Molecular and Cellular Mechanisms of IL-17 Signaling

描述（由申请人提供）：多发性硬化症（MS）是一种中枢神经系统（CNS）的慢性炎症性脱髓鞘疾病。实验性自身免疫性脑脊髓炎（EAE）被广泛用于分析MS的分子机制和开发新的治疗策略。EAE的研究有助于确定自身免疫性中枢神经系统导向炎症性疾病发展的事件序列，包括起始阶段（中枢神经系统外神经抗原反应性CD4 T淋巴细胞的激活和扩增）和效应阶段（中枢神经系统内神经抗原反应性CD4 T淋巴细胞的募集和再激活以及随后的炎症反应）。最近的研究表明，TGF /IL-6/IL-23驱动的CD4 T细胞谱系-Th17细胞在EAE的发展中起着关键作用。由Th17产生的IL-17作为炎症细胞因子，通过上调细胞因子和趋化因子的表达，在EAE的发病过程中发挥重要作用。缺乏IL-17或IL-17受体的小鼠EAE明显受到抑制。利用il -17特异性抑制的研究表明，il -17介导的信号传导在EAE的效应期起着关键作用。我们和其他人已经发现Act1是一个重要的IL-17信号分子，当IL-17刺激时，通过SEFIR-SEFIR结构域相互作用招募到IL-17受体（IL-17R）。我们最近报道了Act1是一种新的真正的U-box E3泛素连接酶，其活性对il -17介导的信号传导和炎症基因表达至关重要。虽然IL-17在EAE的发展中起着至关重要的作用，但目前尚不清楚IL-17在不同细胞室中介导的信号如何参与EAE的中枢神经系统。我们现在表明，Th17细胞在缺乏act1的小鼠中大量产生，通常会浸润缺乏act1的中枢神经系统，但不能招募造血来源的淋巴细胞、中性粒细胞和巨噬细胞进入中枢神经系统。重要的是，内皮细胞或巨噬细胞/小胶质细胞中缺乏Act1并没有实质性地影响EAE的发展。然而，无论是通过主动免疫还是髓磷脂特异性Th17细胞过继性转移诱导EAE，神经外胚层来源的中枢神经系统驻地细胞（包括星形胶质细胞、少突胶质细胞和神经元）靶向性Act1缺乏均可显著降低EAE的严重程度。基于这些发现，我们假设il -17诱导的不同中枢神经系统驻留细胞中act1介导的信号在自身免疫性中枢神经系统炎症过程中协调介导白细胞募集、脱髓鞘和神经退行性变。为了验证这一假设，我们提出以下具体目的：目的1：研究IL-17信号在th17介导的EAE发病机制中的细胞机制。目的2：阐明Act1介导IL-17信号转导的分子机制，开发诱骗（抑制）肽作为治疗中枢神经系统炎症、脱髓鞘和神经退行性变的新策略。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) is widely used to dissect molecular mechanisms of MS and to develop new therapeutic strategies. Studies of EAE have helped define the sequence of events involved in the development of autoimmune CNS-directed inflammatory diseases, including the initiation stage (activation and expansion of neuroantigen-reactive CD4 T lymphocytes outside of CNS) and effector stage (recruitment and reactivation of neuroantigen-reactive CD4 T lymphocytes and subsequent inflammatory response within CNS). Recent studies have shown that a distinct CD4 T cell lineage -Th17 cells driven by TGF /IL-6/IL-23 play a critical role in the development of EAE. IL-17 produced by Th17 functions as an inflammatory cytokine and plays an important role in the pathogenesis of EAE by upregulating the expression of cytokines and chemokines. EAE is markedly suppressed in mice lacking IL-17 or IL-17 receptor. Studies using IL-17-specific inhibition indicate that IL-17-mediated signaling plays a critical role in the effector stage of EAE. We and others have identified Act1 as an essential IL-17 signaling molecule recruited to IL-17 receptor (IL-17R) upon IL-17 stimulation through SEFIR-SEFIR domain interaction. We recently reported that Act1 is a novel bona fide U-box E3 ubiquitin ligase, whose activity is essential for IL-17-mediated signaling and inflammatory gene expression. While IL-17 plays an essential role in the development of EAE, it remains unclear how IL-17-mediated signaling in different cellular compartments participates in the CNS in EAE. We now show that Th17 cells are robustly generated in Act1-deficient mice and normally infiltrate the Act1-deficient CNS but fail to recruit hematogenously derived lymphocytes, neutrophils, and macrophages into the CNS. Importantly, Act1 deficiency in endothelial cells or in macrophages/microglia did not substantially impact the development of EAE. However, targeted Act1 deficiency in neuroectoderm derived CNS resident cells (including astrocytes, oligodendrocytes and neurons) resulted in significantly reduced EAE severity whether EAE was induced by active immunization or adoptive transfer of myelin-specific Th17 cells. Based on these findings, we hypothesize that IL-17-induced Act1-mediated signaling in different CNS resident cells coordinately mediate leukocyte recruitment, demyelination and neurodegeneration during autoimmune induced inflammation of the CNS. To test this hypothesis, we propose the following Specific Aims: Aim 1: Investigate the cellular mechanism of IL-17 signaling in the Th17-mediated pathogenesis of EAE. Aim 2: Elucidate the molecular mechanism by which Act1 mediates IL-17 signaling and develop decoy (inhibitory) peptides as a new therapeutic strategy for CNS inflammation, demyelination and neurodegeneration.