Modulation of coronavirus‐mediated cell fusion by homeostatic control of cholesterol and fatty acid metabolism

Cervin, Marguerite A.; Anderson, Robert

doi:10.1002/jmv.1890350213

Cited by 22 publications

(19 citation statements)

References 24 publications

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“…Studies with the N-terminal fusion peptide of HIV gp41 also suggest that cholesterol may play a role in HIV fusion (43,44), although these studies examine the fusion peptide out of the normal context of the intact virus envelope protein and its physiological fusion trigger of receptor and coreceptor (26). Studies of the coronavirus mouse hepatitis virus suggest that susceptibility to a lytic virus infection and generation of virus-induced syncytia may be influenced by cellular cholesterol content (11,16). Infection and fusion of African swine fever virus are affected by cellular cholesterol content (7), although the restricted host range of this virus of necessity required that these studies be performed in mammalian cells in which cholesterol depletion is limited and may produce toxic effects (26).…”

Section: Discussionmentioning

confidence: 99%

Biochemical Consequences of a Mutation That Controls the Cholesterol Dependence of Semliki Forest Virus Fusion

Chatterjee

Vashishtha

Kielian

2000

J Virol

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The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a low-pH-triggered membrane fusion reaction that requires cholesterol and sphingolipid in the target membrane. Cholesterol-depleted insect cells are highly resistant to alphavirus infection and were used to select srf-3, an SFV mutant that is ϳ100-fold less cholesterol dependent for infection due to a single amino acid change in the E1 spike subunit, proline 226 to serine. Sensitive lipid-mixing assays here demonstrated that the in vitro fusion of srf-3 and wild-type (wt) virus with cholesterol-containing liposomes had comparable kinetics, activation energies, and sphingolipid dependence. In contrast, srf-3 fusion with sterol-free liposomes was significantly more efficient than that of wt virus. Thus, the srf-3 mutation does not affect its general fusion properties with purified lipid bilayers but causes a marked and specific reduction in cholesterol dependence. Upon exposure to low pH, the E1 spike subunit undergoes distinct conformational changes, resulting in the exposure of an acid conformation-specific epitope and formation of an E1 homotrimer. These conformational changes were strongly cholesterol and sphingolipid dependent for wt SFV and strikingly less cholesterol dependent for srf-3. Our results thus demonstrate the functional importance of fusogenic E1 conformational changes in the control of SFV cholesterol dependence.In spite of long-standing interest in the role of cholesterol, its functions in eukaryotic cells are not well understood. Cholesterol is essential for mammalian cells and is believed to be required as both a bulk component of cell membranes and a specific modulator of membrane protein function (reviewed in references 40 and 57). Increased evidence for the importance of cholesterol has come from recent studies demonstrating that cholesterol is a covalent adduct critical for the function of embryonic signalling molecules (46) and that cholesterol is involved in the formation and function of caveolae and clathrin-coated vesicles, key membrane specializations in mammalian cells (5, 47, 52). A well-defined example of a membrane protein with a specific functional requirement for cholesterol is the Semliki Forest virus (SFV) spike glycoprotein, which requires cholesterol to mediate the fusion of the virus membrane with a target membrane. Membrane fusion is the mechanism used by enveloped viruses to infect cells and also plays a key role in such important cellular processes as endocytosis, exocytosis, and cell-cell fusion (22). The SFV spike protein thus illustrates the potential importance of specific membrane lipids in the function of a fusion protein and represents a model for cholesterol-membrane protein interactions.SFV is a member of the alphaviruses, enveloped RNA viruses that infect cells by using receptor-mediated endocytosis and low-pH-mediated fusion of the virus membrane with that of the endosome (reviewed in references 19, 25, 26, and 51). SFV fusion with liposomes has a striking requirement for two specific lipid...

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Section: Discussionmentioning

confidence: 99%

Biochemical Consequences of a Mutation That Controls the Cholesterol Dependence of Semliki Forest Virus Fusion

Chatterjee

Vashishtha

Kielian

2000

J Virol

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“…Also, the SFV envelope itself is rich in SPM (Renkonen et al, 1971;Allan and Quinn, 1989). Furthermore, although it had been reported that the majority of the SPM would be located on the inner leaflet of the SFV bilayer (Van Meer et al, 1981), in a more recent study it was concluded that the SPM and PC in the SFV envelope are exposed at the outer surface (Allan and Quinn, 1989 (Malvoisin and Wild, 1990;Cervin and Anderson, 1991), including HIV (Sarin et al, 1985;Hansen et al, 1990;Aloia et al, 1988Aloia et al, , 1993. Like that of SFV, the envelope of HIV is rich in SPM and cholesterol (Aloia et al, 1988(Aloia et al, , 1993.…”

Section: Discussion Fusion Of Sfv Requires Sphingolipids In the Targementioning

confidence: 99%

Membrane fusion of Semliki Forest virus requires sphingolipids in the target membrane.

et al. 1994

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Enveloped animal viruses, such as Semliki Forest virus (SFV), utilize a membrane fusion strategy to deposit their genome into the cytosol of the host cell. SFV enters cells through receptor-mediated endocytosis, fusion of the viral envelope occurring subsequently from within acidic endosomes. Fusion of SFV has been demonstrated before to be strictly dependent on the presence of cholesterol in the target membrane. Here, utilizing a variety of membrane fusion assays, including an on-line fluorescence assay involving pyrene-labeled virus, we demonstrate that low-pH-induced fusion of SFV with cholesterol-containing liposomal model membranes requires the presence of sphingomyelin or other sphingolipids in the target membrane. The miinimal molecular characteristics essential for supporting SFV fusion are encompassed by a ceramide. The action of the sphingolipids is confined to the actual fusion event, cholesterol being necessary and sufficient for low-pHdependent binding of the virus to target membranes. Complex formation of the sphingolipids with cholesterol is unlikely to be important for the induction of SFV-liposome fusion, as sphingolipids that do not interact appreciably with cholesterol, such as galactosylceramide, effectively support the process. The remarkably low levels of sphingomyelin required for halfmaximal fusion (1-2 mole%) suggest that sphingolipids do not play a structural role in the SFV fusion process, but rather act as a cofactor, possibly activating the viral fusion protein in a specific manner.

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“…Numerous studies have demonstrated that cell cultures exposed to M␤CD, a well-studied cyclic polysaccharide that specifically chelates cholesterol (39), become resistant to infection by a variety of enveloped viruses (7,49). That MHV infection might also be sensitive to M␤CD was suggested by the results of previous studies indicating that cholesterol-supplemented murine cells were hypersensitive to MHV-induced syncytia (13,19). Thus, we exposed murine 17 cl 1 fibroblast monolayers to increasing doses of M␤CD for 30 min at 37°C.…”

Section: Cholesterol Levels Can Determine Cellular Susceptibility To mentioning

confidence: 97%

“…Changes in the lipid composition of cellular membranes can have pronounced effects on the outcome of coronavirus infection. This was first documented in tissue culture, where the syncytia expanding from foci of murine hepatitis virus (MHV) infection were substantially larger after cholesterol supplementations (13,19,67). Subsequent in vivo experiments established correlations between cholesterol-rich diets and susceptibility of mice to pathogenic MHV infection (9).…”

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confidence: 98%

Requirements for CEACAMs and Cholesterol during Murine Coronavirus Cell Entry

Thorp

Gallagher

2004

J Virol

107

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Previous reports have documented that cholesterol supplementations increase cytopathic effects in tissue culture and also intensify in vivo pathogenicities during infection by the enveloped coronavirus murine hepatitis virus (MHV). To move toward a mechanistic understanding of these phenomena, we used growth media enriched with methyl-␤-cyclodextrin or cholesterol to reduce or elevate cellular membrane sterols, respectively. Cholesterol depletions reduced plaque development 2-to 20-fold, depending on the infecting MHV strain, while supplementations increased susceptibility 2-to 10-fold. These various cholesterol levels had no effect on the binding of viral spike (S) proteins to cellular carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptors, rather they correlated directly with S-protein-mediated membrane fusion activities. We considered whether cholesterol was indirectly involved in membrane fusion by condensing CEACAMs into "lipid raft" membrane microdomains, thereby creating opportunities for simultaneous binding of multiple S proteins that subsequently cooperate in the receptor-triggered membrane fusion process. However, the vast majority of CEACAMs were solubilized by cold Triton X-100 (TX-100), indicating their absence from lipid rafts. Furthermore, engineered CEACAMs appended to glycosylphosphatidylinositol anchors partitioned with TX-100-resistant lipid rafts, but cells bearing these raft-associated CEACAMs were not hypersensitive to MHV infection. These findings argued against the importance of cholesterol-dependent CEACAM localizations into membrane microdomains for MHV entry, instead suggesting that cholesterol had a more direct role. Indeed, we found that cholesterol was required even for those rare S-mediated fusions taking place in the absence of CEACAMs. We conclude that cholesterol is an essential membrane fusion cofactor that can act with or without CEACAMs to promote MHV entry.

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Modulation of coronavirus‐mediated cell fusion by homeostatic control of cholesterol and fatty acid metabolism

Cited by 22 publications

References 24 publications

Biochemical Consequences of a Mutation That Controls the Cholesterol Dependence of Semliki Forest Virus Fusion

Biochemical Consequences of a Mutation That Controls the Cholesterol Dependence of Semliki Forest Virus Fusion

Membrane fusion of Semliki Forest virus requires sphingolipids in the target membrane.

Requirements for CEACAMs and Cholesterol during Murine Coronavirus Cell Entry

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