Mechanistic studies on Hsp90 inhibition by ansamycin derivatives
Mechanistic studies on Hsp90 inhibition by ansamycin derivatives
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DOI：
10.1016/j.jmb.2007.06.065
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发表时间：
2007-09-14
影响因子：
5.6
通讯作者：
Jackson, S. E.
中科院分区：
文献类型：
--
作者：
Onuoha, S. C.;Mukund, S. R.;Jackson, S. E.
热休克蛋白 90 (Hsp90) 是一种分子伴侣，是许多客户蛋白成熟和激活所必需的，其中许多客户蛋白与癌症发展有关。安沙霉素家族的天然产物及其衍生物，例如格尔德霉素 (GA)，是众所周知的 Hsp90 必需 ATP 酶活性抑制剂。尽管对安沙霉素衍生物与 Hsp90 ATP 酶结构域的复合物进行了结构研究，但其抑制机制的某些方面仍未得到解决。例如，已知溶液中的GA以具有反式酰胺键的延伸构象存在；然而，它以顺式酰胺键以明显更紧凑的构象与 Hsp90 结合。 GA 及其衍生物已被证明在体外以低微摩尔亲和力与 Hsp90 结合，与这些药物在体内表现出的低纳摩尔抗增殖活性相反。此外，它们对肿瘤细胞表现出选择性。我们研究了 GA 衍生物、17-DMAG 和荧光标记类似物 BDGA 与野生型和突变型 Hsp90 的平衡结合以及缔合和解离动力学。制备突变体是为了测试 ATP 结合位点附近的保守残基可能催化 GA 反式-顺式异构化的假设。我们的结果表明，Hsp90 不会催化 GA 的反式-顺式异构化，这表明在与 Hsp90 结合之前没有异构化步骤。在各种条件下（无论是否存在还原剂）测量 BDGA 实验，证实了最近的研究表明，该药物的还原二氢醌形式与 Hsp90 的结合比非还原醌种类要紧密得多。 (C) 2007 年，爱思唯尔有限公司出版。
Heat shock protein 90 (Hsp90) is a molecular chaperone that is required for the maturation and activation of a number of client proteins, many of which are involved in cancer development. The ansamycin family of natural products and their derivatives, such as geldanamycin (GA), are well-known inhibitors of the essential ATPase activity of Hsp90. Despite structural studies on the complexes of ansamycin derivatives with the ATPase domain of Hsp90, certain aspects of their inhibitory mechanism remain unresolved. For example, it is known that GA in solution exists in an extended conformation with a trans amide bond; however, it binds to Hsp90 in a significantly more compact conformation with a cis amide bond. GA and its derivatives have been shown to bind to Hsp90 with low micromolar affinity in vitro, in contrast to the low nanomolar anti-proliferative activity that these drugs exhibit in vivo. In addition, they show selectivity towards tumour cells. We have studied both the equilibrium binding, and the association and dissociation kinetics of GA derivative, 17-DMAG, and the fluorescently labelled analogue BDGA to both wild-type and mutant Hsp90. The mutants were made in order to test the hypothesis that conserved residues near the ATP-binding site may catalyse the trans-cis isomerisation of GA. Our results show that Hsp90 does not catalyse the trans-cis isomerisation of GA, and suggests that there is no isomerisation step before binding to Hsp90. Experiments with BDGA measured over a wide range of conditions, in the absence and in the presence of reducing agents, confirm recent studies that have suggested that the reduced dihydroquinone form of the drug binds to Hsp90 considerably more tightly than the non-reduced quinone species. (C) 2007 Published by Elsevier Ltd.