Cucurbitacin I inhibits cell motility by indirectly interfering with actin dynamics.
Cucurbitacin I inhibits cell motility by indirectly interfering with actin dynamics.
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DOI：
10.1371/journal.pone.0014039
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发表时间：
2010-11-24
期刊：
影响因子：
3.7
通讯作者：
Fenteany G
中科院分区：
文献类型：
--
作者：
Knecht DA;LaFleur RA;Kahsai AW;Argueta CE;Beshir AB;Fenteany G
葫芦素是植物天然产物，通过一种未知的机制抑制Janus kinase2(JAK2)/信号转导和转录激活因子3(STAT3)通路的激活。众所周知，它们还会引起肌动蛋白细胞骨架组织的变化。我们发现葫芦素I有效地抑制伤口闭合过程中马丁达比犬肾(MDCK)细胞片的移动，以及B16-F1小鼠黑色素瘤细胞的随机移动，但对盘基网柄菌阿米巴的移动没有影响。用葫芦素I处理MDCK或B16-F1细胞后，运动很快停止，丝状肌动蛋白聚集体逐渐积累。该化合物的细胞效应类似于用肌动蛋白细丝稳定剂jasplakinolide处理细胞时观察到的效果。然而，我们发现，与茉莉花激动素或蝴蝶素不同，葫芦素I不直接稳定肌动蛋白细丝。在体外肌动蛋白解聚实验中，葫芦素I在抑制细胞迁移的纳摩尔浓度下对肌动蛋白细丝解聚的速度没有影响。在浓度升高时，解聚速率也不受影响，尽管解聚的开始有延迟。因此，葫芦素I的靶标不是肌动蛋白本身，而是与细胞肌动蛋白动力学有关的某些因子。在肌动蛋白解聚中起作用的两个候选蛋白质是肌动蛋白切断蛋白cofilin和明胶蛋白。根据构效关系数据，葫芦素I具有亲电反应性，可能导致其目标蛋白的化学修饰。然而，质谱学没有发现葫芦素I对纯化的丝蛋白或明胶蛋白进行修饰的证据，葫芦素I通过一种独特的间接机制导致肌动蛋白细丝在细胞内积累。此外，葫芦素I与细胞迁移相关的近端靶点不太可能是参与JAK2/STAT3途径激活的同一靶点。
Cucurbitacins are plant natural products that inhibit activation of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway by an unknown mechanism. They are also known to cause changes in the organization of the actin cytoskeleton. We show that cucurbitacin I potently inhibits the migration of Madin-Darby canine kidney (MDCK) cell sheets during wound closure, as well as the random motility of B16-F1 mouse melanoma cells, but has no effect on movement of Dictyostelium discoideum amoebae. Upon treatment of MDCK or B16-F1 cells with cucurbitacin I, there is a very rapid cessation of motility and gradual accumulation of filamentous actin aggregates. The cellular effect of the compound is similar to that observed when cells are treated with the actin filament-stabilizing agent jasplakinolide. However, we found that, unlike jasplakinolide or phallacidin, cucurbitacin I does not directly stabilize actin filaments. In in vitro actin depolymerization experiments, cucurbitacin I had no effect on the rate of actin filament disassembly at the nanomolar concentrations that inhibit cell migration. At elevated concentrations, the depolymerization rate was also unaffected, although there was a delay in the initiation of depolymerization. Therefore, cucurbitacin I targets some factor involved in cellular actin dynamics other than actin itself. Two candidate proteins that play roles in actin depolymerization are the actin-severing proteins cofilin and gelsolin. Cucurbitacin I possesses electrophilic reactivity that may lead to chemical modification of its target protein, as suggested by structure-activity relationship data. However, mass spectrometry revealed no evidence for modification of purified cofilin or gelsolin by cucurbitacin I. Cucurbitacin I results in accumulation of actin filaments in cells by a unique indirect mechanism. Furthermore, the proximal target of cucurbitacin I relevant to cell migration is unlikely to be the same one involved in activation of the JAK2/STAT3 pathway.
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