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Studies of gene expression and physiological roles of cellular retinol-binding protein, type II in the small intestine.

小肠中 II 型细胞视黄醇结合蛋白的基因表达和生理作用的研究。

基本信息

批准号：
11670076
负责人：
TAKASE Sachiko
金额：
$ 2.3万
依托单位：
Siebold University of Nagasaki
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We have reported that the gene expression of cellular retinol-binding protein, type II (CRBPII), which plays important roles in vitamin A uptake, transport and their metabolisms in small intestinal cells, is transcriptionally regulated by dietary fatty acids. In the present study, we further investigated the mechanism of transcriptional regulation of CRBPII gene and the effects on the intestinal vitamin A uptake and metabolisms modulated by fatty acids in the small intestine. We demonstrated in the cotransfection assay that the heterodimer of peroxisome proliferator-activated receptor α (PPARα) and retinoid X receptor (RXR) induced the rat CRBPII gene promoter's transactivity by binding to two putative nuclear receptor response elements (RXRE and RE3) in the presence of PPAR ligands such as linoleic acid and arachidonic acid. In the rat small intestine, not only PPARα but also PPARδ trasncripts was abundantly expressed. Therefore, in the next step, we examined the differences of ligand responsiveness between PPARα and PPARδ in the human small intestine-like cell lines Caco-2. In the one-hybrid assay, broad and great ligand responsiveness was seen in PPARα-mediated transactivity compared to PPARδ. Moreover, PPARα but not PPARδ preferentially interacted with coactivator p300, which was abundantly expressed in the rat small intestine. We further revealed that the increase of small intestinal CRBPII gene expression level by fatty acids led to an increase in the cellular uptake and metabolisms of vitamin A in the small intestine. These results suggest that the expressions of PPAR-dependent genes in the small intestine including CRBPII may be coordinately regulated by PPARα and PPARδ.

我们已经报道，细胞视黄醇结合蛋白，II型（CRBPII），这在小肠细胞中的维生素A的摄取，运输和代谢起着重要作用的基因表达，是由膳食脂肪酸转录调控。本研究进一步探讨了CRBPII基因的转录调控机制以及脂肪酸对小肠维生素A摄取和代谢的影响。我们在共转染实验中证明，过氧化物酶体增殖物激活受体α（PPARα）和维甲酸X受体（RXR）的异源二聚体通过与两个假定的核受体反应元件（RXRE和RE 3）结合诱导大鼠CRBPII基因启动子的反式活性，其中存在PPAR配体，如亚油酸和花生四烯酸。在大鼠小肠中，不仅有大量的PPARα转录本，而且有大量的PPARδ转录本。因此，在下一步中，我们检查了人小细胞肺癌样细胞系Caco-2中PPARα和PPARδ之间的配体反应性差异。在单杂交试验中，与PPARδ相比，在PPARα介导的反式活性中观察到广泛且较大的配体反应性。此外，PPARα而不是PPARδ优先与辅激活因子p300相互作用，该辅激活因子在大鼠小肠中大量表达。我们进一步揭示了脂肪酸增加小肠CRBPII基因表达水平导致小肠中维生素A的细胞摄取和代谢增加。这些结果提示，PPARα和PPARδ可能协同调控包括CRBPII在内的PPAR-dependent基因在小肠的表达。