Structural basis for sulfation-dependent self-glycan recognition by the human immune-inhibitory receptor Siglec-8

Proc Natl Acad Sci U S A. 2016 Jul 19;113(29):E4170-9. doi: 10.1073/pnas.1602214113. Epub 2016 Jun 29.


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.

Keywords: NMR spectroscopy; glycan sulfation; glycoimmunology; immune regulation; protein–carbohydrate recognition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD* / chemistry
  • Antigens, CD* / genetics
  • Antigens, CD* / metabolism
  • Antigens, Differentiation, B-Lymphocyte* / chemistry
  • Antigens, Differentiation, B-Lymphocyte* / genetics
  • Antigens, Differentiation, B-Lymphocyte* / metabolism
  • Humans
  • Lectins* / chemistry
  • Lectins* / genetics
  • Lectins* / metabolism
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Nuclear Magnetic Resonance, Biomolecular
  • Polysaccharides / metabolism
  • Protein Domains


  • Antigens, CD
  • Antigens, Differentiation, B-Lymphocyte
  • Lectins
  • Polysaccharides
  • SIGLEC8 protein, human

Associated data

  • PDB/2N7A
  • PDB/2N7B