Andrographolide derivatives inhibit guanine nucleotide exchange and abrogate oncogenic Ras function
Andrographolide derivatives inhibit guanine nucleotide exchange and abrogate oncogenic Ras function
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DOI：
10.1073/pnas.1300016110
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发表时间：
2013-06-18
影响因子：
11.1
通讯作者：
Gorfe, Alemayehu A.
中科院分区：
文献类型：
--
作者：
Hocker, Harrison J.;Cho, Kwang-Jin;Gorfe, Alemayehu A.
致癌突变大鼠肉瘤（Ras）蛋白的异常信号传导发生在类似于15%的所有人类肿瘤中，但小分子对Ras的直接抑制仍然难以捉摸。最近，已经发现了几种小分子配体直接结合Ras并通过干扰交换因子结合来抑制其功能。然而，目前还不清楚这些配体是否或如何导致药物对组成型活性致癌突变体Ras起作用。使用基于动力学的口袋识别方案、系综对接和创新的基于细胞的测定，我们在这里表明，穿心莲内酯（AGP）--一种从穿心莲中分离出的双环二萜类内酯--及其亚苄基衍生物与Kirsten-Ras上的瞬时口袋结合（K-Ras）并抑制GDP-GTP交换。正如预期的交换因子结合的抑制剂，AGP衍生物减少GTP负载的野生型K-Ras响应于急性EGF刺激与伴随的MAPK活化减少。然而，值得注意的是，AGP衍生物的长期治疗也降低了致癌突变体K-RasG 12 V的GTP负载和信号传递。总之，我们的计算和细胞生物学结果的组合分析表明，AGP衍生物直接结合Ras，阻断GDP-GTP交换，并抑制野生型和致癌K-Ras信号传导。重要的是，我们的研究结果不仅表明，核苷酸交换因子所需的致癌Ras信号，但也表明，抑制核苷酸交换是一种有效的方法来废除致癌突变体Ras的功能。
Aberrant signaling by oncogenic mutant rat sarcoma (Ras) proteins occurs in similar to 15% of all human tumors, yet direct inhibition of Ras by small molecules has remained elusive. Recently, several small-molecule ligands have been discovered that directly bind Ras and inhibit its function by interfering with exchange factor binding. However, it is unclear whether, or how, these ligands could lead to drugs that act against constitutively active oncogenic mutant Ras. Using a dynamics-based pocket identification scheme, ensemble docking, and innovative cell-based assays, here we show that andrographolide (AGP)-a bicyclic diterpenoid lactone isolated from Andrographis paniculata-and its benzylidene derivatives bind to transient pockets on Kirsten-Ras (K-Ras) and inhibit GDP-GTP exchange. As expected for inhibitors of exchange factor binding, AGP derivatives reduced GTP loading of wild-type K-Ras in response to acute EGF stimulation with a concomitant reduction in MAPK activation. Remarkably, however, prolonged treatment with AGP derivatives also reduced GTP loading of, and signal transmission by, oncogenic mutant K-RasG12V. In sum, the combined analysis of our computational and cell biology results show that AGP derivatives directly bind Ras, block GDP-GTP exchange, and inhibit both wild-type and oncogenic K-Ras signaling. Importantly, our findings not only show that nucleotide exchange factors are required for oncogenic Ras signaling but also demonstrate that inhibiting nucleotide exchange is a valid approach to abrogating the function of oncogenic mutant Ras.