Glutaminase as a metabolic checkpoint in NK cell cytotoxicity: mechanistic uncertainties and translational implications.

In their recent study, Jedlička et al. demonstrate that glutaminase (GLS) activity is indispensable for sustaining human natural killer (NK) cell cytotoxicity, positing it as a key metabolic regulator of effector function. While this work provides a valuable foundation for understanding NK cell immunometabolism, our analysis identifies several critical areas requiring deeper exploration. This letter offers a prospective critique, highlighting the incomplete delineation of the downstream metabolic mechanisms-specifically regarding energy production, biosynthetic precursor synthesis, and redox homeostasis-that link GLS activity to the cytolytic machinery. Furthermore, we question the physiological relevance of these in vitro findings within the nutrient-deprived and competitive tumor microenvironment (TME), where NK cells must exhibit metabolic flexibility. A paramount concern is the translational double-edged sword of GLS inhibition, which may inadvertently suppress anti-tumor immunity. We conclude that future research must employ integrated multi-omics and in vivo models to resolve these complexities, which is essential for harnessing NK cell metabolism without compromising its therapeutic potential.