Cevipabulin-tubulin complex reveals a novel agent binding site on α-tubulin with tubulin degradation effect

• Published in: bioRxiv
• Main Authors: Yang, Jianhong, Yu, Yamei, Li, Yong, Yan, Wei, Ye, Haoyu, Niu, Lu, Tang, Minghai, Wang, Zhoufeng, Zhuang, Yang, Heying Pei, Haoche Wei, Zhao, Min, Wen, Jiaolin, Yang, Linyu, Ouyang, Liang, Wei, Yuquan, Chen, Qiang, Li, Weimin, Chen, Lijuan
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 17.01.2021
• Subjects: Binding sites; Crystallography; Degradation; Drug delivery; Drug development; Guanosine triphosphate; Tubulin; Vinblastine; X-ray crystallography
• DOI: 10.1101/2020.09.11.293563

Abstract Microtubule, composed of αβ-tubulin heterodimers, remains as one of the most popular anticancer targets for decades. To date, anti-microtubule drugs are mainly functionally divided into microtubule-destabilizing and microtubule-stabilizing agents while microtubule- or tubulin-degradation agents are rarely reported. Six known binding sites on tubulin dimer are identified with five sites on β-tubulin and only one site on α-tubulin (pironetin site), hinting compounds binding to α-tubulin are less well characterized. Cevipabulin, a microtubule-active antitumor clinical candidate, is widely accepted as a microtubule-stabilizing agent by binding to the vinblastine site. Our X-ray crystallography study reveals that, in addition binding to the vinblastine site, cevipabulin also binds to a novel site on α-tubulin (named the seventh site) which located near the nonexchangeable GTP. Interestingly, we find the binding of cevipabulin to the seventh site induces tubulin degradation. As the non-exchangeable GTP has structural role and is important for the stability of tubulin dimers, we propose and confirm the tubulin degradation mechanism as: Cevipabulin at the seventh site puts the αT5 loop outward to make the non-exchangeable GTP exchangeable, which reduces the stability of tubulin and results in its destabilization and degradation. Our results confirm a novel agent binding site on α-tubulin and shed light on the development of tubulin degraders as a new generation of anti-microtubule drugs targeting this novel site. Competing Interest Statement The authors have declared no competing interest.