The transcription factor Cdx2 regulates the intestine-specific expression of human peptide transporter 1 through functional interaction with Sp1
The transcription factor Cdx2 regulates the intestine-specific expression of human peptide transporter 1 through functional interaction with Sp1
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DOI：
10.1016/j.bcp.2006.03.001
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发表时间：
2006-05-28
影响因子：
5.8
通讯作者：
Inui, Ken-ichi
中科院分区：
文献类型：
--
作者：
Shimakura, Jin;Terada, Tomohiro;Inui, Ken-ichi
H+/肽协同转运蛋白1（PEPT 1，SLC 15 A1）定位于肠上皮细胞刷状缘膜，在小分子肽和多种拟肽药物的肠道吸收中起重要作用。我们以前证明，转录因子Sp1的功能作为一个基本的转录调节人PEPT 1。然而，负责PEPT 1的精氨酸特异性表达的因子仍然未知。在本研究中，我们研究了肠道转录因子对PEPT 1基因转录的影响，发现只有Cdx 2显著反式激活PEPT 1启动子。然而，负责这种效果的启动子区域缺乏一个典型的Cdx 2结合序列，而是拥有一些Sp1结合位点。使用Caco-2细胞的体外实验显示（1）Sp1结合位点的突变减弱Cdx 2的作用，（2）Cdx 2和Sp1的共表达协同反式激活PEPT 1启动子，以及（3）Sp1蛋白与Cdx 2蛋白免疫沉淀。这些结果提高了Cdx 2通过与Sp1相互作用调节PEPT 1启动子的可能性。通过测定人组织中Cdx 2和PEPT 1的mRNA水平，显示了Cdx 2在体内对PEPT 1调节的意义。在胃标本中，部分伴有肠上皮化生，PEPT 1和Cdx 2 mRNA水平高度相关。综上所述，本研究表明，Cdx 2在PEPT 1的丝氨酸特异性表达的转录调控中起着关键作用，可能是通过与Sp1的相互作用。(c)2006年爱思唯尔公司All rights reserved.
H+/peptide cotransporter 1 (PEPT1, SLC15A1) localized at the brush-border membranes of intestinal epithelial cells plays important roles in the intestinal absorption of small peptides and a variety of peptidemimetic drugs. We previously demonstrated that transcription factor Sp1 functions as a basal transcriptional regulator of human PEPT1. However, the factor responsible for the intestine-specific expression of PEPT1 remains unknown. In the present study, we investigated the effect of the intestinal transcription factors on the transcription of the PEPT1 gene and found that only Cdx2 markedly trans-activated the PEPT1 promoter. However, the promoter region responsible for this effect lacked a typical Cdx2-binding sequence, but instead, possessed some Sp1-binding sites. in vitro experiments using Caco-2 cells showed that (1) mutation of the Sp1-binding site diminished the effect of Cdx2, (2) co-expression of Cdx2 and Sp1 synergistically trans-activated the PEPT1 promoter and (3) Sp1 protein was immunoprecipitated with Cdx2 protein. These results raise the possibility that Cdx2 modulates the PEPT1 promoter by interaction with Sp1. The significance of Cdx2 in vivo for PEPT1 regulation was shown by the determination of mRNA levels of Cdx2 and PEPT1 in human tissue. in gastric samples, some with intestinal metaplasia, the levels of PEPT1 and Cdx2 mRNA were highly correlated. Taken together, the present study suggests that Cdx2 plays a key role in the transcriptional regulation of the intestine-specific expression of PEPT1, possibly through interaction with Sp1. (c) 2006 Elsevier Inc. All rights reserved.