Deletion of the kinase insert sequence of the platelet-derived growth factor beta-receptor affects receptor kinase activity and signal transduction.
A characteristic feature of the platelet-derived growth factor (PDGF) beta-receptor is the presence of an insert sequence in the protein tyrosine kinase domain. A receptor mutant which lacks the entire insert of 98 amino acids was expressed in CHO cells, and its functional characteristics were compared with those of the wild-type receptor. The mutant receptor bound PDGF-BB with high affinity and mediated internalization and degradation of the ligand with efficiency similar to that of the wild-type receptor but did not transduce a mitogenic signal. It was found to display a decreased autophosphorylation after ligand stimulation and had a decreased ability to phosphorylate exogenous substrates; phosphofructokinase was not phosphorylated at all, whereas a peptide substrate was phosphorylated, albeit at a lower rate compared with phosphorylation by the wild-type receptor. Furthermore, the mutant receptor did not mediate actin reorganization but mediated an increase in c-fos expression. The data indicate that the insert in the kinase domain of the PDGF beta-receptor is important for the substrate specificity or catalytic efficiency of the kinase; the deletion of the insert interferes with the transduction of some, but not all, of the signals that arise after activation of the receptor.
Severinsson
L
L
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
Ek
B
B
Mellström
K
K
Claesson-Welsh
L
L
Heldin
C H
CH
D000818:Animals; D002460:Cell Line; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D015870:Gene Expression; D005796:Genes; D005822:Genetic Vectors; D006801:Humans; D007700:Kinetics; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos; D011519:Proto-Oncogenes; D011956:Receptors, Cell Surface / Q000235:genetics*; D017479:Receptors, Platelet-Derived Growth Factor; D015398:Signal Transduction; D014162:Transfection
D004251:DNA Transposable Elements; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D011956:Receptors, Cell Surface; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor