title: Involvement of EGF receptor and c-Src in the survival signals induced by TGF-beta1 in hepatocytes.
abstract: Transforming growth factor beta1 (TGF-beta1) belongs to a family of polypeptide factors, whose cytostatic and apoptotic functions help restrain the growth of mammalian cells. Although solid data established the role of TGF-beta's as suppressor factors in tumorigenic processes, in the context of an advanced stage of disease, TGF-beta's could also play a pro-oncogenic role. We have previously shown that TGF-beta1 induces both pro- and anti-apoptotic signals in foetal rat hepatocytes. In this work, we have focused on its anti-apoptotic mechanism. We show that TGF-beta1 activates the epidermal growth factor receptor (EGFR) and phosphorylates c-Src. EGFR is required for Akt activation. Blocking EGFR signalling amplifies the apoptotic response to TGF-beta1. TGF-beta1 induced a rapid activation of the tumour necrosis factor-alpha-converting enzyme (TACE/ADAM (a disintegrin and metalloprotease) 17). Inhibitors of TACE considerably attenuated Akt activation, which suggests that TGF-beta1 activates EGF signalling in hepatocytes by promoting shedding of EGF-like ligands. The activation of c-Src by TGF-beta1 is EGFR dependent and is required for full Akt phosphorylation and cell survival. Inhibition of EGFR does not block the epithelial-mesenchymal transition (EMT) induced by TGF-beta1 in hepatocytes, which indicates that activation of EGFR plays an essential role in impairing apoptosis, but it is dispensable for the EMT process.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid 28040, Spain.
authors.forename: Miguel M
authors.initials: MM
authors.lastname: Murillo
authors.forename: Gaelle
authors.initials: G
authors.lastname: del Castillo
authors.forename: Aránzazu
authors.initials: A
authors.lastname: Sánchez
authors.forename: Margarita
authors.initials: M
authors.lastname: Fernández
authors.forename: Isabel
authors.initials: I
authors.lastname: Fabregat
mesh_terms: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D058544:Class Ib Phosphatidylinositol 3-Kinase; D004847:Epithelial Cells / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000196:embryology; D008648:Mesoderm / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D053148:Caspase 3; D020169:Caspases; D058544:Class Ib Phosphatidylinositol 3-Kinase; D066246:ErbB Receptors; D007527:Isoenzymes; D008666:Metalloendopeptidases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D016392:Proto-Oncogene Proteins pp60(c-src); D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; C508962:Tgfb1 protein, rat; C546765:Pik3cg protein, rat; C494920:Akt1 protein, rat; C505410:Casp3 protein, rat; C000606464:Adam17 protein, rat