Glycoproteomic analysis identifies cryptdin-related sequence 1 as O-glycosylated protein modified with α1,2-fucose in the small intestine.

Abstract

The modification of galactose with α1,2-fucose is involved in symbiosis with intestinal bacteria and elimination of pathogenic bacteria. It is postulated that α1,2-fucosylated mucin secreted from goblet cells is involved in defending an organism against infections, but the detailed molecular mechanisms are yet to be elucidated. It was previously reported that Paneth cells of the small intestine were positive for UEA-1 lectin staining. However, glycoproteins in Paneth cells carrying α1,2-fucose have not yet been identified. Glycoproteomic analysis of ileal lysates identified 3212 O-linked and 2962 N-linked glycopeptides. In particular, cryptdin-related sequence 1 (CRS1) expressed in Paneth cells was found to be α1,2-fucosylated. Unlike other antimicrobial α-defensin proteins, CRS1 contains unique Thr residues, which are modified with O-glycans, with 3HexNAc2Hex1Fuc1NeuAc being the main glycoform. Identification of α1,2-fucose on the O-glycans of CRS1 expressed in Paneth cells will pave the way for a mechanistic understanding of α1,2-fucose-dependent symbiosis with intestinal bacteria and elimination of pathogenic bacteria in the intestine.