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Glycan array screening reveals a candidate ligand for Siglec-8
Bruce S Bochner1, Richard A Alvarez, Padmaja Mehta
1Division of Allergy and Clinical Immunology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA. bbochner@jhmi.edu
The Journal of Biological Chemistry
|November 26, 2004
Summary
Sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8) preferentially binds to a specific sulfated glycan, 6'-sulfo-sLex, with high affinity. This finding clarifies Siglec-8 ligand specificity, crucial for understanding its role in immune cell regulation.
Area of Science:
- Immunology
- Glycobiology
- Biochemistry
Background:
- Sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8) is expressed on human eosinophils, basophils, and mast cells, regulating their function.
- Previous research indicated sialic acid-dependent Siglec-8 binding but lacked specificity and affinity details.
Purpose of the Study:
- To identify specific glycan ligands recognized by Siglec-8.
- To characterize the binding affinity and specificity of Siglec-8 to various sialylated structures.
Main Methods:
- A Siglec-8-Ig chimeric protein was screened against 172 different immobilized glycans.
- Binding was assessed using microplate assays and confirmed with surface plasmon resonance (SPR) and fluorescence-based detection.
Main Results:
- Siglec-8 avidly bound to 6 eal-sulfo-sLex (NeuAcalpha2-3(6-O-sulfo)Galbeta1-4[Fucalpha1-3]GlcNAc).
- No detectable binding occurred with unsulfated sLex or 6-sulfo-sLex.
- SPR analysis revealed a dissociation constant (Kd) of 2.3 microm for Siglec-8 binding to 6 eal-sulfo-sLex.
Conclusions:
- Siglec-8 exhibits high specificity for the 6 eal-sulfo-sLex glycan structure.
- The additional sulfate ester on the galactose 6-hydroxyl is critical for high-affinity Siglec-8 binding.
- This specificity provides insights into Siglec-8's role in immune cell interactions and potential therapeutic targeting.