title: The role of microRNAs miR-200b and miR-200c in TLR4 signaling and NF-κB activation.
abstract: Recognition of microbial products by members of the Toll-like receptor (TLR) family initiates intracellular signaling cascades that result in NF-κB activation and subsequent production of inflammatory cytokines. We explored the potential roles of microRNAs (miRNAs) in regulating TLR pathways. A target analysis approach to the TLR4 pathway adaptor molecules identified several putative targets of miR-200a, miR-200b and miR-200c. miRNA mimics were co-transfected with a NF-κB activity reporter plasmid into HEK293 cells stably expressing TLR4 (HEK293-TLR4). Mimics of both miR-200b and miR-200c, but not miR-200a, decreased NF-κB reporter activity in either untreated cells or in cells treated with endotoxin:MD2 as a TLR4 agonist. Transfection of HEK293-TLR4 cells with miR-200b or miR-200c significantly decreased expression of MyD88, whereas TLR4, IRAK-1 and TRAF-6 mRNAs were unaffected. When miR-200b or miR-200c mimics were transfected into the differentiated monocytic THP-1 cell line, the abundance of MyD88 transcripts, as well as LPS-induced expression of the pro-inflammatory molecules IL-6, CXCL9 and TNF-α were diminished. These data define miRNAs miR-200b and miR-200c as factors that modify the efficiency of TLR4 signaling through the MyD88-dependent pathway and can thus affect host innate defenses against microbial pathogens.
authors.affiliation: Interdisciplinary Program in Molecular and Cellular Biology, University of Iowa, Iowa City, IA, USA.
authors.forename: Erik B
authors.initials: EB
authors.lastname: Wendlandt
authors.forename: Joel W
authors.initials: JW
authors.lastname: Graff
authors.forename: Theresa L
authors.initials: TL
authors.lastname: Gioannini
authors.forename: Anton P
authors.initials: AP
authors.lastname: McCaffrey
authors.forename: Mary E
authors.initials: ME
authors.lastname: Wilson
mesh_terms: D054370:Chemokine CXCL9 / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000276:immunology*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D019076:Transgenes / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D054370:Chemokine CXCL9; D015850:Interleukin-6; D008070:Lipopolysaccharides; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha