Understanding nucleic acid sensing and its therapeutic applications.

Nucleic acid sensing is involved in viral infections, immune response-related diseases, and therapeutics. Based on the composition of nucleic acids, nucleic acid sensors are defined as DNA or RNA sensors. Pathogen-associated nucleic acids are recognized by membrane-bound and intracellular receptors, known as pattern recognition receptors (PRRs), which induce innate immune-mediated antiviral responses. PRR activation is tightly regulated to eliminate infections and prevent abnormal or excessive immune responses. Nucleic acid sensing is an essential mechanism in tumor immunotherapy and gene therapies that target cancer and infectious diseases through genetically engineered immune cells or therapeutic nucleic acids. Nucleic acid sensing supports immune cells in priming desirable immune responses during tumor treatment. Recent studies have shown that nucleic acid sensing affects the efficiency of gene therapy by inhibiting translation. Suppression of innate immunity induced by nucleic acid sensing through small-molecule inhibitors, virus-derived proteins, and chemical modifications offers a potential therapeutic strategy. Herein, we review the mechanisms and regulation of nucleic acid sensing, specifically covering recent advances. Furthermore, we summarize and discuss recent research progress regarding the different effects of nucleic acid sensing on therapeutic efficacy. This study provides insights for the application of nucleic acid sensing in therapy.

FTO negatively regulates the cytotoxic activity of natural killer cells.

N6 -Methyladenosine (m6 A) is the most abundant epitranscriptomic mark and plays a fundamental role in almost every aspect of mRNA metabolism. Although m6 A writers and readers have been widely studied, the roles of m6 A erasers are not well-understood. Here, we investigate the role of FTO, one of the m6 A erasers, in natural killer (NK) cell immunity. We observe that FTO-deficient NK cells are hyperactivated. Fto knockout (Fto-/- ) mouse NK cells prevent melanoma metastasis in vivo, and FTO-deficient human NK cells enhance the antitumor response against leukemia in vitro. We find that FTO negatively regulates IL-2/15-driven JAK/STAT signaling by increasing the mRNA stability of suppressor of cytokine signaling protein (SOCS) family genes. Our results suggest that FTO is an essential modulator of NK cell immunity, providing a new immunotherapeutic strategy for allogeneic NK cell therapies.

NgR1 is an NK cell inhibitory receptor that destabilizes the immunological synapse.

The formation of an immunological synapse (IS) is essential for natural killer (NK) cells to eliminate target cells. Despite an advanced understanding of the characteristics of the IS and its formation processes, the mechanisms that regulate its stability via the cytoskeleton are unclear. Here, we show that Nogo receptor 1 (NgR1) has an important function in modulating NK cell-mediated killing by destabilization of IS formation. NgR1 deficiency or blockade resulted in improved tumor control of NK cells by enhancing NK-to-target cell contact stability and regulating F-actin dynamics during IS formation. Patients with tumors expressing abundant NgR1 ligand had poor prognosis despite high levels of NK cell infiltration. Thus, our study identifies NgR1 as an immune checkpoint in IS formation and indicates a potential approach to improve the cytolytic function of NK cells in cancer immunotherapy.

A modifiable universal cotinine-chimeric antigen system of NK cells with multiple targets.

Natural killer (NK) cells are immune effector cells with outstanding features for adoptive immunotherapy. Immune effector cells with chimeric antigen receptors (CARs) are promising targeted therapeutic agents for various diseases. Because tumor cells exhibit heterogeneous antigen expression and lose cell surface antigen expression during malignant progression, many CARs fixed against only one antigen have limited efficacy and are associated with tumor relapse. To expand the utility of CAR-NK cells, we designed a split and universal cotinine-CAR (Cot-CAR) system, comprising a Cot-conjugator and NK92 cells (α-Cot-NK92 cells) engineered with a CAR containing an anti-Cot-specific single-chain variable fragment and intracellular signaling domain. The efficacy of the Cot-CAR system was assessed in vitro using a cytolysis assay against various tumor cells, and its single- or multiple- utility potential was demonstrated using an in vivo lung metastasis model by injecting A549-Red-Fluc cells. The α-Cot-NK92 cells could switch targets, logically respond to multiple antigens, and tune cytolytic activation through the alteration of conjugators without re-engineering. Therefore the universal Cot-CAR system is useful for enhancing specificity and diversity of antigens, combating relapse, and controlling cytolytic activity. In conclusion, this universal Cot-CAR system reveals that multiple availability and controllability can be generated with a single, integrated system.

Tryptophanyl-tRNA Synthetase as a Potential Therapeutic Target.

Tryptophanyl-tRNA synthetase (WRS) is an essential enzyme that catalyzes the ligation of tryptophan (Trp) to its cognate tRNAtrp during translation via aminoacylation. Interestingly, WRS also plays physiopathological roles in diseases including sepsis, cancer, and autoimmune and brain diseases and has potential as a pharmacological target and therapeutic. However, WRS is still generally regarded simply as an enzyme that produces Trp in polypeptides; therefore, studies of the pharmacological effects, therapeutic targets, and mechanisms of action of WRS are still at an emerging stage. This review summarizes the involvement of WRS in human diseases. We hope that this will encourage further investigation into WRS as a potential target for drug development in various pathological states including infection, tumorigenesis, and autoimmune and brain diseases.

MicroRNA-150 controls differentiation of intraepithelial lymphocytes through TGF-ß receptor II regulation.

BACKGROUND: Intraepithelial lymphocytes (IELs) in the intestines play pivotal roles in maintaining the integrity of the mucosa, regulating immune cells, and protecting against pathogenic invasion. Although several extrinsic factors, such as TGF-ß, have been identified to contribute to IEL generation, intrinsic regulatory factors have not been determined fully. OBJECTIVE: Here we investigated the regulation of IEL differentiation and the underlying mechanisms in mice. METHODS: We analyzed IELs and the expression of molecules associated with IEL differentiation in wild-type control and microRNA (miRNA)-150 knockout mice. Methotrexate was administered to mice lacking miR-150 and control mice. RESULTS: miR-150 deficiency reduced the IEL population in the small intestine and increased susceptibility to methotrexate-induced mucositis. Evaluation of expression of IEL differentiation-associated molecules showed that miR-150-deficient IELs exhibited decreased expression of TGF-ß receptor (TGF-ßR) II, CD103, CD8αα, and Runt-related transcription factor 3 in all the IEL subpopulations. The reduced expression of TGF-ßRII in miR-150-deficient IELs was caused by increased expression of c-Myb/miR-20a. Restoration of miR-150 or inhibition of miR-20a recovered the TGF-ßRII expression. CONCLUSION: miR-150 is an intrinsic regulator of IEL differentiation through TGF-ßRII regulation. miR-150-mediated IEL generation is crucial for maintaining intestinal integrity against anticancer drug-induced mucositis.

miR-150-Mediated Foxo1 Regulation Programs CD8+ T Cell Differentiation.

MicroRNA (miR)-150 is a developmental regulator of several immune-cell types, but its role in CD8+ T cells is largely unexplored. Here, we show that miR-150 regulates the generation of memory CD8+ T cells. After acute virus infection, miR-150 knockout (KO) mice exhibited an accelerated differentiation of CD8+ T cells into memory cells and improved production of effector cytokines. Additionally, miR-150 KO CD8+ T cells displayed an enhanced recall response and improved protection against infections with another virus and bacteria. We found that forkhead box O1 (Foxo1) and T cell-specific transcription factor 1 (TCF1) are upregulated during the early activation phase in miR-150 KO CD8+ T cells and that miR-150 directly targets and suppresses Foxo1. These results suggest that miR-150-mediated suppression of Foxo1 regulates the balance between effector and memory cell differentiation, which might aid in the development of improved vaccines and T cell therapeutics.

MicroRNA-150 modulates intracellular Ca 2+ levels in naïve CD8+ T cells by targeting TMEM20.

Regulation of intracellular Ca2+ signaling is a major determinant of CD8+ T cell responsiveness, but the mechanisms underlying this regulation of Ca2+ levels, especially in naïve CD8+ T cells, are not fully defined. Here, we showed that microRNA-150 (miR-150) controls intracellular Ca2+ levels in naïve CD8+ T cells required for activation by suppressing TMEM20, a negative regulator of Ca2+ extrusion. miR-150 deficiency increased TMEM20 expression, which resulted in increased intracellular Ca2+ levels in naïve CD8+ T cells. The subsequent increase in Ca2+ levels induced expression of anergy-inducing genes, such as Cbl-b, Egr2, and p27, through activation of NFAT1, as well as reduced cell proliferation, cytokine production, and the antitumor activity of CD8+ T cells upon antigenic stimulation. The anergy-promoting molecular milieu and function induced by miR-150 deficiency were rescued by reinstatement of miR-150. Additionally, knockdown of TMEM20 in miR-150-deficient naïve CD8+ T cells reduced intracellular Ca2+ levels. Our findings revealed that miR-150 play essential roles in controlling intracellular Ca2+ level and activation in naïve CD8+ T cells, which suggest a mechanism to overcome anergy induction by the regulation of intracellular Ca2+ levels.