Sirtuin inhibition by plumbagin connects protein acetylation to cell division

Naphthoquinones interfere with biological systems and exhibit pharmaceutical properties. As an electrophile, the naphthoquinone plumbagin may react with nucleophiles, mainly thiols, and form covalent adducts. Here, we have further characterized the effects of plumbagin in HeLa cells. First, we demonstrate that plumbagin interferes with mitosis by affecting the mitotic spindle formation without preventing exit from mitosis. This plumbagin-induced delay in cell division was reproduced by class III histone deacetylase (HDAC) inhibitors but not by the class I, II and IV pan-HDAC inhibitor trichostatin A; therefore, it most likely involves sirtuins. Second, we establish that, in addition to blocking cell division, plumbagin induces protein hyperacetylation in a sulfhydryl arylation-dependent manner. Finally, in a manner consistent with the plumbagin-dependent inhibition of sirtuin 2 (SIRT2), we show that plumbagin interferes with the centrosomal localization of SIRT2 and induces increased acetylation of α-tubulin, a SIRT2 target. Inhibition of sirtuin activity induces hyperacetylation of proteins such as TPX2 and its delocalization, and consequently interferes with mitotic spindle formation and cell division. Since plumbagin most likely inhibits SIRT2, which is known to modulate several proteins involved in different pathological processes, we propose that it could be a promising therapeutic agent.