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Molecular cloning and functional expression of kidney-specific organic anionic drug transporters

肾脏特异性有机阴离子药物转运蛋白的分子克隆及功能表达

基本信息

批准号：
09470025
负责人：
ENDOU Hitoshi
金额：
$ 7.17万
依托单位：
Kyorin University School of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Most drugs ingested into the body are metabolized by drug-metabolizing enzymes in the liver, and converted to more polarized hydrophilic compounds. Thus formed drug metabolites contain either negative or positive charge, and more anionic compounds are produced. To eliminate these drug metabolites out of the body, specific membrane proteins named transporters are required.There are two major pathways for drug elimination, one of which is hepatic one through bile and another is renal one to urine. In this investigation, we tried to clone kidney-specific organic anion transporters, and to characterize several isoforms.In 1997, we could succeed to isolate a novel organic anion transporter from rat kidneys and named it OAT (organic anion transporter) 1. Thereafter, three members of OAT family have been identified. OAT2 is liver-specific having different spectrum of transport substrates from OAT1. OAT3 having 536 amino acid residue is expressed in the liver, kidney and brain showing 49% and 39% identities with OAT1 and OAT2, respectively. OAT3 mediates high affinity transport of PAH, ochratoxin A, and estron sulfate. Human OAT4 is expressed in the kidney and placenta and consists of 550 amino acids having identity at 38%〜44% with OAT1〜3. The OAT4 is also multispecific in substrate recognition, like estron sulfate, dehydroepiandrosterone sulfate, and ochratoxin A.Although we could chine 4 isoforms of OAT family, OAT1〜4, molecular mechanisms on substrate recognition remain to be carried out by further investigation. Since OATs reveal weak but significant similarity in their structure with organic cation transporters and carnitine transporters, possible molecular evolution should be clarified among these families. The multi specificity seen in OATs may be originated from relatively simple substrate binding to the transporters and the hypothesis of two important biding sites like hydrophobic moiety and ionic charge needs to be elucidated.

大多数摄入体内的药物都会被肝脏中的药物代谢酶代谢，并转化为更具极性的亲水化合物。由此形成的药物代谢物含有负电荷或正电荷，并产生更多的阴离子化合物。为了将这些药物代谢物排出体外，需要称为转运蛋白的特定膜蛋白。药物消除有两种主要途径，其中一种是通过肝脏通过胆汁排出，另一种是通过肾脏通过尿液排出。在这项研究中，我们试图克隆肾脏特异性的有机阴离子转运蛋白，并对几种亚型进行表征。1997年，我们成功地从大鼠肾脏中分离出一种新型有机阴离子转运蛋白，并将其命名为OAT（有机阴离子转运蛋白）1。此后，OAT家族的三个成员被鉴定出来。 OAT2 是肝脏特异性的，具有与 OAT1 不同的转运底物谱。具有536个氨基酸残基的OAT3在肝、肾和脑中表达，与OAT1和OAT2分别显示49%和39%的同一性。 OAT3 介导 PAH、赭曲霉毒素 A 和硫酸雌酮的高亲和力转运。人OAT4在肾脏和胎盘中表达，由550个氨基酸组成，与OAT1～3具有38%〜44%的同一性。 OAT4在底物识别方面也具有多特异性，如硫酸雌酮、硫酸脱氢表雄酮和赭曲霉毒素A。虽然我们可以分析OAT家族的4种亚型OAT1〜4，但底物识别的分子机制仍有待进一步研究。由于燕麦与有机阳离子转运蛋白和肉碱转运蛋白在结构上显示出微弱但显着的相似性，因此应该澄清这些家族之间可能的分子进化。 OAT 中的多特异性可能源于相对简单的底物与转运蛋白的结合，并且需要阐明两个重要结合位点（如疏水部分和离子电荷）的假设。