iRhom2 is essential for innate immunity to DNA viruses by mediating trafficking and stability of the adaptor STING.

STING is a central adaptor in the innate immune response to DNA viruses. However, the manner in which STING activity is regulated remains unclear. We identified iRhom2 ('inactive rhomboid protein 2') as a positive regulator of DNA-virus-triggered induction of type I interferons. iRhom2 deficiency markedly impaired DNA-virus- and intracellular-DNA-induced signaling in cells, and iRhom2-deficient mice were more susceptible to lethal herpes simplex virus type 1 (HSV-1) infection. iRhom2 was constitutively associated with STING and acted in two distinct processes to regulate STING activity. iRhom2 recruited the translocon-associated protein TRAPß to the STING complex to facilitate trafficking of STING from the endoplasmic reticulum to perinuclear microsomes. iRhom2 also recruited the deubiquitination enzyme EIF3S5 to maintain the stability of STING through removal of its K48-linked polyubiquitin chains. These results suggest that iRhom2 is essential for STING activity, as it regulates TRAPß-mediated translocation and EIF3S5-mediated deubiquitination of STING.

The Zinc-Finger Protein ZCCHC3 Binds RNA and Facilitates Viral RNA Sensing and Activation of the RIG-I-like Receptors.

Recognition of viral RNA by the retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) initiates innate antiviral immune response. How the binding of viral RNA to and activation of the RLRs are regulated remains enigmatic. In this study, we identified ZCCHC3 as a positive regulator of the RLRs including RIG-I and MDA5. ZCCHC3 deficiency markedly inhibited RNA virus-triggered induction of downstream antiviral genes, and ZCCHC3-deficient mice were more susceptible to RNA virus infection. ZCCHC3 was associated with RIG-I and MDA5 and functions in two distinct processes for regulation of RIG-I and MDA5 activities. ZCCHC3 bound to dsRNA and enhanced the binding of RIG-I and MDA5 to dsRNA. ZCCHC3 also recruited the E3 ubiquitin ligase TRIM25 to the RIG-I and MDA5 complexes to facilitate its K63-linked polyubiquitination and activation. Thus, ZCCHC3 is a co-receptor for RIG-I and MDA5, which is critical for RLR-mediated innate immune response to RNA virus.

Photocatalytic synthesis of azaheterocycle-fused piperidines and pyrrolidines via tandem difunctionalization of unactivated alkenes.

A variety of azaheterocycle-fused piperidines and pyrrolidines bearing CF3 and CHF2 functionalities were obtained using CF3SO2Na and CHF2SO2Na by visible light photocatalysis. This protocol involves a radical cascade cyclization via tandem tri- and difluoromethylation-arylation of pendent unactivated alkenes. Benzimidazole, imidazole, theophylline, purine, and indole serve as applicable anchors, thereby enriching the structural diversity of piperidine and pyrrolidine derivatives. This method features mild, additive-free and transition metal-free conditions.

Ubiquitination of TLR3 by TRIM3 signals its ESCRT-mediated trafficking to the endolysosomes for innate antiviral response.

Trafficking of toll-like receptor 3 (TLR3) from the endoplasmic reticulum (ER) to endolysosomes and its subsequent proteolytic cleavage are required for it to sense viral double-stranded RNA (dsRNA) and trigger antiviral response, yet the underlying mechanisms remain enigmatic. We show that the E3 ubiquitin ligase TRIM3 is mainly located in the Golgi apparatus and transported to the early endosomes upon stimulation with the dsRNA analog poly(I:C). TRIM3 mediates K63-linked polyubiquitination of TLR3 at K831, which is enhanced following poly(I:C) stimulation. The polyubiquitinated TLR3 is recognized and sorted by the ESCRT (endosomal sorting complex required for transport) complexes to endolysosomes. Deficiency of TRIM3 impairs TLR3 trafficking from the Golgi apparatus to endosomes and its subsequent activation. Trim3-/- cells and mice express lower levels of antiviral genes and show lower levels of inflammatory response following poly(I:C) but not lipopolysaccharide (LPS) stimulation. These findings suggest that TRIM3-mediated polyubiquitination of TLR3 represents a feedback-positive regulatory mechanism for TLR3-mediated innate immune and inflammatory responses.

USP44 positively regulates innate immune response to DNA viruses through deubiquitinating MITA.

Mediator of IRF3 activation (MITA, also known as stimulator of interferon genes, STING) senses the second messenger cyclic GMP-AMP (cGAMP) which is synthesized upon DNA virus infection and activates innate antiviral immune response. It has been demonstrated that the activity of MITA is delicately regulated by various post-translational modifications including polyubiquitination. In this study, we identified the deubiquitinating enzyme USP44 as a positive regulator of MITA. USP44 is recruited to MITA following DNA virus infection and removes K48-linked polyubiquitin moieties from MITA at K236, therefore prevents MITA from proteasome mediated degradation. USP44-deficiency results in acceleration of HSV-1-induced degradation of MITA and reduced induction of type I interferons (IFNs) and proinflammatory cytokines. Consistently, Usp44-/- mice are more susceptible to HSV-1 infection as indicated by higher tissue viral titers, greater tissue damage and lower survival rate. These findings suggest that USP44 plays a specific and critical role in the regulation of innate immune response against DNA viruses.

Human Cytomegalovirus Protein UL94 Targets MITA to Evade the Antiviral Immune Response.

Cyclic GMP-AMP synthase (cGAS) senses double-stranded DNA and synthesizes the second messenger cyclic GMP-AMP (cGAMP), which binds to mediator of IRF3 activation (MITA) and initiates MITA-mediated signaling, leading to induction of type I interferons (IFNs) and other antiviral effectors. Human cytomegalovirus (HCMV), a widespread and opportunistic pathogen, antagonizes the host antiviral immune response to establish latent infection. Here, we identified HCMV tegument protein UL94 as an inhibitor of the cGAS-MITA-mediated antiviral response. Ectopic expression of UL94 impaired cytosolic double-stranded DNA (dsDNA)- and DNA virus-triggered induction of type I IFNs and enhanced viral replication. Conversely, UL94 deficiency potentiated HCMV-induced transcription of type I IFNs and downstream antiviral effectors and impaired viral replication. UL94 interacted with MITA, disrupted the dimerization and translocation of MITA, and impaired the recruitment of TBK1 to the MITA signalsome. These results suggest that UL94 plays an important role in the immune evasion of HCMV.IMPORTANCE Human cytomegalovirus (HCMV), a large double-stranded DNA (dsDNA) virus, encodes more than 200 viral proteins. HCMV infection causes irreversible abnormalities of the central nervous system in newborns and severe syndromes in organ transplantation patients or AIDS patients. It has been demonstrated that HCMV has evolved multiple immune evasion strategies to establish latent infection. Previous studies pay more attention to the mechanism by which HCMV evades immune response in the early phase of infection. In this study, we identified UL94 as a negative regulator of the innate immune response, which functions in the late phase of HCMV infection.

The heterogeneous nuclear ribonucleoprotein hnRNPM inhibits RNA virus-triggered innate immunity by antagonizing RNA sensing of RIG-I-like receptors.

Recognition of viral RNA by the retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), including RIG-I and MDA5, initiates innate antiviral responses. Although regulation of RLR-mediated signal transduction has been extensively investigated, how the recognition of viral RNA by RLRs is regulated remains enigmatic. In this study, we identified heterogeneous nuclear ribonucleoprotein M (hnRNPM) as a negative regulator of RLR-mediated signaling. Overexpression of hnRNPM markedly inhibited RNA virus-triggered innate immune responses. Conversely, hnRNPM-deficiency increased viral RNA-triggered innate immune responses and inhibited replication of RNA viruses. Viral infection caused translocation of hnRNPM from the nucleus to the cytoplasm. hnRNPM interacted with RIG-I and MDA5, and impaired the binding of the RLRs to viral RNA, leading to inhibition of innate antiviral response. Our findings suggest that hnRNPM acts as an important decoy for excessive innate antiviral immune response.

YIPF5 Is Essential for Innate Immunity to DNA Virus and Facilitates COPII-Dependent STING Trafficking.

STING plays central roles in the innate immune response to pathogens that contain DNA. Sensing cytoplasmic DNA by cyclic GMP-AMP synthase produces cyclic GMP-AMP, which binds to and activates STING and induces STING translocation from the endoplasmic reticulum to the perinuclear microsome. However, this trafficking process has not been fully elucidated yet. In this study, we identified YIPF5 as a positive regulator of STING trafficking. YIPF5 is essential for DNA virus- or intracellular DNA-triggered production of type I IFNs. Consistently, knockdown of YIPF5 impairs cellular antiviral responses to DNA virus. Mechanistically, YIPF5 interacts with both STING and components of COPII, facilitating STING recruitment to COPII in the presence of cytoplasmic dsDNA. Furthermore, knockdown of components of COPII inhibits DNA virus-triggered production of type I IFNs, suggesting that COPII is involved in innate immune responses to DNA viruses. Collectively, our findings demonstrate that YIPF5 positively regulates STING-mediated innate immune responses by recruiting STING to COPII-coated vesicles and facilitating STING trafficking from the endoplasmic reticulum to Golgi, providing important insights into the molecular mechanisms of intracellular DNA-stimulated STING trafficking and activation.

SNX8 modulates innate immune response to DNA virus by mediating trafficking and activation of MITA.

MITA (also called STING) is a central adaptor protein in innate immune response to cytosolic DNA. Cellular trafficking of MITA from the ER to perinuclear microsomes after DNA virus infection is critical for MITA activation and onset of innate antiviral response. Here we found that SNX8 is a component of DNA-triggered induction of downstream effector genes and innate immune response. Snx8-/- mice infected with the DNA virus HSV-1 exhibited lower serum cytokine levels and higher viral titers in the brains, resulting in higher lethality. Mechanistically, SNX8 recruited the class III phosphatylinositol 3-kinase VPS34 to MITA, which is required for trafficking of MITA from the ER to perinuclear microsomes. Our findings suggest that SNX8 is a critical component in innate immune response to cytosolic DNA and DNA virus.

TRIM32-TAX1BP1-dependent selective autophagic degradation of TRIF negatively regulates TLR3/4-mediated innate immune responses.

Toll-like receptor (TLR)-mediated signaling are critical for host defense against pathogen invasion. However, excessive responses would cause harmful damages to the host. Here we show that deficiency of the E3 ubiquitin ligase TRIM32 increases poly(I:C)- and LPS-induced transcription of downstream genes such as type I interferons (IFNs) and proinflammatory cytokines in both primary mouse immune cells and in mice. Trim32-/- mice produced higher levels of serum inflammatory cytokines and were more sensitive to loss of body weight and inflammatory death upon Salmonella typhimurium infection. TRIM32 interacts with and mediates the degradation of TRIF, a critical adaptor protein for TLR3/4, in an E3 activity-independent manner. TRIM32-mediated as well as poly(I:C)- and LPS-induced degradation of TRIF is inhibited by deficiency of TAX1BP1, a receptor for selective autophagy. Furthermore, TRIM32 links TRIF and TAX1BP1 through distinct domains. These findings suggest that TRIM32 negatively regulates TLR3/4-mediated immune responses by targeting TRIF to TAX1BP1-mediated selective autophagic degradation.

iRhom2 is essential for innate immunity to RNA virus by antagonizing ER- and mitochondria-associated degradation of VISA.

VISA (also known as MAVS, IPS-1 and Cardif) is an essential adaptor protein in innate immune response to RNA virus. The protein level of VISA is delicately regulated before and after viral infection to ensure the optimal activation and timely termination of innate antiviral response. It has been reported that several E3 ubiquitin ligases can mediate the degradation of VISA, but how the stability of VISA is maintained before and after viral infection remains enigmatic. In this study, we found that the ER-associated inactive rhomboid protein 2 (iRhom2) plays an essential role in mounting an efficient innate immune response to RNA virus by maintaining the stability of VISA through distinct mechanisms. In un-infected and early infected cells, iRhom2 mediates auto-ubiquitination and degradation of the E3 ubiquitin ligase RNF5 and impairs the assembly of VISA-RNF5-GP78 complexes, thereby antagonizes ER-associated degradation (ERAD) of VISA. In the late phase of viral infection, iRhom2 mediates proteasome-dependent degradation of the E3 ubiquitin ligase MARCH5 and impairs mitochondria-associated degradation (MAD) of VISA. Maintenance of VISA stability by iRhom2 ensures efficient innate antiviral response at the early phase of viral infection and ready for next round of response. Our findings suggest that iRhom2 acts as a checkpoint for the ERAD/MAD of VISA, which ensures proper innate immune response to RNA virus.

[Research progress on identification and quality control of Cervi Cornu Pantotrichum].

Cervi Cornu Pantotrichum, as a traditional Chinese medicine, has great potential for development. However, the identification and quality control system is not perfect, leading to the market chaos and chronic slow growth in deep processing of Cervi Cornu Pantotrichum. This paper gives an overview of present situation in identification and quality control system of the Cervi Cornu Pantotrichum, and analyzes present problems. Based on these results, the feasibility study scheme in identification and quality control system for Cervi Cornu Pantotrichum would be then put forward, providing ideas to establish its comprehensive evaluation system.

Activation of the cGAS-STING-IRF3 Axis by Type I and II Interferons Contributes to Host Defense.

Interferons (IFNs) activate JAK-STAT pathways to induce downstream effector genes for host defense against invaded pathogens and tumors. Here both type I (ß) and II (γ) IFNs are shown that can activate the transcription factor IRF3 in parallel with STAT1. IRF3-deficiency impairs transcription of a subset of downstream effector genes induced by IFN-ß and IFN-γ. Mechanistically, IFN-induced activation of IRF3 is dependent on the cGAS-STING-TBK1 axis. Both IFN-ß and IFN-γ cause mitochondrial DNA release into the cytosol. In addition, IFNs induce JAK1-mediated tyrosine phosphorylation of cGAS at Y214/Y215, which is essential for its DNA binding activity and signaling. Furthermore, deficiency of cGAS, STING, or IRF3 impairs IFN-ß- or IFN-γ-mediated antiviral and antitumor activities. The findings reveal a novel IRF3 activation pathway parallel with the canonical STAT1/2 activation pathways triggered by IFNs and provide an explanation for the pleiotropic roles of the cGAS-STING-IRF3 axis in host defense.

LDLR is an entry receptor for Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV) is the most widespread tick-born zoonotic bunyavirus that causes severe hemorrhagic fever and death in humans. CCHFV enters the cell via clathrin-mediated endocytosis which is dependent on its surface glycoproteins. However, the cellular receptors that are required for CCHFV entry are unknown. Here we show that the low density lipoprotein receptor (LDLR) is an entry receptor for CCHFV. Genetic knockout of LDLR impairs viral infection in various CCHFV-susceptible human, monkey and mouse cells, which is restored upon reconstitution with ectopically-expressed LDLR. Mutagenesis studies indicate that the ligand binding domain (LBD) of LDLR is necessary for CCHFV infection. LDLR binds directly to CCHFV glycoprotein Gc with high affinity, which supports virus attachment and internalization into host cells. Consistently, a soluble sLDLR-Fc fusion protein or anti-LDLR blocking antibodies impair CCHFV infection into various susceptible cells. Furthermore, genetic knockout of LDLR or administration of an LDLR blocking antibody significantly reduces viral loads, pathological effects and death following CCHFV infection in mice. Our findings suggest that LDLR is an entry receptor for CCHFV and pharmacological targeting of LDLR may provide a strategy to prevent and treat Crimean-Congo hemorrhagic fever.

Diazotization-Enabled Deaminative Late-Stage Functionalization of Primary Sulfonamides.

We, for the first time, disclosed a simple and efficient strategy for the late-stage functionalization of primary sulfonamides by diazotization, leading to sulfonyl chlorides, sulfonates, and complex sulfonamides. This protocol obviates the requirement for the prefunctionalization of sulfonamides. Its applicability is exemplified by the late-stage functionalization of sulfonamide-type drugs.

Expression of nucleus accumbens-1 in colon cancer negatively modulates antitumor immunity.

BACKGROUND: Nucleus accumbens-1 (NAC-1) is highly expressed in a variety of tumors, including colon cancer, and is closely associated with tumor recurrence, metastasis, and invasion. AIM: To determine whether and how NAC-1 affects antitumor immunity in colon cancer. METHODS: NAC-1-siRNA was transfected into RKO colon cancer cells to knock down NAC expression; tumor cells with or without knockdown of NAC-1 were treated with CD8+ T cells to test their cytocidal effect. The level of the immune checkpoint programmed death receptor-1 ligand (PD-L1) in colon cancer cells with or without knockdown of NAC-1 was analyzed using Quantitative real-time polymerase chain reaction and Western blotting. A double luciferase reporter assay was used to examine the effects of NAC-1 on the transcription of PD-L1. Mice bearing MC-38-OVA colon cancer cells expressing NAC-shRNA or control-shRNA were treated with OT-I mouse CD8+ T cells to determine the tumor response to immunotherapy. Immune cells in the tumor tissues were analyzed using flow cytometry. NAC-1, PD-L1 and CD8+ T cells in colon cancer specimens from patients were examined using immunohistochemistry staining. RESULTS: Knockdown of NAC-1 expression in colon cancer cells significantly enhanced the cytocidal effect of CD8+ T cells in cell culture experiments. The sensitizing effect of NAC-1 knockdown on the antitumor action of cytotoxic CD8+ T cells was recapitulated in a colon cancer xenograft animal model. Furthermore, knockdown of NAC-1 in colon cancer cells decreased the expression of PD-L1 at both the mRNA and protein levels, and this effect could be rescued by transfection of an RNAi-resistant NAC-1 expression plasmid. In a reporter gene assay, transient expression of NAC-1 in colon cancer cells increased the promoter activity of PD-L1, indicating that NAC-1 regulates PD-L1 expression at the transcriptional level. In addition, depletion of tumoral NAC-1 increased the number of CD8+ T cells but decreased the number of suppressive myeloid-derived suppressor cells and regulatory T cells. CONCLUSION: Tumor expression of NAC-1 is a negative determinant of immunotherapy.

Transcription-independent regulation of STING activation and innate immune responses by IRF8 in monocytes.

Sensing of cytosolic DNA of microbial or cellular/mitochondrial origin by cGAS initiates innate immune responses via the adaptor protein STING. It remains unresolved how the activity of STING is balanced between a productive innate immune response and induction of autoimmunity. Here we show that interferon regulatory factor 8 (IRF8) is essential for efficient activation of STING-mediated innate immune responses in monocytes. This function of IRF8 is independent of its transcriptional role in monocyte differentiation. In uninfected cells, IRF8 remains inactive via sequestration of its IRF-associated domain by its N- and C-terminal tails, which reduces its association with STING. Upon triggering the DNA sensing pathway, IRF8 is phosphorylated at Serine 151 to allow its association with STING via the IRF-associated domain. This is essential for STING polymerization and TBK1-mediated STING and IRF3 phosphorylation. Consistently, IRF8-deficiency impairs host defense against the DNA virus HSV-1, and blocks DNA damage-induced cellular senescence. Bone marrow-derived mononuclear cells which have an autoimmune phenotype due to deficiency of Trex1, respond to IRF-8 deletion with reduced pro-inflammatory cytokine production. Peripheral blood mononuclear cells from systemic lupus erythematosus patients are characterized by elevated phosphorylation of IRF8 at the same Serine residue we find to be important in STING activation, and in these cells STING is hyper-active. Taken together, the transcription-independent function of IRF8 we describe here appears to mediate STING activation and represents an important regulatory step in the cGAS/STING innate immune pathway in monocytes.

The RNA-binding protein LUC7L2 mediates MITA/STING intron retention to negatively regulate innate antiviral response.

MITA (also known as STING) is an ER-located adaptor protein, which mediates DNA-triggered innate immune response and is critically involved in autoimmune diseases and tumorigenesis. MITA is regulated by post-translational modifications, but how post-transcriptional mechanisms are involved in the regulation of MITA is still largely unknown. Here, we identified the RNA-binding protein LUC7L2 as a negative regulator of DNA virus-triggered innate immune response. LUC7L2-deficient mice exhibited resistance to lethal herpes simplex virus 1 (HSV-1) infection and reduced HSV-1 loads in the brain. Mechanistically, LUC7L2 directly bound to intron 3 of MITA precursor messenger RNA, inhibited its splicing and promoted its nonsense-mediated decay, leading to its downregulation at protein level. LUC7L2-deficient cells had markedly increased MITA level, leading to heightened innate antiviral response. Finally, LUC7L2 was induced following HSV-1 infection. Our findings reveal a feedback negative post-transcriptional regulatory mechanism for regulation of MITA-mediated innate immune response to viral and aberrant cellular DNA.

Systematic Review with Meta-Analysis: The Effects of Probiotics in Nonalcoholic Fatty Liver Disease.

BACKGROUND AND AIMS: Probiotics was considered as a potential therapy for nonalcoholic fatty liver disease (NAFLD) without approval and comprehensive assessment in recent years, which call for a meta-analysis. METHODS: We performed electronic and manual searches including English and Chinese databases published before April 2019, with the use of mesh term and free text of "nonalcoholic fatty liver disease" and "probiotics." Clinical trials evaluating the efficacy of probiotic therapy in NAFLD patients were included according to the eligibility criteria. With the use of random effects models, clinical outcomes were presented as weighted mean difference (WMD) with 95% confidence interval (CI), while heterogeneity and meta-regression were also assessed. RESULTS: 28 clinical trials enrolling 1555 criterion proven NAFLD patients with the use of probiotics from 4 to 28 weeks were included. Overall, probiotic therapy had beneficial effects on body mass index (WMD: -1.46, 95% CI: [-2.44, -0.48]), alanine aminotransferase (WMD: -13.40, 95% CI: [-17.03, -9.77]), aspartate transaminase (WMD: -13.54, 95% CI: [-17.86, -9.22]), gamma-glutamyl transpeptidase (WMD: -9.88, 95% CI: [-17.77, -1.99]), insulin (WMD: -1.32, 95% CI: [-2.43, -0.21]), homeostasis model assessment-insulin resistance (WMD: -0.42, 95% CI: [-0.73, -0.12]), and total cholesterol (WMD: -15.38, 95% CI: [-26.50, -4.25]), but not in fasting blood sugar, lipid profiles, or tumor necrosis factor-alpha. CONCLUSION: The systematic review and meta-analysis support that probiotics are superior to placebo in NAFLD patients and could be utilized as a common complementary therapeutic approach.