Deep-etch EM reveals that the early poxvirus envelope is a single membrane bilayer stabilized by a geodetic “honeycomb” surface coat

Heuser, John E.

doi:10.1083/jcb.200412169

Cited by 101 publications

(150 citation statements)

References 135 publications

(169 reference statements)

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“…This antibody (Hu anti-VACV Ab) originated from an individual who had been vaccinated five times against smallpox and contained 52% of anti-IMV and 3% of anti-EEV activity compared with Rb anti-VACV Ab (43). The results demonstrated the benefit of HP in combination with human antibody (versus Hu anti-VACV Ab alone; P Ͻ 0.05 for weight loss and signs of illness, days [4][5][6][7][8][9][10]. This suggested that PAs may be used in conjunction with vaccinia-immune globulin in treating smallpox and vaccinerelated complications.…”

Section: Resultsmentioning

confidence: 95%

See 1 more Smart Citation

Ligand-induced and nonfusogenic dissolution of a viral membrane

Law

Carter²,

Roberts³

et al. 2006

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

117

118

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Hitherto, all enveloped viruses were thought to shed their lipid membrane during entry into cells by membrane fusion. The extracellular form of Vaccinia virus has two lipid envelopes surrounding the virus core, and consequently a single fusion event will not deliver a naked core into the cell. Here we report a previously underscribed mechanism in which the outer viral membrane is disrupted by a ligand-induced nonfusogenic reaction, followed by the fusion of the inner viral membrane with the plasma membrane and penetration of the virus core into the cytoplasm. The dissolution of the outer envelope depends on interactions with cellular polyanionic molecules and requires the virus glycoproteins A34 and B5. This discovery represents a remarkable example of how viruses manipulate biological membranes, solves the topological problem of how a double-enveloped virus enters cells, reveals a new effect of polyanions on viruses, and provides a therapeutic approach for treatment of poxvirus infections, such as smallpox.antiviral therapy ͉ extracellular enveloped virus ͉ membrane dissolution ͉ Vaccinia virus ͉ virus entry H itherto, membrane fusion was the only known mechanism by which enveloped viruses overcome the lipid barrier to enter and replicate in cells (1, 2). Here we show that the extracellular enveloped virus (EEV) of Vaccinia virus (VACV) sheds its outer lipid membrane by a ligand-dependent nonfusogenic mechanism.VACV replication produces several distinct virions: the intracellular mature virus (IMV), intracellular enveloped virus, cellassociated enveloped virus (CEV), and EEV (3, 4). IMV is surrounded by one lipid membrane (5-9) and is physically robust to aid virus transmission between hosts. CEV and EEV are IMV particles wrapped with an additional membrane derived from the trans-Golgi network (10) or endosomes (11) and are responsible for virus dissemination within the host (4). This extra lipid envelope (EEV membrane) and the associated virus and host membrane proteins serve to protect the IMV particle within from immune surveillance and may contribute to a broader cell tropism of the virus (4). Recently, we provided unequivocal electron micrographs showing that IMV enters by fusion with the plasma membrane (8), consistent with previous reports (6,12,13), and the recent genetic evidence for entry by fusion (14-17). Once the naked core has entered the cytoplasm, it moves deeper into the cell on microtubules (18). However, for VACV EEV, the additional EEV membrane presents an unexplained topological problem for entry, because fusion of the EEV outer envelope with the plasma membrane or the membrane of an intracellular vesicle will release only an IMV, instead of a naked core, into the cytosol. For a recent review of VACV entry, see ref.19.Here we studied the entry of EEV by immuno-EM and demonstrated that the EEV outer membrane is disrupted at the point of cell contact after binding. This enables the IMV within to enter the cell by fusion with the plasma membrane. The ligands required for membrane rupture were ...

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Section: Resultsmentioning

confidence: 95%

“…IMV is surrounded by one lipid membrane (5)(6)(7)(8)(9) and is physically robust to aid virus transmission between hosts. CEV and EEV are IMV particles wrapped with an additional membrane derived from the trans-Golgi network (10) or endosomes (11) and are responsible for virus dissemination within the host (4).…”

mentioning

confidence: 99%

Ligand-induced and nonfusogenic dissolution of a viral membrane

Law

Carter²,

Roberts³

et al. 2006

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

117

118

View full text Add to dashboard Cite

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“…Moreover, ER, ERGIC, or Golgi proteins were not detected in the crescent membranes, and continuity between the latter and cytoplasmic tubules has been disputed (2,3). Similarly controversial is the nature of the IV and MV membranes, specifically whether they are composed of one (1)(2)(3)14) or two (8,15,16) sets of lipoprotein bilayers.…”

mentioning

confidence: 99%

Existence of an operative pathway from the endoplasmic reticulum to the immature poxvirus membrane

Husain

Weisberg

Moss

2006

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

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In thin sections of cells infected with vaccinia virus or other poxviruses, the viral membrane is first discerned as a crescent or circle lacking obvious continuity with a cellular organelle, presenting an appearance of de novo membrane biogenesis. This notion, which many consider heretical, is nevertheless consistent with the absence of a signature of endoplasmic reticulum (ER) trafficking, such as signal peptide cleavage or glycosylation, in any of the numerous viral membrane proteins. The purpose of this study was to determine whether an operative pathway exists between the ER and the immature virion membrane. We showed that the highly conserved A9 viral membrane protein was inserted into the ER of uninfected cells with the same topology as in viral membranes. Next, we found that replacement of the nonessential cytoplasmic tail of A9 with one containing COPII-binding sites reduced incorporation of the modified A9 into viral membranes and led to its accumulation in the Golgi apparatus, implying that A9 was inserted into the ER and then diverted from its natural path. Most importantly, we demonstrated cleavage of a heterologous signal peptide fused to the N-terminal region of A9 and localized the truncated protein in immature and mature virions. Additionally, immunoelectron micrographs showed A9 in tubules containing protein disulfide isomerase, an ER lumenal protein, near immature viral membranes. The present data provide strong evidence for an operative pathway from ER domains within the virus factory to the viral membrane. membrane protein trafficking ͉ vaccinia virus ͉ virus assembly

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“…The inability to discern clear continuity of the viral crescent membrane with a cellular organelle (4,7,8,10) led to speculation that the viral membrane is formed by a novel mechanism. Skepticism regarding de novo membrane formation, however, inspired efforts to obtain evidence for the origin of the IV membrane from a component of the cellular secretory pathway.…”

Section: Assembly Of Vaccinia Virus (Vacv) and Other Poxvirusesmentioning

confidence: 99%

“…begins with the formation of a crescent-shaped membrane that enlarges into a spherical immature virion (IV), which then condenses into a brick-shaped infectious mature virion (MV) (3,4,8). The MV consists of a core, containing the DNA genome as well as RNA polymerase and transcription factors, surrounded by a lipid membrane with more than 20 proteins, none of which are glycosylated.…”

Section: Assembly Of Vaccinia Virus (Vacv) and Other Poxvirusesmentioning

confidence: 99%