Foxo1-dependent Programme in the Control of Regulatory T Cell Function

描述(申请人提供)：CD4+Foxp3+调节性T细胞(Tregs)在控制对自身抗原、过敏原和共生体的免疫耐受以及对病原体和肿瘤的免疫反应中发挥关键作用。我们最近的研究表明，Treg的功能依赖于转录因子叉头盒O1(Foxo1)，部分是通过Foxo1抑制促炎细胞因子干扰素-γ的表达而实现的。在本项目的第一部分，我们将探索Foxo1诱导树突状细胞干扰素-γ抑制的机制。对Foxo1结合位点的全基因组分析表明，Foxo1被招募到IFNG和IRF1的调控元件中，这两个元件编码一种转录因子，促进T细胞产生干扰素-γ。将进行Foxo1 DNA结合和报告基因分析，以确定Foxo1是否抑制IFNG和IRF1的增强子和启动子活性。对Foxo1相关蛋白的蛋白质组学研究证实了Foxo1与转录因子Runx3之间的物理相互作用。将绘制介导Foxo1与Runx3相互作用的精确蛋白质结构域，并研究它们在调节Runx3诱导的干扰素-γ表达中的作用。此外，还将确定IRF1、IRF1诱导的IL-12Rβ1和Runx3在体内控制干扰素-γ表达的功能以及Foxo1缺陷Tregs的抑制活性。在项目的第二部分，我们将使用弓形虫感染模型来研究干扰素-γ表达的Treg获得和相关的Treg功能缺陷是否由Foxo1活性的丧失引起。这些研究的完成将产生对新的Foxo1依赖的遗传程序的机械性见解，该程序控制Treg在免疫稳定状态和感染期间的功能。

DESCRIPTION (provided by applicant): CD4+Foxp3+ regulatory T cells (Tregs) play a pivotal role in the control of immune tolerance to self-antigens, allergens, and commensals as well as immune responses to pathogens and tumors. Our recent studies have revealed that Treg function is dependent on the transcription factor forkhead box O1 (Foxo1) mediated in part by Foxo1 suppression of the proinflammatory cytokine IFN-γ expression. In the first part of the project, we will explore the mechanisms of Foxo1-induced IFN-γ repression in Tregs. Genome-wide analysis of Foxo1 binding sites showed that Foxo1 is recruited to the regulatory elements of Ifng and Irf1, which encodes a transcription factor that promotes IFN-γ production in T cells. Foxo1 DNA binding and reporter gene assays will be performed to determine whether Foxo1 inhibits the enhancer and promoter activities of Ifng and Irf1. Proteomics studies of Foxo1-associated proteins demonstrated physical interactions between Foxo1 and the transcription factor Runx3. The precise protein domains that mediate Foxo1 interaction with Runx3 will be mapped, and their role in regulating Runx3-induced IFN-γ expression will be studied. Furthermore, the in vivo functions of IRF1, IRF1-induced IL-12Rβ1, and Runx3 in the control of IFN-γ expression and the suppressive activities of Foxo1-deficient Tregs will be determined. In the second part of the project, we will use a Toxoplasma gondii infection model to investigate whether Treg acquisition of IFN-γ expression and the associated Treg functional defects are caused by the loss of Foxo1 activities. Completion of these studies will generate mechanistic insights to the novel Foxo1-dependent genetic program that controls Treg function in the immunological steady state and during infection.