Regulation of T-cell function and autoimmune inflammation by deubiquitinase CYLD

描述(申请人提供)：T细胞对外来抗原有效反应，但对自身组织和正常肠道菌群有耐受性。T细胞的不适当激活或分化可导致严重的免疫紊乱，包括自身免疫和炎症。因此，更好地了解调节T细胞活化和耐受的分子机制对于合理设计免疫性疾病的治疗方法是非常重要的。这项应用的总体目标是了解一种新发现的脱泛素酶(DUB)，CyLD，通过其调节T细胞功能和自身免疫性炎症的分子和细胞机制。在目前的资助期间，我们已经取得了开创性的发现，确立了CyLD是T细胞激活和自身免疫性炎症的关键调节因子。CyLD缺陷的T细胞对TCR刺激反应强烈，CyLD基因敲除(CyLD-/-)小鼠会自发发生肠道炎症，这是人类炎症性肠病(IBD)的主要特征。CyLD-/-小鼠还经历了严重的骨丢失，这是IBD的主要肠道外并发症和结肠炎的动物模型。此外，我们的初步研究表明，CyLD的丢失使小鼠对实验性自身免疫性脑脊髓炎(EAE)的诱导高度敏感。因此，CyLD是T细胞功能和自身免疫性炎症性疾病的主要调节因子。本次继续申请中提出的研究是基于我们实验室强大的初步和已发表的数据。特别是，我们已经证明，T细胞中CyLD的丢失会导致核因子-kB的结构性激活，核因子-kB是一种转录因子，介导T细胞的激活和存活，并参与许多炎症性疾病。CyLD-/-T细胞还表现出显著的共刺激分子ICOS的减弱，ICOS对于诱导T细胞耐受和调节T细胞分化至关重要。与这些分子研究一致，我们发现CyLD-/-T细胞对肠道微生物的耐受性似乎存在缺陷，因为它们过继转移到淋巴细胞缺陷的Rag1/-小鼠会导致严重的结肠炎。此外，CyLD-/-小鼠产生异常高水平的炎性Th17和Th1细胞，伴随着EAE反应的增强。我们已获得初步证据表明，CyLD调节巨噬细胞对TLR刺激的特定细胞因子亚群表达的反应，已知的细胞因子亚集调节Th1和Th17的分化。基于这些发现，我们假设CyLD调控与T细胞激活和分化以及耐受诱导有关的关键信号事件。我们将落实三个具体目标，实现总目标。(1)探讨CyLD介导的T细胞内NF-kB调控的分子机制及其功能意义。(2)研究CyLD调节T细胞耐受和炎性T细胞分化的分子和细胞机制。(3)探讨CyLD调节骨质侵蚀的免疫学和破骨细胞内在机制。 公共卫生相关性：T细胞对于针对微生物感染的免疫反应至关重要。然而，由于遗传或环境因素而导致的T细胞失控激活，可能会导致严重的免疫紊乱，包括自身免疫和慢性炎症。这项研究的重点是了解脱泛素酶CyLD如何调节T细胞的激活和耐受，从而防止自身免疫和炎症的发展。这些知识对于合理设计有效的免疫疗法是很重要的。

DESCRIPTION (provided by applicant): T cells effectively respond to foreign antigens but are tolerant to self-tissues and normal enteric flora. Inappropriate activation or differentiation of T cells can lead to severe immunological disorders, including autoimmunity and inflammation. Thus, a better understanding of the molecular mechanisms regulating T-cell activation and tolerance is important for rational design of therapies for immunological diseases. The overall objective of this application is to understand the molecular and cellular mechanisms by which a newly identified deubiquitinase (DUB), CYLD, regulates T-cell function and autoimmune inflammation. During the current funding period, we have made seminal findings that establish CYLD as a pivotal regulator of T-cell activation and autoimmune inflammation. CYLD-deficient T cells are hyper-responsive to TCR stimulation, and the CYLD knockout (CYLD-/-) mice spontaneously develop intestinal inflammation with major features of human inflammatory bowel disease (IBD). The CYLD-/- mice also experience severe bone loss, which is known as a major extra-intestinal complication of IBD and animal model of colitis. Moreover, our preliminary studies reveal that loss of CYLD renders mice hypersensitive to the induction of experimental autoimmune encephalomyelitis (EAE). Thus, CYLD is a master regulator of T-cell function and autoimmune inflammatory diseases. The studies proposed in this continuation application are based on strong preliminary and published data from our laboratory. In particular, we have shown that loss of CYLD in T cells causes constitutive activation of NF-kB, a transcription factor mediating T-cell activation and survival and being involved in many inflammatory disorders. The CYLD-/- T cells also display marked attenuation of the costimulatory molecule ICOS, which is crucial for the induction of T-cell tolerance and regulation of T-cell differentiation. Consistent with these molecular studies, we have found that the CYLD-/- T cells appear to be defective in tolerance to enteric microbes, since their adoptive transfer into lymphocyte-deficient Rag1-/- mice induces severe colitis. Furthermore, the CYLD-/- mice produce aberrantly high levels of inflammatory Th17 and Th1 cells, coupled with heightened EAE response. We have obtained preliminary evidence that CYLD regulates macrophage response to TLR-stimulated expression of a specific subset of cytokines known to regulate Th1 and Th17 differentiation. Based on these findings, we hypothesize that CYLD regulates key signaling events involved in T-cell activation and differentiation as well as tolerance induction. We will perform three specific aims to accomplish our overall objective. (1) Examine the molecular mechanism and functional significance of CYLD-mediated NF-kB regulation in T cells. (2) Characterize the molecular and cellular mechanisms by which CYLD regulate T-cell tolerance and inflammatory T-cell differentiation. (3) Examine the immunological and osteoclast-intrinsic mechanisms by which CYLD regulates bone erosion. PUBLIC HEALTH RELEVANCE: T cells are vital for immune responses against microbial infections. However, deregulated T cell activation, due to genetic or environmental factors, can lead to severe immunological disorders, including autoimmunity and chronic inflammation. The focus of this research project is to understand how a deubiquitinase, CYLD, regulates T-cell activation and tolerance, thereby preventing the development of autoimmunity and inflammation. This knowledge is important for rational design of effective immunological therapies.