Communication between multiple drug binding sites on P-glycoprotein
Communication between multiple drug binding sites on P-glycoprotein
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DOI：
10.1124/mol.58.3.624
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发表时间：
2000-09-01
影响因子：
3.6
通讯作者：
Callaghan, R
中科院分区：
文献类型：
--
作者：
Martin, C;Berridge, G;Callaghan, R
P-糖蛋白是三磷酸腺苷结合盒转运蛋白家族中的一员，能够使肿瘤对大量功能和化学上不同的细胞毒性化合物产生耐药性。最近的一些研究表明，P-糖蛋白含有多个药物结合位点，而不是具有广泛底物专一性的单一位点。在本研究中，放射性配基结合技术被用来直接表征药物在P-糖蛋白上的相互作用部位以及这些多个部位是如何相互作用的。所使用的药物被分类为1)底物，已知由P-糖蛋白(例如长春花碱)转运，或2)调节剂，改变P-糖蛋白功能，但本身不由蛋白质(例如XR9576)转运。药物与P-糖蛋白的相互作用要么是竞争性的，要么是在共同的部位，要么是非竞争性的，因此在不同的部位。基于这些数据，我们可以指定P-糖蛋白上至少有四个药物结合部位。这些部位分为两类：转运部位和调节部位，前者是药物跨膜转运的部位，后者则是调节P-糖蛋白功能的部位。然而，有趣的是，一些调节子与P-糖蛋白的作用是在运输部位而不是调控部位。药理学数据还表明，转运和调控位点都能够在高亲和力构象和低亲和力构象之间切换。P-糖蛋白上的多个位置表现出复杂的变构相互作用，药物在一个位置的相互作用使其他位置在高亲和力或低亲和力构象之间切换。根据P-糖蛋白转运机制的模型对这些数据进行了讨论。
P-glycoprotein, a member of the ATP-binding cassette transporter family, is able to confer resistance on tumors against a large number of functionally and chemically distinct cytotoxic compounds. Several recent investigations suggest that P-glycoprotein contains multiple drug binding sites rather than a single site of broad substrate specificity. In the present study, radioligand-binding techniques were used to directly characterize drug interaction sites on P-glycoprotein and how these multiple sites interact. The drugs used were classified as either 1) substrates, which are known to be transported by P-glycoprotein (e.g., vinblastine) or 2) modulators, which alter P-glycoprotein function but are not themselves transported by the protein (e.g., XR9576). Drug interactions with P-glycoprotein were either competitive, at a common site, or noncompetitive, and therefore at distinct sites. Based on these data, we can assign a minimum of four drug binding sites on P-glycoprotein. These sites fall into two categories: transport, at which translocation of drug across the membrane can occur, and regulatory sites, which modify P-glycoprotein function. Intriguingly, however, some modulators interact with P-glycoprotein at a transport site rather than a regulatory site. The pharmacological data also demonstrate that both transport and regulatory sites are able to switch between high- and low-affinity conformations. The multiple sites on P-glycoprotein display complex allosteric interactions through which interaction of drug at one site switches other sites between high- or low-affinity conformations. The data are discussed in terms of a model for the mechanism of transport by P-glycoprotein.