Structural Diversity of Human Gastric Mucin Glycans

Abstract

The mucin O-glycosylation of 10 individuals with and without gastric disease was examined in depth in order to generate a structural map of human gastric glycosylation. In the stomach, these mucins and their O-glycosylation protect the epithelial surface from the acidic gastric juice and provide the first point of interaction for pathogens such as Helicobacter pylori, reported to cause gastritis, gastric and duodenal ulcers and gastric cancer. The rational of the present study was to map the O-glycosylation that the pathogen may come in contact with. An enormous diversity in glycosylation was found, which varied both between individuals and within mucins from a single individual: mucin glycan chain length ranged from 2-13 residues, each individual carried 34 -103 O-glycan structures and in total over 258 structures were identified. The majority of gastric O-glycans were neutral and fucosylated. Blood group I antigens, as well as terminal ␣1,4-GlcNAc-like and GalNAc␤1-4GlcNAc-like (LacdiNAc-like), were common modifications of human gastric O-glycans. Gastric cancer is the second most common cause of cancer-associated death and fourth most commonly diagnosed cancer worldwide (1). Annually, 0.7 million patients with gastric cancer die globally (2). The cancer is associated with glycosylation changes, but how alteration of gastric mucins relates to gastric cancer pathogenesis remains unknown. Despite the protection by mucins and the acidic gastric juice and proteolytic enzymes, the bacterium Helicobacter pylori manage to thrive in the gastric lining, infecting about half of the world's population (3). There is a direct correlation between infection and gastric cancer, where 0.1-3% of infected individuals develop gastric adenocarcinoma or mucosa-associated lymphoid tissue lymphoma and another 10 -15% develop symptomatic gastritis or gastric and duodenal ulcers, whereas the majority show no symptoms (4).In the stomach, MUC5AC and MUC6 are the major secreted mucins, whereas MUC1 is the dominant membraneassociated mucin. MUC5AC is produced by the surface epithelium, whereas MUC6 is secreted from the deep glands of the gastric mucosa (5, 6). Both MUC5AC and MUC6 are large oligomeric mucins that occur as distinct glycoforms (7). In gastric precancerous lesions and cancer, altered expression of MUC5AC, MUC6, MUC2, and MUC5B has been described, with MUC2 being a marker for intestinal metaplasia (8, 9). The gastric surface and foveolar epithelium are formed by a single layer of tall columnar mucin-producing cells that have a basal nucleus below an apical cup of mucin. These cells have a turnover rate of 3-6 days, but the mucus layer produced in these cells have an even shorter life span: the production rate from start of glycosylation until release at the apical side is about 6 h (10), demonstrating that both the mucin repertoire and glycosylation theoretically can change rapidly. The carbohydrate structures present on mucosal surfaces vary according to cell lineage, tissue location, and developmental stage (11). The massive...

O‐glycan truncation enhances cancer‐related functions of CD44 in gastric cancer

“…MKN45 WT and mock expresses primarily core 2 O‐glycans with 2 or more LacNAc repeats . This glycosylation profile is reflective of some gastric carcinomas . Although different genes were targeted in our glyco‐engineered models, the early termination of O‐glycans was a common feature of the three cell line models.…”

BabA-mediated adherence of pediatric ulcerogenic H. pylori strains to gastric mucins at neutral and acidic pH

“…Binding of the H. pylori strains isolated from PUD patients was increased compared to the binding of NUD strains to all mucins at both acidic and neutral pH, with higher binding activity at pH 2 than at pH 7 (p≤0.05, Figure 1(a-c)). Based on the strain genotype (babA, sabA and labA status) and mucin glycosylation, a similar proportion of the strains are expected to bind to mucins among the PUD and NUD strains at pH 7: 8/ 11 PUD vs 6/9 NUD would theoretically be expected to bind to the mucin from the human gastric tumor mucosa (Le b+ , SLe x+ , LacdiNAc + , sulfate + ), 9/11 PUD vs 9/9 NUD to the mucin from the human gastric normal mucosa (Le b+ , SLe x-, LacdiNAc + ) and 5/11 PUD vs 5/9 NUD to the mucin from the monkey normal gastric mucosa (Le b-, SLe x+ , LacdiNAc − , + II M 10 DU 417/02 SRR6906463 -+ -+ on off on + (2 copies) --I/II M 1 DU 441/02 SRP064603* + + + + on on off -s1 # + I F 9 D U 559/02 SRP064604* + + -+ on off on + (1 copy) [39], and Jin et al [26]. d Human gastric normal mucins used in the bacterial growth assays.…”

“…At both neutral and acidic pH, PUD H. pylori strains bind better to mucins than NUD strains Gastric mucins carry between 40 to100 different glycan structures resulting in a mucin glycosylation pattern that differs between individuals and also depends on health status [26]. We analyzed the binding levels of H. pylori strains isolated from children with NUD (n=9) or PUD (n=11), to gastric mucins with and without functional binding sites for the previously published H. pylori binding modes, BabA, SabA, LabA and the charge dependent mechanism at acidic pH [9][10][11][12].…”

“…The rhesus monkey sample was positive for H. suis but was otherwise normal (gastritis score < 1 according to the Sydney system) [39]. The isolated human mucins have been previously characterized in detail [26,29,39]. We also screened three rhesus monkeys gastric mucins from our archived mucin library using mass spectrometry (results in supplementary table S1) and selected one negative for Le b and lacdiNAc to complement the glycan repertoir of the human mucins [26].…”

“…The isolated human mucins have been previously characterized in detail [26,29,39]. We also screened three rhesus monkeys gastric mucins from our archived mucin library using mass spectrometry (results in supplementary table S1) and selected one negative for Le b and lacdiNAc to complement the glycan repertoir of the human mucins [26]. Additionally, two mucins (3IS: Le b positive/ɑ1,4-GlcNAc negative, and 4ID: Le b negative/ɑ1,4-GlcNAc positive) were isolated from human normal gastric tissue obtained from obese patients undergoing bariatric surgery and were used in bacterial proliferation assays.…”