Fu Xuanhe, Xu Mingkai, Yao Songyuan, Zhang Huiwen, Zhang Chenggang, Zhang Jinghai
School of Life Science and Biopharmaceutics, Shenyang Pharmaceutical University, 103 WenHua Road, Shenyang 110016, PR China.
Institute of Applied Ecology, Chinese Academy of Sciences, 72 WenHua Road, Shenyang 110016, PR China.
Toxicol Appl Pharmacol. 2017 Oct 15;333:51-59. doi: 10.1016/j.taap.2017.08.006. Epub 2017 Aug 12.
Staphylococcal enterotoxin C2 (SEC2), a superantigen, causes rapid clonal expansion of lymphocytes and secretion of T cell growth factors, leading to a severe inflammatory response within tissues. Although previous studies have shown that ST-4, a SEC2 mutant with enhanced recognition of Vβ regions of T-cell receptors (TCRVβ), can activate an increased number of T cells and produce more cytokines than SEC2. However, the signaling mechanisms of SEC2/ST-4-mediated immune activation have not been addressed. In this study, we showed that the phosphatidylinositide-3-kinase (PI-3K) inhibitor LY294002, mammalian target of rapamycin (mTOR) inhibitor rapamycin, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inhibitor Bay11-7085 could suppress SEC2/ST-4-induced proliferation, CD69/CD25 expression, cell-cycle progression, and IL-2 production in BALB/c mouse splenocytes. In addition, we observed significantly upregulated expression of p70S6K, cyclin E, cyclin D3, and NF-ĸB/p65, but downregulated expression of p27kip during SEC2/ST-4-driven T cells activation. However, SEC2/ST-4-induced changes in cell cycle and PI3K/mTOR signaling were significantly relieved by either LY294002 or rapamycin, and the induction of NF-ĸB/p65 induced was significantly downregulated by Bay11-7085. Moreover, we found that IL-2 secretion was positively associated with p65 expression in a time- and dose-dependent manner. Taken together, our findings demonstrate the involvement of PI3K/mTOR and NF-κB signaling pathways in SEC2/ST-4-induced T cell activation. ST-4 intensifies PI3K/mTOR and NF-ĸB signaling transduction, ultimately leading to enhance T cell activation. These results provide a theoretical mechanism for future immunotherapy using ST-4.
葡萄球菌肠毒素C2（SEC2）是一种超抗原，可导致淋巴细胞快速克隆扩增并分泌T细胞生长因子，从而在组织内引发严重的炎症反应。尽管先前的研究表明，ST-4作为一种对T细胞受体Vβ区域（TCRVβ）具有更强识别能力的SEC2突变体，比SEC2能激活更多数量的T细胞并产生更多细胞因子。然而，SEC2/ST-4介导的免疫激活的信号传导机制尚未得到阐明。在本研究中，我们发现磷脂酰肌醇-3-激酶（PI-3K）抑制剂LY294002、雷帕霉素的哺乳动物靶点（mTOR）抑制剂雷帕霉素以及活化B细胞核因子κB轻链增强子（NF-κB）抑制剂Bay11-7085能够抑制SEC2/ST-4诱导的BALB/c小鼠脾细胞增殖、CD69/CD25表达、细胞周期进程以及IL-2产生。此外，我们观察到在SEC2/ST-4驱动的T细胞激活过程中，p70S6K、细胞周期蛋白E、细胞周期蛋白D3和NF-κB/p65的表达显著上调，但p27kip的表达下调。然而，LY294002或雷帕霉素可显著缓解SEC2/ST-4诱导的细胞周期和PI3K/mTOR信号变化，而Bay11-7085可显著下调NF-κB/p65的诱导表达。此外，我们发现IL-2分泌与p65表达呈时间和剂量依赖性正相关。综上所述，我们的研究结果表明PI3K/mTOR和NF-κB信号通路参与了SEC2/ST-4诱导的T细胞激活。ST-4增强了PI3K/mTOR和NF-κB信号转导，最终导致T细胞激活增强。这些结果为未来使用ST-4进行免疫治疗提供了理论机制。
