Sauna Zuben E, Andrus Merritt B, Turner Timothy M, Ambudkar Suresh V
Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4254, USA.
Biochemistry. 2004 Mar 2;43(8):2262-71. doi: 10.1021/bi035965k.
Human P-glycoprotein (Pgp) is as an ATP-dependent efflux pump for a variety of chemotherapeutic drugs. The aim of this study is to evaluate whether Pgp modulators can be engineered to exhibit high-affinity binding using polyvalency. Five bivalent homodimeric polyenes based on stipiamide linked with polyethylene glycol ethers in the range of 3-50 A were synthesized and quantitatively characterized for their effect on Pgp function. The stipiamide homodimers displaced [(125)I]iodoarylazidoprazoin (IAAP), an analogue of the Pgp substrate prazosin. A minimal spacer of 11 A is necessary for inhibition of IAAP labeling, beyond which there is an inverse correlation between the length of the spacer and the IC(50) for the displacement of IAAP. ATP hydrolysis by Pgp on the other hand is stimulated by the dimers with spacers of up to 22 A, whereas dimers with longer spacers inhibit ATP hydrolysis. Finally, the homodimers reverse Pgp-mediated drug efflux in intact cells overexpressing Pgp, and 11 A is a threshold beyond which the effectiveness of the homodimers increases exponentially and levels off at 33 A. We demonstrate that dimerization and identification of an optimal spacer length increase by 11-fold the affinity of stipiamide, and this is reflected in the efficacy with which Pgp-mediated drug efflux is reversed. These results suggest that polyvalency could be a useful strategy for the development of more potent Pgp modulators.
人P-糖蛋白（Pgp）是一种依赖ATP的多种化疗药物外排泵。本研究的目的是评估是否可以通过多价性设计Pgp调节剂以表现出高亲和力结合。合成了五种基于 stipiamide 且与聚乙二醇醚连接长度在3至50埃范围内的二价同型二聚体多烯，并对其对Pgp功能的影响进行了定量表征。stipiamide 同型二聚体取代了[(125)I]碘芳基叠氮基普拉唑嗪（IAAP），它是Pgp底物哌唑嗪的类似物。抑制IAAP标记需要11埃的最小间隔，超过此间隔，间隔长度与IAAP取代的IC(50)之间呈负相关。另一方面，Pgp的ATP水解受到间隔长度达22埃的二聚体的刺激，而间隔更长的二聚体则抑制ATP水解。最后，同型二聚体在过表达Pgp的完整细胞中逆转Pgp介导的药物外排，11埃是一个阈值，超过该阈值，同型二聚体的有效性呈指数增加，并在33埃时趋于平稳。我们证明二聚化和确定最佳间隔长度使stipiamide的亲和力提高了11倍，这反映在逆转Pgp介导的药物外排的功效上。这些结果表明，多价性可能是开发更有效的Pgp调节剂的有用策略。
