Dietary antioxidant curcumin inhibits microtubule assembly through tubulin binding

Abstract

Curcumin, a component of turmeric, has potent antitumor activity against several tumor types. However, its molecular target and mechanism of antiproliferative activity are not clear. Here, we identified curcumin as a novel antimicrotubule agent. We have examined the effects of curcumin on cellular microtubules and on reconstituted microtubules in vitro. Curcumin inhibited HeLa and MCF‐7 cell proliferation in a concentration‐dependent manner with IC50 of 13.8 ± 0.7 µm and 12 ± 0.6 µm, respectively. At higher inhibitory concentrations (> 10 µm), curcumin induced significant depolymerization of interphase microtubules and mitotic spindle microtubules of HeLa and MCF‐7 cells. However, at low inhibitory concentrations there were minimal effects on cellular microtubules. It disrupted microtubule assembly in vitro, reduced GTPase activity, and induced tubulin aggregation. Curcumin bound to tubulin at a single site with a dissociation constant of 2.4 ± 0.4 µm and the binding of curcumin to tubulin induced conformational changes in tubulin. Colchicine and podophyllotoxin partly inhibited the binding of curcumin to tubulin, while vinblastine had no effect on the curcumin–tubulin interactions. The data together suggested that curcumin may inhibit cancer cells proliferation by perturbing microtubule assembly dynamics and may be used to develop efficacious curcumin analogues for cancer chemotherapy.

EF24, a novel curcumin analog, disrupts the microtubule cytoskeleton and inhibits HIF-1

“…We were unable to reproduce the apparent inhibition of tubulin assembly by curcumin reported by Gupta et al 30 Possible causes for our different results could be the use of different reaction conditions, different tubulin preparations, the methodology used to monitor turbidity development, or, perhaps most likely, by other curcuminoids in the material used by Gupta et al 32 Taken together, the cellular and in vitro effects of EF24 on the microtubule cytoskeleton suggest that this compound may affect cellular microtubules indirectly by modulating pathways that influence microtubule formation and/or stability. Nevertheless, the EF24-induced microtubule stabilization in cells may result in the downstream inhibition of HIF-1α and β levels, similar to the effects of the known microtubule inhibitors.…”

Curcumin derivatives: Molecular basis of their anti-cancer activity

“…The effects of Curcumin on cell cycle arrest are associated with structural changes of tubulin, followed by abnormal chromosome segregration [2,3]. To determine whether bDMC and DAC exert an effect on mitotic spindle organization, HCT116 cells treated for 24 hours with IC 50 doses were fixed and processed for immunofluorescence microscopy using anti-tubulin antibody and HOECHST to detect nuclear morphology.…”

“…In fact, many microtubule-targeting agents (MITs) have been discovered by screening natural products and are currently in clinical trials. Curcumin, a common flavoring agent in the spice turmeric, perturbs microtubule assembly dynamics through tubulin binding, which results in its conformational changes [2]. Significant depolymerization of interphase microtubules and mitotic spindle microtubules have been observed after Curcumin incubation of HeLa, MCF-7, HT-29 and HCT-15 cells, thus leading to a mitotic arrest [2][3][4].…”

Induction of apoptosis through tubulin inhibition in human cancer cells by new chromene-based chalcones

“…The increased fluorescence of compound 14 at 465 nm, upon binding to tubulin, was used to determine the ligand affinity with tubulin (Rai et al, 2008;Gupta et al, 2006). Tubulin (1 µM) was incubated with varying concentrations of ligand (1-50 µM) in 25 mM PIPES at 25°C for 30 min.…”