title: A systematic study of site-specific GalNAc-type O-glycosylation modulating proprotein convertase processing.
abstract: Site-specific GalNAc-type O-glycosylation is emerging as an important co-regulator of proprotein convertase (PC) processing of proteins. PC processing is crucial in regulating many fundamental biological pathways and O-glycans in or immediately adjacent to processing sites may affect recognition and function of PCs. Thus, we previously demonstrated that deficiency in site-specific O-glycosylation in a PC site of the fibroblast growth factor, FGF23, resulted in marked reduction in secretion of active unprocessed FGF23, which cause familial tumoral calcinosis and hyperostosis hyperphosphatemia. GalNAc-type O-glycosylation is found on serine and threonine amino acids and up to 20 distinct polypeptide GalNAc transferases catalyze the first addition of GalNAc to proteins making this step the most complex and differentially regulated steps in protein glycosylation. There is no reliable prediction model for O-glycosylation especially of isolated sites, but serine and to a lesser extent threonine residues are frequently found adjacent to PC processing sites. In the present study we used in vitro enzyme assays and ex vivo cell models to systematically address the boundaries of the region within site-specific O-glycosylation affect PC processing. The results demonstrate that O-glycans within at least ±3 residues of the RXXR furin cleavage site may affect PC processing suggesting that site-specific O-glycosylation is a major co-regulator of PC processing.
authors.affiliation: Center for Glycomics, Department of Cellular and Molecular Medicine and School of Dentistry, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
authors.forename: Katrine Ter-Borch Gram
authors.initials: KT
authors.lastname: Schjoldager
authors.forename: Malene B
authors.initials: MB
authors.lastname: Vester-Christensen
authors.forename: Christoffer K
authors.initials: CK
authors.lastname: Goth
authors.forename: Thomas Nordahl
authors.initials: TN
authors.lastname: Petersen
authors.forename: Søren
authors.initials: S
authors.lastname: Brunak
authors.forename: Eric P
authors.initials: EP
authors.lastname: Bennett
authors.forename: Steven B
authors.initials: SB
authors.lastname: Levery
authors.forename: Henrik
authors.initials: H
authors.lastname: Clausen
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D045683:Furin / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D046188:Protein Modification, Translational / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D059748:Proteolysis
chemical_list: C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D045683:Furin