Mechanism of pathogen recognition by human dectin-2.
J Biol Chem
; 292(32): 13402-13414, 2017 08 11.
Article
em En
| MEDLINE
| ID: mdl-28652405
ABSTRACT
Dectin-2, a C-type lectin on macrophages and other cells of the innate immune system, functions in response to pathogens, particularly fungi. The carbohydrate-recognition domain (CRD) in dectin-2 is linked to a transmembrane sequence that interacts with the common Fc receptor γ subunit to initiate immune signaling. The molecular mechanism by which dectin-2 selectively binds to pathogens has been investigated by characterizing the CRD expressed in a bacterial system. Competition binding studies indicated that the CRD binds to monosaccharides with modest affinity and that affinity was greatly enhanced for mannose-linked α1-2 or α1-4 to a second mannose residue. Glycan array analysis confirmed selective binding of the CRD to glycans that contain Manα1-2Man epitopes. Crystals of the CRD in complex with a mammalian-type high-mannose Man9GlcNAc2 oligosaccharide exhibited interaction with Manα1-2Man on two different termini of the glycan, with the reducing-end mannose residue ligated to Ca2+ in a primary binding site and the nonreducing terminal mannose residue occupying an adjacent secondary site. Comparison of the binding sites in DC-SIGN and langerin, two other pathogen-binding receptors of the innate immune system, revealed why these two binding sites accommodate only terminal Manα1-2Man structures, whereas dectin-2 can bind Manα1-2Man in internal positions in mannans and other polysaccharides. The specificity and geometry of the dectin-2-binding site provide the molecular mechanism for binding of dectin-2 to fungal mannans and also to bacterial lipopolysaccharides, capsular polysaccharides, and lipoarabinomannans that contain the Manα1-2Man disaccharide unit.
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Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Oligossacarídeos
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Polissacarídeos
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Modelos Moleculares
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Lectinas Tipo C
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Dissacarídeos
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Imunidade Inata
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Manose
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2017
Tipo de documento:
Article