IFN-gamma gene expression in epithelial trophectoderm cells is linked to downregulation of the p44/p42 MAP kinase pathway.
We previously stated that interferon-gamma (IFN-gamma) is highly expressed in a transient and developmentally regulated manner by the trophectoderm of the pig blastocyst, which represents a monolayer of polarized epithelial cells, during early pregnancy. In order to study the molecular mechanisms of this atypical IFN-gamma gene expression, we established the pig trophectoderm cell line TBA B4-3. These cells develop a polarized phenotype with high transepithelial electrical resistance (TER) when grown on a microporous membrane. We previously showed that treatment of polarized TBA B4-3 cells with the strong protein kinase C (PKC) agonist phorbol 12-myristate-13-acetate (PMA) induced 3-4 days later a transient IFN-gamma mRNA expression and apical IFN-gamma protein secretion. In the present paper, we report that after PMA removal, a transient phase of p44/p42 mitogen-activated protein (MAP) kinase activation occurs, followed by a strong downregulation preceding the phase of IFN-gamma expression. Surprisingly, we found that inhibition of this surge of p44/p42 MAP kinase activation with MEK inhibitors (U0126 and PD98059) triggers earlier IFN-gamma mRNA and protein expression, correlated with earlier TER rising and restoration of epithelial phenotype. These results indicate that in the TBA B4-3 cell system, activation of this signaling pathway has a negative effect on IFN-gamma gene expression. These observations reinforce the hypothesis of a link between establishment of cell polarity and induction of IFN-gamma that could be mediated by signaling from intercellular junctions.
Unité de Virologie et Immunologie Moléculaires, Institut National de la Recherche Agronomique, Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France.
Paulo
P
Marcelo
François
F
Lefèvre
D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000378:metabolism*; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D016764:Cell Polarity / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D011247:Pregnancy; D013552:Swine / Q000196:embryology / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002070:Butadienes; D005419:Flavonoids; D009570:Nitriles; C113580:U 0126; D007371:Interferon-gamma; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one