A DNase-independent function of TREX1/DNase III in systemic lupus erythematosus

描述（由申请人提供）：系统性红斑狼疮（SLE）是一种病因复杂的自身免疫性疾病，以多种免疫细胞功能障碍为特征。单基因SLE模型对于疾病发病机制的分子解剖和测试潜在的治疗方法是非常有用的。TREX1/DNase III是一种er相关的外切酶，是先天免疫的负调节因子，TREX1是SLE的最高单基因联系之一。奇怪的是，大多数与SLE相关的TREX1突变并不影响其dna酶活性，而是破坏其ER定位域。TREX1型SLE的分子病因尚不清楚。我们最近发现TREX1的一种与dna酶无关的功能，它是调节一种新的er相关反应所必需的。我们还在携带TREX1 SLE突变的细胞中发现了一种以前未知的来自内质网的自配体，以及几种针对TREX1 SLE免疫发病机制关键酶的小分子抑制剂。基于已发表的和初步的数据，我们假设具有内质网定位域缺陷的TREX1突变通过刺激内质网相关反应产生免疫原性自配体来促进SLE。此外，我们的生化数据表明，这些自配体是游离聚糖。治疗性抑制该反应或下游先天免疫信号预计可改善TREX1疾病。我们将从以下三个具体目标来阐明TREX1的这种新功能。目的1)对TREX1 SLE突变激活的一种新的er相关反应进行遗传和生化解剖，该反应导致游离聚糖的释放。我们将使用在初步研究中建立的援救试验来检测TREX1 SLE和其他突变，以确定TREX1中对免疫激活和游离聚糖释放至关重要的残基。我们还将从生化角度剖析TREX1与其调节的er相关的聚糖分解代谢反应之间的相互作用。目的2)确定TREX1 SLE突变体产生的游离聚糖如何触发自身免疫。我们已经建立了一个基于活性的免疫分析，我们将使用它来定义游离聚糖作为TREX1 SLE的自配体和相应的免疫信号通路的结构细节和免疫原性潜力。目的3)在治疗上减少Trex1-/-小鼠和Trex1 SLE突变患者细胞中的游离聚糖释放或抑制TBK1信号。我们将通过治疗靶向TREX1 SLE发病机制中涉及的关键酶进一步在体内验证我们的假设。这一建议的意义在于，它提出了TREX1的一个重要但以前未被认识到的功能，以及游离聚糖作为SLE中一种新的自配体的鉴定。这个应用程序将

DESCRIPTION (provided by applicant): System lupus erythematosus (SLE) is an autoimmune disorder of complex etiology characterized by diverse immune cell dysfunction. Monogenic SLE models are uniquely useful for molecular dissection of disease pathogenesis and for testing potential therapies. TREX1/DNase III, an ER-associated exonuclease, is a negative regulator of innate immunity, and TREX1 represents one of the highest monogenic links to SLE. Curiously, most TREX1 mutations associated with SLE do not affect its DNase activity, but rather, disrupt its ER localization domain. The molecular cause for TREX1 SLE is unclear. We recently discovered a DNase- independent function of TREX1 that is required for regulating a novel ER-associated reaction. We also identified a previously unknown self-ligand derived from the ER in cells carrying TREX1 SLE mutations, as well as several small molecule inhibitors that target key enzymes that contribute to the immunopathogenesis of TREX1 SLE. Based on published and preliminary data, we hypothesize that TREX1 mutations with defective ER localization domain contribute to SLE by stimulating an ER-associated reaction that generates immunogenic self-ligands. Moreover, our biochemical data indicate that these self-ligands are free glycans. Therapeutic inhibition of this reaction or downstream innate immune signaling is predicted to ameliore TREX1 disease. We will elucidate this novel function of TREX1 with the following three specific aims. Aim 1) Genetic and biochemical dissection of a novel ER-associated reaction activated by TREX1 SLE mutations, that causes release of free glycans. We will examine TREX1 SLE and other mutations using rescue assays established in preliminary studies to identify residues in TREX1 critically required for immune activation and free glycan release. We will also biochemically dissect the interaction between TREX1 and the ER-associated glycan catabolic reaction it regulates. Aim 2) Determine how free glycan generated by TREX1 SLE mutants trigger autoimmunity. We have established an activity-based immune assay, which we will use to define structural details and immunogenic potential of free glycan as a self-ligand for TREX1 SLE and the corresponding immune signaling pathway. Aim 3) Therapeutically diminish free glycan release or inhibit TBK1 signaling in Trex1-/- mice and TREX1 SLE mutant patient cells. We will further test our hypothesis in vivo by therapeutically targeting key enzymes implicated in TREX1 SLE pathogenesis. The significance of this proposal lies with the fact that it presents an important but previously unrecognized function of TREX1 as well as identification of free glycan as a novel self-ligand in SLE. This application will also reveal and test novel targets for the treatment of SLE through 're-purposing' existing compounds developed against key enzymes involved in TREX1 SLE.