scholarly journals Comprehensive Analysis of Ebola Virus GP1 in Viral Entry

2005 ◽  
Vol 79 (8) ◽  
pp. 4793-4805 ◽  
Author(s):  
Balaji Manicassamy ◽  
Jizhen Wang ◽  
Haiqing Jiang ◽  
Lijun Rong
Keyword(s):  
Viral Entry ◽  
Ebola Virus ◽  
Binding Pocket ◽  
Marburg Virus ◽  
Pseudotyped Virus ◽  
Viral Glycoprotein ◽  
Functional Roles ◽  
Critical Residues ◽  
And Function ◽  
Expression Processing

ABSTRACT Ebola virus infection is initiated by interactions between the viral glycoprotein GP1 and its cognate receptor(s), but little is known about the structure and function of GP1 in viral entry, partly due to the concern about safety when working with the live Ebola virus and the difficulty of manipulating the RNA genome of Ebola virus. In this study, we have used a human immunodeficiency virus-based pseudotyped virus as a surrogate system to dissect the role of Ebola virus GP1 in viral entry. Analysis of more than 100 deletion and amino acid substitution mutants of GP1 with respect to protein expression, processing, viral incorporation, and viral entry has allowed us to map the region of GP1 responsible for viral entry to the N-terminal 150 residues. Furthermore, six amino acids in this region have been identified as critical residues for early events in Ebola virus entry, and among these, three are clustered and are implicated as part of a potential receptor-binding pocket. In addition, substitutions of some 30 residues in GP1 are shown to adversely affect GP1 expression, processing, and viral incorporation, suggesting that these residues are involved in the proper folding and/or overall conformation of GP. Sequence comparison of the GP1 proteins suggests that the majority of the critical residues for GP folding and viral entry identified in Ebola virus GP1 are conserved in Marburg virus. These results provide information for elucidating the structural and functional roles of the filoviral glycoproteins and for developing potential therapeutics to block viral entry.

scholarly journals Ebola virus triggers receptor tyrosine kinase-dependent signaling to promote the delivery of viral particles to entry-conducive intracellular compartments

2021 ◽  
Vol 17 (1) ◽  
pp. e1009275
Author(s):  
Corina M. Stewart ◽  
Alexandra Phan ◽  
Yuxia Bo ◽  
Nicholas D. LeBlond ◽  
Tyler K. T. Smith ◽  
...  
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Viral Entry ◽  
Receptor Tyrosine Kinase ◽  
Ebola Virus ◽  
Marburg Virus ◽  
Host Protein ◽  
Signaling Cascades ◽  
Viral Glycoprotein ◽  
Viral Particles

Filoviruses, such as the Ebola virus (EBOV) and Marburg virus (MARV), are causative agents of sporadic outbreaks of hemorrhagic fevers in humans. To infect cells, filoviruses are internalized via macropinocytosis and traffic through the endosomal pathway where host cathepsin-dependent cleavage of the viral glycoproteins occurs. Subsequently, the cleaved viral glycoprotein interacts with the late endosome/lysosome resident host protein, Niemann-Pick C1 (NPC1). This interaction is hypothesized to trigger viral and host membrane fusion, which results in the delivery of the viral genome into the cytoplasm and subsequent initiation of replication. Some studies suggest that EBOV viral particles activate signaling cascades and host-trafficking factors to promote their localization with host factors that are essential for entry. However, the mechanism through which these activating signals are initiated remains unknown. By screening a kinase inhibitor library, we found that receptor tyrosine kinase inhibitors potently block EBOV and MARV GP-dependent viral entry. Inhibitors of epidermal growth factor receptor (EGFR), tyrosine protein kinase Met (c-Met), and the insulin receptor (InsR)/insulin like growth factor 1 receptor (IGF1R) blocked filoviral GP-mediated entry and prevented growth of replicative EBOV in Vero cells. Furthermore, inhibitors of c-Met and InsR/IGF1R also blocked viral entry in macrophages, the primary targets of EBOV infection. Interestingly, while the c-Met and InsR/IGF1R inhibitors interfered with EBOV trafficking to NPC1, virus delivery to the receptor was not impaired in the presence of the EGFR inhibitor. Instead, we observed that the NPC1 positive compartments were phenotypically altered and rendered incompetent to permit viral entry. Despite their different mechanisms of action, all three RTK inhibitors tested inhibited virus-induced Akt activation, providing a possible explanation for how EBOV may activate signaling pathways during entry. In sum, these studies strongly suggest that receptor tyrosine kinases initiate signaling cascades essential for efficient post-internalization entry steps.

scholarly journals Influence of different glycoproteins and of the virion core on SERINC5 antiviral activity

2019 ◽  
Author(s):  
William E. Diehl ◽  
Mehmet H. Guney ◽  
Pyae Phyo Kyawe ◽  
Judith M. White ◽  
Massimo Pizzato ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Antiviral Activity ◽  
Viral Entry ◽  
Ebola Virus ◽  
Endogenous Retrovirus ◽  
Marburg Virus ◽  
Human Endogenous Retrovirus ◽  
Target Cells ◽  
Viral Glycoprotein ◽  
Hiv 1

ABSTRACTHost plasma membrane protein SERINC5 is incorporated into budding retrovirus particles where it blocks subsequent entry into susceptible target cells. Three accessory proteins encoded by diverse retroviruses, HIV-1 Nef, EIAV S2, and MLV Glycogag, each independently disrupt SERINC5 antiviral activity, by redirecting SERINC5 from the site of virion assembly on the plasma membrane to an internal RAB7+ endosomal compartment. Pseudotyping retroviruses with particular glycoproteins, e.g., the vesicular stomatitis glycoprotein (VSV G), renders the infectivity of particles resistant to inhibition by virion-associated SERINC5. To better understand viral determinants for SERINC5-sensitivity, the effect of SERINC5 was assessed using HIV-1, MLV, and M-PMV virion cores, pseudotyped with glycoproteins from Arenavirus, Coronavirus, Filovirus, Rhabdovirus, Paramyxovirus, and Orthomyxovirus genera. Infectivity of particles, pseudotyped with HIV-1, amphotropic-MLV, or influenza virus glycoproteins, was decreased by SERINC5, whether the core was provided by HIV-1, MLV, or M-PMV. Particles generated by all three cores, and pseudotyped with glycoproteins from either avian leukosis virus-A, human endogenous retrovirus K (HERV-K), ecotropic-MLV, HTLV-1, Measles morbillivirus, lymphocytic choriomeningitis mammarenavirus (LCMV), Marburg virus, Ebola virus, severe acute respiratory syndrome-related coronavirus (SARS-CoV), or VSV, were insensitive to SERINC5. In contrast, particles pseudotyped with M-PMV, RD114, or rabies virus (RABV) glycoproteins were sensitive to SERINC5, but only with particular retroviral cores. Resistance to SERINC5 by particular glycoproteins did not correlate with reduced SERINC5 incorporation into particles or with the route of viral entry. These findings indicate that some non-retroviruses may be sensitive to SERINC5 and that, in addition to the viral glycoprotein, the retroviral core influences sensitivity to SERINC5.IMPORTANCEThe importance of SERINC5 for inhibition of retroviruses is underscored by convergent evolution among three non-monophyletic retroviruses, each of which encodes a structurally unrelated SERINC5 inhibitor. One of these retroviruses causes tumors in mice, a second anemia in horses, and a third causes AIDS. SERINC5 is incorporated into retrovirus particles where it blocks entry into target cells, via a mechanism that is dependent on the viral glycoprotein. Here we demonstrate that retroviruses pseudotyped with glycoproteins from several non-retroviruses are also inhibited by SERINC5, suggesting that enveloped viruses other than retroviruses may also be inhibited by SERINC5. Additionally, we found that sensitivity to SERINC5 is determined by the retrovirus core, as well as by the glycoprotein. By better understanding how SERINC5 inhibits viruses we hope to extend fundamental understanding of virus replication and of the native role of SERINC5 in cells, and perhaps to advance the development of new antiviral strategies.

scholarly journals Application of pseudotyped virus particles to monitor Ebola virus and SARS-CoV-2 viral entry in human cell lines

2021 ◽  
Vol 2 (4) ◽  
pp. 100818
Author(s):  
Madeleine Eichler ◽  
Ebru Aksi ◽  
Josef Pfeilschifter ◽  
Gergely Imre
Keyword(s):  
Cell Lines ◽  
Human Cell ◽  
Viral Entry ◽  
Ebola Virus ◽  
Pseudotyped Virus ◽  
Human Cell Lines ◽  
Virus Particles

scholarly journals Structure, activity and inhibition of human TMPRSS2, a protease implicated in SARS-CoV-2 activation

2021 ◽  
Author(s):  
Bryan J Fraser ◽  
Serap Beldar ◽  
Almagul Seitova ◽  
Ashley Hutchinson ◽  
Dhiraj Mannar ◽  
...  
Keyword(s):  
Viral Entry ◽  
Serine Proteases ◽  
Binding Pocket ◽  
Structural Basis ◽  
Viral Glycoprotein ◽  
S Protein ◽  
Recombinant Production ◽  
Host Membrane ◽  
Future Drug ◽  
Glycoprotein Processing

Transmembrane protease, serine 2 (TMPRSS2) has been identified as key host cell factor for viral entry and pathogenesis of SARS-coronavirus-2 (SARS-CoV-2). Specifically, TMPRSS2 proteolytically processes the SARS-CoV-2 Spike (S) Protein, enabling virus-host membrane fusion and infection of the lungs. We present here an efficient recombinant production strategy for enzymatically active TMPRSS2 ectodomain enabling enzymatic characterization, and the 1.95 A X-ray crystal structure. To stabilize the enzyme for co-crystallization, we pre-treated TMPRSS2 with the synthetic protease inhibitor nafamosat to form a stable but slowly reversible (15 hour half-life) phenylguanidino acyl-enzyme complex. Our study provides a structural basis for the potent but non-specific inhibition by nafamostat and identifies distinguishing features of the TMPRSS2 substrate binding pocket that will guide future generations of inhibitors to improve selectivity. TMPRSS2 cleaved recombinant SARS-CoV-2 S protein ectodomain at the canonical S1/S2 cleavage site and at least two additional minor sites previously uncharacterized. We established enzymatic activity and inhibition assays that enabled ranking of clinical protease inhibitors with half-maximal inhibitory concentrations ranging from 1.7 nM to 120 uM and determination of inhibitor mechanisms of action. These results provide a body of data and reagents to support future drug development efforts to selectively inhibit TMPRSS2 and other type 2 transmembrane serine proteases involved in viral glycoprotein processing, in order to combat current and future viral threats.

scholarly journals Ebola Virus Produces Discrete Small Noncoding RNAs Independently of the Host MicroRNA Pathway Which Lack RNA Interference Activity in Bat and Human Cells

2019 ◽  
Vol 94 (6) ◽  
Author(s):  
Abhishek N. Prasad ◽  
Adam J. Ronk ◽  
Steven G. Widen ◽  
Thomas G. Wood ◽  
Christopher F. Basler ◽  
...  
Keyword(s):  
Ebola Virus ◽  
Noncoding Rnas ◽  
Computational Prediction ◽  
Marburg Virus ◽  
Sequencing Data ◽  
Viral Mirnas ◽  
Small Noncoding Rnas ◽  
Bona Fide ◽  
Mirna Pathway ◽  
And Function

ABSTRACT The question as to whether RNA viruses produce bona fide microRNAs (miRNAs) during infection has been the focus of intense research and debate. Recently, several groups using computational prediction methods have independently reported possible miRNA candidates produced by Ebola virus (EBOV). Additionally, efforts to detect these predicted RNA products in samples from infected animals and humans have produced positive results. However, these studies and their conclusions are predicated on the assumption that these RNA products are actually processed through, and function within, the miRNA pathway. In the present study, we performed the first rigorous assessment of the ability of filoviruses to produce miRNA products during infection of both human and bat cells. Using next-generation sequencing, we detected several candidate miRNAs from both EBOV and the closely related Marburg virus (MARV). Focusing our validation efforts on EBOV, we found evidence contrary to the idea that these small RNA products function as miRNAs. The results of our study are important because they highlight the potential pitfalls of relying on computational methods alone for virus miRNA discovery. IMPORTANCE Here, we report the discovery, via deep sequencing, of numerous noncoding RNAs (ncRNAs) derived from both EBOV and MARV during infection of both bat and human cell lines. In addition to identifying several novel ncRNAs from both viruses, we identified two EBOV ncRNAs in our sequencing data that were near-matches to computationally predicted viral miRNAs reported in the literature. Using molecular and immunological techniques, we assessed the potential of EBOV ncRNAs to function as viral miRNAs. Importantly, we found little evidence supporting this hypothesis. Our work is significant because it represents the first rigorous assessment of the potential for EBOV to encode viral miRNAs and provides evidence contrary to the existing paradigm regarding the biological role of computationally predicted EBOV ncRNAs. Moreover, our work highlights further avenues of research regarding the nature and function of EBOV ncRNAs.

scholarly journals Inhibition of Ebola Virus Entry by a C-peptide Targeted to Endosomes

2011 ◽  
Vol 286 (18) ◽  
pp. 15854-15861 ◽  
Author(s):  
Emily Happy Miller ◽  
Joseph S. Harrison ◽  
Sheli R. Radoshitzky ◽  
Chelsea D. Higgins ◽  
Xiaoli Chi ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Viral Entry ◽  
Ebola Virus ◽  
Hemorrhagic Fever ◽  
Marburg Virus ◽  
Viral Envelope ◽  
Heptad Repeat ◽  
Fusion Event ◽  
C Peptide ◽  
Hiv 1

Ebola virus (EboV) and Marburg virus (MarV) (filoviruses) are the causative agents of severe hemorrhagic fever. Infection begins with uptake of particles into cellular endosomes, where the viral envelope glycoprotein (GP) catalyzes fusion between the viral and host cell membranes. This fusion event is thought to involve conformational rearrangements of the transmembrane subunit (GP2) of the envelope spike that ultimately result in formation of a six-helix bundle by the N- and C-terminal heptad repeat (NHR and CHR, respectively) regions of GP2. Infection by other viruses employing similar viral entry mechanisms (such as HIV-1 and severe acute respiratory syndrome coronavirus) can be inhibited with synthetic peptides corresponding to the native CHR sequence (“C-peptides”). However, previously reported EboV C-peptides have shown weak or insignificant antiviral activity. To determine whether the activity of a C-peptide could be improved by increasing its intracellular concentration, we prepared an EboV C-peptide conjugated to the arginine-rich sequence from HIV-1 Tat, which is known to accumulate in endosomes. We found that this peptide specifically inhibited viral entry mediated by filovirus GP proteins and infection by authentic filoviruses. We determined that antiviral activity was dependent on both the Tat sequence and the native EboV CHR sequence. Mechanistic studies suggested that the peptide acts by blocking a membrane fusion intermediate.

scholarly journals A Diacylglycerol Kinase Inhibitor, R-59-022, Blocks Filovirus Internalization in Host Cells

Viruses ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 206 ◽  
Author(s):  
Corina Stewart ◽  
Stephanie Dorion ◽  
Marie Ottenbrite ◽  
Nicholas LeBlond ◽  
Tyler Smith ◽  
...  
Keyword(s):  
Viral Entry ◽  
Ebola Virus ◽  
Kinase Inhibitor ◽  
Diacylglycerol Kinase ◽  
Marburg Virus ◽  
Host Cells ◽  
Dependent Manner ◽  
Viral Receptor ◽  
Viral Particles ◽  
Starting Point

Filoviruses, such as Ebola virus (EBOV) and Marburg virus, are causative agents of unpredictable outbreaks of severe hemorrhagic fevers in humans and non-human primates. For infection, filoviral particles need to be internalized and delivered to intracellular vesicles containing cathepsin proteases and the viral receptor Niemann-Pick C1. Previous studies have shown that EBOV triggers macropinocytosis of the viral particles in a glycoprotein (GP)-dependent manner, but the molecular events required for filovirus internalization remain mostly unknown. Here we report that the diacylglycerol kinase inhibitor, R-59-022, blocks EBOV GP-mediated entry into Vero cells and bone marrow-derived macrophages. Investigation of the mode of action of the inhibitor revealed that it blocked an early step in entry, more specifically, the internalization of the viral particles via macropinocytosis. Finally, R-59-022 blocked viral entry mediated by a panel of pathogenic filovirus GPs and inhibited growth of replicative Ebola virus. Taken together, our studies suggest that R-59-022 could be used as a tool to investigate macropinocytic uptake of filoviruses and could be a starting point for the development of pan-filoviral therapeutics.

scholarly journals Characterization of Ebola Virus Entry by Using Pseudotyped Viruses: Identification of Receptor-Deficient Cell Lines

1998 ◽  
Vol 72 (4) ◽  
pp. 3155-3160 ◽  
Author(s):  
Rouven J. Wool-Lewis ◽  
Paul Bates
Keyword(s):  
Host Range ◽  
Cell Lines ◽  
Neutralizing Antibodies ◽  
Ebola Virus ◽  
High Titer ◽  
Leukemia Virus ◽  
Pseudotyped Virus ◽  
Cellular Receptor ◽  
And Function

ABSTRACT Studies analyzing Ebola virus replication have been severely hampered by the extreme pathogenicity of this virus. To permit analysis of the host range and function of the Ebola virus glycoprotein (Ebo-GP), we have developed a system for pseudotyping these glycoproteins into murine leukemia virus (MLV). This pseudotyped virus, MLV(Ebola), can be readily concentrated to titers which exceed 5 × 106 infectious units/ml and is effectively neutralized by antibodies specific for Ebo-GP. Analysis of MLV(Ebola) infection revealed that the host range conferred by Ebo-GP is very broad, extending to cells of a variety of species. Notably, all lymphoid cell lines tested were completely resistant to infection; we speculate that this is due to the absence of a cellular receptor for Ebo-GP on B and T cells. The generation of high-titer MLV(Ebola) pseudotypes will be useful for the analysis of immune responses to Ebola virus infection, development of neutralizing antibodies, analysis of glycoprotein function, and isolation of the cellular receptor(s) for the Ebola virus.

Computational Approaches to Predict the Non-canonical DNAs

2019 ◽  
Vol 14 (6) ◽  
pp. 470-479 ◽  
Author(s):  
Nazia Parveen ◽  
Amen Shamim ◽  
Seunghee Cho ◽  
Kyeong Kyu Kim
Keyword(s):  
Computational Methods ◽  
Genetic Instability ◽  
Computational Prediction ◽  
Structure And Function ◽  
Sequence Motifs ◽  
Computational Approaches ◽  
Functional Roles ◽  
And Function ◽  
Genetic Events ◽  
Insight Into

Background: Although most nucleotides in the genome form canonical double-stranded B-DNA, many repeated sequences transiently present as non-canonical conformations (non-B DNA) such as triplexes, quadruplexes, Z-DNA, cruciforms, and slipped/hairpins. Those noncanonical DNAs (ncDNAs) are not only associated with many genetic events such as replication, transcription, and recombination, but are also related to the genetic instability that results in the predisposition to disease. Due to the crucial roles of ncDNAs in cellular and genetic functions, various computational methods have been implemented to predict sequence motifs that generate ncDNA. Objective: Here, we review strategies for the identification of ncDNA motifs across the whole genome, which is necessary for further understanding and investigation of the structure and function of ncDNAs. Conclusion: There is a great demand for computational prediction of non-canonical DNAs that play key functional roles in gene expression and genome biology. In this study, we review the currently available computational methods for predicting the non-canonical DNAs in the genome. Current studies not only provide an insight into the computational methods for predicting the secondary structures of DNA but also increase our understanding of the roles of non-canonical DNA in the genome.

scholarly journals Antibody-Dependent Enhancement of Ebola Virus Infection

2003 ◽  
Vol 77 (13) ◽  
pp. 7539-7544 ◽  
Author(s):  
Ayato Takada ◽  
Heinz Feldmann ◽  
Thomas G. Ksiazek ◽  
Yoshihiro Kawaoka
Keyword(s):  
Virus Infection ◽  
Ebola Virus ◽  
Human Populations ◽  
Hemorrhagic Disease ◽  
Viral Infectivity ◽  
Kidney Cells ◽  
Emerging Pathogens ◽  
Viral Glycoprotein ◽  
Antibody Dependent Enhancement ◽  
Ebola Virus Infection

ABSTRACT Most strains of Ebola virus cause a rapidly fatal hemorrhagic disease in humans, yet there are still no biologic explanations that adequately account for the extreme virulence of these emerging pathogens. Here we show that Ebola Zaire virus infection in humans induces antibodies that enhance viral infectivity. Plasma or serum from convalescing patients enhanced the infection of primate kidney cells by the Zaire virus, and this enhancement was mediated by antibodies to the viral glycoprotein and by complement component C1q. Our results suggest a novel mechanism of antibody-dependent enhancement of Ebola virus infection, one that would account for the dire outcome of Ebola outbreaks in human populations.

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