The Role of Transmethylation Reactions in Autoimmunity

描述（由申请人提供）：该项目的重点是确定转甲基化在与系统性自身免疫相关的先天性和适应性免疫反应中的作用。这是免疫学研究的一个新领域，基于我们和其他人最近的研究，表明抑制甲基转移会影响正常的免疫和自身免疫反应。我们假设转甲基化对于炎症和免疫反应是至关重要的，并且阻断这种翻译后过程可以减少系统性自身免疫。为了支持这一点，我们在已发表的和初步的研究中特别记录了S-腺苷-L-高半胱氨酸水解酶（SAHase）（一种参与转甲基化的主要酶）的抑制，通过减少参与TCR信号传导的几种关键蛋白的磷酸化/活化而导致免疫抑制。引人注目的是，这种效应在CD 4 T细胞中而不是CD 8 T细胞中被注意到，并且与Vav 1的精氨酸甲基化降低相关。我们还证明，通过抑制转甲基化，不同TLR配体的刺激和随后的炎性细胞因子的产生显著减少。更重要的是，用可逆性SAHase抑制剂治疗器官特异性自身免疫小鼠模型（EAE）和狼疮小鼠模型（MRL-Faslpr和BXSB）显著降低了疾病的发生率、严重程度和进展。在这里，我们建议进行机制研究，以进一步确定蛋白质甲基化影响正常和自身免疫反应的特异性和途径，具有以下三个具体目标：1）确定PRMT（蛋白质精氨酸甲基转移酶）成员存在于T细胞中，鉴定使CD 4 T细胞中的Vav 1甲基化的特异性PRMT，并确定特异性PRMT在T细胞，B细胞，和巨噬细胞功能; 2）确定转甲基化抑制通过其干扰被认为参与狼疮发病机制的核酸及其复合物对炎性介质的TLR依赖性和TLR非依赖性诱导的分子途径;和3）表征在狼疮模型中疾病进展期间由于转甲基化抑制而发生的细胞和功能变化。这些研究将大大提高我们对翻译后修饰如何影响正常和异常免疫反应的认识，并有可能确定治疗自身免疫性疾病的新靶点。 公共卫生相关性：转甲基化等翻译后修饰极大地扩展了蛋白质的功能库，并对免疫细胞功能产生关键影响。我们的初步研究表明，转甲基化是T细胞，B细胞和巨噬细胞的完全激活所必需的，重要的是，是器官特异性和系统性自身免疫性疾病的进展所必需的。在本申请中，我们建议进一步定义转甲基化促进免疫细胞活化和狼疮样系统性自身免疫的机制。这项工作有可能为这种疾病和其他自身免疫性疾病确定新的治疗靶点。

DESCRIPTION (provided by applicant): This project focuses on defining the role of transmethylation in the innate and adaptive immune responses relevant to systemic autoimmunity. This is a new area of immunological research that is based on recent studies by us and others showing that inhibition of transmethylation affects normal immune and autoimmune responses. We hypothesize that transmethylation is critical for inflammation and immune responses and that blockade of this post-translational process can curtail systemic autoimmunity. In support of this, we have specifically documented in published and preliminary studies that inhibition of S-adenosyl-L-homocysteine hydrolase (SAHase), a major enzyme involved in transmethylation, leads to immunosuppression by reducing phosphorylation/activation of several key proteins involved in TCR signaling. Strikingly, this effect was noted in CD4, but not CD8 T cells, and correlated with reduced arginine methylation of Vav1. We also documented that stimulation by diverse TLR ligands and the consequent production of inflammatory cytokines was significantly reduced by inhibition of transmethylation. More importantly, treatment of an organ-specific autoimmune mouse model (EAE) and lupus mouse models (MRL-Faslpr and BXSB) with a reversible SAHase inhibitor markedly reduced the incidence, severity, and progression of disease. Here, we propose to perform mechanistic studies to further define the specificity and pathways by which protein methylation affects normal and autoimmune responses with the following three specific aims: 1) determine what PRMT (protein arginine methyltransferase) members are present in T cells, identify the specific PRMT(s) that methylates Vav1 in CD4 T cells, and determine the role of specific PRMTs in T cell, B cell, and macrophage function; 2) define the molecular pathways by which transmethylation inhibition interferes with TLR-dependent and TLR-independent induction of inflammatory mediators by nucleic acids and complexes thereof, thought to be involved in lupus pathogenesis; and 3) characterize the cellular and functional changes that occur due to transmethylation inhibition during disease progression in lupus models. These studies should significantly advance our knowledge of how post-translational modifications affect normal and abnormal immune responses, and have the potential for identifying novel targets for the treatment of autoimmune diseases. PUBLIC HEALTH RELEVANCE: Post-translational modifications such as transmethylation greatly expand the functional repertoire of proteins and have critical effects on immune cell function. Our preliminary studies indicate that transmethylation is required for the full activation of T cells, B cells and macrophages and, importantly, is necessary for the progression of both organ-specific and systemic autoimmune diseases. In this application, we propose to further define the mechanisms by which transmethylation promotes immune cell activation and lupus-like systemic autoimmunity. This work has the potential of identifying novel therapeutic targets for this and other autoimmune diseases.