N-Acetylglucosaminyltransferase V (Mgat5)-Mediated N-Glycosylation Negatively Regulates Th1 Cytokine Production by T Cells

Abstract

The differentiation of naive CD4+ T cells into either proinflammatory Th1 or proallergic Th2 cells strongly influences autoimmunity, allergy, and tumor immune surveillance. We previously demonstrated that β1,6GlcNAc-branched complex-type (N-acetylglucosaminyltransferase V (Mgat5)) N-glycans on TCR are bound to galectins, an interaction that reduces TCR signaling by opposing agonist-induced TCR clustering at the immune synapse. Mgat5−/− mice display late-onset spontaneous autoimmune disease and enhanced resistance to tumor progression and metastasis. In this study we examined the role of β1,6GlcNAc N-glycan expression in Th1/Th2 cytokine production and differentiation. β1,6GlcNAc N-glycan expression is enhanced by TCR stimulation independent of cell division and declines at the end of the stimulation cycle. Anti-CD3-activated splenocytes and naive T cells from Mgat5−/− mice produce more IFN-γ and less IL-4 compared with wild-type cells, the latter resulting in the loss of IL-4-dependent down-regulation of IL-4Rα. Swainsonine, an inhibitor of Golgi α-mannosidase II, blocked β1,6GlcNAc N-glycan expression and caused a similar increase in IFN-γ production by T cells from humans and mice, but no additional enhancement in Mgat5−/− T cells. Mgat5 deficiency did not alter IFN-γ/IL-4 production by polarized Th1 cells, but caused an ∼10-fold increase in IFN-γ production by polarized Th2 cells. These data indicate that negative regulation of TCR signaling by β1,6GlcNAc N-glycans promotes development of Th2 over Th1 responses, enhances polarization of Th2 cells, and suggests a mechanism for the increased autoimmune disease susceptibility observed in Mgat5−/− mice.

Functions of cell surface galectin-glycoprotein lattices

“…Multivalent galectin-3-TCR complex lattices limit TCR clustering at the immune synapse by restricting lateral TCR movement within the plane of the membrane, thus increasing agonist threshold for TCR signaling [32,33]. Conversely, deficiency in GlcNAcT-V lowers T-cell activation threshold by enabling TCR clustering and signaling characterized by increased TCR-dependent tyrosine phosphorylation and proliferation [32,33].…”

N-Acetylglucosamine Inhibits T-helper 1 (Th1)/T-helper 17 (Th17) Cell Responses and Treats Experimental Autoimmune Encephalomyelitis

“…Multivalent binding of galectins to N-glycans attached to surface glycoproteins forms a molecular lattice at the cell surface that regulates the clustering and endocytosis of transmembrane receptors and transporters to control cell growth and differentiation (12,(17)(18)(19)(20)(21)(22). In T cells, N-glycan branching inhibits basal and activation signaling through the T cell receptor (TCR) and CD45, promotes growth arrest by cytotoxic T lymphocyte antigen-4 (CTLA-4), and enhances T-helper 2 (Th2) over T-helper 1 (Th1) differentiation (12,21,(23)(24)(25)(26)(27)(28). Metabolically increasing availability of substrate (i.e.…”

Validation of Protein Biomarkers to Advance the Management of Autoimmune Disorders

“…For example, alterations in the levels of naturally-occurring glycosylation motifs can serve as a marker of inflammation, lymphocyte tolerance and senescence in arthritis (Garcia et al, 2005), viz. increased branching of sugar moieties on alpha-1 acid glycoprotein can act as biomarkers of inflammation, whereas decreased branching of T-cell receptor affects the development of Th1/Th2 cells increasing susceptibility to autoimmunity (Havenaar et al, 1998;Morgan et al, 2004).…”