Different glycoconjugate content in mucus secreting cells of the rat fundic gastric glands

Abstract

The fundic glands of the stomach contain two types of mucous cells: surface mucous cells (SMCs) located at the surface of the stomach and the pits, and mucous neck cells (MNCs) situated in the neck of the glands. They produce mucins, highly glycosylated proteins. Very little is known about the glycan composition of these mucins and of gastric secretion in general. We used several lectins combined with deglycosylation pretreatments to analyze the glycan composition of SMCs and MNCs. The results showed the presence of terminal sialic acid and subterminal Gal and GalNAc, which is consistent with previous knowledge about glycosylation in mucins. Our results also support previous reports that showed a different expression of mucins in the SMCs, depending on their superficial or deep location in the pit. Some lectins labeled only the perinuclear region of the SMCs, but not the apical region, where the secretory granules are stored. This suggests that the lectins are labeling sugar residues that are accessible to lectins during the first steps of glycan synthesis, which occurs in the endoplasmic reticulum and Golgi apparatus. Our results indicate that SMCs and MNCs produce a mucus secretion with a different glycoconjugate composition. The secretion is more varied in SMCs. As our results coincide with what we know about glycosylation of mucins, we can conclude that most of the glycans detected belong to mucins, and the differences in glycosylation observed in each cell type may be due, mainly, to the different secreted mucins.