title: Functional importance of platelet-derived growth factor (PDGF) receptor extracellular immunoglobulin-like domains. Identification of PDGF binding site and neutralizing monoclonal antibodies.
abstract: The biological effects of platelet-derived growth factor (PDGF) are mediated by alpha- and beta-PDGF receptors (PDGFR), which have an intracellular tyrosine kinase domain and an extracellular region comprising five immunoglobulin-like domains (D1-D5). Using deletion mutagenesis we mapped the PDGF binding site in each PDGFR to the D2-D3 region. In the case of alpha-PDGFR, 125I-PDGF AA and 125I-PDGF BB bound to the full-length extracellular domain, D1-D5, and D2-D3 with equal affinity (Kd = 0.21-0.42 nM). Identical results were obtained for 125I-PDGF BB binding to beta-PDGFR mutants D1-D5 and D2-D3, establishing that D1, D4, and D5 do not contribute to PDGF binding. Monoclonal antibodies (mAb) directed against individual PDGFR Ig-like domains were used to extend these observations. The anti-D1 mAb 1E10E2 and anti-D5 mAb 2D4G10 had no effect on alpha- or beta-PDGFR function, respectively. In contrast, mAb 2H7C5 and 2A1E2 directed against D2 of the alpha- and beta-receptor, respectively, blocked PDGF binding, receptor autophosphorylation and mitogenic signaling with IC50 values of 0.1-3.0 nM. An anti-D4 mAb 1C7D5 blocked beta-receptor autophosphorylation and signaling without inhibiting PDGF binding consistent with the observation that D4 is essential for PDGFR dimerization (Omura, T., Heldin, C.-H., and Ostman, A. (1997) J. Biol. Chem. 272, 12676-12682). mAbs identified here act as potent PDGFR antagonists that can be used as research tools and potentially as therapeutic agents for the treatment of diseases involving unwanted PDGFR signaling.
authors.affiliation: COR Therapeutics Inc., South San Francisco, California 94080, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Lokker
authors.forename: J P
authors.initials: JP
authors.lastname: O'Hare
authors.forename: A
authors.initials: A
authors.lastname: Barsoumian
authors.forename: J E
authors.initials: JE
authors.lastname: Tomlinson
authors.forename: V
authors.initials: V
authors.lastname: Ramakrishnan
authors.forename: L J
authors.initials: LJ
authors.lastname: Fretto
authors.forename: N A
authors.initials: NA
authors.lastname: Giese
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001665:Binding Sites / Q000235:genetics; D016466:CHO Cells; D006224:Cricetinae; D019281:Dimerization; D007136:Immunoglobulins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010766:Phosphorylation; D017479:Receptors, Platelet-Derived Growth Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000911:Antibodies, Monoclonal; D007136:Immunoglobulins; D017479:Receptors, Platelet-Derived Growth Factor