Han Li, Xu Danqing, Xi Zhichao, Wu Man, Nik Nabil Wan Najbah, Zhang Juan, Sui Hua, Fu Wenwei, Zhou Hua, Lao Yuanzhi, Xu Gang, Guo Cheng, Xu Hongxi
School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
Department of Pharmacy, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
Front Pharmacol. 2020 Dec 17;11:564833. doi: 10.3389/fphar.2020.564833. eCollection 2020.
PPAPs (Polycyclic polyprenylated acylphloroglucinols) are a class of compounds with diverse bioactivities, including anticancer effects. Oblongifolin C (OC) is a PPAP isolated from the plant of Hu. We previously discovered that OC induces apoptosis, inhibits autophagic flux, and attenuates metastasis in cancer cells. However, the protein targets and the detailed mechanism of action of OC remain unclear. To identify protein targets of OC, a non-labeled protein fishing assay was performed, and it was found that OC may interact with several proteins, including the heat shock 70 kDa protein 8 (HSPA8). Expanding on our previous studies on protein cathepsin B, this current study applied Surface Plasmon Resonance (SPR) and Isothermal Titration Calorimetry (ITC) to confirm the potential binding affinity between OC and two protein targets. This study highlights the inhibitory effect of OC on HSPA8 in cancer cells under heat shock stress, by specifically inhibiting the translocation of HSPA8. OC also enhanced the interaction between HSPA8, HSP90, and p53, upregulated the expression of p53 and significantly promoted apoptosis in cisplatin-treated cells. Additionally, a flow cytometry assay detected that OC sped up the apoptosis rate in HSPA8 knockdown A549 cells, while overexpression of HSPA8 delayed the OC-induced apoptosis rate. In summary, our results reveal that OC potentially interacts with HSPA8 and cathepsin B and inhibits HSPA8 nuclear translocation and cathepsin B activities, altogether suggesting the potential of OC to be developed as an anticancer drug.
多环多异戊二烯基酰基间苯三酚（PPAPs）是一类具有多种生物活性的化合物，包括抗癌作用。长叶九里香素C（OC）是从虎杖属植物中分离出的一种PPAP。我们之前发现OC可诱导癌细胞凋亡、抑制自噬流并减弱癌细胞转移。然而，OC的蛋白质靶点和详细作用机制仍不清楚。为了确定OC的蛋白质靶点，我们进行了非标记蛋白质筛选试验，发现OC可能与几种蛋白质相互作用，包括热休克70 kDa蛋白8（HSPA8）。在我们之前对组织蛋白酶B的研究基础上，本研究应用表面等离子体共振（SPR）和等温滴定量热法（ITC）来确认OC与两个蛋白质靶点之间的潜在结合亲和力。本研究强调了在热休克应激下OC对癌细胞中HSPA8的抑制作用，通过特异性抑制HSPA8的易位来实现。OC还增强了HSPA8、HSP90和p53之间的相互作用，上调了p53的表达，并显著促进顺铂处理细胞的凋亡。此外，流式细胞术检测发现OC加快了HSPA8敲低的A549细胞的凋亡率，而HSPA8的过表达则延迟了OC诱导的凋亡率。总之，我们的结果表明OC可能与HSPA8和组织蛋白酶B相互作用，抑制HSPA8的核易位和组织蛋白酶B的活性，这表明OC具有开发成为抗癌药物的潜力。
