Shin Sol-Bi, Woo Sang-Uk, Yim Hyungshin
Department of Pharmacy, College of Pharmacy, Institute of Pharmaceutical Science and Technology, Hanyang University, Ansan, Gyeonggi-do, Korea.
J Cell Physiol. 2015 Dec;230(12):3057-67. doi: 10.1002/jcp.25042.
The expression of polo-like kinase 1 (Plk1) correlates with malignancy and is thus recognized as a target for cancer therapy. In addition to the development of ATP-competitive Plk1 inhibitors, the polo-box domain (PBD), a unique functional domain of PLKs, is being targeted to develop Plk1-specific inhibitors. However, the action mechanisms of these two classes of Plk1 inhibitors have not been thoroughly evaluated. Here, we evaluate the differences in cellular effects of ATP-binding domain inhibitors (BI 2536, GSK 461364) and PBD inhibitors (poloxin, thymoquinone) to determine their mechanisms of Plk1 inhibition. Our data show that BI 2536 and GSK461364 increased the population of cells in the G2/M phase compared with controls, while treatment with poloxin and thymoquinone increased cell population in the S phase as well as in G2/M, in a p53-independent manner. The population of cells staining positively for p-Histone H3 and MPM2, mitotic index, was increased by treatment with BI 2536 or GSK461364, but not by treatment with poloxin or thymoquinone. Furthermore, treatment with BI 2536 or GSK461364 resulted in activation of the BubR1 spindle checkpoint kinase, suggesting that treatment with ATP-binding domain inhibitors induces metaphase arrest. However, the administration of poloxin and thymoquinone resulted in an increase in p21(WAF1) and S arrest, indicating that PBD inhibitors also affected interphase before mitotic entry. Taken together, these data suggest that the PDB of Plk1 plays a role in S phase progression through interaction with other proteins, while its ATP-binding domain is important for regulating mitotic progression mediated by its catalytic activity involving consumption of ATP.
polo样激酶1（Plk1）的表达与恶性肿瘤相关，因此被视为癌症治疗的靶点。除了开发ATP竞争性Plk1抑制剂外，polo框结构域（PBD）作为PLKs的一个独特功能结构域，也正被作为开发Plk1特异性抑制剂的靶点。然而，这两类Plk1抑制剂的作用机制尚未得到充分评估。在此，我们评估了ATP结合结构域抑制剂（BI 2536、GSK 461364）和PBD抑制剂（poloxin、百里醌）对细胞作用的差异，以确定它们抑制Plk1的机制。我们的数据表明，与对照组相比，BI 2536和GSK461364增加了G2/M期细胞的比例，而poloxin和百里醌处理则以不依赖p53的方式增加了S期以及G2/M期的细胞比例。用BI 2536或GSK461364处理可增加p-组蛋白H3和MPM2染色阳性的细胞群体，即有丝分裂指数，但用poloxin或百里醌处理则没有。此外，用BI 2536或GSK461364处理导致BubR1纺锤体检查点激酶激活，表明用ATP结合结构域抑制剂处理可诱导中期阻滞。然而，poloxin和百里醌的给药导致p21（WAF1）增加和S期阻滞，表明PBD抑制剂在有丝分裂进入之前也影响间期。综上所述，这些数据表明Plk1的PDB通过与其他蛋白质相互作用在S期进程中发挥作用，而其ATP结合结构域对于调节由其涉及ATP消耗的催化活性介导的有丝分裂进程很重要。
