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A single amino acid substitution in the capsid of foot-and-mouth disease virus can increase acid lability and confer resistance to acid-dependent uncoating inhibition. J Virol 2010; 84:2902-12. [PMID: 20053737 DOI: 10.1128/jvi.02311-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The acid-dependent disassembly of foot-and-mouth disease virus (FMDV) is required for viral RNA release from endosomes to initiate replication. Although the FMDV capsid disassembles at acid pH, mutants escaping inhibition by NH(4)Cl of endosomal acidification were found to constitute about 10% of the viruses recovered from BHK-21 cells infected with FMDV C-S8c1. For three of these mutants, the degree of NH(4)Cl resistance correlated with the sensitivity of the virion to acid-induced inactivation of its infectivity. Capsid sequencing revealed the presence in each of these mutants of a different amino acid substitution (VP3 A123T, VP3 A118V, and VP2 D106G) that affected a highly conserved residue among FMDVs located close to the capsid interpentameric interfaces. These residues may be involved in the modulation of the acid-induced dissociation of the FMDV capsid. The substitution VP3 A118V present in mutant c2 was sufficient to confer full resistance to NH(4)Cl and concanamycin A (a V-ATPase inhibitor that blocks endosomal acidification) as well as to increase the acid sensitivity of the virion to an extent similar to that exhibited by mutant c2 relative to the sensitivity of the parental virus C-S8c1. In addition, the increased propensity to dissociation into pentameric subunits of virions bearing substitution VP3 A118V indicates that this replacement also facilitates the dissociation of the FMDV capsid.
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Abstract
The picornavirus family consists of a large number of small RNA viruses, many of which are significant pathogens of humans and livestock. They are amongst the simplest of vertebrate viruses comprising a single stranded positive sense RNA genome within a T = 1 (quasi T = 3) icosahedral protein capsid of approximately 30 nm diameter. The structures of a number of picornaviruses have been determined at close to atomic resolution by X-ray crystallography. The structures of cell entry intermediate particles and complexes of virus particles with receptor molecules or antibodies have also been obtained by X-ray crystallography or at a lower resolution by cryo-electron microscopy. Many of the receptors used by different picornaviruses have been identified, and it is becoming increasingly apparent that many use co-receptors and alternative receptors to bind to and infect cells. However, the mechanisms by which these viruses release their genomes and transport them across a cellular membrane to gain access to the cytoplasm are still poorly understood. Indeed, detailed studies of cell entry mechanisms have been made only on a few members of the family, and it is yet to be established how broadly the results of these are applicable across the full spectrum of picornaviruses. Working models of the cell entry process are being developed for the best studied picornaviruses, the enteroviruses. These viruses maintain particle integrity throughout the infection process and function as genome delivery modules. However, there is currently no model to explain how viruses such as cardio- and aphthoviruses that appear to simply dissociate into subunits during uncoating deliver their genomes into the cytoplasm.
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Affiliation(s)
- Tobias J. Tuthill
- Faculty of Biological Sciences, Institute for Molecular and Cellular Biology, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, West Yorkshire LS2 9JT, UK, Institute for Animal Health, Pirbright, Surrey GU24 ONF, UK,
| | - Elisabetta Groppelli
- Faculty of Biological Sciences Institute for Molecular and Cellular Biology, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, West Yorkshire LS2 9JT UK
| | - James M. Hogle
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA,
| | - David J. Rowlands
- Faculty of Biological Sciences Institute for Molecular and Cellular Biology, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, West Yorkshire LS2 9JT UK
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53
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Innate immune responses against foot-and-mouth disease virus: Current understanding and future directions. Vet Immunol Immunopathol 2009; 128:205-10. [DOI: 10.1016/j.vetimm.2008.10.296] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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54
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Internalization of swine vesicular disease virus into cultured cells: a comparative study with foot-and-mouth disease virus. J Virol 2009; 83:4216-26. [PMID: 19225001 DOI: 10.1128/jvi.02436-08] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We performed a comparative analysis of the internalization mechanisms used by three viruses causing important vesicular diseases in animals. Swine vesicular disease virus (SVDV) internalization was inhibited by treatments that affected clathrin-mediated endocytosis and required traffic through an endosomal compartment. SVDV particles were found in clathrin-coated pits by electron microscopy and colocalized with markers of early endosomes by confocal microscopy. SVDV infectivity was significantly inhibited by drugs that raised endosomal pH. When compared to foot-and-mouth disease virus (FMDV), which uses clathrin-mediated endocytosis, the early step of SVDV was dependent on the integrity of microtubules. SVDV-productive endocytosis was more sensitive to plasma membrane cholesterol extraction than that of FMDV, and differential cell signaling requirements for virus infection were also found. Vesicular stomatitis virus, a model virus internalized by clathrin-mediated endocytosis, was included as a control of drug treatments. These results suggest that different clathrin-mediated routes are responsible for the internalization of these viruses.
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55
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Ter-Avetisyan G, Tünnemann G, Nowak D, Nitschke M, Herrmann A, Drab M, Cardoso MC. Cell entry of arginine-rich peptides is independent of endocytosis. J Biol Chem 2008; 284:3370-8. [PMID: 19047062 PMCID: PMC2635027 DOI: 10.1074/jbc.m805550200] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Arginine-rich peptides are a subclass of cell-penetrating peptides that are
taken up by living cells and can be detected freely diffusing inside the
cytoplasm and nucleoplasm. This phenomenon has been attributed to either an
endocytic mode of uptake and a subsequent release from vesicles or to direct
membrane penetration (transduction). To distinguish between both
possibilities, we have blocked endocytic pathways suggested to be involved in
uptake of cell-penetrating peptides. We have then monitored by confocal
microscopy the uptake and distribution of the cell-penetrating transactivator
of transcription (TAT) peptide into living mammalian cells over time. To
prevent side effects of chemical inhibitors, we used genetically engineered
cells as well as different temperature. We found that a knockdown of
clathrin-mediated endocytosis and a knock-out of caveolin-mediated endocytosis
did not affect the ability of TAT to enter cells. In addition, the TAT peptide
showed the same intracellular distribution throughout the cytoplasm and
nucleus as in control cells. Even incubation of cells at 4 °C did not
abrogate TAT uptake nor change its intracellular distribution. We therefore
conclude that this distribution results from TAT peptide that directly
penetrated (transduced) the plasma membrane. The formation of nonselective
pores is unlikely, because simultaneously added fluorophores were not taken up
together with the TAT peptide. In summary, although the frequency and kinetics
of TAT transduction varied between cell types, it was independent of
endocytosis.
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56
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Host cell factors and functions involved in vesicular stomatitis virus entry. J Virol 2008; 83:440-53. [PMID: 18971266 DOI: 10.1128/jvi.01864-08] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Vesicular stomatitis virus (VSV) is an animal virus that based on electron microscopy and its dependence on acidic cellular compartments for infection is thought to enter its host cells in a clathrin-dependent manner. The exact cellular mechanism, however, is largely unknown. In this study, we characterized the entry kinetics of VSV and elucidated viral requirements for host cell factors during infection in HeLa cells. We found that endocytosis of VSV was a fast process with a half time of 2.5 to 3 min and that acid activation occurred within 1 to 2 min after internalization in early endosomes. The majority of viral particles were endocytosed in a clathrin-based, dynamin-2-dependent manner. Although associated with some of the surface-bound viruses, the classical adaptor protein complex AP-2 was not required for infection. Time-lapse microscopy revealed that the virus either entered preformed clathrin-coated pits or induced de novo formation of pits. Dynamin-2 was recruited to plasma membrane-confined virus particles. Thus, VSV can induce productive internalization by exploiting a specific combination of the clathrin-associated proteins and cellular functions.
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Heparan sulfate-binding foot-and-mouth disease virus enters cells via caveola-mediated endocytosis. J Virol 2008; 82:9075-85. [PMID: 18614639 DOI: 10.1128/jvi.00732-08] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Foot-and-mouth disease virus (FMDV) utilizes different cell surface macromolecules to facilitate infection of cultured cells. Virus, which is virulent for susceptible animals, infects cells via four members of the alpha(V) subclass of cellular integrins. In contrast, tissue culture adaptation of some FMDV serotypes results in the loss of viral virulence in the animal, accompanied by the loss of virus' ability to use integrins as receptors. These avirulent viral variants acquire positively charged amino acids on surface-exposed structural proteins, resulting in the utilization of cell surface heparan sulfate (HS) molecules as receptors. We have recently shown that FMDV serotypes utilizing integrin receptors enter cells via a clathrin-mediated mechanism into early endosomes. Acidification within the endosome results in a breakdown of the viral capsid, releasing the RNA, which enters the cytoplasm by a still undefined mechanism. Since there is evidence that HS internalizes bound ligands via a caveola-mediated mechanism, it was of interest to analyze the entry of FMDV by cell-surface HS. Using a genetically engineered variant of type O(1)Campos (O(1)C3056R) which can utilize both integrins and HS as receptors and a second variant (O(1)C3056R-KGE) which can utilize only HS as a receptor, we followed viral entry using confocal microscopy. After virus bound to cells at 4 degrees C, followed by a temperature shift to 37 degrees C, type O(1)C3056R-KGE colocalized with caveolin-1, while O(1)C3056R colocalized with both clathrin and caveolin-1. Compounds which either disrupt or inhibit the formation of lipid rafts inhibited the replication of O(1)C3056R-KGE. Furthermore, a caveolin-1 knockdown by RNA interference also considerably reduced the efficiency of O(1)C3056R-KGE infection. These results indicate that HS-binding FMDV enters the cells via the caveola-mediated endocytosis pathway and that caveolae can associate and traffic with endosomes. In addition, these results further suggest that the route of FMDV entry into cells is a function solely of the viral receptor.
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Quirin K, Eschli B, Scheu I, Poort L, Kartenbeck J, Helenius A. Lymphocytic choriomeningitis virus uses a novel endocytic pathway for infectious entry via late endosomes. Virology 2008; 378:21-33. [PMID: 18554681 DOI: 10.1016/j.virol.2008.04.046] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/22/2008] [Accepted: 04/28/2008] [Indexed: 10/21/2022]
Abstract
The endocytic entry of lymphocytic choriomeningitis virus (LCMV) into host cells was compared to the entry of viruses known to exploit clathrin or caveolae/raft-dependent pathways. Pharmacological inhibitors, expression of pathway-specific dominant-negative constructs, and siRNA silencing of clathrin together with electron and light microscopy provided evidence that although a minority population followed a classical clathrin-mediated mechanism of entry, the majority of these enveloped RNA viruses used a novel endocytic route to late endosomes. The pathway was clathrin, dynamin-2, actin, Arf6, flotillin-1, caveolae, and lipid raft independent but required membrane cholesterol. Unaffected by perturbation of Rab5 or Rab7 and apparently without passing through Rab5/EEA1-positive early endosomes, the viruses reached late endosomes and underwent acid-induced penetration. This membrane trafficking route between the plasma membrane and late endosomes may function in the turnover of a select group of surface glycoproteins such as the dystroglycan complex, which serves as the receptor of LCMV.
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Affiliation(s)
- Katharina Quirin
- Institute of Biochemistry, ETH Zurich, Schafmattstrasse 18, CH-8093 Zurich, Switzerland
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Desplanques AS, Nauwynck HJ, Vercauteren D, Geens T, Favoreel HW. Plasma membrane cholesterol is required for efficient pseudorabies virus entry. Virology 2008; 376:339-45. [PMID: 18471850 PMCID: PMC7103377 DOI: 10.1016/j.virol.2008.03.039] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 03/29/2008] [Accepted: 03/31/2008] [Indexed: 10/28/2022]
Abstract
Alphaherpesviruses comprise closely related viruses of man and animal, including herpes simplex virus, varicella-zoster virus and pseudorabies virus (PRV). Here, using methyl-beta-cyclodextrin and fluorescently tagged PRV, we directly show that depletion of cholesterol from the plasma membrane of host cells significantly reduces PRV entry. Cholesterol depletion did not reduce PRV attachment, but stalled virus particles at the plasma membrane before penetration of the cell. Cholesterol depletion results in destabilization of lipid raft microdomains in the plasma membrane, which have been shown before to be involved in efficient entry of different viruses. A significant fraction of PRV virions appears to localize juxtaposed to GM1, a lipid raft marker, during entry. Together, these data indicate that cholesterol and possibly cholesterol-rich lipid rafts may be important during PRV entry.
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Affiliation(s)
- Ann S Desplanques
- Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
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60
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West Nile virus entry requires cholesterol-rich membrane microdomains and is independent of alphavbeta3 integrin. J Virol 2008; 82:5212-9. [PMID: 18385233 DOI: 10.1128/jvi.00008-08] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
West Nile virus (WNV) has been the leading cause of viral encephalitis in the United States since 1999. The endocytic processes involved in the internalization of infectious WNV by various cell types are not well characterized, and the involvement of cholesterol-rich membrane microdomains, or lipid rafts, in the life cycle of WNV has not been investigated previously. In this study, we found that the depletion of cellular cholesterol levels by brief treatment with methyl-beta-cyclodextrin resulted in a 100-fold reduction of the titers of infectious WNV released into the culture supernatant, as well as a reduction in the number of WNV genome copies in the cholesterol-depleted cells. The addition of exogenous cholesterol to cholesterol-depleted cells reversed this effect. Cholesterol depletion postinfection did not affect WNV growth, suggesting that the effect occurs at the level of WNV entry. We also showed that while WNV entry did not require alphavbeta3 integrin and focal adhesion kinase, WNV particles failed to be internalized by cholesterol-depleted cells. Finally, we showed the colocalization of the WNV envelope protein and cholera toxin B, which is internalized in a lipid raft-dependent pathway, in microdomain clusters at the plasma membrane. These data suggest that WNV utilizes lipid rafts during initial stages of internalization and that the lipid rafts may contain a factor(s) that may enhance WNV endocytosis.
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