SUMMARY Ionizing radiation-mediated tumor regression depends on type I interferon (IFN) and the adaptive immune response, but the several pathways control I IFN induction. Here, we demonstrate that adaptor protein STING, but not MyD88, is required for type I IFN-dependent antitumor effects of radiation. In dendritic cells (DCs), STING was required for IFN-β induction in response to irradiated-tumor cells. The cytosolic DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS) mediated sensing of irradiated-tumor cells in DCs. Moreover, STING was essential for radiation-induced adaptive immune responses, which relied on type I IFN signaling on DCs. Exogenous IFN-β treatment rescued the cross-priming by cGAS or STING-deficient DCs. Accordingly, activation of STING by a second messenger cGAMP administration enhanced antitumor immunity induced by radiation. Thus radiation-mediated antitumor immunity in immunogenic tumors requires a functional cytosolic DNA-sensing pathway and suggests cGAMP treatment may provide a new strategy to improve radiotherapy.

Invasion of microbial DNA into the cytoplasm of animal cells triggers a cascade of host immune reactions that help clear the infection; however, self DNA in the cytoplasm can cause autoimmune diseases. Biochemical approaches led to the identification of cyclic GMP-AMP (cGAMP) synthase (cGAS) as a cytosolic DNA sensor that triggers innate immune responses. Here we show that cells from cGAS-deficient (cGas−/−) mice, including fibroblasts, macrophages and dendritic cells, failed to produce type-I interferons and other cytokines in response to DNA transfection or DNA virus infection. cGas−/− mice were more susceptible to lethal infection with herpes simplex virus-1 (HSV1) than wild type mice. We also show that cGAMP is an adjuvant that boosts antigen-specific T cell activation and antibody production in mice.

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We review the problem of dark energy, including a survey of theoretical models and some aspects of numerical studies.

The effect of defects on electron-hole separation is not always clear and is sometimes contradictory. Herein, we initially built clear models of two-dimensional atomic layers with tunable defect concentrations, and hence directly disclose the defect type and distribution at atomic level. As a prototype, defective one-unit-cell ZnInS atomic layers are successfully synthesized for the first time. Aberration-corrected scanning transmission electron microscopy directly manifests their distinct zinc vacancy concentrations, confirmed by positron annihilation spectrometry and electron spin resonance analysis. Density-functional calculations reveal that the presence of zinc vacancies ensures higher charge density and efficient carrier transport, verified by ultrafast photogenerated electron transfer time of ∼15 ps from the conduction band of ZnInS to the trap states. Ultrafast transient absorption spectroscopy manifests the higher zinc vacancy concentration that allows for ∼1.7-fold increase in average recovery lifetime, confirmed by surface photovoltage spectroscopy and PL spectroscopy analysis, which ensures promoted carrier separation rates. As a result, the one-unit-cell ZnInS layers with rich zinc vacancies exhibit a carbon monoxide formation rate of 33.2 μmol g h, roughly 3.6 times higher than that of the one-unit-cell ZnInS layers with poor zinc vacancies, while the former's photocatalytic activity shows negligible loss after 24 h photocatalysis. This present work uncovers the role of defects in affecting electron-hole separation at atomic level, opening new opportunities for achieving highly efficient solar CO reduction performances.

TREX1 is an exonuclease that digests DNA in the cytoplasm. Loss-of-function mutations of TREX1 are linked to Aicardi–Goutieres Syndrome (AGS) and systemic lupus erythematosus (SLE) in humans. Trex1−/− mice exhibit autoimmune and inflammatory phenotypes that are associated with elevated expression of interferon (IFN)-induced genes (ISGs). Cyclic GMP-AMP (cGAMP) synthase (cGAS) is a cytosolic DNA sensor that activates the IFN pathway. Upon binding to DNA, cGAS is activated to catalyze the synthesis of cGAMP, which functions as a second messenger that binds and activates the adaptor protein STING to induce IFNs and other cytokines. Here we show that genetic ablation of cGas in Trex1−/− mice eliminated all detectable pathological and molecular phenotypes, including ISG induction, autoantibody production, aberrant T-cell activation, and lethality. Even deletion of just one allele of cGas largely rescued the phenotypes of Trex1−/− mice. Similarly, deletion of cGas in mice lacking DNaseII, a lysosomal enzyme that digests DNA, rescued the lethal autoimmune phenotypes of the DNaseII−/− mice. Through quantitative mass spectrometry, we found that cGAMP accumulated in mouse tissues deficient in Trex1 or DNaseII and that this accumulation was dependent on cGAS. These results demonstrate that cGAS activation causes the autoimmune diseases in Trex1−/− and DNaseII−/− mice and suggest that inhibition of cGAS may lead to prevention and treatment of some human autoimmune diseases caused by self-DNA.

Summary Activation of the DNA-dependent cytosolic surveillance pathway in response to Mycobacterium tuberculosis infection stimulates ubiquitin-dependent autophagy and inflammatory cytokine production, and plays an important role in host defense against M. tuberculosis. However, the identity of the host sensor for M. tuberculosis DNA is unknown. Here we show that M. tuberculosis activated cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) in macrophages to produce cGAMP, a second messenger that activates the adaptor protein stimulator of interferon genes (STING) to induce type I interferons and other cytokines. cGAS localized with M. tuberculosis in mouse and human cells and in human tuberculosis lesions. Knockdown or knockout of cGAS in human or mouse macrophages blocked cytokine production and induction of autophagy. Mice deficient in cGAS were more susceptible to lethality caused by infection with M. tuberculosis. These results demonstrate that cGAS is a vital innate immune sensor of M. tuberculosis infection.

Unraveling the role of surface oxide on affecting its native metal disulfide's CO photoreduction remains a grand challenge. Herein, we initially construct metal disulfide atomic layers and hence deliberately create oxidized domains on their surfaces. As an example, SnS atomic layers with different oxidation degrees are successfully synthesized. In situ Fourier transform infrared spectroscopy spectra disclose the COOH* radical is the main intermediate, whereas density-functional-theory calculations reveal the COOH* formation is the rate-limiting step. The locally oxidized domains could serve as the highly catalytically active sites, which not only benefit for charge-carrier separation kinetics, verified by surface photovoltage spectra, but also result in electron localization on Sn atoms near the O atoms, thus lowering the activation energy barrier through stabilizing the COOH* intermediates. As a result, the mildly oxidized SnS atomic layers exhibit the carbon monoxide formation rate of 12.28 μmol g h, roughly 2.3 and 2.6 times higher than those of the poorly oxidized SnS atomic layers and the SnS atomic layers under visible-light illumination. This work uncovers atomic-level insights into the correlation between oxidized sulfides and CO reduction property, paving a new way for obtaining high-efficiency CO photoreduction performances.