Arsenic induces NAD(P)H-quinone oxidoreductase I by disrupting the Nrf2•Keap1•CuI3 complex and recruiting Nrf2•Maf to the antioxidant response element enhancer
Arsenic induces NAD(P)H-quinone oxidoreductase I by disrupting the Nrf2•Keap1•CuI3 complex and recruiting Nrf2•Maf to the antioxidant response element enhancer
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DOI：
10.1074/jbc.m604120200
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发表时间：
2006-08-18
影响因子：
4.8
通讯作者：
Ma, Qiang
中科院分区：
文献类型：
--
作者：
He, Xiaoqing;Chen, Michael G.;Ma, Qiang
普遍存在的有毒类金属砷激发哺乳动物的多效性不良反应和适应性反应。砷的生物靶点目前还很不清楚。我们分析了砷诱导解毒基因NAD（P）H-醌氧化还原酶（Nqo 1）的信号通路。遗传和生化证据表明，诱导需要帽'n'领碱性亮氨酸拉链转录因子Nrf 2和Nqo 1的抗氧化反应元件（ARE）。砷稳定Nrf 2蛋白，通过抑制Keap 1（.）Cul 3依赖的泛素化和Nrf 2的蛋白酶体周转。砷显着抑制Nrf 2的遍在化，但不破坏Nrf 2（。）Keap1（.）Cul 3在细胞质中的结合。在细胞核中，砷，但不是酚类抗氧化剂叔丁基对苯二酚，解离Nrf 2从Keap 1和Cul 3，然后由二聚化的Nrf 2与Maf蛋白（Maf G/Maf K）。染色质免疫沉淀表明，Nrf 2和Maf与内源性Nqo 1 ARE增强子组成型相关。砷大大增加了Nrf 2和Maf的ARE占用。此外，Keap 1被证明是在细胞质中的泛素化和去泛素化的细胞核中的砷的存在下，而不改变蛋白质水平，暗示核-细胞质循环的Keap 1。我们的数据表明，砷激活Nrf 2/Keap 1信号通路通过一个不同的机制，从抗氧化剂，并提出了一个“开关”的Nqo 1转录模型，其中Nrf 2（.）Maf到ARE控制Nqo 1的基础和诱导表达。
The ubiquitous toxic metalloid arsenic elicits pleiotropic adverse and adaptive responses in mammalian species. The biological targets of arsenic are largely unknown at present. We analyzed the signaling pathway for induction of detoxification gene NAD(P)H-quinone oxidoreductase (Nqo1) by arsenic. Genetic and biochemical evidence revealed that induction required cap 'n' collar basic leucine zipper transcription factor Nrf2 and the antioxidant response element (ARE) of Nqo1. Arsenic stabilized Nrf2 protein, extending the t(1/2) of Nrf2 from 21 to 200 min by inhibiting the Keap1(.)Cul3-dependent ubiquitination and proteasomal turnover of Nrf2. Arsenic markedly inhibited the ubiquitination of Nrf2 but did not disrupt the Nrf2(.)Keap1(.)Cul3 association in the cytoplasm. In the nucleus, arsenic, but not phenolic antioxidant tert-butylhydroquinone, dissociated Nrf2 from Keap1 and Cul3 followed by dimerization of Nrf2 with a Maf protein (Maf G/Maf K). Chromatin immunoprecipitation demonstrated that Nrf2 and Maf associated with the endogenous Nqo1 ARE enhancer constitutively. Arsenic substantially increased the ARE occupancy by Nrf2 and Maf. In addition, Keap1 was shown to be ubiquitinated in the cytoplasm and deubiquitinated in the nucleus in the presence of arsenic without changing the protein level, implicating nuclear-cytoplasmic recycling of Keap1. Our data reveal that arsenic activates the Nrf2/Keap1 signaling pathway through a distinct mechanism from that by antioxidants and suggest an "onswitch" model of Nqo1 transcription in which the binding of Nrf2(.)Maf to ARE controls both the basal and inducible expression of Nqo1.