Sialylated keratan sulfate proteoglycans are Siglec-8 ligands in human airways.
Glycobiology
; 28(10): 786-801, 2018 10 01.
Article
em En
| MEDLINE
| ID: mdl-29924315
ABSTRACT
Human siglecs are a family of 14 sialic acid-binding proteins, most of which are expressed on subsets of immune cells where they regulate immune responses. Siglec-8 is expressed selectively on human allergic inflammatory cells-primarily eosinophils and mast cells-where engagement causes eosinophil apoptosis and inhibits mast cell mediator release. Evidence supports a model in which human eosinophils and mast cells bind to Siglec-8 sialoglycan ligands on inflammatory target tissues to resolve allergic inflammation and limit tissue damage. To identify Siglec-8-binding sialoglycans from human airways, proteins extracted from postmortem human trachea were resolved by size-exclusion chromatography and composite agarose-acrylamide gel electrophoresis, blotted and probed by Siglec-8-Fc blot overlay. Three size classes of Siglec-8 ligands were identified 250 kDa, 600 kDa and 1 MDa, each of which was purified by affinity chromatography using a recombinant pentameric form of Siglec-8. Proteomic mass spectrometry identified all size classes as the proteoglycan aggrecan, a finding validated by immunoblotting. Glycan array studies demonstrated Siglec-8 binding to synthetic glycans with a terminal Neu5Acα2-3(6-sulfo)-Gal determinant, a quantitatively minor terminus on keratan sulfate (KS) chains of aggrecan. Treating human tracheal extracts with sialidase or keratanase eliminated Siglec-8 binding, indicating sialylated KS chains as Siglec-8-binding determinants. Treating human tracheal histological sections with keratanase also completely eliminated the binding of Siglec-8-Fc. Finally, Siglec-8 ligand purified from human trachea extracts induced increased apoptosis of freshly isolated human eosinophils in vitro. We conclude that sialylated KS proteoglycans are endogenous human airway ligands that bind Siglec-8 and may regulate allergic inflammation.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Proteoglicanas
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Ácidos Siálicos
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Traqueia
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Antígenos de Diferenciação de Linfócitos B
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Antígenos CD
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Sulfato de Queratano
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Lectinas
Tipo de estudo:
Prognostic_studies
Limite:
Female
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Humans
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Male
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Middle aged
Idioma:
En
Revista:
Glycobiology
Assunto da revista:
BIOQUIMICA
Ano de publicação:
2018
Tipo de documento:
Article
País de afiliação:
Estados Unidos