The importance of post-translational glycosylation in the secretory pathway for expansion of the functional repertoire of gene products

Most proteins in animal and plant cells are glycosylated, a fact that must be taken into account for all aspects of protein studies, because the glycan portion often influences protein activity and cellular targeting, and more practically, protein purific ation, crystallization and structural determination. The biosynthesis of glycans, unlike nucleic acids and proteins, is not template-based. Glycans are formed on their protein or lipid scaffolds by glycosyltransferases and glycosidases as they traffic thr ough the secretory pathway in the lumens of the endoplasmic reticulum and the Golgi apparatus. In mammals, glycans are mainly constructed from ten monosaccharide building blocks that can be connected to one another through glycosidic linkages in an unbeat able number of combinations. While four amino acids selected from the regular menu of twenty can give rise to approximately 16 thousand different combinations, can four mammalian monosaccharides from the regular menu of ten produce 15 million different st ructures, due to the different substrate specificities of the enzymes involved. Today, the glycan research area engages fewer scientists than the genomic and proteomic fields, but glycomics is the third step of the stairs to complete understanding of prot ein synthesis, sorting, transport, and activity, and is expected to expand dramatically in the years to come. This application is aiming at further development of studies of glycosylation in the apical and basolateral pathways of epithelial and endotheli al cells, and the potential roles of a particular group of PGs, lecticans, in the secretory pathway. We aim at developing a Nordic collaboration to solve the questions raised more efficiently, by sharing techniques, reagents and know-how. Turku/Åbo streng th: Immunological detection of glycans. Lund and Copenhagen strength: Protein (lectin) - glycan interactions. Oslo strength: Determination of glycan structures by high performance liquid chromatography (HPLC).