Exosomes regulate cell-cell communication by transferring functional proteins and RNAs between cells. Here, to clarify the function of exosomes during influenza virus infection, researchers from the University of Tokyo characterized lung-derived exosomal microRNAs (miRNAs). Among the detected miRNAs, miR-483-3p was present at high levels in bronchoalveolar lavage fluid (BALF) exosomes during infection of mice with various strains of influenza virus, and miR-483-3p transfection potentiated gene expression of type I interferon and proinflammatory cytokine upon viral infection of MLE-12 cells. RNF5, a regulator of the RIG-I signaling pathway, was identified as a target gene of miR-483-3p. Moreover, the researchers found that CD81, another miR-483-3p target, functions as a negative regulator of RIG-I signaling in MLE-12 cells. Taken together, this study indicates that BALF exosomal miRNAs may mediate the antiviral and inflammatory response to influenza virus infection.
miR-483-3p potentiates the activation of the nuclear translocation of IRF3 andNF-κB
MLE-12 cells were transfected with the miR-483-3p or control miRNA mimic. At 24 h post-transfection, the cells were transfected with poly(I:C). Cells were fixed for immunofluorescence at 6 h and 8 h for IRF3 and NF-κB, respectively. Localization of IRF3 and NF-κB was evaluated by confocal microscopy. The arrowheads indicate representative cells that showed nuclear translocation. The percentage of cells with nuclear IRF3 and NF-κB among miR-483-3p-or control miRNA-transfected cells was quantified by using IN Cell Analyzer and IN Cell Investigator.