Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
ACS Chem Biol. 2012 Sep 21;7(9):1502-8. doi: 10.1021/cb300254s. Epub 2012 Jul 9.
Although small molecule actin modulators have been widely used as research tools, only one cell-permeable small molecule inhibitor of actin depolymerization (jasplakinolide) is commercially available. We report that the natural product cucurbitacin E inhibits actin depolymerization and show that its mechanism of action is different from jasplakinolide. In assays using pure fluorescently labeled actin, cucurbitacin E specifically affects depolymerization without affecting polymerization. It inhibits actin depolymerization at substoichiometric concentrations up to 1:6 cucurbitacin E:actin. Cucurbitacin E specifically binds to filamentous actin (F-actin) forming a covalent bond at residue Cys257, but not to monomeric actin (G-actin). On the basis of its compatibility with phalloidin staining, we show that cucurbitacin E occupies a different binding site on actin filaments. Using loss of fluorescence after localized photoactivation, we found that cucurbitacin E inhibits actin depolymerization in live cells. Cucurbitacin E is a widely available plant-derived natural product, making it a useful tool to study actin dynamics in cells and actin-based processes such as cytokinesis.
虽然小分子肌动蛋白调节剂已被广泛用作研究工具，但只有一种可渗透细胞的肌动蛋白解聚小分子抑制剂（jasplakinolide）可商业化获得。我们报告称，天然产物葫芦素 E 可抑制肌动蛋白解聚，并表明其作用机制与 jasplakinolide 不同。在使用纯荧光标记肌动蛋白的测定中，葫芦素 E 特异性地影响解聚而不影响聚合。它在亚化学计量浓度下抑制肌动蛋白解聚，达到 1:6 葫芦素 E:肌动蛋白。葫芦素 E 特异性地结合丝状肌动蛋白（F-actin），在残基 Cys257 处形成共价键，但不与单体肌动蛋白（G-actin）结合。根据其与鬼笔环肽染色的兼容性，我们表明葫芦素 E 在肌动蛋白丝上占据不同的结合位点。使用局部光活化后荧光损失，我们发现葫芦素 E 抑制活细胞中的肌动蛋白解聚。葫芦素 E 是一种广泛可用的植物源性天然产物，使其成为研究细胞中肌动蛋白动力学和肌动蛋白为基础的过程（如胞质分裂）的有用工具。
