Activation-Specific Metabolic Requirements for NK Cell IFN-γ Production

Abstract

There has been increasing recognition of the importance of cellular metabolism and metabolic substrates for the function and differentiation of immune cells. Here, for the first time, we investigate the metabolic requirements for production of IFN-γ by freshly isolated NK cells. Primary murine NK cells mainly utilize mitochondrial oxidative phosphorylation at rest and with short-term activation. Remarkably, we discovered significant differences in the metabolic requirements of murine NK cell IFN-γ production depending upon the activation signal. Stimulation of NK cell IFN-γ production was independent of glycolysis or mitochondrial oxidative phosphorylation when cells were activated with IL-12+IL-18. By contrast, stimulation via activating NK receptors required glucose-driven oxidative phosphorylation. Prolonged treatment with high-dose, but not low dose, IL-15 eliminated the metabolic requirement for receptor stimulation. In summary, this study demonstrates that metabolism provides an essential second signal for induction of IFN-γ production by activating NK cell receptors that can be reversed with prolonged high-dose IL-15 treatment.

Glycolytic requirement for NK cell cytotoxicity and cytomegalovirus control

“…Extracellular flux assays confirmed that 2DG treatment significantly decreased NK cell glycolysis, as measured by the extracellular acidification rate (ECAR) ( Figure 1A). We previously demonstrated that naive murine NK cells primarily use glucose-based oxidative phosphorylation (10). Consistent with this, 2DG treatment also decreased the oxygen consumption rate (OCR) ( Figure 1A).…”

“…We found that receptor activation depends less on these metabolic pathways after priming with high-dose IL-15 (10). Others have found that after expansion in IL-15 and stimulation with IL-2 + IL-12, highly activated lymphokine-activated killer (LAK) cells require glycolysis for maximal production of IFN-γ and the cytotoxic granule protein granzyme B (Gzmb) (12).…”

“…Naive NK cells rely on glucose-fueled oxidative phosphorylation, while expansion with IL-15 elevates metabolic rates with a preference toward glycolysis, similar to changes seen during the activation of CD8 + T cells (10,11). Several studies show that NK cell production of the cytokine IFN-γ is regulated by metabolism (10,(12)(13)(14). We previously demonstrated that, in freshly isolated murine NK cells, IFN-γ production after short-term receptor activation is highly dependent on glycolytic NK cell activation has been shown to be metabolically regulated in vitro; however, the role of metabolism during in vivo NK cell responses to infection is unknown.…”

“…Recent studies have demonstrated that certain NK cell responses require metabolic cues. Naive NK cells rely on glucose-fueled oxidative phosphorylation, while expansion with IL-15 elevates metabolic rates with a preference toward glycolysis, similar to changes seen during the activation of CD8 + T cells (10,11). Several studies show that NK cell production of the cytokine IFN-γ is regulated by metabolism (10,(12)(13)(14).…”

IL-15 activates mTOR and primes stress-activated gene expression leading to prolonged antitumor capacity of NK cells

“…48 Consistently, Keppel et al recently demonstrated that IL-15 potentiates glycolytic functions on human NK cells which are essential for their effector functions. 52 Furthermore, Chang et al showed that tumor-infiltrating lymphocytes that regained glycolytic potential after checkpoint blockade therapy are more efficient in eliminating tumor cells. 53 In this context, it would be of interest to monitor NK-cell activity in patients treated with mTOR inhibitors, such as rapalogs.…”