PROX1 suppresses vitamin K-induced transcriptional activity of steroid and xenobiotic receptor
PROX1 suppresses vitamin K-induced transcriptional activity of steroid and xenobiotic receptor
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DOI：
10.1111/j.1365-2443.2011.01551.x
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发表时间：
2011-11-01
期刊：
影响因子：
2.1
通讯作者：
Inoue, Satoshi
中科院分区：
文献类型：
--
作者：
Azuma, Kotaro;Urano, Tomohiko;Inoue, Satoshi
类固醇和外源性受体（SXR）属于核受体超家族。结果表明，二级胆汁酸如石胆酸和几种化合物如利福平可作为该受体的配体。最近，我们已经证明，维生素K2也可以作为SXR的配体，维生素K2激活SXR抑制肝细胞癌（HCC）细胞的增殖和运动。为了分析SXR在HCC细胞中的功能，我们在HCC细胞系HepG 2细胞中过表达外源性SXR，其用FLAG和HA双标记，并通过免疫沉淀从这些细胞的核提取物中纯化SXR结合分子。通过TOF-MS分析鉴定了几种结合分子。SXR结合分子之一是转录因子PROX 1。我们证实了PROX 1和SXR在HEK 293细胞中的相互作用。然后，我们已经表明，SXR的AF 2结构域是必要的结合PROX 1。通过对SXR靶基因的启动子分析，我们进一步证明了PROX 1负调控SXR的转录活性。这些结果表明，PROX 1可以负调控SXR信号在一些肿瘤细胞，如肝癌细胞，其中SXR和PROX 1都表达。
Steroid and Xenobiotic Receptor (SXR) belongs to nuclear receptor superfamily. It was shown that secondary bile acids such as lithocholic acid and several chemical compounds such as rifampicin could be ligands for this receptor. Recently, we have demonstrated that vitamin K2 also serves as a ligand for SXR and activation of SXR by vitamin K2 suppressed proliferation and motility of hepatocellular carcinoma (HCC) cells. To analyze function of SXR in HCC cells, we overexpressed exogenous SXR double-tagged with FLAG and HA in a HCC cell line, HepG2 cells, and purified SXR-binding molecules by immunoprecipitation from the nuclear extracts of these cells. Several binding molecules were identified by TOF-MS analyses. One of the SXR-binding molecules was a transcription factor PROX1. We confirmed the interaction of PROX1 and SXR in HEK293 cells. Then, we have shown that AF2 domain of SXR is necessary for binding with PROX1. We further demonstrated that PROX1 negatively regulated the transcriptional activity of SXR by promoter analyses of SXR target gene. These results suggest that PROX1 could negatively regulate SXR signals in some tumor cells, such as HCC cells, where both SXR and PROX1 are expressed.