Structure of bluetongue virus particles by cryoelectron microscopy

Hewat, E.A.; Booth, Timothy F.; Roy, Polly

doi:10.1016/1047-8477(92)90068-l

Cited by 97 publications

(68 citation statements)

References 31 publications

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“…In BTV, VP2 protein has been shown to be responsible for receptor binding and has the viral hemagglutination activity (26). A 3D structural study of BTV particles by cryoelectron microscopy revealed that the receptorbinding VP2 protein is organized in trimers and forms triskelionlike structures that are closely associated with the globular VP5 oligomers on the virion surface (19). Hence, VP2 may have direct influence on the fusogenic activity of VP5.…”

Section: Is the Fusion Activity Of Vp5 Influenced By The Btv Receptormentioning

confidence: 99%

“…In contrast to VP2, much less is known of the role of the closely associated 60-kDa, VP5 protein, the inner adjacent layer to VP2, in virus infection. VP5 has an overall globular configuration and is less exposed than VP2 on the surface of the particles (19,20). From our previous studies it appears that VP5 is likely to be involved in cell permeabilization and translocation of the internal core into the cytosol of the infected cells (27).…”

mentioning

confidence: 99%

“…The outer capsid in turn encapsidates the internal capsid, or core, which is composed of two major proteins (VP3 and VP7) and three minor proteins (VP1, VP4, and VP6), in addition to the genome of 10 segments of double-stranded RNA (16)(17)(18). The 110-kDa VP2 is the outermost viral protein and has a sail-shaped protruding triskelion spike-like structure (19,20). It is the cellular receptor binding protein, elicits virus-neutralizing antibody, and is responsible for hemagglutination activity and serotype specificity (21)(22)(23)(24)(25)(26).…”

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confidence: 99%

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A capsid protein of nonenveloped Bluetongue virus exhibits membrane fusion activity

Forzan

Wirblich

Roy

2004

Proc. Natl. Acad. Sci. U.S.A.

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The outer capsid layer of Bluetongue virus, a member of the nonenveloped Reoviridae family, is composed of two proteins, a receptor-binding protein, VP2, and a second protein, VP5, which shares structural features with class I fusion proteins of enveloped viruses. In the replication cycle of Bluetongue virus VP5 acts as a membrane permeabilization protein that mediates release of viral particles from endosomal compartments into the cytoplasm. Here, we show that VP5 can also act as a fusion protein and induce syncytium formation when it is fused to a transmembrane anchor and expressed on the cell surface. Fusion activity is strictly pHdependent and is triggered by short exposure to low pH. No cell-cell fusion is observed at neutral pH. Deletion of the first 40 amino acids, which can fold into two amphipathic helices, abolishes fusion activity. Syncytium formation by VP5 is inhibited in the presence of VP2 when it is expressed in a membrane-anchored form. The data indicate an interaction between the outer capsid protein VP2 and VP5 and show that VP5 undergoes pH-dependent conformational changes that render it capable of interacting with cellular membranes. More importantly, our data show that a membrane permeabilization protein of a nonenveloped virus can evolve into a fusion protein by the addition of an appropriate transmembrane anchor. The results strongly suggest that the mechanism of membrane permeabilization by VP5 and membrane fusion by viral fusion proteins require similar structural features and conformational changes.

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Section: Is the Fusion Activity Of Vp5 Influenced By The Btv Receptormentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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A capsid protein of nonenveloped Bluetongue virus exhibits membrane fusion activity

Forzan

Wirblich

Roy

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…BTV virions are architecturally complex icosahedral structures composed of seven discrete proteins that are organized into outer and inner capsids that surround a genome of 10 double-stranded RNA segments (6)(7)(8). The outer capsid, which is composed of two major structural proteins (VP2 and VP5), is involved in cell attachment and virus penetration during the initial stages of infection (9,10).…”

mentioning

confidence: 99%

The membrane trafficking protein calpactin forms a complex with bluetongue virus protein NS3 and mediates virus release

Beaton

Rodrı́guez

Reddy

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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120

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Bluetongue virus, an arbovirus of the Orbivirus genus, infects and replicates in both insect and mammalian cells. However, the cytopathic effect (cpe) on each host is very different. Mammalian cells show substantial cpe, most likely a result of the mechanism of virus release, whereas insect cells show little cpe and appear to release virus without cell lysis. Expression analysis of each infected cell type shows one protein, the nonstructural (NS) protein NS3, to be differentially expressed in the different cell types, suggesting it may act in the virus egress pathway. The molecular basis of such an interaction, however, has never been clear. Here, by using yeast two-hybrid analysis, we show that NS3 interacts with a cellular protein p11 (calpactin light chain), part of the annexin II complex that is involved in exocytosis. We map the NS3 region of interaction with p11 to a 13-residue peptide found at the N terminus of the protein and show it effectively competes with p36 (annexin II heavy chain) for p11 ligand binding. Further, we show that the C-terminal domain of NS3 interacts with VP2, the outermost protein of the fully assembled virus particle, suggesting that NS3 forms a bridging molecule that draws assembled virus into contact with the cellular export machinery. Our data describe the first host protein involvement in orbivirus egress and provide new insights into understanding arbovirus interactions with their hosts.I nsect-borne arboviruses (arthropod-borne viruses), such as members of genus Orbivirus, are vectored to vertebrate species by arthropod species (e.g., gnats, mosquitoes, and ticks) and replicate in both hosts. However, whereas in vertebrate host cells these viruses cause severe cell damage, infections of insect cells are often inapparent. Bluetongue virus (BTV), the prototype virus of the genus Orbivirus, is transmitted by Culicoides spp., causing a disease of economical importance in the vertebrate hosts (ruminants) in many parts of the world. Other orbiviruses (14 serogroups within the genus, including African horse sickness virus and Epizootic hemorrhagic disease virus of deer) infect a variety of vertebrates, including humans, often causing severe diseases (1).Unlike the other arboviruses, BTV and other orbiviruses are nonenveloped and lack the glycosylated proteins known to facilitate both virus entry and exit processes. Consequently, orbiviruses are released from the infected cells predominantly by cell lysis (2, 3). However, BTV causes less severe cytopathic effects in insect vector cells despite highly efficient virus replication (4). BTV release from vector cells is nonlytic, and the virus particles leave the infected cell by passage, either individually or in groups, through a locally disrupted plasma membrane (5). However, the exact mechanism of cell-to-cell spread by the virus is not clear, and how the virus controls differential egress in insect and mammalian cells is one of the most intriguing aspects of BTV biology.BTV virions are architecturally complex icosahedral structures c...

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“…Well-known species are the bluetongue virus (BTV), African horsesickness virus (AHSV), epizootic hemorrhagic disease virus (EHDV) and equine encephalosis virus (EEV), which are all transmitted by Culicoides biting midges and cause disease in ruminants (BTV and EHDV) or equids (AHSV and EEV). Orbiviruses are non-enveloped, architecturally complex viruses *80 nm in diameter, which are composed of structural proteins VP1-7 organized in three capsid shells (Hewat et al, 1992). In addition, at least four non-structural (NS) viral proteins are expressed after infection (Belhouchet et al, 2011;Ratinier et al, 2011;Roy, 2005;Stewart et al, 2015;Zwart et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Balance of RNA sequence requirement and NS3/NS3a expression of segment 10 of orbiviruses

Feenstra

Gennip²,

Schreuder³

et al. 2016

Journal of General Virology

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Orbiviruses are insect-transmitted, non-enveloped viruses with a ten-segmented dsRNA genome of which the bluetongue virus (BTV) is the prototype. Viral non-structural protein NS3/NS3a is encoded by genome segment 10 (Seg-10), and is involved in different virus release mechanisms. This protein induces specific release via membrane disruptions and budding in both insect and mammalian cells, but also the cytopathogenic release that is only seen in mammalian cells. NS3/NS3a is not essential for virus replication in vitro with BTV Seg-10 containing RNA elements essential for virus replication, even if protein is not expressed. Recently, new BTV serotypes with distinct NS3/NS3a sequence and cell tropism have been identified. Multiple studies have hinted at the importance of Seg-10 in orbivirus replication, but the exact prerequisites are still unknown. Here, more insight is obtained with regard to the needs for orbivirus Seg-10 and the balance between protein expression and RNA elements. Multiple silent mutations in the BTV NS3a ORF destabilized Seg-10, resulting in deletions and sequences originating from other viral segments being inserted, indicating strong selection at the level of RNA during replication in mammalian cells in vitro. The NS3a ORFs of other orbiviruses were successfully exchanged in BTV1 Seg-10, resulting in viable chimeric viruses. NS3/NS3a proteins in these chimeric viruses were generally functional in mammalian cells, but not in insect cells. NS3/NS3a of the novel BTV serotypes 25 and 26 affected virus release from Culicoides cells, which might be one of the reasons for their distinct cell tropism.

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Structure of bluetongue virus particles by cryoelectron microscopy

Cited by 97 publications

References 31 publications

A capsid protein of nonenveloped Bluetongue virus exhibits membrane fusion activity

A capsid protein of nonenveloped Bluetongue virus exhibits membrane fusion activity

The membrane trafficking protein calpactin forms a complex with bluetongue virus protein NS3 and mediates virus release

Balance of RNA sequence requirement and NS3/NS3a expression of segment 10 of orbiviruses

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