Ionomycin downregulates β-catenin/Tcf signaling in colon cancer cell line
Ionomycin downregulates β-catenin/Tcf signaling in colon cancer cell line
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DOI：
10.1093/carcin/bgi145
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发表时间：
2005-11-01
期刊：
影响因子：
4.7
通讯作者：
Yang, CH
中科院分区：
文献类型：
--
作者：
Park, CH;Hahm, ER;Yang, CH
β-连环蛋白/Tcf信号的功能激活在结直肠癌发生的早期事件中起重要作用。我们研究了离子霉素对结肠癌细胞中β-连环蛋白/Tcf信号转导的影响。报告基因分析表明，离子霉素能有效抑制β-连环蛋白/Tcf信号转导。此外，在瞬时转导结构突变的β-连环蛋白基因的HEK293细胞中，离子霉素对β-连环蛋白/Tcf信号转导的抑制作用表明其抑制机制与β-连环蛋白本身或下游成分有关。为了研究其确切的抑制机制，我们进行了免疫沉淀分析、蛋白质印迹和凝胶迁移率改变分析。因此，我们的数据显示，离子霉素以浓度依赖的方式破坏了β-连环蛋白与Tcf-4的结合，并使细胞核中的β-连环蛋白产物数量减少。此外，离子霉素强烈抑制Tcf复合体与其特定的DNA结合部位的结合。本工作的意义在于，离子霉素是结肠癌细胞中β-连环蛋白/Tcf信号的负调节因子，其抑制机制与核内β-连环蛋白产物减少和Tcf复合体与共识DNA的结合受抑制有关。
Functional activation of beta-catenin/Tcf signaling plays an important role in the early events in colorectal carcinogenesis. We examined the effect of ionomycin against beta-catenin/Tcf signaling in colon cancer cells. Reporter gene assay showed that ionomycin inhibited beta-catenin/Tcf signaling efficiently. In addition, the inhibition of beta-catenin/Tcf signaling by ionomycin in HEK293 cells transiently transfected with a constitutively mutant beta-catenin gene, whose product is not phosphorylated by GSK3 beta, indicates that its inhibitory mechanism is related to beta-catenin itself or downstream components. To investigate the precise inhibitory mechanism, we performed immunoprecipitation analysis, western blot and electrophoretic mobility shift assay. As a result, our data reveal that the association of beta-catenin and Tcf-4 is disrupted and the amount of beta-catenin product in the nucleus is decreased by ionomycin in a concentration-dependent manner. Moreover, ionomycin strongly suppressed the binding of the Tcf complexes to its specific DNA-binding sites. The significance of the current work is that ionomycin is a negative regulator of beta-catenin/Tcf signaling in colon cancer cells and its inhibitory mechanism is related to the decreased nuclear beta-catenin products and to the suppressed binding of Tcf complexes to consensus DNA.