Journal of Biological Chemistry
Volume 288, Issue 37, 13 September 2013, Pages 26533-26545
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Glycobiology and Extracellular Matrices
Galactose 6-O-Sulfotransferases Are Not Required for the Generation of Siglec-F Ligands in Leukocytes or Lung Tissue*

https://doi.org/10.1074/jbc.M113.485409Get rights and content
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Eosinophil accumulation is a characteristic feature of the immune response to parasitic worms and allergens. The cell surface carbohydrate-binding receptor Siglec-F is highly expressed on eosinophils and negatively regulates their accumulation during inflammation. Although endogenous ligands for Siglec-F have yet to be biochemically defined, binding studies using glycan arrays have implicated galactose 6-O-sulfate (Gal6S) as a partial recognition determinant for this receptor. Only two sulfotransferases are known to generate Gal6S, namely keratan sulfate galactose 6-O-sulfotransferase (KSGal6ST) and chondroitin 6-O-sulfotransferase 1 (C6ST-1). Here we use mice deficient in both KSGal6ST and C6ST-1 to determine whether these sulfotransferases are required for the generation of endogenous Siglec-F ligands. First, we characterize ligand expression on leukocyte populations and find that ligands are predominantly expressed on cell types also expressing Siglec-F, namely eosinophils, neutrophils, and alveolar macrophages. We also detect Siglec-F ligand activity in bronchoalveolar lavage fluid fractions containing polymeric secreted mucins, including MUC5B. Consistent with these observations, ligands in the lung increase dramatically during infection with the parasitic nematode, Nippostrongylus brasiliensis, which is known to induce eosinophil accumulation and mucus production. Surprisingly, Gal6S is undetectable in sialylated glycans from eosinophils and BAL fluid analyzed by mass spectrometry. Furthermore, none of the ligands we describe are diminished in mice lacking KSGal6ST and C6ST-1, indicating that neither of the known galactose 6-O-sulfotransferases is required for ligand synthesis. These results establish that ligands for Siglec-F are present on several cell types that are relevant during allergic lung inflammation and argue against the widely held view that Gal6S is critical for glycan recognition by this receptor.

Background: The cell surface lectin Siglec-F is thought to preferentially recognize ligands modified with galactose 6-O-sulfate.

Results: Siglec-F ligands are still present in leukocytes and lung tissue from mice lacking galactose 6-O-sulfotransferases.

Conclusion: Ligands are restricted to specific cell types, but galactose 6-O-sulfotransferases are not required for ligand binding.

Significance: This study refines our understanding of the biological ligands for Siglec-F.

Eosinophils
Lectin
Lung
Mucins
Sulfotransferase
Galactose-6-O-Sulfate
Siglec-F

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*

This work was supported, in whole or in part, by National Institutes of Health Grants GM-23547 and GM-57411 (to S. D. R.), Academia Sinica and Taiwan National Science Council Grant 99-2311-B-001-021-MY3 (to K. H. K.), the Taiwan National Core Facility Program for Biotechnology Grants NSC100-2325-B-001-029 and NSC101-2319-B-001-003 to the Core Facilities for Protein Structural Analysis at Academia Sinica, and Wellcome Trust Senior Fellowship WT081882 (to P. R. C.).