Differential galactosylation of neuronal and haematopoietic signal regulatory protein-alpha determines its cellular binding-specificity.
Signal regulatory protein-alpha (SIRP alpha) is a member of the Ig superfamily selectively expressed by neuronal and myeloid cells. The molecule mediates functional interactions with CD47/integrin-associated protein. Here we provide evidence for the tissue-specific glycosylation of neuronal and haematopoietic SIRP alpha. We demonstrate a major difference in the galactosylation of N-linked glycans isolated from neuronal (i.e. brain-derived) SIRP alpha as compared to myeloid (i.e. spleen-derived) SIRP alpha, with neuronal SIRP alpha almost completely lacking galactose. beta 4-galactosyltransferase assays demonstrated that this is most likely due to a low galactosylation capacity of the brain. In order to investigate the role of galactosylation of SIRP alpha in cellular interactions, soluble recombinant SIRP alpha glycoforms containing galactose (SIRP alpha-Fc) or lacking galactose (SIRP alpha(Delta Gal)-Fc) were produced. Binding studies demonstrated superior binding of SIRP alpha(Delta Gal)-Fc to cerebellar neurons and isolated lymphocytes. In contrast, SIRP alpha-Fc bound relatively strong to macrophages. These data show that the galactosylation of SIRP alpha determines its cellular binding specificity.
Department of Medical Chemistry, Research Institute Immunology and Inflammatory diseases, Vrije Universiteit, Van der Boechorststraat 7, The Netherlands. t.van_den_berg.cell@med.vu.nl
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van den Nieuwenhof
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Renardel de Lavalette
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Diaz
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van Die
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TK
van den Berg
D000818:Animals; D000943:Antigens, Differentiation; D016466:CHO Cells; D006224:Cricetinae; D005690:Galactose / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000096:biosynthesis / Q000235:genetics; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009237:N-Acetyllactosamine Synthase / Q000378:metabolism; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D011134:Polysaccharides / Q000378:metabolism; D051381:Rats; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics
D000943:Antigens, Differentiation; D007141:Immunoglobulin Fc Fragments; D008562:Membrane Glycoproteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D011134:Polysaccharides; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; D009237:N-Acetyllactosamine Synthase; D005690:Galactose