泛素缀合酶Ubc13在树突状细胞中的免疫调控功能及机制研究

As the bridge linking innate and adaptive immune responses, dendritic cells (DCs) play pivotal roles in initiating robust immunity against pathogens and maintaining immunological tolerance to self antigens. Activation of β-catenin in DCs has been shown to regulate immunity versus tolerance in the intestine. Ubc13, the lysine 63-specific ubiquitin-conjugating E2 enzyme, mediates activation of numerous signaling pathways and therefore regulates immune responses, and many other biological processes as well. We previously identified that Ubc13 controls hematopoiesis through negatively regulating Wnt/β-catenin signaling pathway. Through characterizing recently generated Ubc13 dendritic cell-specific knockout (CD11c-Cre+Ubc13flox/flox, designated as Ubc13ΔDC) mice, we found that Ubc13 functions as a negative regulator of Wnt/β-catenin signaling in dendritic cells, therefore controls immune homeostasis. In this project, we will utilize methodologies at molecular, cellular, and in vivo animal levels to systemically investigate functions and regulatory mechanisms of Ubc13 in dendritic cells. The outcomes of this study will yield important insights into molecular and cellular mechanisms of dendritic cell biology, and shed lights on developing dendritic cell-based vaccines. Given that small inhibitors targeting Ubc13 and its regulated pathways are already available, our study will provide novel knowledge to further clinical applications of those inhibitors in autoimmune, inflammatory diseases and cancer immunotherapies. Following three specific aims will be pursued: .1..Study functions of Ubc13 in dendritic cells, including characterizing Ubc13-deficienct DCs and testing DSS-Colitis, EAE, and tumor implantation models in Ubc13ΔDC mice..2..Investigate molecular and cellular and mechanisms by which Ubc13 regulates dendritic cell maturation and activation. .3..Examine effect of pharmacologically inhibiting Ubc13 on DC functions.

免疫反应和免疫耐受的平衡对于维持人体免疫系统的健康运行至关重要。树突状细胞作为连接先天和适应性免疫反应的桥梁，在维持这种平衡中起着不可或缺的作用。Wnt/β-Catenin信号通路在树突状细胞中的激活控制肠道免疫系统中的免疫耐受。作为专一的特异性地介导第63位赖氨酸链接泛素链的泛素缀合酶，Ubc13调控众多信号传导通路和不同的免疫反应过程。我们前期已发表的工作揭示了在造血过程中，Ubc13负向调节Wnt/β-Catenin信号通路。近期我们又发现Ubc13可能通过调控Wnt/β-Catenin的激活来控制树突状细胞的生物学功能。在本课题研究中，我们将综合使用分子、细胞生物学、生物化学、免疫学及在体小鼠模型手段，系统深入地研究：1）Ubc13对树突状细胞功能的调控；2）Ubc13在树突状细胞中的信号调控机制；3）Ubc13小分子抑制剂在树突状细胞中的应用。

树突状细胞中Wnt/β-catenin信号通路对维持免疫力和免疫耐受的平衡至关重要，但其中的机制仍不清楚。本项目我们发现泛素缀合酶Ubc13通过负向调控β-catenin的蛋白水平控制DC的功能。DC特异性Ubc13敲除小鼠导致DC过度激活，上调共刺激分子如CD40, CD80并分泌更多的炎性细胞因子如IL-12和 IL-23，同时Ubc13敲除的DC具备更强的激活T细胞能力。我们同时获得DC细胞APC（β-catenin负向调控分子）特异性敲除小鼠，其表型和Ubc13 DC条件性敲除小鼠非常类似。我们更进一步获得DC细胞特异性Ubc13和β-catenin双基因敲除（DKO）小鼠。非常重要的是，β-catenin敲除部分减轻DC细胞Ubc13敲除小鼠中T细胞的过度激活。 我们发现DC细胞Ubc13敲除小鼠的抗肿瘤免疫力显著高于野生型对照小鼠。这些数据表明靶向DC细胞中的Ubc13可以作为提高抗肿瘤免疫的有效方法和策略。