title: Ligand stimulation reduces platelet-derived growth factor beta-receptor susceptibility to tyrosine dephosphorylation.
abstract: Ligand binding to the platelet-derived growth factor (PDGF) beta-receptor leads to increased receptor tyrosine phosphorylation as a consequence of dimerization-induced activation of the intrinsic receptor tyrosine kinase activity. In this study we asked whether ligand-stimulated PDGF beta-receptor tyrosine phosphorylation, to some extent, also involved reduced susceptibility to tyrosine dephosphorylation. To investigate this possibility we compared the sensitivity of ligand-stimulated and non-stimulated forms of tyrosine-phosphorylated PDGF beta-receptors to dephosphorylation using various preparations containing protein-tyrosine phosphatase activity. Ligand-stimulated or unstimulated tyrosine-phosphorylated receptors were obtained after incubation of cells with pervanadate only or pervanadate, together with PDGF-BB, respectively. Dephosphorylation of receptors immobilized on wheat germ agglutinin-Sepharose, as well as of receptors in intact cell membranes, was investigated under conditions when rephosphorylation did not occur. As compared with unstimulated receptors the ligand-stimulated PDGF beta-receptors showed about 10-fold reduced sensitivity to dephosphorylation by cell membranes, a recombinant form of the catalytic domain of density-enhanced phosphatase-1, or recombinant protein-tyrosine phosphatase 1B. We conclude that ligand-stimulated forms of the PDGF beta-receptor display a reduced susceptibility to dephosphorylation. Our findings suggest a novel mechanism whereby ligand stimulation of PDGF beta-receptor, and possibly other tyrosine kinase receptors, leads to a net increase in receptor tyrosine phosphorylation.
authors.affiliation: Ludwig Institute for Cancer Research, Box 595, S-751 24 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Shimizu
authors.forename: C
authors.initials: C
authors.lastname: Persson
authors.forename: C H
authors.initials: CH
authors.lastname: Heldin
authors.forename: A
authors.initials: A
authors.lastname: Ostman
mesh_terms: D000373:Agglutinins / Q000378:metabolism; D000818:Animals; D020134:Catalytic Domain; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D019281:Dimerization; D004730:Endothelium, Vascular / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008024:Ligands; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D054645:Protein Phosphatase 1; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012685:Sepharose / Q000737:chemistry / Q000378:metabolism; D013552:Swine; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000373:Agglutinins; D004791:Enzyme Inhibitors; D008024:Ligands; D011994:Recombinant Proteins; C076715:pervanadate; D014638:Vanadates; D014443:Tyrosine; D012685:Sepharose; D020797:Receptor, Platelet-Derived Growth Factor beta; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases