title: LARGE2-dependent glycosylation confers laminin-binding ability on proteoglycans.
abstract: Both LARGE1 (formerly LARGE) and its paralog LARGE2 are bifunctional glycosyltransferases with xylosy- and glucuronyltransferase activities, and are capable of synthesizing polymers composed of a repeating disaccharide [-3Xylα1,3GlcAβ1-]. Post-translational modification of the O-mannosyl glycan of α-dystroglycan (α-DG) with the polysaccharide is essential for it to act as a receptor for ligands in the extracellular matrix (ECM), and both LARGE paralogs contribute to the modification in vivo. LARGE1 and LARGE2 have different tissue distribution profiles and enzymatic properties; however, the functional difference of the homologs remains to be determined, and α-DG is the only known substrate for the modification by LARGE1 or LARGE2. Here we show that LARGE2 can modify proteoglycans (PGs) with the laminin-binding glycan. We found that overexpression of LARGE2, but not LARGE1, mediates the functional modification on the surface of DG-/-, Pomt1-/-and Fktn-/-embryonic stem cells. We identified a heparan sulfate-PG glypican-4 as a substrate for the LARGE2-dependent modification by affinity purification and subsequent mass spectrometric analysis. Furthermore, we showed that LARGE2 could modify several additional PGs with the laminin-binding glycan, most likely within the glycosaminoglycan (GAG)-protein linkage region. Our results indicate that LARGE2 can modify PGs with the GAG-like polysaccharide composed of xylose and glucuronic acid to confer laminin binding. Thus, LARGE2 may play a differential role in stabilizing the basement membrane and modifying its functions by augmenting the interactions between laminin globular domain-containing ECM proteins and PGs.
authors: Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, and.|Department of Neurology, Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242-1101, USA.|Division of Glycopathology, Institute of Molecular Biomembrane and Glycobiology, Tohoku Medical and Pharmaceutical University, Sendai, Miyagi 981-8558, Japan.
authors: Kei-Ichiro
authors: KI
authors: Inamori
authors: Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, and.|Department of Neurology, Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242-1101, USA.|Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602.
authors: Aaron M
authors: AM
authors: Beedle
authors: Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, and.|Department of Neurology, Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242-1101, USA.
authors: Daniel Beltrán-Valero
authors: DB
authors: de Bernabé
authors: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602.|Department of Molecular Physiology and Biophysics, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242-1101, USA.
authors: Michael E
authors: ME
authors: Wright
authors: Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, and kevin-campbell@uiowa.edu.|Department of Neurology, Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242-1101, USA.
authors: Kevin P
authors: KP
authors: Campbell
mesh_terms: D000818:Animals; D001665:Binding Sites; D053595:Embryonic Stem Cells / Q000378:metabolism; D006031:Glycosylation; D016695:Glycosyltransferases / Q000737:chemistry / Q000378:metabolism*; D007797:Laminin / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007797:Laminin; D011509:Proteoglycans; D016695:Glycosyltransferases; C507407:Large2 protein, mouse
keywords: dystroglycan, glycosaminoglycan, laminin binding, LARGE2, proteoglycan