STAT3 governs the HIF-1\u03b1 response in IL-15 primed human NK cells

Anna Coulibaly,Nina Kassner,Sonia Y Velásquez,Jutta Schulte,Maria Vittoria Barbarossa,Holger A Lindner

doi:10.1038/s41598-021-84916-0

Abstract

Natural killer (NK) cells mediate innate host defense against microbial infection and cancer. Hypoxia and low glucose are characteristic for these tissue lesions but do not affect early interferon (IFN) γ and CC chemokine release by interleukin 15 (IL-15) primed human NK cells in vitro. Hypoxia inducible factor 1α (HIF-1α) mediates cellular adaption to hypoxia. Its production is supported by mechanistic target of rapamycin complex 1 (mTORC1) and signal transducer and activator of transcription 3 (STAT3). We used chemical inhibition to probe the importance of mTORC1 and STAT3 for the hypoxia response and of STAT3 for the cytokine response in isolated and IL-15 primed human NK cells. Cellular responses were assayed by magnetic bead array, RT-PCR, western blotting, flow cytometry, and metabolic flux analysis. STAT3 but not mTORC1 activation was essential for HIF-1α accumulation, glycolysis, and oxygen consumption. In both primed normoxic and hypoxic NK cells, STAT3 inhibition reduced the secretion of CCL3, CCL4 and CCL5, and it interfered with IL-12/IL-18 stimulated IFNγ production, but it did not affect cytotoxic granule degranulation up on target cell contact. We conclude that IL-15 priming promotes the HIF-1α dependent hypoxia response and the early cytokine response in NK cells predominantly through STAT3 signaling.

Highlights

Natural killer (NK) cells mediate innate host defense against microbial infection and cancer
We recently presented experimental evidence for a role of mechanistic target of rapamycin (mTOR) complex 1 and signal transducer and activator of transcription 3 (STAT3) in Hypoxia inducible factor 1α (HIF-1α) activation in response to the cytokine interleukin 15 (IL-15) in human NK cells cultured under chemical hypoxia and developed a mathematical model of this process[22]
To the long-term metabolic requirements[31,32,33], we recently found IL-12/IL-18 stimulated short-term release of IFNγ and CCL3, CCL4, and CCL5 from both normoxic and hypoxic IL-15 primed human NK cells to be essentially independent of glucose availability[34]

Summary

Introduction

Natural killer (NK) cells mediate innate host defense against microbial infection and cancer. STAT3 but not mTORC1 activation was essential for HIF-1α accumulation, glycolysis, and oxygen consumption In both primed normoxic and hypoxic NK cells, STAT3 inhibition reduced the secretion of CCL3, CCL4 and CCL5, and it interfered with IL-12/IL-18 stimulated IFNγ production, but it did not affect cytotoxic granule degranulation up on target cell contact. To the long-term metabolic requirements[31,32,33], we recently found IL-12/IL-18 stimulated short-term release of IFNγ and CCL3, CCL4, and CCL5 from both normoxic and hypoxic IL-15 primed human NK cells to be essentially independent of glucose availability[34] This has questioned the importance of glycolysis as a cellular source of energy and anabolic precursors for the early cytokine response in human NK cells even under hypoxia. Glucose deprivation for 4 h still reduced intracellular IFNγ abundance by around 30%34 which agrees with long-term dependence of IFNγ release on glycolysis[31,32,33]

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Results

Conclusion