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

Abstract

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 negativeion mode. Muc2 from the distal colon of WTand C3Gnt-/- knockout mice carried a mixture of core 1- or core 2-type glycans, whereas Muc2 from IEC C1Galt1-/- mice carried highly sialylated core 3- and core 4-type glycans. A large portion of NeuAc in all mouse models was positioned on disialylated N-acetyllactosamine units, an epitope not reported on human colonic MUC2. Mass spectra and proton NMR spectroscopy revealed an abundant NeuAc linked to internally positioned N-acetylglucosamine on colonic murine Muc2, which also differs markedly from human MUC2. Our results highlight that murine colonic Muc2 O-glycosylation is substantially different from human MUC2, which could be one explanation for the different commensal microbiota of these two species. © The Author 2012. Published by Oxford University Press. All rights reserved.