probe the interaction between β-catenin/TCFs/LEFs and IL-6 promoter activity. β-catenin binds to TCF/LEF to inhibits IL-6 while TCFs/LEF induce IL-6 transcription through interaction with ATF-2/SMADs. β-catenin independent of TCFs/LEF positively regulates C/EBP and NF-κB, which in turn activate IL-6 expression. The IL-6 promoter has two putative regions for TCFs/LEF binding, a proximal site located at -91 nt and a distal site at -948 nt from the transcription start site, both required for TCF/LEF induction of IL-6 independent of β-catenin. IL-6 regulation in human astrocytes engages a discordant interaction between β-catenin and TCF/LEF. These findings are intriguing given that no role for β-catenin nor TCFs/LEF to date is associated with IL-6 regulation and suggest that β-catenin expression in astrocytes is a critical regulator of anti-inflammatory responses and its disruption can potentially mediate persistent neuroinflammation.

中文翻译：

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β-Catenin 和 TCFs/LEF 信号不一致地调节星形胶质细胞中的 IL-6 表达。

Wnt/β-catenin 信号通路是细胞间通讯和基因表达的多产调节剂。典型的 Wnt/β-catenin 信号传导涉及 β-catenin 与 TCF/LEF 转录因子家族成员（TCF1、TCF3、TCF4、LEF1）的合作，以调节基因表达。IL-6 是参与炎症的关键细胞因子，尤其是大脑炎症的标志。星形胶质细胞是大脑中的特殊神经胶质细胞，会分泌 IL-6。星形胶质细胞如何调节 IL-6 表达尚不完全清楚，尽管在其他细胞中 NFκB 和 C/EBP 通路起作用。我们在这里评估了 β-catenin、TCFs/LEF 和 C/EBP 和 NF-κB 之间的界面与星形胶质细胞中 IL-6 基因调控的关系。我们对 β-catenin、TCF/LEF、NFκB、和 C/EBP 以评估人星形胶质细胞中的 IL-6 调节。具体而言，使用siRNA介导的靶基因敲低、靶基因的cDNA过表达和用于调节靶蛋白的药理学试剂。通过实时定量 PCR 和 ELISA 评估 IL-6 水平。我们还在萤火虫荧光素酶报告基因下克隆了 IL-6 启动子，并使用生物信息学、定点诱变和染色质免疫沉淀来探测 β-连环蛋白/TCF/LEF 与 IL-6 启动子活性之间的相互作用。β-catenin 与 TCF/LEF 结合以抑制 IL-6，而 TCFs/LEF 通过与 ATF-2/SMADs 相互作用诱导 IL-6 转录。不依赖 TCF/LEF 的 β-catenin 正向调节 C/EBP 和 NF-κB，进而激活 IL-6 表达。IL-6 启动子有两个用于 TCF/LEF 结合的推定区域，位于 -91 nt 的近端位点和距转录起始位点 -948 nt 的远端位点，两者都是 TCF/LEF 诱导 IL-6 所必需的，而与 β-catenin 无关。人星形胶质细胞中的 IL-6 调节涉及 β-连环蛋白和 TCF/LEF 之间不一致的相互作用。这些发现很有趣，因为迄今为止 β-连环蛋白和 TCF/LEF 的作用都与 IL-6 调节无关，并且表明星形胶质细胞中的 β-连环蛋白表达是抗炎反应的关键调节因子，其破坏可能介导持续性神经炎症。