Our published data in mice has revealed that the simple sugar and dietary supplement N- acetylglucosamine (GlcNAc) inhibits T cell function and autoimmunity by enhancing N-glycosylation in T cells. Virtually all cell surface and secreted proteins in metazoans are modified by the addition of complex carbohydrates in the ER/Golgi secretory pathway, imparting substantial molecular information not encoded by the genome. We find that genetic, metabolic and environmental regulation of Golgi N-glycosylation controls macromolecular complexes on the cell surface to influence cell growth, differentiation and disease states. The branching and number of N-glycans per protein molecule cooperate to regulate binding to galectins, forming a galectin-glycoprotein lattice that controls the distributin, clustering and endocytosis of surface glycoproteins in a predictable manner. N-glyan branching deficiency induces T cell hyper-activity and spontaneous autoimmune disease in mice by enhancing T cell receptor clustering/signaling, reducing surface retention of the growth inhibitors CTLA-4 and TGF-?RI/II and promoting differentiation into pro-inflammatory TH1/TH17 cells. In humans, multiple genetic and environmental risk factors for Multiple Sclerosis (MS) converge to dysregulate N- glycosylation and CTLA-4 surface retention. These include genetic variants in interleukin-7 receptor-?, interleukin-2 receptor-?, MGAT1, MGAT5 and CTLA-4 as well as Vitamin D3 and metabolic production of UDP-GlcNAc, the substrate for MGAT1 and MGAT5. Rescuing N-glycan branching deficiency in T cells in vitro and in vivo by metabolically increasing UDP-GlcNAc with the dietary supplement N-acetylglucosamine (GlcNAc), suppresses T cell growth, enhances CTLA-4 and TGF-?RI/II surface expression, blocks TH1/TH17 differentiation, inhibits MS and autoimmune diabetes models and rescues N-glycan branching deficiency induced by MS genetic risk factors. Therapeutic supplementation to N-glycan biosynthesis with GlcNAc may provide a personalized medicine approach to suppress an underlying molecular defect promoting human autoimmunity. Here we propose to examine whether oral GlcNAc in humans enhances N-glycan branching to suppress T cell function and induce immune deviation, focusing on individuals with genetic polymorphisms that promote MS and down-regulate N-glycan branching in T cells.
Specific Aim 1 examines whether in vitro GlcNAc regulates hypomorphic N-glycan branching in male vs female human T cells to suppress pro- autoimmune TH1/TH17 cells while enhancing anti-autoimmune T regulatory cells.
Specific Aim 2 examines whether oral GlcNAc enhances N-glycan branching to suppress pro-autoimmune TH1/TH17 responses while enhancing anti-autoimmune T regulatory cells in MS patients with genetic defects in N-glycosylation.
Multiple Sclerosis is an autoimmune disease resulting from complex interactions between genetic background of the individual and his/her environment. Our combined data suggests that genetic deficiency in a pathway that controls the addition of specific sugars to proteins (i.e. protein glycosylation) leads to immune hyperactivity and promotes autoimmunity in mice and humans. Supplementing human and mouse cells with the simple sugar and dietary supplement N-acetylglucosamine normalizes protein glycosylation and/or immune hyperactivity. N- acetylglucosamine is also active when given orally to mice, increasing protein glycosylation and suppressing immune hyper-activity and models of Multiple Sclerosis. Here we examine whether oral N-acetylglucosamine in humans similarly enhances protein glycosylation and suppresses immune hyper-activity. If confirmed, N-acetylglucosamine may provide a simple inexpensive oral therapy in Multiple Sclerosis that directly targets an underlying mechanism promoting disease.
|Araujo, Lindsey; Khim, Phillip; Mkhikian, Haik et al. (2017) Glycolysis and glutaminolysis cooperatively control T cell function by limiting metabolite supply to N-glycosylation. Elife 6:|
|Mkhikian, Haik; Mortales, Christie-Lynn; Zhou, Raymond W et al. (2016) Golgi self-correction generates bioequivalent glycans to preserve cellular homeostasis. Elife 5:|