Photo-Reversible Inhibition of Mitotic Kinesin Eg5 by Photochromic STLC Analogues Composed of Azobenzene

Abstract

The kinesin Eg5, is a microtubule plus-end directed homotetrameric molecular motor that is essential for the formation of a bipolar spindle during eukaryotic cell division. Eg5 exists only in proliferating cells, and is required for mitosis. Therefore, Eg5 is new target of cancer therapy. It is known that some small molecules specifically inhibit Eg5 activity. S-trityl-L-cysteine (STLC) is one of the potent Eg5 specific inhibitors. In this study, we tried to develop photochromic Eg5 inhibitors that control inhibitory activity of Eg5 by ultraviolet (UV) and visible (VIS) light irradiations reversibly. Azobenzene is one of the typical photochromic molecules, which shows cis, and trans isomerization by UV and VIS light irradiations respectively. In this study, we designed and synthesized photochromic inhibitors utilizing azobenzene. As the trityl group of STLC is a key moiety to exhibit inhibitory activity, we linked the trityl group to N-acetyl cysteine or maleic acid via azobenzene. The synthesized two photochromic inhibitors, TAB-MA and TAB-Ac-Cys inhibited the ATPase activity of Eg5 at the different inhibition constants between cis and trans isomers. Trans-isomers of the inhibitors showed more significant inhibition of ATPase activity than cis-isomers. Moreover, Eg5 driven microtubule gliding was photo controlled by TAB-Ac-Cys. Trans-TAB-Ac-Cys decreased the velocity of microtubule gliding more significantly than cis-TAB-Ac-Cys.