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.
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.
Ncr1‐dependent Dicer1 deletion results in the loss of microRNAs specifically in natural killer (NK) cells. This affects NK cells at multiple levels, with decreased differentiation, survival, sensitivity to IL‐15, and effector functions, leading to defective control of metastasis. This underscores the role of microRNAs in NK cell biology.
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 report that ...the metabolic checkpoint kinase mTOR is activated and boosts bioenergetic metabolism upon NK cell exposure to high concentrations of IL-15 whereas low doses of IL-15 only triggers the phosphorylation of the transcription factor STAT5. mTOR stimulates NK cell growth and nutrient uptake and positively feeds back onto the IL-15 receptor. This process is essential to sustain NK cell proliferation during development and acquisition of cytolytic potential upon inflammation or virus infection. The mTORC1 inhibitor rapamycin inhibits NK cell cytotoxicity both in mouse and human, which likely contribute to the immunosuppressant activities of this drug in different clinical settings.
According to the World Health Organization, food safety is an essential public health priority. In this context, we report a relevant proof of feasibility for the indirect specific detection of ...bacteria in food samples using unlabeled phage amplification coupled to ESI mass spectrometry analysis and illustrated with the model phage systems T4 and SPP1. High-resolving power mass spectrometry analysis (including bottom-up and top-down protein analysis) was used for the discovery of specific markers of phage infection. Structural components of the viral particle and nonstructural proteins encoded by the phage genome were identified. Then, targeted detection of these markers was performed on a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. E. coli at 1 × 105, 5 × 105, and 1 × 106 CFU/mL concentrations was successfully detected after only a 2 h infection time by monitoring phage T4 structural markers in Luria–Bertani broth, orange juice, and French bean stew (“cassoulet”) matrices. Reproducible detection of nonstructural markers was also demonstrated, particularly when a high titer of input phages was required to achieve successful amplification. This strategy provides a highly time-effective and sensitive assay for bacterial detection.
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