Apoptotic Caspases Suppress Type I Interferon Production via the Cleavage of cGAS, MAVS, and IRF3.

Viral infection triggers host defenses through pattern-recognition receptor-mediated cytokine production, inflammasome activation, and apoptosis of the infected cells. Inflammasome-activated caspases are known to cleave cyclic GMP-AMP synthase (cGAS). Here, we found that apoptotic caspases are critically involved in regulating both DNA and RNA virus-triggered host defenses, in which activated caspase-3 cleaved cGAS, MAVS, and IRF3 to prevent cytokine overproduction. Caspase-3 was exclusively required in human cells, whereas caspase-7 was involved only in murine cells to inactivate cGAS, reflecting distinct regulatory mechanisms in different species. Caspase-mediated cGAS cleavage was enhanced in the presence of dsDNA. Alternative MAVS cleavage sites were used to ensure the inactivation of this critical protein. Elevated type I IFNs were detected in caspase-3-deficient cells without any infection. Casp3-/- mice consistently showed increased resistance to viral infection and experimental autoimmune encephalomyelitis. Our results demonstrate that apoptotic caspases control innate immunity and maintain immune homeostasis against viral infection.

Targeting of the CD161 inhibitory receptor enhances T-cell-mediated immunity against hematological malignancies.

ABSTRACT: The CD161 inhibitory receptor is highly upregulated by tumor-infiltrating T cells in multiple human solid tumor types, and its ligand, CLEC2D, is expressed by both tumor cells and infiltrating myeloid cells. Here, we assessed the role of the CD161 receptor in hematological malignancies. Systematic analysis of CLEC2D expression using the Cancer Cell Line Encyclopedia revealed that CLEC2D messenger RNA was most abundant in hematological malignancies, including B-cell and T-cell lymphomas as well as lymphocytic and myelogenous leukemias. CLEC2D protein was detected by flow cytometry on a panel of cell lines representing a diverse set of hematological malignancies. We, therefore, used yeast display to generate a panel of high-affinity, fully human CD161 monoclonal antibodies (mAbs) that blocked CLEC2D binding. These mAbs were specific for CD161 and had a similar affinity for human and nonhuman primate CD161, a property relevant for clinical translation. A high-affinity CD161 mAb enhanced key aspects of T-cell function, including cytotoxicity, cytokine production, and proliferation, against B-cell lines originating from patients with acute lymphoblastic leukemia, diffuse large B-cell lymphoma, and Burkitt lymphoma. In humanized mouse models, this CD161 mAb enhanced T-cell-mediated immunity, resulting in a significant survival benefit. Single cell RNA-seq data demonstrated that CD161 mAb treatment enhanced expression of cytotoxicity genes by CD4 T cells as well as a tissue-residency program by CD4 and CD8 T cells that is associated with favorable survival outcomes in multiple human cancer types. These fully human mAbs, thus, represent potential immunotherapy agents for hematological malignancies.

Inflammasome Activation Triggers Caspase-1-Mediated Cleavage of cGAS to Regulate Responses to DNA Virus Infection.

Viral infection triggers host innate immune responses that result in the production of various cytokines including type I interferons (IFN), activation of inflammasomes, and programmed cell death of the infected cells. Tight control of inflammatory cytokine production is crucial for the triggering of an effective immune response that can resolve the infection without causing host pathology. In examining the inflammatory response of Asc-/- and Casp1-/- macrophages, we found that deficiency in these molecules resulted in increased IFN production upon DNA virus infection, but not RNA virus challenge. Investigation of the underlying mechanism revealed that upon canonical and non-canonical inflammasome activation, caspase-1 interacted with cyclic GMP-AMP (cGAMP) synthase (cGAS), cleaving it and dampening cGAS-STING-mediated IFN production. Deficiency in inflammasome signaling enhanced host resistance to DNA virus in vitro and in vivo, and this regulatory role extended to other inflammatory caspases. Thus, inflammasome activation dampens cGAS-dependent signaling, suggesting cross-regulation between intracellular DNA-sensing pathways.

Ro-vibrational Distribution of NO+ Dissociated from NO2+ Ions in the a3B2 and b3A2 States: A Slow "Impulsive" Dissociation Example Revealed from Threshold Photoelectron-Photoion Coincidence Imaging.

To clarify the contentions about dissociative photoionization mechanism of nitrogen dioxide via the a3B2 and b3A2 ionic states, a new threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging has been conducted in the 12.8-14.0 eV energy range at the Hefei Light Source. The fine vibrational-resolved threshold photoelectron spectrum agrees well with the previous measurements. The ro-vibrational distributions of NO+, as the unique fragment ion in the dissociation of NO2+ in specific vibronic levels of a3B2 and b3A2 states, are derived from the recorded TPEPICO velocity images. A "cold" vibrational (v+ = 0) and "hot" rotational population is observed at the a3B2(0,3,0) and (0,4,0) vibronic levels, while the dissociation of NO2+ in b3A2(0,0,0) leads to the NO+ fragment with both hot vibrational and rotational populations. With the aid of the quantum chemical calculations at the time-dependent B3LYP level, minimum energy paths on the potential energy surfaces of the a3B2 and b3A2 states clarify their adiabatic dissociation mechanisms near the thresholds, and this study proposes reliable explanations for the observed internal energy distributions of fragment ions. Additionally, this study provides valuable insights into the application of the classical "impulsive" model on an overall slow dissociation process.

Circ_0104700 contributes to acute myeloid leukemia progression by enhancing MCM2 expression through targeting miR-665.

OBJECTIVE: Acute myeloid leukemia (AML) is a common blood cancer associated with poor prognosis and high mortality. In this study, we investigated the role and underlying mechanism of action of circ_0104700 in the pathogenesis of AML. METHODS: Circ_0104700 was screened from the GEO database and detected in AML samples and cell lines. The effect of circ_0104700 on AML was analyzed using a methylcellulose colony assay, CCK-8 assay, and cell cycle and apoptosis analyses. The mechanism was explored using bioinformatic analysis, quantitative reverse transcription-PCR, dual-luciferase reporter assays, northern blotting and western blot analysis in AML cells. RESULTS: Circ_0104700 expression was higher in AML patients and AML cell lines. Functionally, circ_0104700 depletion attenuated cell viability and induced apoptosis in MV-4-11 and Kasumi-1 cells. Circ_0104700 depletion enhanced the G0/G1-phase proportion but reduced the proportion of S-phase cells in MV-4-11 and Kasumi-1 cells. circ_0104700 served as a competing endogenous RNA of miR-665 and enhanced MCM2 expression by sponging miR-665 in MV-4-11 and Kasumi-1 cells. Silencing circ_0104700 repressed the proliferation and cell cycle and induced apoptosis of MV-4-11 and Kasumi-1 cells by inhibiting miR-665. MCM2 depletion alleviated the proliferation and cell cycle and enhanced the apoptosis of MV-4-11 and Kasumi-1 cells by inactivating JAK/STAT signaling. JAK/STAT signaling was involved in circ_0104700-mediated malignant phenotypes of MV-4-11 and Kasumi-1 cells. CONCLUSION: circ_0104700 contributed to AML progression by enhancing MCM2 expression by targeting miR-665. Our findings provide novel potential therapeutic targets for AML, including circ_0104700, miR-665, and MCM2.

Characteristic features of primary testicular lymphoma and survival trends: a multicenter clinical study.

OBJECTIVES: To retrospectively investigate the clinical characteristics, prognosis, treatment, and therapy outcome of Chinese patients with primary testicular lymphoma (PTL). METHODS: we collected data of 49 PTL patients from four hospitals over 13 years. The median age was 63 years old. We described the clinical characteristics of the patients including the laterality, serum lactate dehydrogenase (LDH), pathology classification, stage, International prognostic index (IPI) scores and more. RESULTS: Complete remission (CR) was achieved in 34 patients and partial remission (PR) in 3 patients; Progressive disease (PD) was detected in 11 patients, and 10 patients died. The average progression-free survival (PFS) of all patients was 43.92 months, and the average overall survival (OS) was 47.55 months. The Ann Arbor stage, IPI score, and LDH were associated with OS, while Ann Arbor stage, IPI score, LDH, and histotype were significantly associated with PFS. Chemotherapy and radiotherapy following orchiectomy was associated with a significantly longer PFS. CONCLUSION: Most patients can achieve CR after induced therapy or orchiectomy. However, there are many associated prognostic factors.

The STING phase-separator suppresses innate immune signalling.

Biomolecular condensates (biocondensates) formed via liquid-liquid phase-separation of soluble proteins have been studied extensively. However, neither the phase-separation of endoplasmic reticulum (ER) transmembrane protein nor a biocondensate with organized membranous structures has been reported. Here, we have discovered a spherical ER membranous biocondensate with puzzle-like structures caused by condensation of the ER-resident stimulator of interferon genes (STING) in DNA virus-infected or 2'3'-cGAMP (cyclic GMP-AMP)-treated cells, which required STING transmembrane domains, an intrinsically disordered region (IDR) and a dimerization domain. Intracellular 2'3'-cGAMP concentrations determined STING translocation or condensation. STING biocondensates constrained STING and TBK1 (TANK binding protein 1) to prevent innate immunity from overactivation, presumably acting like a 'STING-TBK1-cGAMP sponge'. Cells expressing STING-E336G/E337G showed notably enhanced innate immune responses due to impaired STING condensation after viral infection at later stages. Microtubule inhibitors impeded the STING condensate gel-like transition and augmented type I-interferon production in DNA virus-infected cells. This membranous biocondensate was therefore named the STING phase-separator.

Caspases control antiviral innate immunity.

Caspases are a family of cysteine proteases whose functions have been scrutinized intensively in recent years. Beyond their established roles in programmed cell death and inflammatory response, some caspases are also fundamental players in antiviral immunity by fine-tuning the levels of antiviral signaling adapters and cytokines, such as type I interferons, which serves as a major, sophisticated weapon against viruses. Viral infections can result in inflammasome activation and the initiation of cell death, including apoptosis and pyroptosis, and multiple caspases are significantly involved in these processes. This review will focus on the cutting-edge discoveries regarding the multifaceted roles of caspases in antiviral innate immunity.