MEK Is a Key Modulator for TLR5-induced Interleukin-8 and MIP3α Gene Expression in Non-transformed Human Colonic Epithelial Cells
| Autor: | Charalabos Pothoulakis, Sang Hoon Rhee, Andrew C. Keates, Mary P. Moyer |
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| Rok vydání: | 2004 |
| Předmět: |
Colon
p38 mitogen-activated protein kinases MAP Kinase Kinase 1 Receptors Cell Surface Biochemistry Humans Interleukin 8 Intestinal Mucosa Molecular Biology Mitogen-Activated Protein Kinase Kinases TNF Receptor-Associated Factor 6 Chemokine CCL20 Membrane Glycoproteins biology Kinase Interleukin-8 Toll-Like Receptors NF-kappa B Proteins Interleukin Cell Biology Transfection Macrophage Inflammatory Proteins Molecular biology Cell biology Toll-Like Receptor 5 IκBα Gene Expression Regulation TLR5 Chemokines CC biology.protein Mitogen-Activated Protein Kinases Flagellin Signal Transduction |
| Zdroj: | Journal of Biological Chemistry. 279:25179-25188 |
| ISSN: | 0021-9258 |
| Popis: | Flagellin, a specific ligand for Toll-like receptor 5 (TLR5), is a molecular pattern associated with several bacterial species. Recently, TLR signaling has been intensively studied. However, TLR5-associated signaling in non-transformed colonocytes has not been investigated. Here we studied the expression of cytokines induced by flagellin in non-transformed human colonic NCM460 cells and the signaling mechanisms mediating these responses. Cytokine expression array experiments showed that exposure of the cells to flagellin (100 ng/ml) for 12 h increased the expression of interleukin (IL)-8 and macrophage-inflammatory protein 3alpha (MIP3alpha) in a TLR5-specific manner. Flagellin also activated MAP kinases (ERK1/2, JNK, and p38) and degraded IkappaBalpha. Dominant negative MEK1 (a kinase that activates ERK1/2) blocked flagellin-stimulated IL-8 and MIP3alpha transcriptional activity, while the MEK-specific inhibitors PD98059 and U0126 reduced protein production of these cytokines. Conversely, transfection with a constitutively active MEK1 increased IL-8 and MIP3alpha transcriptional activity in a NFkappaB-independent manner. Furthermore, overexpression of the constitutively active MEK1 induced IL-8 and MIP3alpha protein production. We also demonstrated that C-terminal coiled-coil and TRAF-C domains of TRAF6, unable to mediate NFkappaB activation, are involved in MEK-mediated IL-8 and MIP3alpha expression. Thus, in non-transformed human colonocytes, MEK activation following flagellin/TLR5 engagement is a key modulator for NFkappaB-independent, IL-8 and MIP3alpha expression. |
| Databáze: | OpenAIRE |
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