Post-translational modifications of Hsp90 that impact drug efficacy

热休克蛋白90（Hsp 90）是一种分子伴侣， 许多信号传导蛋白的功能，这些蛋白通常被激活，突变或过度表达， 癌细胞以及癌细胞增殖和存活的基础。hsp 90是 一种构象灵活的蛋白质，与一组独特的辅助分子伴侣结合 这取决于氨基末端结合口袋的ATP或ADP占用。核苷酸交换和 Hsp 90自身的ATP水解，在辅分子伴侣的协助下，驱动Hsp 90 分子伴侣机器结合、分子伴侣化和释放客户蛋白。HSP 90的循环 伴侣机器对其功能至关重要。虽然ATP的结合和水解已经 令人信服地参与调节Hsp 90循环，越来越多的证据表明， Hsp 90的翻译后修饰，包括磷酸化、乙酰化和其他修饰。 修改，提供了额外的重叠或平行的监管水平。一个更 完全理解这些不同的蛋白质修饰是如何调节和相互作用的 在细胞水平上相互作用以调节Hsp 90分子伴侣活性对于Hsp 90的表达是至关重要的。 设计新的方法来抑制这种医学上重要的分子靶点。协调 介导不同的Hsp 90翻译后修饰的信号通路是 很有可能理解各种修改之间的串扰无疑将是一个 这是一项艰巨的任务，但这些知识将大大增加我们对Hsp 90 在细胞的复杂环境中调节功能。这些信息可以提供一个独特的 特异性阻断癌细胞中Hsp 90功能的方法，因此将是一种新的方法。 设计Hsp 90抑制剂与 其他分子靶向药物。更深入地了解 翻译后修饰在调节Hsp 90功能中的作用肯定会改善Hsp 90的功能， 这种联合治疗的有效性。热休克蛋白90受到一系列的翻译后 影响其功能的修饰，包括乙酰化。组蛋白去乙酰化酶 HDAC 6的抑制剂和敲低诱导Hsp 90乙酰化并抑制其活性。然而，在这方面， 直接测定热休克蛋白90乙酰化的功能性结果还有待作图 具体的网站。我们已经证明Hsp 90 K294是乙酰化的。突变分析 K294显示其乙酰化状态是客户蛋白的强决定因素， 辅伴侣结合。在酵母中，不能在K294处乙酰化的Hsp 90突变体减少了 与WT或模拟组成型突变体相比， 乙酰化这些数据表明，K294的乙酰化/脱乙酰化起着重要作用 在调节热休克蛋白90分子伴侣循环中的作用。进一步的研究将集中在磷酸化， Hsp 90中的特定氨基酸以及这些翻译后变化对Hsp 90的影响 对抑制性药物的亲和力。

Heat shock protein 90 (Hsp90) is a molecular chaperone required for the stability and function of many signaling proteins that are often activated, mutated or over-expressed in cancer cells and that underly cancer cell proliferation and survival. Hsp90 is a conformationally flexible protein that associates with a distinct set of co-chaperones depending on ATP or ADP occupancy of an amino-terminal binding pocket. Nucleotide exchange and ATP hydrolysis by Hsp90 itself, with the assistance of co-chaperones, drive the Hsp90 chaperone machine to bind, chaperone, and release client proteins. Cycling of the Hsp90 chaperone machine is critical to its function. Although ATP binding and hydrolysis have been convincingly implicated in regulating the Hsp90 cycle, growing evidence suggests that various post-translational modifications of Hsp90, including phosphorylation, acetylation, and other modifications, provide an additional overlapping or parallel level of regulation. A more complete understanding of how these various protein modifications are regulated and interact with each other at the cellular level to modulate Hsp90 chaperone activity is critical to the design of novel approaches to inhibit this medically important molecular target. Coordination of signaling pathways that mediate distinct post-translational modifications of Hsp90 is highly likely. Understanding the cross-talk between various modifications will no doubt be a difficult undertaking, but such knowledge will add greatly to our appreciation of how Hsp90 function is regulated in the complex milieu of the cell. Such information may provide a unique approach to specific interdiction of Hsp90 function in cancer cells and will thus be an important consideration in designing clinical trials of Hsp90 inhibitors in combination with other molecularly targeted drugs. A more thorough understanding of the role that post-translational modifications play in modulating Hsp90 function will certainly improve the effectiveness of such combination therapies. Hsp90 is subject to an array of posttranslational modifications that affect its function, including acetylation. Histone deacetylase (HDAC) inhibitors and knockdown of HDAC6 induce Hsp90 acetylation and inhibit its activity. However, direct determination of the functional consequences of Hsp90 acetylation has awaited mapping of specific sites. We have demonstrated that Hsp90 K294 is acetylated. Mutational analysis of K294 shows that its acetylation status is a strong determinant of client protein and cochaperone binding. In yeast, Hsp90 mutants that cannot be acetylated at K294 have reduced viability and chaperone function compared to WT or to mutants that mimic constitutive acetylation. These data suggest that acetylation/deacetylation of K294 plays an important role in regulating the Hsp90 chaperone cycle. Further studies will focus on phosphorylation of specific amino acids in Hsp90 and of the affect of these post-translational changes on Hsp90 affinity for inhibitory drugs.