scholarly journals Enterovirus A71 2B Inhibits Interferon-Activated JAK/STAT Signaling by Inducing Caspase-3-Dependent Karyopherin-α1 Degradation

2021 ◽  
Vol 12 ◽  
Author(s):  
Menghuai Sun ◽  
Qian Lin ◽  
Chunyang Wang ◽  
Jiao Xing ◽  
Kunlong Yan ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Caspase 3 ◽  
Infectious Clone ◽  
Underlying Mechanism ◽  
Neurological Complications ◽  
Type I ◽  
Structural Protein ◽  
Enterovirus A71 ◽  
Stat Signaling ◽  
Infected Cells

Enterovirus A71 (EV-A71) is a major pathogen that causes the hand, foot, and mouth disease, which could be fatal with neurological complications in children. The underlying mechanism for the severe pathogenicity remains obscure, but impaired or aberrant innate immunity is considered to play a key role in viral pathogenesis. We reported previously that EV-A71 suppressed type I interferon (IFN) responses by inducing degradation of karyopherin-α1 (KPNA1), a component of the p-STAT1/2 complex. In this report, we showed that 2B, a non-structural protein of EV-A71, was critical to the suppression of the IFN-α-induced type I response in infected cells. Among viral proteins, 2B was the only one that was involved in the degradation of KPNA1, which impeded the formation of the p-STAT1/2/KPNA1 complex and blocked the translocation of p-STAT1/2 into the nucleus upon IFN-α stimulation. Degradation of KPNA1 induced by 2B can be inhibited in the cells pre-treated with Z-DEVD-FMK, a caspase-3 inhibitor, or siRNA targeting caspase-3, indicating that 2B-induced degradation of KPNA1 was caspase-3 dependent. The mechanism by which 2B functioned in the dysregulation of the IFN signaling was analyzed and a putative hydrophilic domain (H1) in the N-terminus of 2B was characterized to be critical for the release of cytochrome c into the cytosol for the activation of pro-caspase-3. We generated an EV-A71 infectious clone (rD1), which was deficient of the H1 domain. In rD1-infected cells, degradation of KPNA1 was relieved and the infected cells were more sensitive to IFN-α, leading to decreased viral replication, in comparison to the cells infected with the virus carrying a full length 2B. Our findings demonstrate that EV-A71 2B protein plays an important role in dysregulating JAK-STAT signaling through its involvement in promoting caspase-3 dependent degradation of KPNA1, which represents a novel strategy employed by EV-A71 to evade host antiviral innate immunity.

scholarly journals Interaction between PHB2 and Enterovirus A71 VP1 Induces Autophagy and Affects EV-A71 Infection

Viruses ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 414 ◽  
Author(s):  
Weitao Su ◽  
Shan Huang ◽  
Huimin Zhu ◽  
Bao Zhang ◽  
Xianbo Wu
Keyword(s):  
Defense Mechanism ◽  
Foot And Mouth Disease ◽  
Underlying Mechanism ◽  
Host Protein ◽  
Mass Spectrometry Analysis ◽  
Structural Protein ◽  
Viral Protein Synthesis ◽  
Spectrometry Analysis ◽  
C Terminus ◽  
Enterovirus A71

Enterovirus A71 (EV-A71) is a major pathogen that causes severe and fatal cases of hand-foot-and-mouth disease (HFMD). HFMD caused by EV-A71 seriously endangers children’s health. Although autophagy is an important antiviral defense mechanism, some viruses have evolved strategies to utilize autophagy to promote self-replication. EV-A71 can utilize autophagy vesicles as replication scaffolds, indicating that EV-A71 infection is closely related to its autophagy induction mechanism. VP1, a structural protein of EV-A71, has been reported to induce autophagy, but the underlying mechanism is still unclear. In this study, we found that the C-terminus (aa 251–297) of VP1 induces autophagy. Mass spectrometry analysis suggested that prohibitin 2 (PHB2) interacts with the C-terminus of the EV-A71 VP1 protein, and this was further verified by coimmunoprecipitation assays. After PHB2 knockdown, EV-A71 replication, viral particle release, and viral protein synthesis were reduced, and autophagy was inhibited. The results suggest that PHB2 interaction with VP1 is essential for induction of autophagy and the infectivity of EV-A71. Furthermore, we confirmed that EV-A71 induced complete autophagy that required autolysosomal acidification, thus affecting EV-A71 infection. In summary, this study revealed that the host protein PHB2 is involved in an autophagy mechanism during EV-A71 infection.

scholarly journals SARS-CoV-2 non-structural protein 1 inhibits the interferon response by causing depletion of key host signaling factors.

2021 ◽  
Author(s):  
Anil Kumar ◽  
Ray Ishida ◽  
Tania Strilets ◽  
Jamie Cole ◽  
Joaquin Lopez-Orozco ◽  
...  
Keyword(s):  
Causative Agent ◽  
Interferon Response ◽  
Type I ◽  
Structural Protein ◽  
Type I Ifns ◽  
Rapid Spread ◽  
Host Signaling ◽  
Infected Cells ◽  
Serious Disease ◽  
Taste And Smell

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing COVID-19 pandemic. While previous studies have shown that several SARS-CoV-2 proteins can antagonize the interferon (IFN) response, some of the mechanisms by which they do so are not well understood. In this study, we describe two novel mechanisms by which SARS-CoV-2 blocks the IFN pathway. Type I IFNs and IFN-stimulated genes (ISGs) were poorly induced during SARS-CoV-2 infection and once infection was established, cells were highly resistant to ectopic induction of IFNs and ISGs. Levels of two key IFN signaling pathway components, Tyk2 and STAT2 were significantly lower in SARS-CoV-2 infected cells. Expression of non-structural protein 1 (NSP1) or nucleocapsid in the absence of other viral proteins was sufficient to block IFN induction but only NSP1 was able to inhibit IFN signaling. Mapping studies suggest that NSP1 prevents IFN induction in part by blocking IRF3 phosphorylation. In addition, NSP1-induced depletion of Tyk2 and STAT2 dampened ISG induction. Together, our study provides new insights into how SARS-CoV-2 successfully evades the IFN system to establish infection. Importance SARS-CoV-2 is the causative agent of COVID-19, a serious disease that can have myriad of symptoms from loss of taste and smell to pneumonia and hypercoagulation. The rapid spread of SARS-CoV-2 can be attributed in part to asymptomatic transmission, where infected individuals shed large amounts of virus before the onset of disease. This is likely due to the ability of SARS-CoV-2 to effectively suppress the innate immune system, including the IFN response. Indeed, we show that the IFN response is efficiently blocked during SARS-CoV-2 infection, a process that is mediated in large part by non-structural protein 1 and nucleocapsid. Our study provides new insights on how SARS-CoV-2 evades the IFN response to successfully establish infection. These findings should be considered for the development and administration of therapeutics against SARS-CoV-2.

scholarly journals Functional Insights into Silymarin as an Antiviral Agent against Enterovirus A71 (EV-A71)

2021 ◽  
Vol 22 (16) ◽  
pp. 8757
Author(s):  
Salima Lalani ◽  
Malihe Masomian ◽  
Chit Laa Poh
Keyword(s):  
Foot And Mouth Disease ◽  
Antiviral Agent ◽  
Underlying Mechanism ◽  
Neurological Complications ◽  
In Vivo Evaluation ◽  
Competitive Binding Assay ◽  
Enterovirus A71 ◽  
Viral Protein 1

Enterovirus A71 (EV-A71) is a major neurovirulent agent capable of causing severe hand, foot and mouth disease (HFMD) associated with neurological complications and death. Currently, no FDA-approved antiviral is available for the treatment of EV-A71 infections. The flavonoid silymarin was shown to exert virucidal effects, but the binding site on the capsid was unknown. In this study, the ligand interacting site of silymarin was determined in silico and validated in vitro. Moreover, the potential of EV-A71 to develop resistance against silymarin was further evaluated. Molecular docking of silymarin with the capsid of EV-A71 indicated that silymarin binds to viral protein 1 (VP1) of EV-A71, specifically at the GH loop of VP1. The in vitro binding of silymarin with VP1 of EV-A71 was validated using recombinant VP1 through ELISA competitive binding assay. Continuous passaging of EV-A71 in the presence of silymarin resulted in the emergence of a mutant carrying a substitution of isoleucine by threonine (I97T) at position 97 of the BC loop of EV-A71. The mutation was speculated to overcome the inhibitory effects of silymarin. This study provides functional insights into the underlying mechanism of EV-A71 inhibition by silymarin, but warrants further in vivo evaluation before being developed as a potential therapeutic agent.

scholarly journals Inhibition of Interferon Signaling by Rabies Virus Phosphoprotein P: Activation-Dependent Binding of STAT1 and STAT2

2006 ◽  
Vol 80 (6) ◽  
pp. 2675-2683 ◽  
Author(s):  
Krzysztof Brzózka ◽  
Stefan Finke ◽  
Karl-Klaus Conzelmann
Keyword(s):  
Rabies Virus ◽  
Transcriptional Activation ◽  
Type I ◽  
Interferon Signaling ◽  
Cell Extracts ◽  
Independent Functions ◽  
Stat Signaling ◽  
Infected Cells ◽  
Ifn Γ ◽  
In Cells

ABSTRACT Rabies virus (RV) phosphoprotein P is an interferon (IFN) antagonist counteracting transcriptional activation of type I IFN (K. Brzózka, S. Finke, and K. K. Conzelmann, J. Virol 79:7673-7681, 2005). We here show that RV P in addition is responsible for preventing IFN-α/β- and IFN-γ-stimulated JAK-STAT signaling in RV-infected cells by the retention of activated STATs in the cytoplasm. Expression of IFN-stimulated response element- and gamma-activated sequence-controlled genes was severely impaired in cells infected with RV SAD L16 or in cells expressing RV P protein from transfected plasmids. In contrast, a recombinant RV expressing small amounts of P had lost the ability to interfere with JAK-STAT signaling. IFN-mediated tyrosine phosphorylation of STAT1 and STAT2 was not impaired in RV P-expressing cells; rather, a defect in STAT recycling was suggested by distinct accumulation of tyrosine-phosphorylated STATs in cell extracts. In the presence of P, activated STAT1 and STAT2 were unable to accumulate in the nucleus. Notably, STAT1 and STAT2 were coprecipitated with RV P only from extracts of cells previously stimulated with IFN-α or IFN-γ, whereas in nonstimulated cells no association of P with STATs was observed. This conditional, IFN activation-dependent binding of tyrosine-phosphorylated STATs by RV P is unique for a viral IFN antagonist. The 10 C-terminal residues of P are required for counteracting JAK-STAT signaling but not for inhibition of transcriptional activation of IFN-β, thus demonstrating two independent functions of RV P in counteracting the host's IFN response.

scholarly journals Major Human Cytomegalovirus Structural Protein pp65 (ppUL83) Prevents Interferon Response Factor 3 Activation in the Interferon Response

2004 ◽  
Vol 78 (20) ◽  
pp. 10995-11006 ◽  
Author(s):  
Davide A. Abate ◽  
Shinya Watanabe ◽  
Edward S. Mocarski
Keyword(s):  
Underlying Mechanism ◽  
Nuclear Accumulation ◽  
Interferon Response ◽  
Type I ◽  
Response Factor ◽  
Structural Protein ◽  
Virion Protein ◽  
Virus Binding ◽  
Rapid Induction ◽  
Antiviral Control

ABSTRACT We have identified a cytomegalovirus virion protein capable of modulating the rapid induction of an interferon-like response in cells that follows virus binding and penetration. Functional genomics revealed a role for the major cytomegalovirus structural protein, pp65 (ppUL83), in counteracting this response. The underlying mechanism involves a differential impact of this structural protein on the regulation of interferon response factor 3 (IRF-3). In contrast, NF-κB is activated independent of pp65, and neither STAT1 nor STAT3 becomes activated by either virus. pp65 is sufficient to prevent the activation of IRF-3 when introduced alone into cells. pp65 acts by inhibiting nuclear accumulation of IRF-3 and is associated with a reduced IRF-3 phosphorylation state. Thus, this investigation shows that the major structural protein of cytomegalovirus is committed to the modulation of the IRF-3 response, a primary mediator of the type I interferon response. By subverting IRF-3, the virus escapes throwing a central alarm devoted to both immediate antiviral control and regulation of the immune response.

scholarly journals The VP3 Protein of Bluetongue Virus Associates with the MAVS Complex and Interferes with the RIG-I-Signaling Pathway

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 230
Author(s):  
Marie Pourcelot ◽  
Rayane Amaral Moraes ◽  
Aurore Fablet ◽  
Emmanuel Bréard ◽  
Corinne Sailleau ◽  
...  
Keyword(s):  
Bluetongue Virus ◽  
Type I Interferon ◽  
Type I ◽  
Adapter Protein ◽  
Structural Protein ◽  
Innate Response ◽  
Biting Midges ◽  
Domestic Ruminants ◽  
Infected Cells ◽  
Culicoides Biting Midges

Bluetongue virus (BTV), an arbovirus transmitted by Culicoides biting midges, is a major concern of wild and domestic ruminants. While BTV induces type I interferon (alpha/beta interferon [IFN-α/β]) production in infected cells, several reports have described evasion strategies elaborated by this virus to dampen this intrinsic, innate response. In the present study, we suggest that BTV VP3 is a new viral antagonist of the IFN-β synthesis. Indeed, using split luciferase and coprecipitation assays, we report an interaction between VP3 and both the mitochondrial adapter protein MAVS and the IRF3-kinase IKKε. Overall, this study describes a putative role for the BTV structural protein VP3 in the control of the antiviral response.

scholarly journals Role of Super Immune Activation Secondary to Infection in the Context of Cancer

2021 ◽  
Vol 01 (10) ◽  
Author(s):  
Javier Contreras Cardenas ◽  
Keyword(s):  
Innate Immunity ◽  
Risk Factor ◽  
Tumor Suppressor Genes ◽  
Nk Cell ◽  
Epigenetic Modification ◽  
Type I Interferons ◽  
Type I ◽  
Pathophysiological Mechanism ◽  
Infected Cells

By 2008, it was estimated that there were about 12.7 million new cases of cancer worldwide, resulting in 7.6 million deaths. We are aware of the heterogeneity that exists and that it is impossible to link its development in any organ to a single pathophysiological mechanism. The greatest risk factor for developing cancer is aging, as age is directly proportional to accumulated aberrations and exposure to carcinogens. Most cancers occur in people who have no overt immunodeficiency. It is evident, then, that tumor cells must develop mechanisms to escape or evade the immune system in immunocompetent hosts. The main mechanisms of innate immunity against viruses are inhibition of infection by type I interferons and NK cell-mediated death of infected cells. The hypothesis is that perhaps the ability of epigenetic modification, which varies from virus to virus, is not exclusively reduced to the ability to activate genes that lead to cancer; but also randomly empower the organism to activate tumor suppressor genes.

scholarly journals Phosphorylation of SARS-CoV-2 Orf9b Regulates Its Targeting to Two Binding Sites in TOM70 and Recruitment of Hsp90

2021 ◽  
Vol 22 (17) ◽  
pp. 9233
Author(s):  
Lukas Brandherm ◽  
Antonio Mario Kobaš ◽  
Mara Klöhn ◽  
Yannick Brüggemann ◽  
Stephanie Pfaender ◽  
...  
Keyword(s):  
Binding Site ◽  
Underlying Mechanism ◽  
Type I Interferons ◽  
Mitochondrial Outer Membrane ◽  
Type I ◽  
Mitochondrial Targeting ◽  
Terminal Domain ◽  
Associated Proteins ◽  
Infected Cells ◽  
Tpr Domain

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the causative agent of the COVID19 pandemic. The SARS-CoV-2 genome encodes for a small accessory protein termed Orf9b, which targets the mitochondrial outer membrane protein TOM70 in infected cells. TOM70 is involved in a signaling cascade that ultimately leads to the induction of type I interferons (IFN-I). This cascade depends on the recruitment of Hsp90-bound proteins to the N-terminal domain of TOM70. Binding of Orf9b to TOM70 decreases the expression of IFN-I; however, the underlying mechanism remains elusive. We show that the binding of Orf9b to TOM70 inhibits the recruitment of Hsp90 and chaperone-associated proteins. We characterized the binding site of Orf9b within the C-terminal domain of TOM70 and found that a serine in position 53 of Orf9b and a glutamate in position 477 of TOM70 are crucial for the association of both proteins. A phosphomimetic variant Orf9bS53E showed drastically reduced binding to TOM70 and did not inhibit Hsp90 recruitment, suggesting that Orf9b–TOM70 complex formation is regulated by phosphorylation. Eventually, we identified the N-terminal TPR domain of TOM70 as a second binding site for Orf9b, which indicates a so far unobserved contribution of chaperones in the mitochondrial targeting of the viral protein.

scholarly journals A Determinant of Sindbis Virus Neurovirulence Enables Efficient Disruption of Jak/STAT Signaling

2010 ◽  
Vol 84 (21) ◽  
pp. 11429-11439 ◽  
Author(s):  
Jason D. Simmons ◽  
Amy C. Wollish ◽  
Mark T. Heise
Keyword(s):  
Cellular Response ◽  
Sindbis Virus ◽  
Critical Role ◽  
Single Amino Acid ◽  
Type I ◽  
Type Ii ◽  
Virulence Potential ◽  
Stat Signaling ◽  
Infected Cells

ABSTRACT Previous studies with Venezuelan equine encephalitis virus and Sindbis virus (SINV) indicate that alphaviruses are capable of suppressing the cellular response to type I and type II interferons (IFNs) by disrupting Jak/STAT signaling; however, the relevance of this signaling inhibition toward pathogenesis has not been investigated. The relative abilities of neurovirulent and nonneurovirulent SINV strains to downregulate Jak/STAT signaling were compared to determine whether the ability to inhibit IFN signaling correlates with virulence potential. The adult mouse neurovirulent strain AR86 was found to rapidly and robustly inhibit tyrosine phosphorylation of STAT1 and STAT2 in response to IFN-γ and/or IFN-β. In contrast, the closely related SINV strains Girdwood and TR339, which do not cause detectable disease in adult mice, were relatively inefficient inhibitors of STAT1/2 activation. Decreased STAT activation in AR86-infected cells was associated with decreased activation of the IFN receptor-associated tyrosine kinases Tyk2, Jak1, and Jak2. To identify the viral factor(s) involved, we infected cells with several panels of AR86/Girdwood chimeric viruses. Surprisingly, we found that a single amino acid determinant, threonine at nsP1 position 538, which is required for AR86 virulence, was also required for efficient disruption of STAT1 activation, and this determinant fully restored STAT1 inhibition when it was introduced into the avirulent Girdwood background. These data indicate that a key virulence determinant plays a critical role in downregulating the response to type I and type II IFNs, which suggests that the ability of alphaviruses to inhibit Jak/STAT signaling relates to their in vivo virulence potential.

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