title: The glucuronyltransferase B4GAT1 is required for initiation of LARGE-mediated α-dystroglycan functional glycosylation.
abstract: Dystroglycan is a cell membrane receptor that organizes the basement membrane by binding ligands in the extracellular matrix. Proper glycosylation of the α-dystroglycan (α-DG) subunit is essential for these activities, and lack thereof results in neuromuscular disease. Currently, neither the glycan synthesis pathway nor the roles of many known or putative glycosyltransferases that are essential for this process are well understood. Here we show that FKRP, FKTN, TMEM5 and B4GAT1 (formerly known as B3GNT1) localize to the Golgi and contribute to the O-mannosyl post-phosphorylation modification of α-DG. Moreover, we assigned B4GAT1 a function as a xylose β1,4-glucuronyltransferase. Nuclear magnetic resonance studies confirmed that a glucuronic acid β1,4-xylose disaccharide synthesized by B4GAT1 acts as an acceptor primer that can be elongated by LARGE with the ligand-binding heteropolysaccharide. Our findings greatly broaden the understanding of α-DG glycosylation and provide mechanistic insight into why mutations in B4GAT1 disrupt dystroglycan function and cause disease.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Tobias
authors.initials: T
authors.lastname: Willer
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Kei-Ichiro
authors.initials: K
authors.lastname: Inamori
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: David
authors.initials: D
authors.lastname: Venzke
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Corinne
authors.initials: C
authors.lastname: Harvey
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Greg
authors.initials: G
authors.lastname: Morgensen
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hara
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Beltrán Valero de Bernabé
authors.affiliation: Medical Nuclear Magnetic Resonance Facility, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.affiliation: Vollum Institute, Oregon Health and Science University, Portland, United States.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Wright
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Carver College of Medicine, Iowa City, United States.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Campbell
mesh_terms: D000818:Animals; D002460:Cell Line; D049030:Dystroglycans / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism; D020723:Glucuronic Acid / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D017351:N-Acetylglucosaminyltransferases / Q000172:deficiency* / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D014994:Xylose / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D049030:Dystroglycans; D020723:Glucuronic Acid; D014994:Xylose; C117674:LARGE1 protein, human; C502747:Large1 protein, mouse; D017351:N-Acetylglucosaminyltransferases; C530032:B4gat1 protein, mouse
keywords: B3GNT1; B4GAT1; LARGE; alpha-dystroglycan; basement membrane; biochemistry; glycosylation; human biology; medicine; mouse