Exploring the diverse biological significance and roles of fucosylated oligosaccharides

Long since, carbohydrates were thought to be used just as an energy source and structural material. However, in recent years, with the emergence of the field of glycobiology and advances in glycomics, much has been learned about the biological role of oligosaccharides, a carbohydrate polymer containing a small number of monosaccharides, in cell-cell interaction, signal transduction, immune response, pathogen adhesion processes, early embryogenesis, and apoptosis. The function of oligosaccharides in these processes is diversified by fucosylation, also known as modification of oligosaccharides. Fucosylation has allowed the identification of more than 100 different oligosaccharide structures that provide functional diversity. ABO blood group and Lewis antigens are among the best known fucosyl-linked oligosaccharides. In addition, the antigens in the ABO system are composed of various sugar molecules, including fucosylated oligosaccharides, and Lewis antigens are structurally similar to ABO antigens but differ in the linkage of sugars. Variation in blood group antigen expression affects the host's susceptibility to many infections. However, altered expression of ABO and Lewis antigens is related with prognosis in carcinoma types. In addition, many pathogens recognize and bind to human tissues using a protein receptor with high affinity for the fucose molecule in glycoconjugates, such as lectin. Fucosylated oligosaccharides also play vital roles during fertilization and early embryogenesis. Learning and memory-related processes such as neurite growth, neurite migration, and synapse formation seen during the development of the brain, which is among the first organs to develop in embryogenesis, are regulated by fucosylated oligosaccharides. In conclusion, this review mentions the vital roles of fucosylated oligosaccharides in biology, drawing attention to their importance in the development of chemical tools to be used in function analysis and the investigation of various therapeutic targets.

Airway epithelial wound repair: role of carbohydrate sialyl Lewisx

Epithelial repair is a complex cellular and molecular process, the details of which are still not clearly understood. Plasma membrane glycoconjugates can modulate cell function by altering the function of protein and lipids. Sialyl Lewisx (sLex), a fucose-containing tetrasaccharide, decorates membrane-bound and secreted proteins and mediates cell-cell interaction. In the present study we investigated the role of sLex in airway epithelial repair. Using immunohistochemistry, we showed an increased expression of sLex in areas of damaged bronchial epithelium compared with intact regions. Confluent monolayers of airway epithelial cells were mechanically wounded and allowed to close. Wounded monolayers were photographed for wound closure kinetics, fixed for immunocytochemical studies, or subjected to RNA extraction. Examining the expression of different alpha1,3-fucosyltransferases (FucT), enzymes that mediate the final step in the synthesis of sLex, we found that FucT-IV was the common gene expressed in all cell lines and primary airway epithelial cells. We demonstrated an increased expression of sLex over time after mechanical injury. Blocking of sLex with an inhibitory antibody completely prevented epithelial repair. Our data suggest an essential functional role for sLex in epithelial repair. Further studies are necessary to explore the exact mechanism for sLex in mediating cell-cell interaction in bronchial epithelial cells to facilitate epithelial migration and repair.