MicroRNA-155 tunes both the threshold and extent of NK cell activation via targeting of multiple signaling pathways.
NK cells are innate lymphocytes important for host defense against viral infections and malignancy. However, the molecular programs orchestrating NK cell activation are incompletely understood. MicroRNA-155 (miR-155) is markedly upregulated following cytokine activation of human and mouse NK cells. Surprisingly, mature human and mouse NK cells transduced to overexpress miR-155, NK cells from mice with NK cell-specific miR-155 overexpression, and miR-155(-/-) NK cells all secreted more IFN-γ compared with controls. Investigating further, we found that activated NK cells with miR-155 overexpression had increased per-cell IFN-γ with normal IFN-γ(+) percentages, whereas greater percentages of miR-155(-/-) NK cells were IFN-γ(+). In vivo murine CMV-induced IFN-γ expression by NK cells in these miR-155 models recapitulated the in vitro phenotypes. We performed unbiased RNA-induced silencing complex sequencing on wild-type and miR-155(-/-) NK cells and found that mRNAs targeted by miR-155 were enriched in NK cell activation signaling pathways. Using specific inhibitors, we confirmed these pathways were mechanistically involved in regulating IFN-γ production by miR-155(-/-) NK cells. These data indicate that miR-155 regulation of NK cell activation is complex and that miR-155 functions as a dynamic tuner for NK cell activation via both setting the activation threshold as well as controlling the extent of activation in mature NK cells. In summary, miR-155(-/-) NK cells are more easily activated, through increased expression of proteins in the PI3K, NF-κB, and calcineurin pathways, and miR-155(-/-) and 155-overexpressing NK cells exhibit increased IFN-γ production through distinct cellular mechanisms.
Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110;
Ryan P
RP
Sullivan
Leslie A
LA
Fogel
Jeffrey W
JW
Leong
Stephanie E
SE
Schneider
Rachel
R
Wong
Rizwan
R
Romee
To-Ha
TH
Thai
Veronika
V
Sexl
Scot J
SJ
Matkovich
Gerald W
GW
Dorn
Anthony R
AR
French
Todd A
TA
Fehniger
D000818:Animals; D019703:Calcineurin / Q000502:physiology; D002478:Cells, Cultured; D003586:Cytomegalovirus Infections / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D017930:Genes, Reporter; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics; D007378:Interleukins / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018448:Models, Immunological; D016328:NF-kappa B / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017423:Sequence Analysis, RNA; D015398:Signal Transduction / Q000502:physiology*; D013047:Specific Pathogen-Free Organisms; D014161:Transduction, Genetic; D015854:Up-Regulation
D007378:Interleukins; C524942:MIRN155 microRNA, human; D035683:MicroRNAs; C532623:Mirn155 microRNA, mouse; D016328:NF-kappa B; D011993:Recombinant Fusion Proteins; D007371:Interferon-gamma; D019869:Phosphatidylinositol 3-Kinases; D019703:Calcineurin