Age-related structural alterations in loss of self-tolerance to a3(IV) collagen

年龄相关的结构改变导致对 a3(IV) 胶原蛋白自我耐受性丧失

• 批准号: 7116004
• 负责人: DORIN-BOGDAN BORZA
• 金额: $ 21.63万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7116004
• 关键词: aging; autoantibody; autoantigens; collagen; kidney

DESCRIPTION (provided by applicant): Anti-GBM antibody (Ab) nephritis is an autoimmune disease mediated by autoAbs that bind to the NC1 domain of a3(IV) collagen in the glomerular basement membrane (GBM). Under native conditions, autoAbs bind to the GBM of adult kidneys, but not to the GBM of kidneys from children younger than 3-5 years, despite expression of a3(IV) collagen. The objective of this proposal is to investigate the role of age-related changes in the structure and immunoreactivity of a3(IV) collagen and loss of tolerance to a3(IV) collagen in anti-GBM disease. We showed that epitope crypticity depends on the quaternary organization of the a3NC1 domains, which exist in tissues as a3a4a5NC1 hexamer complexes. We found that the adult GBM contains a3NC1 domains in two distinct molecular forms: cross-linked D-hexamers inert toward anti-a3NC1 autoAbs, and non-crosslinked M-hexamers dissociable by autoAbs. Preliminary studies showed that mice immunized with autologous native a3NC1 hexamers develop a limited immune response and no renal disease, but structural alterations of the antigen elicited a robust autoAb response and severe autoimmune nephritis. Specific Aim 1 is to determine the molecular basis of the age-dependent changes in the structure and immunoreactivity of a3(IV) collagen. We hypothesize that: a) all a3(IV) collagen in the young GBM is immunologically privileged by molecular reinforcement of its quaternary structure, b) the increase in GBM immunoreactivity with age is due to an accumulation of post-translational changes in a3(lV) collagen. Specific Aim 2 is to establish the role of age-related changes of a3(IV) collagen structure in the loss of tolerance to this antigen. We hypothesize that the absence of stabilizing cross-links or post-translational modifications of a3(IV) collagen are necessary for autoimmune pathology by circumventing self-tolerance. This will be achieved by in vitro studies, comparing the structure and immunoreactivity of a3(IV) collagen from young versus mature kidneys, and in vivo studies in mice models, comparing the immunogenicity and pathogenicity of self-antigen from young versus mature GBM. The findings will increase our knowledge of the molecular mechanisms implicated in the establishment and loss of immune tolerance to long-lived extracellular matrix antigens, and the role of post-translational modifications and autoantigen "aging" in the autoimmune etiology. New targets for prevention or therapeutic intervention may be identified as a result.

描述（由申请人提供）：抗GBM抗体（Ab）肾炎是一种自身免疫性疾病，由与肾小球基底膜（GBM）中α 3（IV）胶原蛋白的NC 1结构域结合的自身抗体介导。在天然条件下，autoAb与成人肾脏的GBM结合，但不与3-5岁以下儿童肾脏的GBM结合，尽管表达α 3（IV）胶原。本研究的目的是研究年龄相关的α 3（IV）胶原蛋白的结构和免疫反应性变化以及抗GBM疾病中对α 3（IV）胶原蛋白耐受性的丧失。我们表明，表位的隐蔽性取决于四级组织的α 3 NC 1结构域，存在于组织中的α 3 α 4 α 5 NC 1六聚体复合物。我们发现，成人GBM含有两种不同分子形式的α 3 NC 1结构域：对抗α 3 NC 1自身抗体呈惰性的交联D-六聚体和可被自身抗体解离的非交联M-六聚体。初步研究显示，用自体天然a3 NC 1六聚体免疫的小鼠产生有限的免疫应答并且没有肾脏疾病，但是抗原的结构改变引起强烈的自身抗体应答和严重的自身免疫性肾炎。具体目标1是确定a3（IV）胶原蛋白的结构和免疫反应性的年龄依赖性变化的分子基础。我们假设：a）年轻GBM中的所有α 3（IV）胶原蛋白通过其四级结构的分子强化而在免疫学上被豁免，B）GBM免疫反应性随年龄的增加是由于α 3（IV）胶原蛋白中翻译后变化的积累。具体目标2是确定α 3（IV）胶原结构的年龄相关变化在对该抗原的耐受性丧失中的作用。我们假设，缺乏稳定的交联或翻译后修饰的α 3（IV）胶原蛋白是必要的自身免疫性病理学规避自身耐受。这将通过体外研究和小鼠模型中的体内研究来实现，体外研究比较来自年轻与成熟肾脏的α 3（IV）胶原的结构和免疫反应性，体内研究比较来自年轻与成熟GBM的自身抗原的免疫原性和致病性。这些发现将增加我们对与建立和丧失对长寿命细胞外基质抗原的免疫耐受性有关的分子机制的认识，以及翻译后修饰和自身抗原“老化”在自身免疫病因中的作用。因此，可以确定预防或治疗干预的新目标。