201
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Bossart KN, Wang LF, Flora MN, Chua KB, Lam SK, Eaton BT, Broder CC. Membrane fusion tropism and heterotypic functional activities of the Nipah virus and Hendra virus envelope glycoproteins. J Virol 2002; 76:11186-98. [PMID: 12388678 PMCID: PMC136767 DOI: 10.1128/jvi.76.22.11186-11198.2002] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nipah virus (NiV) and Hendra virus (HeV) are novel paramyxoviruses from pigs and horses, respectively, that are responsible for fatal zoonotic infections of humans. The unique genetic and biological characteristics of these emerging agents has led to their classification as the prototypic members of a new genus within the Paramyxovirinae subfamily called HENIPAVIRUS: These viruses are most closely related to members of the genus Morbillivirus and infect cells through a pH-independent membrane fusion event mediated by the actions of their attachment (G) and fusion (F) glycoproteins. Understanding their cell biological features and exploring the functional characteristics of the NiV and HeV glycoproteins will help define important properties of these emerging viruses and may provide new insights into paramyxovirus membrane fusion mechanisms. Using a recombinant vaccinia virus system and a quantitative assay for fusion, we demonstrate NiV glycoprotein function and the same pattern of cellular tropism recently reported for HeV-mediated fusion, suggesting that NiV likely uses the same cellular receptor for infection. Fusion specificity was verified by inhibition with a specific antiserum or peptides derived from the alpha-helical heptads of NiV or HeV F. Like that of HeV, NiV-mediated fusion also requires both F and G. Finally, interactions between the glycoproteins of the paramyxoviruses have not been well defined, but here we show that the NiV and HeV glycoproteins are capable of highly efficient heterotypic functional activity with each other. However, no heterotypic activity was observed with envelope glycoproteins of the morbilliviruses Measles virus and Canine distemper virus.
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Affiliation(s)
- Katharine N Bossart
- Department of Microbiology and Immunology, Uniformed Services University, Bethesda, Maryland 20814, USA
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202
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Torrence PF, Powell LD. The quest for an efficacious antiviral for respiratory syncytial virus. Antivir Chem Chemother 2002; 13:325-44. [PMID: 12718405 DOI: 10.1177/095632020201300601] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalized and the elderly. To date, ribavirin (Virazole) remains the only therapeutic agent approved for the treatment of RSV. The prophylactic administration of palivizumab is problematic and costly. The quest for an efficacious RSV antiviral has produced a greater understanding of the viral fusion process, a new hypothesis for the mechanism of action of ribavirin, and a promising antisense strategy combining the 2'-5' oligoadenylate antisense (2-5A-antisense) approach and RSV genomics.
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Affiliation(s)
- Paul F Torrence
- Department of Chemistry, Northern Arizona University, Flagstaff, Ariz., USA.
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203
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San Román K, Villar E, Muñoz-Barroso I. Mode of action of two inhibitory peptides from heptad repeat domains of the fusion protein of Newcastle disease virus. Int J Biochem Cell Biol 2002; 34:1207-20. [PMID: 12127571 DOI: 10.1016/s1357-2725(02)00045-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Peptides derived from heptad repeat (HR) sequences of viral fusion proteins from several enveloped viruses have been shown to inhibit virus-mediated membrane fusion but the mechanism remains unknown. To further investigate this, the inhibition mechanism of two HR-derived peptides from the fusion protein of the paramyxovirus Newcastle disease virus (NDV) was investigated. Peptide N24 (residues 145-168) derived from HR1 was found to be 145-fold more inhibitory in a syncytium assay than peptide C24 (residues 474-496), derived from HR2. Both peptides failed to block lipid-mixing between R18-labeled virus and cells. None of the peptides interfered with the binding of hemagglutinin-neuraminidase (HN) protein to the target cells, as demonstrated by hemagglutining assays. When both peptides were mixed at equimolar concentrations, their inhibitory effect was abolished. In addition, both peptides induced the aggregation of negatively charged and zwitterionic phospholipid membranes. The ability of the peptides to interact with each other in solution suggests that these peptides may bind to the opposite HR region on the protein whereas their ability to interact with membranes as well as their failure to block lipid transfer suggest a second binding site. Taken together these results, suggest a mode of action for C24 and N24 in which both peptides have two different targets on the F protein: the opposite HR sequence and their corresponding domains.
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Affiliation(s)
- K San Román
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 109, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
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204
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Medinas RJ, Lambert DM, Tompkins WA. C-Terminal gp40 peptide analogs inhibit feline immunodeficiency virus: cell fusion and virus spread. J Virol 2002; 76:9079-86. [PMID: 12186891 PMCID: PMC136458 DOI: 10.1128/jvi.76.18.9079-9086.2002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1), gp160, is synthesized as a protein precursor that when proteolytically cleaved yields two subunits, gp120 and gp41. gp120 is the surface glycoprotein on HIV-1 responsible for binding to CD4, and gp41 is the transmembrane glycoprotein involved in the membrane fusion process. gp41 is divided into the N-terminal fusion peptide, the heptad repeat 1 (HR1) and HR2 regions, and the C-terminal transmembrane region, which are collectively responsible for virus fusion and entry into the cell. Synthetic peptides derived from the HR2 and HR1 regions of HIV-1(LAI) have been shown to prevent virus-cell fusion and infection in vitro. In phase II clinical trials in HIV patients, data revealed that T20 has antiviral efficacy and is well tolerated. Similar results were obtained in vitro with HIV-2 and simian immunodeficiency virus, supporting the conservation of the gp41 ectodomain among lentiviruses. Feline immunodeficiency virus (FIV) infection in the cat has been used as a model to develop potential antivirals for HIV. To determine if synthetic gp40 analogs capable of inhibiting FIV infection could be identified, 15 overlapping 35-amino-acid peptides derived from the C-terminal HR2 domain of FIV gp40 were synthesized. These peptides were tested for efficacy against FIV in a syncytium-forming assay with FIV-infected CrFK cells and HeLa cells expressing the FIV receptor CXCR4. Several peptides exhibited activity at the nanogram level. Antiviral activity was confirmed by suppression of reverse transcriptase in a FIV feline CD4(+)-T-cell (FCD4-E) acute-infection assay. These data demonstrate that synthetic peptides derived from the HR2 domain of the FIV gp41 protein are effective inhibitors of FIV infection.
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Affiliation(s)
- R J Medinas
- Immunology Program, North Carolina State University, Raleigh 27606, USA
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205
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Abstract
Respiratory syncytial virus (RSV) is the most important cause of respiratory tract infection in infants. We have an incomplete understanding of the reasons why some infants are more severely affected by RSV than others. There is no effective antiviral treatment for the infection. Advances in our understanding of the biology of RSV, particularly in relation to the attachment protein G and the fusion protein F, have revealed potential targets for new antiviral therapies and vaccine development. In response to RSV infection an intense inflammatory response is triggered, mediated initially by the infected airway epithelial cells. Cell mediated responses are important in controlling the extent of infection and in viral clearance. Humoral responses are important in protection. There is early evidence that genetic variation of the host response can influence the outcome of RSV-induced bronchiolitis.
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Affiliation(s)
- D Hacking
- International Child Health Group, Department of Paediatrics, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK.
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206
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Smith BJ, Lawrence MC, Colman PM. Modelling the structure of the fusion protein from human respiratory syncytial virus. Protein Eng Des Sel 2002; 15:365-71. [PMID: 12034856 DOI: 10.1093/protein/15.5.365] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The fusion protein of respiratory syncytial virus (RSV-F) is responsible for fusion of virion with host cells and infection of neighbouring cells through the formation of syncytia. A three-dimensional model structure of RSV-F was derived by homology modelling from the structure of the equivalent protein in Newcastle disease virus (NDV). Despite very low sequence homology between the two structures, most features of the model appear to have high credibility, although a few small regions in RSV-F whose secondary structure is predicted to be different to that in NDV are likely to be poorly modelled. The organization of individual residues identified in escape mutants against monoclonal antibodies correlates well with known antigenic sites. The location of residues involved in point mutations in several drug-resistant variants is also examined.
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Affiliation(s)
- Brian J Smith
- Biomolecular Research Institute, 343 Royal Parade, Parkville, Victoria 3052, Australia
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207
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Abstract
Viral envelope glycoproteins promote viral infection by mediating the fusion of the viral membrane with the host-cell membrane. Structural and biochemical studies of two viral glycoproteins, influenza hemagglutinin and HIV-1 envelope protein, have led to a common model for viral entry. The fusion mechanism involves a transient conformational species that can be targeted by therapeutic strategies. This mechanism of infectivity is likely utilized by a wide variety of enveloped viruses for which similar therapeutic interventions should be possible.
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Affiliation(s)
- D M Eckert
- Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, M.I.T., Cambridge, Massachusetts 02142, USA.
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208
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Huntley CC, Weiss WJ, Gazumyan A, Buklan A, Feld B, Hu W, Jones TR, Murphy T, Nikitenko AA, O'Hara B, Prince G, Quartuccio S, Raifeld YE, Wyde P, O'Connell JF. RFI-641, a potent respiratory syncytial virus inhibitor. Antimicrob Agents Chemother 2002; 46:841-7. [PMID: 11850270 PMCID: PMC127488 DOI: 10.1128/aac.46.3.841-847.2002] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human respiratory syncytial virus (RSV), a paramyxovirus, is a major cause of acute upper and lower respiratory tract infections in infants, young children, and adults. RFI-641 is a novel anti-RSV agent with potent in vitro and in vivo activity. RFI-641 is active against both RSV type A and B strains. The viral specificity and the large therapeutic window of RFI-641 (>100-fold) indicate that the antiviral activity of the compound is not due to adverse effects on normal cells. The potent in vitro activity of RFI-641 can be translated to efficacy in vivo: RFI-641 is efficacious when administered prophylactically by the intranasal route in mice, cotton rats, and African green monkeys. RFI-641 is also efficacious when administered therapeutically (24 h postinfection) in the monkey model. Mechanism of action studies indicate that RFI-641 blocks viral F protein-mediated fusion and cell syncytium formation.
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Affiliation(s)
- Clayton C Huntley
- Department of Infectious Disease and Chemical Sciences, Wyeth-Ayerst Research, Pearl River, New York 10965, USA.
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209
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Sudo K, Konno K, Watanabe W, Shigeta S, Yokota T. Mechanism of selective inhibition of respiratory syncytial virus by a benzodithiin compound (RD3-0028). Microbiol Immunol 2002; 45:531-7. [PMID: 11529559 DOI: 10.1111/j.1348-0421.2001.tb02654.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RD3-0028, a compound with a benzodithiin structure, was found to be a potent inhibitor of respiratory syncytial virus (RSV) replication. Its action is specific; no activity is seen against influenza A virus, measles virus, herpes simplex virus type 1 or 2, or human cytomegalovirus. A time-dependent drug addition experiment indicated that the antiviral activity occurs in the late stage of the RSV replication cycle, since this compound completely inhibited syncytium formation even when added up to 16 hr after the infection of cell monolayers at an MOI of 3. RD3-0028 had no direct virucidal effect on RSV. Western blotting analysis showed that RD3-0028 significantly decreased the amount of RSV proteins released into the cell culture medium. Moreover, five independent isolates of the RSV long strain were selected for growth in RD3-0028 (5-20 microg/ml). These resistant viruses were more than 80-fold less sensitive to RD3-0028 than the long strain. The F gene segment of each of these viruses was sequenced and in each case the mutant RNA segment contained at least one sequence alteration, converting asparagine 276 to tyrosine (F1 protein). These results suggest that RD3-0028 inhibits RSV replication by interfering with intracellular processing of the RSV fusion protein, or a step immediately thereafter, leading to loss of infectivity.
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Affiliation(s)
- K Sudo
- Rational Drug Design Laboratories, Fukushima, Fukushima, Japan.
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210
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Abstract
A decade ago, just five drugs were licensed for the treatment of viral infections. Since then, greater understanding of viral life cycles, prompted in particular by the need to combat human immunodeficiency virus, has resulted in the discovery and validation of several targets for therapeutic intervention. Consequently, the current antiviral repertoire now includes more than 30 drugs. But we still lack effective therapies for several viral infections, and established treatments are not always effective or well tolerated, highlighting the need for further refinement of antiviral drug design and development. Here, I describe the rationale behind current and future drug-based strategies for combating viral infections.
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Affiliation(s)
- Erik De Clercq
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
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211
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Bossart KN, Wang LF, Eaton BT, Broder CC. Functional expression and membrane fusion tropism of the envelope glycoproteins of Hendra virus. Virology 2001; 290:121-35. [PMID: 11882997 DOI: 10.1006/viro.2001.1158] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hendra virus (HeV) is an emerging paramyxovirus first isolated from cases of severe respiratory disease that fatally affected both horses and humans. Understanding the mechanisms of host cell infection and cross-species transmission is an important step in addressing the risk posed by such emerging pathogens. We have initiated studies to characterize the biological properties of the HeV envelope glycoproteins. Recombinant vaccinia viruses encoding the HeV F and G open reading frames were generated and glycoprotein expression was verified by metabolic labeling and detection using specific antisera. Glycoprotein function and cellular tropism were examined with a quantitative assay for HeV-mediated membrane fusion. Fusion specificity was verified through specific inhibition by anti-HeV antiserum and a peptide corresponding to one of the alpha-helical heptad repeats of F. HeV requires both F and G to mediate fusion. Permissive target cells have been identified, including cell lines derived from cat, bat, horse, human, monkey, mouse, and rabbit. Fusion negative cell types have also been identified. Protease treatments of the target cells abolished fusion activity, suggesting that the virus is employing a cell-surface protein as its receptor.
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Affiliation(s)
- K N Bossart
- Department of Microbiology, Uniformed Services University, Bethesda, Maryland 20814, USA
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212
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McGinnes LW, Sergel T, Chen H, Hamo L, Schwertz S, Li D, Morrison TG. Mutational analysis of the membrane proximal heptad repeat of the newcastle disease virus fusion protein. Virology 2001; 289:343-52. [PMID: 11689056 DOI: 10.1006/viro.2001.1123] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Paramyxovirus fusion proteins have two heptad repeat domains, HR1 and HR2, that have been implicated in the fusion activity of the protein. Peptides from these two domains form a six-stranded, coiled-coil with the HR1 sequences forming a central trimer and three molecules of the HR2 helix located within the grooves in the central trimer (Baker et al., 1999, Mol. Cell 3, 309; Zhao et al. 2000, Proc. Natl. Acad. Sci. USA 97, 14172). Nonconservative mutations were made in the HR2 domain of the Newcastle disease virus fusion protein in residues that are likely to form contacts with the HR1 core trimer. These residues form the hydrophobic face of the helix and adjacent residues ("a" and "g" positions in the HR2 helical wheel structure). Mutant proteins were characterized for effects on synthesis, steady-state levels, proteolytic cleavage, and surface expression as well as fusion activity as measured by syncytia formation, content mixing, and lipid mixing. While all mutant proteins were transport competent and proteolytically cleaved, these mutations did variously affect fusion activity of the protein. Nonconservative mutations in the "g" position had no effect on fusion. In contrast, single changes in the middle "a" position of HR2 inhibited lipid mixing, content mixing, and syncytia formation. A single mutation in the more carboxyl-terminal "a" position had minimal effects on lipid mixing but did inhibit content mixing and syncytia formation. These results are consistent with the idea that the HR2 domain is involved in posttranslational interactions with HR1 that mediate the close approach of membranes. These results also suggest that the HR2 domain, particularly the carboxyl-terminal region, plays an additional role in fusion, a role related to content mixing and syncytia formation.
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Affiliation(s)
- L W McGinnes
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01532, USA
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213
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Schneider-Schaulies J, ter Meulen V, Schneider-Schaulies S. Measles virus interactions with cellular receptors: consequences for viral pathogenesis. J Neurovirol 2001; 7:391-9. [PMID: 11582511 DOI: 10.1080/135502801753170246] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Although CNS complications occurring early and late after acute measles are a serious problem and often fatal, the transient immunosuppression lasting for several weeks after the rash is the major cause of measles-related morbidity and mortality worldwide. This review is focused on the interactions of measles virus (MV) with cellular receptors on neural and lymphoid cells which are important elements in viral pathogenesis. First, the cognate MV receptors, CD46 and CD150, are important components of viral tropism by mediating binding and entry. Second, however, additional unknown cellular surface molecules may (independently of viral uptake) after interaction with the MV glycoprotein complex act as signaling molecules and thereby modulate cellular survival, proliferation, and specific functions.
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Affiliation(s)
- J Schneider-Schaulies
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany.
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214
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Sergel TA, McGinnes LW, Morrison TG. Mutations in the fusion peptide and adjacent heptad repeat inhibit folding or activity of the Newcastle disease virus fusion protein. J Virol 2001; 75:7934-43. [PMID: 11483738 PMCID: PMC115037 DOI: 10.1128/jvi.75.17.7934-7943.2001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Paramyxovirus fusion proteins have two heptad repeat domains, HR1 and HR2, which have been implicated in the fusion activity of the protein. Peptides with sequences from these two domains form a six-stranded coiled coil, with the HR1 sequences forming a central trimer (K. A. Baker, R. E. Dutch, R. A. Lamb, and T. S. Jardetzky, Mol. Cell 3:309-319, 1999; X. Zhao, M. Singh, V. N. Malashkevich, and P. S. Kim, Proc. Natl. Acad. Sci. USA 97:14172-14177, 2000). We have extended our previous mutational analysis of the HR1 domain of the Newcastle disease virus fusion protein, focusing on the role of the amino acids forming the hydrophobic core of the trimer, amino acids in the "a" and "d" positions of the helix from amino acids 123 to 182. Both conservative and nonconservative point mutations were characterized for their effects on synthesis, stability, proteolytic cleavage, and surface expression. Mutant proteins expressed on the cell surface were characterized for fusion activity by measuring syncytium formation, content mixing, and lipid mixing. We found that all mutations in the "a" position interfered with proteolytic cleavage and surface expression of the protein, implicating the HR1 domain in the folding of the F protein. However, mutation of five of seven "d" position residues had little or no effect on surface expression but, with one exception at residue 175, did interfere to various extents with the fusion activity of the protein. One of these "d" mutations, at position 154, interfered with proteolytic cleavage, while the rest of the mutants were cleaved normally. That most "d" position residues do affect fusion activity argues that a stable HR1 trimer is required for formation of the six-stranded coiled coil and, therefore, optimal fusion activity. That most of the "d" position mutations do not block folding suggests that formation of the core trimer may not be required for folding of the prefusion form of the protein. We also found that mutations within the fusion peptide, at residue 128, can interfere with folding of the protein, implicating this region in folding of the molecule. No characterized mutation enhanced fusion.
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Affiliation(s)
- T A Sergel
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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215
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Walker MA. Novel antiviral molecules. Drug Discov Today 2001; 6:747-749. [PMID: 11445467 DOI: 10.1016/s1359-6446(01)01860-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- M A. Walker
- Bristol-Myers Squibb, Pharmaceutical Research Institute, 06492, Tel: +1 203 677 6686; fax: +1 203 677 7702, Wallingford CT, USA
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216
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McGinnes L, Sergel T, Reitter J, Morrison T. Carbohydrate modifications of the NDV fusion protein heptad repeat domains influence maturation and fusion activity. Virology 2001; 283:332-42. [PMID: 11336558 DOI: 10.1006/viro.2001.0899] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The amino acid sequence of the fusion protein (F) of Newcastle disease virus (NDV) has six potential N-linked glycosylation addition sites, five in the ectodomain (at amino acids 85, 191, 366, 447, and 471) and one in the cytoplasmic domain at amino acid 542. Two of these sites, at positions 191 and 471, are within heptad repeat (HR) domains implicated in fusion activity of the protein. To determine glycosylation site usage as well as the function of added carbohydrate, each site was mutated by substituting alanine for the serine or threonine in the addition signal. The sizes of the resulting mutant proteins, expressed in Cos cells, showed that sites at amino acids 85, 191, 366, and 471 are used. This conclusion was verified by comparing sizes of mutant proteins missing all four used sites with that of unglycosylated F protein. The role of each added oligosaccharide in the structure and function of the F protein was determined by characterizing stability, proteolytic cleavage, surface expression, and fusion activity of the mutant proteins. Elimination of the site in F(2) at amino acid 85 had the most detrimental effect, decreasing cleavage, stability, and surface expression as well as fusion activity. The protein missing the site at 191, at the carboxyl terminus of the HR1 domain, also showed modestly reduced surface expression and negligible fusion activity. Proteins missing sites at 366 and 471 (within HR2) were expressed at nearly wild-type levels but had decreased fusion activity. These results suggest that all carbohydrate side chains, individually, influence the folding or activity of the NDV F protein. Importantly, carbohydrate modifications of the HR domains impact fusion activity of the protein.
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Affiliation(s)
- L McGinnes
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01655, USA
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217
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Chen L, Gorman JJ, McKimm-Breschkin J, Lawrence LJ, Tulloch PA, Smith BJ, Colman PM, Lawrence MC. The structure of the fusion glycoprotein of Newcastle disease virus suggests a novel paradigm for the molecular mechanism of membrane fusion. Structure 2001; 9:255-66. [PMID: 11286892 DOI: 10.1016/s0969-2126(01)00581-0] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Membrane fusion within the Paramyxoviridae family of viruses is mediated by a surface glycoprotein termed the "F", or fusion, protein. Membrane fusion is assumed to involve a series of structural transitions of F from a metastable (prefusion) state to a highly stable (postfusion) state. No detail is available at the atomic level regarding the metastable form of these proteins or regarding the transitions accompanying fusion. RESULTS The three-dimensional structure of the fusion protein of Newcastle disease virus (NDV-F) has been determined. The trimeric NDV-F molecule is organized into head, neck, and stalk regions. The head is comprised of a highly twisted beta domain and an additional immunoglobulin-like beta domain. The neck is formed by the C-terminal extension of the heptad repeat region HR-A, capped by a four-helical bundle. The C terminus of HR-A is encased by a further helix HR-C and a 4-stranded beta sheet. The stalk is formed by the remaining visible portion of HR-A and by polypeptide immediately N-terminal to the C-terminal heptad repeat region HR-B. An axial channel extends through the head and neck and is fenestrated by three large radial channels located approximately at the head-neck interface. CONCLUSION We propose that prior to fusion activation, the hydrophobic fusion peptides in NDV-F are sequestered within the radial channels within the head, with the central HR-A coiled coil being only partly formed. Fusion activation then involves, inter alia, the assembly of a complete HR-A coiled coil, with the fusion peptides and transmembrane anchors being brought into close proximity. The structure of NDV-F is fundamentally different than that of influenza virus hemagglutinin, in that the central coiled coil is in the opposite orientation with respect to the viral membrane.
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Affiliation(s)
- L Chen
- Biomolecular Research Institute, Parkville, Victoria 3052, Australia
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218
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Dutch RE, Hagglund RN, Nagel MA, Paterson RG, Lamb RA. Paramyxovirus fusion (F) protein: a conformational change on cleavage activation. Virology 2001; 281:138-50. [PMID: 11222104 DOI: 10.1006/viro.2000.0817] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The fusion (F) protein of the paramyxovirus SV5 promotes both virus-cell and cell-cell fusion. Recently, the atomic structure at 1.4 A of an extremely thermostable six-helix bundle core complex consisting of two heptad repeat regions of the F protein has been described (K. A. Baker, R. E. Dutch, R. A. Lamb, and T. S Jardetsky, Mol. Cell 3, 309-319, 1999). To analyze the conformations of the F protein at various stages of the membrane fusion process and to understand further the role of formation of the six-helix bundle core complex in promotion of membrane fusion, antibodies to peptides corresponding to regions of the F protein were obtained. Major changes in F protein antibody recognition were found after cleavage of the precursor protein F(0) to the fusogenically active disulfide-linked heterodimer, F(1) + F(2), and antibodies directed against the heptad repeat regions recognized only the uncleaved form. A monoclonal antibody directed against the F protein showed increased recognition at the cell surface of the cleaved form of the F protein as compared to uncleaved F protein, again indicating changes in conformation between the uncleaved and cleaved forms of the F protein. Anti-peptide antibodies specific for the heptad repeat regions were unable to precipitate a synthetic protein that consisted of the heptad repeat regions separated only by a small spacer, suggesting that the antibodies are unable to recognize their target regions when the heptad repeats are present in the six-helix bundle core complex. Taken together, these data indicate that the six-helix bundle core complex is not present in the precursor molecule F(0) and that significant conformational changes occur subsequent to cleavage of the F protein.
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Affiliation(s)
- R E Dutch
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA
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219
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Gallaher WR, DiSimone C, Buchmeier MJ. The viral transmembrane superfamily: possible divergence of Arenavirus and Filovirus glycoproteins from a common RNA virus ancestor. BMC Microbiol 2001; 1:1. [PMID: 11208257 PMCID: PMC29097 DOI: 10.1186/1471-2180-1-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2000] [Accepted: 02/09/2001] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Recent studies of viral entry proteins from influenza, measles, human immunodeficiency virus, type 1 (HIV-1), and Ebola virus have shown, first with molecular modeling, and then X-ray crystallographic or other biophysical studies, that these disparate viruses share a coiled-coil type of entry protein. RESULTS Structural models of the transmembrane glycoproteins (GP-2) of the Arenaviruses, lymphochoriomeningitis virus (LCMV) and Lassa fever virus, are presented, based on consistent structural propensities despite variation in the amino acid sequence. The principal features of the model, a hydrophobic amino terminus, and two antiparallel helices separated by a glycosylated, antigenic apex, are common to a number of otherwise disparate families of enveloped RNA viruses. Within the first amphipathic helix, demonstrable by circular dichroism of a peptide fragment, there is a highly conserved heptad repeat pattern proposed to mediate multimerization by coiled-coil interactions. The amino terminal 18 amino acids are 28% identical and 50% highly similar to the corresponding region of Ebola, a member of the Filovirus family. Within the second, charged helix just prior to membrane insertion there is also high similarity over the central 18 amino acids in corresponding regions of Lassa and Ebola, which may be further related to the similar region of HIV-1 defining a potent antiviral peptide analogue. CONCLUSIONS These findings indicate a common pattern of structure and function among viral transmembrane fusion proteins from a number of virus families. Such a pattern may define a viral transmembrane superfamily that evolved from a common precursor eons ago.
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Affiliation(s)
- William R Gallaher
- Department of Microbiology, Immunology & Parasitology, Neuroscience Center of Excellence and Stanley S. Scott Cancer Center, Louisiana State University Medical Center, New Orleans, LA, USA 70112-1393
| | - Christopher DiSimone
- Division of Virology, Department of Neuropharmacology, The Scripps Research Institute, La Jolla, California, USA 92037
| | - Michael J Buchmeier
- Division of Virology, Department of Neuropharmacology, The Scripps Research Institute, La Jolla, California, USA 92037
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220
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Abstract
Human immunodeficiency virus type-1 (HIV-1) membrane fusion is promoted by the formation of a trimer-of-hairpins structure that brings the amino- and carboxyl-terminal regions of the gp41 envelope glycoprotein ectodomain into close proximity. Peptides derived from the carboxyl-terminal region (called C-peptides) potently inhibit HIV-1 entry by binding to the gp41 amino-terminal region. To test the converse of this inhibitory strategy, we designed a small protein, denoted 5-Helix, that binds the C-peptide region of gp41. The 5-Helix protein displays potent (nanomolar) inhibitory activity against diverse HIV-1 variants and may serve as the basis for a new class of antiviral agents. The inhibitory activity of 5-Helix also suggests a strategy for generating an HIV-1 neutralizing antibody response that targets the carboxyl-terminal region of the gp41 ectodomain.
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Affiliation(s)
- M J Root
- Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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221
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Zhao X, Singh M, Malashkevich VN, Kim PS. Structural characterization of the human respiratory syncytial virus fusion protein core. Proc Natl Acad Sci U S A 2000; 97:14172-7. [PMID: 11106388 PMCID: PMC18890 DOI: 10.1073/pnas.260499197] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human respiratory syncytial virus (HRSV) is a major cause of a number of severe respiratory diseases, including bronchiolitis and pneumonia, in infants and young children. The HRSV F protein, a glycoprotein essential for viral entry, is a primary target for vaccine and drug development. Two heptad-repeat regions within the HRSV F sequence were predicted by the computer program learncoil-vmf. These regions are thought to form trimer-of-hairpins-like structures, similar to those found in the fusion proteins of several enveloped viruses. The hairpin structure likely brings the viral and cellular membranes into close apposition, thereby facilitating membrane fusion and subsequent viral entry. Here, we show that peptides, denoted HR-N and HR-C, corresponding to the heptad-repeat regions from the N-terminal and C-terminal segments of the HRSV F protein, respectively, form a stable alpha-helical trimer of heterodimers. The HRSV N/C complex was crystallized and its x-ray structure was determined at 2.3-A resolution. As anticipated, the complex is a six-helix bundle in which the HR-N peptides form a three-stranded, central coiled coil, and the HR-C peptides pack in an antiparallel manner into hydrophobic grooves on the coiled-coil surface. There is remarkable structural similarity between the HRSV N/C complex and the fusion protein core of other viruses, including HIV-1 gp41. In addition, earlier work has shown that HRSV HR-C peptides, like the HIV-1 gp41 C peptides, inhibit viral infection. Thus, drug discovery and vaccine development strategies aimed at inhibiting viral entry by blocking hairpin formation may be applied to the inhibition of HRSV.
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Affiliation(s)
- X Zhao
- Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA
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222
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Watanabe S, Takada A, Watanabe T, Ito H, Kida H, Kawaoka Y. Functional importance of the coiled-coil of the Ebola virus glycoprotein. J Virol 2000; 74:10194-201. [PMID: 11024148 PMCID: PMC102058 DOI: 10.1128/jvi.74.21.10194-10201.2000] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ebola virus contains a single glycoprotein (GP) that is responsible for receptor binding and membrane fusion and is proteolytically cleaved into disulfide-linked GP1 and GP2 subunits. The GP2 subunit possesses a coiled-coil motif, which plays an important role in the oligomerization and fusion activity of other viral GPs. To determine the functional significance of the coiled-coil motif of GP2, we examined the effects of peptides corresponding to the coiled-coil motif of GP2 on the infectivity of a mutant vesicular stomatitis virus (lacking the receptor-binding/fusion protein) pseudotyped with the Ebola virus GP. A peptide corresponding to the C-terminal helix reduced the infectivity of the pseudotyped virus. We next introduced alanine substitutions into hydrophobic residues in the coiled-coil motif to identify residues important for GP function. None of the substitutions affected GP oligomerization, but some mutations, two in the N-terminal helix and all in the C-terminal helix, reduced the ability of GP to confer infectivity to the mutant vesicular stomatitis virus without affecting the transport of GP to the cell surface, its incorporation into virions, and the production of virus particles. These results indicate that the coiled-coil motif of GP2 plays an important role in facilitating the entry of Ebola virus into host cells and that peptides corresponding to this region could act as efficient antiviral agents.
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Affiliation(s)
- S Watanabe
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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223
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Lawless-Delmedico MK, Sista P, Sen R, Moore NC, Antczak JB, White JM, Greene RJ, Leanza KC, Matthews TJ, Lambert DM. Heptad-repeat regions of respiratory syncytial virus F1 protein form a six-membered coiled-coil complex. Biochemistry 2000; 39:11684-95. [PMID: 10995236 DOI: 10.1021/bi000471y] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Respiratory Syncytial Virus (RSV) fusogenic glycoprotein F(1) was characterized using biochemical and biophysical techniques. Two heptad-repeat (HR) regions within F(1) were shown to interact. Proteinase-K digestion experiments highlight the HR1 region (located proximal to the fusion peptide sequence) of the F(1) protein to which an HR2-derived (located proximal to the membrane-spanning domain) peptide binds, thus protecting both the protein and peptide from digestion. Solution-phase analysis of HR1-derived peptides shows that these peptides adopt helical secondary structure as measured by circular dichroism. Sedimentation equilibrium studies indicate that these HR1 peptides self-associate in a monomer/trimer equilibrium with an association constant of 5.2 x 10(8) M(-2). In contrast, HR2-derived peptides form random monomers in solution. CD analysis of mixtures containing peptides from the two regions demonstrate their propensity to interact and form a very stable (T(m) = 87 degrees C), helical (86% helicity) complex comprised of three HR1 and three HR2 members.
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224
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Abstract
This review evaluates the current situation and long-term prospects for containment of human respiratory syncytial virus (HRSV) infection and bronchiolitis in infancy. The biology and immunopathology of HRSV infection are complex. Initial attempts to control HRSV infection using a conventional formalin-inactivated vaccine had the unexpected outcome that the disease was potentiated in some vaccinees experiencing natural HRSV infection at a later date. Much effort has been devoted to defining the nature of protective immunity, and several candidate sub-unit and live attenuated vaccines have been developed by empirical and semi-empirical routes, and most recently by reverse genetics. None has yet received approval for clinical use, and attention has switched from active to passive immunization. Both concentrated human immune globulin (RespiGam) and a humanized monoclonal antibody (Palivizumab) have been approved for clinical use. On grounds of cost-effectiveness these treatments are recommended only for treatment of high-risk infants. An effective antiviral is not yet available.
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MESH Headings
- Antibodies, Monoclonal/therapeutic use
- Antibodies, Monoclonal, Humanized
- Antiviral Agents/therapeutic use
- Bronchiolitis, Viral/immunology
- Bronchiolitis, Viral/prevention & control
- Bronchiolitis, Viral/virology
- Child
- Child, Preschool
- Humans
- Immunoglobulins, Intravenous/therapeutic use
- Infant
- Infant, Newborn
- Palivizumab
- RNA, Antisense/therapeutic use
- Respiratory Syncytial Virus Infections/immunology
- Respiratory Syncytial Virus Infections/prevention & control
- Respiratory Syncytial Virus, Human
- Viral Vaccines
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Affiliation(s)
- C R Pringle
- Biological Sciences Department, University of Warwick, Coventry, CV4 7AL, UK.
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225
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Weidmann A, Fischer C, Ohgimoto S, Rüth C, ter Meulen V, Schneider-Schaulies S. Measles virus-induced immunosuppression in vitro is independent of complex glycosylation of viral glycoproteins and of hemifusion. J Virol 2000; 74:7548-53. [PMID: 10906208 PMCID: PMC112275 DOI: 10.1128/jvi.74.16.7548-7553.2000] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/1999] [Accepted: 05/18/2000] [Indexed: 01/01/2023] Open
Abstract
Expression of the measles virus (MV) F/H complex on the surface of viral particles, infected cells, or cells transfected to express these proteins (presenter cells [PC]) is necessary and sufficient to induce proliferative arrest in both human and rodent lymphoid cells (responder cells [RC]). This inhibition was found to occur independent of apoptosis and soluble mediators excluded by a pore size filter of 200 nm released from either PC or RC. We now show that reactive oxygen intermediates which might be released by RC or PC also do not contribute to MV-induced immunosuppression in vitro. Using an inhibitor of Golgi-resident mannosidases (deoxymannojirimycin), we found that complex glycosylation of the F and H proteins is not required for the induction of proliferative arrest of RC. As revealed by our previous studies, proteolytic cleavage of the MV F protein precursor into its F1 and F2 subunits, but not of F/H-mediated cellular fusion, was found to be required, since fusion-inhibitory peptides such as Z-D-Phe-L-Phe-Gly (Z-fFG) did not interfere with the induction of proliferative inhibition. We now show that Z-fFG inhibits cellular fusion at the stage of hemifusion by preventing lipid mixing of the outer membrane layer. These results provide strong evidence for a receptor-mediated signal elicited by the MV F/H complex which can be uncoupled from its fusogenic activity is required for the induction of proliferative arrest of human lymphocytes.
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Affiliation(s)
- A Weidmann
- Institute for Virology and Immunobiology, University of Würzburg, D-97078 Würzburg, Germany
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226
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Matthews JM, Young TF, Tucker SP, Mackay JP. The core of the respiratory syncytial virus fusion protein is a trimeric coiled coil. J Virol 2000; 74:5911-20. [PMID: 10846072 PMCID: PMC112087 DOI: 10.1128/jvi.74.13.5911-5920.2000] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Entry into the host cell by enveloped viruses is mediated by fusion (F) or transmembrane glycoproteins. Many of these proteins share a fold comprising a trimer of antiparallel coiled-coil heterodimers, where the heterodimers are formed by two discontinuous heptad repeat motifs within the proteolytically processed chain. The F protein of human respiratory syncytial virus (RSV; the major cause of lower respiratory tract infections in infants) contains two corresponding regions that are predicted to form coiled coils (HR1 and HR2), together with a third predicted heptad repeat (HR3) located in a nonhomologous position. In order to probe the structures of these three domains and ascertain the nature of the interactions between them, we have studied the isolated HR1, HR2, and HR3 domains of RSV F by using a range of biophysical techniques, including circular dichroism, nuclear magnetic resonance spectroscopy, and sedimentation equilibrium. HR1 forms a symmetrical, trimeric coiled coil in solution (K(3) approximately 2.2 x 10(11) M(-2)) which interacts with HR2 to form a 3:3 hexamer. The HR1-HR2 interaction domains have been mapped using limited proteolysis, reversed-phase high-performance liquid chromatography, and electrospray-mass spectrometry. HR2 in isolation exists as a largely unstructured monomer, although it exhibits a tendency to form aggregates with beta-sheet-like characteristics. Only a small increase in alpha-helical content was observed upon the formation of the hexamer. This suggests that the RSV F glycoprotein contains a domain that closely resembles the core structure of the simian parainfluenza virus 5 fusion protein (K. A. Baker, R. E. Dutch, R. A. Lamb, and T. S. Jardetzky, Mol. Cell 3:309-319, 1999). Finally, HR3 forms weak alpha-helical homodimers that do not appear to interact with HR1, HR2, or the HR1-HR2 complex. The results of these studies support the idea that viral fusion proteins have a common core architecture.
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Affiliation(s)
- J M Matthews
- Department of Biochemistry, University of Sydney, New South Wales Australia. j,
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227
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Respiratory syncytial virus: recent progress towards the discovery of effective prophylactic and therapeutic agents. Drug Discov Today 2000; 5:241-252. [PMID: 10825730 DOI: 10.1016/s1359-6446(00)01500-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Although respiratory syncytial virus (RSV) was discovered in 1955, the burden associated with this infectious agent on all population groups is only now beginning to be fully appreciated. The successful launch of the humanized monoclonal antibody Synagis (developed by MedImmune, Gaithersburg, MD, USA), as a prophylactic in September 1998 has helped to heighten awareness of the extent of mortality and morbidity associated with annual RSV epidemics. Small, drug-like molecules that would provide the clinician with effective and conveniently administered prophylactic and therapeutic agents for the prevention and treatment of RSV have not yet advanced into clinical studies. This review will summarize recent developments in the area of RSV drug discovery and development.
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228
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Sergel TA, McGinnes LW, Morrison TG. A single amino acid change in the Newcastle disease virus fusion protein alters the requirement for HN protein in fusion. J Virol 2000; 74:5101-7. [PMID: 10799584 PMCID: PMC110862 DOI: 10.1128/jvi.74.11.5101-5107.2000] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of a leucine heptad repeat motif between amino acids 268 and 289 in the structure and function of the Newcastle disease virus (NDV) F protein was explored by introducing single point mutations into the F gene cDNA. The mutations affected either folding of the protein or the fusion activity of the protein. Two mutations, L275A and L282A, likely interfered with folding of the molecule since these proteins were not proteolytically cleaved, were minimally expressed at the cell surface, and formed aggregates. L268A mutant protein was cleaved and expressed at the cell surface although the protein migrated slightly slower than wild type on polyacrylamide gels, suggesting an alteration in conformation or processing. L268A protein was fusion inactive in the presence or absence of HN protein expression. Mutant L289A protein was expressed at the cell surface and proteolytically cleaved at better than wild-type levels. Most importantly, this protein mediated syncytium formation in the absence of HN protein expression although HN protein enhanced fusion activity. These results show that a single amino acid change in the F(1) portion of the NDV F protein can alter the stringent requirement for HN protein expression in syncytium formation.
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Affiliation(s)
- T A Sergel
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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229
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Weidmann A, Maisner A, Garten W, Seufert M, ter Meulen V, Schneider-Schaulies S. Proteolytic cleavage of the fusion protein but not membrane fusion is required for measles virus-induced immunosuppression in vitro. J Virol 2000; 74:1985-93. [PMID: 10644371 PMCID: PMC111676 DOI: 10.1128/jvi.74.4.1985-1993.2000] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/1999] [Accepted: 11/22/1999] [Indexed: 11/20/2022] Open
Abstract
Immunosuppression induced by measles virus (MV) is associated with unresponsiveness of peripheral blood lymphocytes (PBL) to mitogenic stimulation ex vivo and in vitro. In mixed lymphocyte cultures and in an experimental animal model, the expression of the MV glycoproteins on the surface of UV-inactivated MV particles, MV-infected cells, or cells transfected to coexpress the MV fusion (F) and the hemagglutinin (H) proteins was found to be necessary and sufficient for this phenomenon. We now show that MV fusion-inhibitory peptides do not interfere with the induction of immunosuppression in vitro, indicating that MV F-H-mediated fusion is essentially not involved in this process. Proteolytic cleavage of MV F(0) protein by cellular proteases, such as furin, into the F(1)-F(2) subunits is, however, an absolute requirement, since (i) the inhibitory activity of MV-infected BJAB cells was significantly impaired in the presence of a furin-inhibitory peptide and (ii) cells expressing or viruses containing uncleaved F(0) proteins revealed a strongly reduced inhibitory activity which was improved following trypsin treatment. The low inhibitory activity of effector structures containing mainly F(0) proteins was not due to an impaired F(0)-H interaction, since both surface expression and cocapping efficiencies were similar to those found with the authentic MV F and H proteins. These results indicate that the fusogenic activity of the MV F-H complexes can be uncoupled from their immunosuppressive activity and that the immunosuppressive domains of these proteins are exposed only after proteolytic activation of the MV F(0) protein.
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Affiliation(s)
- A Weidmann
- Institute for Virology and Immunobiology, University of W]urzburg, D-97078 W]urzburg, Germany
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230
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Shigeta S. Recent progress in antiviral chemotherapy for respiratory syncytial virus infections. Expert Opin Investig Drugs 2000; 9:221-35. [PMID: 11060673 DOI: 10.1517/13543784.9.2.221] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The recent progress in antiviral chemotherapy against respiratory syncytial virus (RSV) infections was reviewed. RSV infections among high risk individuals, such as premature babies, infants with congenital disease of cardiopulmonary system or immune system and the aged, hospitalised patients with immunosuppressed status are threatened, with high mortality rates and thus need anti-viral chemotherapy. Clinical efficacy of ribavirin and humanized monoclonal antibody (mAb) against RSV infections as well as experimental reports of novel anti-RSV compounds under investigation such as membrane fusion inhibitors were introduced.
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Affiliation(s)
- S Shigeta
- Department of Microbiology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295, Japan
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231
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Pastey MK, Gower TL, Spearman PW, Crowe JE, Graham BS. A RhoA-derived peptide inhibits syncytium formation induced by respiratory syncytial virus and parainfluenza virus type 3. Nat Med 2000; 6:35-40. [PMID: 10613821 PMCID: PMC7095870 DOI: 10.1038/71503] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The fusion glycoproteins of human respiratory syncytial virus (RSV) and human parainfluenza virus type-3 (PIV-3) mediate virus entry and syncytium formation. Interaction between the fusion protein of RSV and RhoA, a small GTPase, facilitates virus-induced syncytium formation. We show here a RhoA-derived peptide inhibits RSV and syncytium formation induced by RSV and PIV-3, both in vitro by inhibition of cell-to-cell fusion and in vivo by reduction of peak titer by 2 log10 in RSV-infected mice. These findings indicate that the interaction between these two paramyxovirus fusion proteins and RhoA is an important target for new antiviral strategies.
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Affiliation(s)
- Manoj K. Pastey
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
| | - Tara L. Gower
- Department of Microbiology & Immunology, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
| | - Paul W. Spearman
- Department of Microbiology & Immunology, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
| | - James E. Crowe
- Department of Microbiology & Immunology, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
| | - Barney S. Graham
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
- Department of Microbiology & Immunology, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee USA
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232
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Kingsley DH, Behbahani A, Rashtian A, Blissard GW, Zimmerberg J. A discrete stage of baculovirus GP64-mediated membrane fusion. Mol Biol Cell 1999; 10:4191-200. [PMID: 10588652 PMCID: PMC25752 DOI: 10.1091/mbc.10.12.4191] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Viral fusion protein trimers can play a critical role in limiting lipids in membrane fusion. Because the trimeric oligomer of many viral fusion proteins is often stabilized by hydrophobic 4-3 heptad repeats, higher-order oligomers might be stabilized by similar sequences. There is a hydrophobic 4-3 heptad repeat contiguous to a putative oligomerization domain of Autographa californica multicapsid nucleopolyhedrovirus envelope glycoprotein GP64. We performed mutagenesis and peptide inhibition studies to determine if this sequence might play a role in catalysis of membrane fusion. First, leucine-to-alanine mutants within and flanking the amino terminus of the hydrophobic 4-3 heptad repeat motif that oligomerize into trimers and traffic to insect Sf9 cell surfaces were identified. These mutants retained their wild-type conformation at neutral pH and changed conformation in acidic conditions, as judged by the reactivity of a conformationally sensitive mAb. These mutants, however, were defective for membrane fusion. Second, a peptide encoding the portion flanking the GP64 hydrophobic 4-3 heptad repeat was synthesized. Adding peptide led to inhibition of membrane fusion, which occurred only when the peptide was present during low pH application. The presence of peptide during low pH application did not prevent low pH-induced conformational changes, as determined by the loss of a conformationally sensitive epitope. In control experiments, a peptide of identical composition but different sequence, or a peptide encoding a portion of the Ebola GP heptad motif, had no effect on GP64-mediated fusion. Furthermore, when the hemagglutinin (X31 strain) fusion protein of influenza was functionally expressed in Sf9 cells, no effect on hemagglutinin-mediated fusion was observed, suggesting that the peptide does not exert nonspecific effects on other fusion proteins or cell membranes. Collectively, these studies suggest that the specific peptide sequences of GP64 that are adjacent to and include portions of the hydrophobic 4-3 heptad repeat play a dynamic role in membrane fusion at a stage that is downstream of the initiation of protein conformational changes but upstream of lipid mixing.
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Affiliation(s)
- D H Kingsley
- Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1855, USA
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233
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Ghosh JK, Shai Y. Direct evidence that the N-terminal heptad repeat of Sendai virus fusion protein participates in membrane fusion. J Mol Biol 1999; 292:531-46. [PMID: 10497019 DOI: 10.1006/jmbi.1999.3097] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent studies have demonstrated the importance of heptad repeat regions within envelope proteins of viruses in mediating conformational changes at various stages of viral infection. However, it is not clear if heptad repeats have a direct role in the actual fusion event. Here we have synthesized, fluorescently labeled and functionally and structurally characterized a wild-type 70 residue peptide (SV-117) composed of both the fusion peptide and the N-terminal heptad repeat of Sendai virus fusion protein, two of its mutants, as well as the fusion peptide and heptad repeat separately. One mutation was introduced in the fusion peptide (G119K) and another in the heptad repeat region (I154K). Similar mutations have been shown to drastically reduce the fusogenic ability of the homologous fusion protein of Newcastle disease virus. We found that only SV-117 was active in inducing lipid mixing of egg phosphatidylcholine/phosphatidyiglycerol (PC/PG) large unilamellar vesicles (LUV), and not the mutants nor the mixture of the fusion peptide and the heptad repeat. Functional characterization revealed that SV-117, and to a lesser extent its two mutants, were potent inhibitors of Sendai virus-mediated hemolysis of red blood cells, while the fusion peptide and SV-150 were negligibly active alone or in a mixture. Hemagglutinin assays revealed that none of the peptides disturb the binding of virions to red blood cells. Further studies revealed that SV-117 and its mutants oligomerize similarly in solution and in membrane, and have similar potency in inducing vesicle aggregation. Circular dichroism and FTIR spectroscopy revealed a higher helical content for SV-117 compared to its mutants in 40 % tifluorethanol and in PC/PG multibilayer membranes, respectively, ATR-FTIR studies indicated that SV-117 lies more parallel with the surface of the membrane than its mutants. These observations suggest a direct role for the N-terminal heptad repeat in assisting the fusion peptide in mediating membrane fusion.
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Affiliation(s)
- J K Ghosh
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100, Israel
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234
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Estepa A, Fernandez-Alonso M, Coll JM. Structure, binding and neutralization of VHSV with synthetic peptides. Virus Res 1999; 63:27-34. [PMID: 10509713 DOI: 10.1016/s0168-1702(99)00055-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The phosphatidylserine binding region p2 of VHSV was characterized and was shown to be involved with fusion. Synthetic peptides corresponding to this region interact with phospholipids by penetrating into the membrane and changing to a beta sheet configuration. Computer modeling of this region shows the possible ways by which the interaction with the membranes can succeed. Inhibitory peptides are presently being sought by studying possible interactions within heptad repeats located in other regions of the G protein of VHSV. The heptad repeat region that includes the phosphatidylserine binding domain p2 has been cloned and preliminary experiments show that under certain conditions, peptides from this region can inhibit VHSV infectivity.
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Affiliation(s)
- A Estepa
- Departmento Bioquimica y Biologia Molecular, Universidad Miguel Hernandez, Elche, Alicante, Spain
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235
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Abstract
Billions of people are infected with respiratory viruses annually. Infants and young children, the elderly, immunocompromised individuals and those debilitated by other diseases or nutritional deficiencies are most at risk for serious disease. There are few vaccines available for use against these viruses, and even where there are (influenza, measles and adenovirus), infections remain common. The continued prevalence of respiratory virus infections has lead to renewed efforts to find safe agents effective against the most medically important respiratory viruses: influenza, respiratory syncytial, parainfluenza, measles, rhino- and adenovirus. Copyright 1999 Harcourt Publishers Ltd.
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Affiliation(s)
- Philip R. Wyde
- Department of Microbiology, Immunology, Baylor College of Medicine, Houston, TX, USA
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236
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Singh M, Berger B, Kim PS. LearnCoil-VMF: computational evidence for coiled-coil-like motifs in many viral membrane-fusion proteins. J Mol Biol 1999; 290:1031-41. [PMID: 10438601 PMCID: PMC7125536 DOI: 10.1006/jmbi.1999.2796] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Crystallographic studies have shown that the coiled-coil motif occurs in several viral membrane-fusion proteins, including HIV-1 gp41 and influenza virus hemagglutinin. Here, the LearnCoil-VMF program was designed as a specialized program for identifying coiled-coil-like regions in viral membrane-fusion proteins. Based upon the use of LearnCoil-VMF, as well as other computational tools, we report detailed sequence analyses of coiled-coil-like regions in retrovirus, paramyxovirus and filovirus membrane-fusion proteins. Additionally, sequence analyses of these proteins outside their putative coiled-coil domains illustrate some structural differences between them. Complementing previous crystallographic studies, the coiled-coil-like regions detected by LearnCoil-VMF provide further evidence that the three-stranded coiled coil is a common motif found in many diverse viral membrane-fusion proteins. The abundance and structural conservation of this motif, even in the absence of sequence homology, suggests that it is critical for viral-cellular membrane fusion. The LearnCoil-VMF program is available at http://web.wi.mit.edu/kim
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Affiliation(s)
- Mona Singh
- Howard Hughes Medical Institute and the Whitehead Institute for Biomedical Research, 9 Cambridge Center Cambridge, MA 02142, USA Department of Biology Massachusetts Institute of Technology, Cambridge MA 02139, USA
| | - Bonnie Berger
- Department of Mathematics and Laboratory of Computer Science, Massachusetts Institute of Technology, Cambridge MA 02139, USA
| | - Peter S Kim
- Howard Hughes Medical Institute and the Whitehead Institute for Biomedical Research, 9 Cambridge Center Cambridge, MA 02142, USA Department of Biology Massachusetts Institute of Technology, Cambridge MA 02139, USA
- Corresponding author
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237
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Young JK, Li D, Abramowitz MC, Morrison TG. Interaction of peptides with sequences from the Newcastle disease virus fusion protein heptad repeat regions. J Virol 1999; 73:5945-56. [PMID: 10364347 PMCID: PMC112656 DOI: 10.1128/jvi.73.7.5945-5956.1999] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Typical of many viral fusion proteins, the sequence of the Newcastle disease virus (NDV) fusion protein has several heptad repeat regions. One, HR1, is located just carboxyl terminal to the fusion peptide, while the other, HR2, is located adjacent to the transmembrane domain. The structure and function of a synthetic peptide with a sequence from the region of the NDV HR1 region (amino acids 150 to 173) were characterized. The peptide inhibited fusion with a half-maximal concentration of approximately 2 microM; however, inhibition was observed only if the peptide was added prior to protease activation of the fusion protein. This inhibition was virus specific since the peptide had minimal effect on fusion directed by the Sendai virus glycoproteins. To explore the mechanism of action, the potential HR1 peptide interaction with a previously characterized fusion inhibitory peptide with a sequence from the HR2 domain (J. K. Young, R. P. Hicks, G. E. Wright, and T. G. Morrison, Virology 238:291-304, 1997) was characterized. The results demonstrated an interaction between the two peptides both functionally and directly. First, while the individual peptides each inhibit fusion, equimolar mixtures of the two peptides had minimal effect on fusion, suggesting that the two peptides form a complex preventing their interaction with a target protein. Second, an HR2 peptide covalently linked with biotin was found to bind specifically to HR1 peptide in a Western blot. The structure of the HR1 peptide was analyzed by nuclear magnetic resonance spectroscopy and found to be an alpha helix.
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Affiliation(s)
- J K Young
- Department of Chemistry, Colgate University, Hamilton, New York, USA
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238
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Kaiser L, Couch RB, Galasso GJ, Glezen WP, Webster RG, Wright PF, Hayden FG. First International Symposium on Influenza and Other Respiratory Viruses: summary and overview: Kapalua, Maui, Hawaii, December 4-6, 1998. Antiviral Res 1999; 42:149-75. [PMID: 10443529 PMCID: PMC7134157 DOI: 10.1016/s0166-3542(99)00034-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/1999] [Accepted: 04/13/1999] [Indexed: 11/29/2022]
Affiliation(s)
- L Kaiser
- Division of Epidemiology and Virology, University of Virginia School of Medicine, Charlottesville 22908, USA.
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239
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Moulard M, Mabrouk K, Martin I, Van Rietschoten J, Rochat H, Sabatier JM. V3 loop-derived peptide SPC3 inhibits infection of CD4- and galactosylceramide- cells by LAV-2/B. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1999; 53:647-55. [PMID: 10408339 DOI: 10.1034/j.1399-3011.1999.00062.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
SPC3, a synthetic multibranched peptide including the GPGRAF consensus motif of the human immunodeficiency virus type 1 (HIV-1) gp120 V3-loop is a potent inhibitor of HIV infection of human CD4+ lymphocytes, macrophages and CD4-/galactosylceramide+ human colon epithelial cells and is currently tested in phase II clinical trials (FDA protocol 257 A). The antiviral property of SPC3 was further investigated for its ability to inhibit LAV-2/B, an HIV-2 clone with a CD4-independent tropism. SPC3 inhibited the LAV-2/B-mediated infection of B-cell line which does not express the CD4 and the galactosylceramide molecules on their cell surface, suggesting an SPC3-sensitive CD4/galactosylceramide-independent pathway of viral infection in HIV susceptible cells. The molecular mechanism of the peptide inhibition was also investigated. The data suggested that the SPC3-mediated inhibition does not result from a direct competition between SPC3 and gp120 binding to the cell surface of the target cell.
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Affiliation(s)
- M Moulard
- Centre d'Immunologie de Marseille Luminy, France.
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240
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Stone-Hulslander J, Morrison TG. Mutational analysis of heptad repeats in the membrane-proximal region of Newcastle disease virus HN protein. J Virol 1999; 73:3630-7. [PMID: 10196255 PMCID: PMC104138 DOI: 10.1128/jvi.73.5.3630-3637.1999] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
For most paramyxoviruses, syncytium formation requires the expression of both surface glycoproteins (HN and F) in the same cell, and evidence suggests that fusion involves a specific interaction between the HN and F proteins (X. Hu et al., J. Virol. 66:1528-1534, 1992). The stalk region of the Newcastle disease virus (NDV) HN protein has been implicated in both fusion promotion and virus specificity of that activity. The NDV F protein contains two heptad repeat motifs which have been shown by site-directed mutagenesis to be critical for fusion (R. Buckland et al., J. Gen. Virol. 73:1703-1707, 1992; T. Sergel-Germano et al., J. Virol. 68:7654-7658, 1994; J. Reitter et al., J. Virol. 69:5995-6004, 1995). Heptad repeat motifs mediate protein-protein interactions by enabling the formation of coiled coils. Upon analysis of the stalk region of the NDV HN protein, we identified two heptad repeats. Secondary structure analysis of these repeats suggested the potential for these regions to form alpha helices. To investigate the importance of this sequence motif for fusion promotion, we mutated the hydrophobic a-position amino acids of each heptad repeat to alanine or methionine. In addition, hydrophobic amino acids in other positions were also changed to alanine. Every mutant protein retained levels of attachment activity that was greater than or equal to the wild-type protein activity and bound to conformation-specific monoclonal as well as polyclonal antisera. Neuraminidase activity was variably affected. Every mutation, however, showed a dramatic decrease in fusion promotion activity. The phenotypes of these mutant proteins indicate that individual amino acids within the heptad repeat region of the stalk domain of the HN protein are important for the fusion promotion activity of the protein. These data are consistent with the idea that the HN protein associates with the F protein via specific interactions between the heptad repeat regions of both proteins.
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Affiliation(s)
- J Stone-Hulslander
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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241
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Domachowske JB, Rosenberg HF. Respiratory syncytial virus infection: immune response, immunopathogenesis, and treatment. Clin Microbiol Rev 1999; 12:298-309. [PMID: 10194461 PMCID: PMC88919 DOI: 10.1128/cmr.12.2.298] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Respiratory syncytial virus (RSV) is the single most important cause of lower respiratory tract infection during infancy and early childhood. Once RSV infection is established, the host immune response includes the production of virus-neutralizing antibodies and T-cell-specific immunity. The humoral immune response normally results in the development of anti-RSV neutralizing-antibody titers, but these are often suboptimal during an infant's initial infection. Even when the production of RSV neutralizing antibody following RSV infection is robust, humoral immunity wanes over time. Reinfection during subsequent seasons is common. The cellular immune response to RSV infection is also important for the clearance of virus. This immune response, vital for host defense against RSV, is also implicated in the immunopathogenesis of severe lower respiratory tract RSV bronchiolitis. Many details of the immunology and immunopathologic mechanisms of RSV disease known at present have been learned from rodent models of RSV disease and are discussed in some detail. In addition, the roles of immunoglobulin E, histamine, and eosinophils in the immunopathogenesis of RSV disease are considered. Although the treatment of RSV bronchiolitis is primarily supportive, the role of ribavirin is briefly discussed. Novel approaches to the development of new antiviral drugs with promising anti-RSV activity in vitro are also described.
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Affiliation(s)
- J B Domachowske
- State University of New York Health Science Center at Syracuse, Syracuse, New York 13210,
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242
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Malashkevich VN, Schneider BJ, McNally ML, Milhollen MA, Pang JX, Kim PS. Core structure of the envelope glycoprotein GP2 from Ebola virus at 1.9-A resolution. Proc Natl Acad Sci U S A 1999; 96:2662-7. [PMID: 10077567 PMCID: PMC15825 DOI: 10.1073/pnas.96.6.2662] [Citation(s) in RCA: 209] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ebola virions contain a surface transmembrane glycoprotein (GP) that is responsible for binding to target cells and subsequent fusion of the viral and host-cell membranes. GP is expressed as a single-chain precursor that is posttranslationally processed into the disulfide-linked fragments GP1 and GP2. The GP2 subunit is thought to mediate membrane fusion. A soluble fragment of the GP2 ectodomain, lacking the fusion-peptide region and the transmembrane helix, folds into a stable, highly helical structure in aqueous solution. Limited proteolysis studies identify a stable core of the GP2 ectodomain. This 74-residue core, denoted Ebo-74, was crystallized, and its x-ray structure was determined at 1.9-A resolution. Ebo-74 forms a trimer in which a long, central three-stranded coiled coil is surrounded by shorter C-terminal helices that are packed in an antiparallel orientation into hydrophobic grooves on the surface of the coiled coil. Our results confirm the previously anticipated structural similarity between the Ebola GP2 ectodomain and the core of the transmembrane subunit from oncogenic retroviruses. The Ebo-74 structure likely represents the fusion-active conformation of the protein, and its overall architecture resembles several other viral membrane-fusion proteins, including those from HIV and influenza.
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Affiliation(s)
- V N Malashkevich
- Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA
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243
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Ben-Efraim I, Kliger Y, Hermesh C, Shai Y. Membrane-induced step in the activation of Sendai virus fusion protein. J Mol Biol 1999; 285:609-25. [PMID: 9878433 DOI: 10.1006/jmbi.1998.2370] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peptides derived from conserved heptad-repeat regions of several viruses have been shown recently to inhibit virus-cell fusion. To find out their possible role in the fusion process, two biologically active heptad-repeat segments of the fusion protein (F) of Sendai virus, SV-150 (residues 150-186), and SV-473 (residues 473-495) were synthesized, fluorescently labeled and spectroscopically characterized for their structure and organization in solution and within the membrane. SV-150 was found to be 50-fold less active than SV-473 in inhibiting Sendai virus-cell fusion. Circular dichroism (CD) spectroscopy revealed that in aqueous solution, the peptides are self-associated and adopt low alpha-helical structure. However, when the two peptides are mixed together, their alpha-helical content significantly increases. Fluorescence studies, CD, and polarized attenuated total reflection infrared (ATR-FTIR) spectroscopy showed that both peptides, alone or as a complex, bind strongly to negatively charged and zwitterionic phospholipid membranes, dissociate therein into alpha-helical monomers, but do not perturb the lipid packing of the membrane. The ability of the peptides to interact with each other in solution may be correlated with antiviral activity, whereas their ability to interact with the membrane, together with their location near the fusion peptide and the transmembrane domain, suggests a revision to the currently accepted model for viral-induced membrane fusion. In the revised model, in the sequence of events associated with viral entry, the two heptad-repeat sequences may assist in bringing the viral and cellular membranes closer, thus facilitating membrane fusion.
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Affiliation(s)
- I Ben-Efraim
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100, Israel
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244
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Lamb RA, Joshi SB, Dutch RE. The paramyxovirus fusion protein forms an extremely stable core trimer: structural parallels to influenza virus haemagglutinin and HIV-1 gp41. Mol Membr Biol 1999; 16:11-9. [PMID: 10332733 DOI: 10.1080/096876899294715] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The paramyxovirus fusion (F) protein mediates membrane fusion. The biologically active F protein consists of a membrane distal subunit F2 and a membrane anchored subunit F1. A highly stable structure has been identified comprised of peptides derived from the simian virus 5 (SV5) F1 heptad repeat A, which abuts the hydrophobic fusion peptide (peptide N-1), and the SV5 F1 heptad repeat B, located 270 residues downstream and adjacent to the transmembrane domain (peptides C-1 and C-2). In isolation, peptide N-1 is 47% alpha-helical and peptide C-1 and C-2 are unfolded. When mixed together, peptides N1 + C1 form a thermostable (Tm > 90 degrees C), 82% alpha-helical, discrete trimer of heterodimers (mass 31,300 M(r)) that is resistant to denaturation by 2% SDS at 40 degrees C. The authors suggest that this alpha-helical trimeric complex represents the core most stable form of the F protein that is either fusion competent or forms after fusion has occurred. Peptide C-1 is a potent inhibitor of both the lipid mixing and aqueous content mixing fusion activity of the SV5 F protein. In contrast, peptide N-1 inhibits cytoplasmic content mixing but not lipid mixing, leading to a stable hemifusion state. Thus, these peptides define functionally different steps in the fusion process. The parallels among both the fusion processes and the protein structures of paramyxovirus F proteins, HIV gp41 and influenza virus haemagglutinin are discussed, as the analogies are indicative of a conserved paradigm for fusion promotion among fusion proteins from widely disparate viruses.
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Affiliation(s)
- R A Lamb
- Howard Hughes Medical Institute, Northwestern University, Evanston, IL 60208-3500, USA
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245
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Chan DC, Chutkowski CT, Kim PS. Evidence that a prominent cavity in the coiled coil of HIV type 1 gp41 is an attractive drug target. Proc Natl Acad Sci U S A 1998; 95:15613-7. [PMID: 9861018 PMCID: PMC28092 DOI: 10.1073/pnas.95.26.15613] [Citation(s) in RCA: 410] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synthetic C peptides, corresponding to the C helix of the HIV type 1 (HIV-1) gp41 envelope protein, are potent inhibitors of HIV-1 membrane fusion. One such peptide is in clinical trials. The crystal structure of the gp41 core, in its proposed fusion-active conformation, is a trimer of helical hairpins in which three C helices pack against a central coiled coil. Each C helix shows especially prominent contacts with one of three symmetry-related, hydrophobic cavities on the surface of the coiled coil. We show that the inhibitory activity of the C peptide C34 depends on its ability to bind to this coiled-coil cavity. Moreover, examining a series of C34 peptide variants with modified cavity-binding residues, we find a linear relationship between the logarithm of the inhibitory potency and the stability of the corresponding helical-hairpin complexes. Our results provide strong evidence that this coiled-coil cavity is a good drug target and clarify the mechanism of C peptide inhibition. They also suggest simple, quantitative assays for the identification and evaluation of analogous inhibitors of HIV-1 entry.
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Affiliation(s)
- D C Chan
- Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA
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246
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Ghosh JK, Peisajovich SG, Ovadia M, Shai Y. Structure-function study of a heptad repeat positioned near the transmembrane domain of Sendai virus fusion protein which blocks virus-cell fusion. J Biol Chem 1998; 273:27182-90. [PMID: 9765238 DOI: 10.1074/jbc.273.42.27182] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A synthetic heptad repeat, SV-473, derived from Sendai virus fusion protein is a potent inhibitor of virus-cell fusion. In order to understand the mechanism of the inhibitory effect, we synthesized and fluorescently labeled SV-465, an extended version of SV-473 by one more heptad, its mutant peptide A17,24-SV-465, in which two heptadic leucines were substituted with two alanines, and its enatiomer D-SV-465, composed entirely of Damino acids. Similar mutations in the homologous fusion protein of the Newcastle disease virus drastically reduced its activity. The data revealed that SV-465, but not A17,24-SV-465 or its enantiomer, is highly active in inhibiting Sendai virus-induced hemolysis of red blood cells. None of the peptides interfere with the binding of virions to the target red blood cells as demonstrated by hemagglutinin assay. Fluorescence and circular dichroism (CD) spectroscopy indicated that: (i) only SV-465 could self-assemble in aqueous environment; (ii) only SV-465 could co-assemble with two other biologically active heptad repeats derived from Sendai virus fusion protein; (iii) SV-465 has a higher helical content than A17,24-SV-465 in solution, and (iv) all the peptides bind strongly to zwitterionic and negatively charged phospholipids. Polarized attenuated total reflection infrared spectroscopy revealed that they bound as monomers onto the surface of zwitterionic membranes with predominantly alpha-helical structures. The functional role of the amino acid 465-497 domain in Sendai virus-mediated membrane fusion is discussed in light of these findings.
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Affiliation(s)
- J K Ghosh
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100 Israel
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247
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Joshi SB, Dutch RE, Lamb RA. A core trimer of the paramyxovirus fusion protein: parallels to influenza virus hemagglutinin and HIV-1 gp41. Virology 1998; 248:20-34. [PMID: 9705252 DOI: 10.1006/viro.1998.9242] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The paramyxovirus fusion (F) protein mediates membrane fusion. The biologically active F protein consists of a membrane distal subunit, F2, and a membrane-anchored subunit, F1. We have identified a highly stable structure composed of peptides derived from the F1 heptad repeat A, which abuts the hydrophobic fusion peptide (peptide N-1), and the F1 heptad repeat B, located 270 residues downstream and adjacent to the transmembrane domain (peptides C-1 and C-2). In isolation, peptide N-1 is 47% alpha-helical and peptide C-1 and C-2 are unfolded. When mixed together, peptides N1 + C1 form a thermostable (Tm >90 degreesC), 82% alpha-helical, discrete trimer of heterodimers (mass 31,300 Mr) that is resistant to denaturation by 2% SDS at 40 degreesC. We suggest that this alpha-helical trimeric complex represents the core most stable form of the F protein that either is fusion competent or forms after fusion has occurred. Peptide C-1 is a potent inhibitor of both the lipid mixing and the aqueous content mixing fusion activity of the SV5 F protein. In contrast, peptides N-1 and N-2 inhibit cytoplasmic content mixing but not lipid mixing, leading to a stable hemifusion state. Thus, these peptides define functionally different steps in the fusion process. The parallels among both the fusion processes and the protein structures of paramyxovirus F proteins, HIV gp41, and influenza virus hemagglutinin are discussed, as the analogies are indicative of a conserved paradigm for fusion promotion among fusion proteins from widely disparate viruses.
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Affiliation(s)
- S B Joshi
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, 60208-3500, USA
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248
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Qiao H, Pelletier SL, Hoffman L, Hacker J, Armstrong RT, White JM. Specific single or double proline substitutions in the "spring-loaded" coiled-coil region of the influenza hemagglutinin impair or abolish membrane fusion activity. J Cell Biol 1998; 141:1335-47. [PMID: 9628890 PMCID: PMC2132786 DOI: 10.1083/jcb.141.6.1335] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/1997] [Revised: 04/10/1998] [Indexed: 02/07/2023] Open
Abstract
We tested the role of the "spring-loaded" conformational change in the fusion mechanism of the influenza hemagglutinin (HA) by assessing the effects of 10 point mutants in the region of high coiled-coil propensity, HA2 54-81. The mutants included proline substitutions at HA2 55, 71, and 80, as well as a double proline substitution at residues 55 and 71. Mutants were expressed in COS or 293T cells and assayed for cell surface expression and structural features as well as for their ability to change conformation and induce fusion at low pH. We found the following: Specific mutations affected the precise carbohydrate structure and folding of the HA trimer. All of the mutants, however, formed trimers that could be expressed at the cell surface in a form that could be proteolytically cleaved from the precursor, HA0, to the fusion-permissive form, HA1-S-S-HA2. All mutants reacted with an antibody against the major antigenic site and bound red blood cells. Seven out of ten mutants displayed a wild-type (wt) or moderately elevated pH dependence for the conformational change. V55P displayed a substantial reduction (approximately 60- 80%) in the initial rate of lipid mixing. The other single mutants displayed efficient fusion with the same pH dependence as wt-HA. The double proline mutant V55P/ S71P displayed no fusion activity despite being well expressed at the cell surface as a proteolytically cleaved trimer that could bind red blood cells and change conformation at low pH. The impairment in fusion for both V55P and V55P/S71P was at the level of outer leaflet lipid mixing. We interpret our results in support of the hypothesis that the spring-loaded conformational change is required for fusion. An alternate model is discussed.
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Affiliation(s)
- H Qiao
- Department of Cell Biology, University of Virginia, Health Sciences Center, Charlottesville, Virginia 22908, USA
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249
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Lawless MK, Hopkins S, Anwer MK. Quantitation of a 36-amino-acid peptide inhibitor of HIV-1 membrane fusion in animal and human plasma using high-performance liquid chromatography and fluorescence detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1998; 707:213-7. [PMID: 9613952 DOI: 10.1016/s0378-4347(97)00609-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Selective extraction of a 36-amino-acid peptide (DP-178, T20, pentafuside) from the protein matrices of animal and human plasma was achieved using acetonitrile containing 1% trifluoroacetic acid and 1% n-nonyl-beta-D-glucopyranoside. The peptide concentration of the extract was measured using reversed-phase high-performance liquid chromatography (RP-HPLC) and fluorescence detection. The eluent was excited at 280 nm and the intrinsic fluorescence signal was collected at 350 nm. Recovery of T20 from the plasma matrices was 75% (mouse), 60% (rat), 50% (cynomolgus monkey), and 55% (human) based on parallel-processed aqueous T20 standard solutions. The fluorescence peak area vs. concentration of T20 was linear in the range 4-160 ng/ml based on the final solute concentration in the HPLC vial, corresponding to original plasma concentrations of 100-4000 ng/ml. Experiments with truncated analogs of T20 demonstrate that this assay offers the advantage of detecting metabolites attributable to bio-transformation degradation processes differing by as little as one amino acid from the original peptide.
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250
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Furuta RA, Wild CT, Weng Y, Weiss CD. Capture of an early fusion-active conformation of HIV-1 gp41. NATURE STRUCTURAL BIOLOGY 1998; 5:276-9. [PMID: 9546217 DOI: 10.1038/nsb0498-276] [Citation(s) in RCA: 426] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Using an inhibitory synthetic peptide (DP-178) from HIV-1 gp41, we have trapped HIV-1 envelope glycoprotein (Env) undergoing conformational changes during virus entry. Our data show that DP-178 binds gp41 and inhibits Env-mediated membrane fusion after gp120 interacts with cellular receptors, indicating that conformational changes involving the coiled coil domain of gp41 are required for entry. Capture of this fusion-active conformation of Env provides insights into the early events leading to Env-mediated membrane fusion.
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Affiliation(s)
- R A Furuta
- Office of Vaccines, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892-4555, USA
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