Ligand-induced ubiquitination of the platelet-derived growth factor beta-receptor plays a negative regulatory role in its mitogenic signaling.
We have recently reported that the platelet-derived growth factor beta-receptor undergoes polyubiquitination as a consequence of ligand binding and that a mutant beta-receptor lacking the carboxyl-terminal 98 amino acid residues of the receptor (CT98 mutant) does not undergo this posttranslational modification (Mori, S., Heldin, C.-H., and Claesson-Welsh, L. (1992) J. Biol. Chem. 267, 6429-6434). In this paper, we report that a mutant beta-receptor in which the carboxyl-terminally located Tyr-1009 and Tyr-1021, which are potential autophosphorylation sites, were simultaneously changed to phenylalanine residues by site-directed mutagenesis (Y1009F/Y1021F mutant) showed only 15% efficiency in ligand-induced ubiquitination compared with the wild-type receptor. Ligand-stimulated degradation of the receptor-bound ligand, as well as of the receptor itself, was partially impaired in the cells expressing the ubiquitination-deficient receptor mutants (CT98 and Y1009F/Y1021F). Furthermore, the ubiquitination-deficient receptors possessed an amplified mitogenic activity, as judged by a [3H]thymidine incorporation assay. These data suggest that ligand-induced ubiquitination plays a negative regulatory role in mitogenic signaling of the platelet-derived growth factor beta-receptor, possibly by promoting the efficient degradation of the ligand-activated receptor.
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
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Mori
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Heldin
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Claesson-Welsh
D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D017479:Receptors, Platelet-Derived Growth Factor / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D014443:Tyrosine; D014452:Ubiquitins / Q000378:metabolism*
D008024:Ligands; D009838:Oligodeoxyribonucleotides; D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D014452:Ubiquitins; D014443:Tyrosine; D004247:DNA; D017479:Receptors, Platelet-Derived Growth Factor; D013936:Thymidine