Metal Response Element-binding Transcription Factor-1 Is Activated by Degradation of Metallothionein
Metal Response Element-binding Transcription Factor-1 Is Activated by Degradation of Metallothionein
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DOI：
10.1248/jhs.55.72
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发表时间：
2009-02
影响因子：
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通讯作者：
T. Kimura;Fumika Okumura;I. Oguro;T. Nakanishi;T. Sone;M. Isobe;Keiichi Tanaka;N. Itoh
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文献类型：
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作者：
T. Kimura;Fumika Okumura;I. Oguro;T. Nakanishi;T. Sone;M. Isobe;Keiichi Tanaka;N. Itoh
细胞溶质锌结合蛋白，金属硫蛋白（MT），通常是饱和的锌。据认为，锌饱和MT（Zn-MT）作为一个主要的细胞内锌库。金属反应元件结合转录因子-1（MTF-1）在锌离子介导的MT转录中起重要作用。在这里，我们表明Zn-MT的降解激活MTF-1。我们使用电泳迁移率变动分析测量活化的MTF-1。IL-6诱导MT表达并增加MTF-1活性。在MT过表达细胞中未观察到MTF-1活化。MT依赖的MTF-1激活后，观察到MT-过表达细胞与放线菌酮（CHX），蛋白质合成抑制剂。CHX处理提高了蛋白质的降解/合成率。预计MT蛋白质的降解/合成比率的增加会增加不稳定Zn的水平并激活MTF-1。重组MTF-1仅在Zn-MT存在下被H2 O2活化。在原代培养的肝细胞中，氧化应激激活MTF-1 DNA结合活性，但在MT缺陷的肝细胞中不激活。这些结果表明，降解的Zn-MT激活MTF-1，MT锌介导的信号转导中起着重要的作用。
Cytosolic zinc-binding protein, metallothionein (MT), is normally saturated with Zn. It is thought that Zn-saturated MT (Zn-MT) acts as a major intracellular Zn pool. Metal-response element-binding transcription factor-1 (MTF-1) plays an important role in Zn-mediated MT transcription. Here, we showed that degradation of Zn-MT activates MTF-1. We measured activated MTF-1 using an electrophoretic mobility shift assay. Interleukin-6 induced MT expression and increased MTF-1 activity. MTF-1 activation was not observed in MT-overexpressing cells. MT-dependent MTF-1 activation was observed only after treating MT-overexpressing cells with cycloheximide (CHX), a protein synthesis inhibitor. CHX-treatment increased the degradation/synthesis ratio of protein. An increase in the degradation/synthesis ratio for the MT protein is expected to increase the level of labile Zn and activate MTF-1. Recombinant MTF-1 was activated by H2O2 only in the presence of Zn-MT. Oxidative stress activated MTF-1 DNA-binding activity in primary cultured hepatocytes but not in MT-deficient hepatocytes. These findings suggest that degradation of Zn-MT activates MTF-1, and that MT plays an important role in zinc-mediated signal transduction.