title: The kinase-inactive PDGF beta-receptor mediates activation of the MAP kinase cascade via the endogenous PDGF alpha-receptor in HepG2 cells.
abstract: The PDGF beta-receptor in which the active-site lysine in the kinase domain has been mutated to arginine (K634R) tacks intrinsic kinase activity. When expressed in HepG2 cells, the kinase-inactive PDGF beta-receptor was tyrosine phosphorylated in response to PDGF-BB. Previously, HepG2 cells were thought to be devoid of PDGF alpha-receptor primarily due to lack of specific antibody which precluded detection of the PDGF alpha-receptor. In fact, these cells express low levels of PDGF alpha-receptor. In HepG2 cells that express the kinase-inactive PDGF beta-receptor, PDGF-BB activates the PDGF alpha-receptors to trans phosphorylate the kinase-inactive PDGF beta-receptor in an intermolecular fashion. As a result, stimulation of HepG2 cells that express the kinase-inactive receptor leads to activation of serine/threonine kinases of the MAP kinase cascade which include RAF-1, MEK-1 and p42 MAP kinase. In contrast, the kinase-inactive receptor does not activate any signaling pathways when it is expressed in PC12 cells which do not express the endogenous PDGF alpha-receptor. Thus, the kinase-inactive K634R PDGF beta-receptor is able to enhance PDGF-BB signaling in HepG2 cells that express the PDGF alpha-receptor.
authors.affiliation: Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
authors.forename: R R
authors.initials: RR
authors.lastname: Vaillancourt
authors.forename: A M
authors.initials: AM
authors.lastname: Gardner
authors.forename: A
authors.initials: A
authors.lastname: Kazlauskas
authors.forename: G L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000077214:Becaplermin; D001665:Binding Sites; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D051379:Mice; D008969:Molecular Sequence Data; D016716:PC12 Cells / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D018076:DNA, Complementary; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011993:Recombinant Fusion Proteins; D000077214:Becaplermin; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases