RESUMO
Interleukin 15 (IL-15) controls both the homeostasis and the peripheral activation of natural killer (NK) cells. The molecular basis for this duality of action remains unknown. Here we found that the metabolic checkpoint kinase mTOR was activated and boosted bioenergetic metabolism after exposure of NK cells to high concentrations of IL-15, whereas low doses of IL-15 triggered only phosphorylation of the transcription factor STAT5. mTOR stimulated the growth and nutrient uptake of NK cells and positively fed back on the receptor for IL-15. This process was essential for sustaining NK cell proliferation during development and the acquisition of cytolytic potential during inflammation or viral infection. The mTORC1 inhibitor rapamycin inhibited NK cell cytotoxicity both in mice and humans; this probably contributes to the immunosuppressive activity of this drug in different clinical settings.
Assuntos
Interleucina-15/imunologia , Células Matadoras Naturais/imunologia , Ativação Linfocitária/imunologia , Serina-Treonina Quinases TOR/imunologia , Animais , Proliferação de Células , Células Cultivadas , Infecções por Herpesviridae/imunologia , Humanos , Imunossupressores/farmacologia , Inflamação/imunologia , Vírus da Influenza A Subtipo H1N1/imunologia , Células Matadoras Naturais/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina , Alvo Mecanístico do Complexo 2 de Rapamicina , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Complexos Multiproteicos/antagonistas & inibidores , Complexos Multiproteicos/genética , Complexos Multiproteicos/imunologia , Muromegalovirus/imunologia , Infecções por Orthomyxoviridae/imunologia , Poli I-C/imunologia , Fator de Transcrição STAT5/metabolismo , Transdução de Sinais/imunologia , Sirolimo/farmacologia , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/genéticaRESUMO
MicroRNAs control developmental pathways and effector functions in immune cells. Previous studies have studied the role of microRNAs in natural killer (NK) cells. However, the mouse models of microRNA depletion used were nonNK-specific and only partially depleting, hampering the interpretation of the data obtained. To clarify the role of microRNAs in murine NK cells, we deleted the RNase III enzyme Dicer1 in NKp46-expressing cells. We observed a drastic decrease in several microRNAs specifically in NK cells. Furthermore, the overall size of the "NK-cell" pool was severely decreased, a phenotype associated with compromised survival. Moreover, performing a broad flow cytometry profiling, we show that Dicer1-deficient NK cells failed to complete their differentiation program. In particular, several integrins were inappropriately expressed in mature NK cells. These defects coincided with decreased response to IL-15, a cytokine responsible for "NK-cell" maturation and survival. In addition, Dicer1 deletion impaired key "NK-cell" functions: target cell killing and production of IFN-γ, leading to defective control of metastasis. Dicer1 deletion thus affects "NK-cell" biology in a cell intrinsic manner at several distinct stages.