title: Galactosyltransferase 4 is a major control point for glycan branching in N-linked glycosylation.
abstract: Protein N-glycosylation is a common post-translational modification that produces a complex array of branched glycan structures. The levels of branching, or antennarity, give rise to differential biological activities for single glycoproteins. However, the precise mechanism controlling the glycan branching and glycosylation network is unknown. Here, we constructed quantitative mathematical models of N-linked glycosylation that predicted new control points for glycan branching. Galactosyltransferase, which acts on N-acetylglucosamine residues, was unexpectedly found to control metabolic flux through the glycosylation pathway and the level of final antennarity of nascent protein produced in the Golgi network. To further investigate the biological consequences of glycan branching in nascent proteins, we glycoengineered a series of mammalian cells overexpressing human chorionic gonadotropin (hCG). We identified a mechanism in which galactosyltransferase 4 isoform regulated N-glycan branching on the nascent protein, subsequently controlling biological activity in an in vivo model of hCG activity. We found that galactosyltransferase 4 is a major control point for glycan branching decisions taken in the Golgi of the cell, which might ultimately control the biological activity of nascent glycoprotein.
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: McDonald
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Jerrard M
authors.initials: JM
authors.lastname: Hayes
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Tania
authors.initials: T
authors.lastname: Bezak
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Sonia A
authors.initials: SA
authors.lastname: Głuchowska
authors.affiliation: National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Eoin F J
authors.initials: EF
authors.lastname: Cosgrave
authors.affiliation: National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Weston B
authors.initials: WB
authors.lastname: Struwe
authors.affiliation: Merck, Sharp & Dohme, 5340 BH Oss, The Netherlands.
authors.forename: Corné J M
authors.initials: CJ
authors.lastname: Stroop
authors.affiliation: Merck, Sharp & Dohme, 5340 BH Oss, The Netherlands.
authors.forename: Han
authors.initials: H
authors.lastname: Kok
authors.affiliation: Merck, Sharp & Dohme, 5340 BH Oss, The Netherlands.
authors.forename: Teun
authors.initials: T
authors.lastname: van de Laar
authors.affiliation: National Institute for Bioprocessing Research and Training (NIBRT), Fosters Avenue, Dublin 4, Ireland.
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Rudd
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Keith F
authors.initials: KF
authors.lastname: Tipton
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland gdavey@tcd.ie.
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Davey
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D006063:Chorionic Gonadotropin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D003198:Computer Simulation; D003412:Cricetulus; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D007527:Isoenzymes; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D008958:Models, Molecular; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D051381:Rats; D012669:Seminal Vesicles / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D006063:Chorionic Gonadotropin; D007527:Isoenzymes; D017351:N-Acetylglucosaminyltransferases; C038111:alpha-1,3-mannosylglycoprotein beta-1,4-N-acetylglucosaminyltransferase; D000117:Acetylglucosamine
keywords: Chorionic gonadotropin; Galactosyltransferase; Glycosylation; Golgi; branching; hCG