Studies of mucus in mouse stomach, small intestine, and colon. III. Gastrointestinal Muc5ac and Muc2 mucin O-glycan patterns reveal a regiospecific distribution.

The mouse intestinal mucus is mainly made up by the gel-forming Muc2 mucin and the stomach surface mucus Muc5ac, both extensively O-glycosylated. The oligosaccharide diversity provides a vast library of potential recognition sites for both commensal and pathogenic organisms. The mucin glycans are thus likely very important for the selection and maintenance of a stable intestinal flora.

Detailed O-glycomics of the Muc2 mucin from colon of wild-type, core 1- and core 3-transferase-deficient mice highlights differences compared with human MUC2.

The heavily O-glycosylated mucin MUC2 constitutes the major protein in the mucosal layer that acts as a physical barrier protecting the epithelial layer in the colon. In this study, Muc2 was purified from mucosal scrapings from the colon of wild-type (WT) mice, core 3 transferase knockout (C3Gnt(-/-)) mice and intestinal epithelial cell-specific core 1 knockout (IEC C1Galt1(-/-)) mice. The Muc2 O-glycans were released by reductive β-elimination and analyzed with liquid chromatography-mass spectrometry in the negative-ion mode.

Composition and functional role of the mucus layers in the intestine.

In discussions on intestinal protection, the protective capacity of mucus has not been very much considered. The progress in the last years in understanding the molecular nature of mucins, the main building blocks of mucus, has, however, changed this. The intestinal enterocytes have their apical surfaces covered by transmembrane mucins and the whole intestinal surface is further covered by mucus, built around the gel-forming mucin MUC2.

The two mucus layers of colon are organized by the MUC2 mucin, whereas the outer layer is a legislator of host-microbial interactions.

The normal intestinal microbiota inhabits the colon mucus without triggering an inflammatory response. The reason for this and how the intestinal mucus of the colon is organized have begun to be unraveled. The mucus is organized in two layers: an inner, stratified mucus layer that is firmly adherent to the epithelial cells and approximately 50 μm thick; and an outer, nonattached layer that is usually approximately 100 μm thick as measured in mouse.

Enhanced detection of sialylated and sulfated glycans with negative ion mode nanoliquid chromatography/mass spectrometry at high pH.

Negative ion mode nanoliquid chromatography/mass spectrometry (nano-LC/MS) on porous graphitic carbon columns at pH 11 was studied and compared to capillary LC/MS at pH 8 for the analysis of neutral and acidic glycan alditols. Oligosaccharides were chromatographed with an acetonitrile gradient containing 0.04% ammonium hydroxide and analyzed with a linear ion trap mass spectrometer (LTQ) equipped with a modified nanospray interface.

Cervical mucins carry alpha(1,2)fucosylated glycans that partly protect from experimental vaginal candidiasis.

Cervical mucins are glycosylated proteins that form a protective cervical mucus. To understand the role of mucin glycans in Candida albicans infection, oligosaccharides from mouse cervical mucins were analyzed by liquid chromatography-mass spectrometry. Cervical mucins carry multiple alpha(1-2)fucosylated glycans, but alpha(1,2)fucosyltransferase Fut2-null mice are devoid of these epitopes.

A complex, but uniform O-glycosylation of the human MUC2 mucin from colonic biopsies analyzed by nanoLC/MSn.

High-sensitivity glycan profiling providing detailed structural information is very important in the search for glycan disease markers. By combining a straight-forward and fast preparation protocol of mucins with high-throughput nanoLC/MS, we have been able to study the O-glycosylation of the colon MUC2 mucin from one single biopsy (approximately 5 mg wet tissue as starting material) collected from the sigmoid colon during routine colonoscopy of 25 normal control patients. This large mucin glycoprotein was recovered from the guanidinium chloride-extracted insoluble pellet, reduced and alkylated, separated by SDS-agarose polyacrylamide composite gel electrophoresis, and transferred to a PVDF membrane.

High-throughput and high-sensitivity nano-LC/MS and MS/MS for O-glycan profiling.

Sensitive and fast methods for the profiling of biologically important molecules are highly demanded. Mucins are densely O-glycosylated glycoproteins found at mucosal surfaces and are of great medical interest. Here we describe sensitive methods for the analysis of O-glycans from mucins using gel electrophoresis, and chromatography by nanoLC on graphite columns and structural analysis by electrospray mass spectrometry on a linear trap mass spectrometer.

Large scale identification of proteins, mucins, and their O-glycosylation in the endocervical mucus during the menstrual cycle.

The mucus filling the human cervical opening blocks the entry to the uterus, but this has to be relative and allow for the sperm to penetrate at ovulation. We studied this mucus, its content of proteins and mucins, and the mucin O-glycosylation in cervical secretions before, during, and after ovulation. Cervical mucosal secretions from 12 subjects were collected, reduced-alkylated, separated with polyacrylamide or agarose/polyacrylamide gel electrophoresis, and stained with silver, Alcian blue, or Coomassie Blue stain.