Core fucosylation and its roles in gastrointestinal glycoimmunology

Glycosylation is a common post-translational modification in eukaryotic cells.It is involved in the production of many biologically active glycoproteins and the regulation of protein structure and function.Core fucosylation plays a vital role in the immune response.Most immune system molecules are core fucosylated glycoproteins such as complements,cluster differentiation antigens,immunoglobulins,cytokines,major histocompatibility complex molecules,adhesion molecules,and immune molecule synthesis-related transcription factors.These core fucosylated glycoproteins play important roles in antigen recognition and clearance,cell adhesion,lymphocyte activation,apoptosis,signal transduction,and endocytosis.Core fucosylation is dominated by fucosyltransferase 8(Fut8),which catalyzes the addition ofα-1,6-fucose to the innermost GlcNAc residue of N-glycans.Fut8 is involved in humoral,cellular,and mucosal immunity.Tumor immunology is associated with aberrant core fucosylation.Here,we summarize the roles and potential modulatory mechanisms of Fut8 in various immune processes of the gastrointestinal system.

Fucosylation and gastrointestinal cancer

Fucose (6-deoxy-L-galactose) is a monosaccharide that is found on glycoproteins and glycolipids in verteb rates, invertebrates, plants, and bacteria. Fucosylation, which comprises the transfer of a fucose residue to oligosaccharides and proteins, is regulated by many kinds of molecules, including fucosyltransferases, GDP-fucose synthetic enzymes, and GDP-fucose transporter(s). Dramatic changes in the expression of fucosylated oligosaccharides have been observed in cancer and inflammation. Thus, monoclonal antibodies and lectins recognizing cancer-associated fucosylated oligosaccharides have been clinically used as tumor markers for the last few de cades. Recent advanced glycomic approaches allow us to identify novel fucosylation-related tumor markers. Moreover, a growing body of evidence supports the functional significance of fucosylation at various pathophysiological steps of carcinogenesis and tumor progression. This review highlights the biological and medical signifi cance of fucosylation in gastrointestinal cancer.

Blocking Posttranslational Core Fucosylation Ameliorates Rat Peritoneal Mesothelial Cell Epithelial-Mesenchymal Transition

Background：Core fucosylation （CF）,catalyzed by α-1,6 fucosyltransferase （Fut8） in mammals,plays an important role in pathological processes through posttranslational modification of key signaling receptor proteins,including transforming growth factor （TGF）-β receptors and platelet-derived growth factor （PDGF） receptors.However,its effect on peritoneal fibrosis is unknown.Here,we investigated its influence on epithelial-mesenchymal transition （EMT） of rat peritoneal mesothelial cells （PMCs） in vitro induced by a high-glucose （HG） culture solution.Methods：Rat PMCs were first cultured in a HG （2.5%） culture solution to observe the CF expression level （fluorescein isothiocyanate-lens culinaris agglutinin）,we next established a knockdown model of rat PMCs in vitro with Fut8 small interfering RNA （siRNA） to observe whether inhibiting CF decreases the messenger RNA （mRNA） expression and protein expression of Fut8 and reverses EMT status.Rat PMCs were randomly divided into control group,mock group （transfected with scrambled siRNA）,Fut8 siRNA group,HG group,HG ＋ mock group,and HG ＋ Fut8 siRNA group.Finally,we examined the activation of TGF-β/Smad2/3 signaling and PDGF/extracellular signal-regulated kinase （ERK） signaling to observe the influence of CF on them.Results：CF,Fut8 mRNA,and protein expression were all significantly upregulated in HG-induced EMT model than those in the control rat PMCs （P 〈 0.05）.Fut8 siRNA successfully blocked CF of TGF-β receptors and PDGF receptors and attenuated the EMT status （E-cadherin and α-SMA and phenotypic changes） in HG-induced rat PMCs.In TGF-β/Smad2/3 signaling,Fut8 siRNA did not suppress the protein expression of TGF-3 receptors and Smad2/3;however,it significantly suppressed the phosphowlation of Smad2/3 （relative expression folds of HG ＋ Fut8 group vs.HG group：7.6 ± 0.4 vs.15.1 ± 0.6,respectively,P 〈 0.05）.In PDGF/ERK signaling,Fut8 siRNA did not suppress the protein expression of PDGF receptors and ERK,but it significantly suppressed the phosphorylation of ERK （relative expression folds of HG ＋ Fut8 group vs.HG group：8.7 ± 0.9 vs.15.6 ± 1.2,respectively,P 〈 0.05）.Blocking CF inactivated the activities of TGF-β and PDGF signaling pathways,and subsequently blocked EMT.Conclusions：These results demonstrate that CF contributes to rat PMC EMT.and that blocking it attenuates EMT.CF regulation is a potential therapeutic target of peritoneal fibrosis.

Alteration of liver N-glycome in patients with hepatocellular carcinoma

Purpose: Alteration of liver function during pro- gression of hepatocellular carcinoma (HCC) and cirrhosis affects the serum glycoprotein pattern. In this study, the changes in the N-glycome in liver tis- sue from patients with hepatocellular carcinoma and cirrhosis caused by hepatitis B virus infection were investigated to find out the relationship between this maker and liver disease. Methods: Twenty patients, 11 with cirrhosis and 9 with hepatocellular carcinoma, and 15 healthy donors were involved in this study. Liver protein N-glycans were profiled using the DSA-FACE technique developed in our laboratory. To further analyze the fucosylation status of these liver glycans Western lectin blots of total liver proteins were performed using Aspergillus oryzae lectin (AOL) as probe, which is a carbohydrate- binding protein that recognizes specifically α-1,6-fu- cosylated glycans. Results: The N-glycome of liver proteins in patients with HBV related HCC and cirrhosis was analyzed. Compared with healthy donors, the N-glycome had significantly less (p < 0.05) high mannose (M8) in both groups of patients. The total core α-1,6-fucosy-lation in total liver glycoproteins was dramatically increased during the progress of hepatocellular carcinoma and cirrhosis compared to the controls. Conclusion: These results show that fucosylation not only increases in serum proteins but also in liver tissue itself of patients with HBV related HCC and cirrhosis.

Gastrointestinal microbiome and Helicobacter pylori:Eradicate,leave it as it is,or take a personalized benefit-risk approach?

Helicobacter pylori(H.pylori)is generally regarded as a human pathogen and a class 1 carcinogen,etiologically related to gastric and duodenal ulcers,gastric cancer,and mucosa-associated lymphoid tissue lymphoma.However,H.pylori can also be regarded as a commensal symbiont.Unlike other pathogenic/opportunistic bacteria,H.pylori colonization in infancy is facilitated by T helper type 2 immunity and leads to the development of immune tolerance.Fucosylated gastric mucin glycans,which are an important part of the innate and adaptive immune system,mediate the adhesion of H.pylori to the surface of the gastric epithelium,contributing to successful colonization.H.pylori may have beneficial effects on the host by regulating gastrointestinal(GI)microbiota and protecting against some allergic and autoimmune disorders and inflammatory bowel disease.The potential protective role against inflammatory bowel disease may be related to both modulation of the gut microbiota and the immunomodulatory properties of H.pylori.The inverse association between H.pylori and some potentially proinflammatory and/or procarcinogenic bacteria may suggest it regulates the GI microbiota.Eradication of H.pylori can cause various adverse effects and alter the GI microbiota,leading to short-term or long-term dysbiosis.Overall,studies have shown that gastric Actinobacteria decrease after H.pylori eradication,Proteobacteria increase during short-term follow-up and then return to baseline levels,and Enterobacteriaceae and Enterococcus increase in the short-term and interim follow-up.Various gastric mucosal bacteria(Actinomyces,Granulicatella,Parvimonas,Peptostreptococcus,Prevotella,Rothia,Streptococcus,Rhodococcus,and Lactobacillus)may contribute to precancerous gastric lesions and cancer itself after H.pylori eradication.H.pylori eradication can also lead to dysbiosis of the gut microbiota,with increased Proteobacteria and decreased Bacteroidetes and Actinobacteria.The increase in gut Proteobacteria may contribute to adverse effects during and after eradication.The decrease in Actinobacteria,which are pivotal in the maintenance of gut homeostasis,can persist for>6 mo after H.pylori eradication.Furthermore,H.pylori eradication can alter the metabolism of gastric and intestinal bacteria.Given the available data,eradication cannot be an unconditional recommendation in every case of H.pylori infection,and the decision to eradicate H.pylori should be based on an assessment of the benefit-risk ratio for the individual patient.Thus,the current guidelines based on the unconditional"test-and-treat"strategy should be revised.The most cautious and careful approach should be taken in elderly patients with multiple eradication failures since repeated eradication can cause antibiotic-associated diarrhea,including severe Clostridioides difficile-associated diarrhea and colitis and antibiotic-associated hemorrhagic colitis due to Klebsiella oxytoca.Furthermore,since eradication therapy with antibiotics and proton pump inhibitors can lead to serious adverse effects and/or dysbiosis of the GI microbiota,supplementation of probiotics,prebiotics,and microbial metabolites(e.g.,butyrate+inulin)should be considered to decrease the negative effects of eradication.

Detection of fucosylated haptoglobin using the 10-7G antibody as a biomarker for evaluating endoscopic remission in ulcerative colitis

BACKGROUND Inflammatory bowel disease(IBD)is a chronic,relapsing inflammation of the digestive tract.Although fecal and serum biomarkers have been extremely important and supportive for monitoring of IBD,their low sensitivity and high variability characteristics limit clinical efficacy.Thus,the establishment of better biomarkers is expected.Fucosylation is one of the most important glycosylation modifications of proteins.Fucosylated haptoglobin(Fuc-Hpt)is used as a biomarker for several cancers and inflammation-related diseases.We recently established a novel glycan monoclonal antibody(mAb),designated 10-7G,which recognizes Fuc-Hpt.We developed an enzyme-linked immunosorbent assay(ELISA)to measure serum levels of Fuc-Hpt(10-7G values).AIM To investigate the usefulness of the serum 10-7G values as a potential biomarker for monitoring disease activity in IBD.METHODS This was a case control study.Intestinal tissues of IBD patients(n=10)were examined immunohistochemically using the 10-7G mAb.We determined 10-7G values using serum from patients with ulcerative colitis(UC,n=110),Crohn’s disease(n=45),acute enteritis(AE,n=11),and healthy volunteers(HVs)who exhibited normal(n=20)or high(n=79)C-reactive protein(CRP)levels at medical check-up.We investigated the correlation between the 10-7G value and various clinical parameters of IBD patients by correlation analysis.Receiver operating characteristic(ROC)curve analysis was performed to evaluate the usefulness of the 10-7G values as a biomarker for clinical and endoscopic remission of UC compared to conventional serum biomarkers.RESULTS In the immunohistochemical analysis,positive 10-7G mAb staining was observed in lymphocytes infiltrating into inflammatory sites of the mucosal layer and lymphoid follicles.The 10-7G values were significantly higher in patients with IBD(P<0.001)and AE(P<0.05)compared with HVs.In addition,10-7G values were correlated with clinical examination parameters related to inflammation in patients with UC,particularly the CRP level(rs=0.525,P=0.003)and clinical activity index score(rs=0.435,P=0.038).However,there was no correlation between 10-7G values and CRP in HVs with high CRP levels,suggesting that the 10-7G values is not the same as a general inflammation biomarker.ROC curve analysis showed that area under the curve(AUC)value of 10-7G values for the diagnosis of endoscopic remission was higher than other biomarkers(AUC value=0.699).CONCLUSION The serum 10-7G value is a novel biomarker for evaluating intestinal inflammation and endoscopic mucosal healing in UC.

Distribution of Fucosylated Xyloglucans among the Walls of Different Cell Types in Monocotyledons Determined by Immunofluorescence Microscopy

Xyloglucans in the non-lignified primary cell walls of different species of monocotyledons have diverse struc- tures, with widely varying proportions of oligosaccharide units that contain fucosylated side chains （F side chains）. To determine whether fucosylated xyloglucans occur in all non-lignified walls in a range of monocotyledon species, we used immunofluorescence microscopy with the monoclonal antibody CCRC-M1. The epitope of this antibody, α-L-FUCp-（1 →2）- β-D-Galp, occurs in F side chains. In most non-commelinid monocotyledons, the epitope was found in all non-lignified walls. A similar distribution was found in the palm Phoenix canariensis, which is a member of the basal commelinid order Arecales. However, in the other commelinid orders Zingiberales, Commelinales, and Poales, the occurrence of the epitope was restricted, sometimes occurring in only the phloem walls, but often also in walls of other cell types including stomatal guard and subsidiary cells and raphide idioblasts. No epitope was found in the walls of the commelinids Tradescantia virginiana （Commelinaceae, Commelinales） and Zea mays （Poaceae, Poales）, but it occurred in the phloem walls of two other Poaceae species, Lolium multiflorum and L. perenne. The distribution of the epitope is discussed in relation to xyloglucan structures in the different taxa. However, the functional significance of the restricted distributions is unknown.