title: Developmentally regulated expression of a 78 kDa erythroblast membrane glycoprotein immunologically related to the platelet thrombospondin receptor.
abstract: We have previously described a monoclonal antibody (FA6-152), obtained by immunizing mice with fetal human erythrocytes [Edelman, Vinci, Villeval, Vainchenker, Henri, Miglierina, Rouger, Reviron, Breton-Gorius, Sureau & Edelman (1986) Blood 67, 56-63]. The antibody labelled fetal, but not adult, erythrocytes and bound to both fetal and adult platelets and monocytes. In the present study we have characterized the antigen recognized by FA6-152 on human platelets and on cells of the erythroid lineage at different stages of maturation. FA6-152 precipitated a chymotrypsin-resistant 88 kDa sialoglycoprotein from both iodinated and periodate/NaB3H4-surface-labelled platelets which corresponds to glycoprotein IV, the platelet thrombospondin (TSP) receptor. After neuraminidase treatment, a shift of the apparent molecular mass from 88 kDa to 85 kDa was observed. Scatchard analysis revealed that 125I-FA6-152 bound saturably with high affinity to a single class of platelet binding sites (Kd 6.4 +/- 0.6 nM). The number of FA6-152 IgG molecules bound per platelet was 25,400 +/- 8,800 (n = 4) and did not change upon thrombin activation of platelets. At low doses of alpha-thrombin (0.025 unit), FA6-152 inhibited platelet aggregation as well as endogenous TSP binding to the platelet surface. Immunofluorescence labelling of bone-marrow cells and of cultures in vitro of burst-forming units-erythroid (BFU-E) and colony-forming units-erythroid (CFU-E) revealed that that FA6-152 antigen is a very early marker of erythroid differentiation and that its expression declines during maturation. Immunochemical identification of the FA6-152 antigen on fetal erythroblasts and fetal mature erythrocytes revealed a 78 kDa glycoprotein migrating just in front of the glycophorin A dimer. The antigen, which was absent from adult mature erythrocytes, was also detected in human erythroleukaemic (HEL) cells where FA6-152 precipitated two bands of molecular mass 85 and 88 kDa. Our data establish the existence of a previously unidentified 78 kDa erythroblast cell-surface glycoprotein whose expression is developmentally regulated during erythroid differentiation and which is immunologically related to the 88 kDa platelet TSP receptor.
authors: INSERM U91/CNRS UA 607, Hôpital Henri Mondor, Créteil, France.
authors: N
authors: N
authors: Kieffer
authors: A
authors: A
authors: Bettaieb
authors: C
authors: C
authors: Legrand
authors: L
authors: L
authors: Coulombel
authors: W
authors: W
authors: Vainchenker
authors: L
authors: L
authors: Edelman
authors: J
authors: J
authors: Breton-Gorius
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000032:analysis*; D001792:Blood Platelets / Q000276:immunology*; D018955:CD36 Antigens; D002454:Cell Differentiation; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D008970:Molecular Weight; D010974:Platelet Aggregation; D016024:Receptors, Cytoadhesin / Q000032:analysis*
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens; D018955:CD36 Antigens; D006023:Glycoproteins; D016024:Receptors, Cytoadhesin