Regulation of T cell function and Autoimmunity by Mgat5

描述（由申请人提供）：多发性硬化症（MS）是一种中枢神经系统自身免疫性疾病，导致轴突多灶性脱髓鞘和相关的轴突损伤。遗传连锁分析已经确定了许多与MS相关的候选位点，但尚未确定具有强关联的非mhc基因。MS的动物模型，实验性自身免疫性脑脊髓炎（EAE），是一种T细胞介导的疾病。beta1, 6n -乙酰氨基葡萄糖转移酶V （Mgat5）是Asn (N)蛋白糖基化途径中的一种酶，是小鼠T细胞活化和自身免疫的有效负调节因子。Mgat5缺陷通过直接增强抗原呈递部位的TCR聚集和信号传导降低T细胞激活阈值。Mgat5-/- T细胞对TCR激动剂的反应过度增殖，Mgat5缺陷小鼠对EAE的易感性增加，并发展为肾脏自身免疫性疾病。由Mgat5启动的GIcNAc a1,6分支优先被两个或多个n -乙酰乳胺单位扩展，这些单位是半乳糖凝集素的配体，半乳糖凝集素是调节T细胞信号传导、增殖和凋亡的碳水化合物结合蛋白家族。TCR相关的Mgat5修饰聚糖与半乳糖凝集素-3结合，参与假定的细胞表面半乳糖凝集素-糖蛋白晶格，抑制TCR募集到抗原呈递位点。为了进一步阐明Mgat5和半凝集素-糖蛋白晶格在调节T细胞功能和自身免疫中的作用，提出了三个具体目标。特异性目标#1将确定T细胞半凝集素-糖蛋白晶格的其他蛋白质和碳水化合物成分及其与T细胞功能和粘附的相关性。从糖基化靶向突变的小鼠中分离出的T细胞将通过荧光显微镜、共免疫沉淀、质谱、信号传导和增殖试验分析细胞功能和受体-凝集素相互作用的变化。特异性Aim #2将探讨Mgat5聚糖在th1和TH2 CD4+、CD8+和记忆T细胞亚群中的调节和功能。Mgat5缺乏对自身免疫性疾病中TH1促进和TH2抑制平衡的影响将被确定。特异性Aim #3将通过过继转移使用EAE诱导来确定改变的T细胞粘附和非T细胞对Mgat5缺陷自身免疫表型的作用。

DESCRIPTION (provided by applicant): Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system that results in multi-focal demyelination of axons and associated axonal damage. Genetic linkage analysis has identified a number of candidate loci associated with MS, but non-MHC genes having a strong association have yet to be identified. The animal model for MS, Experimental Autoimmune Encephalomyelitis (EAE), is a T cell mediated disease. beta1,6N-acetylglucosaminyltransferase V (Mgat5), an enzyme in the Asn (N)-Iinked protein glycosylation pathway, is a potent negative regulator of T cell activation and autoimmunity in mice. Mgat5 deficiency lowers T cell activation thresholds by directly enhancing TCR clustering and signaling at the site of antigen presentation. Mgat5-/- T Cells hyperproliferate in response to TCR agonists and Mgat5 deficient mice display increased susceptibility to EAE and develop kidney autoimmune disease. The GIcNAc a1,6 branching initiated by Mgat5 is preferentially extended by two or more N-acetyllactosamine units, the ligand for galectins, a family of carbohydrate binding proteins that regulate T cell signaling, proliferation and apoptosis. TCR associated Mgat5 modified glycans are bound to galectin-3, participating in a putative cell surface galectin-glycoprotein lattice that inhibits TCR recruitment to the site of antigen presentation. To further elucidate the role of Mgat5 and the galectin-glycoprotein lattice in the regulation of T cell function and autoimmunity, three specific aims are proposed. Specific Aim #1 will identify additional protein and carbohydrate components of the T cell galectin-glycoprotein lattice and their relevance to T cell function and adhesion. T cells isolated from mice with targeted mutations in glycosylation will be analyzed for alterations in cell function and receptor - galectin interactions by florescence microscopy, co-immunoprecipitation, mass spectroscopy, signaling and proliferation assays. Specific Aim #2 will explore the regulation and function of Mgat5 glycans in TH1and TH2 CD4+, CD8+ and memory T cell subsets. The influence of Mgat5 deficiency on the balance between TH1 promotion and TH2 inhibition of autoimmune disease will be determined. Specific Aim #3 will use EAE induction by adoptive transfer to determine the roles of altered T cell adhesion and non-T cells to the Mgat5 deficient autoimmune phenotype.