title: A B-type PDGF receptor lacking most of the intracellular domain escapes degradation after ligand binding.
abstract: The characteristics of the human B-type platelet-derived-growth-factor (PDGF) receptor expressed in Chinese hamster ovary (CHO) cells, were compared with those of a mutant receptor lacking all but 19 amino acids of the intracellular domain. The transfected wild-type receptor was synthesized as a 160-kDa precursor that was processed to 190 kDa. Each CHO cell expressed 30,000-100,000 receptors which bound PDGF-BB with a Kd of about 0.5 nM. Analysis of PDGF-AB binding yielded non-linear Scatchard plots; the major part of the binding sites had a Kd of 6 nM. PDGF-AA was not bound. The receptors expressed in CHO cells were down-regulated after binding of PDGF-BB, and mediated degradation of 125I-PDGF-BB with similar efficiency as PDGF-B-type receptors in human fibroblasts. The transfected receptor also transduced a mitogenic signal. The mutant receptor was synthesized as a 90-kDa precursor and was processed to 120 kDa with a slightly faster rate than the wild-type receptor. Cells expressing the mutant receptor generally had around 10(6) ligand-binding sites/cell, with a Kd for binding of PDGF-BB of 3 nM. The mutant receptor, which did not transduce a mitogenic response, mediated degradation of 125I-PDGF-BB, albeit less efficiently compared to the wild-type receptor. In contrast to the wild-type receptor, it was down-regulated only to a limited extent and not degraded in response to ligand binding. These findings indicate a role for the intracellular part of the receptor, not only in mitogenic signaling, but also in receptor internalization and intracellular routing.
authors.affiliation: Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Severinsson
authors.forename: L
authors.initials: L
authors.lastname: Claesson-Welsh
authors.forename: C H
authors.initials: CH
authors.lastname: Heldin
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D009154:Mutation; D010053:Ovary / Q000187:drug effects / Q000378:metabolism; D010957:Plasmids; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology; D011498:Protein Precursors / Q000096:biosynthesis*; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D017479:Receptors, Platelet-Derived Growth Factor; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: D010982:Platelet-Derived Growth Factor; D011498:Protein Precursors; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D017479:Receptors, Platelet-Derived Growth Factor