Ligand Selectivity and Gene Regulation by the Human Aryl Hydrocarbon Receptor in Transgenic Mice
Ligand Selectivity and Gene Regulation by the Human Aryl Hydrocarbon Receptor in Transgenic Mice
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DOI：
10.1124/mol.109.054825
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发表时间：
2009-06-01
影响因子：
3.6
通讯作者：
Perdew, Gary H.
中科院分区：
文献类型：
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作者：
Flaveny, Colin A.;Murray, Iain A.;Perdew, Gary H.
芳烃受体（aryl hydrocarbon receptor， AHR）是一种配体诱导的转录因子，与人类和小鼠的AHR c端序列只有58%的氨基酸序列相同。与小鼠AHR （mAHR）相比，人AHR （hAHR）对典型AHR配体（如2,3,7,8-四氯二苯并-对二恶英）的相对亲和力降低了10倍左右，这主要归因于hAHR配体结合域的氨基酸残基缬氨酸381 （mAHR中的丙氨酸375）。我们研究了不同范围的AHR配体是否会观察到mAHR和hAHR之间10倍的配体结合亲和力差异。为了验证这一假设，我们使用从肝细胞特异性转基因hAHR小鼠和C57BL/6J小鼠中分离的光亲和配体2-叠氮3-[I-125]碘-7,8-二溴二苯并-对二英和肝细胞质进行了配体结合实验。值得注意的是，竞争配体结合实验显示，与mAHR相比，hAHR对某些化合物具有更高的相对亲和力，包括靛玉红[(2Z)-2,3-双吲哚-2,3 (1'H, 1'H)-二酮和槲皮素(2-（3,4二羟基苯基）-3,5,7-三羟基- 4h -铬-4-one]。电泳迁移率转移试验显示，与mAHR相比，靛玉红在转化hAHR方面更有效。与C57BL/6J小鼠肝细胞相比，靛玉红在转基因hAHR小鼠肝细胞中也是一种更有效的Cyp1a1表达诱诱剂。这些观察结果表明，靛玉红是一种有效的hAHR配体，能够选择性地结合并激活hAHR。这些发现表明，mAHR和hAHR配体之间可能存在很大程度的结构差异，并突出了hAHR转基因小鼠作为体内hAHR研究模型的重要性。
The aryl hydrocarbon receptor (AHR) is a ligand-inducible transcription factor that displays interspecies differences with the human and mouse AHR C-terminal region sequences sharing only 58% amino acid sequence identity. Compared with the mouse AHR (mAHR), the human AHR (hAHR) displays similar to 10-fold lower relative affinity for prototypical AHR ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, which has been attributed to the amino acid residue valine 381 (alanine 375 in the mAHR) in the ligand binding domain of the hAHR. We investigated whether the 10-fold difference in ligand-binding affinity between the mAHR and hAHR would be observed with a diverse range of AHR ligands. To test this hypothesis, ligand binding assays were performed using the photo-affinity ligand 2-azido3-[I-125]iodo-7,8-dibromodibenzo-p-dioxin and liver cytosol isolated from hepatocyte-specific transgenic hAHR mice and C57BL/6J mice. It is noteworthy that competitive ligand-binding assays revealed that, compared with the mAHR, the hAHR has a higher relative affinity for certain compounds, including indirubin [(2Z)-2,3-biindole-2,3 (1'H, 1'H)-dione and quercetin (2-(3,4dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one]. Electrophoretic mobility shift assays revealed that indirubin was more efficient at transforming the hAHR compared with the mAHR. Indirubin was also a more potent inducer of Cyp1a1 expression in transgenic hAHR mouse hepatocytes compared with C57BL/6J mouse hepatocytes. These observations suggest that indirubin is a potent hAHR ligand that is able to selectively bind to and activate the hAHR. These discoveries imply that there may be a significant degree of structural divergence between mAHR and hAHR ligands and highlights the importance of the hAHR transgenic mouse as a model to study the hAHR in vivo.