Human Autoimmunity and Genetic Defects in N-Glycosylation

遗传信息从DNA流向大分子结构--主导力量 在生命的分子组织中。然而，几乎所有的细胞表面和分泌 后生动物中的蛋白质通过在 内质网/高尔基体分泌途径。我们发现代谢产物对高尔基体N-糖基化的可用性 途径对大分子的组装施加自主控制 细胞表面的复合体，以这种能力，作用于信号和基因的上游 影响细胞生长、分化和疾病状态的基因表达。分支机构 和每个蛋白质分子的N-糖链数量协同调节与半乳糖凝集素的结合 因此，表面糖蛋白在体内的分布、聚集和内吞作用 可预见的方式。N-糖基化的遗传干扰促进T细胞高活性 通过增强T细胞受体聚集性/信号转导和 降低生长抑制剂CTLA-4的表面保留率。在人类中，一种单倍型 MGAT1协同作用将糖蛋白中N-糖链分支减少约20% 与CTLA-4的一个等位基因相互作用，使N-糖链数量减少约50%，增加 多发性硬化(MS)和类风湿性关节炎(RA)的风险增加~2倍。两个人 变异体有望独立降低CTLA-4对Galectins的亲和力，实际上， 它们协同作用，限制表面CTLA-4表面水平。疾病推广是 仅在拥有这两种变体的受试者中观察到，并似乎由 有缺陷的CTLA-4等位基因的拷贝数。高尔基体的代谢补充剂 抑制小鼠T细胞功能和自身免疫，挽救N-糖基化缺陷 在T细胞生长和CTLA-4表面滞留与MS和RA相关。我们的数据 提示在人类自身免疫的病因学中， 有条件地抑制CTLA-4中高尔基体GlcNAc分支和N-X-S/T位点的使用，以及 为环境和遗传疾病提供治疗策略和分子机制 互动。为了将这些结果推广到人类身上，我们提出了以下目标。特定的 目标1将确定改变N-糖链分支的遗传变异。特定目标2将 研究MS相关等位基因对N-糖链分支的调节作用 它们与目标1中确定的变体的相互作用。特定目标3将研究合作 改变N-糖链分支的变异体与CTLA-4 Ala17的相互作用 以及相关的等位基因。特殊目标4将检查来自于 多发性硬化症和1型糖尿病患者的特定目标为1-3。

Genetic information flows from DNA to macromolecular structures - the dominant force in the molecular organization of life. However, virtually all cell surface and secreted proteins in metazoans are modified by the addition of complex carbohydrates in the ER/Golgi secretory pathway. We find that metabolite availability to the Golgi N-glycosylation pathway exerts autonomous control over the assembly of macromolecular complexes on the cell surface, and in this capacity, acts upstream of signaling and gene expression to influence cell growth, differentiation and disease states. The branching and number of N-glycans per protein molecule cooperate to regulate binding to galectins and thereby the distribution, clustering and endocytosis of surface glycoproteins in a predictable manner. Genetic disruption of N-glycosylation promotes T cell hyper-activity and autoimmune disease in mice by enhancing T cell receptor clustering/signaling and reducing surface retention of the growth inhibitor CTLA-4. In humans, a haplotype of MGAT1 that reduces N-glycan branching in glycoproteins by ~20% synergistically interacts with an allele of CTLA-4 that reduces N-glycan number by ~50%, increasing the risk of Multiple Sclerosis (MS) and Rheumatoid Arthritis (RA) by ~2 fold. The two variants are expected to independently reduce CTLA-4 affinity for galectins and indeed, they act cooperatively to limit surface CTLA-4 surface levels. Disease promotion is observed only in subjects who harbor both variants, and appears to be titrated by the number of copies of the defective CTLA-4 allele. Metabolic supplementation to the Golgi inhibits T cell function and autoimmunity in mice and rescues the N-glycosylation defects in T cell growth and CTLA-4 surface retention associated with MS and RA. Our data suggests synergism in the etiology of human autoimmunity between polymorphisms that conditionally suppress Golgi GlcNAc branching and N-X-S/T site usage in CTLA-4, and provides a therapeutic strategy and molecular mechanism for environmental and genetic interactions. To extend these results in humans we propose the following aims. Specific Aim 1 will identify genetic variants that alter N-glycan branching. Specific Aim 2 will investigate the regulation of N-glycan branching by MS associated alleles and their interaction with variants identified in Aim 1. Specific Aim 3 will investigate for cooperative interactions between variants that alter N-glycan branching and CTLA-4 Ala17 and related alleles. Specific Aim 4 will examine for genetic interaction of variants from Specific Aim's 1-3 in Multiple Sclerosis and Type 1 Diabetes co-horts.