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Dissociation of the AhR/ARNT complex by TGF-β/Smad signaling represses CYP1A1 gene expression and inhibits benze[a]pyrene-mediated cytotoxicity.
Journal of Biological Chemistry ( IF 5.5 ) Pub Date : 2020-07-03 , DOI: 10.1074/jbc.ra120.013596
Naoko Nakano 1 , Nobuo Sakata 1 , Yuki Katsu 1 , Daiki Nochise 1 , Erika Sato 1 , Yuta Takahashi 1 , Saori Yamaguchi 1 , Yoko Haga 1 , Souichi Ikeno 1 , Mitsuyoshi Motizuki 2 , Keigo Sano 1 , Kohei Yamasaki 1 , Keiji Miyazawa 2 , Susumu Itoh 1
Affiliation  

Cytochrome P450 1A1 (CYP1A1) catalyzes the metabolic activation of polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (B[a]P) and is transcriptionally regulated by the aryl hydrocarbon receptor (AhR)/AhR nuclear translocator (ARNT) complex upon exposure to PAHs. Accordingly, inhibition of CYP1A1 expression reduces production of carcinogens from PAHs. Although transcription of the CYP1A1 gene is known to be repressed by transforming growth factor-β (TGF-β), how TGF-β signaling is involved in the suppression of CYP1A1 gene expression has yet to be clarified. In this study, using mammalian cell lines, along with shRNA-mediated gene silencing, CRISPR/Cas9-based genome editing, and reporter gene and quantitative RT-PCR assays, we found that TGF-β signaling dissociates the B[a]P-mediated AhR/ARNT heteromeric complex. Among the examined Smads, Smad family member 3 (Smad3) strongly interacted with both AhR and ARNT via its MH2 domain. Moreover, hypoxia-inducible factor 1α (HIF-1α), which is stabilized upon TGF-β stimulation, also inhibited AhR/ARNT complex formation in the presence of B[a]P. Thus, TGF-β signaling negatively regulated the transcription of the CYP1A1 gene in at least two different ways. Of note, TGF-β abrogated DNA damage in B[a]P-exposed cells. We therefore conclude that TGF-β may protect cells against carcinogenesis because it inhibits CYP1A1-mediated metabolic activation of PAHs as part of its anti-tumorigenic activities.

中文翻译:

通过 TGF-β/Smad 信号传导解离 AhR/ARNT 复合物可抑制 CYP1A1 基因表达并抑制苯[a]芘介导的细胞毒性。

细胞色素 P450 1A1 (CYP1A1) 催化苯并[a]芘 (B[a]P) 等多环芳烃 (PAH) 的代谢活化,并受芳基烃受体 (AhR)/AhR 核转位子 (ARNT) 转录调节接触 PAH 后会变得复杂。因此,抑制 CYP1A1 表达可减少 PAH 致癌物质的产生。尽管已知 CYP1A1 基因的转录会受到转化生长因子-β (TGF-β) 的抑制,但 TGF-β 信号传导如何参与抑制 CYP1A1 基因表达尚不清楚。在这项研究中,使用哺乳动物细胞系,结合 shRNA 介导的基因沉默、基于 CRISPR/Cas9 的基因组编辑以及报告基因和定量 RT-PCR 检测,我们发现 TGF-β 信号传导可解离 B[a]P-介导的 AhR/ARNT 异聚复合物。在接受检查的 Smad 中,Smad 家族成员 3 (Smad3) 通过其 MH2 结构域与 AhR 和 ARNT 强烈相互作用。此外,在 TGF-β 刺激下稳定的缺氧诱导因子 1α (HIF-1α) 也在 B[a]P 存在下抑制 AhR/ARNT 复合物的形成。因此,TGF-β信号传导至少以两种不同的方式负向调节 CYP1A1 基因的转录。值得注意的是,TGF-β 消除了 B[a]P 暴露细胞中的 DNA 损伤。因此,我们得出结论,TGF-β 可以保护细胞免受癌变,因为它抑制 CYP1A1 介导的 PAH 代谢激活,作为其抗肿瘤活性的一部分。因此,TGF-β信号传导至少以两种不同的方式负向调节 CYP1A1 基因的转录。值得注意的是,TGF-β 消除了 B[a]P 暴露细胞中的 DNA 损伤。因此,我们得出结论,TGF-β 可以保护细胞免受癌变,因为它抑制 CYP1A1 介导的 PAH 代谢激活,作为其抗肿瘤活性的一部分。因此,TGF-β信号传导至少以两种不同的方式负向调节 CYP1A1 基因的转录。值得注意的是,TGF-β 消除了 B[a]P 暴露细胞中的 DNA 损伤。因此,我们得出结论,TGF-β 可以保护细胞免受癌变,因为它抑制 CYP1A1 介导的 PAH 代谢激活,作为其抗肿瘤活性的一部分。
更新日期:2020-07-03
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