Significance of Sulfated Glycans on Mucins in the Gut

In the intestine, mucins function as a physical barrier separating the gut bacteria and the host. MUC2 mucin is a highly O-glycosylated glycoprotein, and its glycans are an essential post-translational modification for MUC2 function. In recent years, it has been discovered that specific structural units of the complex MUC2 glycans play distinct physiological functions. In particular, the sulfation of GlcNAc and Galactose in MUC2 glycans is essential for intestinal barrier function. Furthermore, gut bacteria utilize mucin sugar chains as a nutrient source by employing specific sulfatase enzymes, allowing them to colonize in the intestine. On the other hand, gut bacteria regulate host glycosylation through the induction of glycosyltransferase expression. In the light of recent studies on the structure and function of MUC2 glycans, mucins are not only functioning as a physical barrier but also as molecules that mediate complex interactions with gut microbiota. In this article, we discuss the function of MUC2 mucin and its glycosylation, with a particular focus on sulfated glycans.