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.
van den Nieuwenhof
I M
IM
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
Renardel de Lavalette
C
C
Diaz
N
N
van Die
I
I
van den Berg
T K
TK
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