Ligand-induced dimerization of the platelet-derived growth factor receptor. Monomer-dimer interconversion occurs independent of receptor phosphorylation.
The platelet-derived growth factor (PDGF) receptor is a single membrane-spanning polypeptide of 180,000 daltons with a ligand-stimulatable tyrosine kinase site. We have investigated changes in the structure and association state of the receptor that are induced by ligand binding, but which precede autophosphorylation. Chemical cross-linking of PDGF-bound 32P-labeled receptor and 125I-PDGF-labeled receptor resulted in the generation of a radiolabeled cross-linked complex of 370-390 kDa. This band, as well as the 180-190-kDa PDGF receptor band, were recognized by a PDGF receptor-specific antipeptide antibody. The appearance of the 370-390-kDa band was PDGF-dependent and was seen irrespective of whether the receptor was membrane-bound, solubilized, or highly (approximately 90%) purified. Sedimentation analysis of the 125I-PDGF cross-linked receptor showed that both 180-190- and 370-390-kDa labeled species sedimented as a single peak at about 11.5 S, a position expected of a receptor dimer, demonstrating that the liganded receptor exists essentially as a dimer. In contrast, unliganded receptors sedimented as a single species at 7 S, a position consistent with a monomeric structure. The monomer-dimer interconversion was absolutely ligand-dependent and occurred independent of autophosphorylation. These results demonstrate and intimate correlation between PDGF binding and inter-receptor bond formation, and raise the possibility that the phenomenon may be causally linked to the process of kinase activation.
Bishayee
S
S
Division of Oncology, Children's Hospital of Philadelphia, Pennsylvania 19104.
Majumdar
S
S
Khire
J
J
Das
M
M
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008024:Ligands; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011108:Polymers; D011233:Precipitin Tests; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor; D014407:Tumor Cells, Cultured
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D008024:Ligands; D010982:Platelet-Derived Growth Factor; D011108:Polymers; D011956:Receptors, Cell Surface; D017479:Receptors, Platelet-Derived Growth Factor