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

描述(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。单基因系统性红斑狼疮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唯一有用的。TREX1/DNase III是一种ER相关的核酸外切酶，是天然免疫的负调节因子，TREX1是SLE最高的单基因连锁。奇怪的是，大多数与SLE相关的TREX1突变并不影响其DNase活性，而是破坏其ER定位结构域。TREX1系统性红斑狼疮的分子病因尚不清楚。我们最近发现了TREX1的一个DNA酶不依赖的功能，它是调节一个新的内质网相关反应所必需的。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ER的自体配体，以及几种针对TREX1 SLE免疫发病机制的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TREX1突变具有缺陷的ER定位结构域，通过刺激产生免疫原性自身配体的ER相关反应而导致SLE。此外，我们的生化数据表明，这些自体配体是游离的葡聚糖。这种反应的治疗抑制或下游的先天免疫信号被预测可以改善TREX1疾病。我们将从以下三个方面阐明TREX1的这一新功能。目的1)对由TREX1 SLE突变激活的一种新的ER相关反应进行遗传和生化剖析，该反应可导致游离多糖的释放。我们将使用初步研究中建立的补救试验来检测TREX1、SLE和其他突变，以确定TREX1中对于免疫激活和释放游离多糖至关重要的残基。我们还将用生化方法剖析TREX1与其调控的内质网相关的糖分解代谢反应之间的相互作用。目的2)确定TREX1 SLE突变体产生的游离糖如何触发自身免疫。我们已经建立了一种基于活性的免疫分析方法，我们将用它来确定作为TREX1 SLE自身配体的游离糖的结构细节和免疫原性，以及相应的免疫信号通路。目的3)在治疗上减少TREX1-/-小鼠和TREX1-SLE突变患者细胞中游离糖的释放或抑制TBK1信号转导。我们将通过治疗靶向TREX1系统性红斑狼疮发病机制中的关键酶，在体内进一步验证我们的假设。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的功能，以及将游离糖确定为SLE中一种新的自体配体。此应用程序将 还通过“重新利用”针对TREX1 SLE中涉及的关键酶开发的现有化合物来揭示和测试治疗SLE的新靶点。

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.