Department of Immunology and Oncology, Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Mol Cell Biol. 2012 Oct;32(20):4168-80. doi: 10.1128/MCB.00654-12. Epub 2012 Aug 13.
Diacylglycerol kinase α (DGKα) regulates diacylglycerol levels, catalyzing its conversion into phosphatidic acid. The α isoform is central to immune response regulation; it downmodulates Ras-dependent pathways and is necessary for establishment of the unresponsive state termed anergy. DGKα functions are regulated in part at the transcriptional level although the mechanisms involved remain poorly understood. Here, we analyzed the 5' end structure of the mouse DGKα gene and detected three binding sites for forkhead box O (FoxO) transcription factors, whose function was confirmed using luciferase reporter constructs. FoxO1 and FoxO3 bound to the 5' regulatory region of DGKα in quiescent T cells, as well as after interleukin-2 (IL-2) withdrawal in activated T cells. FoxO binding to this region was lost after complete T cell activation or IL-2 addition, events that correlated with FoxO phosphorylation and a sustained decrease in DGKα gene expression. These data strongly support a role for FoxO proteins in promoting high DGKα levels and indicate a mechanism by which DGKα function is downregulated during productive T cell responses. Our study establishes a basis for a causal relationship between DGKα downregulation, IL-2, and anergy avoidance.
二酰基甘油激酶 α（DGKα）调节二酰基甘油水平，催化其转化为磷脂酸。α 同工型是免疫反应调节的核心；它下调 Ras 依赖性途径，是建立称为无能的无反应状态所必需的。DGKα 的功能部分受转录水平的调节，尽管涉及的机制仍知之甚少。在这里，我们分析了小鼠 DGKα 基因的 5'端结构，并检测到三个叉头框 O（FoxO）转录因子的结合位点，其功能通过荧光素酶报告基因构建得到证实。FoxO1 和 FoxO3 在静止 T 细胞中以及在激活的 T 细胞中白细胞介素 2（IL-2）撤出后与 DGKα 的 5'调控区结合。FoxO 与该区域的结合在完全 T 细胞激活或 IL-2 加入后丢失，这与 FoxO 磷酸化和 DGKα 基因表达的持续下降相关。这些数据强烈支持 FoxO 蛋白在促进高 DGKα 水平中的作用，并表明 DGKα 功能在有活力的 T 细胞反应中下调的一种机制。我们的研究为 DGKα 下调、IL-2 和避免无能之间的因果关系奠定了基础。
