PROJ 1: ORGANIC ANION TRANSPORTING POLYPEPTIDES IN NUCLEAR RECEPTOR ACTIVATION

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。有机阴离子转运多肽(OATPs)参与多种内生菌和多种药物的吸收、分布和消除。像OATP1B1和OATP1B3这样的多特异性OATP(即接受广泛的结构无关底物的OATP)主要在肝脏表达，在那里它们介导对大量胆汁酸和外源物质的摄取。核受体法尼醇-X-受体(FXR)、孕烷-X-受体(PXR)和维甲酸-X-受体a(RXRA)是配体激活的转录因子，主要在肝脏和小肠表达。当它们被胆汁酸和外源生物等配体激活时，它们调节各种酶和转运体的表达，这些酶和转运体涉及胆固醇和胆汁酸稳态以及药物代谢。该项目的工作假设是，OATP1B1和OATP1B3介导了肝细胞对核受体配体的摄取，这些OATP的故障将影响核受体的激活。在特定目标1中，我们将使用稳定转染的细胞系来表征OATP1B1和OATP1B3相对于核受体配体的底物特异性。在具体目标2中，我们将对OATP1B1和OATP1B3进行详细的定量结构活性关系(QSAR)分析，这将使我们能够预测新的OATP底物和/或抑制剂。在具体目标3中，我们将使用基于细胞的报告系统中的选定配体来确定OATP底物对核受体激活的影响。对OATP1B1和OATP1B3底物特异性的详细表征对于理解OATP的特异性是必不可少的。此外，它还将有助于在转运蛋白水平上了解和预测核受体配体和OATP底物的潜在药物相互作用，如降脂他汀类药物和降糖药物格列酮。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Organic Anion Transporting Polypeptides (OATPs) are involved in absorption, distribution, and elimination of various endobiotics and numerous drugs. Multispecific OATPs (i.e. OATPs, which accept a broad range of structurally unrelated substrates) like OATP1B1 and OATP1B3, are predominantly expressed in liver where they mediate uptake of numerous bile acids and xenobiotics. The nuclear receptors farnesoid-X-receptor (FXR), pregnane-X-receptor (PXR) and retinoid-X-receptor a (RXRa) are ligand activated transcription factors expressed mainly in liver and small intestine. When activated by ligands, like bile acids and xenobiotics, they regulate the expression of various enzymes and transporters involved in cholesterol and bile-acid homeostasis, and drug metabolism. The working hypothesis of this project is that OATP1B1 and OATP1B3 mediate hepatocellular uptake of nuclear-receptor ligands, and that malfunction of these OATPs will affect nuclear-receptor activation. In specific aim 1, we will characterize the substrate specificity of OATP1B1 and OATP1B3 with respect to nuclear-receptor ligands using stably transfected cell lines. In specific aim 2, we will perform a detailed quantitative structure activity relationship (QSAR) analysis for OATP1B1 and OATP1B3, which will allow us to predict new OATP substrates and/or inhibitors. In specific aim 3, we will determine the effect of OATP substrates on nuclear-receptor activation using selected ligands in a cell-based reporter system. A detailed characterization of the substrate specificity of OATP1B1 and OATP1B3 is essential for understanding the specificity of OATPs. Furthermore, it will help to understand and predict potential drug-drug interactions of nuclear-receptor ligands and OATP substrates, such as the lipid lowering statins and the antidiabetic glitazones at the transporter level.