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Role of System LAmino Acid Transporter in Podocyte Cell Biology

系统LA氨基酸转运蛋白在足细胞生物学中的作用

基本信息

批准号：
18590901
负责人：
YAN Kunimasa
金额：
$ 1.54万
依托单位：
Kyorin University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18590901/
关键词：
amino acid transporter mTOR podocyte crescentic glomerulonephritis zebrafish アミノ酸輸送体ネフローゼ

项目摘要

We investigated two system L amino acid transporters, LAT2 and LAT3 in the glomerulus. LAT2 and its functional ligand, 4F2hc, was expressed not only in the proximal tubules but also in the podocytes, however, its localization was revealed in the podocyte cytoplasm, suggesting that LAT2 does not function as amino acid transporter in normal mature podocytes. However, interestingly, LAT2 was dearly expressed in the cellular crescent lesion of human IgA nephropathy and ANCA-related glomerulonephritis. We further studied the role of LAT2 in the process of crescent formation by using rat crescent glomerulonephritis model. Increased phosphorylation of S6 ribosomal protein and 4E-BP1, down stream of mTOR pathway, was clearly demonstrated, preceding increase of LAT2 and 4F2hc expression in cellular crescents. LAT2 cDNA-transfected cell line exhibited predominant phosphorylation of p70S6K and 4E-BP1, which was clearly abrogated in the presence of LAT functional inhibitor. Taken together, we conc … More luded that upregulation of LAT2 and 4F2hc could be involved in the crescent formation via the mechanism by which mTOR signaling activated by growth factors and cytokines accelerated LAT2 and 4F2hc expression in the plasma membrane of glomerular parietal cells that leads secondary induction of mTOR signaling through increase of intra cellular branched-chain amino acids. On the other hand, LAT3 was clearly expressed in apical membrane of podocyte foot processes in human and mouse kidney. Cultured mouse podocytes exhibited system L amino acid transport system. Mouse LAT3 protein and mRNA were upregulated by food starvation. The human fatal kidney revealed LAT3 commencing expressing in the S-shaped body glomeruli Finally, zebrafish morphant lacking lat3 revealed collapsed glomerulus with thickened glomerular basement membrane, despite well-preserved slit diaphragm. Dye-injection experiment indicated the disruption of ultrafiltration barrier in zebrafish lat3 morphant Our data suggest that LAT3 plays a crucial role in glomerular development via the mechanism by which LAT3 transports leucine from the Bowman's space to podocyte cytoplasm, leading to the regulation of the protein synthesis system through mammalian target of rapamycin-2 activation. Less

我们研究了肾小球中的两种系统L氨基酸转运蛋白，LAT 2和LAT 3。LAT 2及其功能性配体4F 2 hc不仅在近端小管中表达，而且在足细胞中表达，然而，其定位在足细胞的细胞质中，表明LAT 2在正常成熟足细胞中不起氨基酸转运蛋白的作用。然而，有趣的是，LAT 2在人类伊加肾病和ANCA相关性肾小球肾炎的细胞新月体病变中高表达。本实验采用大鼠新月体肾炎模型进一步研究了LAT 2在新月体形成过程中的作用。清楚地证明了在细胞新月体中LAT 2和4F 2 hc表达增加之前，mTOR通路下游的S6核糖体蛋白和4 E-BP 1的磷酸化增加。LAT 2 cDNA转染的细胞系表现出p70 S6 K和4 E-BP 1的主要磷酸化，这在LAT功能抑制剂的存在下明显被废除。综合考虑，我们认为 ...更多信息提示LAT 2和4F 2 hc的上调可能参与新月体的形成，其机制是生长因子和细胞因子激活的mTOR信号促进肾小球壁细胞质膜中LAT 2和4F 2 hc的表达，通过增加细胞内支链氨基酸导致mTOR信号的二次诱导。另一方面，LAT 3在人和小鼠肾脏足细胞足突的顶膜中明确表达。培养的小鼠足细胞具有L系统氨基酸转运系统。小鼠LAT 3蛋白和mRNA通过食物饥饿上调。最后，缺乏lat 3的斑马鱼变形体显示出具有增厚的肾小球基底膜的塌陷肾小球，尽管有保存良好的狭缝隔膜。染料注射实验表明，在斑马鱼lat 3 morphant超滤屏障的破坏我们的数据表明，LAT 3通过LAT 3运输亮氨酸从鲍曼氏间隙到足细胞胞质的机制在肾小球发育中起着至关重要的作用，导致蛋白质合成系统的调节，通过哺乳动物靶雷帕霉素-2激活。少