Rho/rhotekin-mediated NF-κB activation confers resistance to apoptosis
Rho/rhotekin-mediated NF-κB activation confers resistance to apoptosis
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DOI：
10.1038/sj.onc.1208106
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发表时间：
2004-11-18
期刊：
影响因子：
8
通讯作者：
Chen, JY
中科院分区：
文献类型：
--
作者：
Liu, CA;Wang, MJ;Chen, JY
Rhotekin （RTKN）是编码Rho效应的基因，在人胃癌（GC）中被证明是过表达的。在本研究中，我们进一步发现RTKN在正常细胞中低水平表达，在许多癌源性细胞系中过表达。研究了RTKN在Rho gtpase介导的细胞凋亡调控通路中作为效应蛋白的作用。通过在低基础水平表达内源性RTKN的细胞中转染和表达RTKN，我们发现RTKN过表达使细胞对血清剥夺或丁酸钠处理诱导的细胞凋亡具有抗性，并且抗性的增加与RTKN水平相关。相反，通过小干扰rna降低RTKN的表达会使细胞对凋亡非常敏感。rtkn介导的抗凋亡作用可被核因子- kappab （NF-kappaB）抑制剂姜黄素或parthenolide阻断，但不能被磷脂酰肌醇3'- oh激酶抑制剂LY294002或MAP激酶抑制剂PD98059阻断。报告基因分析和电泳迁移率转移实验证实，RTKN过表达通过IKKbeta对IkappaB的磷酸化导致NF-kappaB的组成性激活。通过使用RTKN截断突变体，我们发现RTKN介导Rho活性诱导信号通路激活NF-kappaB，同时诱导NF-kappaB抗凋亡基因cIAP-2、BCl-xL、A1和A20的表达。与这些数据一致的是，表达rtkn的细胞对5-氟尿嘧啶和紫杉醇的化学耐药增加，而NF-kappaB抑制剂大大减弱了这种耐药。综上所述，通过过表达RTKN过度激活Rho/RTKN/NF-kappaB信号通路可能通过赋予细胞对凋亡的抗性在胃肿瘤发生中发挥关键作用，该信号通路可能成为治疗胃癌新方法的重要靶点。
Rhotekin ( RTKN), the gene coding for the Rho effector, RTKN, was shown to be overexpressed in human gastric cancer ( GC). In this study, we further showed that RTKN is expressed at a low level in normal cells and is overexpressed in many cancer-derived cell lines. The function of RTKN as an effector protein in Rho GTPase-mediated pathways regulating apoptosis was investigated. By transfection and expression of RTKN in cells that expressed endogenous RTKN at a low basal level, we showed that RTKN overexpression conferred cell resistance to apoptosis induced by serum deprivation or treatment with sodium butyrate, and the increased resistance correlated to the level of RTKN. Conversely, reducing RTKN expression by small interfering RNAs greatly sensitized cells to apoptosis. The RTKN-mediated antiapoptotic effect was blocked by the nuclear factor-kappaB (NF-kappaB) inhibitors, curcumin or parthenolide, but not by the phosphatidylinositol 3'-OH-kinase inhibitor, LY294002, or the MAP kinase inhibitor, PD98059. Reporter gene assays and electrophoretic mobility shift assay confirmed that RTKN overexpression led to constitutive activation of NF-kappaB through the phosphorylation of IkappaB by IKKbeta. By using the RTKN truncation mutants, we showed that RTKN mediated Rho activity eliciting signaling pathway to activate NF-kappaB, with a concomitant induction of expression of the NF-kappaB antiapoptotic genes, cIAP-2, BCl-xL, A1, and A20. Consistent with these data, RTKN-expressing cells showed increased chemoresistance to 5-fluorouracil and paclitaxol, and the resistance was greatly attenuated by NF-kappaB inhibitor. In conclusion, overactivated Rho/RTKN/NF-kappaB signaling pathway through overexpression of RTKN may play a key role in gastric tumorigenesis by conferring cells resistance to apoptosis, and this signaling pathway may serve as an important target for novel therapeutic approaches to the treatment of human GC.