title: Human Cytomegalovirus miR-UL112-3p Targets TLR2 and Modulates the TLR2/IRAK1/NFκB Signaling Pathway.
abstract: Human Cytomegalovirus (HCMV) encodes multiple microRNAs (miRNAs) whose functions are just beginning to be uncovered. Using in silico approaches, we identified the Toll-Like Receptor (TLR) innate immunity pathway as a possible target of HCMV miRNAs. Luciferase reporter assay screens further identified TLR2 as a target of HCMV miR-UL112-3p. TLR2 plays a major role in innate immune response by detecting both bacterial and viral ligands, including HCMV envelope proteins gB and gH. TLR2 activates a variety of signal transduction routes including the NFκB pathway. Furthermore, TLR2 plays an important role in controlling CMV infection both in humans and in mice. Immunoblot analysis of cells transfected with a miR-UL112-3p mimic revealed that endogenous TLR2 is down-regulated by miR-UL112-3p with similar efficiency as a TLR2-targeting siRNA (siTLR2). We next found that TLR2 protein level decreases at late times during HCMV infection and correlates with miR-UL112-3p accumulation in fibroblasts and monocytic THP1 cells. Confirming direct miR-UL112-3p targeting, down-regulation of endogenous TLR2 was not observed in cells infected with HCMV mutants deficient in miR-UL112-3p expression, but transfection of miR-UL112-3p in these cells restored TLR2 down-regulation. Using a NFκB reporter cell line, we found that miR-UL112-3p transfection significantly inhibited NFκB-dependent luciferase activity with similar efficiency as siTLR2. Consistent with this observation, miR-UL112-3p transfection significantly reduced the expression of multiple cytokines (IL-1β, IL-6 and IL-8) upon stimulation with a TLR2 agonist. Finally, miR-UL112-3p transfection significantly inhibited the TLR2-induced post-translational activation of IRAK1, a kinase located in the upstream section of the TLR2/NFκB signaling axis. To our knowledge, this is the first identified mechanism of TLR2 modulation by HCMV and is the first report of functional targeting of TLR2 by a viral miRNA. These results provide a novel mechanism through which a HCMV miRNA regulates the innate immune response by down-regulating TLR-2 expression.
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Igor
authors.initials: I
authors.lastname: Landais
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Chantel
authors.initials: C
authors.lastname: Pelton
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Streblow
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Victor
authors.initials: V
authors.lastname: DeFilippis
authors.affiliation: Division of Biostatistics, Public Health and Preventive Medicine, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Shannon
authors.initials: S
authors.lastname: McWeeney
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Jay A
authors.initials: JA
authors.lastname: Nelson
mesh_terms: D020413:3' Untranslated Regions; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D008024:Ligands; D035683:MicroRNAs; D016328:NF-kappa B; D034741:RNA, Small Interfering; D012367:RNA, Viral; D011994:Recombinant Proteins; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; C000599836:microRNA-UL112, human cytomegalovirus; C507768:IRAK1 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases