1
|
Dufloo J, Sanjuán R. Temperature impacts SARS-CoV-2 spike fusogenicity and evolution. mBio 2024; 15:e0336023. [PMID: 38411986 PMCID: PMC11005339 DOI: 10.1128/mbio.03360-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 01/29/2024] [Indexed: 02/28/2024] Open
Abstract
SARS-CoV-2 infects both the upper and lower respiratory tracts, which are characterized by different temperatures (33°C and 37°C, respectively). In addition, fever is a common COVID-19 symptom. SARS-CoV-2 has been shown to replicate more efficiently at low temperatures, but the effect of temperature on different viral proteins remains poorly understood. Here, we investigate how temperature affects the SARS-CoV-2 spike function and evolution. We first observed that increasing temperature from 33°C to 37°C or 39°C increased spike-mediated cell-cell fusion. We then experimentally evolved a recombinant vesicular stomatitis virus expressing the SARS-CoV-2 spike at these different temperatures. We found that spike-mediated cell-cell fusion was maintained during evolution at 39°C but was lost in a high proportion of viruses that evolved at 33°C or 37°C. Consistently, sequencing of the spikes evolved at 33°C or 37°C revealed the accumulation of mutations around the furin cleavage site, a region that determines cell-cell fusion, whereas this did not occur in spikes evolved at 39°C. Finally, using site-directed mutagenesis, we found that disruption of the furin cleavage site had a temperature-dependent effect on spike-induced cell-cell fusion and viral fitness. Our results suggest that variations in body temperature may affect the activity and diversification of the SARS-CoV-2 spike. IMPORTANCE When it infects humans, SARS-CoV-2 is exposed to different temperatures (e.g., replication site and fever). Temperature has been shown to strongly impact SARS-CoV-2 replication, but how it affects the activity and evolution of the spike protein remains poorly understood. Here, we first show that high temperatures increase the SARS-CoV-2 spike fusogenicity. Then, we demonstrate that the evolution of the spike activity and variants depends on temperature. Finally, we show that the functional effect of specific spike mutations is temperature-dependent. Overall, our results suggest that temperature may be a factor influencing the activity and adaptation of the SARS-CoV-2 spike in vivo, which will help understanding viral tropism, pathogenesis, and evolution.
Collapse
Affiliation(s)
- Jérémy Dufloo
- Institute for Integrative Systems Biology, Consejo Superior de Investigaciones Científicas-Universitat de València, Paterna, València, Spain
| | - Rafael Sanjuán
- Institute for Integrative Systems Biology, Consejo Superior de Investigaciones Científicas-Universitat de València, Paterna, València, Spain
| |
Collapse
|
2
|
Kordyukova L. Structural and functional specificity of Influenza virus haemagglutinin and paramyxovirus fusion protein anchoring peptides. Virus Res 2017; 227:183-199. [DOI: 10.1016/j.virusres.2016.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 09/21/2016] [Accepted: 09/23/2016] [Indexed: 02/08/2023]
|
3
|
Abstract
The family Paramyxoviridae includes many viruses that significantly affect human and animal health. An essential step in the paramyxovirus life cycle is viral entry into host cells, mediated by virus-cell membrane fusion. Upon viral entry, infection results in expression of the paramyxoviral glycoproteins on the infected cell surface. This can lead to cell-cell fusion (syncytia formation), often linked to pathogenesis. Thus membrane fusion is essential for both viral entry and cell-cell fusion and an attractive target for therapeutic development. While there are important differences between viral-cell and cell-cell membrane fusion, many aspects are conserved. The paramyxoviruses generally utilize two envelope glycoproteins to orchestrate membrane fusion. Here, we discuss the roles of these glycoproteins in distinct steps of the membrane fusion process. These findings can offer insights into evolutionary relationships among Paramyxoviridae genera and offer future targets for prophylactic and therapeutic development.
Collapse
|
4
|
Trypsin- and low pH-mediated fusogenicity of avian metapneumovirus fusion proteins is determined by residues at positions 100, 101 and 294. Sci Rep 2015; 5:15584. [PMID: 26498473 PMCID: PMC4620442 DOI: 10.1038/srep15584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/29/2015] [Indexed: 12/03/2022] Open
Abstract
Avian metapneumovirus (aMPV) and human metapneumovirus (hMPV) are members of the genus Metapneumovirus in the subfamily Pneumovirinae. Metapneumovirus fusion (F) protein mediates the fusion of host cells with the virus membrane for infection. Trypsin- and/or low pH-induced membrane fusion is a strain-dependent phenomenon for hMPV. Here, we demonstrated that three subtypes of aMPV (aMPV/A, aMPV/B, and aMPV/C) F proteins promoted cell-cell fusion in the absence of trypsin. Indeed, in the presence of trypsin, only aMPV/C F protein fusogenicity was enhanced. Mutagenesis of the amino acids at position 100 and/or 101, located at a putative cleavage region in aMPV F proteins, revealed that the trypsin-mediated fusogenicity of aMPV F proteins is regulated by the residues at positions 100 and 101. Moreover, we demonstrated that aMPV/A and aMPV/B F proteins mediated cell-cell fusion independent of low pH, whereas the aMPV/C F protein did not. Mutagenesis of the residue at position 294 in the aMPV/A, aMPV/B, and aMPV/C F proteins showed that 294G played a critical role in F protein-mediated fusion under low pH conditions. These findings on aMPV F protein-induced cell-cell fusion provide new insights into the molecular mechanisms underlying membrane fusion and pathogenesis of aMPV.
Collapse
|
5
|
Yunus AS, Jackson TP, Crisafi K, Burimski I, Kilgore NR, Zoumplis D, Allaway GP, Wild CT, Salzwedel K. Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation. Virology 2009; 396:226-37. [PMID: 19922971 DOI: 10.1016/j.virol.2009.10.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 08/11/2009] [Accepted: 10/26/2009] [Indexed: 10/20/2022]
Abstract
Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 degrees C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of RSV F-mediated membrane fusion and have important implications for the identification of therapeutic strategies and vaccines targeting RSV F protein conformational changes.
Collapse
Affiliation(s)
- Abdul S Yunus
- Panacos Pharmaceuticals, Inc., 209 Perry Parkway, Suite 7, Gaithersburg, MD 20877, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Sarmiento R, Arias C, Méndez E, Gómez B. Characterization of a persistent respiratory syncytial virus showing a low-fusogenic activity associated to an impaired F protein. Virus Res 2009; 139:39-47. [DOI: 10.1016/j.virusres.2008.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/06/2008] [Accepted: 10/08/2008] [Indexed: 10/21/2022]
|
7
|
Low-pH triggering of human metapneumovirus fusion: essential residues and importance in entry. J Virol 2008; 83:1511-22. [PMID: 19036821 DOI: 10.1128/jvi.01381-08] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human metapneumovirus (HMPV) is a significant respiratory pathogen classified in the Pneumovirinae subfamily of the paramyxovirus family. Recently, we demonstrated that HMPV F protein-promoted cell-cell fusion is stimulated by exposure to low pH, in contrast to what is observed for other paramyxovirus F proteins. In the present study, we examined the potential role of histidine protonation in HMPV F fusion and investigated the role of low pH in HMPV viral entry. Mutagenesis of the three ectodomain histidine residues of the HMPV F protein demonstrated that the mutation of a histidine in the heptad repeat B linker domain (H435) ablated fusion activity without altering cell surface expression or proteolytic processing significantly. Modeling of the HMPV F protein revealed several basic residues surrounding this histidine residue, and the mutation of these residues also reduced fusion activity. These results suggest that electrostatic repulsion in the heptad repeat B linker region may contribute to the triggering of HMPV F. In addition, we examined the effect of inhibitors of endosomal acidification or endocytosis on the entry of a recombinant green fluorescent protein-expressing HMPV. Interestingly, chemicals that raise the pH of endocytic vesicles resulted in a 30 to 50% decrease in HMPV infection, while the inhibitors of endocytosis reduced infection by as much as 90%. These data suggest that HMPV utilizes an endocytic entry mechanism, in contrast to what has been hypothesized for most paramyxoviruses. In addition, our results indicate that HMPV uses the low pH of the endocytic pathway to enhance infectivity, though the role of low pH likely differs from classically described mechanisms.
Collapse
|
8
|
White JM, Delos SE, Brecher M, Schornberg K. Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit Rev Biochem Mol Biol 2008; 43:189-219. [PMID: 18568847 DOI: 10.1080/10409230802058320] [Citation(s) in RCA: 664] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Recent work has identified three distinct classes of viral membrane fusion proteins based on structural criteria. In addition, there are at least four distinct mechanisms by which viral fusion proteins can be triggered to undergo fusion-inducing conformational changes. Viral fusion proteins also contain different types of fusion peptides and vary in their reliance on accessory proteins. These differing features combine to yield a rich diversity of fusion proteins. Yet despite this staggering diversity, all characterized viral fusion proteins convert from a fusion-competent state (dimers or trimers, depending on the class) to a membrane-embedded homotrimeric prehairpin, and then to a trimer-of-hairpins that brings the fusion peptide, attached to the target membrane, and the transmembrane domain, attached to the viral membrane, into close proximity thereby facilitating the union of viral and target membranes. During these conformational conversions, the fusion proteins induce membranes to progress through stages of close apposition, hemifusion, and then the formation of small, and finally large, fusion pores. Clearly, highly divergent proteins have converged on the same overall strategy to mediate fusion, an essential step in the life cycle of every enveloped virus.
Collapse
Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908-0732, USA.
| | | | | | | |
Collapse
|
9
|
Effects of hemagglutinin-neuraminidase protein mutations on cell-cell fusion mediated by human parainfluenza type 2 virus. J Virol 2008; 82:8283-95. [PMID: 18562539 DOI: 10.1128/jvi.00460-08] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The monoclonal antibody M1-1A, specific for the hemagglutinin-neuraminidase (HN) protein of human parainfluenza type 2 virus (HPIV2), blocks virus-induced cell-cell fusion without affecting the hemagglutinating and neuraminidase activities. F13 is a neutralization escape variant selected with M1-1A and contains amino acid mutations N83Y and M186I in the HN protein, with no mutation in the fusion protein. Intriguingly, F13 exhibits reduced ability to induce cell-cell fusion despite its multistep replication. To investigate the potential role of HPIV2 HN protein in the regulation of cell-cell fusion, we introduced these mutations individually or in combination to the HN protein in the context of recombinant HPIV2. Following infection at a low multiplicity, Vero cells infected with the mutant virus H-83/186, which carried both the N83Y and M186I mutations, remained as nonfused single cells at least for 24 h, whereas most of the cells infected with wild-type virus mediated prominent cell-cell fusion within 24 h. On the other hand, the cells infected with the mutant virus, carrying either the H-83 or H-186 mutation, mediated cell-cell fusion but less efficiently than those infected with wild-type virus. Irrespective of the ability to cause cell-cell fusion, however, every virus could infect all the cells in the culture within 48 h after the initial infection. These results indicated that both the N83Y and M186I mutations in the HN protein are involved in the regulation of cell-cell fusion. Notably, the limited cell-cell fusion by H-83/186 virus was greatly promoted by lysophosphatidic acid, a stimulator of the Ras and Rho family GTPases.
Collapse
|
10
|
Cavalcanti A, Shirinzadeh B, Zhang M, Kretly LC. Nanorobot Hardware Architecture for Medical Defense. SENSORS (BASEL, SWITZERLAND) 2008; 8:2932-2958. [PMID: 27879858 PMCID: PMC3675524 DOI: 10.3390/s8052932] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Accepted: 04/29/2008] [Indexed: 12/03/2022]
Abstract
This work presents a new approach with details on the integrated platform and hardware architecture for nanorobots application in epidemic control, which should enable real time in vivo prognosis of biohazard infection. The recent developments in the field of nanoelectronics, with transducers progressively shrinking down to smaller sizes through nanotechnology and carbon nanotubes, are expected to result in innovative biomedical instrumentation possibilities, with new therapies and efficient diagnosis methodologies. The use of integrated systems, smart biosensors, and programmable nanodevices are advancing nanoelectronics, enabling the progressive research and development of molecular machines. It should provide high precision pervasive biomedical monitoring with real time data transmission. The use of nanobioelectronics as embedded systems is the natural pathway towards manufacturing methodology to achieve nanorobot applications out of laboratories sooner as possible. To demonstrate the practical application of medical nanorobotics, a 3D simulation based on clinical data addresses how to integrate communication with nanorobots using RFID, mobile phones, and satellites, applied to long distance ubiquitous surveillance and health monitoring for troops in conflict zones. Therefore, the current model can also be used to prevent and save a population against the case of some targeted epidemic disease.
Collapse
Affiliation(s)
- Adriano Cavalcanti
- CAN Center for Automation in Nanobiotech, Melbourne, VIC 3168 Australia.
- Robotics and Mechatronics Research Lab., Dept. of Mechanical Eng., Monash University, Clayton, Melbourne, VIC 3800 Australia.
| | - Bijan Shirinzadeh
- Robotics and Mechatronics Research Lab., Dept. of Mechanical Eng., Monash University, Clayton, Melbourne, VIC 3800 Australia.
| | - Mingjun Zhang
- Dept. of Mechanical, Aerospace & Biomedical Eng., The University of Tennessee, Knoxville, TN 37996 USA.
| | - Luiz C Kretly
- Dept. of Microwave and Optics, Electrical & Comp. Eng., University of Campinas, Campinas, SP 13083 Brazil.
| |
Collapse
|
11
|
Mohd Jaafar F, Goodwin AE, Belhouchet M, Merry G, Fang Q, Cantaloube JF, Biagini P, de Micco P, Mertens PPC, Attoui H. Complete characterisation of the American grass carp reovirus genome (genus Aquareovirus: family Reoviridae) reveals an evolutionary link between aquareoviruses and coltiviruses. Virology 2008; 373:310-21. [PMID: 18191982 DOI: 10.1016/j.virol.2007.12.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Revised: 11/27/2007] [Accepted: 12/06/2007] [Indexed: 11/18/2022]
Abstract
An aquareovirus was isolated from several fish species in the USA (including healthy golden shiners) that is not closely related to members of species Aquareovirus A, B and C. The virus, which is atypical (does not cause syncytia in cell cultures at neutral pH), was implicated in a winter die-off of grass carp fingerlings and has therefore been called 'American grass carp reovirus' (AGCRV). Complete nucleotide sequence analysis of the AGCRV genome and comparisons to the other aquareoviruses showed that it is closely related to golden ide reovirus (GIRV) (>92% amino acid [aa] identity in VP5(NTPase) and VP2(Pol)). However, comparisons with grass carp reovirus (Aquareovirus C) and chum salmon reovirus (Aquareovirus A) showed only 22% to 76% aa identity in different viral proteins. These findings have formed the basis for the recognition of AGCRV and GIRV as members of a new Aquareovirus species 'Aquareovirus G' by ICTV. Further sequence comparisons to other members of the family Reoviridae suggest that there has been an 'evolutionary jump,' involving a change in the number of genome segments, between the aquareoviruses (11 segments) and coltiviruses (12 segments). Segment 7 of AGRCV encodes two proteins, from two distinct ORFs, which are homologues of two Coltivirus proteins encoded by genome segments 9 and 12. A similar model has previously been reported for the rotaviruses and seadornaviruses.
Collapse
Affiliation(s)
- Fauziah Mohd Jaafar
- Department of Arbovirology, Institute for Animal Health, Pirbright, Woking, Surrey, GU24 0NF, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Palermo LM, Porotto M, Greengard O, Moscona A. Fusion promotion by a paramyxovirus hemagglutinin-neuraminidase protein: pH modulation of receptor avidity of binding sites I and II. J Virol 2007; 81:9152-61. [PMID: 17567695 PMCID: PMC1951465 DOI: 10.1128/jvi.00888-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paramyxoviruses, including the childhood respiratory pathogen human parainfluenza virus type 3 (HPIV3), possess an envelope protein hemagglutinin-neuraminidase (HN) that has receptor-cleaving (neuraminidase), as well as receptor-binding, activity. HN is a type II transmembrane glycoprotein, present on the surface of the virus as a tetramer composed of two dimers. HN is also essential for activating the fusion protein (F) to mediate merger of the viral envelope with the host cell membrane. This initial step of viral entry occurs at the host cell surface at neutral pH. The HN molecule carries out these three different critical activities at specific points in the process of viral entry, and understanding the regulation of these activities is key for the design of strategies that block infection. One bifunctional site (site I) on the HN of HPIV3 possesses both receptor binding and neuraminidase activities, and we recently obtained experimental evidence for a second receptor binding site (site II) on HPIV3 HN. Mutation of HN at specific residues at this site, which is next to the HN dimer interface, confers enhanced fusion properties, without affecting neuraminidase activity or receptor binding at neutral pH. We now demonstrate that mutations at this site II, as well as at site I, confer pH dependence on HN's receptor avidity. These mutations permit pH to modulate the binding and fusion processes of the virus, potentially providing regulation at specific stages of the viral life cycle.
Collapse
Affiliation(s)
- Laura M Palermo
- Department of Pediatrics, Weill Medical College of Cornell University, 515 East 71st St., Box 309, New York, NY 10021, USA
| | | | | | | |
Collapse
|
13
|
Cantín C, Holguera J, Ferreira L, Villar E, Muñoz-Barroso I. Newcastle disease virus may enter cells by caveolae-mediated endocytosis. J Gen Virol 2007; 88:559-569. [PMID: 17251575 DOI: 10.1099/vir.0.82150-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The entry into cells of Newcastle disease virus (NDV), a prototype member of the paramyxoviruses, is believed to occur by direct fusion at the plasma membrane through a pH-independent mechanism. In addition, NDV may enter host cells by an endocytic pathway. Treatment of cells with drugs that block caveolae-dependent endocytosis reduced NDV fusion and infectivity, the degree of inhibition being dependent on virus concentration. The inhibitory effect was reduced greatly when drugs were added after virus adsorption. Cells treated with methyl beta-cyclodextrin, a drug that sequesters cholesterol from membranes, reduced the extent of fusion, infectivity and virus-cell binding; this indicates that cholesterol plays a role in NDV entry. Double-labelling immunofluorescence assays performed with anti-NDV monoclonal antibodies and antibodies against the early endosome marker EEA1 revealed the localization of the virus in these intracellular structures. Using fluorescence microscopy, it was found that cell-cell fusion was enhanced at low pH. It is concluded that NDV may infect cells through a caveolae-dependent endocytic pathway, suggesting that this pathway could be an alternative route for virus entry into cells.
Collapse
Affiliation(s)
- Celia Cantín
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| | - Javier Holguera
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| | - Laura Ferreira
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| | - Enrique Villar
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| | - Isabel Muñoz-Barroso
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| |
Collapse
|
14
|
Seth S, Skountzou I, Gernert KM, Compans RW. Fusogenic variants of a noncytopathic paramyxovirus. J Virol 2007; 81:4286-97. [PMID: 17287262 PMCID: PMC1866114 DOI: 10.1128/jvi.01623-06] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SER virus is a type 5 parainfluenza virus that does not exhibit syncytium formation, in contrast to most other paramyxoviruses. This property has been attributed, at least in part, to the presence of an extension of the cytoplasmic tail (CT) of the SER F protein, as truncations or mutations of this region resulted in enhanced fusion. In this study we used repeated passage to select for mutant SER viruses, which were found to be fusogenic. The mutant viruses replicated at levels comparable to or higher than the wild-type SER virus and caused plaque formation, in contrast to the wild-type virus which does not form plaques. The mutants differed strikingly in their plaque sizes. The F genes of mutant viruses were cloned and sequenced and shared some mutations, including a proline-to-leucine change at position 22 and an isoleucine-to-leucine substitution at position 191; other changes that were specific to each mutant were also found. The HN proteins of mutant viruses also showed mutations spanning the length of the protein whereas the M protein showed a consistent mutation, threonine to isoleucine, at position 129. The structure of the F protein was used to identify residues involved in the mutant phenotypes in terms of their location and proximity to heptad repeat domains.
Collapse
Affiliation(s)
- Shaguna Seth
- Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA
| | | | | | | |
Collapse
|
15
|
Schowalter RM, Smith SE, Dutch RE. Characterization of human metapneumovirus F protein-promoted membrane fusion: critical roles for proteolytic processing and low pH. J Virol 2006; 80:10931-41. [PMID: 16971452 PMCID: PMC1642150 DOI: 10.1128/jvi.01287-06] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human metapneumovirus (HMPV) is a recently described human pathogen of the pneumovirus subfamily within the paramyxovirus family. HMPV infection is prevalent worldwide and is associated with severe respiratory disease, particularly in infants. The HMPV fusion protein (F) amino acid sequence contains features characteristic of other paramyxovirus F proteins, including a putative cleavage site and potential N-linked glycosylation sites. Propagation of HMPV in cell culture requires exogenous trypsin, which cleaves the F protein, and HMPV, like several other pneumoviruses, is infectious in the absence of its attachment protein (G). However, little is known about HMPV F-promoted fusion, since the HMPV glycoproteins have yet to be analyzed separately from the virus. Using syncytium and luciferase reporter gene fusion assays, we determined the basic requirements for HMPV F protein-promoted fusion in transiently transfected cells. Our data indicate that proteolytic cleavage of the F protein is a stringent requirement for fusion and that the HMPV G protein does not significantly enhance fusion. Unexpectedly, we also found that fusion can be detected only when transfected cells are treated with trypsin and exposed to low pH, indicating that this viral fusion protein may function in a manner unique among the paramyxoviruses. We also analyzed the F protein cleavage site and three potential N-linked glycosylation sites by mutagenesis. Mutations in the cleavage site designed to facilitate endogenous cleavage did so with low efficiency, and our data suggest that all three N-glycosylation sites are utilized and that each affects cleavage and fusion to various degrees.
Collapse
Affiliation(s)
- Rachel M Schowalter
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Biomedical Biological Sciences Research Building, 741 South Limestone, Lexington, KY 40536-0509, USA
| | | | | |
Collapse
|
16
|
Oomens AGP, Bevis KP, Wertz GW. The cytoplasmic tail of the human respiratory syncytial virus F protein plays critical roles in cellular localization of the F protein and infectious progeny production. J Virol 2006; 80:10465-77. [PMID: 16928754 PMCID: PMC1641763 DOI: 10.1128/jvi.01439-06] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The importance of the F protein cytoplasmic tail (CT) for replication of human respiratory syncytial virus (HRSV) was examined by monitoring the behavior of viruses expressing F proteins with a modified COOH terminus. The F protein mutant viruses were recovered and amplified under conditions where F protein function was complemented by expression of a heterologous viral envelope protein. The effect of the F protein modifications was then examined in the context of a viral infection in standard cell types (Vero and HEp-2). The F protein modifications consisted of a deletion of the predicted CT or a replacement of the CT with the CT of the vesicular stomatitis virus (VSV) G protein. In addition, engineered HRSVs that lacked all homologous glycoprotein genes (SH, G, and F) and expressed instead either the authentic VSV G protein or a VSV G containing the HRSV F protein CT were examined. We found that deletion or replacement of the F protein CT seriously impaired the production of infectious progeny. Cells infected with viruses bearing CT modifications displayed increased F protein surface expression and increased syncytium formation. The distribution of F protein in the plasma membrane of infected cells was altered, resulting in an F protein that was evenly distributed rather than localized predominantly to virus-induced surface filaments. CT deletion or exchange also abrogated interaction of F protein with Triton-insoluble lipid rafts. Addition of the F protein CT to the VSV G protein, expressed as the only viral glycoprotein in an HRSV genome, had the opposite effects: the number of infectious progeny was higher, the surface distribution was changed from relatively even to localized, and the proportion of VSV G protein associated with lipid rafts was higher. Together, these results show that the HRSV F protein CT plays a critical role in F protein cellular localization and production of infectious virus and suggest that the function provided by the CT is independent of the F protein ectodomain and transmembrane domain and is mediated by F protein-lipid raft interaction.
Collapse
Affiliation(s)
- Antonius G P Oomens
- Department of Pathology, University of Virginia, MR5 Building, P.O. Box 800904, Charlottesville, VA 22908-0904, USA
| | | | | |
Collapse
|
17
|
Li M, Li ZN, Yao Q, Yang C, Steinhauer DA, Compans RW. Murine leukemia virus R Peptide inhibits influenza virus hemagglutinin-induced membrane fusion. J Virol 2006; 80:6106-14. [PMID: 16731949 PMCID: PMC1472558 DOI: 10.1128/jvi.02665-05] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cytoplasmic tail of the murine leukemia virus (MuLV) envelope (Env) protein is known to play an important role in regulating viral fusion activity. Upon removal of the C-terminal 16 amino acids, designated as the R peptide, the fusion activity of the Env protein is activated. To extend our understanding of the inhibitory effect of the R peptide and investigate the specificity of inhibition, we constructed chimeric influenza virus-MuLV hemagglutinin (HA) genes. The influenza virus HA protein is the best-studied membrane fusion model, and we investigated the fusion activities of the chimeric HA proteins. We compared constructs in which the coding sequence for the cytoplasmic tail of the influenza virus HA protein was replaced by that of the wild-type or mutant MuLV Env protein or in which the cytoplasmic tail sequence of the MuLV Env protein was added to the HA cytoplasmic domain. Enzyme-linked immunosorbent assays and Western blot analysis showed that all chimeric HA proteins were effectively expressed on the cell surface and cleaved by trypsin. In BHK21 cells, the wild-type HA protein had a significant ability after trypsin cleavage to induce syncytium formation at pH 5.1; however, neither the chimeric HA protein with the full-length cytoplasmic tail of MuLV Env nor the full-length HA protein followed by the R peptide showed any syncytium formation. When the R peptide was truncated or mutated, the fusion activity was partially recovered in the chimeric HA proteins. A low-pH conformational-change assay showed that similar conformational changes occurred for the wild-type and chimeric HA proteins. All chimeric HA proteins were capable of promoting hemifusion and small fusion pore formation, as shown by a dye redistribution assay. These results indicate that the R peptide of the MuLV Env protein has a sequence-dependent inhibitory effect on influenza virus HA protein-induced membrane fusion and that the inhibitory effect occurs at a late stage in fusion pore enlargement.
Collapse
Affiliation(s)
- Min Li
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | |
Collapse
|
18
|
Bissonnette MLZ, Connolly SA, Young DF, Randall RE, Paterson RG, Lamb RA. Analysis of the pH requirement for membrane fusion of different isolates of the paramyxovirus parainfluenza virus 5. J Virol 2006; 80:3071-7. [PMID: 16501116 PMCID: PMC1395469 DOI: 10.1128/jvi.80.6.3071-3077.2006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paramyxoviruses enter cells by fusing their envelopes with the plasma membrane, a process that occurs at neutral pH. Recently, it has been found that there is an exception to this dogma in that a porcine isolate of the paramyxovirus parainfluenza virus 5 (PIV5), known as SER, requires a low-pH step for fusion (S. Seth, A. Vincent, and R. W. Compans, J. Virol. 77: 6520-6527, 2003). As a low-pH activation mechanism for fusion would greatly facilitate biophysical studies of paramyxovirus-mediated membrane fusion, we have reexamined the triggering of the PIV5 SER fusion protein. Using multiple assays, we could not find a requirement for low-pH triggering of PIV5 SER fusion. The challenge of discovering how the paramyxovirus receptor binding protein (HN, H, or G) activates the metastable fusion protein to cause membrane fusion at neutral pH remains.
Collapse
Affiliation(s)
- Mei Lin Z Bissonnette
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, 2205 Tech Drive, Evanston, Illinois 60208-3500, USA
| | | | | | | | | | | |
Collapse
|
19
|
Tsurudome M. [Viral fusion mechanisms]. Uirusu 2006; 55:207-19. [PMID: 16557006 DOI: 10.2222/jsv.55.207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The majority of viral fusion proteins can be divided into two classes. The influenza hemagglutinin (HA) belongs to the class I fusion proteins and undergoes a series of conformational changes at acidic pH, leading to membrane fusion. The crystal structures of the prefusion and the postfusion forms of HA have been revealed in 1981 and 1994, respectively. On the basis of these structures, a model for the mechanism of membrane fusion mediated by the conformational changes of HA has been proposed. The flavivirus E and alphavirus E1 proteins belong to the class II fusion proteins and mediate membrane fusion at acidic pH. Their prefusion structures are distinct from that of HA. Last year, however, it has become evident that the postfusion structures of these class I and class II fusion proteins are similar. The paramyxovirus F protein belongs to the class I fusion proteins. In contrast to HA, an interaction between F and its homologous attachment protein is required for F to undergo the conformational changes. Since F mediates fusion at neutral pH, the infected cells can fuse with neighboring uninfected cells. The crystal structures of F and the attachment protein HN have recently been clarified, which will facilitate studies of the molecular mechanism of F-mediated membrane fusion.
Collapse
Affiliation(s)
- Masato Tsurudome
- Department of Microbiology, Mie University Graduate School of Medicine, Tsu, Mie, Japan.
| |
Collapse
|
20
|
Barnard RJO, Elleder D, Young JAT. Avian sarcoma and leukosis virus-receptor interactions: from classical genetics to novel insights into virus-cell membrane fusion. Virology 2006; 344:25-9. [PMID: 16364732 DOI: 10.1016/j.virol.2005.09.021] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 09/10/2005] [Indexed: 11/16/2022]
Abstract
For over 40 years, avian sarcoma and leukosis virus (ASLV)-receptor interactions have been employed as a useful model system to study the mechanism of retroviral entry into cells. Pioneering studies on this system focused upon the genetic basis of the differential susceptibilities of different lines of chickens to infection by distinct subgroups of ASLV. These studies led to the definition of three distinct autosomal recessive genes that were predicted to encode cellular receptors for different viral subgroups. They also led to the concept of viral interference, i.e. the mechanism by which infection by one virus can render cells resistant to reinfection by other viruses that use the same cellular receptor. Here, we review the contributions that analyses of the ASLV-receptor system have made in unraveling the mechanisms of retroviral entry into cells and focus on key findings such as identification and characterization of the ASLV receptor genes and the subsequent elucidation of an unprecedented mechanism of virus-cell fusion. Since many of the initial findings on this system were published in the early volumes of Virology, this subject is especially well suited to this special anniversary issue of the journal.
Collapse
Affiliation(s)
- R J O Barnard
- The Infectious Disease Laboratory, The Salk Institute, La Jolla, San Diego, CA 92037-1099, USA
| | | | | |
Collapse
|
21
|
Meulendyke KA, Wurth MA, McCann RO, Dutch RE. Endocytosis plays a critical role in proteolytic processing of the Hendra virus fusion protein. J Virol 2005; 79:12643-9. [PMID: 16188966 PMCID: PMC1235849 DOI: 10.1128/jvi.79.20.12643-12649.2005] [Citation(s) in RCA: 59] [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
The Hendra virus fusion (F) protein is synthesized as a precursor protein, F(0), which is proteolytically processed to the mature form, F(1) + F(2). Unlike the case for the majority of paramyxovirus F proteins, the processing event is furin independent, does not require the addition of exogenous proteases, is not affected by reductions in intracellular Ca(2+), and is strongly affected by conditions that raise the intracellular pH (C. T. Pager, M. A. Wurth, and R. E. Dutch, J. Virol. 78:9154-9163, 2004). The Hendra virus F protein cytoplasmic tail contains a consensus motif for endocytosis, YXXPhi. To analyze the potential role of endocytosis in the processing and membrane fusion promotion of the Hendra virus F protein, mutation of tyrosine 525 to alanine (Hendra virus F Y525A) or phenylalanine (Hendra virus F Y525F) was performed. The rate of endocytosis of Hendra virus F Y525A was significantly reduced compared to that of the wild-type (wt) F protein, confirming the functional importance of the endocytosis motif. An intermediate level of endocytosis was observed for Hendra virus F Y525F. Surprisingly, dramatic reductions in the rate of proteolytic processing were observed for Hendra virus F Y525A, although initial transport to the cell surface was not affected. The levels of surface expression for both Hendra virus F Y525A and Hendra virus F Y525F were higher than that of the wt protein, and these mutants displayed enhanced syncytium formation. These results suggest that endocytosis is critically important for Hendra virus F protein cleavage, representing a new paradigm for proteolytic processing of paramyxovirus F proteins.
Collapse
Affiliation(s)
- Kelly Ann Meulendyke
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, 40536-0509, USA
| | | | | | | |
Collapse
|
22
|
Porotto M, Murrell M, Greengard O, Doctor L, Moscona A. Influence of the human parainfluenza virus 3 attachment protein's neuraminidase activity on its capacity to activate the fusion protein. J Virol 2005; 79:2383-92. [PMID: 15681439 PMCID: PMC546598 DOI: 10.1128/jvi.79.4.2383-2392.2005] [Citation(s) in RCA: 53] [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
In order to examine functions of the hemagglutinin-neuraminidase (HN) protein that quantitatively influence fusion promotion, human parainfluenza virus 3 (HPIV3) variants with alterations in HN were studied. The variant HNs have mutations that affect either receptor binding avidity, neuraminidase activity, or fusion protein (F) activation. Neuraminidase activity was regulated by manipulation of temperature and pH. F activation was assessed by quantitating the irreversible binding of target erythrocytes (RBC) to HN/F-coexpressing cells in the presence of 4-GU-DANA (zanamivir) to release target cells bound only by HN-receptor interactions; the remaining, irreversibly bound target cells are retained via the fusion protein. In cells coexpressing wild-type (wt) or variant HNs with wt F, the fusion promotion capacity of HN was distinguished from target cell binding by measuring changes with time in the amounts of target RBC that were (i) reversibly bound by HN-receptor interaction (released only upon the addition of 4-GU-DANA), (ii) released by HN's neuraminidase, and (iii) irreversibly bound by F-insertion or fusion (F triggered). For wt HN, lowering the pH (to approach the optimum for HPIV3 neuraminidase) decreased F triggering via release of HN from its receptor. An HN variant with increased receptor binding avidity had F-triggering efficiency like that of wt HN at pH 8.0, but this efficiency was not decreased by lowering the pH to 5.7, which suggested that the variant HN's higher receptor binding activity counterbalanced the receptor dissociation promoted by increased neuraminidase activity. To dissect the specific contribution of neuraminidase to triggering, two variant HNs that are triggering-defective due to a mutation in the HN stalk were evaluated. One of these variants has, in addition, a mutation in the globular head that renders it neuraminidase dead, while the HN with the stalk mutation alone has 30% of wt neuraminidase. While the variant without neuraminidase activity triggered F effectively at 37 degrees C irrespective of pH, the variant possessing effective neuraminidase activity completely failed to activate F at pH 5.7 and was capable of only minimal triggering activity even at pH 8.0. These results demonstrate that neuraminidase activity impacts the extent of HPIV3-mediated fusion by releasing HN from contact with receptor. Any particular HN's competence to promote F-mediated fusion depends on the balance between its inherent F-triggering efficacy and its receptor-attachment regulatory functions (binding and receptor cleavage).
Collapse
Affiliation(s)
- Matteo Porotto
- Department of Pediatrics, Mount Sinai School of Medicine, 1 Gustave L. Levy Pl., New York, NY 10029, USA
| | | | | | | | | |
Collapse
|
23
|
Lacy DB, Wigelsworth DJ, Melnyk RA, Harrison SC, Collier RJ. Structure of heptameric protective antigen bound to an anthrax toxin receptor: a role for receptor in pH-dependent pore formation. Proc Natl Acad Sci U S A 2004; 101:13147-51. [PMID: 15326297 PMCID: PMC516539 DOI: 10.1073/pnas.0405405101] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
After binding to cellular receptors and proteolytic activation, the protective antigen component of anthrax toxin forms a heptameric prepore. The prepore later undergoes pH-dependent conversion to a pore, mediating translocation of the edema and lethal factors to the cytosol. We describe structures of the prepore (3.6 A) and a prepore:receptor complex (4.3 A) that reveal the location of pore-forming loops and an unexpected interaction of the receptor with the pore-forming domain. Lower pH is required for prepore-to-pore conversion in the presence of the receptor, indicating that this interaction regulates pH-dependent pore formation. We present an example of a receptor negatively regulating pH-dependent membrane insertion.
Collapse
Affiliation(s)
- D Borden Lacy
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
| | | | | | | | | |
Collapse
|
24
|
Seth S, Goodman AL, Compans RW. Mutations in multiple domains activate paramyxovirus F protein-induced fusion. J Virol 2004; 78:8513-23. [PMID: 15280460 PMCID: PMC479096 DOI: 10.1128/jvi.78.16.8513-8523.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
SER virus, a paramyxovirus that is closely related to simian virus 5 (SV5), is unusual in that it fails to induce syncytium formation. The SER virus F protein has an unusually long cytoplasmic tail (CT), and it was previously observed that truncations or specific mutations of this domain result in enhanced syncytium formation. In addition to the long CT, the SER F protein has nine amino acid differences from the F protein of SV5. We previously observed only a partial suppression of fusion in a chimeric SV5 F protein with a CT derived from SER virus, indicating that these other amino acid differences between the SER and SV5 F proteins also play a role in regulating the fusion phenotype. To examine the effects of individual amino acid differences, we mutated the nine SER residues individually to the respective residues of the SV5 F protein. We found that most of the mutants were expressed well and were transported to the cell surface at levels comparable to that of the wild-type SER F protein. Many of the mutants showed enhanced lipid mixing, calcein transfer, and syncytium formation even in the presence of the long SER F protein CT. Some mutants, such as the I310 M, T438S, M489I, T516V, and N529K mutants, also showed fusion at lower temperatures of 32, 25, and 18 degrees C. The residue Asn529 plays a critical role in the suppression of fusion activity, as the mutation of this residue to lysine caused a marked enhancement of fusion. The effect of the N529K mutation on the enhancement of fusion by a previously described mutant, L539,548A, as well as by chimeric SV5/SER F proteins was also dramatic. These results indicate that activation to a fusogenic conformation is dependent on the interplay of residues in the ectodomain, the transmembrane domain, and the CT domain of paramyxovirus F proteins.
Collapse
Affiliation(s)
- Shaguna Seth
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | | |
Collapse
|
25
|
Matsuyama S, Delos SE, White JM. Sequential roles of receptor binding and low pH in forming prehairpin and hairpin conformations of a retroviral envelope glycoprotein. J Virol 2004; 78:8201-9. [PMID: 15254191 PMCID: PMC446138 DOI: 10.1128/jvi.78.15.8201-8209.2004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 03/23/2004] [Indexed: 11/20/2022] Open
Abstract
A general model has been proposed for the fusion mechanisms of class I viral fusion proteins. According to this model a metastable trimer, anchored in the viral membrane through its transmembrane domain, transits to a trimeric prehairpin intermediate, anchored at its opposite end in the target membrane through its fusion peptide. A subsequent refolding event creates a trimer of hairpins (often termed a six-helix bundle) in which the previously well-separated transmembrane domain and fusion peptide (and their attached membranes) are brought together, thereby driving membrane fusion. While there is ample biochemical and structural information on the trimer-of-hairpins conformation of class I viral fusion proteins, less is known about intermediate states between native metastable trimers and the final trimer of hairpins. In this study we analyzed conformational states of the transmembrane subunit (TM), the fusion subunit, of the Env glycoprotein of the subtype A avian sarcoma and leukosis virus (ASLV-A). By analyzing forms of EnvA TM on mildly denaturing sodium dodecyl sulfate gels we identified five conformational states of EnvA TM. Following interaction of virions with a soluble form of the ASLV-A receptor at 37 degrees C, the metastable form of EnvA TM (which migrates at 37 kDa) transits to a 70-kDa and then to a 150-kDa species. Following subsequent exposure to a low pH (or an elevated temperature or the fusion promoting agent chlorpromazine), an additional set of bands at >150 kDa, and then a final band at 100 kDa, forms. Both an EnvA C-helix peptide (which inhibits virus fusion and infectivity) and the fusion-inhibitory agent lysophosphatidylcholine inhibit the formation of the >150- and 100-kDa bands. Our data are consistent with the 70- and 150-kDa bands representing precursor and fully formed prehairpin conformations of EnvA TM. Our data are also consistent with the >150-kDa bands representing higher-order oligomers of EnvA TM and with the 100-kDa band representing the fully formed six-helix bundle. In addition to resolving fusion-relevant conformational intermediates of EnvA TM, our data are compatible with a model in which the EnvA protein is activated by its receptor (at neutral pH and a temperature greater than or equal to room temperature) to form prehairpin conformations of EnvA TM, and in which subsequent exposure to a low pH is required to stabilize the final six-helix bundle, which drives a later stage of fusion.
Collapse
Affiliation(s)
- Shutoku Matsuyama
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908-0732, USA
| | | | | |
Collapse
|
26
|
Waning DL, Russell CJ, Jardetzky TS, Lamb RA. Activation of a paramyxovirus fusion protein is modulated by inside-out signaling from the cytoplasmic tail. Proc Natl Acad Sci U S A 2004; 101:9217-22. [PMID: 15197264 PMCID: PMC438956 DOI: 10.1073/pnas.0403339101] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Many viruses have evolved fusion-mediating glycoproteins that couple the energy released from irreversible protein refolding to the work of membrane fusion. The viral fusion proteins require a triggering event to undergo a cascade of tightly regulated conformational changes. Different isolates of the paramyxovirus SV5 fusion (F) protein have either a short (20-residue) or long (42-residue) cytoplasmic tail (CT), and a long CT suppresses fusion activity in a sequence-specific manner. Addition of a domain to the F protein CT, which has the propensity to form a three-helix bundle, stabilizes the F protein and increases the energy required for fusion activation. Quantitative cell-cell fusion assays and measurement of ectodomain conformation by monoclonal antibody reactivity indicate that this suppression of fusion by the long CT or addition of a three-helix bundle occurs at a step preceding initial membrane merger. The data suggest that F protein activation involves CT signaling to the ectodomain.
Collapse
Affiliation(s)
- David L Waning
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA
| | | | | | | |
Collapse
|
27
|
Ferreira L, Villar E, Muñoz-Barroso I. Conformational changes of Newcastle disease virus envelope glycoproteins triggered by gangliosides. ACTA ACUST UNITED AC 2004; 271:581-8. [PMID: 14728685 DOI: 10.1111/j.1432-1033.2003.03960.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have investigated the conformational changes of Newcastle disease virus (NDV) glycoproteins in response to receptor binding, using 1,1-bis(4-anilino)naphthalene-5,5-disulfonic acid (bis-ANS) as a hydrophobicity-sensitive probe. Temperature- and pH-dependent conformational changes were detected in the presence of free bovine gangliosides. The fluorescence of bis-ANS was maximal at pH 5. The binding of bis-ANS to NDV was not affected by chemicals that denature the fusion glycoprotein, such as reducing agents, nor by the presence of neuraminidase inhibitors such as N-acetyl neuramicic acid. Gangliosides partially inhibited fusion and hemadsorption, but not neuraminidase hemagglutinin-neuraminidase glycoprotein (HN) activity. A conformational intermediate of HN, triggered by the presence of gangliosides acting as receptor mimics, was detected. Our results indicate that, upon binding to free gangliosides, HN undergoes a certain conformational change that does not affect the fusion glycoprotein.
Collapse
Affiliation(s)
- Laura Ferreira
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Spain
| | | | | |
Collapse
|