Characterization of two monoclonal antibodies reactive with the external domain of the platelet-derived growth factor receptor.
Two monoclonal antibodies against the receptor for platelet-derived growth factor (PDGF) were obtained by immunizing mice with pure PDGF receptor preparations derived from porcine uterus. The antibodies, denoted PDGFR-B1 and PDGFR-B2, both bound to the external domain of the receptor, as demonstrated by indirect immunofluorescence and binding of 125I-labeled antibodies to intact human fibroblasts. Both antibodies precipitated pure 175-kDa 32P-labeled autophosphorylated porcine PDGF receptor as well as a Mr 175,000 glycoprotein from metabolically labeled cells. The monoclonal antibodies did not inhibit binding of 125I-PDGF to human fibroblasts and did not stimulate these cells to undergo mitosis. Both antibodies induced clustering and down-regulation of their antigen. However, this resulted in only a partial loss of cell surface binding sites for PDGF itself, consistent with the conclusion that the monoclonals recognized only one of two or several receptors for PDGF. Clustering and down-regulation were not seen when the cells were incubated with monovalent Fab' fragments of the PDGFR-B2 antibody. The antibodies also stimulated autophosphorylation of pure PDGF receptor, and PDGFR-B2 was shown to stimulate phosphorylation of phosphofructokinase, an exogenous substrate for the PDGF receptor kinase. High concentrations of PDGFR-B2 antibody, or Fab' fragments thereof, failed to enhance the PDGF receptor kinase activity, compatible with the possibility that dimerization was of importance in the antibody-stimulated kinase activity of purified PDGF receptors.
Rönnstrand
L
L
Ludwig Institute for Cancer Research, Uppsala, Sweden.
Terracio
L
L
Claesson-Welsh
L
L
Heldin
C H
CH
Rubin
K
K
D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000032:analysis*; D005260:Female; D007700:Kinetics; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000276:immunology* / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor; D013552:Swine; D014599:Uterus / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D000939:Epitopes; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D017479:Receptors, Platelet-Derived Growth Factor