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Dunuweera AN, Dunuweera SP, Ranganathan K. A Comprehensive Exploration of Bioluminescence Systems, Mechanisms, and Advanced Assays for Versatile Applications. Biochem Res Int 2024; 2024:8273237. [PMID: 38347947 PMCID: PMC10861286 DOI: 10.1155/2024/8273237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/10/2023] [Accepted: 01/21/2024] [Indexed: 02/15/2024] Open
Abstract
Bioluminescence has been a fascinating natural phenomenon of light emission from living creatures. It happens when the enzyme luciferase facilitates the oxidation of luciferin, resulting in the creation of an excited-state species that emits light. Although there are many bioluminescent systems, few have been identified. D-luciferin-dependent systems, coelenterazine-dependent systems, Cypridina luciferin-based systems, tetrapyrrole-based luciferins, bacterial bioluminescent systems, and fungal bioluminescent systems are natural bioluminescent systems. Since different bioluminescence systems, such as various combinations of luciferin-luciferase pair reactions, have different light emission wavelengths, they benefit industrial applications such as drug discovery, protein-protein interactions, in vivo imaging in small animals, and controlling neurons. Due to the expression of luciferase and easy permeation of luciferin into most cells and tissues, bioluminescence assays are applied nowadays with modern technologies in most cell and tissue types. It is a versatile technique in a variety of biomedical research. Furthermore, there are some investigated blue-sky research projects, such as bioluminescent plants and lamps. This review article is mainly based on the theory of diverse bioluminescence systems and their past, present, and future applications.
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Affiliation(s)
| | | | - K. Ranganathan
- Department of Botany, University of Jaffna, Jaffna 40000, Sri Lanka
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Sasaki M, Anindita PD, Phongphaew W, Carr M, Kobayashi S, Orba Y, Sawa H. Development of a rapid and quantitative method for the analysis of viral entry and release using a NanoLuc luciferase complementation assay. Virus Res 2017; 243:69-74. [PMID: 29074234 DOI: 10.1016/j.virusres.2017.10.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 10/06/2017] [Accepted: 10/20/2017] [Indexed: 11/24/2022]
Abstract
Subviral particles (SVPs) self-assemble and are released from cells transfected with expression plasmids encoding flavivirus structural proteins. Flavivirus-like particles (VLPs), consisting of flavivirus structural proteins and a subgenomic replicon, can enter cells and cause single-round infections. Neither SVPs or VLPs possess complete viral RNA genomes, therefore are replication-incompetent systems; however, they retain the capacity to fuse and bud from target cells and follow the same maturation process as whole virions. SVPs and VLPs have been previously employed in studies analyzing entry and release steps of viral life cycles. In this study, we have developed quantitative methods for the detection of cellular entry and release of SVPs and VLPs by applying a luciferase complementation assay based on the high affinity interaction between the split NanoLuc luciferase protein, LgBiT and the small peptide, HiBiT. We introduced HiBiT into the structural protein of West Nile virus and generated SVPs and VLPs harboring HiBiT (SVP-HiBiT and VLP-HiBiT, respectively). As SVP-HiBiT emitted strong luminescence upon exposure to LgBiT and its substrate, the nascently budded SVP-HiBiT in the supernatant was readily quantified by luminometry. Similarly, the cellular entry of VLP-HiBiT generated luminescence when VLP-HiBiT was infected into LgBiT-expressing cells. These methods utilizing SVP-HiBiT and VLP-HiBiT will facilitate research into life cycles of flaviviruses, including WNV.
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Affiliation(s)
- Michihito Sasaki
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Paulina D Anindita
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Wallaya Phongphaew
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Michael Carr
- Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0020, Japan; National Virus Reference Laboratory, University College of Dublin, Dublin 4, Ireland
| | - Shintaro Kobayashi
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Yasuko Orba
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Hirofumi Sawa
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0020, Japan; Global Virus Network, Baltimore, MD 21201, USA.
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Functional Interplay Between Murine Leukemia Virus Glycogag, Serinc5, and Surface Glycoprotein Governs Virus Entry, with Opposite Effects on Gammaretroviral and Ebolavirus Glycoproteins. mBio 2016; 7:mBio.01985-16. [PMID: 27879338 PMCID: PMC5120145 DOI: 10.1128/mbio.01985-16] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gammaretroviruses, such as murine leukemia viruses (MLVs), encode, in addition to the canonical Gag, Pol, and Env proteins that will form progeny virus particles, a protein called “glycogag” (glycosylated Gag). MLV glycogag contains the entire Gag sequence plus an 88-residue N-terminal extension. It has recently been reported that glycogag, like the Nef protein of HIV-1, counteracts the antiviral effects of the cellular protein Serinc5. We have found, in agreement with prior work, that glycogag strongly enhances the infectivity of MLVs with some Env proteins but not those with others. In contrast, however, glycogag was detrimental to MLVs carrying Ebolavirus glycoprotein. Glycogag could be replaced, with respect to viral infectivity, by the unrelated S2 protein of equine infectious anemia virus. We devised an assay for viral entry in which virus particles deliver the Cre recombinase into cells, leading to the expression of a reporter. Data from this assay showed that both the positive and the negative effects of glycogag and S2 upon MLV infectivity are exerted at the level of virus entry. Moreover, transfection of the virus-producing cells with a Serinc5 expression plasmid reduced the infectivity and entry capability of MLV carrying xenotropic MLV Env, particularly in the absence of glycogag. Conversely, Serinc5 expression abrogated the negative effects of glycogag upon the infectivity and entry capability of MLV carrying Ebolavirus glycoprotein. As Serinc5 may influence cellular phospholipid metabolism, it seems possible that all of these effects on virus entry derive from changes in the lipid composition of viral membranes. Many murine leukemia viruses (MLVs) encode a protein called “glycogag.” The function of glycogag is not fully understood, but it can assist HIV-1 replication in the absence of the HIV-1 protein Nef under some circumstances. In turn, Nef counteracts the cellular protein Serinc5. Glycogag enhances the infectivity of MLVs with some but not all MLV Env proteins (which mediate viral entry into the host cell upon binding to cell surface receptors). We now report that glycogag acts by enhancing viral entry and that, like Nef, glycogag antagonizes Serinc5. Surprisingly, the effects of glycogag and Serinc5 upon the entry and infectivity of MLV particles carrying an Ebolavirus glycoprotein are the opposite of those observed with the MLV Env proteins. The unrelated S2 protein of equine infectious anemia virus (EIAV) is functionally analogous to glycogag in our experiments. Thus, three retroviruses (HIV-1, MLV, and EIAV) have independently evolved accessory proteins that counteract Serinc5.
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Burkard C, Bloyet LM, Wicht O, van Kuppeveld FJ, Rottier PJM, de Haan CAM, Bosch BJ. Dissecting virus entry: replication-independent analysis of virus binding, internalization, and penetration using minimal complementation of β-galactosidase. PLoS One 2014; 9:e101762. [PMID: 25025332 PMCID: PMC4099126 DOI: 10.1371/journal.pone.0101762] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 06/10/2014] [Indexed: 12/21/2022] Open
Abstract
Studies of viral entry into host cells often rely on the detection of post-entry parameters, such as viral replication or the expression of a reporter gene, rather than on measuring entry per se. The lack of assays to easily detect the different steps of entry severely hampers the analysis of this key process in virus infection. Here we describe novel, highly adaptable viral entry assays making use of minimal complementation of the E. coli β-galactosidase in mammalian cells. Enzyme activity is reconstituted when a small intravirion peptide (α-peptide) is complementing the inactive mutant form ΔM15 of β-galactosidase. The method allows to dissect and to independently detect binding, internalization, and fusion of viruses during host cell entry. Here we use it to confirm and extend current knowledge on the entry process of two enveloped viruses: vesicular stomatitis virus (VSV) and murine hepatitis coronavirus (MHV).
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Affiliation(s)
- Christine Burkard
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Louis-Marie Bloyet
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Oliver Wicht
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Frank J. van Kuppeveld
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Peter J. M. Rottier
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Cornelis A. M. de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Berend Jan Bosch
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Yang L, He D, Tang M, Li Z, Liu C, Xu L, Chen Y, Du H, Zhao Q, Zhang J, Cheng T, Xia N. Development of an enzyme-linked immunosorbent spot assay to measure serum-neutralizing antibodies against coxsackievirus B3. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2014; 21:312-20. [PMID: 24391137 PMCID: PMC3957675 DOI: 10.1128/cvi.00359-13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 12/23/2013] [Indexed: 11/20/2022]
Abstract
Coxsackievirus B3 (CVB3) is the most common pathogen that induces acute and chronic viral myocarditis in children. The cytopathic effect (CPE)-based neutralization test (Nt-CPE) and the plaque reduction neutralization test (PRNT) are the most common methods for measuring neutralizing antibody titers against CVB3 in blood serum samples. However, these two methods are inefficient for CVB3 vaccine clinical trials, which require the testing of a large number of serum specimens. In this study, we developed an efficient neutralization test based on the enzyme-linked immunospot (Nt-ELISPOT) assay for measuring CVB3-neutralizing antibodies. This modified ELISPOT assay was based on the use of a monoclonal antibody against the viral capsid protein VP1 to detect the cells that are infected with CVB3, which, after immunoperoxidase staining, are counted as spots using an automated ELISPOT analyzer. Using the modified ELISPOT assay, we characterized the infection kinetics of CVB3 and divided the infection process of CVB3 on a cluster of cells into four phases. The stability of the Nt-ELISPOT was then evaluated. We found that over a wide range of infectious doses (10(2) to 10(6.5)× 50% tissue culture infectious dose [TCID(50)] per well), the neutralizing titers of the sera were steady as long as they were tested during the log phase or the first half of the stationary phase of growth of the spots. We successfully shortened the testing period from 7 days to approximately 20 h. We also found that there was a good correlation (R(2) = 0.9462) between the Nt-ELISPOT and the Nt-CPE assays. Overall, the Nt-ELISPOT assay is a reliable and efficient method for measuring neutralizing antibodies in serum.
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Mather S, Scott S, Temperton N, Wright E, King B, Daly J. Current progress with serological assays for exotic emerging/re-emerging viruses. Future Virol 2013. [DOI: 10.2217/fvl.13.60] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Recent decades have witnessed an unprecedented rise in the outbreak occurrence of infectious and primarily zoonotic viruses. Contributing factors to this phenomenon include heightened global connectivity via air travel and international trade links, as well as man-made environmental alterations, such as deforestation and climate change, which all serve to bring humans into closer contact with animal reservoirs and alter the habitat of vectors, thus facilitating the transmission of viruses between species. Serological assays are integral to tracking the epidemiological spread of a virus and evaluating mass vaccination programs by quantifying neutralizing antibody responses raised against antigenic epitopes on the viral surface. However, conventional serological tests are somewhat marred by equipment and reagent costs, the necessity for high-containment laboratories for studying many emerging viruses, and interlaboratory variability, among other issues. This review details ‘next-generation’ assays aimed at addressing some of the persistent problems with viral serology, focusing on how manipulating the genomes of RNA viruses can produce attenuated or chimeric viruses that can be exploited as surrogate viruses in neutralization assays. Despite the undoubted promise of such novel serological platforms, it must be remembered that these assays have to withstand rigorous validation and standardization measures before they can play an integral role in curtailing the severity of future emerging virus outbreaks.
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Affiliation(s)
- Stuart Mather
- Viral Pseudotype Unit (Medway), School of Pharmacy, University of Kent, Chatham, Kent, ME4 4TB, UK
| | - Simon Scott
- Viral Pseudotype Unit (Medway), School of Pharmacy, University of Kent, Chatham, Kent, ME4 4TB, UK
| | - Nigel Temperton
- Viral Pseudotype Unit (Medway), School of Pharmacy, University of Kent, Chatham, Kent, ME4 4TB, UK
| | - Edward Wright
- Viral Pseudotype Unit (Fitzrovia), School of Life Sciences, University of Westminster, London, W1W 6UW, UK
| | - Barnabas King
- School of Veterinary Medicine & Science, University of Nottingham, Sutton Bonington Campus, Leicestershire, LE12 5RD, UK
| | - Janet Daly
- School of Veterinary Medicine & Science, University of Nottingham, Sutton Bonington Campus, Leicestershire, LE12 5RD, UK
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Ebolavirus requires acid sphingomyelinase activity and plasma membrane sphingomyelin for infection. J Virol 2012; 86:7473-83. [PMID: 22573858 DOI: 10.1128/jvi.00136-12] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Acid sphingomyelinase (ASMase) converts the lipid sphingomyelin (SM) to phosphocholine and ceramide and has optimum activity at acidic pH. Normally, ASMase is located in lysosomes and endosomes, but membrane damage or the interaction with some bacterial and viral pathogens can trigger its recruitment to the plasma membrane. Rhinovirus and measles viruses each require ASMase activity during early stages of infection. Both sphingomyelin and ceramide are important components of lipid rafts and are potent signaling molecules. Each plays roles in mediating macropinocytosis, which has been shown to be important for ebolavirus (EBOV) infection. Here, we investigated the role of ASMase and its substrate, SM, in EBOV infection. The work was performed at biosafety level 4 with wild-type virus with specificity and mechanistic analysis performed using virus pseudotypes and virus-like particles. We found that virus particles strongly associate with the SM-rich regions of the cell membrane and depletion of SM reduces EBOV infection. ASM-specific drugs and multiple small interfering RNAs strongly inhibit the infection by EBOV and EBOV glycoprotein pseudotyped viruses but not by the pseudotypes bearing the glycoprotein of vesicular stomatitis virus. Interestingly, the binding of virus-like particles to cells is strongly associated with surface-localized ASMase as well as SM-enriched sites. Our work suggests that ASMase activity and SM presence are necessary for efficient infection of cells by EBOV. The inhibition of this pathway may provide new avenues for drug treatment.
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GRB2 interaction with the ecotropic murine leukemia virus receptor, mCAT-1, controls virus entry and is stimulated by virus binding. J Virol 2011; 86:1421-32. [PMID: 22090132 DOI: 10.1128/jvi.05993-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
For retroviruses such as HIV-1 and murine leukemia virus (MLV), active receptor recruitment and trafficking occur during viral entry. However, the underlying mechanisms and cellular factors involved in the process are largely uncharacterized. The viral receptor for ecotropic MLV (eMLV), a classical model for retrovirus infection mechanisms and pathogenesis, is mouse cationic amino acid transporter 1 (mCAT-1). Growth factor receptor-bound protein 2 (GRB2) is an adaptor protein that has been shown to couple cell surface receptors, such as epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor, to intracellular signaling events. Here we examined if GRB2 could also play a role in controlling infection by retroviruses by affecting receptor function. The GRB2 RNA interference (RNAi)-mediated suppression of endogenous GRB2 resulted in a consistent and significant reduction of virus binding and membrane fusion. The binding between eMLV and cells promoted increased GRB2-mCAT-1 interactions, as detected by immunoprecipitation. Consistently, the increased colocalization of GRB2 and mCAT-1 signals was detected by confocal microscopy. This association was time dependent and paralleled the kinetics of cell-virus membrane fusion. Interestingly, unlike the canonical binding pattern seen for GRB2 and growth factor receptors, GRB2-mCAT-1 binding does not depend on the GRB2-SH2 domain-mediated recognition of tyrosine phosphorylation on the receptor. The inhibition of endogenous GRB2 led to a reduction in surface levels of mCAT-1, which was detected by immunoprecipitation and by a direct binding assay using a recombinant MLV envelope protein receptor binding domain (RBD). Consistent with this observation, the expression of a dominant negative GRB2 mutant (R86K) resulted in the sequestration of mCAT-1 from the cell surface into intracellular vesicles. Taken together, these findings suggest a novel role for GRB2 in ecotropic MLV entry and infection by facilitating mCAT-1 trafficking.
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Feng SZ, Cao WS, Liao M. The PI3K/Akt pathway is involved in early infection of some exogenous avian leukosis viruses. J Gen Virol 2011; 92:1688-1697. [DOI: 10.1099/vir.0.030866-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Avian leukosis virus (ALV) is an enveloped and oncogenic retrovirus. Avian leukosis caused by the members of ALV subgroups A, B and J has become one of the major problems challenging the poultry industry in China. However, the cellular factors such as signal transduction pathways involved in ALV infection are not well defined. In this study, our data demonstrated that ALV-J strain NX0101 infection in primary chicken embryo fibroblasts or DF-1 cells was correlated with the activity and phosphorylation of Akt. Akt activation was initiated at a very early stage of infection independently of NX0101 replication. The specific phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin could suppress Akt phosphorylation, indicating that NX0101-induced Akt phosphorylation is PI3K-dependent. ALV-A strain GD08 or ALV-B strain CD08 infection also demonstrated a similar profile of PI3K/Akt activation. Treatment of DF-1 cells with the drug 5-(N, N-hexamethylene) amiloride that inhibits the activity of chicken Na+/H+ exchanger type 1 significantly reduced Akt activation induced by NX0101, but not by GD08 and CD08. Akt activation triggered by GD08 or CD08 was abolished by clathrin-mediated endocytosis inhibitor chlorpromazine. Receptor-mediated endocytosis inhibitor dansylcadaverine had a negligible effect on all ALV-induced Akt phosphorylation. Moreover, viral replication of ALV was suppressed by LY294002 in a dose-dependent manner, which was due to the inhibition of virus infection by LY294002. These data suggest that the activation of the PI3K/Akt signalling pathway by exogenous ALV infection plays an important role in viral entry, yet the precise mechanism remains under further investigation.
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Affiliation(s)
- Shao-zhen Feng
- Key Laboratory of Animal Disease Control and Prevention of the Ministry of Agriculture, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Wei-sheng Cao
- Key Laboratory of Animal Disease Control and Prevention of the Ministry of Agriculture, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Ming Liao
- Key Laboratory of Animal Disease Control and Prevention of the Ministry of Agriculture, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
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Host-encoded reporters for the detection and purification of multiple enveloped viruses. J Virol Methods 2010; 167:178-85. [PMID: 20399809 PMCID: PMC2916077 DOI: 10.1016/j.jviromet.2010.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 03/31/2010] [Accepted: 04/08/2010] [Indexed: 02/07/2023]
Abstract
The identification of host cell factors for virus replication holds great promise for the development of new antiviral therapies. Recently, high-throughput screening methods have emerged as powerful tools to identify candidate host factors for therapeutic intervention. The development of assay systems suitable for large-scale automated screening is of particular importance for novel viruses with high pathogenic potential for which limited biological information can be developed in a short period of time. This report presents a general enzymatic reporter system for the detection and characterization of multiple enveloped viruses that does not rely on engineering of the virus. Instead, reporter enzymes are incorporated into virus particles by targeting to lipid microdomains in producer cells. The approach allows a variety of human pathogenic enveloped viruses to be detected by sensitive, inexpensive and automatable enzymatic assays. Tagged viruses can be purified quickly and efficiently by a magnetic bead-based capture method. The method allows general detection of enveloped viruses without prior reference to their sequence.
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Tayi VS, Bowen BD, Piret JM. Mathematical model of the rate-limiting steps for retrovirus-mediated gene transfer into mammalian cells. Biotechnol Bioeng 2010; 105:195-209. [DOI: 10.1002/bit.22515] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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12
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Melikyan GB. Common principles and intermediates of viral protein-mediated fusion: the HIV-1 paradigm. Retrovirology 2008; 5:111. [PMID: 19077194 PMCID: PMC2633019 DOI: 10.1186/1742-4690-5-111] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 12/10/2008] [Indexed: 12/20/2022] Open
Abstract
Enveloped viruses encode specialized fusion proteins which promote the merger of viral and cell membranes, permitting the cytosolic release of the viral cores. Understanding the molecular details of this process is essential for antiviral strategies. Recent structural studies revealed a stunning diversity of viral fusion proteins in their native state. In spite of this diversity, the post-fusion structures of these proteins share a common trimeric hairpin motif in which the amino- and carboxy-terminal hydrophobic domains are positioned at the same end of a rod-shaped molecule. The converging hairpin motif, along with biochemical and functional data, implies that disparate viral proteins promote membrane merger via a universal "cast-and-fold" mechanism. According to this model, fusion proteins first anchor themselves to the target membrane through their hydrophobic segments and then fold back, bringing the viral and cellular membranes together and forcing their merger. However, the pathways of protein refolding and the mechanism by which this refolding is coupled to membrane rearrangements are still not understood. The availability of specific inhibitors targeting distinct steps of HIV-1 entry permitted the identification of key conformational states of its envelope glycoprotein en route to fusion. These studies provided functional evidence for the direct engagement of the target membrane by HIV-1 envelope glycoprotein prior to fusion and revealed the role of partially folded pre-hairpin conformations in promoting the pore formation.
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Affiliation(s)
- Gregory B Melikyan
- Institute of Human Virology, Department of Microbiology and Immunology, University of Maryland School of Medicine, 725 W, Lombard St, Baltimore, MD 21201, USA.
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13
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Exosomes packaging APOBEC3G confer human immunodeficiency virus resistance to recipient cells. J Virol 2008; 83:512-21. [PMID: 18987139 DOI: 10.1128/jvi.01658-08] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The human cytidine deaminase APOBEC3G (A3G) is a part of a cellular defense system against human immunodeficiency virus type 1 (HIV-1) and other retroviruses. Antiretroviral activity of A3G can be severely blunted in the presence of the HIV-1 protein Vif. However, in some cells expressing the enzymatically active low-molecular-mass form of A3G, HIV-1 replication is restricted at preintegration steps, before accumulation of Vif. Here, we show that A3G can be secreted by cells in exosomes that confer resistance to both vif-defective and wild-type HIV-1 in exosome recipient cells. Our results also suggest that A3G is the major exosomal component responsible for the anti-HIV-1 activity of exosomes. However, enzymatic activity of encapsidated A3G does not correlate with the observed limited cytidine deamination in HIV-1 DNA, suggesting that A3G-laden exosomes restrict HIV-1 through a nonenzymatic mechanism. Real-time PCR quantitation demonstrated that A3G exosomes reduce accumulation of HIV-1 reverse transcription products and steady-state levels of HIV-1 Gag and Vif proteins. Our findings suggest that A3G exosomes could be developed into a novel class of anti-HIV-1 therapeutics.
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Saeed MF, Kolokoltsov AA, Freiberg AN, Holbrook MR, Davey RA. Phosphoinositide-3 kinase-Akt pathway controls cellular entry of Ebola virus. PLoS Pathog 2008; 4:e1000141. [PMID: 18769720 PMCID: PMC2516934 DOI: 10.1371/journal.ppat.1000141] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 08/01/2008] [Indexed: 11/18/2022] Open
Abstract
The phosphoinositide-3 kinase (PI3K) pathway regulates diverse cellular activities related to cell growth, migration, survival, and vesicular trafficking. It is known that Ebola virus requires endocytosis to establish an infection. However, the cellular signals that mediate this uptake were unknown for Ebola virus as well as many other viruses. Here, the involvement of PI3K in Ebola virus entry was studied. A novel and critical role of the PI3K signaling pathway was demonstrated in cell entry of Zaire Ebola virus (ZEBOV). Inhibitors of PI3K and Akt significantly reduced infection by ZEBOV at an early step during the replication cycle. Furthermore, phosphorylation of Akt-1 was induced shortly after exposure of cells to radiation-inactivated ZEBOV, indicating that the virus actively induces the PI3K pathway and that replication was not required for this induction. Subsequent use of pseudotyped Ebola virus and/or Ebola virus-like particles, in a novel virus entry assay, provided evidence that activity of PI3K/Akt is required at the virus entry step. Class 1A PI3Ks appear to play a predominant role in regulating ZEBOV entry, and Rac1 is a key downstream effector in this regulatory cascade. Confocal imaging of fluorescently labeled ZEBOV indicated that inhibition of PI3K, Akt, or Rac1 disrupted normal uptake of virus particles into cells and resulted in aberrant accumulation of virus into a cytosolic compartment that was non-permissive for membrane fusion. We conclude that PI3K-mediated signaling plays an important role in regulating vesicular trafficking of ZEBOV necessary for cell entry. Disruption of this signaling leads to inappropriate trafficking within the cell and a block in steps leading to membrane fusion. These findings extend our current understanding of Ebola virus entry mechanism and may help in devising useful new strategies for treatment of Ebola virus infection.
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Affiliation(s)
- Mohammad F. Saeed
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Western Regional Center of Excellence in Biodefense and Emerging Infectious Diseases Research, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Andrey A. Kolokoltsov
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Alexander N. Freiberg
- Western Regional Center of Excellence in Biodefense and Emerging Infectious Diseases Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Michael R. Holbrook
- Western Regional Center of Excellence in Biodefense and Emerging Infectious Diseases Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute of Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Robert A. Davey
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Western Regional Center of Excellence in Biodefense and Emerging Infectious Diseases Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute of Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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15
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Asokan A, Johnson JS, Li C, Samulski RJ. Bioluminescent virion shells: new tools for quantitation of AAV vector dynamics in cells and live animals. Gene Ther 2008; 15:1618-22. [PMID: 18668144 DOI: 10.1038/gt.2008.127] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Current technologies for visualizing infectious pathways of viruses rely on fluorescent labeling of capsid proteins by chemical conjugation or genetic manipulation. For noninvasive in vivo imaging of such agents in mammalian tissue, we engineered bioluminescent Gaussia luciferase-tagged Adeno-associated viral (gLuc/AAV) vectors. The enzyme was incorporated into recombinant AAV serotypes 1, 2 and 8 capsids by fusing to the N-terminus of the VP2 capsid subunit to yield bioluminescent virion shells. The gLuc/AAV vectors were used to quantify kinetics of cell-surface-binding by AAV2 capsids in vitro. Bioluminescent virion shells displayed an exponential decrease in luminescent signal following cellular uptake in vitro. A similar trend was observed following intramuscular injection in vivo, although the rate of decline in bioluminescent signal varied markedly between AAV serotypes. gLuc/AAV1 and gLuc/AAV8 vectors displayed rapid decrease in bioluminescent signal to background levels within 30 min, whereas the signal from gLuc/AAV2 vectors persisted for over 2 h. Bioluminescent virion shells might be particularly useful in quantifying dynamics of viral vector uptake in cells and peripheral tissues in live animals.
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Affiliation(s)
- A Asokan
- Department of Pharmacology, Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7352, USA
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16
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Alphavirus production is inhibited in neurofibromin 1-deficient cells through activated RAS signalling. Virology 2008; 377:133-42. [PMID: 18485440 DOI: 10.1016/j.virol.2008.03.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 03/14/2008] [Accepted: 03/21/2008] [Indexed: 11/24/2022]
Abstract
Virus-host interactions essential for alphavirus pathogenesis are poorly understood. To address this shortcoming, we coupled retrovirus insertional mutagenesis and a cell survival selection strategy to generate clonal cell lines broadly resistant to Sindbis virus (SINV) and other alphaviruses. Resistant cells had significantly impaired SINV production relative to wild-type (WT) cells, although virus binding and fusion events were similar in both sets of cells. Analysis of the retroviral integration sites identified the neurofibromin 1 (NF1) gene as disrupted in alphavirus-resistant cell lines. Subsequent analysis indicated that expression of NF1 was significantly reduced in alphavirus-resistant cells. Importantly, independent down-regulation of NF1 expression in WT HEK 293 cells decreased virus production and increased cell viability during SINV infection, relative to infected WT cells. Additionally, we observed hyperactive RAS signalling in the resistant HEK 293 cells, which was anticipated because NF1 is a negative regulator of RAS. Expression of constitutively active RAS (HRAS-G12V) in a WT HEK 293 cell line resulted in a marked delay in virus production, compared with infected cells transfected with parental plasmid or dominant-negative RAS (HRAS-S17N). This work highlights novel host cell determinants required for alphavirus pathogenesis and suggests that RAS signalling may play an important role in neuronal susceptibility to SINV infection.
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17
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Kottke T, Qiao J, Diaz RM, Ahmed A, Vroman B, Thompson J, Sanchez-Perez L, Vile R. The perforin-dependent immunological synapse allows T-cell activation-dependent tumor targeting by MLV vector particles. Gene Ther 2006; 13:1166-77. [PMID: 16625245 DOI: 10.1038/sj.gt.3302722] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have reported that retroviral particles adhered to the surface of antigen-specific T cells can be carried to metastases following adoptive transfer in vivo, a process we have called viral hitch hiking. Following antigen-driven T-cell accumulation at tumors, viral particles productively infect tumor cells via envelope/receptor dependent interactions ('hand on' of virus from the T cell to the tumor cell). We describe here a second envelope/receptor independent pathway of viral hand on from T cells, dependent on T-cell activation. We show that the endosomolytic property of perforin promotes release of viral particles from endosomes into which they are co-delivered along with cytotoxic granules from the activated T cell. Therefore, hand on of MLV particles lacking any envelope can be used for in vivo delivery of vectors, where targeting is at the extremely specific level of recognition of antigen by the T-cell receptor, thereby dispensing with the need to engineer viral envelopes. These data reveal a novel pathway by which MLV viral particles exploit a functional immunological synapse and present new opportunities both to improve the efficacy of adoptive T-cell transfer and to target vectors for systemic gene delivery.
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Affiliation(s)
- T Kottke
- Molecular Medicine Program and Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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18
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Negi SS, Kolokoltsov AA, Schein CH, Davey RA, Braun W. Determining functionally important amino acid residues of the E1 protein of Venezuelan equine encephalitis virus. J Mol Model 2006; 12:921-9. [PMID: 16607494 DOI: 10.1007/s00894-006-0101-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 01/05/2006] [Indexed: 10/24/2022]
Abstract
A new method for predicting interacting residues in protein complexes, InterProSurf, was applied to the E1 envelope protein of Venezuelan equine encephalitis (VEEV). Monomeric and trimeric models of VEEV-E1 were constructed with our MPACK program, using the crystal structure of the E1 protein of Semliki forest virus as a template. An alignment of the E1 sequences from representative alphavirus sequences was used to determine physical chemical property motifs (likely functional areas) with our PCPMer program. Information on residue variability, propensity to be in protein interfaces, and surface exposure on the model was combined to predict surface clusters likely to interact with other viral or cellular proteins. Mutagenesis of these clusters indicated that the predictions accurately detected areas crucial for virus infection. In addition to the fusion peptide area in domain 2, at least two other surface areas play an important role in virus infection. We propose that these may be sites of interaction between the E1-E1 and E1-E2 subdomains of the envelope proteins that are required to assemble the functional unit. The InterProSurf method is, thus, an important new tool for predicting viral protein interactions. These results can aid in the design of new vaccines against alphaviruses and other viruses.
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Affiliation(s)
- Surendra S Negi
- Sealy Center for Structural Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-0857, USA
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19
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Saeed MF, Kolokoltsov AA, Davey RA. Novel, rapid assay for measuring entry of diverse enveloped viruses, including HIV and rabies. J Virol Methods 2006; 135:143-50. [PMID: 16584792 DOI: 10.1016/j.jviromet.2006.02.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 02/10/2006] [Accepted: 02/20/2006] [Indexed: 11/29/2022]
Abstract
Entry is the first and essential step in virus replication and is a target for therapeutic intervention. However, current knowledge on entry mechanism for the majority of viruses is poor, partly due to lack of a simple, sensitive and accurate entry assay that can be applied to diverse viruses. To overcome this obstacle, a novel contents-mixing-based virus entry assay is described that can be broadly applied to many enveloped viruses. By fusing firefly luciferase to the HIV Nef protein, luciferase was directly packaged into HIV particles pseudotyped with envelope proteins of diverse viruses including HIV, rabies and others. Upon cell entry, the luciferase-fusion protein was released into the cell cytoplasm, reacted with its substrates and was detected by light emission. The assay was validated by demonstrating its versatility in measuring virus entry. Entry was detected much more rapidly (in real-time) with higher sensitivity (a multiplicity of infection <0.1 gives a robust signal) and lower background (signal/noise ration >1000) than other comparable assays. In addition to its utility in studying virus entry mechanisms, the assay will aid in screening potential entry/fusion inhibitors and in diagnosis of virus infections.
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Affiliation(s)
- Mohammad F Saeed
- Department of Microbiology and Immunology, and Western Regional Center for Excellence in Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1019, USA
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20
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Kolokoltsov AA, Fleming EH, Davey RA. Venezuelan equine encephalitis virus entry mechanism requires late endosome formation and resists cell membrane cholesterol depletion. Virology 2006; 347:333-42. [PMID: 16427678 DOI: 10.1016/j.virol.2005.11.051] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 09/27/2005] [Accepted: 11/30/2005] [Indexed: 10/25/2022]
Abstract
Virus envelope proteins determine receptor utilization and host range. The choice of receptor not only permits specific targeting of cells that express it, but also directs the virus into specific endosomal trafficking pathways. Disrupting trafficking can result in loss of virus infectivity due to redirection of virions to non-productive pathways. Identification of the pathway or pathways used by a virus is, thus, important in understanding virus pathogenesis mechanisms and for developing new treatment strategies. Most of our understanding of alphavirus entry has focused on the Old World alphaviruses, such as Sindbis and Semliki Forest virus. In comparison, very little is known about the entry route taken by more pathogenic New World alphaviruses. Here, we use a novel contents mixing assay to identify the cellular requirements for entry of a New World alphavirus, Venezuelan equine encephalitis virus (VEEV). Expression of dominant negative forms of key endosomal trafficking genes shows that VEEV must access clathrin-dependent endocytic vesicles for membrane fusion to occur. Unexpectedly, the exit point is different from Old World alphaviruses that leave from early endosomes. Instead, VEEV also requires functional late endosomes. Furthermore, unlike the Old World viruses, VEEV entry is insensitive to cholesterol sequestration from cell membranes and may reflect a need to access an endocytic compartment that lacks cholesterol. This indicates fundamental differences in the entry route taken by VEEV compared to Old World alphaviruses.
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Affiliation(s)
- Andrey A Kolokoltsov
- Department of Microbiology and Immunology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
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21
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Lehmann MJ, Sherer NM, Marks CB, Pypaert M, Mothes W. Actin- and myosin-driven movement of viruses along filopodia precedes their entry into cells. ACTA ACUST UNITED AC 2005; 170:317-25. [PMID: 16027225 PMCID: PMC2171413 DOI: 10.1083/jcb.200503059] [Citation(s) in RCA: 305] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Viruses have often been observed in association with the dense microvilli of polarized epithelia as well as the filopodia of nonpolarized cells, yet whether interactions with these structures contribute to infection has remained unknown. Here we show that virus binding to filopodia induces a rapid and highly ordered lateral movement, “surfing” toward the cell body before cell entry. Virus cell surfing along filopodia is mediated by the underlying actin cytoskeleton and depends on functional myosin II. Any disruption of virus cell surfing significantly reduces viral infection. Our results reveal another example of viruses hijacking host machineries for efficient infection by using the inherent ability of filopodia to transport ligands to the cell body.
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Affiliation(s)
- Maik J Lehmann
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
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22
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Markosyan RM, Cohen FS, Melikyan GB. Time-resolved imaging of HIV-1 Env-mediated lipid and content mixing between a single virion and cell membrane. Mol Biol Cell 2005; 16:5502-13. [PMID: 16195349 PMCID: PMC1289397 DOI: 10.1091/mbc.e05-06-0496] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A method has been developed to follow fusion of individual pseudotyped virus expressing HIV-1 Env to cells by time-resolved fluorescence microscopy. Viral envelopes were labeled with a fluorescent lipid dye (DiD) and virus content was rendered visible by incorporating a Gag-GFP chimera. The Gag-GFP is naturally cleaved to the much smaller NC-GFP fragment in the mature virions. NC-GFP was readily released upon permeabilization of the viral envelope, whereas the capsid was retained. The NC-GFP thus provides a relatively small and mobile aqueous marker to follow viral content transfer. In fusion experiments, virions were bound to cells at low temperature, and fusion was synchronously triggered by a temperature jump. DiD transferred from virions to cells without a significant lag after the temperature jump. Some virions released DiD but retained NC-GFP. Surprisingly, the fraction of lipid mixing events yielding NC-GFP transfer was dependent on the type of target cell: of three infectable cell lines, only one permitted NC-GFP transfer within minutes of raising temperature. NC-GFP release did not correlate with the level of CD4 or coreceptor expression in the target cells. The data indicate that fusion pores formed by HIV-1 Env can remain small for a relatively long time before they enlarge.
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Affiliation(s)
- Ruben M Markosyan
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL 60612
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23
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Top D, de Antueno R, Salsman J, Corcoran J, Mader J, Hoskin D, Touhami A, Jericho MH, Duncan R. Liposome reconstitution of a minimal protein-mediated membrane fusion machine. EMBO J 2005; 24:2980-8. [PMID: 16079913 PMCID: PMC1201348 DOI: 10.1038/sj.emboj.7600767] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Accepted: 07/13/2005] [Indexed: 11/08/2022] Open
Abstract
Biological membrane fusion is dependent on protein catalysts to mediate localized restructuring of lipid bilayers. A central theme in current models of protein-mediated membrane fusion involves the sequential refolding of complex homomeric or heteromeric protein fusion machines. The structural features of a new family of fusion-associated small transmembrane (FAST) proteins appear incompatible with existing models of membrane fusion protein function. While the FAST proteins function to induce efficient cell-cell fusion when expressed in transfected cells, it was unclear whether they function on their own to mediate membrane fusion or are dependent on cellular protein cofactors. Using proteoliposomes containing the purified p14 FAST protein of reptilian reovirus, we now show via liposome-cell and liposome-liposome fusion assays that p14 is both necessary and sufficient for membrane fusion. Stoichiometric and kinetic analyses suggest that the relative efficiency of p14-mediated membrane fusion rivals that of the more complex cellular and viral fusion proteins, making the FAST proteins the simplest known membrane fusion machines.
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Affiliation(s)
- Deniz Top
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Roberto de Antueno
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jayme Salsman
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jennifer Corcoran
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jamie Mader
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - David Hoskin
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ahmed Touhami
- Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Manfred H Jericho
- Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Roy Duncan
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5. Tel.: +1 902 494 6770; Fax: +1 902 494 5125; E-mail:
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24
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Kolokoltsov AA, Weaver SC, Davey RA. Efficient functional pseudotyping of oncoretroviral and lentiviral vectors by Venezuelan equine encephalitis virus envelope proteins. J Virol 2005; 79:756-63. [PMID: 15613303 PMCID: PMC538582 DOI: 10.1128/jvi.79.2.756-763.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Murine oncoretroviruses and lentiviruses pseudotyped with envelope proteins of alphaviruses have shown great potential in providing broad-host-range, stable vectors for gene therapy. Unlike vesicular stomatitis virus G protein-pseudotyped vectors, they are not neutralized by complement and do not appear to cause significant tissue damage. Here we report the production of murine oncoretroviral and lentiviral vectors pseudotyped with the envelope proteins of Venezuelan equine encephalitis virus (VEEV). When optimized, these pseudotypes achieve titers of 10(6) CFU/ml, which is 5- to 10-fold higher than for previous vectors pseudotyped with envelope proteins from other alphaviruses. They can also be concentrated or stored frozen without significant loss of infectivity. Consistent with the tropism of the envelope donor, they transduce a broad array of human cell types, including lung epithelial cells, neuronal cells, lymphocytes, and fibroblasts. Infection is blocked by agents that inhibit endosomal acidification and by neutralizing antibodies against VEEV. These observations indicate that the pseudotypes present native epitopes on their surface and enter through a VEEV envelope-dependent, pH-sensitive mechanism. The fact that the pseudotypes are unaffected by sera reactive to other alphaviruses indicates that they may be useful when successive gene therapies are required in the presence of an active immune response. In this case, having an array of alphavirus-based vectors with similar cell tropisms would be highly advantageous. These vectors may also be useful in diagnostic assays in which infectious VEEV is undesirable but immune reactivity to native epitopes is required.
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Affiliation(s)
- Andrey A Kolokoltsov
- Department of Microbiology and Immunology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555, USA
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