Protein Tyrosine Phosphatase SHP2 Suppresses Host Innate Immunity against Influenza A Virus by Regulating EGFR-Mediated Signaling

Tyrosine phosphatase SHP2 accelerated ovarian cancer via modulating integrin/ E-Cadherin/ ZEB1 induced EMT

This article focusing on examining the function and further, molecular function of SHP2 in ovarian cancer (OC). For the molecular mechanism, bioinformatics was applied to study the specifically expressed genes in ovarian cancer ; the western blotting was applied to identify the EGF, p-SHP2, ZEB1, and E-Cadherin expressions in ovarian cancer tissue and pair adjacent tissue; then SKOV3 cells were treated with EGF and infected with E-Cadherin overexpression lentivirus, and then cells were treated with benzyl butyl phthalate and IRS-1 respectively. Detection of expression of p-SHP2, ZEB1, E-Cadherin, α3-integrin, p-Src, p-SMAD2, Snail, Slug and SKOV3 cells of migration and invasion abilities were detected using Western blot method and cell scratch assay and Transwell assay; Progression of ovarian cancer was detected using subcutaneous tumor transplantation assay in nude mice and HE staining method and immunocyto. The bioinformatics analysis results suggested that SHP2 is highly specifically expressed and E-Cadherin, which is low specifically expressed in ovarian cancer tissues, while EGF, p-SHP2 or ZEB1 are highly expressed and E-Cadherin is low expressed in ovarian cancer tissues; Overexpression of E-Cadherin could reduce the expressions of p-SHP2, ZEB1, α3-integrin, p-Src, p-SMAD2, Snail and Slug might has roles in alleviating the ovarian cancer development and decreasing the levels of p-SHP2 and ZEB1 in tumor samples. And E-Cadherin overexpression reduced the migration and invasion ability of SKOV3 cells. SHP2 tyrosine phosphatase enhances the ovarian cancer cells' motility and invasiveness by upregulation of the integrin/E-Cadherin switch through ZEB1 signal.

Virus versus host: influenza A virus circumvents the immune responses

Influenza A virus (IAV) is a highly contagious pathogen causing dreadful losses to humans and animals around the globe. As is known, immune escape is a strategy that benefits the proliferation of IAVs by antagonizing, blocking, and suppressing immune surveillance. The HA protein binds to the sialic acid (SA) receptor to enter the cytoplasm and initiate viral infection. The conserved components of the viral genome produced during replication, known as the pathogen-associated molecular patterns (PAMPs), are thought to be critical factors for the activation of effective innate immunity by triggering dependent signaling pathways after recognition by pattern recognition receptors (PRRs), followed by a cascade of adaptive immunity. Viral infection-induced immune responses establish an antiviral state in the host to effectively inhibit virus replication and enhance viral clearance. However, IAV has evolved multiple mechanisms that allow it to synthesize and transport viral components by "playing games" with the host. At its heart, this review will describe how host and viral factors interact to facilitate the viral evasion of host immune responses.

African swine fever virus A137R protein inhibits NF-κB activation via suppression of MyD88 signaling in PK15 and 3D4/21 cells in vitro

African swine fever (ASF) is an infectious disease with high mortality caused by African swine fever virus (ASFV), which poses a great threat to the global swine industry. ASFV has evolved multiple strategies to evade host antiviral innate immunity by perturbing inflammatory responses and interferon production. However, the molecular mechanisms underlying manipulation of inflammatory responses by ASFV proteins are not fully understood. Here, we report that A137R protein of ASFV is a key suppressor of host inflammatory responses. Ectopic expression of ASFV A137R in HEK293T cells significantly inhibited the activation of IL-8 and NF-κB promoters triggered by Sendai virus (SeV), influenza A virus (IAV), or vesicular stomatitis virus (VSV). Accordingly, forced A137R expression caused a significant decrease in the production of several inflammatory cytokines such as IL-8, IL-6 and TNF-α in the cells infected with SeV or IAV. Similar results were obtained from experiments using A137R overexpressing PK15 and 3D4/21 cells infected with SeV or VSV. Furthermore, we observed that A137R impaired the activation of MAPK and NF-κB signaling pathways, as enhanced expression of A137R significantly decreased the phosphorylation of JNK, p38 and p65 respectively upon viral infection (SeV or IAV) and IL-1β treatment. Mechanistically, we found that A137R interacted with MyD88, and dampened MyD88-mediated activation of MAPK and NF-κB signaling. Together, these findings uncover a critical role of A137R in restraining host inflammatory responses, and improve our understanding of complicated mechanisms whereby ASFV evades innate immunity.

PZR suppresses innate immune response to RNA viral infection by inhibiting MAVS activation in interferon signaling mediated by RIG-I and MDA5

RNA viral infections seriously endanger human health. Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 2 (SHP2) suppresses innate immunity against influenza A virus, and pharmacological inhibition of SHP2 provokes hepatic innate immunity. SHP2 binds and catalyzes tyrosyl dephosphorylation of protein zero-related (PZR), but the regulatory effect of PZR on innate immune response to viral infection is unclear. In this study, the transcription and protein level of PZR in host cells were found to be decreased with RNA viral infection, and high level of PZR was uncovered to inhibit interferon (IFN) signaling mediated by RIG-I and MDA5. Through localizing in mitochondria, PZR targeted and interacted with MAVS (also known as IPS-1/VISA/Cardif), suppressing the aggregation and activation of MAVS. Specifically, Y263 residue in ITIM is critical for PZR to exert immunosuppression under RNA viral infection. Moreover, the recruited SHP2 by PZR that modified with tyrosine phosphorylation under RNA viral infection might inhibit phosphorylation activation of MAVS. In conclusion, PZR and SHP2 suppress innate immune response to RNA viral infection through inhibiting MAVS activation. This study reveals the regulatory mechanism of PZR-SHP2-MAVS signal axis on IFN signaling mediated by RIG-I and MDA5, which may provide new sight for developing antiviral drugs.

Role of Virus-Induced EGFR Trafficking in Proviral Functions

Since its discovery in the early 1980s, the epidermal growth factor receptor (EGFR) has emerged as a pivotal and multifaceted player in elucidating the intricate mechanisms underlying various human diseases and their associations with cell survival, proliferation, and cellular homeostasis. Recent advancements in research have underscored the profound and multifaceted role of EGFR in viral infections, highlighting its involvement in viral entry, replication, and the subversion of host immune responses. In this regard, the importance of EGFR trafficking has also been highlighted in recent studies. The dynamic relocation of EGFR to diverse intracellular organelles, including endosomes, lysosomes, mitochondria, and even the nucleus, is a central feature of its functionality in diverse contexts. This dynamic intracellular trafficking is not merely a passive process but an orchestrated symphony, facilitating EGFR involvement in various cellular pathways and interactions with viral components. Furthermore, EGFR, which is initially anchored on the plasma membrane, serves as a linchpin orchestrating viral entry processes, a crucial early step in the viral life cycle. The role of EGFR in this context is highly context-dependent and varies among viruses. Here, we present a comprehensive summary of the current state of knowledge regarding the intricate interactions between EGFR and viruses. These interactions are fundamental for successful propagation of a wide array of viral species and affect viral pathogenesis and host responses. Understanding EGFR significance in both normal cellular processes and viral infections may not only help develop innovative antiviral therapies but also provide a deeper understanding of the intricate roles of EGFR signaling in infectious diseases.

Pathogenicity and virulence of influenza

Influenza viruses, including four major types (A, B, C, and D), can cause mild-to-severe and lethal diseases in humans and animals. Influenza viruses evolve rapidly through antigenic drift (mutation) and shift (reassortment of the segmented viral genome). New variants, strains, and subtypes have emerged frequently, causing epidemic, zoonotic, and pandemic infections, despite currently available vaccines and antiviral drugs. In recent years, avian influenza viruses, such as H5 and H7 subtypes, have caused hundreds to thousands of zoonotic infections in humans with high case fatality rates. The likelihood of these animal influenza viruses acquiring airborne transmission in humans through viral evolution poses great concern for the next pandemic. Severe influenza viral disease is caused by both direct viral cytopathic effects and exacerbated host immune response against high viral loads. Studies have identified various mutations in viral genes that increase viral replication and transmission, alter tissue tropism or species specificity, and evade antivirals or pre-existing immunity. Significant progress has also been made in identifying and characterizing the host components that mediate antiviral responses, pro-viral functions, or immunopathogenesis following influenza viral infections. This review summarizes the current knowledge on viral determinants of influenza virulence and pathogenicity, protective and immunopathogenic aspects of host innate and adaptive immune responses, and antiviral and pro-viral roles of host factors and cellular signalling pathways. Understanding the molecular mechanisms of viral virulence factors and virus-host interactions is critical for the development of preventive and therapeutic measures against influenza diseases.

Metabolomic profiling of Marek's disease virus infection in host cell based on untargeted LC-MS

Marek's disease (MD) caused by Marek's disease virus (MDV), poses a serious threat to the poultry industry by inducing neurological disease and malignant lymphoma in infected chickens. However, the underlying mechanisms how MDV disrupts host cells and causes damage still remain elusive. Recently, the application of metabolomics has shown great potential for uncovering the complex mechanisms during virus-host interactions. In this study, chicken embryo fibroblasts (CEFs) infected with MDV were subjected to ultrahigh-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS) and multivariate statistical analysis. The results showed that 261 metabolites were significantly altered upon MDV infection, with most changes occurring in amino acid metabolism, energy metabolism, nucleotide metabolism, and lipid metabolism. Notably, MDV infection induces an up-regulation of amino acids in host cells during the early stages of infection to provide the energy and intermediary metabolites necessary for efficient multiplication of its own replication. Taken together, these data not only hold promise in identifying the biochemical molecules utilized by MDV replication in host cells, but also provides a new insight into understanding MDV-host interactions.

EGF receptor modulates HEV entry in human hepatocytes

BACKGROUND AND AIMS

Being the most common cause of acute viral hepatitis with >20 million cases per year and 70,000 deaths annually, HEV presents a long-neglected and underinvestigated health burden. Although the entry process of viral particles is an attractive target for pharmacological intervention, druggable host factors to restrict HEV entry have not been identified so far.

APPROACH AND RESULTS

Here we identify the EGF receptor (EGFR) as a novel host factor for HEV and reveal the significance of EGFR for the HEV entry process. By utilizing RNAi, chemical modulation with Food and Drug Administration-approved drugs, and ectopic expression of EGFR, we revealed that EGFR is critical for HEV infection without affecting HEV RNA replication or assembly of progeny virus. We further unveiled that EGFR itself and its ligand-binding domain, rather than its signaling function, is responsible for the proviral effect. Modulation of EGF expression in HepaRG cells and primary human hepatocytes affected HEV infection.

CONCLUSIONS

Taken together, our study provides novel insights into the life cycle of HEV and identified EGFR as a possible target for future antiviral strategies against HEV.

The Immunosuppressive Roles of PD-L1 during Influenza A Virus Infection

The clinical benefits of targeting programmed death-ligand 1 (PD-L1) in various cancers represent a strategy for the treatment of immunosuppressive diseases. Here, it was demonstrated that the expression levels of PD-L1 in cells were greatly upregulated in response to H1N1 influenza A virus (IAV) infection. Overexpression of PD-L1 promoted viral replication and downregulated type-I and type-III interferons and interferon-stimulated genes. Moreover, the association between PD-L1 and Src homology region-2, containing protein tyrosine phosphatase (SHP2), during IAV/H1N1 infection was analyzed by employing the SHP2 inhibitor (SHP099), siSHP2, and pNL-SHP2. The results showed that the expressions of PD-L1 mRNA and protein were decreased under SHP099 or siSHP2 treatment, whereas the cells overexpressing SHP2 exhibited the opposite effects. Additionally, the effects of PD-L1 on the expression of p-ERK and p-SHP2 were investigated in PD-L1-overexpressed cells following WSN or PR8 infection, determining that the PD-L1 overexpression led to the decreased expression of p-SHP2 and p-ERK induced by WSN or PR8 infection. Taken together, these data reveal that PD-L1 could play an important role in immunosuppression during IAV/H1N1 infection; thus, it may serve as a promising therapeutic target for development of novel anti-IAV drugs.

Upregulation of galectin-3 in influenza A virus infection promotes viral RNA synthesis through its association with viral PA protein

BACKGROUND

Influenza is one of the most important viral infections globally. Viral RNA-dependent RNA polymerase (RdRp) consists of the PA, PB1, and PB2 subunits, and the amino acid residues of each subunit are highly conserved among influenza A virus (IAV) strains. Due to the high mutation rate and emergence of drug resistance, new antiviral strategies are needed. Host cell factors are involved in the transcription and replication of influenza virus. Here, we investigated the role of galectin-3, a member of the β-galactoside-binding animal lectin family, in the life cycle of IAV infection in vitro and in mice.

METHODS

We used galectin-3 knockout and wild-type mice and cells to study the intracellular role of galectin-3 in influenza pathogenesis. Body weight and survival time of IAV-infected mice were analyzed, and viral production in mouse macrophages and lung fibroblasts was examined. Overexpression and knockdown of galectin-3 in A549 human lung epithelial cells were exploited to assess viral entry, viral ribonucleoprotein (vRNP) import/export, transcription, replication, virion production, as well as interactions between galectin-3 and viral proteins by immunoblotting, immunofluorescence, co-immunoprecipitation, RT-qPCR, minireplicon, and plaque assays. We also employed recombinant galectin-3 proteins to identify specific step(s) of the viral life cycle that was affected by exogenously added galectin-3 in A549 cells.

RESULTS

Galectin-3 levels were increased in the bronchoalveolar lavage fluid and lungs of IAV-infected mice. There was a positive correlation between galectin-3 levels and viral loads. Notably, galectin-3 knockout mice were resistant to IAV infection. Knockdown of galectin-3 significantly reduced the production of viral proteins and virions in A549 cells. While intracellular galectin-3 did not affect viral entry, it increased vRNP nuclear import, RdRp activity, and viral transcription and replication, which were associated with the interaction of galectin-3 with viral PA subunit. Galectin-3 enhanced the interaction between viral PA and PB1 proteins. Moreover, exogenously added recombinant galectin-3 proteins also enhanced viral adsorption and promoted IAV infection in A549 cells.

CONCLUSION

We demonstrate that galectin-3 enhances viral infection through increases in vRNP nuclear import and RdRp activity, thereby facilitating viral transcription and replication. Our findings also identify galectin-3 as a potential therapeutic target for influenza.

FDA-Approved Inhibitors of RTK/Raf Signaling Potently Impair Multiple Steps of In Vitro and Ex Vivo Influenza A Virus Infections

Influenza virus (IV) infections pose a burden on global public health with significant morbidity and mortality. The limited range of currently licensed IV antiviral drugs is susceptible to the rapid rise of resistant viruses. In contrast, FDA-approved kinase inhibitors can be repurposed as fast-tracked host-targeted antivirals with a higher barrier of resistance. Extending our recent studies, we screened 21 FDA-approved small-molecule kinase inhibitors (SMKIs) and identified seven candidates as potent inhibitors of pandemic and seasonal IV infections. These SMKIs were further validated in a biologically and clinically relevant ex vivo model of human precision-cut lung slices. We identified steps of the virus infection cycle affected by these inhibitors (entry, replication, egress) and found that most SMKIs affected both entry and egress. Based on defined and overlapping targets of these inhibitors, the candidate SMKIs target receptor tyrosine kinase (RTK)-mediated activation of Raf/MEK/ERK pathways to limit influenza A virus infection. Our data and the established safety profiles of these SMKIs support further clinical investigations and repurposing of these SMKIs as host-targeted influenza therapeutics.

RNA Sequencing Demonstrates That Circular RNA Regulates Avian Influenza Virus Replication in Human Cells

Circular RNAs (circRNAs) are involved in diverse biological processes. Avian influenza virus (AIV) can cross the species barrier to infect humans. Here, we employed RNA sequencing technology to profile circRNA, microRNA, and mRNA expression in human lung carcinoma cells in response to AIV or human influenza A virus (IAV) infection at viral replication. The analysis revealed that the expression of 475 common circRNAs were significantly regulated. The 381 and 1163 up-regulated circRNAs were induced by AIV at 8 and 16 h, respectively. Subsequently, gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses were also conducted for the AIV-specific up-regulated circRNAs. Moreover, the circRNAs were characterized, of which six were verified by quantitative real-time PCR. We further confirmed that expression of the selected circRNAs only increased following AIV infection. Knocking down the selected circRNAs promoted AIV proliferation, and overexpression of three of the candidate circRNAs restricted AIV replication and proliferation. We further analyzed that AIV-specific up-regulated circRNA mechanisms might function through the ceRNA network to affect the “Endocytosis” pathway and the “Cell cycle process”. These data provide the first expression profile of AIV-specific up-regulated circRNAs and shed new light on the pathogenesis of AIV infection. Our findings also suggest that these circRNAs serve an important role in AIV infection.

EGFR Activation Impairs Antiviral Activity of Interferon Signaling in Brain Microvascular Endothelial Cells During Japanese Encephalitis Virus Infection

The establishment of Japanese encephalitis virus (JEV) infection in brain microvascular endothelial cells (BMECs) is thought to be a critical step to induce viral encephalitis with compromised blood–brain barrier (BBB), and the mechanisms involved in this process are not completely understood. In this study, we found that epidermal growth factor receptor (EGFR) is related to JEV escape from interferon-related host innate immunity based on a STRING analysis of JEV-infected primary human brain microvascular endothelial cells (hBMECs) and mouse brain. At the early phase of the infection processes, JEV induced the phosphorylation of EGFR. In JEV-infected hBMECs, a rapid internalization of EGFR that co-localizes with the endosomal marker EEA1 occurred. Using specific inhibitors to block EGFR, reduced production of viral particles was observed. Similar results were also found in an EGFR-KO hBMEC cell line. Even though the process of viral infection in attachment and entry was not noticeably influenced, the induction of IFNs in EGFR-KO hBMECs was significantly increased, which may account for the decreased viral production. Further investigation demonstrated that EGFR downstream cascade ERK, but not STAT3, was involved in the antiviral effect of IFNs, and a lowered viral yield was observed by utilizing the specific inhibitor of ERK. Taken together, the results revealed that JEV induces EGFR activation, leading to a suppression of interferon signaling and promotion of viral replication, which could provide a potential target for future therapies for the JEV infection.

Dependency of EGFR activation in vanadium-based sensitization to oncolytic virotherapy

Oncolytic virotherapy is a clinically validated approach to treat cancers such as melanoma; however, tumor resistance to virus makes its efficacy variable. Compounds such as sodium orthovanadate (vanadate) can overcome viral resistance and synergize with RNA-based oncolytic viruses. In this study, we explored the basis of vanadate mode of action and identified key cellular components in vanadate’s oncolytic virus-enhancing mechanism using a high-throughput kinase inhibitor screen. We found that several kinase inhibitors affecting signaling downstream of the epidermal growth factor receptor (EGFR) pathway abrogated the oncolytic virus-enhancing effects of vanadate. EGFR pathway inhibitors such as gefitinib negated vanadate-associated changes in the phosphorylation and localization of STAT1/2 as well as NF-κB signaling. Moreover, gefitinib treatment could abrogate the viral sensitizing response of vanadium compounds in vivo. Together, we demonstrate that EGFR signaling plays an integral role in vanadium viral sensitization and that pharmacological EGFR blockade can counteract vanadium/oncolytic virus combination therapy.

Syk Facilitates Influenza A Virus Replication by Restraining Innate Immunity at the Late Stage of Viral Infection

Spleen tyrosine kinase (Syk) has recently come forth as a critical regulator of innate immune response. Previous studies identify Syk as a key kinase for STAT1 activation at the early stage of influenza A virus (IAV) infection that is involved in initial antiviral immunity. However, the involvement of Syk in host antiviral immunity during the late phase of IAV infection and its effect on pathogenesis of the virus remain unknown. Here, we found through time course studies that Syk restrained antiviral immune response at the late stage of IAV infection, thereby promoting viral replication. Depletion of Syk suppressed IAV replication in vitro, whereas ectopic expression of Syk facilitated viral replication. Moreover, Syk-deficient mice were employed, and we observed that knockout of Syk rendered mice more resistant to IAV infection, as evidenced by a lower degree of lung injury, slower body weight loss, and an increased survival rate of Syk knockout mice challenged with IAV. Furthermore, we revealed that Syk repressed the interferon response at the late stage of viral infection. Loss of Syk potentiated the expression of type I and III interferons in both Syk-depleted cells and mice. Mechanistically, Syk interacted with TBK1 and modulated its phosphorylation status, thereby impeding TBK1 activation and restraining innate immune signaling that governs interferon response. Together, these findings unveil a role of Syk in temporally regulating host antiviral immunity and advance our understanding of complicated mechanisms underlying regulation of innate immunity against viral invasion. IMPORTANCE Innate immunity must be tightly controlled to eliminate invading pathogens while avoiding autoimmune or inflammatory diseases. Syk is essential for STAT1 activation at the early stage of IAV infection, which is critical for initial antiviral responses. Surprisingly, here a time course study showed that Syk suppressed innate immunity during late phases of IAV infection and thereby promoted IAV replication. Syk deficiency enhanced the expression of type I and III interferons, inhibited IAV replication, and rendered mice more resistant to IAV infection. Syk impaired innate immune signaling through impeding TBK1 activation. These data reveal that Syk participates in the initiation of antiviral defense against IAV infection and simultaneously contributes to the restriction of innate immunity at the late stage of viral infection, suggesting that Syk serves a dual function in regulating antiviral responses. This finding provides new insights into complicated mechanisms underlying interaction between virus and host immune system.

I226R Protein of African Swine Fever Virus Is a Suppressor of Innate Antiviral Responses

African swine fever is one of the most devastating swine diseases caused by African swine fever virus (ASFV). Although ASFV encodes more than 160 viral proteins, the implication of a majority of ASFV proteins in regulating host immunity is yet to be explored, and the mechanisms of immune evasion by ASFV proteins are largely unknown. Here, we report that the I226R protein of ASFV significantly suppressed innate immune responses. The ectopic expression of ASFV I226R in 293T cells significantly inhibited the activation of interferon-stimulated response element promoters triggered by Sendai virus (SeV), poly(I:C), or cyclic GMP-AMP synthase (cGAS)/STING. The I226R protein caused a significant decrease in the expression of interferons and interferon-stimulating genes in cells infected with SeV. Similar results were obtained from experiments using I226R-overexpressed PK15 and 3D4/21 cells stimulated with vesicular stomatitis virus. We observed that I226R inhibited the activation of both nuclear factor-kappa B (NF-κB) and interferon regulatory factor 3 (IRF3). Furthermore, it was shown that overexpression of I226R suppressed IRF3 activation and caused the degradation of NF-κB essential modulator (NEMO) protein. The I226R-induced NEMO degradation could be prevented by treatment with MG132, a proteasome inhibitor. Together, these results reveal that the ASFV I226R protein impairs antiviral responses, likely through multiple mechanisms including the suppression of NF-κB and IRF3 activation, to counteract innate immune responses during the viral infection.

Novel insights into the pathogenesis of virus-induced ARDS: review on the central role of the epithelial-endothelial barrier

Introduction: Respiratory viruses can directly or indirectly damage the pulmonary defense barrier, potentially contributing to acute respiratory distress syndrome (ARDS). Despite developments in the understanding of the pathogenesis of ARDS, the underlying pathophysiology still needs to be elucidated.Areas covered: The PubMed database was reviewed for relevant papers published up to 2021. This review summarizes the currently immunological and clinical studies to provide a systemic overview of the epithelial-endothelial barrier, given the recently published immunological profiles upon viral pneumonia, and the potentially detrimental contribution to respiratory function caused by damage to this barrier.Expert opinion: The biophysical structure of host pulmonary defense is intrinsically linked with the ability of alveolar epithelial and capillary endothelial cells, known as the epithelial-endothelial barrier, to respond to, and instruct the delicate immune system to protect the lungs from infections and injuries. Recently published immunological profiles upon viral infection, and its contributions to the damage of respiratory function, suggest a central role for the pulmonary epithelial and endothelial barrier in the pathogenesis of ARDS. We suggest a central role and common pathways by which the epithelial-endothelial barrier contributes to the pathogenesis of ARDS.