Department of Surgery, Starzl Transplantation Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States.
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States.
Front Immunol. 2019 Jul 2;10:1451. doi: 10.3389/fimmu.2019.01451. eCollection 2019.
In myeloid dendritic cells (DC), deletion of the mechanistic target of rapamycin complex 2 (TORC2) results in an augmented pro-inflammatory phenotype and T cell stimulatory activity; however, the underlying mechanism has not been resolved. Here, we demonstrate that mouse bone marrow-derived TORC2-deficient myeloid DC (TORC2 DC) utilize an altered metabolic program, characterized by enhanced baseline glycolytic function compared to wild-type WT control (Ctrl) DC, increased dependence on glycolytic ATP production, elevated lipid content and higher viability following stimulation with LPS. In addition, TORC2 DC display an increased spare respiratory capacity (SRC) compared to WT Ctrl DC; this metabolic phenotype corresponds with increased mitochondrial mass and mean mitochondrial DNA copy number, and failure of TORC2 DC mitochondria to depolarize following LPS stimulation. Our data suggest that the enhanced metabolic activity of TORC2 DC may be due to compensatory TORC1 pathway activity, namely increased expression of multiple genes upstream of Akt/TORC1 activity, including the integrin alpha IIb, protein tyrosine kinase 2/focal adhesion kinase, IL-7R and Janus kinase 1(JAK1), and the activation of downstream targets of TORC1, including p70S6K, eukaryotic translation initiation factor 4E binding protein 1 (4EBP1) and CD36 (fatty acid translocase). These enhanced TORC1 pathway activities may culminate in increased expression of the nuclear receptor peroxisome proliferator-activated receptor γ (Pparγ) that regulates fatty acid storage, and the transcription factor sterol regulatory element-binding transcription factor 1 (Srebf1). Taken together, our data suggest that TORC2 may function to restrain TORC1-driven metabolic activity and mitochondrial regulation in myeloid DC.
在髓系树突状细胞 (DC) 中，雷帕霉素靶蛋白复合物 2 (TORC2) 的缺失导致促炎表型和 T 细胞刺激活性增强；然而，其潜在机制尚未解决。在这里，我们证明了小鼠骨髓来源的 TORC2 缺陷型髓系 DC（TORC2 DC）利用了改变的代谢程序，其特征是与野生型 WT 对照 (Ctrl) DC 相比，基础糖酵解功能增强，对糖酵解 ATP 产生的依赖性增加，刺激后脂质含量升高，活力增加 LPS。此外，与 WT Ctrl DC 相比，TORC2 DC 显示出增加的备用呼吸能力 (SRC)；这种代谢表型与增加的线粒体质量和平均线粒体 DNA 拷贝数相对应，并且 TORC2 DC 线粒体在 LPS 刺激后不能去极化。我们的数据表明，TORC2 DC 增强的代谢活性可能是由于 TORC1 途径活性的代偿性增加，即 Akt/TORC1 活性上游的多个基因表达增加，包括整合素 alpha IIb、蛋白酪氨酸激酶 2/粘着斑激酶、IL-7R 和 Janus 激酶 1 (JAK1)，以及 TORC1 的下游靶标，包括 p70S6K、真核翻译起始因子 4E 结合蛋白 1 (4EBP1) 和 CD36（脂肪酸转运蛋白）的激活。这些增强的 TORC1 途径活性可能导致核受体过氧化物酶体增殖物激活受体 γ (Pparγ) 的表达增加，该受体调节脂肪酸储存，以及转录因子固醇调节元件结合转录因子 1 (Srebf1)。综上所述，我们的数据表明，TORC2 可能在髓系 DC 中发挥作用，以抑制 TORC1 驱动的代谢活性和线粒体调节。
