Shirit Einav

All Publications

• Interactions between the Hepatitis C Virus Nonstructural 2 Protein and Host Adaptor Proteins 1 and 4 Orchestrate Virus Release. mBio Xiao, F., Wang, S., Barouch-Bentov, R., Neveu, G., Pu, S., Beer, M., Schor, S., Kumar, S., Nicolaescu, V., Lindenbach, B. D., Randall, G., Einav, S. 2018; 9 (2)

  Abstract

  Hepatitis C virus (HCV) spreads via secreted cell-free particles or direct cell-to-cell transmission. Yet, virus-host determinants governing differential intracellular trafficking of cell-free- and cell-to-cell-transmitted virus remain unknown. The host adaptor proteins (APs) AP-1A, AP-1B, and AP-4 traffic in post-Golgi compartments, and the latter two are implicated in basolateral sorting. We reported that AP-1A mediates HCV trafficking during release, whereas the endocytic adaptor AP-2 mediates entry and assembly. We demonstrated that the host kinases AAK1 and GAK regulate HCV infection by controlling these clathrin-associated APs. Here, we sought to define the roles of AP-4, a clathrin-independent adaptor; AP-1A; and AP-1B in HCV infection. We screened for interactions between HCV proteins and the μ subunits of AP-1A, AP-1B, and AP-4 by mammalian cell-based protein fragment complementation assays. The nonstructural 2 (NS2) protein emerged as an interactor of these adaptors in this screening and by coimmunoprecipitations in HCV-infected cells. Two previously unrecognized dileucine-based motifs in the NS2 C terminus mediated AP binding and HCV release. Infectivity and coculture assays demonstrated that while all three adaptors mediate HCV release and cell-free spread, AP-1B and AP-4, but not AP-1A, mediate cell-to-cell spread. Live-cell imaging revealed HCV cotrafficking with AP-1A, AP-1B, and AP-4 and that AP-4 mediates HCV trafficking in a post-Golgi compartment. Lastly, HCV cell-to-cell spread was regulated by AAK1 and GAK and thus susceptible to treatment with AAK1 and GAK inhibitors. These data provide a mechanistic understanding of HCV trafficking in distinct release pathways and reveal a requirement for APs in cell-to-cell viral spread.IMPORTANCE HCV spreads via cell-free infection or cell-to-cell contact that shields it from antibody neutralization, thereby facilitating viral persistence. Yet, factors governing this differential sorting remain unknown. By integrating proteomic, RNA interference, genetic, live-cell imaging, and pharmacological approaches, we uncover differential coopting of host adaptor proteins (APs) to mediate HCV traffic at distinct late steps of the viral life cycle. We reported that AP-1A and AP-2 mediate HCV trafficking during release and assembly, respectively. Here, we demonstrate that dileucine motifs in the NS2 protein mediate AP-1A, AP-1B, and AP-4 binding and cell-free virus release. Moreover, we reveal that AP-4, an adaptor not previously implicated in viral infections, mediates cell-to-cell spread and HCV trafficking. Lastly, we demonstrate cell-to-cell spread regulation by AAK1 and GAK, host kinases controlling APs, and susceptibility to their inhibitors. This study provides mechanistic insights into virus-host determinants that facilitate HCV trafficking, with potential implications for pathogenesis and antiviral agent design.

  View details for DOI 10.1128/mBio.02233-17

  View details for PubMedID 29535204

  View details for PubMedCentralID PMC5850324

• Turning Up Your Nose for a Flaviviral Encephalitis Cure. Cell host & microbe Barouch-Bentov, R., Einav, S. 2018; 23 (4): 427–29

  Abstract

  siRNA approaches have demonstrated promise in treating viral infections in animal models, but poor delivery limits clinical application. In this issue of Cell Host & Microbe, Beloor et al. (2018) report that nose-to-brain delivery of viral-targeted siRNA cures mice from West Nile virus encephalitis, with potential implications for human infection.

  View details for DOI 10.1016/j.chom.2018.03.014

  View details for PubMedID 29649437

• Single-cell transcriptional dynamics of flavivirus infection. eLife Zanini, F., Pu, S. Y., Bekerman, E., Einav, S., Quake, S. R. 2018; 7

  Abstract

  Dengue and Zika viral infections affect millions of people annually and can be complicated by hemorrhage and shock or neurological manifestations, respectively. However, a thorough understanding of the host response to these viruses is lacking, partly because conventional approaches ignore heterogeneity in virus abundance across cells. We present viscRNA-Seq (virus-inclusive single cell RNA-Seq), an approach to probe the host transcriptome together with intracellular viral RNA at the single cell level. We applied viscRNA-Seq to monitor dengue and Zika virus infection in cultured cells and discovered extreme heterogeneity in virus abundance. We exploited this variation to identify host factors that show complex dynamics and a high degree of specificity for either virus, including proteins involved in the endoplasmic reticulum translocon, signal peptide processing, and membrane trafficking. We validated the viscRNA-Seq hits and discovered novel proviral and antiviral factors. viscRNA-Seq is a powerful approach to assess the genome-wide virus-host dynamics at single cell level.

  View details for DOI 10.7554/eLife.32942

  View details for PubMedID 29451494

• Combating Intracellular Pathogens with Repurposed Host-Targeted Drugs. ACS infectious diseases Schor, S., Einav, S. 2018; 4 (2): 88–92

  Abstract

  There is a large, global unmet need for the development of countermeasures to combat intracellular pathogens. The development of novel antimicrobials is expensive and slow and typically focuses on selective inhibition of proteins encoded by a single pathogen, thereby providing a narrow spectrum of coverage. The repurposing of approved drugs targeting host functions required for microbial infections represents a promising alternative. This review summarizes progress and challenges in the repurposing of approved drugs as host-targeted broad-spectrum agents for the treatment of intracellular pathogens. These strategies include targeting both cellular factors required for infection by various viruses, intracellular bacteria, and/or protozoa as well as factors that modulate the host immune response to these microbial infections. The repurposed approach offers complementary means to develop therapeutics against existing and emerging intracellular microbial threats.

  View details for DOI 10.1021/acsinfecdis.7b00268

  View details for PubMedID 29298032

  View details for PubMedCentralID PMC5807128

• Anticancer kinase inhibitors impair intracellular viral trafficking and exert broad-spectrum antiviral effects JOURNAL OF CLINICAL INVESTIGATION Bekerman, E., Neveu, G., Shulla, A., Brannan, J., Pu, S., Wang, S., Xiao, F., Barouch-Bentov, R., Bakken, R. R., Mateo, R., Govero, J., Nagamine, C. M., Diamond, M. S., De Jonghe, S., Herdewijn, P., Dye, J. M., Randall, G., Einav, S. 2017; 127 (4): 1338-1352

  Abstract

  Global health is threatened by emerging viral infections, which largely lack effective vaccines or therapies. Targeting host pathways that are exploited by multiple viruses could offer broad-spectrum solutions. We previously reported that AAK1 and GAK, kinase regulators of the host adaptor proteins AP1 and AP2, are essential for hepatitis C virus (HCV) infection, but the underlying mechanism and relevance to other viruses or in vivo infections remained unknown. Here, we have discovered that AP1 and AP2 cotraffic with HCV particles in live cells. Moreover, we found that multiple viruses, including dengue and Ebola, exploit AAK1 and GAK during entry and infectious virus production. In cultured cells, treatment with sunitinib and erlotinib, approved anticancer drugs that inhibit AAK1 or GAK activity, or with more selective compounds inhibited intracellular trafficking of HCV and multiple unrelated RNA viruses with a high barrier to resistance. In murine models of dengue and Ebola infection, sunitinib/erlotinib combination protected against morbidity and mortality. We validated sunitinib- and erlotinib-mediated inhibition of AAK1 and GAK activity as an important mechanism of antiviral action. Additionally, we revealed potential roles for additional kinase targets. These findings advance our understanding of virus-host interactions and establish a proof of principle for a repurposed, host-targeted approach to combat emerging viruses.

  View details for DOI 10.1172/JCI89857

  View details for Web of Science ID 000398183300024

  View details for PubMedID 28240606

• Repurposing of Kinase Inhibitors as Broad-Spectrum Antiviral Drugs. DNA Cell Biol. Schor, S., Einav, S. 2017

  View details for DOI 10.1089/dna.2017.4033

• Hepatitis C Virus Proteins Interact with the Endosomal Sorting Complex Required for Transport (ESCRT) Machinery via Ubiquitination To Facilitate Viral Envelopment. mBio Barouch-Bentov, R., Neveu, G., Xiao, F., Beer, M., Bekerman, E., Schor, S., Campbell, J., Boonyaratanakornkit, J., Lindenbach, B., Lu, A., Jacob, Y., Einav, S. 2016; 7 (6)

  Abstract

  Enveloped viruses commonly utilize late-domain motifs, sometimes cooperatively with ubiquitin, to hijack the endosomal sorting complex required for transport (ESCRT) machinery for budding at the plasma membrane. However, the mechanisms underlying budding of viruses lacking defined late-domain motifs and budding into intracellular compartments are poorly characterized. Here, we map a network of hepatitis C virus (HCV) protein interactions with the ESCRT machinery using a mammalian-cell-based protein interaction screen and reveal nine novel interactions. We identify HRS (hepatocyte growth factor-regulated tyrosine kinase substrate), an ESCRT-0 complex component, as an important entry point for HCV into the ESCRT pathway and validate its interactions with the HCV nonstructural (NS) proteins NS2 and NS5A in HCV-infected cells. Infectivity assays indicate that HRS is an important factor for efficient HCV assembly. Specifically, by integrating capsid oligomerization assays, biophysical analysis of intracellular viral particles by continuous gradient centrifugations, proteolytic digestion protection, and RNase digestion protection assays, we show that HCV co-opts HRS to mediate a late assembly step, namely, envelopment. In the absence of defined late-domain motifs, K63-linked polyubiquitinated lysine residues in the HCV NS2 protein bind the HRS ubiquitin-interacting motif to facilitate assembly. Finally, ESCRT-III and VPS/VTA1 components are also recruited by HCV proteins to mediate assembly. These data uncover involvement of ESCRT proteins in intracellular budding of a virus lacking defined late-domain motifs and a novel mechanism by which HCV gains entry into the ESCRT network, with potential implications for other viruses.Viruses commonly bud at the plasma membrane by recruiting the host ESCRT machinery via conserved motifs termed late domains. The mechanism by which some viruses, such as HCV, bud intracellularly is, however, poorly characterized. Moreover, whether envelopment of HCV and other viruses lacking defined late domains is ESCRT mediated and, if so, what the entry points into the ESCRT pathway are remain unknown. Here, we report the interaction network of HCV with the ESCRT machinery and a critical role for HRS, an ESCRT-0 complex component, in HCV envelopment. Viral protein ubiquitination was discovered to be a signal for HRS binding and HCV assembly, thereby functionally compensating for the absence of late domains. These findings characterize how a virus lacking defined late domains co-opts ESCRT to bud intracellularly. Since the ESCRT machinery is essential for the life cycle of multiple viruses, better understanding of this virus-host interplay may yield targets for broad-spectrum antiviral therapies.

  View details for DOI 10.1128/mBio.01456-16

  View details for PubMedID 27803188

  View details for PubMedCentralID PMC5090039

• Pathogen receptor discovery with a microfluidic human membrane protein array PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Glick, Y., Ben-Ari, Y., Drayman, N., Pellach, M., Neveu, G., Boonyaratanakornkit, J., Avrahami, D., Einav, S., Oppenheim, A., Gerber, D. 2016; 113 (16): 4344-4349

  Abstract

  The discovery of how a pathogen invades a cell requires one to determine which host cell receptors are exploited. This determination is a challenging problem because the receptor is invariably a membrane protein, which represents an Achilles heel in proteomics. We have developed a universal platform for high-throughput expression and interaction studies of membrane proteins by creating a microfluidic-based comprehensive human membrane protein array (MPA). The MPA is, to our knowledge, the first of its kind and offers a powerful alternative to conventional proteomics by enabling the simultaneous study of 2,100 membrane proteins. We characterized direct interactions of a whole nonenveloped virus (simian virus 40), as well as those of the hepatitis delta enveloped virus large form antigen, with candidate host receptors expressed on the MPA. Selected newly discovered membrane protein-pathogen interactions were validated by conventional methods, demonstrating that the MPA is an important tool for cellular receptor discovery and for understanding pathogen tropism.

  View details for DOI 10.1073/pnas.1518698113

  View details for Web of Science ID 000374393800043

  View details for PubMedID 27044079

  View details for PubMedCentralID PMC4843447

• Epidermal Growth Factor Receptor-Dependent Mutual Amplification between Netrin-1 and the Hepatitis C Virus PLOS BIOLOGY Plissonnier, M., Lahlali, T., Michelet, M., Lebosse, F., Cottarel, J., Beer, M., Neveu, G., Durantel, D., Bartosch, B., Accardi, R., Clement, S., Paradisi, A., Devouassoux-Shisheboran, M., Einav, S., Mehlen, P., Zoulim, F., Parent, R. 2016; 14 (3)

  View details for DOI 10.1371/journal.pbio.1002421

  View details for Web of Science ID 000373038200035

• Response—Applying antibiotics lessons to antivirals. Science Bekerman, E., Einav, S. 2015; 348 (6242): 1437-?

  View details for DOI 10.1126/science.348.6242.1437-b

  View details for PubMedID 26113710

• Selective Inhibitors of Cyclin G Associated Kinase (GAK) as Anti-Hepatitis C Agents JOURNAL OF MEDICINAL CHEMISTRY Kovackova, S., Chang, L., Bekerman, E., Neveu, G., Barouch-Bentov, R., Chaikuad, A., Heroven, C., Sala, M., De Jonghe, S., Knapp, S., Einav, S., Herdewijn, P. 2015; 58 (8): 3393-3410

  Abstract

  Cyclin-G associated kinase (GAK) emerged as a promising drug target for the treatment of viral infections. However, no potent and selective GAK inhibitors have been reported in the literature to date. This paper describes the discovery of isothiazolo[5,4-b]pyridines as selective GAK inhibitors, with the most potent congeners displaying low nanomolar binding affinity for GAK. Co-crystallization experiments revealed that these compounds behaved as classic type I ATP-competitive kinase inhibitors. In addition, we have demonstrated that these compounds exhibit a potent activity against hepatitis C virus (HCV) by inhibiting two temporally distinct steps in the HCV lifecycle (i.e. viral entry and assembly). Hence, these GAK inhibitors represent chemical probes to study GAK function in different disease areas where GAK has been implicated (including viral infection, cancer and Parkinson's disease).

  View details for DOI 10.1021/jm501759m

  View details for Web of Science ID 000353602200009

  View details for PubMedID 25822739

• Infectious disease. Combating emerging viral threats. Science Bekerman, E., Einav, S. 2015; 348 (6232): 282-283

  View details for DOI 10.1126/science.aaa3778

  View details for PubMedID 25883340

• AP-2-Associated Protein Kinase 1 and Cyclin G-Associated Kinase Regulate Hepatitis C Virus Entry and Are Potential Drug Targets JOURNAL OF VIROLOGY Neveu, G., Ziv-Av, A., Barouch-Bentov, R., Berkerman, E., Mulholland, J., Einav, S. 2015; 89 (8): 4387-4404

  Abstract

  Hepatitis C virus (HCV) enters its target cell via clathrin-mediated endocytosis. AP-2-associated protein kinase 1 (AAK1) and cyclin G-associated kinase (GAK) are host kinases that regulate clathrin adaptor protein (AP)-mediated trafficking in the endocytic and secretory pathways. We previously reported that AAK1 and GAK regulate HCV assembly by stimulating binding of the μ subunit of AP-2, AP2M1, to HCV core protein. We also discovered that AAK1 and GAK inhibitors, including the approved anticancer drugs sunitinib and erlotinib, could block HCV assembly. Here, we hypothesized that AAK1 and GAK regulate HCV entry independently of their effect on HCV assembly. Indeed, silencing AAK1 and GAK expression inhibited entry of pseudoparticles and cell culture grown-HCV and internalization of Dil-labeled HCV particles with no effect on HCV attachment or RNA replication. AAK1 or GAK depletion impaired epidermal growth factor (EGF)-mediated enhanced HCV entry and endocytosis of EGF receptor (EGFR), an HCV entry cofactor and erlotinib's cancer target. Moreover, either RNA interference-mediated depletion of AP2M1 or NUMB, each a substrate of AAK1 and/or GAK, or overexpression of either an AP2M1 or NUMB phosphorylation site mutant inhibited HCV entry. Last, in addition to affecting assembly, sunitinib and erlotinib inhibited HCV entry at a postbinding step, their combination was synergistic, and their antiviral effect was reversed by either AAK1 or GAK overexpression. Together, these results validate AAK1 and GAK as critical regulators of HCV entry that function in part by activating EGFR, AP2M1, and NUMB and as the molecular targets underlying the antiviral effect of sunitinib and erlotinib (in addition to EGFR), respectively.Understanding the host pathways hijacked by HCV is critical for developing host-centered anti-HCV approaches. Entry represents a potential target for antiviral strategies; however, no FDA-approved HCV entry inhibitors are currently available. We reported that two host kinases, AAK1 and GAK, regulate HCV assembly. Here, we provide evidence that AAK1 and GAK regulate HCV entry independently of their role in HCV assembly and define the mechanisms underlying AAK1- and GAK-mediated HCV entry. By regulating temporally distinct steps in the HCV life cycle, AAK1 and GAK represent "master regulators" of HCV infection and potential targets for antiviral strategies. Indeed, approved anticancer drugs that potently inhibit AAK1 or GAK inhibit HCV entry in addition to assembly. These results contribute to an understanding of the mechanisms of HCV entry and reveal attractive host targets for antiviral strategies as well as approved candidate inhibitors of these targets, with potential implications for other viruses that hijack clathrin-mediated pathways.

  View details for DOI 10.1128/JVI.02705-14

  View details for Web of Science ID 000352218400030

  View details for PubMedID 25653444

• Isothiazolo[4,3-b]pyridines as inhibitors of cyclin G associated kinase: synthesis, structure-activity relationship studies and antiviral activity MEDCHEMCOMM Li, J., Kovackova, S., Pu, S., Rozenski, J., De Jonghe, S., Einav, S., Herdewijn, P. 2015; 6 (9): 1666-1672

  View details for DOI 10.1039/c5md00229j

  View details for Web of Science ID 000360639300011

• B-cell receptors expressed by lymphomas of hepatitis C virus (HCV)-infected patients rarely react with the viral proteins. Blood Ng, P. P., Kuo, C., Wang, S., Einav, S., Arcaini, L., Paulli, M., Portlock, C. S., Marcotrigiano, J., Tarr, A., Ball, J., Levy, R., Levy, S. 2014; 123 (10): 1512-1515

  Abstract

  Chronic HCV infection has been implicated in the induction and maintenance of B-cell lymphomas. The strongest evidence for this comes from clinical observations of tumor regressions upon anti-viral treatments. Here we used multiple methods to test the hypothesis that the expansion of HCV-specific B cells gives rise to lymphomas. We obtained lymphoma tissues from HCV-infected lymphoma patients, including some that later regressed upon anti-viral treatments. We expressed the lymphoma B-cell receptors (BCRs) as soluble IgGs and membrane IgMs, and analyzed their reactivity with HCV proteins and with HCV virions. We confirmed previous reports that HCV-associated lymphomas use a restricted immunoglobulin variable region (V) gene repertoire. However, we found no evidence for their binding to the HCV antigens. We conclude that most lymphomas of HCV-infected patients do not arise from B cells aimed at eliminating the virus.

  View details for DOI 10.1182/blood-2013-10-532895

  View details for PubMedID 24449209

• Identification and Targeting of an Interaction between a Tyrosine Motif within Hepatitis C Virus Core Protein and AP2M1 Essential for Viral Assembly PLOS PATHOGENS Neveu, G., Barouch-Bentov, R., Ziv-Av, A., Gerber, D., Jacob, Y., Einav, S. 2012; 8 (8)

  Abstract

  Novel therapies are urgently needed against hepatitis C virus infection (HCV), a major global health problem. The current model of infectious virus production suggests that HCV virions are assembled on or near the surface of lipid droplets, acquire their envelope at the ER, and egress through the secretory pathway. The mechanisms of HCV assembly and particularly the role of viral-host protein-protein interactions in mediating this process are, however, poorly understood. We identified a conserved heretofore unrecognized YXXΦ motif (Φ is a bulky hydrophobic residue) within the core protein. This motif is homologous to sorting signals within host cargo proteins known to mediate binding of AP2M1, the μ subunit of clathrin adaptor protein complex 2 (AP-2), and intracellular trafficking. Using microfluidics affinity analysis, protein-fragment complementation assays, and co-immunoprecipitations in infected cells, we show that this motif mediates core binding to AP2M1. YXXΦ mutations, silencing AP2M1 expression or overexpressing a dominant negative AP2M1 mutant had no effect on HCV RNA replication, however, they dramatically inhibited intra- and extracellular infectivity, consistent with a defect in viral assembly. Quantitative confocal immunofluorescence analysis revealed that core's YXXΦ motif mediates recruitment of AP2M1 to lipid droplets and that the observed defect in HCV assembly following disruption of core-AP2M1 binding correlates with accumulation of core on lipid droplets, reduced core colocalization with E2 and reduced core localization to trans-Golgi network (TGN), the presumed site of viral particles maturation. Furthermore, AAK1 and GAK, serine/threonine kinases known to stimulate binding of AP2M1 to host cargo proteins, regulate core-AP2M1 binding and are essential for HCV assembly. Last, approved anti-cancer drugs that inhibit AAK1 or GAK not only disrupt core-AP2M1 binding, but also significantly inhibit HCV assembly and infectious virus production. These results validate viral-host interactions essential for HCV assembly and yield compounds for pharmaceutical development.

  View details for DOI 10.1371/journal.ppat.1002845

  View details for Web of Science ID 000308558000023

  View details for PubMedID 22916011

  View details for PubMedCentralID PMC3420927

• The hepatitis C virus (HCV) NS4B RNA binding inhibitor clemizole is highly synergistic with HCV protease inhibitors. journal of infectious diseases Einav, S., Sobol, H. D., Gehrig, E., Glenn, J. S. 2010; 202 (1): 65-74

  Abstract

  We recently identified a compound, clemizole hydrochloride, that inhibits NS4B's RNA binding and hepatitis C virus (HCV) replication. Although significant, clemizole's antiviral effect is moderate (50% effective concentration of 8 microM against an HCV genotype 2a clone). We hypothesized that the combination of clemizole with other anti-HCV agents can increase the antiviral effect over that achieved with each drug alone and could also decrease the emergence of viral resistance.Luciferase reporter-linked HCV replication assays were used to study the antiviral effects of drug combinations that included clemizole. Data were analyzed using Loewe additivity and Bliss independence models for synergy, and resistance studies were performed using HCV colony formation assays.Clemizole's antiviral effect was highly synergistic with the HCV protease inhibitors SCH503034 and VX950, without toxicity. In contrast, combinations of clemizole with either interferon, ribavirin, or the nucleoside (NM283) and nonnucleoside (HCV796) HCV polymerase inhibitors were additive. Furthermore, combination of clemizole with SCH503034 decreased the frequency of drug-resistant mutants, compared with treatment with either drug alone. Finally, no cross-resistance to clemizole of SCH503034-resistant mutants (or vice versa) was observed.Clemizole can yield high-level synergy with the protease inhibitor class. Inclusion of clemizole in future anti-HCV cocktails can represent an attractive paradigm for increasing current virologic response rates.

  View details for DOI 10.1086/653080

  View details for PubMedID 20486856

• The Hepatitis C Virus (HCV) NS4B RNA Binding Inhibitor Clemizole Is Highly Synergistic with HCV Protease Inhibitors Annual Meeting of the Infectious-Diseases-Society-of-America Einav, S., Dvory-Sobol, H., Gehrig, E., Glenn, J. S. OXFORD UNIV PRESS INC. 2010: 65–74

  View details for DOI 10.1086/653080

  View details for Web of Science ID 000278322300008

• A small molecule inhibits HCV replication and alters NS4B's subcellular distribution ANTIVIRAL RESEARCH Bryson, P. D., Cho, N., Einav, S., Lee, C., Tai, V., Bechtel, J., Sivaraja, M., Roberts, C., Schmitz, U., Glenn, J. S. 2010; 87 (1): 1-8

  Abstract

  Hepatitis C Virus (HCV) is a leading cause of liver disease and represents a significant public health challenge. Treatments for this disease are inadequate and improved antiviral therapies are necessary. Several such antivirals are in development, most of which target the well-characterized NS3 protease or the NS5B polymerase. In contrast, the nonstructural 4B (NS4B) protein, though essential for HCV RNA replication, has been the subject of few pharmacological studies. One of the functions ascribed to this protein is the ability to form intracellular membrane-associated foci (MAF), which are believed to be related to the sites of viral replication. Here, we report the identification of a small molecule that inhibits HCV replication and disrupts the organization of these MAF. Genetic analysis links the compound's mode of action to the NS4B gene product, and transient transfections of NS4B-GFP demonstrate that treatment with this compound can lead to the formation of novel elongated assemblies of NS4B. Furthermore, an in vitro dynamic light scattering assay provides evidence that the second amphipathic helix of NS4B may be the target of the drug. Our results demonstrate that this molecule represents a new potential class of HCV inhibitors and also provides us with a useful tool for studying the HCV life cycle.

  View details for DOI 10.1016/j.antiviral.2010.03.013

  View details for Web of Science ID 000279452800001

  View details for PubMedID 20363257

  View details for PubMedCentralID PMC3909674

• Six RNA Viruses and Forty-One Hosts: Viral Small RNAs and Modulation of Small RNA Repertoires in Vertebrate and Invertebrate Systems PLOS PATHOGENS Parameswaran, P., Sklan, E., Wilkins, C., Burgon, T., Samuel, M. A., Lu, R., Ansel, K. M., Heissmeyer, V., Einav, S., Jackson, W., Doukas, T., Paranjape, S., Polacek, C., dos Santos, F. B., Jalili, R., Babrzadeh, F., Gharizadeh, B., Grimm, D., Kay, M., Koike, S., Sarnow, P., Ronaghi, M., Ding, S., Harris, E., Chow, M., Diamond, M. S., Kirkegaard, K., Glenn, J. S., Fire, A. Z. 2010; 6 (2)

  Abstract

  We have used multiplexed high-throughput sequencing to characterize changes in small RNA populations that occur during viral infection in animal cells. Small RNA-based mechanisms such as RNA interference (RNAi) have been shown in plant and invertebrate systems to play a key role in host responses to viral infection. Although homologs of the key RNAi effector pathways are present in mammalian cells, and can launch an RNAi-mediated degradation of experimentally targeted mRNAs, any role for such responses in mammalian host-virus interactions remains to be characterized. Six different viruses were examined in 41 experimentally susceptible and resistant host systems. We identified virus-derived small RNAs (vsRNAs) from all six viruses, with total abundance varying from "vanishingly rare" (less than 0.1% of cellular small RNA) to highly abundant (comparable to abundant micro-RNAs "miRNAs"). In addition to the appearance of vsRNAs during infection, we saw a number of specific changes in host miRNA profiles. For several infection models investigated in more detail, the RNAi and Interferon pathways modulated the abundance of vsRNAs. We also found evidence for populations of vsRNAs that exist as duplexed siRNAs with zero to three nucleotide 3' overhangs. Using populations of cells carrying a Hepatitis C replicon, we observed strand-selective loading of siRNAs onto Argonaute complexes. These experiments define vsRNAs as one possible component of the interplay between animal viruses and their hosts.

  View details for DOI 10.1371/journal.ppat.1000764

  View details for Web of Science ID 000275295900016

  View details for PubMedID 20169186

• Discovery of a hepatitis C target and its pharmacological inhibitors by microfluidic affinity analysis NATURE BIOTECHNOLOGY Einav, S., Gerber, D., Bryson, P. D., Sklan, E. H., Elazar, M., Maerkl, S. J., Glenn, J. S., Quake, S. R. 2008; 26 (9): 1019-1027

  Abstract

  More effective therapies are urgently needed against hepatitis C virus (HCV), a major cause of viral hepatitis. We used in vitro protein expression and microfluidic affinity analysis to study RNA binding by the HCV transmembrane protein NS4B, which plays an essential role in HCV RNA replication. We show that HCV NS4B binds RNA and that this binding is specific for the 3' terminus of the negative strand of the viral genome with a dissociation constant (Kd) of approximately 3.4 nM. A high-throughput microfluidic screen of a compound library identified 18 compounds that substantially inhibited binding of RNA by NS4B. One of these compounds, clemizole hydrochloride, was found to inhibit HCV RNA replication in cell culture that was mediated by its suppression of NS4B's RNA binding, with little toxicity for the host cell. These results yield new insight into the HCV life cycle and provide a candidate compound for pharmaceutical development.

  View details for DOI 10.1038/nbt.1490

  View details for Web of Science ID 000259074700025

  View details for PubMedID 18758449

• The nucleotide binding motif of hepatitis C virus NS4B can mediate cellular transformation and tumor formation without ha-ras co-transfection HEPATOLOGY Einav, S., Sklan, E. H., Moon, H. M., Gehrig, E., Liu, P., Hao, Y., Lowe, A. W., Glenn, J. S. 2008; 47 (3): 827-835

  Abstract

  Hepatitis C virus (HCV) is an important cause of chronic liver disease and is complicated by hepatocellular carcinoma (HCC). Mechanisms whereby the virus promotes cellular transformation are poorly understood. We hypothesized that the guanosine triphosphatase activity encoded in the HCV NS4B protein's nucleotide binding motif (NBM) might play a role in the transformation process. Here we report that NS4B can transform NIH-3T3 cells, leading to tumor formation in vivo. This transformation was independent of co-transfection with activated Ha-ras. Detailed analyses of NS4B mutants revealed that this transforming activity could be progressively inhibited and completely abrogated by increasing genetic impairment of the NS4B nucleotide binding motif.NS4B has in vitro and in vivo tumorigenic potential, and the NS4B transforming activity is indeed mediated by its NBM. Moreover, our results suggest that pharmacological inhibition of the latter might inhibit not only HCV replication but also the associated HCC.

  View details for DOI 10.1002/hep.22108

  View details for Web of Science ID 000253698900009

  View details for PubMedID 18081150

• TBC1D20 is a Rab1 GTPase-activating protein that mediates hepatitis C virus replication JOURNAL OF BIOLOGICAL CHEMISTRY Sklan, E. H., Serrano, R. L., Einav, S., Pfeffer, S. R., Lambright, D. G., Glenn, J. S. 2007; 282 (50): 36354-36361

  Abstract

  Like other viruses, productive hepatitis C virus (HCV) infection depends on certain critical host factors. We have recently shown that an interaction between HCV nonstructural protein NS5A and a host protein, TBC1D20, is necessary for efficient HCV replication. TBC1D20 contains a TBC (Tre-2, Bub2, and Cdc16) domain present in most known Rab GTPase-activating proteins (GAPs). The latter are master regulators of vesicular membrane transport, as they control the activity of membrane-associated Rab proteins. To better understand the role of the NS5A-TBC1D20 interaction in the HCV life cycle, we used a biochemical screen to identify the TBC1D20 Rab substrate. TBC1D20 was found to be the first known GAP for Rab1, which is implicated in the regulation of anterograde traffic between the endoplasmic reticulum and the Golgi complex. Mutation of amino acids implicated in Rab GTPase activation by other TBC domain-containing GAPs abrogated the ability of TBC1D20 to activate Rab1 GTPase. Overexpression of TBC1D20 blocked the transport of exogenous vesicular stomatitis virus G protein from the endoplasmic reticulum, validating the involvement of TBC1D20 in this pathway. Rab1 depletion significantly decreased HCV RNA levels, suggesting a role for Rab1 in HCV replication. These results highlight a novel mechanism by which viruses can hijack host cell machinery and suggest an attractive model whereby the NS5A-TBC1D20 interaction may promote viral membrane-associated RNA replication.

  View details for DOI 10.1074/jbc.M705221200

  View details for Web of Science ID 000251458300026

  View details for PubMedID 17901050

• Mechanisms of resistance to antiviral agents. In Manual of clinical microbiology, 9th edition, Murray PR ed, Baron EJ ed, Jorgensen JH ed, Pfaller MA ed, Tenover FC ed, and Yolken RH ed. American Society of Microbiology. Shafer RW, Einav S, Chou S 2007: 1689-04
• A nucleotide binding motif in hepatitis C virus (HCV) NS4B mediates HCV RNA replication JOURNAL OF VIROLOGY Einav, S., Elazar, M., Danieli, T., Glenn, J. S. 2004; 78 (20): 11288-11295

  Abstract

  Hepatitis C virus (HCV) is a major cause of viral hepatitis. There is no effective therapy for most patients. We have identified a nucleotide binding motif (NBM) in one of the virus's nonstructural proteins, NS4B. This structural motif binds and hydrolyzes GTP and is conserved across HCV isolates. Genetically disrupting the NBM impairs GTP binding and hydrolysis and dramatically inhibits HCV RNA replication. These results have exciting implications for the HCV life cycle and novel antiviral strategies.

  View details for Web of Science ID 000224229000045

  View details for PubMedID 15452248

• Prenylation inhibitors: a novel class of antiviral agents JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY Einav, S., Glenn, J. S. 2003; 52 (6): 883-886

  Abstract

  Prenylation is a site-specific lipid modification of proteins. Although first described for a variety of cellular proteins, it has become apparent that viruses can also make use of this post-translational modification provided by their host cells. Depriving a virus access to prenylation can have dramatic effects on the targeted virus's life cycle. Selective pharmacological inhibitors of prenylating enzymes have been developed and shown to have potent antiviral effects in both in vitro and in vivo systems. Because prenylation inhibitors target a host cell function, are available in oral form and are surprisingly well tolerated in human trials, these compounds represent an attractive new class of antiviral agents with potential for broad-spectrum activity. After a brief outline of host cell prenylation pathways, we review below the development of prenylation inhibition as an antiviral strategy applied to a prototype target, hepatitis delta virus (HDV), and discuss the potential application of prenylation inhibitors to a broad range of other viruses.

  View details for DOI 10.1093/jac/dkg490

  View details for Web of Science ID 000187227000001

  View details for PubMedID 14613953

• Immunopathogenesis of hepatitis C virus in the immunosuppressed host. Transplant infectious disease Einav, S., Koziel, M. J. 2002; 4 (2): 85-92

  Abstract

  The prevalence of chronic hepatitis C virus (HCV) infection among various groups of immunosuppressed patients is high. These groups include patients co-infected with human immunodeficiency virus (HIV), recipients of organ transplants, and those with hypogammaglobulinemia. The liver disease in the immunosuppressed host is typically severe with an unusually rapid progression to cirrhosis. This is somewhat paradoxical, as the classical model for HCV-induced liver disease assumes that cell-mediated immune responses induce liver injury. It is likely that a combination of viral-related factors and host-related factors plays a role in this accelerated natural history of HCV. Data are accumulating in immunocompromised hosts that address the immunopathogenesis of liver injury, although there are still fundamental gaps in our understanding of this process. In this review, we will focus on our current understanding of the mechanisms of liver injury and how it relates to the accelerated liver disease progression in immunocompromised hosts.

  View details for PubMedID 12220245

• Complement C4 is protective for lupus disease independent of C3 JOURNAL OF IMMUNOLOGY Einav, S., Pozdnyakova, O. O., Ma, M. H., Carroll, M. C. 2002; 168 (3): 1036-1041

  Abstract

  The role of complement C3 in mediating systemic lupus erythematosus (SLE) was examined using a double-knockout C3(null)C4(null) Fas (CD95)-deficient mouse model. Results from this study reveal significant lymphadenopathy, splenomegaly, elevated titers of anti-nuclear Abs and anti-dsDNA Abs, an increased number of anti-dsDNA-producing cells in ELISPOT assay, as well as severe glomerulonephritis in the double-deficient mice. Based on these clinical, serological, and histological parameters, we find that autoimmune disease in the double-knockout group is similar in severity to that in C4(null) lpr mice, but not to that in C3(null) lpr mice. The development of severe SLE in the absence of both classical and alternative complement pathways suggests that it is the absence of C4, and not the presence of C3, that is critical in SLE pathogenesis. Thus, complement C4 provides an important protective role against the development of SLE.

  View details for Web of Science ID 000173429300010

  View details for PubMedID 11801636