Transcriptional regulation of inflammatory helper T Cell differentiation

描述(由申请人提供)：CD4+辅助T(TH)淋巴细胞是适应性免疫反应的基本组织者，也是免疫介导性炎症性和过敏性疾病的关键介质。在抗原提呈细胞(APC)的激活下，幼稚TH细胞经过克隆扩增和功能分化为分泌细胞因子的效应细胞。效应器TH细胞历来被分为TH1和TH2亚群。最近，我们和其他研究小组发现了一个新的TH亚群，命名为TH17，它可以产生IL-17。在上一个资助周期中，我们研究了控制TH17分化的分子程序。我们已经确定了STAT3在细胞因子调节的TH17分化中的关键作用。我们进一步表明，STAT3是上调两个TH17特异性孤儿核受体RORA和RORg所必需的，这两个因素在TH17分化中起着协同和一定程度上的冗余作用。我们还报道了RORA和RORg在激活IL-17和IL-17F基因转录方面的作用，IL-17-IL-17F基因是两个相关的细胞因子基因，但在体内功能不同，在报告实验中，IL-17-IL-17F基因座位上的CNS2元件促进了IL-17基因启动子依赖于ROR的转录。此外，我们还发现Foxp3+Treg和TH17细胞在体外和体内都表现出拮抗调节，并具有功能可塑性。Smad2和Smad3分子都被TGFb信号激活，对Treg和TH17细胞的分化有不同的调节作用。尽管取得了这些成就，但关于TH17细胞的转录调控仍然存在疑问。首先，在成熟的TH17细胞中，RORs对于维持细胞因子转录是否重要？第二，Rors如何调控IL-17和IL-17F基因的转录？第三，考虑到Rors与各种辅助激活剂的功能相关，TH17细胞分化需要哪些辅助激活剂？我们将在拟议拨款中继续探讨这些问题。首先，我们将确定RORg和RORA在成熟的TH17细胞和Treg细胞中的功能。其次，我们将研究Rors如何调控TH17细胞因子转录。我们将确定IL-17F转录可能也需要的其他元件。最后，我们将从遗传学角度分析SRC分子在TH17分化中的作用。我们将在体外和体内研究它们在TH17细胞分化过程中的功能和调控。总体而言，拟议的项目将以前一个周期中显示的对TH17分化至关重要的转录因子为中心。我们将分析这些因子的生物学功能以及它们潜在的作用机制。这些研究将进一步证实我们对这些重要调控因子的理解，并促进在人类疾病治疗中针对这些途径的持续努力。

DESCRIPTION (provided by applicant): CD4+ helper T (TH) lymphocytes are essential organizers of adaptive immune responses and key mediators in immune-mediated inflammatory and allergic diseases. Upon activation by antigen-presenting cells (APC), naive TH cells undergo clonal expansion and functional differentiation into cytokine-secreting effector cells. Effector TH cells have been historically classified into TH1 and TH2 subsets. Recently, a novel TH subset, named TH17, that makes IL-17 has been identified by our and other groups. In the last funding cycle, we have investigated the molecular programs governing TH17 differentiation. We have identified key function of STAT3 in mediating cytokine-regulated TH17 differentiation. We further showed that STAT3 is required for upregulation of two TH17-specific orphan nuclear receptors RORa and RORg and that these two factors play synergistic and somewhat redundant function in TH17 differentiation. We also reported that RORa and RORg function in activating the transcription of IL-17 and IL-17F genes, two related cytokine genes but with differential in vivo function, and that the CNS2 element in IL-17-IL-17F gene locus enhances ROR-dependent transcription of IL-17 gene promoter in a reporter assay. Furthermore, we show that Foxp3+ Treg and TH17 cells exhibit antagonistic regulation yet with functional plasticity in vitro and in vivo. Smad2 and Smad3 molecules, both of which are activated by TGFb signaling, differentially regulate Treg and TH17 cell differentiation. Despite these achievements, there are still remaining questions about the transcriptional regulation in TH17 cells. First, are RORs important for maintaining cytokine transcription in mature TH17 cells? Second, how do RORs regulate the transcription of the IL-17 and IL-17F genes? Thirdly, considering RORs associate with various co-activators for their function, what co-activators are required for TH17 cell differentiation? We will pursue these questions in the proposed grant. First, we will determine the function of RORg and RORa in mature TH17 cells and in Treg cells. Secondly, we will examine how RORs regulate TH17 cytokine transcription. We will identify additional elements that may be also required for IL-17F transcription. Lastly, we will genetically analyze the functio of SRC molecules in TH17 differentiation. We will investigate their function and regulation during TH17 cell differentiation in vitro and in vivo. Overall, the proposed project will center on the transcription factors that were shown in the previous cycle to be crucial in TH17 differentiation. We will analyze the biological function of these factors as well as the mechanisms underlying their function. These studies will further substantiate our understanding on these important regulators and facilitate ongoing efforts in targeting these pathways in treatment of human diseases.