Key Points ST-4 induces CD8 T cell activation and increases TCRVβ 8.2 and 8.3 subgroup expression. ST-4 promotes CD8 fatty acid metabolic program via mTOR/PPARγ/SREBP signal pathway. ST-4 promotes CD8 mitochondrial energy metabolic program via p38 signal pathway. Visual Abstract CD8+ T cells can switch between fatty acid catabolism and mitochondrial energy metabolism to sustain expansion and their cytotoxic functions. ST-4 is a TCR-enhanced mutant derived from superantigen staphylococcal enterotoxin C2 (SEC2), which can hyperactivate CD4+ T cells without MHC class II molecules. However, whether ST-4/SEC2 can enhance metabolic reprogramming in CD8+ T cells remains poorly understood. In this study, we found that ST-4, but not SEC2, could induce proliferation of purified CD8+ T cell from BALB/c mice in Vβ8.2- and -8.3–specific manners. Results of gas chromatography–mass spectroscopy analysis showed that fatty acid contents in CD8+ T cells were increased after ST-4 stimulation. Flow cytometry and Seahorse analyses showed that ST-4 significantly promoted mitochondrial energy metabolism in CD8+ T cells. We also observed significantly upregulated levels of gene transcripts for fatty acid uptake and synthesis, and significantly increased protein expression levels of fatty acid and mitochondrial metabolic markers of mTOR/PPARγ/SREBP1 and p38-MAPK signaling pathways in ST-4–activated CD8+ T cells. However, blocking mTOR, PPARγ, SREBP1, or p38-MAPK signals with specific inhibitors could significantly relieve the enhanced fatty acid catabolism and mitochondrial capacity induced by ST-4. In addition, blocking these signals inhibited ST-4–stimulated CD8+ T cell proliferation and effector functions. Taken together, our findings demonstrate that ST-4 enhanced fatty acid and mitochondria metabolic reprogramming through mTOR/PPARγ/SREBP and p38-MAPK signaling pathways, which may be important regulatory mechanisms of CD8+ T cell activation. Understanding the effects of ST-4–induced regulatory metabolic networks on CD8+ T cells provide important mechanistic insights to superantigen-based tumor therapy.

中文翻译：

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葡萄球菌肠毒素 C2 突变体导向的脂肪酸和线粒体能量代谢程序调节 CD8+ T 细胞活化

要点 ST-4 诱导 CD8 T 细胞活化并增加 TCRVβ 8.2 和 8.3 亚群表达。ST-4 通过 mTOR/PPARγ/SREBP 信号通路促进 CD8 脂肪酸代谢程序。ST-4 通过 p38 信号通路促进 CD8 线粒体能量代谢程序。Visual Abstract CD8+ T 细胞可以在脂肪酸分解代谢和线粒体能量代谢之间切换，以维持扩增及其细胞毒功能。ST-4 是源自超级抗原葡萄球菌肠毒素 C2 (SEC2) 的 TCR 增强突变体，它可以在没有 MHC II 类分子的情况下过度激活 CD4+ T 细胞。然而，ST-4/SEC2 是否可以增强 CD8+T 细胞中的代谢重编程仍然知之甚少。在这项研究中，我们发现 ST-4 而不是 SEC2，可以以 Vβ8.2 和 -8.3 特异性方式诱导来自 BALB/c 小鼠的纯化 CD8+ T 细胞的增殖。气相色谱-质谱分析结果表明，CD8+T 细胞中的脂肪酸含量在 ST-4 刺激后增加。流式细胞术和海马分析表明，ST-4 显着促进 CD8+ T 细胞中的线粒体能量代谢。我们还观察到脂肪酸摄取和合成的基因转录水平显着上调，并显着增加了 ST-4 激活的 CD8+ T 细胞中脂肪酸和 mTOR/PPARγ/SREBP1 和 p38-MAPK 信号通路的线粒体代谢标志物的蛋白质表达水平. 然而，用特异性抑制剂阻断 mTOR、PPARγ、SREBP1 或 p38-MAPK 信号可以显着减轻 ST-4 诱导的增强的脂肪酸分解代谢和线粒体能力。此外，阻断这些信号会抑制 ST-4 刺激的 CD8+ T 细胞增殖和效应子功能。总之，我们的研究结果表明，ST-4 通过 mTOR/PPARγ/SREBP 和 p38-MAPK 信号通路增强了脂肪酸和线粒体代谢重编程，这可能是 CD8+ T 细胞活化的重要调节机制。了解 ST-4 诱导的调节代谢网络对 CD8+ T 细胞的影响为基于超抗原的肿瘤治疗提供了重要的机制见解。