Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 279, Issue 33, Pages 34530-34536Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M405703200
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- NCI NIH HHS [CA 23226] Funding Source: Medline
- NIEHS NIH HHS [T32 ES 07032-23] Funding Source: Medline
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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.
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