Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred glycan ligand.
Mouse sialic acid-binding immunoglobulin-like lectin F (Siglec-F) is an eosinophil surface receptor, which contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic domain, implicating it as a regulator of cell signaling as documented for other siglecs. Here, we show that the sialoside sequence 6'-sulfo-sLe(X) (Neu5Acalpha2-3[6-SO4] Galbeta1-4[Fucalpha1-3]GlcNAc) is a preferred ligand for Siglec-F. In glycan array analysis of 172 glycans, recombinant Siglec-F-Fc chimeras bound with the highest avidity to 6'-sulfo-sLe X. Secondary analysis showed that related structures, sialyl-Lewis X (sLe X) and 6-sulfo-sLe X containing 6-GlcNAc-SO4 showed much lower binding avidity, indicating significant contribution of 6-Gal-SO4 on Siglec-F binding to 6'-sulfo-sLe x. The lectin activity of Siglec-F on mouse eosinophils was "masked" by endogenous cis ligands and could be unmasked by treatment with sialidase. Unmasked Siglec-F mediated mouse eosinophil binding and adhesion to multivalent 6'-sulfo-sLe X structure, and these interactions were inhibited by anti-Siglec-F monoclonal antibody (mAb). Although there is no clear-cut human ortholog of Siglec-F, Siglec-8 is encoded by a paralogous gene that is expressed selectively by human eosinophils and has recently been found to recognize 6'-sulfo-sLe X. These observations suggest that mouse Siglec-F and human Siglec-8 have undergone functional convergence during evolution and implicate a role for the interaction of these siglecs with their preferred 6'-sulfo-sLe X ligand in eosinophil biology.
Department of Molecular Biology, The Scripps Research Institute, San Diego, CA 92037, USA.
Hiroaki
H
Tateno
Paul R
PR
Crocker
James C
JC
Paulson
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015214:Antigens, Differentiation, Myelomonocytic / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016466:CHO Cells; D006224:Cricetinae; D004804:Eosinophils / Q000378:metabolism*; D006801:Humans; D037102:Lectins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016256:Lewis X Antigen / Q000031:analogs & derivatives; D008024:Ligands; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D009439:Neuraminidase / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D000080506:Sialyl Lewis X Antigen / Q000031:analogs & derivatives
C086949:6'-sulfated sialyl Lewis x; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D015214:Antigens, Differentiation, Myelomonocytic; D037102:Lectins; D016256:Lewis X Antigen; D008024:Ligands; D009844:Oligosaccharides; D011134:Polysaccharides; C403967:SIGLEC8 protein, human; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D000080506:Sialyl Lewis X Antigen; C443130:Siglecf protein, mouse; D009439:Neuraminidase