We report here the identification and characterization of a protein, ERIS, an endoplasmic reticulum (ER) IFN stimulator, which is a strong type I IFN stimulator and plays a pivotal role in response to both non-self-cytosolic RNA and dsDNA. ERIS (also known as STING or MITA) resided exclusively on ER membrane. The ER retention/ retrieval sequence RIR was found to be critical to retain the protein on ER membrane and to maintain its integrity. ERIS was dimerized on innate immune challenges. Coumermycin-induced ERIS dimerization led to strong and fast IFN induction, suggesting that dimerization of ERIS was critical for self-activation and subsequent downstream signaling.innate immunity ͉ type I IFN ͉ functional cDNA library screening ͉ cytosolic RNA and dsDNA ͉ ER retention signal M icrobial infection-induced host immune responses are initiated by the germline-encoded pattern recognition receptors, which recognize components specific to microorganisms. There are 3 major classes of such receptors: Toll-like receptors (TLRs), RIG-I-like helicases (RLHs) and NOD-like receptors (1). During infection, nucleic acids derived from microbes are recognized by TLRs and RLHs, which then trigger a series of signaling events leading to the production of type I IFNs and proinflammatory cytokines.RLHs have recently been identified to sense the invading viruses in the cytoplasm. Unlike TLRs, which are expressed in specific cells like macrophages and dendritic cells, RLHs are found in most cell types (2). They contain caspase recruitment domain (CARD) and DExD/H helicase domain. RLHs interact with microbial nucleotides through their helicase domain. The N-terminal CARDs are responsible for activating downstream signaling pathways that mediate type I IFN production. Genetic analyses demonstrate that RIG-I and MDA5 sense distinct types of viruses (3-5). RIG-I and MDA5 use a common adaptor molecule, IPS-1 (also known as Cardif, MAVS, or VISA) (6-9). IPS-1 is found to reside on the mitochondrial membrane by its C-terminal transmembrane (TM) domain. It also contains a CARD-like domain at its N-terminus, which mediates the interaction with MDA5 or RIG-I. IPS-1 transmits the signal to TANK-binding kinase-1 (TBK1)/I B kinase i (IKKi; also known as IKK ) and the IKK complex to activate interferon regulatory factor (IRF)-3/IRF-7 and NF-B, respectively, collectively eliciting innate antiviral immune responses, including type I IFN production.On the other hand, dsDNA in the cytosol, for example, genomic DNA from intracellular bacteria (e.g., Listeria, Legionella), also causes a strong host immune response independent of TLRs, leading to the induction of type I IFN. A recent report has indicated that the molecule DAI (also known as ZBP1) might serve as a cytosolic dsDNA sensor (10). However, ZBP1 Ϫ/Ϫ cells showed normal type I IFN production in response to dsDNA stimulation (11). Meanwhile, reports showed that IPS-1/Cardif/MAVS/VISA was not required for dsDNA-caused innate immune activation (12).The signaling induced by cytoplasmic dsDNA leading ...

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Previous studies have suggested that ␣-glucosidase inhibitors such as castanospermine and deoxynojirimycin inhibit dengue virus type 1 infection by disrupting the folding of the structural proteins prM and E, a step crucial to viral secretion. We extend these studies by evaluating the inhibitory activity of castanospermine against a panel of clinically important flaviviruses including all four serotypes of dengue virus, yellow fever virus, and West Nile virus. Using in vitro assays we demonstrated that infections by all serotypes of dengue virus were inhibited by castanospermine. In contrast, yellow fever virus and West Nile virus were partially and almost completely resistant to the effects of the drug, respectively. Castanospermine inhibited dengue virus infection at the level of secretion and infectivity of viral particles. Importantly, castanospermine prevented mortality in a mouse model of dengue virus infection, with doses of 10, 50, and 250 mg/kg of body weight per day being highly effective at promoting survival (P < 0.0001). Correspondingly, castanospermine had no adverse or protective effect on West Nile virus mortality in an analogous mouse model. Overall, our data suggest that castanospermine has a strong antiviral effect on dengue virus infection and warrants further development as a possible treatment in humans.Dengue fever, the most prevalent arthropod-borne viral illness in humans, is caused by dengue virus (DEN). DEN is a single-stranded, positive-polarity, enveloped RNA virus that is translated in the cytoplasm as a single polyprotein and cleaved into three structural and seven nonstructural proteins. Four related serotypes of DEN exist in nature and are transmitted to humans primarily by two mosquitoes, Aedes aegypti and Aedes albopictus. DEN is a member of the Flaviviridae family and is genetically related to the viruses that cause yellow fever, hepatitis C, and the Japanese, St. Louis, and West Nile encephalitides. DEN infection results in a spectrum of disease ranging from a debilitating, self-limited illness (dengue fever) to a life-threatening syndrome (dengue hemorrhagic fever [DHF]). DEN causes disease globally with an estimated 25 to 100 million new infections per year (34). At present, no vaccine has been approved for human use and treatment is supportive.Flavivirus assembly takes place at the endoplasmic reticulum (ER) (7). The structural glycoproteins prM and E localize to the luminal side of the ER and form an immature particle with prM and E in a heterodimeric complex (7, 58). Furin-mediated proteolysis of prM in the trans-Golgi network (48) triggers rearrangement, homodimerization of E, and formation of the mature viral particle before release from the infected cell (1, 16). In flavivirus-infected mammalian cells, a 14-residue oligosaccharide, (Glc) 3 (Man) 9 (GlcNAc) 2 , is added in the ER to specific asparagine residues on the prM and E proteins. This high-mannose carbohydrate is sequentially modified in the ER by resident ␣-glucosidases to generate N-linked glycans that lack t...

Highlights d Antibody blockade of MerTK prevents apoptotic cell clearance by macrophages d MerTK blockade induces tumor-cGAS-and host-STINGdependent type I IFN response d Extracellular ATP facilitates transfer of tumor-derived cGAMP to TAMs via P2X7R d MerTK blockade increases tumor immunogenicity and enhances anti-PD-1/PD-L1 therapy

The re-emergence of Zika virus (ZIKV) and Ebola virus (EBOV) poses serious and continued threats to the global public health. Effective therapeutics for these maladies is an unmet need. Here, we show that emetine, an anti-protozoal agent, potently inhibits ZIKV and EBOV infection with a low nanomolar half maximal inhibitory concentration (IC50) in vitro and potent activity in vivo. Two mechanisms of action for emetine are identified: the inhibition of ZIKV NS5 polymerase activity and disruption of lysosomal function. Emetine also inhibits EBOV entry. Cephaeline, a desmethyl analog of emetine, which may be better tolerated in patients than emetine, exhibits a similar efficacy against both ZIKV and EBOV infections. Hence, emetine and cephaeline offer pharmaceutical therapies against both ZIKV and EBOV infection.

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Cyclic GMP-AMP (cGAMP) synthase (cGAS, a.k.a. MB21D1), a cytosolic DNA sensor, catalyzes formation of the second messenger 2’3’-cGAMP that activates the stimulator of interferon genes (STING) signaling. How the cGAS activity is modulated remains largely unknown. Here, we demonstrate that sentrin/SUMO-specific protease 7 (SENP7) interacted with and potentiated cGAS activation. The small ubiquitin-like modifier (SUMO) was conjugated onto the lysine residues 335, 372 and 382 of cGAS, which suppressed its DNA-binding, oligomerization and nucleotidyl-transferase activities. SENP7 reversed this inhibition via catalyzing the cGAS de-SUMOylation. Consistently, silencing of SENP7 markedly impaired the IRF3-responsive gene expression induced by cGAS-STING axis. SENP7-knockdown mice were more susceptible to herpes simplex virus 1 (HSV-1) infection. SENP7 was significantly up-regulated in patients with SLE. Our study highlights the temporal modulation of the cGAS activity via dynamic SUMOylation, uncovering a novel mechanism for fine-tuning the STING signaling in innate immunity.

A Mismatch-Tolerant LAMP a visual determination method by adding colorimetric dyes. Because of its simplicity, all LAMP-based diagnostic assays may be easily updated to the newly improved version. The novel mismatch-tolerant LAMP method represents a simple, sensitive and promising approach for molecular diagnosis of highly variable viruses, and it is especially suited for application in resource-limited settings.