title: Epidermal growth factor receptor transactivation mediates tumor necrosis factor-induced hepatocyte replication.
abstract: Tumor necrosis factor (TNF) has multiple biological effects such as participating in inflammation, apoptosis, and cell proliferation, but the mechanisms of its effects on epithelial cell proliferation have not been examined in detail. At the early stages of liver regeneration, TNF functions as a priming agent for hepatocyte replication and increases the sensitivity of hepatocytes to growth factors such as transforming growth factor alpha (TGFalpha); however, the mechanisms by which TNF interacts with growth factors and enhances hepatocyte replication are not known. Using the AML-12 hepatocyte cell line, we show that TNF stimulates proliferation of these cells through transactivation of the epidermal growth factor receptor (EGFR). The transactivation mechanism involves the release of TGFalpha into the medium through activation of the metalloproteinase TNFalpha-converting enzyme (also known as ADAM 17). Binding of the ligand to EGFR initiates a mitogenic cascade through extracellular signal-regulated kinases 1 and 2 and the partial involvement of protein kinase B. TNF-induced release of TGFalpha and activation of EGFR signaling were inhibited by TNFalpha protease inhibitor-1, an agent that interferes with TNFalpha-converting enzyme activity. We suggest that TNF-induced transactivation of EGFR may provide an early signal for the entry of hepatocytes into the cell cycle and may integrate proliferative and survival pathways at the start of liver regeneration.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309, USA.
authors.forename: Gretchen M
authors.initials: GM
authors.lastname: Argast
authors.forename: Jean S
authors.initials: JS
authors.lastname: Campbell
authors.forename: John T
authors.initials: JT
authors.lastname: Brooling
authors.forename: Nelson
authors.initials: N
authors.lastname: Fausto
mesh_terms: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D000818:Animals; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002021:Buffers; D002455:Cell Division; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004396:Coloring Agents / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008099:Liver / Q000502:physiology; D008666:Metalloendopeptidases / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D012038:Regeneration; D015398:Signal Transduction; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D001973:Bromodeoxyuridine; D002021:Buffers; D004396:Coloring Agents; D016895:Culture Media, Serum-Free; D004247:DNA; D066246:ErbB Receptors; D008024:Ligands; D008666:Metalloendopeptidases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D013936:Thymidine; D014409:Tumor Necrosis Factor-alpha; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse