scholarly journals Roles of the Endogenous Lunapark Protein during Flavivirus Replication

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1198
Author(s):  
Pham-Tue-Hung Tran ◽  
Naveed Asghar ◽  
Magnus Johansson ◽  
Wessam Melik
Keyword(s):  
Virus Replication ◽  
Nonstructural Protein ◽  
Host Factors ◽  
Membrane Remodeling ◽  
Biochemical Assays ◽  
Langat Virus ◽  
Underlying Mechanisms ◽  
Flavivirus Infection ◽  
Curved Membrane ◽  
High Resolution Microscopy

The endoplasmic reticulum (ER) of eukaryotic cells is a dynamic organelle, which undergoes continuous remodeling. At the three-way tubular junctions of the ER, the lunapark (LNP) protein acts as a membrane remodeling factor to stabilize these highly curved membrane junctions. In addition, during flavivirus infection, the ER membrane is invaginated to form vesicles (Ve) for virus replication. Thus, LNP may have roles in the generation or maintenance of the Ve during flavivirus infection. In this study, our aim was to characterize the functions of LNP during flavivirus infection and investigate the underlying mechanisms of these functions. To specifically study virus replication, we generated cell lines expressing replicons of West Nile virus (Kunjin strain) or Langat virus. By using these replicon platforms and electron microscopy, we showed that depletion of LNP resulted in reduced virus replication, which is due to its role in the generation of the Ve. By using biochemical assays and high-resolution microscopy, we found that LNP is recruited to the Ve and the protein interacts with the nonstructural protein (NS) 4B. Therefore, these data shed new light on the interactions between flavivirus and host factors during viral replication.

scholarly journals Potential Phosphorylation of Viral Nonstructural Protein 1 in Dengue Virus Infection

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1393
Author(s):  
Thanyaporn Dechtawewat ◽  
Sittiruk Roytrakul ◽  
Yodying Yingchutrakul ◽  
Sawanya Charoenlappanit ◽  
Bunpote Siridechadilok ◽  
...  
Keyword(s):  
Dengue Virus ◽  
Nonstructural Protein ◽  
Antiviral Drug ◽  
Denv Infection ◽  
Site Directed Mutagenesis ◽  
Phosphorylation Sites ◽  
Post Translational Modification ◽  
Multifunctional Protein ◽  
Nonstructural Protein 1 ◽  
Underlying Mechanisms

Dengue virus (DENV) infection causes a spectrum of dengue diseases that have unclear underlying mechanisms. Nonstructural protein 1 (NS1) is a multifunctional protein of DENV that is involved in DENV infection and dengue pathogenesis. This study investigated the potential post-translational modification of DENV NS1 by phosphorylation following DENV infection. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), 24 potential phosphorylation sites were identified in both cell-associated and extracellular NS1 proteins from three different cell lines infected with DENV. Cell-free kinase assays also demonstrated kinase activity in purified preparations of DENV NS1 proteins. Further studies were conducted to determine the roles of specific phosphorylation sites on NS1 proteins by site-directed mutagenesis with alanine substitution. The T27A and Y32A mutations had a deleterious effect on DENV infectivity. The T29A, T230A, and S233A mutations significantly decreased the production of infectious DENV but did not affect relative levels of intracellular DENV NS1 expression or NS1 secretion. Only the T230A mutation led to a significant reduction of detectable DENV NS1 dimers in virus-infected cells; however, none of the mutations interfered with DENV NS1 oligomeric formation. These findings highlight the importance of DENV NS1 phosphorylation that may pave the way for future target-specific antiviral drug design.

scholarly journals Potential Dual Role of West Nile Virus NS2B in Orchestrating NS3 Enzymatic Activity in Viral Replication

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 216
Author(s):  
Alanna C. Tseng ◽  
Vivek R. Nerurkar ◽  
Kabi R. Neupane ◽  
Helmut Kae ◽  
Pakieli H. Kaufusi
Keyword(s):  
West Nile Virus ◽  
Enzymatic Activity ◽  
Nonstructural Protein ◽  
Antiviral Drug ◽  
West Nile ◽  
Biochemical Assays ◽  
In Trans ◽  
Viral Polyprotein ◽  
Ns3 Protease

West Nile virus (WNV) nonstructural protein 3 (NS3) harbors the viral triphosphatase and helicase for viral RNA synthesis and, together with NS2B, constitutes the protease responsible for polyprotein processing. NS3 is a soluble protein, but it is localized to specialized compartments at the rough endoplasmic reticulum (RER), where its enzymatic functions are essential for virus replication. However, the mechanistic details behind the recruitment of NS3 from the cytoplasm to the RER have not yet been fully elucidated. In this study, we employed immunofluorescence and biochemical assays to demonstrate that NS3, when expressed individually and when cleaved from the viral polyprotein, is localized exclusively to the cytoplasm. Furthermore, NS3 appeared to be peripherally recruited to the RER and proteolytically active when NS2B was provided in trans. Thus, we provide evidence for a potential additional role for NS2B in not only serving as the cofactor for the NS3 protease, but also in recruiting NS3 from the cytoplasm to the RER for proper enzymatic activity. Results from our study suggest that targeting the interaction between NS2B and NS3 in disrupting the NS3 ER localization may be an attractive avenue for antiviral drug discovery.

scholarly journals Foot‐and‐mouth disease virus nonstructural protein 2B interacts with cyclophilin A, modulating virus replication

2018 ◽  
Vol 32 (12) ◽  
pp. 6706-6723 ◽  
Author(s):  
Huisheng Liu ◽  
Qiao Xue ◽  
Weijun Cao ◽  
Fan Yang ◽  
Linna Ma ◽  
...  
Keyword(s):  
Disease Virus ◽  
Virus Replication ◽  
Nonstructural Protein ◽  
Foot And Mouth Disease ◽  
Cyclophilin A ◽  
Mouth Disease ◽  
Mouth Disease Virus ◽  
Foot And Mouth

scholarly journals A Combined Genetic-Proteomic Approach Identifies Residues within Dengue Virus NS4B Critical for Interaction with NS3 and Viral Replication

2015 ◽  
Vol 89 (14) ◽  
pp. 7170-7186 ◽  
Author(s):  
Laurent Chatel-Chaix ◽  
Wolfgang Fischl ◽  
Pietro Scaturro ◽  
Mirko Cortese ◽  
Stephanie Kallis ◽  
...  
Keyword(s):  
Amino Acid ◽  
Dengue Virus ◽  
Virus Replication ◽  
Strong Evidence ◽  
Drug Target ◽  
Nonstructural Protein ◽  
Rna Replication ◽  
Replication Cycle ◽  
Infected Cells ◽  
Ns3 Protease

ABSTRACTDengue virus (DENV) infection causes the most prevalent arthropod-borne viral disease worldwide. Approved vaccines are not available, and targets suitable for the development of antiviral drugs are lacking. One possible drug target is nonstructural protein 4B (NS4B), because it is absolutely required for virus replication; however, its exact role in the DENV replication cycle is largely unknown. With the aim of mapping NS4B determinants critical for DENV replication, we performed a reverse genetic screening of 33 NS4B mutants in the context of an infectious DENV genome. While the majority of these mutations were lethal, for several of them, we were able to select for second-site pseudoreversions, most often residing in NS4B and restoring replication competence. To identify all viral NS4B interaction partners, we engineered a fully viable DENV genome encoding an affinity-tagged NS4B. Mass spectrometry-based analysis of the NS4B complex isolated from infected cells identified the NS3 protease/helicase as a major interaction partner of NS4B. By combining the genetic complementation map of NS4B with a replication-independent expression system, we identified the NS4B cytosolic loop—more precisely, amino acid residue Q134—as a critical determinant for NS4B-NS3 interaction. An alanine substitution at this site completely abrogated the interaction and DENV RNA replication, and both were restored by pseudoreversions A69S and A137V. This strict correlation between the degree of NS4B-NS3 interaction and DENV replication provides strong evidence that this viral protein complex plays a pivotal role during the DENV replication cycle, hence representing a promising target for novel antiviral strategies.IMPORTANCEWith no approved therapy or vaccine against dengue virus infection, the viral nonstructural protein 4B (NS4B) represents a possible drug target, because it is indispensable for virus replication. However, little is known about its precise structure and function. Here, we established the first comprehensive genetic interaction map of NS4B, identifying amino acid residues that are essential for virus replication, as well as second-site mutations compensating for their defects. Additionally, we determined the NS4B viral interactome in infected cells and identified the NS3 protease/helicase as a major interaction partner of NS4B. We mapped residues in the cytosolic loop of NS4B as critical determinants for interaction with NS3, as well as RNA replication. The strong correlation between NS3-NS4B interaction and RNA replication provides strong evidence that this complex plays a pivotal role in the viral replication cycle, hence representing a promising antiviral drug target.

scholarly journals Role for TBC1D20 and Rab1 in Hepatitis C Virus Replication via Interaction with Lipid Droplet-Bound Nonstructural Protein 5A

2012 ◽  
Vol 86 (12) ◽  
pp. 6491-6502 ◽  
Author(s):  
I. Nevo-Yassaf ◽  
Y. Yaffe ◽  
M. Asher ◽  
O. Ravid ◽  
S. Eizenberg ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Virus Replication ◽  
Lipid Droplet ◽  
Nonstructural Protein ◽  
Nonstructural Protein 5A

shRNA targeting nonstructural protein inhibits the replication of severe fever with thrombocytopenia syndrome virus

2021 ◽  
Author(s):  
Lili Dou ◽  
Xiaoli Tao ◽  
Wei Zhao ◽  
Guofeng Zheng ◽  
Ying Lu ◽  
...  
Keyword(s):  
Tissue Culture ◽  
Western Blotting ◽  
Virus Replication ◽  
Nonstructural Protein ◽  
Vero Cells ◽  
Antiviral Effects ◽  
Infective Dose ◽  
Shrna Plasmid ◽  
Dose Dependent ◽  
Severe Fever

Aim: To explore whether shRNA targeting nonstructural protein (NSs) of severe fever with thrombocytopenia syndrome virus (SFTSV) could inhibit SFTSV replication in Vero cells. Materials & methods: SFTSV used in this experiment was propagated in Vero cells and stored at -20°C. shRNA plasmid against NSs of SFTSV was transfected to Vero cells and infected with SFTSV, after which western blotting and tissue culture infective dose (TCID50) were used to measure the virus titers. Results: shRNA against NSs protein decreased the expression of NSs and inhibited the replication of SFTSV. Conclusion: The constructed SFTSV NSs-shRNA plasmid could inhibit the replication of SFTSV. It was concluded that SFTSV NSs-shRNA could inhibit virus replication for at least 72 h. shRNA-mediated antiviral effects were dose-dependent.

The balance between p53 isoforms modulates the efficiency of HIV-1 infection in macrophages

2021 ◽  
Author(s):  
Yann Breton ◽  
Corinne Barat ◽  
Michel J. Tremblay
Keyword(s):  
Virus Replication ◽  
Potential Role ◽  
Host Factors ◽  
Fine Tuning ◽  
Mrna Levels ◽  
Cellular Environment ◽  
P53 Isoforms ◽  
Antiviral Role ◽  
Hiv 1

Several host factors influence HIV-1 infection and replication. The p53-mediated antiviral role in monocytes-derived macrophages (MDMs) was previously highlighted. Indeed, an increase in p53 level results in a stronger restriction against HIV-1 early replication steps through SAMHD1 activity. In this study, we investigated the potential role of some p53 isoforms in HIV-1 infection. Transfection of isoform-specific siRNA induces distinctive effects on the virus life cycle. For example, in contrast to a siRNA targeting all isoforms, a knockdown of Δ133p53 transcripts reduces virus replication in MDMs that is correlated with a decrease in phosphorylated inactive SAMHD1. Combination of Δ133p53 knockdown and Nutlin-3, a pharmacological inhibitor of MDM2 that stabilizes p53, further reduces susceptibility of MDMs to HIV-1 infection, thus suggesting an inhibitory role of Δ133p53 towards p53 antiviral activity. In contrast, p53β knockdown in MDMs increases the viral production independently of SAMHD1. Moreover, experiments with a Nef-deficient virus show that this viral protein plays a protective role against the antiviral environment mediated by p53. Finally, HIV-1 infection affects the expression pattern of p53 isoforms by increasing p53β and p53γ mRNA levels while stabilizing the protein level of p53α and some isoforms from the p53β subclass. The balance between the various p53 isoforms is therefore an important factor in the overall susceptibility of macrophages to HIV-1 infection, fine-tuning the p53 response against HIV-1. This study brings a new understanding of the complex role of p53 in virus replication processes in myeloid cells. Importance As of today, HIV-1 is still considered as a global pandemic without a functional cure, partly because of the presence of stable viral reservoirs. Macrophages constitute one of these cell reservoirs, contributing to the viral persistence. Studies investigating the host factors involved in cell susceptibility to HIV-1 infection might lead to a better understanding of the reservoir formation and will eventually allow the development of an efficient cure. Our team previously showed the antiviral role of p53 in macrophages, which acts by compromising the early steps of HIV-1 replication. In this study, we demonstrate the involvement of p53 isoforms, which regulates p53 activity and define the cellular environment influencing viral replication. In addition, the results concerning the potential role of p53 in antiviral innate immunity could be transposed to other fields of virology and suggest that knowledge in oncology can be applied to HIV-1 research.

scholarly journals Network-Guided Discovery of Influenza Virus Replication Host Factors

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Emily E. Ackerman ◽  
Eiryo Kawakami ◽  
Manami Katoh ◽  
Tokiko Watanabe ◽  
Shinji Watanabe ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Viral Replication ◽  
Virus Replication ◽  
Drug Targets ◽  
Antiviral Drug ◽  
Viral Proteins ◽  
Host Factors ◽  
Ppi Network ◽  
Host Proteins ◽  
Influenza Virus Replication

ABSTRACTThe positions of host factors required for viral replication within a human protein-protein interaction (PPI) network can be exploited to identify drug targets that are robust to drug-mediated selective pressure. Host factors can physically interact with viral proteins, be a component of virus-regulated pathways (where proteins do not interact with viral proteins), or be required for viral replication but unregulated by viruses. Here, we demonstrate a method of combining human PPI networks with virus-host PPI data to improve antiviral drug discovery for influenza viruses by identifying target host proteins. Analysis shows that influenza virus proteins physically interact with host proteins in network positions significant for information flow, even after the removal of known abundance-degree bias within PPI data. We have isolated a subnetwork of the human PPI network that connects virus-interacting host proteins to host factors that are important for influenza virus replication without physically interacting with viral proteins. The subnetwork is enriched for signaling and immune processes distinct from those associated with virus-interacting proteins. Selecting proteins based on subnetwork topology, we performed an siRNA screen to determine whether the subnetwork was enriched for virus replication host factors and whether network position within the subnetwork offers an advantage in prioritization of drug targets to control influenza virus replication. We found that the subnetwork is highly enriched for target host proteins—more so than the set of host factors that physically interact with viral proteins. Our findings demonstrate that network positions are a powerful predictor to guide antiviral drug candidate prioritization.IMPORTANCEIntegrating virus-host interactions with host protein-protein interactions, we have created a method using these established network practices to identify host factors (i.e., proteins) that are likely candidates for antiviral drug targeting. We demonstrate that interaction cascades between host proteins that directly interact with viral proteins and host factors that are important to influenza virus replication are enriched for signaling and immune processes. Additionally, we show that host proteins that interact with viral proteins are in network locations of power. Finally, we demonstrate a new network methodology to predict novel host factors and validate predictions with an siRNA screen. Our results show that integrating virus-host proteins interactions is useful in the identification of antiviral drug target candidates.

scholarly journals Protein Kinase G Phosphorylates Mosquito-Borne Flavivirus NS5

2009 ◽  
Vol 83 (18) ◽  
pp. 9195-9205 ◽  
Author(s):  
Dipankar Bhattacharya ◽  
Mayuri ◽  
S. M. Best ◽  
R. Perera ◽  
R. J. Kuhn ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Yellow Fever Virus ◽  
Nonstructural Protein ◽  
Protein Kinase G ◽  
Phosphorylation Sites ◽  
Histidine Residue ◽  
Phosphorylation Event ◽  
Langat Virus ◽  
And Function

ABSTRACT Serine/threonine phosphorylation of the nonstructural protein 5 (NS5) is a conserved feature of flaviviruses, but the kinase(s) responsible and function(s) remain unknown. Mass spectrometry was used to compare the phosphorylation sites of the NS5 proteins of yellow fever virus (YFV) and dengue virus (DENV), two flaviviruses transmitted by mosquitoes. Seven DENV phosphopeptides were identified, but only one conserved phosphoacceptor site (threonine 449 in DENV) was identified in both viruses. This site is predicted to be a protein kinase G (PKG) recognition site and is a strictly conserved serine/threonine phosphoacceptor site in mosquito-borne flaviviruses. In contrast, in tick-borne flaviviruses, this residue is typically a histidine. A DENV replicon engineered to have the tick-specific histidine residue at this position is replication defective. We show that DENV NS5 purified from Escherichia coli is a substrate for PKG in vitro and facilitates the autophosphorylation of PKG as seen with cellular substrates. Phosphorylation in vitro by PKG also occurs at threonine 449. Activators and inhibitors of PKG modulate DENV replication in cell culture but not replication of the tick-borne langat virus. Collectively, these data argue that PKG mediates a conserved serine/threonine phosphorylation event specifically for flaviviruses spread by mosquitoes.

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