title: Protein-tyrosine phosphatase 1B (PTP1B) deficiency confers resistance to transforming growth factor-β (TGF-β)-induced suppressor effects in hepatocytes.
abstract: Transforming growth factor-β (TGF-β) plays a dual role in hepatocytes, mediating both tumor suppressor and promoter effects. The suppressor effects of the cytokine can be negatively regulated by activation of survival signals, mostly dependent on tyrosine kinase activity. The aim of our work was to study the role of the protein-tyrosine phosphatase 1B (PTP1B) on the cellular responses to TGF-β, using for this purpose immortalized neonatal hepatocytes isolated from both PTP1B(+/+) and PTP1B(-/-) mice. We have found that PTP1B deficiency conferred resistance to TGF-β suppressor effects, such as apoptosis and growth inhibition, correlating with lower Smad2/Smad3 activation. Both responses were recovered in the presence of the general tyrosine kinase inhibitor genistein. PTP1B(-/-) cells showed elevated NF-κB activation in response to TGF-β. Knockdown of the NF-κB p65 subunit increased cell response in terms of Smads phosphorylation and apoptosis. Interestingly, these effects were accompanied by inhibition of Smad7 up-regulation. In addition, lack of PTP1B promoted an altered NADPH oxidase (NOX) expression pattern in response to TGF-β, strongly increasing the NOX1/NOX4 ratio, which was reverted by genistein and p65 knockdown. Importantly, NOX1 knockdown inhibited nuclear translocation of p65, promoted Smad phosphorylation, and decreased Smad7 levels. In summary, our results suggest that PTP1B deficiency confers resistance to TGF-β through Smad inhibition, an effect that is mediated by NOX1-dependent NF-κB activation, which in turn, increases the level of the Smad inhibitor Smad7 and participates in a positive feedback loop on NOX1 up-regulation.
authors.affiliation: Biological Clues of the Invasive and Metastatic Phenotype Group, Bellvitge Biomedical Research Institut (IDIBELL), L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors.forename: Conrad
authors.initials: C
authors.lastname: Ortiz
authors.forename: Laia
authors.initials: L
authors.lastname: Caja
authors.forename: Esther
authors.initials: E
authors.lastname: Bertran
authors.forename: Águeda
authors.initials: Á
authors.lastname: Gonzalez-Rodriguez
authors.forename: Ángela M
authors.initials: ÁM
authors.lastname: Valverde
authors.forename: Isabel
authors.initials: I
authors.lastname: Fabregat
authors.forename: Patricia
authors.initials: P
authors.lastname: Sancho
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004351:Drug Resistance / Q000235:genetics*; D019833:Genistein / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000074624:NADPH Oxidase 1; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000172:deficiency / Q000235:genetics*; D034622:RNA Interference; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D051906:Smad7 Protein / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D047428:Protein Kinase Inhibitors; D051899:Smad2 Protein; D051900:Smad3 Protein; D051906:Smad7 Protein; D051996:Transcription Factor RelA; D053773:Transforming Growth Factor beta1; D019833:Genistein; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; C000614711:NOX1 protein, mouse; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; C516609:Ptpn1 protein, mouse