Photo-Regulation of Cell Division using Photochromic Inhibitors for Kinesin Eg5

Abstract

Previously it has been demonstrated that some kinesins known as an ATP driven motor protein are directly involved in regulation of the cell division cycle. Eg5 is one of the kinesin and its biochemical properties and structure were well studied. It is suggested that that Eg5 is activated in M phase of cell cycle and performs stabilizing and positioning of spindle. It is also known that Eg5 is overexpressed in tumor cell and induce significant cell division. Monastrol and STLC, which are potent inhibitor specific for kinesin Eg5, shut off mitotic division and result in apotosis. Therefore, these inhibitors are attracting as anti-cancer drug. Azobenzene and spiropyran, a widely studied photochromic compound, can be reversibly isomerized between the cis and trans forms by ultra-violet (UV) and visible (VIS) light irradiation, respectively. We have recently demonstrated the Monastrol and STLC analogues composed of photochromic molecules inhibit ATPase activity of Eg5 reversibly upon UV and VIS light irradiation in vitro. Therefore, it is strongly expected that the photochromic inhibitors are applicable to reversible photo-regulation of cell mitosis. In this study, we have examined the effects of the photochromic inhibitors for mammalian cells. Effects of the photochromic inhibitors were evaluated by survival number of mammalian cells, HeLa cells or A172 cells. Survival numbers of cells were quantitatively analyzed by MTS reagent and cell divisions were observed by phase-contrast microscope. spindle behavior of the cells cultured in the presence of photochromic inhibitors were also examined using immunofluorescent staining. These experimental results suggested that the effects of photochromic inhibitors for the cell division were controlled by UV and VIS light irradiations reversibly.