Dias, D. A.; Kulasegaram, V.; Okorokova-Facanha, A.; Chen, Q.

Curcumin is the active ingredient of one of the most widely used spices in the world for millennia. It is also highly valued as a traditional health supplement in many South Asian countries. It is not surprising that this yellow turmeric has attracted strong attention for its therapeutic potential in recent years. Nevertheless, the molecular and cellular targets of curcumin remain unknown. Here, we took a novel imaging-based approach to determine the intracellular localization of curcumin using the model organism fission yeast Schizosacchromyces pombe. We took advantage of the intrinsic fluorescence of curcumin to track its whereabout in yeast cells. Live fluorescence microscopy revealed for the first time that curcumin, at a concentration as low as one micromolar, formed a narrow circumferential band around the equatorial plane of dividing cells within 10 minutes of addition. The intensity of this band increased proportionally to the concentration of curcumin and gradually over time. Inhibition of cell division by the cdc25 temperature-sensitive mutation inhibited the curcumin band. During cytokinesis, curcumin co-localized with the integrated plasma membrane protein Bgs1 at the cleavage furrow, not with either the contractile ring or the septum markers. Besides fission yeast, such equatorial curcumin band was found in the dividing cells of two other yeasts, Saccharomyces cerevisiae and Candida albicans. Our study thus discovered that this widely used yellow turmeric targets the cleavage furrow of dividing yeast cells, suggesting that curcumin may have anti-fungal therapeutic potential (223 words).