Cucurbitacin E

Cucurbitacin E, a widely available plant-derived natural product, is a useful tool to study actin dynamics in cells and actin-based processes such as cytokinesis [1].

In vitro: In assays using pure fluorescently labeled actin, Cucurbitacin E affected depolymerization without affecting the polymerization. It inhibited actin depolymerization at substoichiometric concentrations up to 1:6 cucurbitacin E:actin. Cucurbitacin E specifically bound to F-actin to form a covalent bond at residue Cys257, but not to monomeric actin (G-actin) [1]. In human leukemia HL-60 cells, Cucurbitacin E (3-50 nmol/l) inhibited the growth of HL-60 cells. At high concentrations (1-10 mol/l), Cucurbitacin E induced apoptosis of HL-60 cells and activation of caspase-3, 8 and 9. Jurkat leukemia cells with or without caspase-8 expression were nearly equally sensitive to cucurbitacin E-induced apoptosis[2]. Cucurbitacin E disrupted the actin cytoskeleton. In a series of cucurbitacin analogues, the anti-proliferative activity was correlated with the disruption of the F-actin cytoskeleton directly [3].

References:
[1]. Sorensen P M, Iacob R E, Fritzsche M, et al. The natural product cucurbitacin E inhibits depolymerization of actin filaments[J]. ACS chemical biology, 2012, 7(9): 1502-1508.
[2]. Li Y, Wang R, Ma E, et al. The induction of G2/M cell-cycle arrest and apoptosis by cucurbitacin E is associated with increased phosphorylation of eIF2α in leukemia cells[J]. Anti-cancer drugs, 2010, 21(4): 389-400.
[3]. Duncan K L K, Duncan M D, Alley M C, et al. Cucurbitacin E-induced disruption of the actin and vimentin cytoskeleton in prostate carcinoma cells[J]. Biochemical pharmacology, 1996, 52(10): 1553-1560.