title: Structural basis of myelin-associated glycoprotein adhesion and signalling.
abstract: Myelin-associated glycoprotein (MAG) is a myelin-expressed cell-adhesion and bi-directional signalling molecule. MAG maintains the myelin-axon spacing by interacting with specific neuronal glycolipids (gangliosides), inhibits axon regeneration and controls myelin formation. The mechanisms underlying MAG adhesion and signalling are unresolved. We present crystal structures of the MAG full ectodomain, which reveal an extended conformation of five Ig domains and a homodimeric arrangement involving membrane-proximal domains Ig4 and Ig5. MAG-oligosaccharide complex structures and biophysical assays show how MAG engages axonal gangliosides at domain Ig1. Two post-translational modifications were identified-N-linked glycosylation at the dimerization interface and tryptophan C-mannosylation proximal to the ganglioside binding site-that appear to have regulatory functions. Structure-guided mutations and neurite outgrowth assays demonstrate MAG dimerization and carbohydrate recognition are essential for its regeneration-inhibiting properties. The combination of trans ganglioside binding and cis homodimerization explains how MAG maintains the myelin-axon spacing and provides a mechanism for MAG-mediated bi-directional signalling.
authors.affiliation: Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Matti F
authors.initials: MF
authors.lastname: Pronker
authors.affiliation: Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Lemstra
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Department of Chemistry and Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Snijder
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Department of Chemistry and Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Albert J R
authors.identifier: 0000-0002-2405-4404
authors.initials: AJ
authors.lastname: Heck
authors.affiliation: Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute of Nanomaterials Science, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Dominique M E
authors.initials: DM
authors.lastname: Thies-Weesie
authors.affiliation: Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
authors.forename: R Jeroen
authors.initials: RJ
authors.lastname: Pasterkamp
authors.affiliation: Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Bert J C
authors.initials: BJ
authors.lastname: Janssen
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D018360:Crystallography, X-Ray; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D051379:Mice; D008954:Models, Biological; D008958:Models, Molecular; D018992:Myelin-Associated Glycoprotein / Q000737:chemistry* / Q000378:metabolism*; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D016501:Neurites / Q000378:metabolism; D000072417:Protein Domains; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D053838:Scattering, Small Angle; D015398:Signal Transduction; D012996:Solutions; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D018992:Myelin-Associated Glycoprotein; D012996:Solutions; D019158:N-Acetylneuraminic Acid