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 α1,4-GlcNAc-like and GalNAcβ1-4GlcNAc-like (LacdiNAc-like), were common modifications of human gastric O-glycans. Furthemore, each individual carried 1-14 glycan structures that were unique for that individual. The diversity and alterations in gastric O-glycosylation broaden our understanding of the human gastric O-glycome and its implications for gastric cancer research and emphasize that the high individual variation makes it difficult to identify gastric cancer specific structures. However, despite the low number of individuals, we could verify a higher level of sialylation and sulfation on gastric O-glycans from cancerous tissue than from healthy stomachs.
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 GalNAc1-4GlcNAc-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...
There is an increasing interest in the use of dried blood spot (DBS) sampling and multiple reaction monitoring in proteomics. Although several groups have explored the utility of DBS by focusing on protein detection, the reproducibility of the approach and whether it can be used for biomarker discovery in high throughput studies is yet to be determined. We assessed the reproducibility of multiplexed targeted protein measurements in DBS compared to serum. Eighty-two medium to high abundance proteins were monitored in a number of technical and biological replicates. Importantly, as part of the data analysis, several statistical quality control approaches were evaluated to detect inaccurate transitions. After implementing statistical quality control measures, the median CV on the original scale for all detected peptides in DBS was 13.2% and in Serum 8.8%. We also found a strong correlation (r = 0.72) between relative peptide abundance measured in DBS and serum. The combination of minimally invasive sample collection with a highly specific and sensitive mass spectrometry (MS) technique allows for targeted quantification of multiple proteins in a single MS run. This approach has the potential to fundamentally change clinical proteomics and personalized medicine by facilitating large-scale studies.
The Gram-negative bacteria Campylobactor jejuni is the primary bacteria responsible for food poisoning in industrialized countries, and acute diarrheal illness is a leading cause of mortality among children in developing countries. C. jejuni are commensal in chickens. They are particularly abundant in the caecal crypts, and poultry products are commonly infected as a result of crosscontamination during processing. The interactions between C. jejuni and chicken intestinal tissues as well as the pathogenic molecular mechanisms of colonization in humans are unknown, but identifying these factors could provide potential targets to reduce the incidence of campylobacteriosis. Recently, purified chicken intestinal mucin was shown to attenuate adherence and invasion of C. jejuni in the human colorectal adenocarcinoma cell line HCT-8 in vitro, and this effect was attributed to mucin O-glycosylation. Mucins from different regions of the chicken intestine inhibited C. jejuni binding and internalization differentially, with large intestine>small intestine>caecum. Here, we use LC-MS to perform a detailed structural analysis of O-glycans released from mucins purified from chicken large intestine, small intestine, and caecum. The O-glycans identified were abundantly sulfated compared with the human intestines, and sulfate moieties were present throughout the chicken intestinal tract. Interestingly, alpha 1-2 linked fucose residues, which have a high binding affinity to C. jejuni, were identified in the small and large intestines. Additionally, N-glycolylneuraminic/N-acetylneuraminic acid containing structures present as Sd a -like epitopes were identified in large intestine samples but not small intestine or caecum. O-glycan structural characterization of chicken intestinal mucins provides insights into adherence and invasion properties of C. jejuni, and may offer prospective candidate molecules aimed at reducing the incidence of infection. Molecular & Cellular
Isolation of MUC5AC mucins from the gastric mucosa from two secretor individuals (one from normal mucosa from a patient with gastric cancer and one from a control) showed different abilities to bind and induce the proliferation of the Helicobacter pylori strain J99. Analysis of the released O-linked oligosaccharides by LC-MS from these individuals showed a very heterogeneous mixture of species from the cancer patient containing both neutral and sialylated structures, whereas the normal sample showed dominating neutral blood group H terminating structures as well as neutral structures containing the di-N-acetyllactosamine (lacdiNAc) unit GalNAcβ1-4GlcNAcβ1- on the C-6 branch of the reducing end GalNAc. The linkage configuration of these epitopes were determined using C-4-specific fragmentation for the GalNAcβ1-4GlcNAcβ1- glycosidic linkage, comparison of the MS(3) fragmentation with standards for linkage configuration and N-acetylhexosamine type as well as exoglycosidase treatment. It was also shown that the lacdiNAc epitope is present in both human and porcine gastric mucins, indicating that this is an epitope preserved between species. We hypothesize that the termination on gastric MUC5AC with lacdiNAc is in competition with complex glycosylation such as the Le(b) and H type 1 as well as complex sialylated structures. These are epitopes known to bind the H. pylori BabA and SabA adhesins.
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