ATP1B3: a virus-induced host factor against EV71 replication by up-regulating the production of type-I interferons

Current status of hand-foot-and-mouth disease

Hand-foot-and-mouth disease (HFMD) is a viral illness commonly seen in young children under 5 years of age, characterized by typical manifestations such as oral herpes and rashes on the hands and feet. These symptoms typically resolve spontaneously within a few days without complications. Over the past two decades, our understanding of HFMD has greatly improved and it has received significant attention. A variety of research studies, including epidemiological, animal, and in vitro studies, suggest that the disease may be associated with potentially fatal neurological complications. These findings reveal clinical, epidemiological, pathological, and etiological characteristics that are quite different from initial understandings of the illness. It is important to note that HFMD has been linked to severe cardiopulmonary complications, as well as severe neurological sequelae that can be observed during follow-up. At present, there is no specific pharmaceutical intervention for HFMD. An inactivated Enterovirus A71 (EV-A71) vaccine that has been approved by the China Food and Drug Administration (CFDA) has been shown to provide a high level of protection against EV-A71-related HFMD. However, the simultaneous circulation of multiple pathogens and the evolution of the molecular epidemiology of infectious agents make interventions based solely on a single agent comparatively inadequate. Enteroviruses are highly contagious and have a predilection for the nervous system, particularly in child populations, which contributes to the ongoing outbreak. Given the substantial impact of HFMD around the world, this Review synthesizes the current knowledge of the virology, epidemiology, pathogenesis, therapy, sequelae, and vaccine development of HFMD to improve clinical practices and public health efforts.

Hand-Foot-and-Mouth Disease-Associated Enterovirus and the Development of Multivalent HFMD Vaccines

Hand-foot-and-mouth disease (HFMD) is an infectious disease of children caused by more than 20 types of enteroviruses, with most cases recovering spontaneously within approximately one week. Severe HFMD in individual children develops rapidly, leading to death, and is associated with other complications such as viral myocarditis and type I diabetes mellitus. The approval and marketing of three inactivated EV-A71 vaccines in China in 2016 have provided a powerful tool to curb the HFMD epidemic but are limited in cross-protecting against other HFMD-associated enteroviruses. This review focuses on the epidemiological analysis of HFMD-associated enteroviruses since the inactivated EV-A71 vaccine has been marketed, collates the progress in the development of multivalent enteroviruses vaccines in different technical routes reported in recent studies, and discusses issues that need to be investigated for safe and effective HFMD multivalent vaccines.

ATP5B Is an Essential Factor for Hepatitis B Virus Entry

Elucidation of the factors responsible for hepatitis B virus (HBV) is extremely important in order to understand the viral life cycle and pathogenesis, and thereby explore potential anti-HBV drugs. The recent determination that sodium taurocholate co-transporting peptide (NTCP) is an essential molecule for the HBV entry into cells led to the development of an HBV infection system in vitro using a human hepatocellular carcinoma (HCC) cell line expressing NTCP; however, the precise mechanism of HBV entry is still largely unknown, and thus it may be necessary to elucidate all the molecules involved. Here, we identified ATP5B as another essential factor for HBV entry. ATP5B was expressed on the cell surface of the HCC cell lines and bound with myristoylated but not with non-myristoylated preS1 2-47, which supported the notion that ATP5B is involved in the HBV entry process. Knockdown of ATP5B in NTCP-expressing HepG2 cells, which allowed HBV infection, reduced HBV infectivity with less cccDNA formation. Taken together, these results strongly suggested that ATP5B is an essential factor for HBV entry into the cells.

Inhibition of viral suppressor of RNAi proteins by designer peptides protects from enteroviral infection in vivo

RNA interference (RNAi) is the major antiviral mechanism in plants and invertebrates, but the absence of detectable viral (v)siRNAs in mammalian cells upon viral infection has questioned the functional relevance of this pathway in mammalian immunity. We designed a series of peptides specifically targeting enterovirus A71 (EV-A71)-encoded protein 3A, a viral suppressor of RNAi (VSR). These peptides abrogated the VSR function of EV-A71 in infected cells and resulted in the accumulation of vsiRNAs and reduced viral replication. These vsiRNAs were functional, as evidenced by RISC-loading and silencing of target RNAs. The effects of VSR-targeting peptides (VTPs) on infection with EV-A71 as well as another enterovirus, Coxsackievirus-A16, were ablated upon deletion of Dicer1 or AGO2, core components of the RNAi pathway. In vivo, VTP treatment protected mice against lethal EV-A71 challenge, with detectable vsiRNAs. Our findings provide evidence for the functional relevance of RNAi in mammalian immunity and present a therapeutic strategy for infectious disease.

Covid-19 and development of heart failure: mystery and truth

Coronavirus disease 2019 (Covid-19) is a novel worldwide pandemic caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). During Covid-19 pandemic, socioeconomic deprivation, social isolation, and reduced physical activities may induce heart failure (HF), destabilization, and cause more complications. HF appears as a potential hazard due to SARS-CoV-2 infection, chiefly in elderly patients with underlying comorbidities. In reality, the expression of cardiac ACE2 is implicated as a target point for SARS-CoV-2-induced acute cardiac injury. In SARS-CoV-2 infection, like other febrile illnesses, high blood viscosity, exaggerated pro-inflammatory response, multisystem inflammatory syndrome, and endothelial dysfunction-induced coagulation disorders may increase risk of HF development. Hypoxic respiratory failure, as in pulmonary edema, severe acute lung injury (ALI), and acute respiratory distress syndrome (ARDS) may affect heart hemodynamic stability due to the development of pulmonary hypertension. Indeed, Covid-19-induced HF could be through the development of cytokine storm, characterized by high proliferation pro-inflammatory cytokines. In cytokine storm-mediated cardiac dysfunction, there is a positive correlation between levels of pro-inflammatory cytokine and myocarditis-induced acute cardiac injury biomarkers. Therefore, Covid-19-induced HF is more complex and related from a molecular background in releasing pro-inflammatory cytokines to the neuro-metabolic derangements that together affect cardiomyocyte functions and development of HF. Anti-heart failure medications, mainly digoxin and carvedilol, have potent anti-SARS-CoV-2 and anti-inflammatory properties that may mitigate Covid-19 severity and development of HF. In conclusion, SARS-CoV-2 infection may lead to the development of HF due to direct acute cardiac injury or through the development of cytokine storms, which depress cardiomyocyte function and cardiac contractility. Anti-heart failure drugs, mainly digoxin and carvedilol, may attenuate severity of HF by reducing the infectivity of SARS-CoV-2 and prevent the development of cytokine storms in severely affected Covid-19 patients.

DEAD-Box Helicase DDX6 Facilitated RIG-I-Mediated Type-I Interferon Response to EV71 Infection

Previous studies have shown that DEAD (Glu-Asp-Ala-Glu)-box RNA helicases play important roles in viral infection, either as cytosolic sensors of pathogenic molecules or as essential host factors against viral infection. In the current study, we found that DDX6, an RNA helicase belonging to the DEAD-box family of helicase, exhibited anti-Enterovirus 71 activity through augmenting RIG-I-mediated type-I IFN response. Moreover, DDX6 binds viral RNA to form an RNA-protein complex to positively regulate the RIG-I-mediated interferon response; however, EV71 has evolved a strategy to antagonize the antiviral effect of DDX6 by proteolytic degradation of the molecule through its non-structural protein 2A, a virus-encoded protease.

Effects of glycyrrhizin on the growth cycle and ATPase activity of PRRSV-2-infected MARC-145 cells

Porcine reproductive and respiratory syndrome (PRRS) is a viral infectious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV) and is devastating the swine industry. MARC-145 cells, an African green monkey kidney cell line, are sensitive to PRRSV-2, and are often used for in vitro studies on PRRSV-2. Preliminary research has shown that glycyrrhizin, an important active component extracted from traditional Chinese medicinal licorice, significantly inhibits the proliferation of PRRSV-2 in MARC-145 cells; however, the in-depth molecular mechanism remains unclear. By determining the cell growth cycle, this study found that PRRSV-2 infection first increased the content of G1-phase MARC-145 cells and then decreased the content of G1-phase cells. Moreover, glycyrrhizin affected the role of PRRSV-2 in regulating the cell cycle. Furthermore, PRRSV-2 had the highest proliferation titer in G0/G1-phase MARC-145 cells, and glycyrrhizin reduced the content of PRRSV-2 in synchronized MARC-145 cells. According to the results of ATPase detection, PRRSV-2 infection weakened the Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase activities in MARC-145 cells, while glycyrrhizin significantly enhanced their activities in PRRSV-2-infected MARC-145 cells. The above results provide theoretical support toward clarifying the mechanism by which glycyrrhizin inhibits the proliferation of PRRSV-2 in MARC-145 cells. Moreover, these results offer references for the development and use of glycyrrhizin and the clinical treatment of PRRSV-2 infection.

Picornaviruses: A View from 3A

Picornaviruses are comprised of a positive-sense RNA genome surrounded by a protein shell (or capsid). They are ubiquitous in vertebrates and cause a wide range of important human and animal diseases. The genome encodes a single large polyprotein that is processed to structural (capsid) and non-structural proteins. The non-structural proteins have key functions within the viral replication complex. Some, such as 3D^pol (the RNA dependent RNA polymerase) have conserved functions and participate directly in replicating the viral genome, whereas others, such as 3A, have accessory roles. The 3A proteins are highly divergent across the Picornaviridae and have specific roles both within and outside of the replication complex, which differ between the different genera. These roles include subverting host proteins to generate replication organelles and inhibition of cellular functions (such as protein secretion) to influence virus replication efficiency and the host response to infection. In addition, 3A proteins are associated with the determination of host range. However, recent observations have challenged some of the roles assigned to 3A and suggest that other viral proteins may carry them out. In this review, we revisit the roles of 3A in the picornavirus life cycle. The 3AB precursor and mature 3A have distinct functions during viral replication and, therefore, we have also included discussion of some of the roles assigned to 3AB.

ATP1B3 Restricts Hepatitis B Virus Replication Via Reducing the Expression of the Envelope Proteins

Our recent study reported that ATP1B3 inhibits hepatitis B virus (HBV) replication via inducing NF-κB activation. However, ATP1B3 mutants which were defective in NF-κB activation still maintained the moderate degree of suppression on HBV replication, suggesting that another uncharacterized mechanism is also responsible for ATP1B3-mediated HBV suppression. Here, we demonstrated that ATP1B3 reduced the expression of HBV envelope proteins LHBs, MHBs and SHBs, but had no effect on intracellular HBV DNA, RNA levels as well as HBV promoter activities. Further investigation showed that proteasome inhibitor MG132 rescued ATP1B3-mediated envelope proteins degradation, demonstrating that proteasome-dependent pathway is involved in ATP1B3-induced degradation of envelope proteins. Co-IP showed that ATP1B3 interacts with LHBs and MHBs and induces LHBs and MHBs polyubiquitination. Immunofluorescence co-localization analysis confirmed LHBs and MHBs colocalized with ATP1B3 together. Our work provides important information for targeting ATP1B3 as a potential therapeutic molecule for HBV infection.

ATP1B3 cooperates with BST-2 to promote hepatitis B virus restriction

Increasing evidence indicates ATP1B3, one of the regulatory subunits of Na⁺ /K⁺ -ATPase, is involved in numerous viral propagations, such as HIV and EV71. However, the function and mechanism of ATP1B3 on hepatitis B virus (HBV) propagation is unknown. Here, we demonstrated that ATP1B3 overexpression reduced the quantity of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) in supernatants of HBV expression plasmids cotransfected HepG2 cells. Correspondingly, small interfering RNA and short hairpin RNA mediated ATP1B3 silencing promoted HBsAg and HBeAg expression in the supernatants of HBV expression plasmids transfected HepG2 cells. Mechanically, we reported that ATP1B3 expression could activate nuclear factor-κB (NF-κB) pathway by inducing the expression, phosphorylation, and nuclear import of P65 for the first time. And NF-κB inhibitor (Bay11) impaired the restraint of ATP1B3 on HBV replication. This counteraction effect of Bay11 proved that ATP1B3-induced NF-κB activation was crucial for HBV restriction. Accordingly, we observed that anti-HBV factors interferon-α (IFN-α) and interleukin-6 (IL-6) production were increased in HepG2 cells after the NF-κB activation. It suggested that ATP1B3 suppressed HBsAg and HBeAg by NF-κB/IFN-α and NF-κB/IL-6 axis. Further experiments proved that ATP1B3 overexpression induced anti-HBV factor BST-2 expression by NF-κB/IFN-α axis in HepG2 cells but not HEK293T cells, and ATP1B3 silencing downregulated BST-2 messenger RNA level in HepG2 cells. As an HBV restriction factor, BST-2 cooperated with ATP1B3 to antagonize HBsAg but not HBeAg in HepG2 cells. Our work identified ATP1B3 as a novel candidate of HBV restrictor with unrevealed mechanism and we highlighted it might serve as a potential therapeutic molecule for HBV infection.

Interplay between FACT subunit SPT16 and TRIM33 can remodel chromatin at macrophage distal regulatory elements

BACKGROUND

Cell type-specific use of cis-acting regulatory elements is mediated by the combinatorial activity of transcription factors involved in lineage determination and maintenance of cell identity. In macrophages, specific transcriptional programs are dictated by the transcription factor PU.1 that primes distal regulatory elements for macrophage identities and makes chromatin competent for activity of stimuli-dependent transcription factors. Although the advances in genome-wide approaches have elucidated the functions of these macrophage-specific distal regulatory elements in transcriptional responses, chromatin structures associated with PU.1 priming and the underlying mechanisms of action of these cis-acting sequences are not characterized.

RESULTS

Here, we show that, in macrophages, FACT subunit SPT16 can bind to positioned nucleosomes directly flanking PU.1-bound sites at previously uncharacterized distal regulatory elements located near genes essential for macrophage development and functions. SPT16 can interact with the transcriptional co-regulator TRIM33 and binds to half of these sites in a TRIM33-dependent manner. Using the Atp1b3 locus as a model, we show that FACT binds to two positioned nucleosomes surrounding a TRIM33/PU.1-bound site in a region, located 35 kb upstream the Atp1b3 TSS, that interact with the Atp1b3 promoter. At this - 35 kb region, TRIM33 deficiency leads to FACT release, loss of the two positioned nucleosomes, RNA Pol II recruitment and bidirectional transcription. These modifications are associated with higher levels of FACT binding at the Atp1b3 promoter, an increase of RNA Pol II recruitment and an increased expression of Atp1b3 in Trim33^-/- macrophages.

CONCLUSIONS

Thus, sequestering of SPT16/FACT by TRIM33 at PU.1-bound distal regions might represent a new regulatory mechanism for RNA Pol II recruitment and transcription output in macrophages.

The Antiviral Effects of Na,K-ATPase Inhibition: A Minireview

Since being first described more than 60 years ago, Na,K-ATPase has been extensively studied, while novel concepts about its structure, physiology, and biological roles continue to be elucidated. Cardiac glycosides not only inhibit the pump function of Na,K-ATPase but also activate intracellular signal transduction pathways, which are important in many biological processes. Recently, antiviral effects have been described as a novel feature of Na,K-ATPase inhibition with the use of cardiac glycosides. Cardiac glycosides have been reported to be effective against both DNA viruses such as cytomegalovirus and herpes simplex and RNA viruses such as influenza, chikungunya, coronavirus, and respiratory syncytial virus, among others. Consequently, cardiac glycosides have emerged as potential broad-spectrum antiviral drugs, with the great advantage of targeting cell host proteins, which help to minimize resistance to antiviral treatments, making them a very promising strategy against human viral infections. Here, we review the effect of cardiac glycosides on viral biology and the mechanisms by which these drugs impair the replication of this array of different viruses.

Enterovirus A71 Proteins: Structure and Function

Enterovirus A71 (EV-A71) infection has grown to become a serious threat to global public health. It is one of the major causes of hand, foot, and mouth disease (HFMD) in infants and young children. EV-A71 can also infect the central nervous system (CNS) and induce diverse neurological complications, such as brainstem encephalitis, aseptic meningitis, and acute flaccid paralysis, or even death. Viral proteins play a crucial role in EV-A71 infection. Many recent studies have discussed the structure and function of EV-A71 proteins, and the findings reported will definitely aid the development of vaccines and therapeutic approaches. This article reviews the progress in the research on the structure and function of EV-A71 proteins. Available literature can provide a basis for studying the pathogenesis of EV-A71 infection in detail.

Corydaline inhibits enterovirus 71 replication by regulating COX-2 expression

Enterovirus 71 (EV71) is a huge threat to the worldwide public health and there is no approved antiviral drug for EV71-induced disease therapy. Corydaline exists antiallergic and antinociceptive activities, but the anti-EV71 activity of corydaline is still not reported. In this study, corydaline could suppress the expression of viral structural and non-structural proteins. Furthermore, corydaline inhibits EV71 replication by suppressing the COX-2 expression and the phosphorylation of JNK MAPK and P38 MAPK but not ERK MAPK in vitro. Based on these findings, corydaline could be a potential lead or supplement for the development of new anti-EV71 agents in the future.

Expression of the β3 subunit of Na+/K+-ATPase is increased in gastric cancer and regulates gastric cancer cell progression and prognosis via the PI3/AKT pathway

ATP1B3 encodes the β3 subunit of Na⁺/K⁺-ATPase and is located in the q22-23 region of chromosome 3. Na⁺/K⁺-ATPase participates in normal cellular activities but also plays a crucial role in carcinogenesis. In the present study, we found that expression of the β3 subunit of Na⁺/K⁺-ATPase was increased in human gastric cancer tissues compared with that in normal matched tissues and that this increased expression predicted a poor outcome. ATP1B3 expression was elevated at both the mRNA and protein levels in gastric cancer cell lines relative to those in a normal gastric epithelial cell line. Interestingly, ATP1B3 knockdown significantly inhibited cell proliferation, colony-formation ability, migration, and invasion and increased apoptosis in human gastric carcinoma cell lines. Additionally, knockdown induced cell cycle arrest at the G2/M phase. Furthermore, we demonstrated that ATP1B3 silencing decreased the expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and phosphorylated AKT (p-AKT), indicating that ATP1B3 regulates gastric cancer cell progression via the PI3K/AKT signalling pathway. Hence, the β3 subunit of Na⁺/K⁺-ATPase plays an essential role in the tumourigenesis of gastric cancer and may be a potential prognostic and therapeutic target for the treatment of gastric cancer.