Metabolic control of T cell immune response through glycans in inflammatory bowel disease

A unique serum IgG glycosylation signature predicts development of Crohn's disease and is associated with pathogenic antibodies to mannose glycan

Inflammatory bowel disease (IBD) is characterized by chronic inflammation in the gut. There is growing evidence in Crohn's disease (CD) of the existence of a preclinical period characterized by immunological changes preceding symptom onset that starts years before diagnosis. Gaining insight into this preclinical phase will allow disease prediction and prevention. Analysis of preclinical serum samples, up to 6 years before IBD diagnosis (from the PREDICTS cohort), revealed the identification of a unique glycosylation signature on circulating antibodies (IgGs) characterized by lower galactosylation levels of the IgG fragment crystallizable (Fc) domain that remained stable until disease diagnosis. This specific IgG2 Fc glycan trait correlated with increased levels of antimicrobial antibodies, specifically anti-Saccharomyces cerevisiae (ASCA), pinpointing a glycome-ASCA hub detected in serum that predates by years the development of CD. Mechanistically, we demonstrated that this agalactosylated glycoform of ASCA IgG, detected in the preclinical phase, elicits a proinflammatory immune pathway through the activation and reprogramming of innate immune cells, such as dendritic cells and natural killer cells, via an FcγR-dependent mechanism, triggering NF-κB and CARD9 signaling and leading to inflammasome activation. This proinflammatory role of ASCA was demonstrated to be dependent on mannose glycan recognition and galactosylation levels in the IgG Fc domain. The pathogenic properties of (anti-mannose) ASCA IgG were validated in vivo. Adoptive transfer of antibodies to mannan (ASCA) to recipient wild-type mice resulted in increased susceptibility to intestinal inflammation that was recovered in recipient FcγR-deficient mice. Here we identify a glycosylation signature in circulating IgGs that precedes CD onset and pinpoint a specific glycome-ASCA pathway as a central player in the initiation of inflammation many years before CD diagnosis. This pathogenic glyco-hub may constitute a promising new serum biomarker for CD prediction and a potential target for disease prevention.

A Unified Atlas of T cell Glycophysiology

Glycans are emerging as important regulators of T cell function but remain poorly characterized across the functionally distinct populations that exist in vivo . Here, we couple single-cell analysis technologies with soluble lectins and chemical probes to interrogate glycosylation patterns on major T cell populations across multiple mouse and human tissues. Our analysis focused on terminal glycan epitopes with immunomodulatory functions, including sialoglycan ligands for Siglecs. We demonstrate that glycosylation patterns are diverse across the resting murine T cell repertoire and dynamically remodelled in response to antigen-specific stimulation. Surprisingly, we find that human T cell populations do not share the same glycoprofiles or glycan remodelling dynamics as their murine counterparts. We show that these differences can be explained by divergent regulation of glycan biosynthesis pathways between the species. These results highlight fundamental glycophysiological differences between mouse and human T cells and reveal features that are critical to consider for glycan-targeted therapies.

"Glycans in Trained Immunity: Educators of innate immune memory in homeostasis and disease"

Trained Immunity is defined as a biological process normally induced by exogenous or endogenous insults that triggers epigenetic and metabolic reprogramming events associated with long-term adaptation of innate immune cells. This trained phenotype confers enhanced responsiveness to subsequent triggers, resulting in an innate immune "memory" effect. Trained Immunity, in the past decade, has revealed important benefits for host defense and homeostasis, but can also induce potentially harmful outcomes associated with chronic inflammatory disorders or autoimmune diseases. Interestingly, evidence suggest that the "trainers" prompting trained immunity are frequently glycans structures. In fact, the exposure of different types of glycans at the surface of pathogens is a key driver of the training phenotype, leading to the reprogramming of innate immune cells through the recognition of those glycan-triggers by a variety of glycan-binding proteins (GBPs) expressed by the immune cells. β-glucan or mannose-enriched structures in Candida albicans are some of the examples that highlight the potential of glycans in trained immunity, both in homeostasis and in disease. In this review, we will discuss the relevance of glycans exposed by pathogens in establishing key immunological hubs with glycan-recognizing receptors expressed in immune cells, highlighting how this glycan-GBP network can impact trained immunity. Finally, we discuss the power of glycans and GBPs as potential targets in trained immunity, envisioning potential therapeutic applications.

LC-MS/MS of isomeric N-and O-glycopeptides on mesoporous graphitized carbon column

BACKGROUND

The study of glycopeptides is associated with challenges regarding the microheterogeneity of different isomeric glycans occupying the same glycosylation sites in glycoproteins. It is immensely valuable to perform both qualitative and quantitative site-specific glycosylation analysis of glycopeptide isomers due to their link to several diseases. Achieving isomeric separation of glycopeptides is particularly challenging due to the low abundance of glycopeptides as well as inefficient ionization. Although some methods have demonstrated the isomeric separation of glycopeptides, a more efficient nanoflow-based stationary phase is needed for the isomeric separation of both N- and O-glycopeptides.

RESULTS

In this study, the separation of N- and O-glycopeptide isomers at 75 °C was achieved with an in-house packed 1 cm long mesoporous graphitized carbon (MGC) column. Different gradient compositions of the optimized mobile phase for separating permethylated glycans on MGC column were tested, and we observed efficient separation of N- and O-glycopeptide isomers at a gradient elution time of 120 min. After achieving the isomeric separation of sialylated glycopeptides from model glycoproteins derived from bovine fetuin, the separation of isomeric glycopeptides derived from asialofetuin, α-1 glycoprotein and human blood serum were also demonstrated. Furthermore, the developed method for the separation of isomeric N- and O-glycopeptide on MGC column showed high reproducibility over three months. We observed an average retention time shift of 1 min and consistent resolution of separated peaks throughout three months.

SIGNIFICANCE AND NOVELTY

MGC column can serve as an efficient tool for obtaining the isomeric separation of N- and O-glycopeptide from complex biological samples in future studies. This will enable a more profound understanding of the roles played by isomeric N- and O-glycopeptide in important biological processes and their correlations to various disease progressions.

Orally Delivered Stimulus-Sensitive Nanomedicine to Harness Teduglutide Efficacy in Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) is a chronic inflammatory condition affecting the gastrointestinal tract (GIT). Glucagon-like peptide-2 (GLP-2) analogs possess high potential in the treatment of IBD by enhancing intestinal repair and attenuating inflammation. Due to the enzymatic degradation and poor intestinal absorption, GLP-2 analogs are administered parenterally, which leads to poor patient compliance. This work aims to develop IBD-targeted nanoparticles (NPs) for the oral delivery of the GLP-2 analog, Teduglutide (TED). Leveraging the overproduction of Reactive Oxygen Species (ROS) in the IBD environment, ROS-sensitive NPs are developed to target the intestinal epithelium, bypassing the mucus barrier. PEGylation of NPs facilitates mucus transposition, but subsequent PEG removal is crucial for cellular internalization. This de-PEGylation is possible by including a ROS-sensitive thioketal linker within the system. ROS-sensitive NPs are established, with the ability to fully de-PEGylate via ROS-mediated cleavage. Encapsulation of TED into NPs resulted in the absence of absorption in 3D in vitro models, potentially promoting a localized action, and avoiding adverse effects due to systemic absorption. Upon oral administration to colitis-induced mice, ROS-sensitive NPs are located in the colon, displaying healing capacity and reducing inflammation. Cleavable PEGylated NPs demonstrate effective potential in managing IBD symptoms and modulating the disease's progression.

Aberrant N-glycosylation is a therapeutic target in carriers of a common and highly pleiotropic mutation in the manganese transporter ZIP8

The treatment of defective glycosylation in clinical practice has been limited to patients with rare and severe phenotypes associated with congenital disorders of glycosylation (CDG). Carried by approximately 5% of the human population, the discovery of the highly pleiotropic, missense mutation in a manganese transporter ZIP8 has exposed under-appreciated roles for Mn homeostasis and aberrant Mn-dependent glycosyltransferases activity leading to defective N-glycosylation in complex human diseases. Here, we test the hypothesis that aberrant N-glycosylation contributes to disease pathogenesis of ZIP8 A391T-associated Crohn's disease. Analysis of N-glycan branching in intestinal biopsies demonstrates perturbation in active Crohn's disease and a genotype-dependent effect characterized by increased truncated N-glycans. A mouse model of ZIP8 391-Thr recapitulates the intestinal glycophenotype of patients carrying mutations in ZIP8. Borrowing from therapeutic strategies employed in the treatment of patients with CDGs, oral monosaccharide therapy with N-acetylglucosamine ameliorates the epithelial N-glycan defect, bile acid dyshomeostasis, intestinal permeability, and susceptibility to chemical-induced colitis in a mouse model of ZIP8 391-Thr. Together, these data support ZIP8 391-Thr alters N-glycosylation to contribute to disease pathogenesis, challenging the clinical paradigm that CDGs are limited to patients with rare diseases. Critically, the defect in glycosylation can be targeted with monosaccharide supplementation, providing an opportunity for genotype-driven, personalized medicine.

Revisiting the immunopathology of congenital disorders of glycosylation: an updated review

Glycosylation is a critical post-translational modification that plays a pivotal role in several biological processes, such as the immune response. Alterations in glycosylation can modulate the course of various pathologies, such as the case of congenital disorders of glycosylation (CDG), a group of more than 160 rare and complex genetic diseases. Although the link between glycosylation and immune dysfunction has already been recognized, the immune involvement in most CDG remains largely unexplored and poorly understood. In this study, we provide an update on the immune dysfunction and clinical manifestations of the 12 CDG with major immune involvement, organized into 6 categories of inborn errors of immunity according to the International Union of Immunological Societies (IUIS). The immune involvement in phosphomannomutase 2 (PMM2)-CDG - the most frequent CDG - was comprehensively reviewed, highlighting a higher prevalence of immune issues during infancy and childhood and in R141H-bearing genotypes. Finally, using PMM2-CDG as a model, we point to links between abnormal glycosylation patterns in host cells and possibly favored interactions with microorganisms that may explain the higher susceptibility to infection. Further characterizing immunopathology and unusual host-pathogen adhesion in CDG can not only improve immunological standards of care but also pave the way for innovative preventive measures and targeted glycan-based therapies that may improve quality of life for people living with CDG.

Melanoma tumour-derived glycans hijack dendritic cell subsets through C-type lectin receptor binding

Dendritic cell (DC) subsets play a crucial role in shaping anti-tumour immunity. Cancer escapes from the control immune system by hijacking DC functions. Yet, bases for such subversion are only partially understood. Tumour cells display aberrant glycan motifs on surface glycoproteins and glycolipids. Such carbohydrate patterns can be sensed by DCs through C-type lectin receptors (CLRs) that are critical to shape and orientate immune responses. We recently demonstrated that melanoma tumour cells harboured an aberrant 'glyco-code,' and that circulating and tumour-infiltrating DCs from melanoma patients displayed major perturbations in their CLR profiles. To decipher whether melanoma, through aberrant glycan patterns, may exploit CLR pathways to mislead DCs and evade immune control, we explored the impact of glycan motifs aberrantly found in melanoma (neoglycoproteins [NeoGP] functionalised with Gal, Man, GalNAc, s-Tn, fucose [Fuc] and GlcNAc residues) on features of human DC subsets (cDC2s, cDC1s and pDCs). We examined the ability of glycans to bind to purified DCs, and assessed their impact on DC basal properties and functional features using flow cytometry, confocal microscopy and multiplex secreted protein analysis. DC subsets differentially bound and internalised NeoGP depending on the nature of the glycan. Strikingly, Fuc directly remodelled the expression of activation markers and immune checkpoints, as well as the cytokine/chemokine secretion profile of DC subsets. NeoGP interfered with Toll like receptor (TLR)-signalling and pre-conditioned DCs to exhibit an altered response to subsequent TLR stimulation, dampening antitumor mediators while triggering pro-tumoral factors. We further demonstrated that DC subsets can bind NeoGP through CLRs, and identified GalNAc/MGL and s-Tn/ C-type lectin-like receptor 2 (CLEC2) as potential candidates. Moreover, DC dysfunction induced by tumour-associated carbohydrate molecules may be reversed by interfering with the glycan/CLR axis. These findings revealed the glycan/CLR axis as a promising checkpoint to exploit in order to reshape potent antitumor immunity while impeding immunosuppressive pathways triggered by aberrant tumour glycosylation patterns. This may rescue DCs from tumour hijacking and improve clinical success in cancer patients.

N-linked Fc glycosylation is not required for IgG-B-cell receptor function in a GC-derived B-cell line

IgG secreted by B cells carry asparagine N(297)-linked glycans in the fragment crystallizable (Fc) region. Changes in Fc glycosylation are related to health or disease and are functionally relevant, as IgG without Fc glycans cannot bind to Fcɣ receptors or complement factors. However, it is currently unknown whether ɣ-heavy chain (ɣHC) glycans also influence the function of membrane-bound IgG-B-cell receptors (BCR) and thus the outcome of the B-cell immune response. Here, we show in a germinal center (GC)-derived human B-cell line that ɣHC glycans do not affect membrane expression of IgG-BCRs. Furthermore, antigen binding or other BCR-facilitated mechanisms appear unaffected, including BCR downmodulation or BCR-mediated signaling. As expected, secreted IgG lacking Fc glycosylation is unable to carry out effector functions. Together, these observations indicate that IgG-Fc glycosylation serves as a mechanism to control the effector functions of antibodies, but does not regulate the activation of IgG-switched B cells, as its absence had no apparent impact on BCR function.

The role of glycosylation in clinical allergy and immunology

While glycans are among the most abundant macromolecules on the cell with widespread functions, their role in immunity has historically been challenging to study. This is in part due to difficulties assimilating glycan analysis into routine approaches used to interrogate immune cell function. Despite this, recent developments have illuminated fundamental roles for glycans in host immunity. The growing field of glycoimmunology continues to leverage new tools and approaches to uncover the function of glycans and glycan-binding proteins in immunity. Here we utilize clinical vignettes to examine key roles of glycosylation in allergy, inborn errors of immunity, and autoimmunity. We will discuss the diverse functions of glycans as epitopes, as modulators of antibody function, and as regulators of immune cell function. Finally, we will highlight immune modulatory therapies that harness the critical role of glycans in the immune system.

Maladaptive T-Cell Metabolic Fitness in Autoimmune Diseases

Immune surveillance and adaptive immune responses, involving continuously circulating and tissue-resident T-lymphocytes, provide host defense against infectious agents and possible malignant transformation while avoiding autoimmune tissue damage. Activation, migration, and deployment of T-cells to affected tissue sites are crucial for mounting an adaptive immune response. An effective adaptive immune defense depends on the ability of T-cells to dynamically reprogram their metabolic requirements in response to environmental cues. Inability of the T-cells to adapt to specific metabolic demands may skew cells to become either hyporesponsive (creating immunocompromised conditions) or hyperactive (causing autoimmune tissue destruction). Here, we review maladaptive T-cell metabolic fitness that can cause autoimmune diseases and discuss how T-cell metabolic programs can potentially be modulated to achieve therapeutic benefits.

Polyomavirus Wakes Up and Chooses Neurovirulence

JC polyomavirus (JCPyV) is a human-specific polyomavirus that establishes a silent lifelong infection in multiple peripheral organs, predominantly those of the urinary tract, of immunocompetent individuals. In immunocompromised settings, however, JCPyV can infiltrate the central nervous system (CNS), where it causes several encephalopathies of high morbidity and mortality. JCPyV-induced progressive multifocal leukoencephalopathy (PML), a devastating demyelinating brain disease, was an AIDS-defining illness before antiretroviral therapy that has "reemerged" as a complication of immunomodulating and chemotherapeutic agents. No effective anti-polyomavirus therapeutics are currently available. How depressed immune status sets the stage for JCPyV resurgence in the urinary tract, how the virus evades pre-existing antiviral antibodies to become viremic, and where/how it enters the CNS are incompletely understood. Addressing these questions requires a tractable animal model of JCPyV CNS infection. Although no animal model can replicate all aspects of any human disease, mouse polyomavirus (MuPyV) in mice and JCPyV in humans share key features of peripheral and CNS infection and antiviral immunity. In this review, we discuss the evidence suggesting how JCPyV migrates from the periphery to the CNS, innate and adaptive immune responses to polyomavirus infection, and how the MuPyV-mouse model provides insights into the pathogenesis of JCPyV CNS disease.

Omics and Multi-Omics in IBD: No Integration, No Breakthroughs

The recent advent of sophisticated technologies like sequencing and mass spectroscopy platforms combined with artificial intelligence-powered analytic tools has initiated a new era of "big data" research in various complex diseases of still-undetermined cause and mechanisms. The investigation of these diseases was, until recently, limited to traditional in vitro and in vivo biological experimentation, but a clear switch to in silico methodologies is now under way. This review tries to provide a comprehensive assessment of state-of-the-art knowledge on omes, omics and multi-omics in inflammatory bowel disease (IBD). The notion and importance of omes, omics and multi-omics in both health and complex diseases like IBD is introduced, followed by a discussion of the various omics believed to be relevant to IBD pathogenesis, and how multi-omics "big data" can generate new insights translatable into useful clinical tools in IBD such as biomarker identification, prediction of remission and relapse, response to therapy, and precision medicine. The pitfalls and limitations of current IBD multi-omics studies are critically analyzed, revealing that, regardless of the types of omes being analyzed, the majority of current reports are still based on simple associations of descriptive retrospective data from cross-sectional patient cohorts rather than more powerful longitudinally collected prospective datasets. Given this limitation, some suggestions are provided on how IBD multi-omics data may be optimized for greater clinical and therapeutic benefit. The review concludes by forecasting the upcoming incorporation of multi-omics analyses in the routine management of IBD.

Immune regulatory networks coordinated by glycans and glycan-binding proteins in autoimmunity and infection

The immune system is coordinated by an intricate network of stimulatory and inhibitory circuits that regulate host responses against endogenous and exogenous insults. Disruption of these safeguard and homeostatic mechanisms can lead to unpredictable inflammatory and autoimmune responses, whereas deficiency of immune stimulatory pathways may orchestrate immunosuppressive programs that contribute to perpetuate chronic infections, but also influence cancer development and progression. Glycans have emerged as essential components of homeostatic circuits, acting as fine-tuners of immunological responses and potential molecular targets for manipulation of immune tolerance and activation in a wide range of pathologic settings. Cell surface glycans, present in cells, tissues and the extracellular matrix, have been proposed to serve as "self-associated molecular patterns" that store structurally relevant biological data. The responsibility of deciphering this information relies on different families of glycan-binding proteins (including galectins, siglecs and C-type lectins) which, upon recognition of specific carbohydrate structures, can recalibrate the magnitude, nature and fate of immune responses. This process is tightly regulated by the diversity of glycan structures and the establishment of multivalent interactions on cell surface receptors and the extracellular matrix. Here we review the spatiotemporal regulation of selected glycan-modifying processes including mannosylation, complex N-glycan branching, core 2 O-glycan elongation, LacNAc extension, as well as terminal sialylation and fucosylation. Moreover, we illustrate examples that highlight the contribution of these processes to the control of immune responses and their integration with canonical tolerogenic pathways. Finally, we discuss the power of glycans and glycan-binding proteins as a source of immunomodulatory signals that could be leveraged for the treatment of autoimmune inflammation and chronic infection.

Understanding glycosylation: Regulation through the metabolic flux of precursor pathways

Glycosylation is how proteins and lipids are modified with complex carbohydrates known as glycans. The post-translational modification of proteins with glycans is not a template-driven process in the same way as genetic transcription or protein translation. Glycosylation is instead dynamically regulated by metabolic flux. This metabolic flux is determined by the concentrations and activities of the glycotransferase enzymes, which synthesise glycans, the metabolites that act as their precursors and transporter proteins. This review provides an overview of the metabolic pathways underlying glycan synthesis. Pathological dysregulation of glycosylation, particularly increased glycosylation occurring during inflammation, is also elucidated. The resulting inflammatory hyperglycosylation acts as a glycosignature of disease, and we report on the changes in the metabolic pathways which feed into glycan synthesis, revealing alterations to key enzymes. Finally, we examine studies in developing metabolic inhibitors targeting these critical enzymes. These results provide the tools for researchers investigating the role of glycan metabolism in inflammation and have helped to identify promising glycotherapeutic approaches to inflammation.

Muscle glycome in idiopathic inflammatory myopathies: Impact in IL-6 production and disease prognosis

Idiopathic inflammatory myopathies (IIM) are a group of chronic autoimmune diseases mainly affecting proximal muscles. Absence of meaningful prognostic factors in IIM has hindered new therapies development. Glycans are essential molecules that regulate immunological tolerance and consequently the onset of autoreactive immune response. We showed that muscle biopsies from patients with IIM revealed a deficiency in the glycosylation pathway resulting in loss of branched N-glycans. At diagnosis, this glycosignature predicted disease relapse and treatment refractoriness. Peripheral CD4⁺ T cells from active-disease patients shown a deficiency in branched N-glycans, linked to increased IL-6 production. Glycan supplementation, restoring homeostatic glycosylation profile, led to a decrease in IL-6 levels. This study highlights the biological and clinical importance of glycosylation in IIM immunopathogenesis, providing a potential mechanism for IL-6 production. This pinpoints muscle glycome as promising biomarker for personalized follow-up and a potential target for new therapies in a patients' subgroup with an ominous evolution.

Glycome dynamics in T and B cell development: basic immunological mechanisms and clinical applications

Glycans cover the surfaces of all mammalian cells through a process called glycosylation. Nearly all proteins and receptors that integrate the intricate series of co-stimulatory/inhibitory pathways of the immune system are glycosylated. Growing evidence indicates that the development of the immune system at the origins of T and B cell development is tightly regulated by glycosylation. In this opinion, we hypothesize that the glycome composition of developing T and B cells is developmentally regulated. We discuss how glycans play fundamental roles in lymphocyte development and how glycans early define T and B cell functionality in multiple aspects of adaptive immunity. These advances can provide opportunities for the discovery of novel disease factors and more effective candidate treatments for various conditions.

Altered profile of glycosylated proteins in serum samples obtained from patients with Hashimoto's thyroiditis following depletion of highly abundant proteins

Objectives

Hashimoto's thyroiditis (HT) is one of the most common autoimmune disorders; however, its underlying pathological mechanisms remain unclear. Although aberrant glycosylation has been implicated in the N-glycome of immunoglobulin G (IgG), changes in serum proteins have not been comprehensively characterized. This study aimed to investigate glycosylation profiles in serum samples depleted of highly abundant proteins from patients with HT and propose the potential functions of glycoproteins for further studies on the pathological mechanisms of HT.

Methods

A lectin microarray containing 70 lectins was used to detect and analyze glycosylation of serum proteins using serum samples (N=27 HT; N=26 healthy control [HC]) depleted of abundant proteins. Significant differences in glycosylation status between HT patients and the HC group were verified using lectin blot analysis. A lectin-based pull-down assay combined with mass spectrometry was used to investigate potential glycoproteins combined with differentially present lectins, and an enzyme-linked immunosorbent assay (ELISA) was used to identify the expression of targeted glycoproteins in 131 patients with papillary thyroid carcinoma (PTC), 131 patients with benign thyroid nodules (BTN) patients, 130 patients with HT, and 128 HCs.

Results

Compared with the HC group, the majority of the lectin binding signals in HT group were weakened, while the Vicia villosa agglutinin (VVA) binding signal was increased. The difference in VVA binding signals verified by lectin blotting was consistent with the results of the lectin microarray. A total of 113 potential VVA-binding glycoproteins were identified by mass spectrometry and classified by gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analyses. Using ELISA, we confirmed that lactoferrin (LTF) and mannan-binding lectin-associated serine protease 1 (MASP-1) levels were elevated in the serum of patients with HT and PTC.

Conclusion

Following depletion of abundant proteins, remaining serum proteins in HT patients exhibited lower glycosylation levels than those observed in HCs. An increased level of potential VVA-binding glycoproteins may play an important role in HT development. LTF and MASP-1 expression was significantly higher in the serum of HT and PTC patients, providing novel insight into HT and PTC.

Mannosylated glycans impair normal T-cell development by reprogramming commitment and repertoire diversity

T-cell development ensures the formation of diverse repertoires of T-cell receptors (TCRs) that recognize a variety of antigens. Glycosylation is a major posttranslational modification present in virtually all cells, including T-lymphocytes, that regulates activity/functions. Although these structures are known to be involved in TCR-selection in DP thymocytes, it is unclear how glycans regulate other thymic development processes and how they influence susceptibility to disease. Here, we discovered stage-specific glycome compositions during T-cell development in human and murine thymocytes, as well as dynamic alterations. After restricting the N-glycosylation profile of thymocytes to high-mannose structures, using specific glycoengineered mice (Rag1^CreMgat1^fl/fl), we showed remarkable defects in key developmental checkpoints, including ß-selection, regulatory T-cell generation and γδT-cell development, associated with increased susceptibility to colon and kidney inflammation and infection. We further demonstrated that a single N-glycan antenna (modeled in Rag1^CreMgat2^fl/fl mice) is the sine-qua-non condition to ensure normal development. In conclusion, we revealed that mannosylated thymocytes lead to a dysregulation in T-cell development that is associated with inflammation susceptibility.

RUNX2 promotes gastric cancer progression through the transcriptional activation of MGAT5 and MMP13

Introduction

RUNX2 is overexpressed in gastric cancer but the mechanism(s) through which it promotes tumor progression remain undefined. Here, we investigated the role of RUNX2 on gastric cancer pathogenesis at the molecular level.

Methods

The qRT-PCR and western bolt were utilized to examine the mRNA and protein levels. CCK-8, Transwell and wound healing assays were used to measure cell proliferation, invasion and migration. CHIP-PCR gel electrophoresis was used to verify RUNX2 as a transcription factor for MMP13 and MGAT5. The in vivo assay was utilized to assess tumor growth. In vivo assay was used to evaluate tumor growth, aberrant expression of RUNX2 and lung metastasis of gastric cancer.

Results

RUNX2 is overexpressed in MKN-45 and AGS cells. Genetic RUNX2 silencing reduced the proliferation, invasion and migration of MKN-45 and AGS cells. Analysis of the gastric cancer samples from the database revealed a significant positive correlation between MGAT5, MMP13, and RUNX2 expression. JASPAR analysis revealed that there was a potential binding site of RUNX2 in the promoter regions of MGAT5 and MMP13, and the experimental results confirmed that RUNX2 could regulate the expression of MGAT5 and MMP13 respectively. In vivo assays confirmed the aberrant expression of RUNX2 in mouse models of gastric cancer and reduced growth and lung metastasis in RUNX2 silenced xenograft tumors assessed.

Conclusion

Collectively, these data reveal that RUNX2 enhances MGAT5 and MMP13 expression in gastric cancer cells and represents a biomarker and potential therapeutic target for gastric cancer therapy.

Advances in protein glycosylation and its role in tissue repair and regeneration

After tissue damage, a series of molecular and cellular events are initiated to promote tissue repair and regeneration to restore its original structure and function. These events include inter-cell communication, cell proliferation, cell migration, extracellular matrix differentiation, and other critical biological processes. Glycosylation is the crucial conservative and universal post-translational modification in all eukaryotic cells [1], with influential roles in intercellular recognition, regulation, signaling, immune response, cellular transformation, and disease development. Studies have shown that abnormally glycosylation of proteins is a well-recognized feature of cancer cells, and specific glycan structures are considered markers of tumor development. There are many studies on gene expression and regulation during tissue repair and regeneration. Still, there needs to be more knowledge of complex carbohydrates' effects on tissue repair and regeneration, such as glycosylation. Here, we present a review of studies investigating protein glycosylation in the tissue repair and regeneration process.

The Hexosamine Biosynthesis Pathway: Regulation and Function

The hexosamine biosynthesis pathway (HBP) produces uridine diphosphate-N-acetyl glucosamine, UDP-GlcNAc, which is a key metabolite that is used for N- or O-linked glycosylation, a co- or post-translational modification, respectively, that modulates protein activity and expression. The production of hexosamines can occur via de novo or salvage mechanisms that are catalyzed by metabolic enzymes. Nutrients including glutamine, glucose, acetyl-CoA, and UTP are utilized by the HBP. Together with availability of these nutrients, signaling molecules that respond to environmental signals, such as mTOR, AMPK, and stress-regulated transcription factors, modulate the HBP. This review discusses the regulation of GFAT, the key enzyme of the de novo HBP, as well as other metabolic enzymes that catalyze the reactions to produce UDP-GlcNAc. We also examine the contribution of the salvage mechanisms in the HBP and how dietary supplementation of the salvage metabolites glucosamine and N-acetylglucosamine could reprogram metabolism and have therapeutic potential. We elaborate on how UDP-GlcNAc is utilized for N-glycosylation of membrane and secretory proteins and how the HBP is reprogrammed during nutrient fluctuations to maintain proteostasis. We also consider how O-GlcNAcylation is coupled to nutrient availability and how this modification modulates cell signaling. We summarize how deregulation of protein N-glycosylation and O-GlcNAcylation can lead to diseases including cancer, diabetes, immunodeficiencies, and congenital disorders of glycosylation. We review the current pharmacological strategies to inhibit GFAT and other enzymes involved in the HBP or glycosylation and how engineered prodrugs could have better therapeutic efficacy for the treatment of diseases related to HBP deregulation.

Host-derived mannose glycans trigger a pathogenic γδ T cell/IL-17a axis in autoimmunity

Autoimmune diseases are life-threatening disorders that cause increasing disability over time. Systemic lupus erythematosus (SLE) and other autoimmune diseases arise when immune stimuli override mechanisms of self-tolerance. Accumulating evidence has demonstrated that protein glycosylation is substantially altered in autoimmune disease development, but the mechanisms by which glycans trigger these autoreactive immune responses are still largely unclear. In this study, we found that presence of microbial-associated mannose structures at the surface of the kidney triggers the recognition of DC-SIGN-expressing γδ T cells, inducing a pathogenic interleukin-17a (IL-17a)-mediated autoimmune response. Mice lacking Mgat5, which have a higher abundance of mannose structures in the kidney, displayed increased γδ T cell infiltration into the kidney that was associated with spontaneous development of lupus in older mice. N-acetylglucosamine supplementation, which promoted biosynthesis of tolerogenic branched N-glycans in the kidney, was found to inhibit γδ T cell infiltration and control disease development. Together, this work reveals a mannose-γδ T cell-IL-17a axis in SLE immunopathogenesis and highlights glycometabolic reprogramming as a therapeutic strategy for autoimmune disease treatment.

Aberrant N-glycosylation in cancer: MGAT5 and β1,6-GlcNAc branched N-glycans as critical regulators of tumor development and progression

BACKGROUND

Changes in protein glycosylation are widely observed in tumor cells. N-glycan branching through adding β1,6-linked N-acetylglucosamine (β1,6-GlcNAc) to an α1,6-linked mannose, which is catalyzed by the N-acetylglucosaminyltransferase V (MGAT5 or GnT-V), is one of the most frequently observed tumor-associated glycan structure formed. Increased levels of this branching structure play a pro-tumoral role in various ways, for example, through the stabilization of growth factor receptors, the destabilization of intercellular adhesion, or the acquisition of a migratory phenotype.

CONCLUSION

In this review, we provide an updated and comprehensive summary of the physiological and pathophysiological roles of MGAT5 and β1,6-GlcNAc branched N-glycans, including their regulatory mechanisms. Specific emphasis is given to the role of MGAT5 and β1,6-GlcNAc branched N-glycans in cellular mechanisms that contribute to the development and progression of solid tumors. We also provide insight into possible future clinical implications, such as the use of MGAT5 as a prognostic biomarker.

The Blessed Union of Glycobiology and Immunology: A Marriage That Worked

In this article, we discuss the main aspects regarding the recognition of cell surface glycoconjugates and the immunomodulation of responses against the progression of certain pathologies, such as cancer and infectious diseases. In the first part, we talk about different aspects of glycoconjugates and delve deeper into the importance of N-glycans in cancer immunotherapy. Then, we describe two important lectin families that have been very well studied in the last 20 years. Examples include the sialic acid-binding immunoglobulin (Ig)-like lectins (siglecs), and galectins. Finally, we discuss a topic that needs to be better addressed in the field of glycoimmunology: the impact of oncofetal antigens on the cells of the immune system. New findings in this area are of great importance for advancement, especially in the field of oncology, since it is already known that cellular interactions mediated by carbohydrate-carbohydrate and/or carbohydrate proteins are able to modulate the progression of different types of cancer in events that compromise the functionality of the immune responses.

Decoding Strategies to Evade Immunoregulators Galectin-1, -3, and -9 and Their Ligands as Novel Therapeutics in Cancer Immunotherapy

Galectins are a family of ß-galactoside-binding proteins that play a variety of roles in normal physiology. In cancer, their expression levels are typically elevated and often associated with poor prognosis. They are known to fuel a variety of cancer progression pathways through their glycan-binding interactions with cancer, stromal, and immune cell surfaces. Of the 15 galectins in mammals, galectin (Gal)-1, -3, and -9 are particularly notable for their critical roles in tumor immune escape. While these galectins play integral roles in promoting cancer progression, they are also instrumental in regulating the survival, differentiation, and function of anti-tumor T cells that compromise anti-tumor immunity and weaken novel immunotherapies. To this end, there has been a surge in the development of new strategies to inhibit their pro-malignancy characteristics, particularly in reversing tumor immunosuppression through galectin-glycan ligand-targeting methods. This review examines some new approaches to evading Gal-1, -3, and -9-ligand interactions to interfere with their tumor-promoting and immunoregulating activities. Whether using neutralizing antibodies, synthetic peptides, glyco-metabolic modifiers, competitive inhibitors, vaccines, gene editing, exo-glycan modification, or chimeric antigen receptor (CAR)-T cells, these methods offer new hope of synergizing their inhibitory effects with current immunotherapeutic methods and yielding highly effective, durable responses.

A roadmap for translational cancer glycoimmunology at single cell resolution

Cancer cells can evade immune responses by exploiting inhibitory immune checkpoints. Immune checkpoint inhibitor (ICI) therapies based on anti-CTLA-4 and anti-PD-1/PD-L1 antibodies have been extensively explored over the recent years to unleash otherwise compromised anti-cancer immune responses. However, it is also well established that immune suppression is a multifactorial process involving an intricate crosstalk between cancer cells and the immune systems. The cancer glycome is emerging as a relevant source of immune checkpoints governing immunosuppressive behaviour in immune cells, paving an avenue for novel immunotherapeutic options. This review addresses the current state-of-the-art concerning the role played by glycans controlling innate and adaptive immune responses, while shedding light on available experimental models for glycoimmunology. We also emphasize the tremendous progress observed in the development of humanized models for immunology, the paramount contribution of advances in high-throughput single-cell analysis in this context, and the importance of including predictive machine learning algorithms in translational research. This may constitute an important roadmap for glycoimmunology, supporting careful adoption of models foreseeing clinical translation of fundamental glycobiology knowledge towards next generation immunotherapies.

The Pathogenicity and Synergistic Action of Th1 and Th17 Cells in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBDs), including ulcerative colitis and Crohn's disease, are characterized by chronic idiopathic inflammation of gastrointestinal tract. Although the pathogenesis of IBD remains unknown, intestinal immune dysfunction has been considered as the core pathogenesis. In the intestinal immune system, T helper 1 (Th1) and Th17 cells are indispensable for intestine homeostasis via preventing pathogenic bacteria invasion, regulating metabolism and functions of intestinal epithelial cells (IECs), and promoting IEC self-renewal. However, during the development of IBD, Th1 and Th17 cells acquire the pathogenicity and change from the maintainer of intestinal homeostasis to the destroyer of intestinal mucosa. Because of coexpressing interferon-γ and interleukin-17A, Th17 cells with pathogenicity are named as pathogenic Th17 cells. In disease states, Th1 cells impair IEC programs by inducing IEC apoptosis, recruiting immune cells, promoting adhesion molecules expression of IECs, and differentiating to epithelial cell adhesion molecule-specific interferon γ-positive Th1 cells. Pathogenic Th17 cells induce IEC injury by triggering IBD susceptibility genes expression of IECs and specifically killing IECs. In addition, Th1 and pathogenic Th17 cells could cooperate to induce colitis. The evidences from IBD patients and animal models demonstrate that synergistic action of Th1 and pathogenic Th17 cells occurs in the diseases development and aggravates the mucosal inflammation. In this review, we focused on Th1 and Th17 cell programs in homeostasis and intestine inflammation and specifically discussed the impact of Th1 and Th17 cell pathogenicity and their synergistic action on the onset and the development of IBD. We hoped to provide some clues for treating IBD.

CD4+ T cell metabolism, gut microbiota, and autoimmune diseases: Implication in precision medicine of autoimmune diseases

CD4⁺ T cells are critical to the development of autoimmune disorders. Glucose, fatty acids, and glutamine metabolisms are the primary metabolic pathways in immune cells, including CD4⁺ T cells. The distinct metabolic programs in CD4⁺ T cell subsets are recognized to reflect the bioenergetic requirements, which are compatible with their functional demands. Gut microbiota affects T cell responses by providing a series of antigens and metabolites. Accumulating data indicate that CD4⁺ T cell metabolic pathways underlie aberrant T cell functions, thereby regulating the pathogenesis of autoimmune disorders, including inflammatory bowel diseases, systemic lupus erythematosus, and rheumatoid arthritis. Here, we summarize the current progress of CD4⁺ T cell metabolic programs, gut microbiota regulation of T cell metabolism, and T cell metabolic adaptions to autoimmune disorders to shed light on potential metabolic therapeutics for autoimmune diseases.

Bringing to Light the Risk of Colorectal Cancer in Inflammatory Bowel Disease: Mucosal Glycosylation as a Key Player

Colitis-associated cancer is a major complication of inflammatory bowel disease remaining an important clinical challenge in terms of diagnosis, screening, and prognosis. Inflammation is a driving factor both in inflammatory bowel disease and cancer, but the mechanism underlying the transition from colon inflammation to cancer remains to be defined. Dysregulation of mucosal glycosylation has been described as a key regulatory mechanism associated both with colon inflammation and colorectal cancer development. In this review, we discuss the major molecular mechanisms of colitis-associated cancer pathogenesis, highlighting the role of glycans expressed at gut epithelial cells, at lamina propria T cells, and in serum proteins in the regulation of intestinal inflammation and its progression to colon cancer, further discussing its potential clinical and therapeutic applications.

Multiomics to elucidate inflammatory bowel disease risk factors and pathways

Inflammatory bowel disease (IBD) is an immune-mediated disease of the intestinal tract, with complex pathophysiology involving genetic, environmental, microbiome, immunological and potentially other factors. Epidemiological data have provided important insights into risk factors associated with IBD, but are limited by confounding, biases and data quality, especially when pertaining to risk factors in early life. Multiomics platforms provide granular high-throughput data on numerous variables simultaneously and can be leveraged to characterize molecular pathways and risk factors for chronic diseases, such as IBD. Herein, we describe omics platforms that can advance our understanding of IBD risk factors and pathways, and available omics data on IBD and other relevant diseases. We highlight knowledge gaps and emphasize the importance of birth, at-risk and pre-diagnostic cohorts, and neonatal blood spots in omics analyses in IBD. Finally, we discuss network analysis, a powerful bioinformatics tool to assemble high-throughput data and derive clinical relevance.

Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology

Complex asparagine-linked glycosylation plays key roles in cellular functions, including cellular signaling, protein stability, and immune response. Previously, we characterized the appearance of a complex asparagine-linked glycosylated form of lysosome-associated membrane protein 1 (LAMP1) in the cerebellum of Npc1^-/- mice. This LAMP1 form was found on activated microglia, and its appearance correlated both spatially and temporally with cerebellar Purkinje neuron loss. To test the importance of complex asparagine-linked glycosylation in NPC1 pathology, we generated NPC1 knock-out mice deficient in MGAT5, a key Golgi-resident glycosyl transferase involved in complex asparagine-linked glycosylation. Our results show that Mgat5^-/-:Npc1^-/- mice were smaller than Mgat5^+/+:Npc1^-/- mice, and exhibited earlier NPC1 disease onset and reduced lifespan. Western blot and lectin binding analyses of cerebellar extracts confirmed the reduction in complex asparagine-linked glycosylation, and the absence of the hyper-glycosylated LAMP1 previously observed. Western blot analysis of cerebellar extracts demonstrated reduced calbindin staining in Mgat5^-/-:Npc1^-/- mice compared to Mgat5^+/+:Npc1^-/- mutant mice, and immunofluorescent staining of cerebellar sections indicated decreased levels of Purkinje neurons and increased astrogliosis in Mgat5^-/-:Npc1^-/- mice. Our results suggest that reduced asparagine-linked glycosylation increases NPC1 disease severity in mice, and leads to the hypothesis that mutations in genes involved in asparagine-linked glycosylation may contribute to disease severity progression in individuals with NPC1. To examine this with respect to MGAT5, we analyzed 111 NPC1 patients for two MGAT5 SNPs associated with multiple sclerosis; however, we did not identify an association with NPC1 phenotypic severity.

Glucosylceramide in T cells regulates the pathology of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease in the colon characterized by excessive activation of T cells. Glycosphingolipids (GSLs) are composed of lipid rafts in cellular membranes, and their content is linked to immune cell function. In the present study, we investigated the involvement of GSLs in IBD. Microarray data showed that in IBD patients, the expression of only UDP-glucose ceramide glucosyltransferase (UGCG) decreased among the GSLs synthases. Ad libitum access to dextran sulfate sodium (DSS) resulted in decreased UGCG and glucosylceramide (GlcCer) content in mesenteric lymph nodes and T cells from the spleen. Furthermore, the knockdown of Ugcg in T cells exacerbated the pathogenesis of colitis, which was accompanied by a decrease in Treg levels. Treatment with GlcCer nanoparticles prevented DSS-induced colitis. These results suggested that GlcCer in T cells is involved in the pathogenesis of IBD. Furthermore, GlcCer nanoparticles are a potential efficacious therapeutic target for IBD patients.

Glycans as a key factor in self and non-self discrimination: Impact on the breach of immune tolerance

Glycans are carbohydrates that are made by all organisms and covalently conjugated to other biomolecules. Glycans cover the surface of both human cells and pathogens and are fundamental to defining the identity of a cell or an organism, thereby contributing to discriminating self from non-self. As such, glycans are a class of "Self-Associated Molecular Patterns" that can fine-tune host inflammatory processes. In fact, glycans can be sensed and recognized by a variety of glycan-binding proteins (GBP) expressed by immune cells, such as galectins, siglecs and C-type lectins, which recognize changes in the cellular glycosylation, instructing both pro-inflammatory or anti-inflammatory responses. In this review, we introduce glycans as cell-identification structures, discussing how glycans modulate host-pathogen interactions and how they can fine-tune inflammatory processes associated with infection, inflammation and autoimmunity. Finally, from the clinical standpoint, we discuss how glycoscience research can benefit life sciences and clinical medicine by providing a source of valuable biomarkers and therapeutic targets for immunity.

N-glycosylation, a leading role in viral infection and immunity development

N-linked protein glycosylation is an essential co-and posttranslational protein modification that occurs in all three domains of life; the assembly of N-glycans follows a complex sequence of events spanning the (Endoplasmic Reticulum) ER and the Golgi apparatus. It has a significant impact on both physicochemical properties and biological functions. It plays a significant role in protein folding and quality control, glycoprotein interaction, signal transduction, viral attachment, and immune response to infection. Glycoengineering of protein employed for improving protein properties and plays a vital role in the production of recombinant glycoproteins and struggles to humanize recombinant therapeutic proteins. It considers an alternative platform for biopharmaceuticals production. Many immune proteins and antibodies are glycosylated. Pathogen’s glycoproteins play vital roles during the infection cycle and their expression of specific oligosaccharides via the N-glycosylation pathway to evade detection by the host immune system. This review focuses on the aspects of N-glycosylation processing, glycoengineering approaches, their role in viral attachment, and immune responses to infection.

Emerging role of protein modification in inflammatory bowel disease

The onset of inflammatory bowel disease (IBD) involves many factors, including environmental parameters, microorganisms, and the immune system. Although research on IBD continues to expand, the specific pathogenesis mechanism is still unclear. Protein modification refers to chemical modification after protein biosynthesis, also known as post-translational modification (PTM), which causes changes in the properties and functions of proteins. Since proteins can be modified in different ways, such as acetylation, methylation, and phosphorylation, the functions of proteins in different modified states will also be different. Transitions between different states of protein or changes in modification sites can regulate protein properties and functions. Such modifications like neddylation, sumoylation, glycosylation, and acetylation can activate or inhibit various signaling pathways (e.g., nuclear factor-‍κB (NF-‍κB), extracellular signal-regulated kinase (ERK), and protein kinase B (AKT)) by changing the intestinal flora, regulating immune cells, modulating the release of cytokines such as interleukin-1β (IL-‍‍1β), tumor necrosis factor-α (TNF‍-‍α), and interferon-‍γ (IFN-‍γ), and ultimately leading to the maintenance of the stability of the intestinal epithelial barrier. In this review, we focus on the current understanding of PTM and describe its regulatory role in the pathogenesis of IBD.

Finding the sweet spot: glycosylation mediated regulation of intestinal inflammation

Glycans are essential cellular components that facilitate a range of critical functions important for tissue development and mucosal homeostasis. Furthermore, specific alterations in glycosylation represent important diagnostic hallmarks of cancer that contribute to tumor cell dissociation, invasion, and metastasis. However, much less is known about how glycosylation contributes to the pathobiology of inflammatory mucosal diseases. Here we will review how epithelial and immune cell glycosylation regulates gut homeostasis and how inflammation-driven changes in glycosylation contribute to intestinal pathobiology.

Role of heparinase in the gastrointestinal dysfunction of sepsis (Review)

Heparinase (HPA) is a β-D glucuronidase that belongs to the endoglycosidase enzyme family, and plays an important role in numerous pathological and physiological processes, including inflammation, angiogenesis and tumor metastasis. When the expression of HPA is abnormally high, the side chain of heparin sulfate proteoglycans degrades, destroying the cell barrier and leading to the occurrence and development of inflammation, with systemic inflammation occurring in severe cases. Sepsis is a major cause of mortality in critically ill patients. In sepsis, the gastrointestinal tract is the first and most frequently involved target organ, which often leads to gastrointestinal dysfunction. HPA overexpression has been determined to accelerate sepsis progression and gastrointestinal dysfunction; thus, it was hypothesized that HPA may play an important role and may serve as an index for the diagnosis of gastrointestinal dysfunction in sepsis. HPA inhibitors may therefore become applicable as targeted drugs for the treatment of gastrointestinal dysfunction in patients with sepsis. The present review mainly discussed the role of HPA in gastrointestinal dysfunction of sepsis.

Targeting Immune Cell Metabolism in the Treatment of Inflammatory Bowel Disease

The cells of the immune system are highly dynamic, constantly sensing and adapting to changes in their surroundings. Complex metabolic pathways govern leukocytes' ability to fine-tune their responses to external threats. Mammalian target of rapamycin complex 1 and hypoxia inducible factor are important hubs of these pathways and play a critical role coordinating cell activation and proliferation and cytokine production. For this reason, these molecules are attractive therapeutic targets in inflammatory disease. Insight into perturbations in immune cell metabolic pathways and their impact on inflammatory bowel disease (IBD) progression are starting to emerge. However, it remains to be determined whether the aberrations in immune metabolism that occur in gut resident immune cells contribute to disease pathogenesis or are reflected in the peripheral blood of patients with IBD. In this review, we explore what is known about the metabolic profile of T cells, monocytes, macrophages, dendritic cells, and natural killer cells in IBD and discuss the potential of manipulating immune cell metabolism as a novel approach to treating IBD.

SARS-CoV-2 Infection Drives a Glycan Switch of Peripheral T Cells at Diagnosis

COVID-19 is a highly selective disease in which SARS-CoV-2 infection can result in different clinical manifestations ranging from asymptomatic/mild to severe disease that requires hospitalization. In this study, we demonstrated that SARS-CoV-2 infection results in a glycosylation reprogramming of circulating lymphocytes at diagnosis. We identified a specific glycosignature of T cells, defined upon SARS-CoV-2 infection and apparently triggered by a serological factor. This specific glycan switch of T cells is detected at diagnosis being more pronounced in asymptomatic patients. We further demonstrated that asymptomatic patients display an increased expression of a viral-sensing receptor through the upregulation of DC-SIGN in monocytes. We showed that higher levels of DC-SIGN in monocytes at diagnosis correlates with better COVID-19 prognosis. This new evidence pave the way to the identification of a novel glycan-based response in T cells that may confer protection against SARS-CoV-2 infection in asymptomatic patients, highlighting a novel prognostic biomarker and potential therapeutic target.

Native Mass Spectrometry Meets Glycomics: Resolving Structural Detail and Occupancy of Glycans on Intact Glycoproteins

Glycoproteins are inherently heterogeneous and therefore resolving structures in their entirety remains a major challenge in structural biology. Native mass spectrometry has transformed our ability to study glycoproteins, and despite advances in high-resolution instrumentation, there are comparatively a few studies demonstrating its potential with data largely limited to an overall measure of monosaccharide composition for all glycans across glycosylation sites for a given protein. Clearly, these readouts lack glycan topology information, namely, monosaccharide linkage and glycan branching. To address this deficiency, we developed a new approach that joins native mass spectrometry with glycan exoglycosidase sequencing, the combination of which provides remarkable glycoprotein structural details. We show how N-glycan branching, terminal fucosylation, LacNAc extensions, and N- and O-glycan occupancy (i.e., total number of glycans) can be directly characterized on intact glycoproteins with minimal sample preparation. Taken together, native exoglycosidase sequencing mass spectrometry (NES-MS) notably improves our ability to characterize protein glycosylation, addressing a significant need in structural biology that will enable new routes to understand glycoprotein function.

Neu3 neuraminidase induction triggers intestinal inflammation and colitis in a model of recurrent human food-poisoning

Intestinal inflammation is the underlying basis of colitis and the inflammatory bowel diseases. These syndromes originate from genetic and environmental factors that remain to be fully identified. Infections are possible disease triggers, including recurrent human food-poisoning by the common foodborne pathogen Salmonella enterica Typhimurium (ST), which in laboratory mice causes progressive intestinal inflammation leading to an enduring colitis. In this colitis model, disease onset has been linked to Toll-like receptor-4-dependent induction of intestinal neuraminidase activity, leading to the desialylation, reduced half-life, and acquired deficiency of anti-inflammatory intestinal alkaline phosphatase (IAP). Neuraminidase (Neu) inhibition protected against disease onset; however, the source and identity of the Neu enzyme(s) responsible remained unknown. Herein, we report that the mammalian Neu3 neuraminidase is responsible for intestinal IAP desialylation and deficiency. Absence of Neu3 thereby prevented the accumulation of lipopolysaccharide-phosphate and inflammatory cytokine expression in providing protection against the development of severe colitis.

Association of a Marker of N-Acetylglucosamine With Progressive Multiple Sclerosis and Neurodegeneration

Question

Is the serum concentration of N-acetylglucosamine (GlcNAc) altered in patients with multiple sclerosis?

Findings

This cross-sectional study found that patients with a progressive multiple sclerosis subtype and more severe disease have reduced serum levels of a marker of GlcNAc. In addition, GlcNAc is a rate-limiting substrate for N-glycan branching, which has been shown to regulate immunoactivity and myelination.

Meaning

This study suggests that GlcNAc and N-glycan branching are associated with multiple sclerosis in general and progressive multiple sclerosis in particular.

Importance

N-glycan branching modulates cell surface receptor availability, and its deficiency in mice promotes inflammatory demyelination, reduced myelination, and neurodegeneration. N-acetylglucosamine (GlcNAc) is a rate-limiting substrate for N-glycan branching, but, to our knowledge, endogenous serum levels in patients with multiple sclerosis (MS) are unknown.

Objective

To investigate a marker of endogenous serum GlcNAc levels in patients with MS.

Design, Setting, and Participants

A cross-sectional discovery study and cross-sectional confirmatory study were conducted at 2 academic MS centers in the US and Germany. The discovery study recruited 54 patients with MS from an outpatient clinic as well as 66 healthy controls between April 20, 2010, and June 21, 2013. The confirmatory study recruited 180 patients with MS from screening visits at an academic MS study center between April 9, 2007, and February 29, 2016. Serum samples were analyzed from December 2, 2013, to March 2, 2015. Statistical analysis was performed from February 23, 2020, to March 18, 2021.

Main Outcomes and Measures

Serum levels of GlcNAc plus its stereoisomers, termed N-acetylhexosamine (HexNAc), were assessed using targeted tandem mass spectroscopy. Secondary outcomes (confirmatory study) comprised imaging and clinical disease markers.

Results

The discovery cohort included 66 healthy controls (38 women; mean [SD] age, 42 [20] years), 33 patients with relapsing-remitting MS (RRMS; 25 women; mean [SD] age, 50 [11] years), and 21 patients with progressive MS (PMS; 14 women; mean [SD] age, 55 [7] years). The confirmatory cohort included 125 patients with RRMS (83 women; mean [SD] age, 40 [9] years) and 55 patients with PMS (22 women; mean [SD] age, 49 [80] years). In the discovery cohort, the mean (SD) serum level of GlcNAc plus its stereoisomers (HexNAc) was 710 (174) nM in healthy controls and marginally reduced in patients with RRMS (mean [SD] level, 682 [173] nM; P = .04), whereas patients with PMS displayed markedly reduced levels compared with healthy controls (mean [SD] level, 548 [101] nM; P = 9.55 × 10⁻⁹) and patients with RRMS (P = 1.83 × 10⁻⁴). The difference between patients with RRMS (mean [SD] level, 709 [193] nM) and those with PMS (mean [SD] level, 405 [161] nM; P = 7.6 × 10⁻¹⁸) was confirmed in the independent confirmatory cohort. Lower HexNAc serum levels correlated with worse expanded disability status scale scores (ρ = –0.485; P = 4.73 × 10⁻¹²), lower thalamic volume (t = 1.7; P = .04), and thinner retinal nerve fiber layer (B = 0.012 [SE = 7.5 × 10⁻¹¹]; P = .008). Low baseline serum HexNAc levels correlated with a greater percentage of brain volume loss at 18 months (t = 1.8; P = .04).

Conclusions and Relevance

This study suggests that deficiency of GlcNAc plus its stereoisomers (HexNAc) may be a biomarker for PMS. Previous preclinical, human genetic, and ex vivo human mechanistic studies revealed that N-glycan branching and/or GlcNAc may reduce proinflammatory responses, promote myelin repair, and decrease neurodegeneration. Combined, the data suggest that GlcNAc deficiency may be associated with progressive disease and neurodegeneration in patients with MS.

Analysis of site-specific glycan profiles of serum proteins in patients with multiple sclerosis or neuromyelitis optica spectrum disorder - a pilot study

Glycosylation is important for biological functions of proteins and greatly affected by diseases. Exploring the glycosylation profile of the protein-specific glycosylation and/or the site-specific glycosylation may help understand disease etiology, differentiate diseases, and ultimately develop therapeutics. Patients with multiple sclerosis (MS) and patients with neuromyelitis optica spectrum disorder (NMOSD) are sometimes difficult to differentiate due to the similarity in their clinical symptoms. The disease-related glycosylation profiles of MS and NMOSD have not yet been well studied. Here, we analyzed site-specific glycan profiles of serum proteins of these patients by using a recently developed mass spectrometry technique. A total of 286 glycopeptides from 49 serum glycoproteins were quantified and compared between healthy controls (n = 6), remitting MS (n = 45) and remitting NMOSD (n = 23) patients. Significant differences in the levels of site-specific N-glycans on inflammation-associated components [IgM, IgG1, IgG2, complement components 8b (CO8B), attractin], central nerve system-damage-related serum proteins [apolipoprotein D (APOD), alpha-1-antitrypsin, plasma kallikrein and ADAMTS-like protein 3] were observed among three study groups. We furthered demonstrated that site-specific N-glycans on APOD on site 98, CO8B on sites 243 and 553 are potential markers to differentiate MS from NMOSD with an area under receiver operating curve value greater than 0.75. All these observations indicate that remitting MS or NMOSD patients possess a unique disease-associated glyco-signature in their serum proteins. We conclude that monitoring one's serum protein glycan profile using this high-throughput analysis may provide an additional diagnostic criterion for differentiating diseases, monitoring disease status and estimating response-to-treatment effect.

Control of intestinal inflammation by glycosylation-dependent lectin-driven immunoregulatory circuits

Diverse immunoregulatory circuits operate to preserve intestinal homeostasis and prevent inflammation. Galectin-1 (Gal1), a β-galactoside-binding protein, promotes homeostasis by reprogramming innate and adaptive immunity. Here, we identify a glycosylation-dependent "on-off" circuit driven by Gal1 and its glycosylated ligands that controls intestinal immunopathology by targeting activated CD8⁺ T cells and shaping the cytokine profile. In patients with inflammatory bowel disease (IBD), augmented Gal1 was associated with dysregulated expression of core 2 β6-N-acetylglucosaminyltransferase 1 (C2GNT1) and α(2,6)-sialyltransferase 1 (ST6GAL1), glycosyltransferases responsible for creating or masking Gal1 ligands. Mice lacking Gal1 exhibited exacerbated colitis and augmented mucosal CD8⁺ T cell activation in response to 2,4,6-trinitrobenzenesulfonic acid; this phenotype was partially ameliorated by treatment with recombinant Gal1. While C2gnt1^-/- mice exhibited aggravated colitis, St6gal1^-/- mice showed attenuated inflammation. These effects were associated with intrinsic T cell glycosylation. Thus, Gal1 and its glycosylated ligands act to preserve intestinal homeostasis by recalibrating T cell immunity.

Genetic Variants of the MGAT5 Gene Are Functionally Implicated in the Modulation of T Cells Glycosylation and Plasma IgG Glycome Composition in Ulcerative Colitis

The impact of genetic variants (single nucleotide polymorphisms [SNPs]) in the clinical heterogeneity of ulcerative colitis (UC) remains unclear. We showed that patients with UC exhibit a deficiency in MGAT5 glycogene transcription in intestinal T cells associated with a hyperimmune response. Herein, we evaluated whether MGAT5 SNPs might functionally impact on T cells glycosylation and plasma IgG glycome in patients with UC, as well as in UC clinical outcomes.

Protein mannosylation as a diagnostic and prognostic biomarker of lupus nephritis: an unusual glycan-neoepitope in Systemic Lupus Erythematosus

OBJECTIVES

Changes in protein glycosylation are a hallmark of immune-mediated diseases. Glycans are master regulators of the inflammatory response being important molecules for the discrimination between "self"/"non-self". We here explored whether lupus nephritis (LN) exhibit an altered cellular glycosylation aiming to identify a unique glycosignature that characterizes LN pathogenesis.

METHODS

A comprehensive tissue glycomics characterization was performed in a cohort of human biopsy-proven LN clinical samples from SLE patients. A combination of advanced tissue mass spectrometry imaging (MSI); in situ glyco-characterization and ex vivo glycophenotyping of human kidney biopsies were performed to structurally map the N-glycans repertoire in LN samples.

RESULTS

LN revealed a unique glycan signature characterized by an increased abundance and spatial distribution of unusual mannose-enriched glycans that are typically found in lower microorganisms; this glycosignature was specific of LN as it was not observed in other kidney diseases. Exposure of mannosylated glycans in LN was found to occur at the cell surface of kidney cells promoting an increased recognition by specific glycans-recognizing receptors, expressed by immune cells. This abnormal glyco-signature of LN was demonstrated to be due to a deficient complex N-glycosylation and a proficient O-mannosylation pathway. Moreover, levels of mannosylation detected in kidney biopsies from LN patients at diagnosis were demonstrated to predict the development of chronic kidney disease (CKD) with 93% of specificity.

CONCLUSIONS

Cellular mannosylation is a marker of LN, predicting the development of CKD, and thus constituting a potential glycobiomarker to be included in the diagnostic and prognostic algorithm of LN.