title: Structural basis for sulfation-dependent self-glycan recognition by the human immune-inhibitory receptor Siglec-8.
abstract: Siglec-8 is a human immune-inhibitory receptor that, when engaged by specific self-glycans, triggers eosinophil apoptosis and inhibits mast cell degranulation, providing an endogenous mechanism to down-regulate immune responses of these central inflammatory effector cells. Here we used solution NMR spectroscopy to dissect the fine specificity of Siglec-8 toward different sialylated and sulfated carbohydrate ligands and determined the structure of the Siglec-8 lectin domain in complex with its prime glycan target 6'-sulfo sialyl Lewis(x) A canonical motif for sialic acid recognition, extended by a secondary motif formed by unique loop regions, recognizing 6-O-sulfated galactose dictates tight specificity distinct from other Siglec family members and any other endogenous glycan recognition receptors. Structure-guided mutagenesis revealed key contacts of both interfaces to be equally essential for binding. Our work provides critical structural and mechanistic insights into how Siglec-8 selectively recognizes its glycan target, rationalizes the functional impact of site-specific glycan sulfation in modulating this lectin-glycan interaction, and will enable the rational design of Siglec-8-targeted agonists to treat eosinophil- and mast cell-related allergic and inflammatory diseases, such as asthma.
authors.affiliation: Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland;
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Pröpster
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel, 4056 Basel, Switzerland.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel, 4056 Basel, Switzerland.
authors.forename: Said
authors.initials: S
authors.lastname: Rabbani
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel, 4056 Basel, Switzerland.
authors.forename: Beat
authors.initials: B
authors.lastname: Ernst
authors.affiliation: Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland; mario.schubert@sbg.ac.at allain@mol.biol.ethz.ch.
authors.forename: Frédéric H-T
authors.initials: FH
authors.lastname: Allain
authors.affiliation: Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland; mario.schubert@sbg.ac.at allain@mol.biol.ethz.ch.
authors.forename: Mario
authors.identifier: 0000-0003-0278-4091
authors.initials: M
authors.lastname: Schubert
mesh_terms: D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000944:Antigens, Differentiation, B-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D011134:Polysaccharides / Q000378:metabolism; D000072417:Protein Domains
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D037102:Lectins; D011134:Polysaccharides; C403967:SIGLEC8 protein, human
keywords: NMR spectroscopy; glycan sulfation; glycoimmunology; immune regulation; protein–carbohydrate recognition