Study on the Role of TNF-α/TNFR2 Axis in NK Cell Metabolic Reprogramming Based on TR-FRET Technology

Natural killer (NK) cells are innate lymphocytes that play a crucial role in early responses to microbial infections. Upon infection or inflammation, NK cells rapidly proliferate and become primary cytotoxic cells. During this process, NK cells undergo metabolic reprogramming to support their expansion and differentiation into potent effector cells. IL-2 and IL-15 activate mTORC1, a key metabolic sensor required for glycolytic reprogramming through upregulation of various glycolytic enzymes and GLUT1. Previous studies have shown that TNF-α signaling enhances NK cell function via TNFR2, but the mechanism by which TNFR2 activates NK cells remains incompletely understood. The TR-FRET TNF-α/TNFR2 assay kit can detect the binding activity of TNF-α to TNFR2, providing a technical tool to study the role of this signaling axis in NK cell metabolic regulation.

Studies have found that after injecting mice with MCMV or LPS, NK cells upregulate TNFR2 expression, which correlates with increased proliferation, metabolic activity, and effector function. Further investigation into cytokines that promote TNFR2 upregulation revealed that IL-18 in the IL-18-MyD88 signaling pathway induces TNFR2 expression in NK cells, enhancing their sensitivity to TNF-α. In vitro experiments demonstrate that co-administration of IL-18 and TNF-α synergistically promotes NK cell activation and metabolic activity. The TR-FRET TNF-α/TNFR2 assay kit can quantitatively measure the binding affinity between TNF-α and TNFR2, assessing dynamic changes in receptor-ligand interactions under different conditions.

Mechanistically, after TNF-α binds to TNFR2, it upregulates the expression of CD25 and nutrient transporters in NK cells, leading to a metabolic shift toward aerobic glycolysis. This metabolic switch is a critical step for NK cell proliferation and acquisition of effector function. Transcriptomic analysis shows that in TNFR2-knockout mice, NK cells exhibit significantly reduced expression of genes involved in cell metabolism and proliferation. Genetic ablation of TNFR2 suppresses CD25 upregulation and TNF-α-induced glycolysis, impairing NK cell proliferation and antiviral function during viral infection in vivo. TR-FRET technology can be applied to detect the activation status of the TNFR2 signaling pathway, providing a quantitative analytical tool for studying the molecular mechanisms of metabolic reprogramming.

This study identifies the critical role of TNF-α binding to TNFR2 in NK cell proliferation, glycolysis, and effector function. This signaling axis acts as a metabolic switch, tilting the metabolic balance of NK cells toward aerobic glycolysis. The impact of TNF-α on NK cells is essential for understanding their antiviral and antitumor activities. During viral infection, several cytokines such as IL-12, IL-18, and IL-15 can induce NK cell proliferation. Additionally, activated NK cell receptors recognize viral glycoproteins expressed on infected cells, inducing infected cell killing and preferential proliferation of specific subsets. The interaction between TNF-α and TNFR2 plays a central regulatory role in this process.

This study has certain limitations. Due to the use of immunocompromised mouse models, the absence of complete immune cell interactions means the important role of membrane-bound TNF-α presented by other immune cells to NK cells remains unexplored. Furthermore, complex interactions between adoptive cells and host cells may exist, making it impossible to conduct comprehensive research using the current mouse models. Considering these limitations, further studies using appropriate models with intact immune cell interactions are needed to explore the effects of membrane-bound TNF-α on NK cell function, providing a more comprehensive understanding of the mechanisms regulating NK cell responses during viral infection. The TR-FRET TNF-α/TNFR2 assay kit can be applied to comparative studies of receptor-ligand interactions in different model systems.

NK cells are being used in adoptive immunotherapy, including CAR-NK cell therapy. The large-scale expansion of NK cells for cancer immunotherapy highlights the potential impact of TNFR2 signaling in ensuring extensive NK cell proliferation and expansion. The findings of this study expand our understanding of the pleiotropic effects of TNF-α on NK cells. Exploring the possibility of genetically engineering NK cells to upregulate TNFR2 expression is a potential research direction for adoptive immunotherapy. Investigating whether TNFR2 overexpression can enhance NK cell activity for more effective immunotherapeutic outcomes requires further research into the relevance and applicability of the TNF-α/TNFR2 axis in human NK cells. TR-FRET technology can be applied to screen molecules that modulate the binding of TNF-α to TNFR2, providing technical support for developing novel immunotherapeutic strategies.

Nanjing UA-Bio Technology Co., Ltd. (UA-Bio) has independently developed the "UniOne® TR-FRET Human TNF-α/TNFR2 Binding Kit" (Catalog No.: UA086008), a high-performance analysis platform specifically designed for studying the interaction between tumor necrosis factor-α (TNF-α) and its receptor TNFR2. Based on time-resolved fluorescence resonance energy transfer (TR-FRET) technology, this kit accurately and efficiently evaluates the binding activity between human TNF-α and TNFR2, providing a stable and reliable standardized solution for research in inflammatory disease mechanisms, immunomodulatory drug screening, and autoimmune disease treatment development.