Molecular Characterization of Hepatic Organic Anion Transporting Polypeptides

描述(由申请人提供)：发生在药物转运体水平上的药物-药物相互作用可能会产生意想不到的严重副作用。有机阴离子转运多肽(OATP超家族)的肝脏药物转运体转运大量的内源和外源药物，因此在药物处置中起着重要作用。两个肝脏特异的OATP1B1和OATP1B3具有广泛和重叠的底物特异性，但也运输不同和独特的底物。然而，关于OATP如何识别和运输不同的化合物，目前还知之甚少。到目前为止，还不可能准确地预测一种化合物是否会成为底物，以及是否可能发生药物相互作用。由于OATP是药物相互作用的潜在部位，可能导致严重的不良反应，这些未知因素应该得到澄清。因此，拟议研究的长期目标是了解、预测和预防与OATP相关的药物-药物相互作用。这一特殊应用的目的是确定肝脏特异性转运蛋白OATP1B1和OATP1B3的多特异性的分子基础。本研究的中心假设是OATP1B1和OATP1B3通过多个转运/结合位点转运不同的底物。这些转运蛋白的故障(抑制、上调或下调以及基因多态性)将影响药物的生物利用度，并可能导致不良药物作用。我们计划验证我们的中心假设，并实现这一应用的总体目标，有以下四个具体目标：1)表征OATP1B1和OATP1B3的底物特异性，重点是核受体配体；2)对OATP1B1和OATP1B3进行详细的3D-QSAR分析；3)确定膜拓扑；以及4)使用嵌合体和定点突变确定OATP1B1和OATP1B3的底物结合位点。详细了解肝脏特异性药物转运蛋白OATP1B1和OATP1B3是如何识别和转运不同底物的，将有助于预测和预防药物与药物的不良相互作用，并开发针对肝脏的新的治疗化合物。一旦有了这些知识，就有可能开发出更安全的药物，从而减少住院人数。

DESCRIPTION (provided by applicant): Drug-drug interactions that occur at the level of drug transporters can have unexpected and severe side effects. The hepatic drug transporters of the organic anion transporting polypeptide (OATP) superfamily transport numerous endo- and xenobiotics (drugs) and are therefore important for drug disposition. The two liver specific OATP1B1 and OATP1B3 have broad and overlapping substrate specificity, but also transport distinct and unique substrates. However, there is nothing known about how OATPs recognize and transport different compounds. So far it is impossible to make exact predictions on whether a compound will be a substrate or not, and whether a possible drug-interaction might occur. Because OATPs are potential sites of drug-drug interactions that can lead to severe adverse effects, these unknowns should be clarified. Therefore, the long-term goal of the proposed studies is to understand, predict and prevent OATP related drug-drug interactions. The objective of this particular application is to determine the molecular basis of the polyspecificity of the liver-specific transporters, OATP1B1 and OATP1B3. The central hypothesis for the proposed research is that different substrates are transported by OATP1B1 and OATP1B3 using multiple transport/binding sites. Malfunction of these transporters (inhibition, up- or down-regulation, and polymorphisms) will affect drug bioavailability and can lead to adverse drug actions. We plan to test our central hypothesis and accomplish the overall objective of this application with the following four specific aims: 1) Characterize the substrate specificity of OATP1B1 and OATP1B3 with emphasis on nuclear receptor ligands; 2) Perform a detailed 3D-QSAR analysis for OATP1B1 and OATP1B3; 3) Determine the membrane topology; and 4) Identify the substrate binding sites of OATP1B1 and OATP1B3 using chimeras and site directed mutagenesis. A detailed understanding on how the liver specific drug transporters OATP1B1 and OATP1B3 recognize and transport their different substrates will help to predict and prevent adverse drug-drug interactions and to develop new therapeutic compounds to target the liver. Once this knowledge is available, there is the promise that it will be possible to develop safer medication which will result in less hospitalizations.