Inhibition of transcription factor NF-κB signaling proteins IKKβ and p65 through specific cysteine residues by epoxyquinone A monomer:: Correlation with its anti-cancer cell growth activity
Inhibition of transcription factor NF-κB signaling proteins IKKβ and p65 through specific cysteine residues by epoxyquinone A monomer:: Correlation with its anti-cancer cell growth activity
复制标题
DOI：
10.1016/j.bcp.2005.11.013
复制
发表时间：
2006-02-28
影响因子：
5.8
通讯作者：
Gilmore, TD
中科院分区：
文献类型：
--
作者：
Liang, MC;Bardhan, S;Gilmore, TD
转录因子NF-κ B在许多人类慢性炎性疾病和癌症中具有组成性活性。环氧醌A单体（EqM）是天然产物环氧醌A的合成衍生物，先前已显示为肿瘤坏死因子-α（TNF-α）诱导的NF-κ B活化的有效抑制剂，但EqM抑制NF-κ B活化的机制尚不清楚。在本报告中，我们发现EqM通过抑制两个分子靶点阻断NF-κ B的活化：I κ B激酶IKK β和NF-κ B亚基p65。EqM通过靶向IKK β抑制TNF-α诱导的I κ B α磷酸化和降解，并且IKK β激活环中Cys 179的丙氨酸取代使其对EqM介导的抑制具有抗性。EqM还直接抑制p65的DNA结合，但不抑制p50;此外，用Ser取代p65中的Cys 38消除了EqM介导的DNA结合抑制。用还原剂二硫苏糖醇预处理细胞密切依赖性地减少EqM介导的NF-κ B抑制，进一步表明EqM直接修饰蛋白质靶中Cys残基的巯基。EqM的环外烯烃的修饰显著降低了EqM抑制NF-κ B活化的能力。在人SUDHL-4淋巴瘤细胞系中，EqM抑制增殖和NF-κ B DNA结合，并激活caspase-3活性。EqM还有效抑制NCI肿瘤细胞面板中的人类白血病、肾癌和结肠癌细胞系的生长。在六种结肠癌细胞系中，具有低量的组成型NF-κ B DNA结合活性的那些通常对EqM的生长抑制更敏感。综上所述，这些结果表明EqM通过涉及在信号传导途径的多个步骤抑制NF-κ B活性的机制抑制肿瘤细胞的生长并诱导细胞死亡。(c)2005年爱思唯尔公司All rights reserved.
Transcription factor NF-kappa B is constitutively active in many human chronic inflammatory diseases and cancers. Epoxyquinone A monomer (EqM), a synthetic derivative of the natural product epoxyquinol A, has previously been shown to be a potent inhibitor of tumor necrosis factor-a (TNF-alpha)-induced activation of NF-kappa B, but the mechanism by which EqM inhibits NF-kappa B activation was not known. In this report, we show that EqM blocks activation of NF-kappa B by inhibiting two molecular targets: I kappa B kinase IKK beta and NF-kappa B subunit p65. EqM inhibits TNF-alpha-induced I kappa B alpha phosphorylation and degradation by targeting IKK beta, and an alanine substitution for Cys179 in the activation loop of IKK beta makes it resistant to EqM-mediated inhibition. EqM also directly inhibits DNA binding by p65, but not p50; moreover, replacement of Cys38 in p65 with Ser abolishes EqM-mediated inhibition of DNA binding. Pretreatment of cells with reducing agent dithiothreitol close-dependently reduces EqM-mediated inhibition of NF-kappa B, further suggesting that EqM directly modifies the thiol group of Cys residues in protein targets. Modifications of the exocyclic alkene of EqM substantially reduce EqM's ability to inhibit NF-kappa B activation. In the human SUDHL-4 lymphoma cell line, EqM inhibits both proliferation and NF-kappa B DNA binding, and activates caspase-3 activity. EqM also effectively inhibits the growth of human leukemia, kidney, and colon cancer cell lines in the NCI's tumor cell panel. Among six colon cancer cell lines, those with low amounts of constitutive NF-kappa B DNA-binding activity are generally more sensitive to growth inhibition by EqM. Taken together, these results suggest that EqM inhibits growth and induces cell death in tumor cells through a mechanism that involves inhibition of NF-kappa B activity at multiple steps in the signaling pathway. (c) 2005 Elsevier Inc. All rights reserved.