Post Translational Modifications in Tolerance and Autoimmunity

描述（由申请人提供）：本提案是AR 48120“耐受性和自身免疫性的翻译后修饰”的修订版竞争性延续。我们最初的建议详细介绍了一种新的自我蛋白质的性质，可能会赋予自身免疫反应的系统性红斑狼疮（SLE）的小鼠模型。正如我们最初的提议中所介绍的，翻译后蛋白质修饰（称为异戊酰基）可以在pH和温度的生理条件下自发发生。虽然这种修饰已经在细胞中存在多年，但对自身蛋白质内这种修饰的免疫性仅由我们的实验室描述。这些修饰发生在所有细胞类型中，并且在老化和应激的淋巴细胞中增强。与我们的工作相关的是，针对其他蛋白质修饰的自身抗体，特别是瓜氨酸蛋白，已成为自身免疫综合征（如类风湿性关节炎）的诊断方法。这个提议的总体目的是确定自身蛋白内自发的生物化学修饰如何改变通常对自身蛋白建立的免疫耐受性。我们已经确定了蛋白质修饰的两个重要机制如何引起自身免疫。首先，异戊酰修饰的自身抗原可以经历改变的抗原加工，潜在地导致新的隐蔽自身肽的表达。特别地，组蛋白H2B蛋白经历广泛的异戊酰修饰，其可以以这种方式触发自身免疫。第二，在狼疮易感MRL小鼠的细胞中发现细胞内蛋白质修饰的积累，导致异常T细胞过度增殖，并且与自身免疫病理学的发作一致。 本提案将研究异戊酰蛋白修饰如何改变蛋白质的免疫原性和改变淋巴细胞功能的机制。特别是，我们将开发具有条件蛋白修复系统的新型小鼠品系，该系统改变CD4 T细胞中的蛋白质修饰。我们将确定在蛋白质修饰的存在下自身抗原加工是如何改变的，以及修饰的组蛋白如何触发自身抗体反应。这些研究的总体目标是确定翻译后蛋白质修饰在狼疮样自身免疫发生中的作用。 系统性自身免疫性疾病的特征在于针对细胞内蛋白质中的选择组的异常免疫应答。我们工作的重点是确定新的翻译后蛋白质修饰，可能是诱导自身免疫性疾病的关键。通过几种蛋白质修饰（尤其是瓜氨酸）在风湿性疾病中的诊断和临床相关性，这些研究的优先性显而易见。目前的研究集中在蛋白质修饰称为“异丙基”，自发发生在真核细胞中，并在细胞应激和炎症的条件下增强。我们以前已经确定了两个狼疮自身抗原，snRNP核糖核蛋白和组蛋白H2B的异戊酰修饰的存在。我们将研究在这种修饰的背景下产生的免疫原性，并确定如何改变自身免疫过程中的异戊酰蛋白修饰时，在体内修复。这项工作的目标是确定自发性蛋白质修饰在B和T细胞免疫耐受和自身免疫病理学中的重要性。

DESCRIPTION (provided by applicant): The present proposal is a revised, competing continuation of AR48120, "Post- Translational Modifications in Tolerance and Autoimmunity". Our original proposal detailed a novel property of self proteins that may confer autoimmune responses in murine models of systemic lupus erythematosus (SLE). As introduced in our original proposal, a post-translational protein modification, termed isoaspartyl, can occur spontaneously under physiologic conditions of pH and temperature. While the modification has been known to exist in cells for many years now, the immunity to such modifications within self proteins has only been described by our laboratory. These modifications occur in all cell types and are enhanced in aged and stressed lymphocytes. With relevance to our work, autoantibodies to other protein modifications, notably citrulline proteins, have become diagnostic for autoimmune syndromes such as rheumatoid arthritis. The overall intent of this proposal is to determine how spontanteous biochemical modifications within self proteins can change the immunologic tolerance that is normally established to self proteins. We have identified how two important mechanisms of protein modification can elicit autoimmunity. First, isoaspartyl modified self antigens can undergo altered antigen processing, potentially leading to the expression of novel cryptic self peptides. In particular, histone H2B protein undergoes extensive isoaspartyl modification that may trigger autoimmunity in this manner. Second, an accumulation of intracellular protein modifications is found in the cells of lupus-prone MRL mice causing abnormal T cell hyperproliferation and is coincident with the onset of autoimmune pathology. The present proposal will examine the mechanisms of how isoaspartyl protein modifications alter immunogenicity of proteins and alter lymphocyte functions. In particular, we will develop novel mouse strains with conditional protein repair systems that alter protein modification in CD4 T cells. We will determine how autoantigen processing is altered in the presence of protein modification and how modified histone protein triggers autoantibody responses. The overall goal of these studies is to identify the roles of posttranslational protein modifications in the genesis of lupus-like autoimmunity.Project Narrative Systemic autoimmune diseases are characterized by aberrant immune responses directed at a select group in intracellular proteins. The focus of our work is to identify novel posttranslational protein modifications that may be critical in the induction of autoimmune disease. Precedence for these studies is apparent by the diagnostic and clinical relevance of several protein modifications, notably citrulline, in rheumatic disease. The present studies focus on a protein modification termed `isoaspartyl' that occurs spontaneously in eukaryotic cells and is enhanced in conditions of cellular stress and inflammation. We have previously identified the presence of isoaspartyl modifications in two lupus autoantigens, the snRNP ribonucleoprotein and histone H2B. We will examine the immunogenicity that arises in the context of this modification and determine how the course of autoimmunity is altered when isoaspartyl protein modifications are repaired in vivo. The goal of this work is to determine the importance of spontaneous protein modification in B and T cell immune tolerance and autoimmune pathology.