Department of Biochemistry and Molecular Biology, 246 Noble Research Center, Oklahoma State University, Stillwater, Oklahoma 74078, United States.
J Nat Prod. 2011 May 27;74(5):1085-92. doi: 10.1021/np200029q. Epub 2011 Apr 12.
A high-throughput screening of natural product libraries identified (-)-gambogic acid (1), a component of the exudate of Garcinia harburyi, as a potential Hsp90 inhibitor, in addition to the known Hsp90 inhibitor celastrol (2). Subsequent testing established that 1 inhibited cell proliferation, brought about the degradation of Hsp90 client proteins in cultured cells, and induced the expression of Hsp70 and Hsp90, which are hallmarks of Hsp90 inhibition. Gambogic acid also disrupted the interaction of Hsp90, Hsp70, and Cdc37 with the heme-regulated eIF2α kinase (HRI, an Hsp90-dependent client) and blocked the maturation of HRI in vitro. Surface plasmon resonance spectroscopy indicated that 1 bound to the N-terminal domain of Hsp90 with a low micromolar Kd, in a manner that was not competitive with the Hsp90 inhibitor geldanamycin (3). Molecular docking experiments supported the posit that 1 binds Hsp90 at a site distinct from Hsp90s ATP binding pocket. The data obtained have firmly established 1 as a novel Hsp90 inhibitor and have provided evidence of a new site that can be targeted for the development of improved Hsp90 inhibitors.
高通量筛选天然产物文库发现（-）-藤黄酸（1），一种藤黄果实渗出物的成分，是一种潜在的 HSP90 抑制剂，除了已知的 HSP90 抑制剂雷公藤红素（2）。后续的测试表明，1 抑制细胞增殖，导致培养细胞中 HSP90 客户蛋白的降解，并诱导 HSP70 和 HSP90 的表达，这是 HSP90 抑制的标志。藤黄酸还破坏了 HSP90、Hsp70 和 Cdc37 与血红素调节的 eIF2α 激酶（HRI，一种 HSP90 依赖性客户）的相互作用，并在体外阻止 HRI 的成熟。表面等离子体共振光谱表明，1 以低微摩尔 Kd 与 HSP90 的 N 端结构域结合，其方式与 HSP90 抑制剂 17-AAG（3）不具有竞争性。分子对接实验支持 1 结合 HSP90 的位置不同于 HSP90 的 ATP 结合口袋的观点。获得的数据已牢固确立 1 为新型 HSP90 抑制剂，并为可以针对 HSP90 抑制剂的开发的新靶点提供了证据。
