Protein O-GlcNAcylation in Regulatory T Cell Function

项目摘要 调节性T（Treg）细胞以表达FOXP 3为特征，是T淋巴细胞的独特谱系 控制自身免疫耐受和组织内环境稳定。这些细胞与多种 人类疾病，如自身免疫性疾病、炎症、器官移植排斥和一些感染 和癌症。生物医学界已经对靶向Treg细胞产生了强烈的兴趣， 免疫治疗;然而，显著的障碍，例如Treg细胞功能异质性和不稳定性， 需要克服，以实现临床可行性。这项研究旨在理解一部小说 调节性T细胞的稳定性和功能的分子机制。我们的初步数据显示， 新的O-连接的N-乙酰葡糖胺（O-GlcNAc）蛋白修饰，由T细胞受体（TCR）激活 信号传导对于Treg细胞的抑制功能是必不可少的。Treg细胞特异性敲除O-GlcNAc 催化O-GlcNAc酰化的酶--葡萄糖基转移酶（OGT）不影响Treg细胞谱系特化， 导致小鼠发生侵袭性自身免疫综合征。O-GlcNAc酰化修饰和 稳定FOXP 3蛋白，转录组学分析显示，IL-2/STAT 5信号转导被抑制， OGT缺陷型Treg细胞。因此，我们假设TCR启动的蛋白质O-GlcNAc化调节 F0 XP 3和STAT 5，从而连接TCR和IL-2信号传导途径，以调节Treg细胞稳态， 效应子功能在目的1中，我们假设O-GlcNAc化的丧失使FOXP 3蛋白不稳定，消除了FOXP 3蛋白的活性。 Treg细胞的抑制功能和将Treg细胞转化为效应T细胞。我们将决定 O-GlcNAc化抵消泛素化以稳定FOXP 3蛋白，从而维持Treg身份。通过 产生FOXP 3突变小鼠，其中O-GlcNAc化被特异性消除，我们将测试FOXP 3是否 O-GlcNAc化是Treg细胞的抑制活性所必需的。在目标2中，我们建议检查 STAT 5 O-GlcNAc化对Treg细胞抑制功能的影响。我们将检验O-GlcNAcylation的假设 控制Treg细胞中IL-2刺激的STAT 5活化，FOXP 3和STAT 5协同作用介导IL-2刺激的STAT 5活化。 蛋白质O-GlcNAc化在Treg细胞功能中作用。在目标3中，我们将确定TCR与 和Treg细胞中的O-GlcNAc化。我们将检验TCR信号促进蛋白O- GlcNAc化和Treg细胞抑制活性以Ca 2 +/CaMK II依赖性方式。最后，通过无偏 O-GlcNAc蛋白质组学，我们将表征TCR调节的蛋白质O-GlcNAc化谱并识别潜在的 O-GlcNAc介导的Treg细胞功能的互补机制。拟议的研究将促进 开辟了一条新的治疗途径，旨在激活和维持Treg细胞用于免疫治疗。

PROJECT SUMMARY Regulatory T (Treg) cells, characterized by the expression of FOXP3, are a distinct lineage of T lymphocytes that control immunological self-tolerance and tissue homeostasis. These cells are associated with a multitude of human diseases, such as autoimmune disease, inflammation, organ transplant rejection, and some infections and cancers. The biomedical community has developed an intense interest in targeting Treg cells for immunotherapy; however, significant barriers, for example Treg-cell functional heterogeneity and instability, need to be surmounted in order to achieve clinical feasibility. The proposed study aims to understand a novel molecular mechanism that control the stability and function of Treg cells. Our preliminary data have found that a novel O-linked N-Acetylglucosamine (O-GlcNAc) protein modification, activated by T-cell receptor (TCR) signaling, is indispensable for the suppressive function of Treg cells. Treg cell-specific knockout of O-GlcNAc transferase (OGT), the enzyme catalyzing O-GlcNAcylation, does not affect Treg cell lineage specification but results in the development of an aggressive autoimmune syndrome in mice. O-GlcNAcylation modifies and stabilizes FOXP3 protein and transcriptomic analyses have revealed that IL-2/STAT5 signaling is suppressed in OGT-deficient Treg cells. Therefore, we hypothesize that TCR-initiated protein O-GlcNAcylation modulates FOXP3 and STAT5, thereby linking TCR and IL-2 signaling pathways, to regulate Treg cell homeostasis and effector function. In Aim 1, we hypothesize that loss of O-GlcNAcylation destabilizes FOXP3 protein, eliminating the suppressive function of Treg cells and converting Treg cells into effector T cells. We will determine whether O-GlcNAcylation counteracts ubiquitination to stabilize FOXP3 protein, thus maintaining the Treg identity. By generating FOXP3 mutant mice, in which O-GlcNAcylation is specifically abolished, we will test whether FOXP3 O-GlcNAcylation is required for the suppressive activity of Treg cells. In Aim 2, we propose to examine the effect of STAT5 O-GlcNAcylation on Treg cell suppressive function. We will test the hypothesis that O-GlcNAcylation controls IL-2-stimulated STAT5 activation in Treg cells and FOXP3 and STAT5 act cooperatively to mediate the effect of protein O-GlcNAcylation in Treg cell function. In Aim 3, we will identify the molecular link between TCR and O-GlcNAcylation in Treg cells. We will test the hypothesis that TCR signaling promotes protein O- GlcNAcylation and Treg cell suppressive activity in a Ca2+/CaMKII-dependent manner. Lastly, through unbiased O-GlcNAc proteomics, we will characterize TCR-regulated protein O-GlcNAcylation profile and identify potential complementary mechanisms for O-GlcNAc-mediated Treg cell function. The proposed study will stimulate the opening of a new avenue in therapeutics directed to activate and maintain Treg cells for immunotherapy.