Autoinhibition of the platelet-derived growth factor beta-receptor tyrosine kinase by its C-terminal tail.
In this report, we investigated the role of the C-terminal tail of the platelet-derived growth factor (PDGF) beta-receptor in the control of the receptor kinase activity. Using a panel of PDGF beta-receptor mutants with progressive C-terminal truncations, we observed that deletion of the last 46 residues, which contain a proline- and glutamic acid-rich motif, increased the autoactivation velocity in vitro and the V(max) of the phosphotransfer reaction, in the absence of ligand, as compared with wild-type receptors. By contrast, the kinase activity of mutant and wild-type receptors that were pre-activated by treatment with PDGF was comparable. Using a conformation-sensitive antibody, we found that truncated receptors presented an active conformation even in the absence of PDGF. A soluble peptide containing the Pro/Glu-rich motif specifically inhibited the PDGF beta-receptor kinase activity. Whereas deletion of this motif was not enough to confer ligand-independent transforming ability to the receptor, it dramatically enhanced the effect of the weakly activating D850N mutation in a focus formation assay. These findings indicate that allosteric inhibition of the PDGF beta-receptor by its C-terminal tail is one of the mechanisms involved in keeping the receptor inactive in the absence of ligand.
Ludwig Institute for Cancer Research, S-75124 Uppsala, Sweden.
Federica
F
Chiara
Subal
S
Bishayee
Carl-Henrik
CH
Heldin
Jean-Baptiste
JB
Demoulin
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D004305:Dose-Response Relationship, Drug; D017353:Gene Deletion; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014162:Transfection
D008024:Ligands; D010455:Peptides; D020797:Receptor, Platelet-Derived Growth Factor beta