title: Coupling of Grb2 to Gab1 mediates hepatocyte growth factor-induced high intensity ERK signal required for inhibition of HepG2 hepatoma cell proliferation.
abstract: Activation of the extracellular signal-regulated kinase (ERK) pathway is a key factor in the regulation of cell proliferation by growth factors. Hepatocyte growth factor (HGF)-induced cell cycle arrest in the human hepatocellular carcinoma cell line HepG2 requires strong activation of the ERK pathway. In this study, we investigated the molecular mechanism of the activation. We constructed a chimeric receptor composed of the extracellular domain of the NGF receptor and the cytoplasmic domain of the HGF receptor (c-Met) and introduced a point mutation (N1358H) into the chimeric receptor, which specifically abrogates the direct binding of Grb2 to c-Met. The mutant chimeric receptor failed to mediate the strong activation of ERK, up-regulation of the expression of a Cdk inhibitor p16(INK4a) and inhibition of HepG2 cell proliferation by ligand stimulation. Moreover, the mutant receptor did not induce tyrosine phosphorylation of the docking protein Gab1. Knockdown of Gab1 using siRNA suppressed the HGF-induced strong activation of ERK and inhibition of HepG2 cell proliferation. These results suggest that coupling of Grb2 to Gab1 mediates the HGF-induced strong activation of the ERK pathway, which is required for the inhibition of HepG2 cell proliferation.
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Kondo
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Hirayama
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Sugito
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Michihiro
authors.initials: M
authors.lastname: Shono
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. Electronic address: nkitamur@bio.titech.ac.jp.
authors.forename: Naomi
authors.initials: N
authors.lastname: Kitamura
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D002522:Chlorocebus aethiops; D002999:Clone Cells; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D051380:GRB2 Adaptor Protein / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology* / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D050505:Mutant Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019941:Cyclin-Dependent Kinase Inhibitor p16; C098587:GAB1 protein, human; D051380:GRB2 Adaptor Protein; D050505:Mutant Proteins; D011994:Recombinant Proteins; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D048049:Extracellular Signal-Regulated MAP Kinases