title: Endogenous airway mucins carry glycans that bind Siglec-F and induce eosinophil apoptosis.
abstract: BACKGROUND
  Sialic acid-binding, immunoglobulin-like lectin (Siglec) F is a glycan-binding protein selectively expressed on mouse eosinophils. Its engagement induces apoptosis, suggesting a pathway for ameliorating eosinophilia in the setting of asthma and other eosinophil-associated diseases. Siglec-F recognizes sialylated sulfated glycans in glycan-binding assays, but the identities of endogenous sialoside ligands and their glycoprotein carriers in vivo are unknown.
  
  
  OBJECTIVE
  To use mouse lung-derived materials to isolate, biochemically identify, and biologically characterize naturally occurring endogenous glycan ligands for Siglec-F.
  
  
  METHODS
  Lungs from normal and mucin-deficient mice, as well as mouse tracheal epithelial cells, were investigated in vitro and in vivo for the expression of Siglec-F ligands. Western blotting and cytochemistry used Siglec-F-Fc as a probe for directed purification, followed by liquid chromatography-tandem mass spectrometry of recognized glycoproteins. Purified components were tested in mouse eosinophil-binding assays and flow cytometry-based cell death assays.
  
  
  RESULTS
  We detected mouse lung glycoproteins that bound to Siglec-F; binding was sialic acid dependent. Proteomic analysis of Siglec-F binding material identified Muc5b and Muc4. Cross-affinity enrichment and histochemical analysis of lungs from mucin-deficient mice assigned and validated the identity of Muc5b as one glycoprotein ligand for Siglec-F. Purified mucin preparations carried sialylated and sulfated glycans, bound to eosinophils and induced their death in vitro. Mice conditionally deficient in Muc5b displayed exaggerated eosinophilic inflammation in response to intratracheal installation of IL-13.
  
  
  CONCLUSIONS
  These data identify a previously unrecognized endogenous anti-inflammatory property of airway mucins by which their glycans can control lung eosinophilia through engagement of Siglec-F.
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, Baltimore, MD 21224.
authors.forename: Takumi
authors.initials: T
authors.lastname: Kiwamoto
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Katoh
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, University of Colorado School of Medicine, Denver, CO 80045.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Evans
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, University of Colorado School of Medicine, Denver, CO 80045.|Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, National Jewish Health, Denver, CO, 80206.
authors.forename: William J
authors.initials: WJ
authors.lastname: Janssen
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, Baltimore, MD 21224.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Brummet
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, Baltimore, MD 21224.
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Hudson
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, Baltimore, MD 21224.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602.
authors.forename: Michael
authors.initials: M
authors.lastname: Tiemeyer
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, Baltimore, MD 21224.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Bochner
mesh_terms: D000818:Animals; D015214:Antigens, Differentiation, Myelomonocytic; D017209:Apoptosis / Q000276:immunology; D002352:Carrier Proteins; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology; D004804:Eosinophils / Q000276:immunology* / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D016130:Immunophenotyping; D008024:Ligands; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D055264:Mucin-4 / Q000378:metabolism; D055257:Mucin-5B / Q000378:metabolism; D009077:Mucins / Q000737:chemistry / Q000378:metabolism*; D010641:Phenotype; D011134:Polysaccharides / Q000378:metabolism*; D011485:Protein Binding; D040901:Proteomics / Q000379:methods; D063265:Sialic Acid Binding Immunoglobulin-like Lectins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015214:Antigens, Differentiation, Myelomonocytic; D002352:Carrier Proteins; D016207:Cytokines; D008024:Ligands; D055264:Mucin-4; D055257:Mucin-5B; D009077:Mucins; D011134:Polysaccharides; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; C443130:Siglecf protein, mouse
keywords: Eosinophil; Muc4; Muc5b; Siglec-F; airway; apoptosis; asthma; epithelium; glands; glycan ligands; lung; mucin