Abstract
The E-cadherin-based adherens junction (AJ) is essential for organogenesis of epithelial tissues including the liver, although the regulatory mechanism of AJ formation during development remains unknown. Using a primary culture system of fetal hepatocytes in which oncostatin M (OSM) induces differentiation, we show here that OSM induces AJ formation by altering the subcellular localization of AJ components including E-cadherin and catenins. By retroviral expression of dominant-negative forms of signaling molecules, Ras was shown to be required for the OSM-induced AJ formation. Fetal hepatocytes derived from K-Ras knockout (K-Ras-/-) mice failed to form AJs in response to OSM, whereas AJ formation was induced normally by OSM in mutant hepatocytes lacking both H-Ras and N-Ras. Moreover, the defective phenotype of K-Ras-/- hepatocytes was restored by expression of K-Ras, but not by H-Ras and N-Ras. Finally, pull-down assays using the Ras-binding domain of Raf1 demonstrated that OSM directly activates K-Ras in fetal hepatocytes. These results indicate that K-Ras specifically mediates cytokine signaling for formation of AJs during liver development.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adherens Junctions / drug effects
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Adherens Junctions / metabolism*
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Animals
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Cadherins / metabolism*
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Cell Differentiation / drug effects
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Cells, Cultured / drug effects
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Cytoskeletal Proteins / metabolism
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Dexamethasone / pharmacology
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Enzyme Activation
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Fetal Proteins / physiology*
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Genes, ras
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Genetic Complementation Test
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Hepatocytes / drug effects
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Hepatocytes / ultrastructure*
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Liver / embryology*
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Membrane Proteins / analysis
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Mice
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Mice, Knockout
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Oncostatin M
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Peptides / pharmacology
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Phenotype
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Phosphoproteins / analysis
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Protein Structure, Tertiary
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Proto-Oncogene Proteins c-raf / chemistry
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Proto-Oncogene Proteins c-raf / metabolism
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Proto-Oncogene Proteins p21(ras) / physiology*
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Recombinant Fusion Proteins / physiology
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Signal Transduction
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Trans-Activators*
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Zonula Occludens-1 Protein
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beta Catenin
Substances
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CTNNB1 protein, mouse
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Cadherins
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Cytoskeletal Proteins
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Fetal Proteins
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Membrane Proteins
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Osm protein, mouse
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Peptides
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Phosphoproteins
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Recombinant Fusion Proteins
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Tjp1 protein, mouse
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Trans-Activators
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Zonula Occludens-1 Protein
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beta Catenin
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Oncostatin M
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Dexamethasone
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Proto-Oncogene Proteins c-raf
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Proto-Oncogene Proteins p21(ras)