The benzoquinone ansamycins inhibit the ATPase activity of the 90-kDa heat shock protein (Hsp90), disrupting the function of numerous client proteins involved in oncogenesis. In this study, we examine the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the metabolism of trans - and cis -amide isomers of the benzoquinone ansamycins and their mechanism of Hsp90 inhibition. Inhibition of purified human Hsp90 by a series of benzoquinone ansamycins was examined in the presence and absence of NQO1, and their relative rate of NQO1-mediated reduction was determined. Computational-based molecular docking simulations indicated that the trans - but not the cis -amide isomers of the benzoquinone ansamycins could be accommodated by the NQO1 active site, and the ranking order of binding energies correlated with the relative reduction rate using purified human NQO1. The trans-cis isomerization of the benzoquinone ansamycins in Hsp90 inhibition has been disputed in recent reports. Previous computational studies have used the closed or cocrystallized Hsp90 structures in an attempt to explore this isomerization step; however, we have successfully docked both the trans - and cis -amide isomers of the benzoquinone ansamycins into the open Hsp90 structure. The results of these studies indicate that both trans - and cis -amide isomers of the hydroquinone ansamycins exhibited increased binding affinity for Hsp90 relative to their parent quinones. Our data support a mechanism in which trans - rather than cis -amide forms of benzoquinone ansamycins are metabolized by NQO1 to hydroquinone ansamycins and that Hsp90-mediated trans-cis isomerization via tautomerization plays an important role in subsequent Hsp90 inhibition.
苯
醌类ansamycins抑制90-kDa热休克蛋白(Hsp90)的
ATP酶活性,从而破坏了许多参与肿瘤发生的客户蛋白的功能。在这项研究中,我们考察了
NAD(P)H:quinone 氧化还原酶 1 (NQO1) 在苯醌ansamycins 的反式和顺式酰胺异构体代谢中的作用及其抑制 Hsp90 的机制。在 NQO1 存在和不存在的情况下,考察了一系列苯醌ansamycins 对纯化的人 Hsp90 的抑制作用,并测定了它们在 NQO1 介导下的相对还原率。基于计算的分子对接模拟表明,NQO1 活性位点可以容纳苯醌ansamycins 的反式(而非顺式)酰胺异构体,并且结合能的排序与使用纯化的人类 NQO1 的相对还原率相关。最近的报告
对苯醌ansamycins在抑制Hsp90过程中的反式-顺式异构化提出了争议。以前的计算研究使用封闭的或共晶的 Hsp90 结构来尝试探索这一异构化步骤;然而,我们已经成功地将苯醌ansamycins 的反式和顺式酰胺异构体对接到开放的 Hsp90 结构中。这些研究结果表明,与母体
醌类化合物相比,反式和顺式苯醌
氨酰胺异构体与 Hsp90 的结合亲和力都有所提高。我们的数据支持这样一种机制,即苯醌
氨酪酸的反式而非顺式酰胺形式通过 NQO1 代谢为
对苯二酚氨酪酸,而 Hsp90 介导的反式-顺式异构体通过同分异构在随后的 Hsp90 抑制中发挥重要作用。