Molecular and Cellular Mechanisms of IL-17 Signaling

描述(申请人提供)：多发性硬化症(MS)是一种慢性中枢神经系统炎症性脱髓鞘疾病。实验性自身免疫性脑脊髓炎(EAE)被广泛用于研究MS的分子机制和开发新的治疗策略。对EAE的研究有助于确定自身免疫性中枢神经系统炎症性疾病的发生发展过程，包括起始阶段(神经抗原反应性CD4T淋巴细胞在中枢神经系统外的激活和扩增)和效应阶段(神经抗原反应性CD4T淋巴细胞的募集和重新激活以及随后的中枢神经系统内的炎症反应)。最近的研究表明，由转化生长因子/IL-6/IL-23驱动的一种独特的CD4T细胞系-Th17细胞在EAE的发生发展中起着关键作用。Th17产生的IL-17是一种炎性细胞因子，通过上调细胞因子和趋化因子的表达，在EAE的发病机制中发挥重要作用。在缺乏IL-17或IL-17受体的小鼠中，EAE明显受到抑制。使用IL-17特异性抑制的研究表明，IL-17介导的信号转导在EAE的效应阶段起着关键作用。我们和其他人已经确定Act1是一个重要的IL-17信号分子，通过SEFIR-SEFIR结构域的相互作用被IL-17受体(IL-17R)招募到IL-17刺激。我们最近报道了Act1是一个新的真正的U-box E3泛素连接酶，它的活性对于IL-17介导的信号转导和炎症基因的表达是必不可少的。虽然IL-17在EAE的发生发展中起着重要作用，但IL-17介导的不同细胞亚区的信号如何参与EAE的中枢神经系统尚不清楚。我们现在表明，Th17细胞在Act1缺陷小鼠中旺盛地生成，正常情况下渗透到Act1缺陷的CNS，但无法招募血源性淋巴细胞、中性粒细胞和巨噬细胞进入CNS。重要的是，内皮细胞或巨噬细胞/小胶质细胞中的Act1缺乏对EAE的发展没有实质性的影响。然而，无论是主动免疫还是过继转移髓鞘特异性Th17细胞，神经外胚层来源的CNS驻留细胞(包括星形胶质细胞、少突胶质细胞和神经元)中的靶向性Act1缺失都能显著降低EAE的严重程度。基于这些发现，我们推测，在自身免疫诱导的中枢神经系统炎症过程中，IL-17诱导的不同CNS驻留细胞中的Act1介导的信号协同介导了白细胞募集、脱髓鞘和神经变性。为了验证这一假说，我们提出了以下具体目标：目的1：探讨IL-17信号在Th17介导的EAE发病机制中的细胞机制。目的：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、脱髓鞘和神经变性的新策略。

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.