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Tan WS, Rong E, Dry I, Lillico S, Law A, Digard P, Whitelaw B, Dalziel RG. Validation of Candidate Host Cell Entry Factors for Bovine Herpes Virus Type-1 Based on a Genome-Wide CRISPR Knockout Screen. Viruses 2024; 16:297. [PMID: 38400072 PMCID: PMC10893506 DOI: 10.3390/v16020297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 02/09/2024] [Accepted: 02/13/2024] [Indexed: 02/25/2024] Open
Abstract
To identify host factors that affect Bovine Herpes Virus Type 1 (BoHV-1) infection we previously applied a genome wide CRISPR knockout screen targeting all bovine protein coding genes. By doing so we compiled a list of both pro-viral and anti-viral proteins involved in BoHV-1 replication. Here we provide further analysis of those that are potentially involved in viral entry into the host cell. We first generated single cell knockout clones deficient in some of the candidate genes for validation. We provide evidence that Polio Virus Receptor-related protein (PVRL2) serves as a receptor for BoHV-1, mediating more efficient entry than the previously identified Polio Virus Receptor (PVR). By knocking out two enzymes that catalyze HSPG chain elongation, HST2ST1 and GLCE, we further demonstrate the significance of HSPG in BoHV-1 entry. Another intriguing cluster of candidate genes, COG1, COG2 and COG4-7 encode six subunits of the Conserved Oligomeric Golgi (COG) complex. MDBK cells lacking COG6 produced fewer but bigger plaques compared to control cells, suggesting more efficient release of newly produced virions from these COG6 knockout cells, due to impaired HSPG biosynthesis. We further observed that viruses produced by the COG6 knockout cells consist of protein(s) with reduced N-glycosylation, potentially explaining their lower infectivity. To facilitate candidate validation, we also detailed a one-step multiplex CRISPR interference (CRISPRi) system, an orthogonal method to KO that enables quick and simultaneous deployment of three CRISPRs for efficient gene inactivation. Using CRISPR3i, we verified eight candidates that have been implicated in the synthesis of surface heparan sulfate proteoglycans (HSPGs). In summary, our experiments confirmed the two receptors PVR and PVRL2 for BoHV-1 entry into the host cell and other factors that affect this process, likely through the direct or indirect roles they play during HSPG synthesis and glycosylation of viral proteins.
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Affiliation(s)
- Wenfang Spring Tan
- Division of Infection and Immunity, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK (I.D.); (P.D.); (R.G.D.)
| | - Enguang Rong
- Division of Infection and Immunity, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK (I.D.); (P.D.); (R.G.D.)
| | - Inga Dry
- Division of Infection and Immunity, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK (I.D.); (P.D.); (R.G.D.)
| | - Simon Lillico
- Division of Functional Genetics and Development, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK; (S.L.); (B.W.)
- Centre for Tropical Livestock Genetics and Health, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK
| | - Andy Law
- Division of Genetics and Genomics, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK;
| | - Paul Digard
- Division of Infection and Immunity, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK (I.D.); (P.D.); (R.G.D.)
| | - Bruce Whitelaw
- Division of Functional Genetics and Development, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK; (S.L.); (B.W.)
- Division of Genetics and Genomics, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK;
| | - Robert G. Dalziel
- Division of Infection and Immunity, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh EH259RG, UK (I.D.); (P.D.); (R.G.D.)
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Tan WS, Rong E, Dry I, Lillico SG, Law A, Digard P, Whitelaw B, Dalziel RG. GARP and EARP are required for efficient BoHV-1 replication as identified by a genome wide CRISPR knockout screen. PLoS Pathog 2023; 19:e1011822. [PMID: 38055775 PMCID: PMC10727446 DOI: 10.1371/journal.ppat.1011822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 12/18/2023] [Accepted: 11/13/2023] [Indexed: 12/08/2023] Open
Abstract
The advances in gene editing bring unprecedented opportunities in high throughput functional genomics to animal research. Here we describe a genome wide CRISPR knockout library, btCRISPRko.v1, targeting all protein coding genes in the cattle genome. Using it, we conducted genome wide screens during Bovine Herpes Virus type 1 (BoHV-1) replication and compiled a list of pro-viral and anti-viral candidates. These candidates might influence multiple aspects of BoHV-1 biology such as viral entry, genome replication and transcription, viral protein trafficking and virion maturation in the cytoplasm. Some of the most intriguing examples are VPS51, VPS52 and VPS53 that code for subunits of two membrane tethering complexes, the endosome-associated recycling protein (EARP) complex and the Golgi-associated retrograde protein (GARP) complex. These complexes mediate endosomal recycling and retrograde trafficking to the trans Golgi Network (TGN). Simultaneous loss of both complexes in MDBKs resulted in greatly reduced production of infectious BoHV-1 virions. We also found that viruses released by these deficient cells severely lack VP8, the most abundant tegument protein of BoHV-1 that are crucial for its virulence. In combination with previous reports, our data suggest vital roles GARP and EARP play during viral protein packaging and capsid re-envelopment in the cytoplasm. It also contributes to evidence that both the TGN and the recycling endosomes are recruited in this process, mediated by these complexes. The btCRISPRko.v1 library generated here has been controlled for quality and shown to be effective in host gene discovery. We hope it will facilitate efforts in the study of other pathogens and various aspects of cell biology in cattle.
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Affiliation(s)
- Wenfang S. Tan
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Enguang Rong
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Inga Dry
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Simon G. Lillico
- Division of Functional Genetics and Development, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- Centre for Tropical Livestock Genetics and Health, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Andy Law
- Division of Genetics and Genomics, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Paul Digard
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Bruce Whitelaw
- Division of Functional Genetics and Development, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- Centre for Tropical Livestock Genetics and Health, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Robert G. Dalziel
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
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Thompson BH, Sharp CP, Dry IR, Dalziel RG, Gaunt ER. 1 Cellular protein TTC4 and its cofactor HSP90 are pro-viral for bovine herpesvirus 1. Virus Res 2022; 321:198927. [PMID: 36100007 DOI: 10.1016/j.virusres.2022.198927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 09/05/2022] [Accepted: 09/09/2022] [Indexed: 12/24/2022]
Abstract
Bovine Herpesvirus Type 1 (BoHV-1) infection causes infectious bovine rhinotracheitis and genital disease in cattle, with significant economic and welfare impacts. However, the role of cellular host factors during viral replication remains poorly characterised. A previously performed genome-wide CRISPR knockout screen identified pro- and antiviral host factors acting during BoHV-1 replication. Herein we validate a pro-viral role for a candidate from this screen: the cellular protein tetracopeptide repeat protein 4 (TTC4). We show that TTC4 transcript production is upregulated during BoHV-1 infection. Depletion of TTC4 protein impairs BoHV-1 protein production but does not reduce production of infectious virions, whereas overexpression of exogenous TTC4 results in a significant increase in production of infectious BoHV-1 virions. TTC4 itself is poorly characterized (especially in the context of virus infection), but is a known co-chaperone of heat shock protein 90 (HSP90). HSP90 has a well-characterized pro-viral role during the replication of diverse herpesviruses, and we therefore hypothesized that HSP90 is also pro-viral for BoHV-1. Drug-mediated inhibition of HSP90 using geldanamycin at sub-cytotoxic concentrations inhibited both BoHV-1 protein production and viral genome replication, indicating a pro-viral role for HSP90 during BoHV-1 infection. Our data demonstrates pro-viral roles for both TTC4 and HSP90 during BoHV-1 replication; possibly, interactions between these two proteins are required for optimal BoHV-1 replication, or the two proteins may have independent pro-viral roles.
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Affiliation(s)
- Beth H Thompson
- The Roslin Institute, The University of Edinburgh, Easter Bush Campus, Edinburgh, Midlothian EH25 9RG, UK
| | - Colin P Sharp
- The Roslin Institute, The University of Edinburgh, Easter Bush Campus, Edinburgh, Midlothian EH25 9RG, UK
| | - Inga R Dry
- The Roslin Institute, The University of Edinburgh, Easter Bush Campus, Edinburgh, Midlothian EH25 9RG, UK
| | - Robert G Dalziel
- The Roslin Institute, The University of Edinburgh, Easter Bush Campus, Edinburgh, Midlothian EH25 9RG, UK
| | - Eleanor R Gaunt
- The Roslin Institute, The University of Edinburgh, Easter Bush Campus, Edinburgh, Midlothian EH25 9RG, UK.
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4
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Craig N, Fletcher SL, Daniels A, Newman C, O’Shea M, Tan WS, Warr A, Tait-Burkard C. Direct Lysis RT-qPCR of SARS-CoV-2 in Cell Culture Supernatant Allows for Fast and Accurate Quantification. Viruses 2022; 14:v14030508. [PMID: 35336915 PMCID: PMC8949636 DOI: 10.3390/v14030508] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/16/2022] [Accepted: 02/25/2022] [Indexed: 11/16/2022] Open
Abstract
Studying the entire virus replication cycle of SARS-CoV-2 is essential to identify the host factors involved and treatments to combat infection. Quantification of released virions often requires lengthy procedures, whereas quantification of viral RNA in supernatant is faster and applicable to clinical isolates. Viral RNA purification is expensive in terms of time and resources, and is often unsuitable for high-throughput screening. Direct lysis protocols were explored for patient swab samples, but the lack of virus inactivation, cost, sensitivity, and accuracy is hampering their application and usefulness for in vitro studies. Here, we show a highly sensitive, accurate, fast, and cheap direct lysis RT-qPCR method for quantification of SARS-CoV-2 in culture supernatant. This method inactivates the virus and permits detection limits of 0.043 TCID50 virus and <1.89 copy RNA template per reaction. Comparing direct lysis with RNA extraction, a mean difference of +0.69 ± 0.56 cycles was observed. Application of the method to established qPCR methods for RSV (-ve RNA), IAV (segmented -ve RNA), and BHV (dsDNA) showed wider applicability to other enveloped viruses, whereby IAV showed poorer sensitivity. This shows that accurate quantification of SARS-CoV-2 and other enveloped viruses can be achieved using direct lysis protocols, facilitating a wide range of high- and low-throughput applications.
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Affiliation(s)
- Nicky Craig
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Sarah L. Fletcher
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Alison Daniels
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
- Division of Infection Medicine, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Caitlin Newman
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Marie O’Shea
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Wenfang Spring Tan
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Amanda Warr
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
| | - Christine Tait-Burkard
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK; (N.C.); (S.L.F.); (A.D.); (C.N.); (M.O.); (W.S.T.); (A.W.)
- Correspondence:
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Herpesvirus Nuclear Egress across the Outer Nuclear Membrane. Viruses 2021; 13:v13122356. [PMID: 34960625 PMCID: PMC8706699 DOI: 10.3390/v13122356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 01/22/2023] Open
Abstract
Herpesvirus capsids are assembled in the nucleus and undergo a two-step process to cross the nuclear envelope. Capsids bud into the inner nuclear membrane (INM) aided by the nuclear egress complex (NEC) proteins UL31/34. At that stage of egress, enveloped virions are found for a short time in the perinuclear space. In the second step of nuclear egress, perinuclear enveloped virions (PEVs) fuse with the outer nuclear membrane (ONM) delivering capsids into the cytoplasm. Once in the cytoplasm, capsids undergo re-envelopment in the Golgi/trans-Golgi apparatus producing mature virions. This second step of nuclear egress is known as de-envelopment and is the focus of this review. Compared with herpesvirus envelopment at the INM, much less is known about de-envelopment. We propose a model in which de-envelopment involves two phases: (i) fusion of the PEV membrane with the ONM and (ii) expansion of the fusion pore leading to release of the viral capsid into the cytoplasm. The first phase of de-envelopment, membrane fusion, involves four herpes simplex virus (HSV) proteins: gB, gH/gL, gK and UL20. gB is the viral fusion protein and appears to act to perturb membranes and promote fusion. gH/gL may also have similar properties and appears to be able to act in de-envelopment without gB. gK and UL20 negatively regulate these fusion proteins. In the second phase of de-envelopment (pore expansion and capsid release), an alpha-herpesvirus protein kinase, US3, acts to phosphorylate NEC proteins, which normally produce membrane curvature during envelopment. Phosphorylation of NEC proteins reverses tight membrane curvature, causing expansion of the membrane fusion pore and promoting release of capsids into the cytoplasm.
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Development of a reliable bovine neuronal cell culture system and labeled recombinant bovine herpesvirus type-1 for studying virus-host cell interactions. Virus Res 2020; 293:198255. [PMID: 33338533 DOI: 10.1016/j.virusres.2020.198255] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/24/2020] [Accepted: 11/25/2020] [Indexed: 11/22/2022]
Abstract
Bovine herpesvirus type 1 (BoHV-1) is the viral causative agent of infectious bovine rhinotracheitis and a component of the bovine respiratory complex commonly referred to as shipping fever in calves. BoHV-1 is also responsible for losses of aborted calves and reductions in dairy productivity. BoHV-1 belongs to the neurotropic alphaherpesviruses which have a predilection to infect and establish latency in sensory neurons. Neuronal cell cultures provide a useful platform for experiments investigating neuronal entry, retrograde and anterograde transport, and the establishment of latency. Rodent neuronal cell lines and primary rabbit neuronal cells have been utilized for BoHV-1, though a reliable host-specific neuronal cell culture system has not been developed. In this study, BoHV-1 readily infected bovine-derived immortalized neuronal progenitor cells (FBBC-1) differentiated in cell culture producing neurite-like projections and exhibiting neuronal cell markers NeuN and L1CAM. FBBC-1 cells expressed both nectin-1 and nectin-2 alphaherpesvirus receptors on their cell surfaces, however, nectin-2 was detected in much greater abundance than nectin-1. To facilitate investigations of BoHV-1 infection, a recombinant BoHV-1 virus expressing the green fluorescent protein (GFP) cloned into a bacterial artificial chromosome (BAC) was used to generate an mCherry-VP26 fusion protein. The BoHV-1 GFP expressing VP26mCherry labeled virus infected differentiated FBBC-1 cells as evidenced by the production of infectious virions and the expression of both GFP and mCherry fluorophores. Time-lapse live cell microscopy revealed the presence of mCherry fluorescent capsids in neuronal projections immediately after virus entry moving retrograde in a saltatory manner. Proximity ligation assays (PLA) using MDBK cells demonstrated that BoHV-1 glycoprotein D (gD) interacted more efficiently with nectin-1 than nectin-2. However, the gD interaction with nectin-2 predominated in differentiated FBBC-1 cells in comparison to the gD nectin-1 interaction. The efficiently differentiated FBBC-1 neuronal cell line and fluorescently labeled BoHV-1 virions will assist experimentation aiming to elucidate specific mechanisms of virus entry and transport in a homologous bovine neuronal cell culture system.
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Alkalay E, Gam Ze Letova Refael C, Shoval I, Kinor N, Sarid R, Shav-Tal Y. The Sub-Nuclear Localization of RNA-Binding Proteins in KSHV-Infected Cells. Cells 2020; 9:cells9091958. [PMID: 32854341 PMCID: PMC7564026 DOI: 10.3390/cells9091958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 08/21/2020] [Indexed: 12/13/2022] Open
Abstract
RNA-binding proteins, particularly splicing factors, localize to sub-nuclear domains termed nuclear speckles. During certain viral infections, as the nucleus fills up with replicating virus compartments, host cell chromatin distribution changes, ending up condensed at the nuclear periphery. In this study we wished to determine the fate of nucleoplasmic RNA-binding proteins and nuclear speckles during the lytic cycle of the Kaposi's sarcoma associated herpesvirus (KSHV). We found that nuclear speckles became fewer and dramatically larger, localizing at the nuclear periphery, adjacent to the marginalized chromatin. Enlarged nuclear speckles contained splicing factors, whereas other proteins were nucleoplasmically dispersed. Polyadenylated RNA, typically found in nuclear speckles under regular conditions, was also found in foci separated from nuclear speckles in infected cells. Poly(A) foci did not contain lncRNAs known to colocalize with nuclear speckles but contained the poly(A)-binding protein PABPN1. Examination of the localization of spliced viral RNAs revealed that some spliced transcripts could be detected within the nuclear speckles. Since splicing is required for the maturation of certain KSHV transcripts, we suggest that the infected cell does not dismantle nuclear speckles but rearranges their components at the nuclear periphery to possibly serve in splicing and transport of viral RNAs into the cytoplasm.
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Meier AF, Fraefel C, Seyffert M. The Interplay between Adeno-Associated Virus and its Helper Viruses. Viruses 2020; 12:E662. [PMID: 32575422 PMCID: PMC7354565 DOI: 10.3390/v12060662] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 06/15/2020] [Accepted: 06/18/2020] [Indexed: 12/14/2022] Open
Abstract
The adeno-associated virus (AAV) is a small, nonpathogenic parvovirus, which depends on helper factors to replicate. Those helper factors can be provided by coinfecting helper viruses such as adenoviruses, herpesviruses, or papillomaviruses. We review the basic biology of AAV and its most-studied helper viruses, adenovirus type 5 (AdV5) and herpes simplex virus type 1 (HSV-1). We further outline the direct and indirect interactions of AAV with those and additional helper viruses.
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Affiliation(s)
| | | | - Michael Seyffert
- Institute of Virology, University of Zurich, CH-8057 Zurich, Switzerland; (A.F.M.); (C.F.)
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Banerjee A, Kulkarni S, Mukherjee A. Herpes Simplex Virus: The Hostile Guest That Takes Over Your Home. Front Microbiol 2020; 11:733. [PMID: 32457704 PMCID: PMC7221137 DOI: 10.3389/fmicb.2020.00733] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 03/30/2020] [Indexed: 12/15/2022] Open
Abstract
Alpha (α)-herpesviruses (HSV-1 and HSV-2), like other viruses, are obligate intracellular parasites. They hijack the cellular machinery to survive and replicate through evading the defensive responses by the host. The viral genome of herpes simplex viruses (HSVs) contains viral genes, the products of which are destined to exploit the host apparatus for their own existence. Cellular modulations begin from the entry point itself. The two main gateways that the virus has to penetrate are the cell membrane and the nuclear membrane. Changes in the cell membrane are triggered when the glycoproteins of HSV interact with the surface receptors of the host cell, and from here, the components of the cytoskeleton take over. The rearrangement in the cytoskeleton components help the virus to enter as well as transport to the nucleus and back to the cell membrane to spread out to the other cells. The entire carriage process is also mediated by the motor proteins of the kinesin and dynein superfamily and is directed by the viral tegument proteins. Also, the virus captures the cell’s most efficient cargo carrying system, the endoplasmic reticulum (ER)–Golgi vesicular transport machinery for egress to the cell membrane. For these reasons, the host cell has its own checkpoints where the normal functions are halted once a danger is sensed. However, a cell may be prepared for the adversities from an invading virus, and it is simply commendable that the virus has the antidote to these cellular strategies as well. The HSV viral proteins are capable of limiting the use of the transcriptional and translational tools for the cell itself, so that its own transcription and translation pathways remain unhindered. HSV prefers to constrain any self-destruction process of the cell—be it autophagy in the lysosome or apoptosis by the mitochondria, so that it can continue to parasitize the cell for its own survival. This review gives a detailed account of the significance of compartmentalization during HSV pathogenesis. It also highlights the undiscovered areas in the HSV cell biology research which demand attention for devising improved therapeutics against the infection.
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Affiliation(s)
- Anwesha Banerjee
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
| | - Smita Kulkarni
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
| | - Anupam Mukherjee
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
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Wild P, Leisinger S, de Oliveira AP, Doehner J, Schraner EM, Fraevel C, Ackermann M, Kaech A. Nuclear envelope impairment is facilitated by the herpes simplex virus 1 Us3 kinase. F1000Res 2019; 8:198. [PMID: 31249678 PMCID: PMC6584977 DOI: 10.12688/f1000research.17802.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/11/2019] [Indexed: 12/22/2022] Open
Abstract
Background: Capsids of herpes simplex virus 1 (HSV-1) are assembled in the nucleus, translocated either to the perinuclear space by budding at the inner nuclear membrane acquiring tegument and envelope, or released to the cytosol in a "naked" state via impaired nuclear pores that finally results in impairment of the nuclear envelope. The Us3 gene encodes a protein acting as a kinase, which is responsible for phosphorylation of numerous viral and cellular substrates. The Us3 kinase plays a crucial role in nucleus to cytoplasm capsid translocation. We thus investigate the nuclear surface in order to evaluate the significance of Us3 in maintenance of the nuclear envelope during HSV-1 infection. Methods: To address alterations of the nuclear envelope and capsid nucleus to cytoplasm translocation related to the function of the Us3 kinase we investigated cells infected with wild type HSV-1 or the Us3 deletion mutant R7041(∆Us3) by transmission electron microscopy, focused ion-beam electron scanning microscopy, cryo-field emission scanning electron microscopy, confocal super resolution light microscopy, and polyacrylamide gel electrophoresis. Results: Confocal super resolution microscopy and cryo-field emission scanning electron microscopy revealed decrement in pore numbers in infected cells. Number and degree of pore impairment was significantly reduced after infection with R7041(∆Us3) compared to infection with wild type HSV-1. The nuclear surface was significantly enlarged in cells infected with any of the viruses. Morphometric analysis revealed that additional nuclear membranes were produced forming multiple folds and caveolae, in which virions accumulated as documented by three-dimensional reconstruction after ion-beam scanning electron microscopy. Finally, significantly more R7041(∆Us3) capsids were retained in the nucleus than wild-type capsids whereas the number of R7041(∆Us3) capsids in the cytosol was significantly lower. Conclusions: The data indicate that Us3 kinase is involved in facilitation of nuclear pore impairment and, concomitantly, in capsid release through impaired nuclear envelope.
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Affiliation(s)
- Peter Wild
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | - Sabine Leisinger
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | | | - Jana Doehner
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
| | - Elisabeth M. Schraner
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Cornel Fraevel
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Mathias Ackermann
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Andres Kaech
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
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Tunneling Nanotubes as a Novel Route of Cell-to-Cell Spread of Herpesviruses. J Virol 2018; 92:JVI.00090-18. [PMID: 29491165 DOI: 10.1128/jvi.00090-18] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 02/12/2018] [Indexed: 12/21/2022] Open
Abstract
Various types of intercellular connections that are essential for communication between cells are often utilized by pathogens. Recently, a new type of cellular connection, consisting of long, thin, actin-rich membrane extensions named tunneling nanotubes (TNTs), has been shown to play an important role in cell-to-cell spread of HIV and influenza virus. In the present report, we show that TNTs are frequently formed by cells infected by an alphaherpesvirus, bovine herpesvirus 1 (BoHV-1). Viral proteins, such as envelope glycoprotein E (gE), capsid protein VP26, and tegument protein Us3, as well as cellular organelles (mitochondria) were detected by immunofluorescence and live-cell imaging of nanotubes formed by bovine primary fibroblasts and oropharynx cells (KOP cells). Time-lapse confocal studies of live cells infected with fluorescently labeled viruses showed that viral particles were transmitted via TNTs. This transfer also occurred in the presence of neutralizing antibodies, which prevented free entry of BoHV-1. We conclude that TNT formation contributes to successful cell-to-cell spread of BoHV-1 and demonstrate for the first time the participation of membrane nanotubes in intercellular transfer of a herpesvirus in live cells.IMPORTANCE Efficient transmission of viral particles between cells is an important factor in successful infection by herpesviruses. Herpesviruses can spread by the free-entry mode or direct cell-to-cell transfer via cell junctions and long extensions of neuronal cells. In this report, we show for the first time that an alphaherpesvirus can also spread between various types of cells using tunneling nanotubes, intercellular connections that are utilized by HIV and other viruses. Live-cell monitoring revealed that viral transmission occurs between the cells of the same type as well as between epithelial cells and fibroblasts. This newly discovered route of herpesviruses spread may contribute to efficient transmission despite the presence of host immune responses, especially after reactivation from latency that developed after primary infection. Long-range communication provided by TNTs may facilitate the spread of herpesviruses between many tissues and organs of an infected organism.
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/29/2017] [Indexed: 09/29/2023] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus before they are translocated to the perinuclear space by budding, acquiring tegument and envelope, or releasing to the cytoplasm in a "naked" state via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" are essential steps for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of an alternative exit route. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols that lead to improved spatial and temporal resolution. Results: Scanning electron microscopy showed the Golgi complex as a compact entity in a juxtanuclear position covered by a membrane on the cis face. Transmission electron microscopy revealed that Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data strongly suggest that virions are intraluminally transported from the perinuclear space via Golgi complex-endoplasmic reticulum transitions into Golgi cisternae for packaging into transport vacuoles. Furthermore, virions derived by budding at nuclear membranes are infective as has been shown for HSV-1 Us3 deletion mutants, which almost entirely accumulate in the perinuclear space. Therefore, de-envelopment followed by re-envelopment is not essential for production of infective progeny virus.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/19/2018] [Indexed: 11/23/2022] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus, translocated to the perinuclear space by budding, acquiring tegument and envelope, or released to the cytoplasm via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" is essential for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of alternative exit routes. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols. Results: The Golgi complex is a compact entity in a juxtanuclear position covered by a membrane on the cis face. Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data suggest that virions derived by budding at nuclear membranes are intraluminally transported from the perinuclear space via Golgi -endoplasmic reticulum transitions into Golgi cisternae for packaging. Virions derived by budding at nuclear membranes are infective like Us3 deletion mutants, which accumulate in the perinuclear space. Therefore, i) de-envelopment followed by re-envelopment is not essential for production of infective progeny virus, ii) the process taking place at the outer nuclear membrane is budding not fusion, and iii) naked capsids gain access to the cytoplasmic matrix via impaired nuclear envelope as reported earlier.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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Roller RJ, Baines JD. Herpesvirus Nuclear Egress. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2017; 223:143-169. [PMID: 28528443 DOI: 10.1007/978-3-319-53168-7_7] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Herpesviruses assemble and package their genomes into capsids in the nucleus, but complete final assembly of the mature virion in the cell cytoplasm. This requires passage of the genome-containing capsid across the double-membrane nuclear envelope. Herpesviruses have evolved a mechanism that relies on a pair of conserved viral gene products to shuttle the capsids from the nucleus to the cytoplasm by way of envelopment and de-envelopment at the inner and outer nuclear membranes, respectively. This complex process requires orchestration of the activities of viral and cellular factors to alter the architecture of the nuclear membrane, select capsids at the appropriate stage for egress, and accomplish efficient membrane budding and fusion events. The last few years have seen major advances in our understanding of the membrane budding mechanism and helped clarify the roles of viral and cellular proteins in the other, more mysterious steps. Here, we summarize and place into context this recent research and, hopefully, clarify both the major advances and major gaps in our understanding.
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Affiliation(s)
- Richard J Roller
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Joel D Baines
- Kenneth F. Burns Chair in Veterinary Medicine, School of Veterinary Medicine, Skip Bertman Drive, Louisiana State University, Baton Rouge, LA, USA.
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Hellberg T, Paßvogel L, Schulz KS, Klupp BG, Mettenleiter TC. Nuclear Egress of Herpesviruses: The Prototypic Vesicular Nucleocytoplasmic Transport. Adv Virus Res 2016; 94:81-140. [PMID: 26997591 DOI: 10.1016/bs.aivir.2015.10.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Herpesvirus particles mature in two different cellular compartments. While capsid assembly and packaging of the genomic linear double-stranded DNA occur in the nucleus, virion formation takes place in the cytoplasm by the addition of numerous tegument proteins as well as acquisition of the viral envelope by budding into cellular vesicles derived from the trans-Golgi network containing virally encoded glycoproteins. To gain access to the final maturation compartment, herpesvirus nucleocapsids have to cross a formidable barrier, the nuclear envelope (NE). Since the ca. 120 nm diameter capsids are unable to traverse via nuclear pores, herpesviruses employ a vesicular transport through both leaflets of the NE. This process involves proteins which support local dissolution of the nuclear lamina to allow access of capsids to the inner nuclear membrane (INM), drive vesicle formation from the INM and mediate inclusion of the capsid as well as scission of the capsid-containing vesicle (also designated as "primary virion"). Fusion of the vesicle membrane (i.e., the "primary envelope") with the outer nuclear membrane subsequently results in release of the nucleocapsid into the cytoplasm for continuing virion morphogenesis. While this process has long been thought to be unique for herpesviruses, a similar pathway for nuclear egress of macromolecular complexes has recently been observed in Drosophila. Thus, herpesviruses may have coopted a hitherto unrecognized cellular mechanism of vesicle-mediated nucleocytoplasmic transport. This could have far reaching consequences for our understanding of cellular functions as again unraveled by the study of viruses.
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Affiliation(s)
- Teresa Hellberg
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Lars Paßvogel
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Katharina S Schulz
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany.
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16
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Pires de Mello CP, Bloom DC, Paixão IC. Herpes simplex virus type-1: replication, latency, reactivation and its antiviral targets. Antivir Ther 2016; 21:277-86. [PMID: 26726828 DOI: 10.3851/imp3018] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2015] [Indexed: 10/22/2022]
Abstract
Infection by herpes simplex virus type-1 (HSV-1) causes several diseases, ranging from cutaneous, oral and genital infections to fatal encephalitis. Despite the availability of antiviral therapies on the market, their efficacies are incomplete, and new cases of resistant strains arise, mainly in the immunocompromised, but also recently documented in immunocompetent patients. Over the last decades a lot has been discovered about the molecular basis of infection which has been of great benefit to the investigation of new anti-HSV-1 molecules. In this review we summarize replication, latency and reactivation highlighting potential antiviral targets and new molecules described in the past several years in the literature.
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Affiliation(s)
- Camilly P Pires de Mello
- Department of Cellular and Molecular Biology, Universidade Federal Fluminense, Biology Institute, Niterói, Brazil
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17
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3D Analysis of HCMV Induced-Nuclear Membrane Structures by FIB/SEM Tomography: Insight into an Unprecedented Membrane Morphology. Viruses 2015; 7:5686-704. [PMID: 26556360 PMCID: PMC4664973 DOI: 10.3390/v7112900] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 10/22/2015] [Accepted: 10/26/2015] [Indexed: 01/04/2023] Open
Abstract
We show that focused ion beam/scanning electron microscopy (FIB/SEM) tomography is an excellent method to analyze the three-dimensional structure of a fibroblast nucleus infected with human cytomegalovirus (HCMV). We found that the previously described infoldings of the inner nuclear membrane, which are unique among its kind, form an extremely complex network of membrane structures not predictable by previous two-dimensional studies. In all cases they contained further invaginations (2nd and 3rd order infoldings). Quantification revealed 5498HCMV capsids within two nuclear segments, allowing an estimate of 15,000 to 30,000 capsids in the entire nucleus five days post infection. Only 0.8% proved to be enveloped capsids which were exclusively detected in 1st order infoldings (perinuclear space). Distribution of the capsids between 1st, 2nd and 3rd order infoldings is in complete agreement with the envelopment/de-envelopment model for egress of HCMV capsids from the nucleus and we confirm that capsid budding does occur at the large infoldings. Based on our results we propose the pushing membrane model: HCMV infection induces local disruption of the nuclear lamina and synthesis of new membrane material which is pushed into the nucleoplasm, forming complex membrane infoldings in a highly abundant manner, which then may be also used by nucleocapsids for budding.
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18
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Schulz KS, Klupp BG, Granzow H, Passvogel L, Mettenleiter TC. Herpesvirus nuclear egress: Pseudorabies Virus can simultaneously induce nuclear envelope breakdown and exit the nucleus via the envelopment-deenvelopment-pathway. Virus Res 2015; 209:76-86. [PMID: 25678269 DOI: 10.1016/j.virusres.2015.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 02/01/2015] [Accepted: 02/02/2015] [Indexed: 12/19/2022]
Abstract
Herpesvirus replication takes place in the nucleus and in the cytosol. After entering the cell, nucleocapsids are transported to nuclear pores where viral DNA is released into the nucleus. After gene expression and DNA replication new nucleocapsids are assembled which have to exit the nucleus for virion formation in the cytosol. Since nuclear pores are not wide enough to allow passage of the nucleocapsid, nuclear egress occurs by vesicle-mediated transport through the nuclear envelope. To this end, nucleocapsids bud at the inner nuclear membrane (INM) recruiting a primary envelope which then fuses with the outer nuclear membrane (ONM). In the absence of this regulated nuclear egress, mutants of the alphaherpesvirus pseudorabies virus have been described that escape from the nucleus after virus-induced nuclear envelope breakdown. Here we review these exit pathways and demonstrate that both can occur simultaneously under appropriate conditions.
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Affiliation(s)
- Katharina S Schulz
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Harald Granzow
- Institute of Infectology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Lars Passvogel
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany.
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19
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Wang Y, Yang Y, Wu S, Pan S, Zhou C, Ma Y, Ru Y, Dong S, He B, Zhang C, Cao Y. p32 is a novel target for viral protein ICP34.5 of herpes simplex virus type 1 and facilitates viral nuclear egress. J Biol Chem 2014; 289:35795-805. [PMID: 25355318 PMCID: PMC4276848 DOI: 10.1074/jbc.m114.603845] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/23/2014] [Indexed: 12/25/2022] Open
Abstract
As a large double-stranded DNA virus, herpes simplex virus type 1 (HSV-1) assembles capsids in the nucleus where the viral particles exit by budding through the inner nuclear membrane. Although a number of viral and host proteins are involved, the machinery of viral egress is not well understood. In a search for host interacting proteins of ICP34.5, which is a virulence factor of HSV-1, we identified a cellular protein, p32 (gC1qR/HABP1), by mass spectrophotometer analysis. When expressed, ICP34.5 associated with p32 in mammalian cells. Upon HSV-1 infection, p32 was recruited to the inner nuclear membrane by ICP34.5, which paralleled the phosphorylation and rearrangement of nuclear lamina. Knockdown of p32 in HSV-1-infected cells significantly reduced the production of cell-free viruses, suggesting that p32 is a mediator of HSV-1 nuclear egress. These observations suggest that the interaction between HSV-1 ICP34.5 and p32 leads to the disintegration of nuclear lamina and facilitates the nuclear egress of HSV-1 particles.
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Affiliation(s)
- Yu Wang
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yin Yang
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Songfang Wu
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Shuang Pan
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Chaodong Zhou
- Department of Biochemistry, Institute for Drug Control, Tianjin 300070, China
| | - Yijie Ma
- Department of Microbiology and Immunology, College of Medicine, University of Illinois, Chicago, Illinois 60612, and
| | - Yongxin Ru
- Department of Electron Microscopy, Institute of Hematology and Blood Diseases Hospital, Peking Union College, Tianjin 300020, China
| | - Shuxu Dong
- Department of Electron Microscopy, Institute of Hematology and Blood Diseases Hospital, Peking Union College, Tianjin 300020, China
| | - Bin He
- Department of Microbiology and Immunology, College of Medicine, University of Illinois, Chicago, Illinois 60612, and
| | - Cuizhu Zhang
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China,
| | - Youjia Cao
- From the Key laboratory of Microbial Functional Genomics of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China,
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21
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Abstract
Marek's disease virus (MDV) is a highly contagious virus that induces T-lymphoma in chicken. This viral infection still circulates in poultry flocks despite the use of vaccines. With the emergence of new virulent strains in the field over time, MDV remains a serious threat to the poultry industry. More than 40 yr after MDV identification as a herpesvirus, the visualization and purification of fully enveloped infectious particles remain a challenge for biologists. The various strategies used to detect such hidden particles by electron microscopy are reviewed herein. It is now generally accepted that the production of cell-free virions only occurs in the feather follicle epithelium and is associated with viral, cellular, or both molecular determinants expressed in this tissue. This tissue is considered the only source of efficient virus shedding into the environment and therefore the origin of successful transmission in birds. In other avian tissues or permissive cell cultures, MDV replication only leads to a very low number of intracellular enveloped virions. In the absence of detectable extracellular enveloped virions in cell culture, the nature of the transmitted infectious material and its mechanisms of spread from cell to cell remain to be deciphered. An attempt is made to bring together the current knowledge on MDV morphogenesis and spread, and new approaches that could help understand MDV morphogenesis are discussed.
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Affiliation(s)
- Caroline Denesvre
- INRA, UMR1282, Infectious Diseases and Public Health, ISP, BIOVA team, F-37380 Nouzilly, France.
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22
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Wild P, de Oliveira AP, Sonda S, Schraner EM, Ackermann M, Tobler K. The herpes simplex virus 1 U(S)3 regulates phospholipid synthesis. Virology 2012; 432:353-60. [PMID: 22789738 DOI: 10.1016/j.virol.2012.06.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 05/07/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
Herpes simplex virus type 1 capsids bud at nuclear and Golgi membranes for envelopment by phospholipid bilayers. In the absence of U(S)3, nuclear membranes form multiple folds harboring virions that suggests disturbance in membrane turnover. Therefore, we investigated phospholipid metabolism in cells infected with the U(S)3 deletion mutant R7041(ΔU(S)3), and quantified membranes involved in viral envelopment. We report that (i) [(3)H]-choline incorporation into nuclear membranes and cytoplasmic membranes was enhanced peaking at 12 or 20 h post inoculation with wild type HSV-1 and R7041(ΔU(S)3), respectively, (ii) the surface area of nuclear membranes increased until 24 h of R7041(ΔU(S)3) infection forming folds that equaled ~45% of the nuclear surface, (iii) the surface area of viral envelopes between nuclear membranes equaled ~2400 R7041(ΔU(S)3) virions per cell, and (iv) during R7041(ΔU(S)3) infection, the Golgi complex expanded dramatically. The data indicate that U(S)3 plays a significant role in regulation of membrane biosynthesis.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, University of Zürich, Switzerland.
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Antiviral effect of HPMPC (Cidofovir®), entrapped in cationic liposomes: In vitro study on MDBK cell and BHV-1 virus. J Control Release 2012; 160:330-8. [DOI: 10.1016/j.jconrel.2012.01.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 01/25/2012] [Accepted: 01/27/2012] [Indexed: 11/19/2022]
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Analysis of viral and cellular factors influencing herpesvirus-induced nuclear envelope breakdown. J Virol 2012; 86:6512-21. [PMID: 22491460 DOI: 10.1128/jvi.00068-12] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Herpesvirus nucleocapsids are translocated from their assembly site in the nucleus to the cytosol by acquisition of a primary envelope at the inner nuclear membrane which subsequently fuses with the outer nuclear membrane. This transport through the nuclear envelope requires homologs of the conserved herpesviral pUL31 and pUL34 proteins which form the nuclear egress complex (NEC). In its absence, 1,000-fold less virus progeny is produced. We isolated a UL34-negative mutant of the alphaherpesvirus pseudorabies virus (PrV), PrV-ΔUL34Pass, which regained replication competence after serial passages in cell culture by inducing nuclear envelope breakdown (NEBD) (B. G. Klupp, H. Granzow, and T. C. Mettenleiter, J. Virol. 85:8285-8292, 2011). To test whether this phenotype is unique, passaging experiments were repeated with a UL31 deletion mutant. After 60 passages, the resulting PrV-ΔUL31Pass replicated similarly to wild-type PrV. Ultrastructural analyses confirmed escape from the nucleus via NEBD, indicating an inherent genetic disposition in herpesviruses. To identify the mutated viral genes responsible for this phenotype, the genome of PrV-ΔUL34Pass was sequenced and compared to the genomes of parental PrV-Ka and PrV-ΔUL34. Targeted sequencing of PrV-ΔUL31Pass disclosed congruent mutations comprising genes encoding tegument proteins (pUL49, pUL46, pUL21, pUS2), envelope proteins (gI, pUS9), and protease pUL26. To investigate involvement of cellular pathways, different inhibitors of cellular kinases were tested. While induction of apoptosis or inhibition of caspases had no specific effect on the passaged mutants, roscovitine, a cyclin-dependent kinase inhibitor, and U0126, an inhibitor of MEK1/2, specifically impaired replication of the passaged mutants, indicating involvement of mitosis-related processes in herpesvirus-induced NEBD.
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Sobol MA, Philimonenko VV, Philimonenko AA, Hozák P. Quantitative evaluation of freeze-substitution effects on preservation of nuclear antigens during preparation of biological samples for immunoelectron microscopy. Histochem Cell Biol 2012; 138:167-77. [DOI: 10.1007/s00418-012-0931-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2012] [Indexed: 10/28/2022]
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Rémillard-Labrosse G, Lippé R. In vitro nuclear egress of herpes simplex virus type 1 capsids. Methods 2011; 55:153-9. [PMID: 21824520 DOI: 10.1016/j.ymeth.2011.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 07/18/2011] [Accepted: 07/20/2011] [Indexed: 11/24/2022] Open
Abstract
During their life cycles, viruses typically undergo many transport events throughout the cell. These events depend on a variety of both viral and host proteins and are often not fully understood. Such studies are often complicated by asynchronous infections and the concurrent presence of various viral intermediates in the cells, making it difficult to molecularly define each step. In the case of the herpes simplex virus type 1, the etiological agent of cold sores and many other illnesses, the viral particles undergo an intricate series of transport steps during its life cycle. Upon entry by fusion with a cellular membrane, they travel to the host cell nucleus where the virus replicates and assembles new viral particles. These particles then travel across the two nuclear envelopes and transit through the trans-Golgi network before finally being transported to and released at the cell surface. Though viral components and some host proteins modulating these numerous transport events have been identified, the details of these processes remain to be elucidated. To specifically address how the virus escapes the nucleus, we set up an in vitro model that reproduces the unconventional route used by herpes simplex type 1 virus to leave nuclei. This has not only allowed us to clarify the route of capsid egress of the virus but is now useful to define it at the molecular level.
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Affiliation(s)
- Gaudeline Rémillard-Labrosse
- Department of Pathology and Cell Biology, University of Montreal, PO Box 6128, Succursale Centre-Ville, Montreal, Quebec, Canada H3C 3J7
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Herpesviruses and intermediate filaments: close encounters with the third type. Viruses 2011; 3:1015-40. [PMID: 21994768 PMCID: PMC3185793 DOI: 10.3390/v3071015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 06/07/2011] [Accepted: 06/24/2011] [Indexed: 01/29/2023] Open
Abstract
Intermediate filaments (IF) are essential to maintain cellular and nuclear integrity and shape, to manage organelle distribution and motility, to control the trafficking and pH of intracellular vesicles, to prevent stress-induced cell death, and to support the correct distribution of specific proteins. Because of this, IF are likely to be targeted by a variety of pathogens, and may act in favor or against infection progress. As many IF functions remain to be identified, however, little is currently known about these interactions. Herpesviruses can infect a wide variety of cell types, and are thus bound to encounter the different types of IF expressed in each tissue. The analysis of these interrelationships can yield precious insights into how IF proteins work, and into how viruses have evolved to exploit these functions. These interactions, either known or potential, will be the focus of this review.
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Nuclear envelope breakdown can substitute for primary envelopment-mediated nuclear egress of herpesviruses. J Virol 2011; 85:8285-92. [PMID: 21680518 DOI: 10.1128/jvi.00741-11] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Herpesvirus nucleocapsids assemble in the nucleus but mature to infectious virions in the cytoplasm. To gain access to this cellular compartment, nucleocapsids are translocated to the cytoplasm by primary envelopment at the inner nuclear membrane and subsequent fusion of the primary envelope with the outer nuclear membrane. The conserved viral pUL34 and pUL31 proteins play a crucial role in this process. In their absence, viral replication is strongly impaired but not totally abolished. We used the residual infectivity of a pUL34-deleted mutant of the alphaherpesvirus pseudorabies virus (PrV) for reversion analysis. To this end, PrV-ΔUL34 was serially passaged in rabbit kidney cells until final titers of the mutant virus PrV-ΔUL34Pass were comparable to those of wild-type PrV. PrV-ΔUL34Pass produced infectious progeny independently of the pUL34/pUL31 nuclear egress complex and the pUS3 protein kinase. Ultrastructural analyses demonstrated that this effect was due to virus-induced disintegration of the nuclear envelope, thereby releasing immature and mature capsids into the cytosol for secondary envelopment. Our data indicate that nuclear egress primarily serves to transfer capsids through the intact nuclear envelope. Immature and mature intranuclear capsids are competent for further virion maturation once they reach the cytoplasm. However, nuclear egress exhibits a strong bias for nucleocapsids, thereby also functioning as a quality control checkpoint which is abolished by herpesvirus-induced nuclear envelope breakdown.
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29
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Bucks MA, Murphy MA, O'Regan KJ, Courtney RJ. Identification of interaction domains within the UL37 tegument protein of herpes simplex virus type 1. Virology 2011; 416:42-53. [PMID: 21601231 DOI: 10.1016/j.virol.2011.04.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 01/03/2011] [Accepted: 04/26/2011] [Indexed: 12/16/2022]
Abstract
Herpes simplex virus type 1 (HSV-1) UL37 is a 1123 amino acid tegument protein that self-associates and binds to the tegument protein UL36 (VP1/2). Studies were undertaken to identify regions of UL37 involved in these protein-protein interactions. Coimmunoprecipitation assays showed that residues within the carboxy-terminal half of UL37, amino acids 568-1123, are important for interaction with UL36. Coimmunoprecipitation assays also revealed that amino acids 1-300 and 568-1123 of UL37 are capable of self-association. UL37 appears to self-associate only under conditions when UL36 is not present or is present in low amounts, suggesting UL36 and UL37 may compete for binding. Transfection-infection experiments were performed to identify domains of UL37 that complement the UL37 deletion virus, K∆UL37. The carboxy-terminal region of UL37 (residues 568-1123) partially rescues the K∆UL37 infection. These results suggest the C-terminus of UL37 may contribute to its essential functional role within the virus-infected cell.
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Affiliation(s)
- Michelle A Bucks
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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30
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Guo H, Shen S, Wang L, Deng H. Role of tegument proteins in herpesvirus assembly and egress. Protein Cell 2010; 1:987-98. [PMID: 21153516 DOI: 10.1007/s13238-010-0120-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022] Open
Abstract
Morphogenesis and maturation of viral particles is an essential step of viral replication. An infectious herpesviral particle has a multilayered architecture, and contains a large DNA genome, a capsid shell, a tegument and an envelope spiked with glycoproteins. Unique to herpesviruses, tegument is a structure that occupies the space between the nucleocapsid and the envelope and contains many virus encoded proteins called tegument proteins. Historically the tegument has been described as an amorphous structure, but increasing evidence supports the notion that there is an ordered addition of tegument during virion assembly, which is consistent with the important roles of tegument proteins in the assembly and egress of herpesviral particles. In this review we first give an overview of the herpesvirus assembly and egress process. We then discuss the roles of selected tegument proteins in each step of the process, i.e., primary envelopment, de-envelopment, secondary envelopment and transport of viral particles. We also suggest key issues that should be addressed in the near future.
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Affiliation(s)
- Haitao Guo
- CAS Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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31
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Myosin Va enhances secretion of herpes simplex virus 1 virions and cell surface expression of viral glycoproteins. J Virol 2010; 84:9889-96. [PMID: 20631136 DOI: 10.1128/jvi.00732-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The final step in the egress of herpes simplex virus (HSV) virions requires virion-laden vesicles to bypass cortical actin and fuse with the plasma membrane, releasing virions into the extracellular space. Little is known about the host or viral proteins involved. In the current study, we noted that the conformation of myosin Va (myoVa), a protein known to be involved in melanosome and secretory granule trafficking to the plasma membrane in melanocytes and neuroendocrine cells, respectively, was altered by 4 h after infection with HSV-1 such that an N-terminal epitope expected to be masked in its inactive state was rendered immunoreactive. Wild-type myoVa localized throughout the cytoplasm and to a limited extent in the nuclei of HSV-infected cells. Two different dominant negative myoVa molecules containing cargo-binding domains but lacking the lever arms and actin-binding domains colocalized with markers of the trans-Golgi network (TGN). Expression of dominant negative myoVa isoforms reduced secretion of HSV-1 infectivity into the medium by 50 to 75%, reduced surface expression of glycoproteins B, M, and D, and increased intracellular virus infectivity to levels consistent with increased retention of virions in the cytoplasm. These data suggest that myoVa is activated during HSV-1 infection to help transport virion- and glycoprotein-laden vesicles from the TGN, through the cortical actin, to the plasma membrane. We cannot exclude a role for myoVa in promoting fusion of these vesicles with the inner surface of the plasma membrane. These data also indicate that myoVa is involved in exocytosis in human epithelial cells as well as other cell types.
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32
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de Oliveira AP, Fraefel C. Herpes simplex virus type 1/adeno-associated virus hybrid vectors. Open Virol J 2010; 4:109-22. [PMID: 20811580 PMCID: PMC2930156 DOI: 10.2174/1874357901004030109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Revised: 01/12/2010] [Accepted: 01/13/2010] [Indexed: 11/22/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) amplicons can accommodate foreign DNA of any size up to 150 kbp and, therefore, allow extensive combinations of genetic elements. Genomic sequences as well as cDNA, large transcriptional regulatory sequences for cell type-specific expression, multiple transgenes, and genetic elements from other viruses to create hybrid vectors may be inserted in a modular fashion. Hybrid amplicons use genetic elements from HSV-1 that allow replication and packaging of the vector DNA into HSV-1 virions, and genetic elements from other viruses that either direct integration of transgene sequences into the host genome or allow episomal maintenance of the vector. Thus, the advantages of the HSV-1 amplicon system, including large transgene capacity, broad host range, strong nuclear localization, and availability of helper virus-free packaging systems are retained and combined with those of heterologous viral elements that confer genetic stability to the vector DNA. Adeno-associated virus (AAV) has the unique capability of integrating its genome into a specific site, designated AAVS1, on human chromosome 19. The AAV rep gene and the inverted terminal repeats (ITRs) that flank the AAV genome are sufficient for this process. HSV-1 amplicons have thus been designed that contain the rep gene and a transgene cassette flanked by AAV ITRs. These HSV/AAV hybrid vectors direct site-specific integration of transgene sequences into AAVS1 and support long-term transgene expression.
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Affiliation(s)
| | - Cornel Fraefel
- Institute of Virology, University of Zurich, Zurich, Switzerland
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33
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Steiner F, Zumsteg A, Vogt B, Ackermann M, Schwyzer M. Bovine herpesvirus 5 BICP0 complements the bovine herpesvirus 1 homolog. Vet Microbiol 2010; 143:37-44. [DOI: 10.1016/j.vetmic.2010.02.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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34
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Shlapobersky M, Sinyakov MS, Katzenellenbogen M, Sarid R, Don J, Avtalion RR. Viral encephalitis of tilapia larvae: Primary characterization of a novel herpes-like virus. Virology 2010; 399:239-47. [DOI: 10.1016/j.virol.2010.01.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 12/23/2009] [Accepted: 01/04/2010] [Indexed: 11/28/2022]
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35
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Sagou K, Uema M, Kawaguchi Y. Nucleolin is required for efficient nuclear egress of herpes simplex virus type 1 nucleocapsids. J Virol 2010; 84:2110-21. [PMID: 19955312 PMCID: PMC2812367 DOI: 10.1128/jvi.02007-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 11/20/2009] [Indexed: 12/15/2022] Open
Abstract
Herpesvirus nucleocapsids assemble in the nucleus and must cross the nuclear membrane for final assembly and maturation to form infectious progeny virions in the cytoplasm. It has been proposed that nucleocapsids enter the perinuclear space by budding through the inner nuclear membrane, and these enveloped nucleocapsids then fuse with the outer nuclear membrane to enter the cytoplasm. Little is known about the mechanism(s) for nuclear egress of herpesvirus nucleocapsids and, in particular, which, if any, cellular proteins are involved in the nuclear egress pathway. UL12 is an alkaline nuclease encoded by herpes simplex virus type 1 (HSV-1) and has been suggested to be involved in viral DNA maturation and nuclear egress of nucleocapsids. Using a live-cell imaging system to study cells infected by a recombinant HSV-1 expressing UL12 fused to a fluorescent protein, we observed the previously unreported nucleolar localization of UL12 in live infected cells and, using coimmunoprecipitation analyses, showed that UL12 formed a complex with nucleolin, a nucleolus marker, in infected cells. Knockdown of nucleolin in HSV-1-infected cells reduced capsid accumulation, as well as the amount of viral DNA resistant to staphylococcal nuclease in the cytoplasm, which represented encapsidated viral DNA, but had little effect on these viral components in the nucleus. These results indicated that nucleolin is a cellular factor required for efficient nuclear egress of HSV-1 nucleocapsids in infected cells.
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Affiliation(s)
- Ken Sagou
- Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Nippon Institute for Biological Science, Ome, Tokyo 198-0024, Japan
| | - Masashi Uema
- Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Nippon Institute for Biological Science, Ome, Tokyo 198-0024, Japan
| | - Yasushi Kawaguchi
- Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Nippon Institute for Biological Science, Ome, Tokyo 198-0024, Japan
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36
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Lobanov VA, Zheng C, Babiuk LA, van Drunen Littel-van den Hurk S. Intracellular trafficking of VP22 in bovine herpesvirus-1 infected cells. Virology 2009; 396:189-202. [PMID: 19922972 DOI: 10.1016/j.virol.2009.10.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Revised: 08/05/2009] [Accepted: 10/15/2009] [Indexed: 11/24/2022]
Abstract
The intracellular trafficking of different VP22-enhanced yellow fluorescent protein (EYFP) fusion proteins expressed by bovine herpesvirus-1 (BHV-1) recombinants was examined by live-cell imaging. Our results demonstrate that (i) the fusion of EYFP to the C terminus of VP22 does not alter the trafficking of the protein in infected cells, (ii) VP22 expressed during BHV-1 infection translocates to the nucleus through three different pathways, namely early mitosis-dependent nuclear translocation, late massive nuclear translocation that follows a prolonged cytoplasmic stage of the protein in non-mitotic cells, and accumulation of a small subset of VP22 in discrete dot-like nuclear domains during its early cytoplasmic stage, (iii) the addition of the SV40 large-T-antigen nuclear localization signal (NLS) to VP22-EYFP abrogates its early cytoplasmic stage, and (iv) the VP22 (131)PRPR(134) NLS is not required for the late massive nuclear translocation of the protein, but this motif is essential for the targeting of VP22 to discrete dot-like nuclear domains during the early cytoplasmic stage. These results show that the amount of VP22 in the nucleus is precisely regulated at different stages of BHV-1 infection and suggest that the early pathways of VP22 nuclear accumulation may be more relevant to the infection process as the late massive nuclear influx starts when most of the viral progeny has already emerged from the cell.
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Affiliation(s)
- Vladislav A Lobanov
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada
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37
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Kelly BJ, Fraefel C, Cunningham AL, Diefenbach RJ. Functional roles of the tegument proteins of herpes simplex virus type 1. Virus Res 2009; 145:173-86. [PMID: 19615419 DOI: 10.1016/j.virusres.2009.07.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2009] [Revised: 07/07/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
Abstract
Herpes virions consist of four morphologically distinct structures, a DNA core, capsid, tegument, and envelope. Tegument occupies the space between the nucleocapsid (capsid containing DNA core) and the envelope. A combination of genetic, biochemical and proteomic analysis of alphaherpes virions suggest the tegument contains in the order of 20 viral proteins. Historically the tegument has been described as amorphous but increasing evidence suggests there is an ordered addition of tegument during assembly. This review highlights the diverse roles, in addition to structural, that tegument plays during herpes viral replication using as an example herpes simplex virus type 1. Such diverse roles include: capsid transport during entry and egress; targeting of the capsid to the nucleus; regulation of transcription, translation and apoptosis; DNA replication; immune modulation; cytoskeletal assembly; nuclear egress of capsid; and viral assembly and final egress.
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Affiliation(s)
- Barbara J Kelly
- Centre for Virus Research, The Westmead Millennium Institute, The University of Sydney and Westmead Hospital, Westmead, NSW 2145, Australia
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38
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Mettenleiter TC, Klupp BG, Granzow H. Herpesvirus assembly: an update. Virus Res 2009; 143:222-34. [PMID: 19651457 DOI: 10.1016/j.virusres.2009.03.018] [Citation(s) in RCA: 293] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 03/28/2009] [Accepted: 03/28/2009] [Indexed: 12/30/2022]
Abstract
The order Herpesvirales contains viruses infecting animals from molluscs to men with a common virion morphology which have been classified into the families Herpesviridae, Alloherpesviridae and Malacoherpesviridae. Herpes virions are among the most complex virus particles containing a multitude of viral and cellular proteins which assemble into nucleocapsid, envelope and tegument. After autocatalytic assembly of the capsid and packaging of the newly replicated viral genome, a process which occurs in the nucleus and resembles head formation and genome packaging in the tailed double-stranded DNA bacteriophages, the nucleocapsid is translocated to the cytoplasm by budding at the inner nuclear membrane followed by fusion of the primary envelope with the outer nuclear membrane. Viral and cellular proteins are involved in mediating this 'nuclear egress' which entails substantial remodeling of the nuclear architecture. For final maturation within the cytoplasm tegument components associate with the translocated nucleocapsid, with themselves, and with the future envelope containing viral membrane proteins in a complex network of interactions resulting in the formation of an infectious herpes virion. The diverse interactions between the involved proteins exhibit a striking redundancy which is still insufficiently understood. In this review, recent advances in our understanding of the molecular processes resulting in herpes virion maturation will be presented and discussed as an update of a previous contribution [Mettenleiter, T.C., 2004. Budding events in herpesvirus morphogenesis. Virus Res. 106, 167-180].
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39
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Wild P, Senn C, Manera CL, Sutter E, Schraner EM, Tobler K, Ackermann M, Ziegler U, Lucas MS, Kaech A. Exploring the nuclear envelope of herpes simplex virus 1-infected cells by high-resolution microscopy. J Virol 2009; 83:408-19. [PMID: 18922868 PMCID: PMC2612326 DOI: 10.1128/jvi.01568-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 10/06/2008] [Indexed: 01/11/2023] Open
Abstract
Herpesviruses are composed of capsid, tegument, and envelope. Capsids assemble in the nucleus and exit the nucleus by budding at the inner nuclear membrane, acquiring tegument and the envelope. This study focuses on the changes of the nuclear envelope during herpes simplex virus 1 (HSV-1) infection in HeLa and Vero cells by employing preparation techniques at ambient and low temperatures for high-resolution scanning and transmission electron microscopy and confocal laser scanning microscopy. Cryo-field emission scanning electron microscopy of freeze-fractured cells showed for the first time budding of capsids at the nuclear envelope at the third dimension with high activity at 10 h and low activity at 15 h of incubation. The mean number of pores was significantly lower, and the mean interpore distance and the mean interpore area were significantly larger than those for mock-infected cells 15 h after inoculation. Forty-five percent of nuclear pores in HSV-1-infected cells were dilated to more than 140 nm. Nuclear material containing capsids protrude through them into the cytoplasm. Examination of in situ preparations after dry fracturing revealed significant enlargements of the nuclear pore diameter and of the nuclear pore central channel in HSV-1-infected cells compared to mock-infected cells. The demonstration of nucleoporins by confocal microscopy also revealed fewer pores but focal enhancement of fluorescence signals in HSV-1-infected cells, whereas Western blots showed no loss of nucleoporins from cells. The data suggest that infection with HSV-1 alters the number, size, and architecture of nuclear pores without a loss of nucleoporins from altered nuclear pore complexes.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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40
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41
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Abstract
Electron microscopy is a powerful tool to visualize viruses in diagnostic as well as in research settings for investigating viral structure and virus-cell interactions. Here, a simple but efficient method is described for demonstrating viruses by negative staining, and its limit is discussed. A prerequisite to obtain reliable information on virus-cell interactions is excellent preservation of cellular and viral ultrastructure. The crux is that during fixation and embedding, by applying conventional protocols about 50% of the lipids are lost, which results in loss of integrity of cell membranes. To achieve good preservation of cellular architectures, good contrast, and both high spatial and temporal resolution, methods for freezing, freeze-substitution, and freeze-etching are described and their applicability discussed mostly taking complicated built herpes viruses as examples.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institutes of Veterinary Anatomy and of Virology, University of Zürich, CH-8057 Zürich, Switzerland
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42
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Lee JH, Vittone V, Diefenbach E, Cunningham AL, Diefenbach RJ. Identification of structural protein-protein interactions of herpes simplex virus type 1. Virology 2008; 378:347-54. [PMID: 18602131 DOI: 10.1016/j.virol.2008.05.035] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Revised: 05/18/2008] [Accepted: 05/31/2008] [Indexed: 11/24/2022]
Abstract
In this study we have defined protein-protein interactions between the structural proteins of herpes simplex virus type 1 (HSV-1) using a LexA yeast two-hybrid system. The majority of the capsid, tegument and envelope proteins of HSV-1 were screened in a matrix approach. A total of 40 binary interactions were detected including 9 out of 10 previously identified tegument-tegument interactions (Vittone, V., Diefenbach, E., Triffett, D., Douglas, M.W., Cunningham, A.L., and Diefenbach, R.J., 2005. Determination of interactions between tegument proteins of herpes simplex virus type 1. J. Virol. 79, 9566-9571). A total of 12 interactions involving the capsid protein pUL35 (VP26) and 11 interactions involving the tegument protein pUL46 (VP11/12) were identified. The most significant novel interactions detected in this study, which are likely to play a role in viral assembly, include pUL35-pUL37 (capsid-tegument), pUL46-pUL37 (tegument-tegument) and pUL49 (VP22)-pUS9 (tegument-envelope). This information will provide further insights into the pathways of HSV-1 assembly and the identified interactions are potential targets for new antiviral drugs.
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Affiliation(s)
- Jin H Lee
- Centre for Virus Research, The Westmead Millennium Institute, The University of Sydney and Westmead Hospital, PO Box 412 Westmead, NSW 2145, Australia
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43
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Abstract
The mechanism by which herpes simplex virus (HSV) exits the nucleus remains a matter of controversy. The generally accepted route proposes that capsids exit via primary envelopment at the inner nuclear membrane and subsequent fusion of this primary particle with the outer nuclear membrane to gain capsid entry to the cytoplasm. However, recent observations indicate that HSV may induce gross morphological alterations of nuclear pores, resulting in the loss of normal pores and the appearance of dilated gaps in the nuclear membrane of up to several 100 nm. On this basis, it was proposed that a main route of capsid exit from the nucleus is directly through these altered pores. Here, we examine the biochemical composition of some of the major nuclear pore components in uninfected and HSV-infected cells. We show that total levels of major nucleoporins and their sedimentation patterns in density gradients remain largely unchanged up to 18 h after HSV infection. Some alteration in modification of one nucleoporin, Nup358/RanBP2, was observed during enrichment with anti-nucleoporin antibody and probing for O glycosylation. In addition, we examine functional gating within the nucleus in live cells, using microinjection of labeled dextran beads and a recombinant virus expressing GFP-VP16 to track the progress of infection. The nuclear permeability barrier for molecules bigger than 70 kDa remained intact throughout infection. Thus, in a functional assay in live cells, we find no evidence for gross perturbation to the gating of nuclear pores, although this might not exclude a small population of modified pores.
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44
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Identification of a highly conserved, functional nuclear localization signal within the N-terminal region of herpes simplex virus type 1 VP1-2 tegument protein. J Virol 2008; 82:5234-44. [PMID: 18385239 DOI: 10.1128/jvi.02497-07] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
VP1-2 is a large structural protein assembled into the tegument compartment of the virion, conserved across the herpesviridae, and essential for virus replication. In herpes simplex virus (HSV) and pseudorabies virus, VP1-2 is tightly associated with the capsid. Studies of its assembly and function remain incomplete, although recent data indicate that in HSV, VP1-2 is recruited onto capsids in the nucleus, with this being required for subsequent recruitment of additional structural proteins. Here we have developed an antibody to characterize VP1-2 localization, observing the protein in both cytoplasmic and nuclear compartments, frequently in clusters in both locations. Within the nucleus, a subpopulation of VP1-2 colocalized with VP26 and VP5, though VP1-2-positive foci devoid of these components were observed. We note a highly conserved basic motif adjacent to the previously identified N-terminal ubiquitin hydrolase domain (DUB). The DUB domain in isolation exhibited no specific localization, but when extended to include the adjacent motif, it efficiently accumulated in the nucleus. Transfer of the isolated motif to a test protein, beta-galactosidase, conferred specific nuclear localization. Substitution of a single amino acid within the motif abolished the nuclear localization function. Deletion of the motif from intact VP1-2 abrogated its nuclear localization. Moreover, in a functional assay examining the ability of VP1-2 to complement growth of a VP1-2-ve mutant, deletion of the nuclear localization signal abolished complementation. The nuclear localization signal may be involved in transport of VP1-2 early in infection or to late assembly sites within the nucleus or, considering the potential existence of VP1-2 cleavage products, in selective localization of subdomains to different compartments.
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45
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Simultaneous tracking of capsid, tegument, and envelope protein localization in living cells infected with triply fluorescent herpes simplex virus 1. J Virol 2008; 82:5198-211. [PMID: 18353954 DOI: 10.1128/jvi.02681-07] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report here the construction of a triply fluorescent-tagged herpes simplex virus 1 (HSV-1) expressing capsid protein VP26, tegument protein VP22, and envelope protein gB as fusion proteins with monomeric yellow, red, and cyan fluorescent proteins, respectively. The recombinant virus enabled us to monitor the dynamics of these capsid, tegument, and envelope proteins simultaneously in the same live HSV-1-infected cells and to visualize single extracellular virions with three different fluorescent emissions. In Vero cells infected by the triply fluorescent virus, multiple cytoplasmic compartments were found to be induced close to the basal surfaces of the infected cells (the adhesion surfaces of the infected cells on the solid growth substrate). Major capsid, tegument, and envelope proteins accumulated and colocalized in the compartments, as did marker proteins for the trans-Golgi network (TGN) which has been implicated to be the site of HSV-1 secondary envelopment. Moreover, formation of the compartments was correlated with the dynamic redistribution of the TGN proteins induced by HSV-1 infection. These results suggest that HSV-1 infection causes redistribution of TGN membranes to form multiple cytoplasmic compartments, possibly for optimal secondary envelopment. This is the first real evidence for the assembly of all three types of herpesvirus proteins-capsid, tegument, and envelope membrane proteins-in TGN.
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46
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Nuclear egress and envelopment of herpes simplex virus capsids analyzed with dual-color fluorescence HSV1(17+). J Virol 2007; 82:3109-24. [PMID: 18160444 DOI: 10.1128/jvi.02124-07] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
To analyze the assembly of herpes simplex virus type 1 (HSV1) by triple-label fluorescence microscopy, we generated a bacterial artificial chromosome (BAC) and inserted eukaryotic Cre recombinase, as well as beta-galactosidase expression cassettes. When the BAC pHSV1(17(+))blueLox was transfected back into eukaryotic cells, the Cre recombinase excised the BAC sequences, which had been flanked with loxP sites, from the viral genome, leading to HSV1(17(+))blueLox. We then tagged the capsid protein VP26 and the envelope protein glycoprotein D (gD) with fluorescent protein domains to obtain HSV1(17(+))blueLox-GFPVP26-gDRFP and -RFPVP26-gDGFP. All HSV1 BACs had variations in the a-sequences and lost the oriL but were fully infectious. The tagged proteins behaved as their corresponding wild type, and were incorporated into virions. Fluorescent gD first accumulated in cytoplasmic membranes but was later also detected in the endoplasmic reticulum and the plasma membrane. Initially, cytoplasmic capsids did not colocalize with viral glycoproteins, indicating that they were naked, cytosolic capsids. As the infection progressed, they were enveloped and colocalized with the viral membrane proteins. We then analyzed the subcellular distribution of capsids, envelope proteins, and nuclear pores during a synchronous infection. Although the nuclear pore network had changed in ca. 20% of the cells, an HSV1-induced reorganization of the nuclear pore architecture was not required for efficient nuclear egress of capsids. Our data are consistent with an HSV1 assembly model involving primary envelopment of nuclear capsids at the inner nuclear membrane and primary fusion to transfer capsids into the cytosol, followed by their secondary envelopment on cytoplasmic membranes.
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47
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Denesvre C, Blondeau C, Lemesle M, Le Vern Y, Vautherot D, Roingeard P, Vautherot JF. Morphogenesis of a highly replicative EGFPVP22 recombinant Marek's disease virus in cell culture. J Virol 2007; 81:12348-59. [PMID: 17855520 PMCID: PMC2168996 DOI: 10.1128/jvi.01177-07] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Marek's disease virus (MDV) is an alphaherpesvirus for which infection is strictly cell associated in permissive cell culture systems. In contrast to most other alphaherpesviruses, no comprehensive ultrastructural study has been published to date describing the different stages of MDV morphogenesis. To circumvent problems linked to nonsynchronized infection and low infectivity titers, we generated a recombinant MDV expressing an enhanced green fluorescent protein fused to VP22, a major tegument protein that is not implicated in virion morphogenesis. Growth of this recombinant virus in cell culture was decreased threefold compared to that of the parental Bac20 virus, but this mutant was still highly replicative. The recombinant virus allowed us to select infected cells by cell-sorting cytometry at late stages of infection for subsequent transmission electron microscopy analysis. Under these conditions, all of the stages of assembly and virion morphogenesis could be observed except extracellular enveloped virions, even at the cell surface. We observed 10-fold fewer naked cytoplasmic capsids than nuclear capsids, and intracellular enveloped virions were very rare. The partial envelopment of capsids in the cytoplasm supports the hypothesis of the acquisition of the final envelope in this cellular compartment. We demonstrate for the first time that, compared to other alphaherpesviruses, MDV seems deficient in three crucial steps of viral morphogenesis, i.e., release from the nucleus, secondary envelopment, and the exocytosis process. The discrepancy between the efficiency with which this MDV mutant spreads in cell culture and the relatively inefficient process of its envelopment and virion release raises the question of the MDV cell-to-cell spreading mechanism.
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Affiliation(s)
- C Denesvre
- Laboratoire Virologie Moléculaire, INRA, UR1282, Infectiologie Animale et Santé Publique, IASP, Nouzilly, France.
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48
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Mijatov B, Cunningham AL, Diefenbach RJ. Residues F593 and E596 of HSV-1 tegument protein pUL36 (VP1/2) mediate binding of tegument protein pUL37. Virology 2007; 368:26-31. [PMID: 17651773 DOI: 10.1016/j.virol.2007.07.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 04/10/2007] [Accepted: 07/03/2007] [Indexed: 11/29/2022]
Abstract
The herpes simplex virus type 1 (HSV-1) structural tegument proteins pUL36 (VP1/2) and pUL37 are essential for secondary envelopment during the egress of viral particles. Our laboratory has previously shown that HSV-1 pUL36(512-767) fragment interacts with full-length pUL37. A number of single and double amino acid changes of conserved residues in the pUL36(512-767) fragment were generated using alanine-scanning site-directed mutagenesis. The interaction of pUL36(512-767) and pUL37 was then assessed using a combination of yeast two-hybrid and coimmunoprecipitation assays. Single changes to alanine of pUL36 residues F593 and E596 impaired binding of pUL37 with the greatest effect observed for the substitution E596A. Double mutations involving either of these residues in combination with the substitution E580A essentially blocked binding of pUL37. This information will provide the basis for generation of viral mutants to further define the importance of the pUL36/pUL37 interaction in assembly of HSV-1.
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Affiliation(s)
- Branka Mijatov
- Centre For Virus Research, The Westmead Millennium Institute, The University of Sydney and Westmead Hospital, PO Box 412, Westmead, NSW 2145, Australia
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49
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Hawes P, Netherton CL, Mueller M, Wileman T, Monaghan P. Rapid freeze-substitution preserves membranes in high-pressure frozen tissue culture cells. J Microsc 2007; 226:182-9. [PMID: 17444947 DOI: 10.1111/j.1365-2818.2007.01767.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe a method for high-pressure freezing and rapid freeze-substitution of cells in tissue culture which provides excellent preservation of membrane detail with negligible ice segregation artefacts. Cells grown on sapphire discs were placed 'face to face' without removal of tissue culture medium and frozen without the protection of aluminium planchettes. This reduction in thermal load of the sample/holder combination resulted in freezing of cells without visible ice-crystal artefact. Freeze-substitution at -90 degrees C for 60 min in acetone containing 2% uranyl acetate, followed by warming to -50 degrees C and embedding in Lowicryl HM20 gave consistent and clear membrane detail even when imaged without section contrasting. Preliminary data indicates that the high intrinsic contrast of samples prepared in this way will be valuable for tomographic studies. Immunolabelling sensitivity of sections of samples prepared by this rapid substitution technique was poor; however, reducing the uranyl acetate concentration in the substitution medium to 0.2% resulted in improved labelling. Samples substituted in this lower concentration of uranyl acetate also gave good membrane detail when imaged after section contrasting.
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Affiliation(s)
- P Hawes
- Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK
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50
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Farnsworth A, Wisner TW, Webb M, Roller R, Cohen G, Eisenberg R, Johnson DC. Herpes simplex virus glycoproteins gB and gH function in fusion between the virion envelope and the outer nuclear membrane. Proc Natl Acad Sci U S A 2007; 104:10187-92. [PMID: 17548810 PMCID: PMC1891206 DOI: 10.1073/pnas.0703790104] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Herpesviruses must traverse the nuclear envelope to gain access to the cytoplasm and, ultimately, to exit cells. It is believed that herpesvirus nucleocapsids enter the perinuclear space by budding through the inner nuclear membrane (NM). To reach the cytoplasm these enveloped particles must fuse with the outer NM and the unenveloped capsids then acquire a second envelope in the trans-Golgi network. Little is known about the process by which herpesviruses virions fuse with the outer NM. Here we show that a herpes simplex virus (HSV) mutant lacking both the two putative fusion glycoproteins gB and gH failed to cross the nuclear envelope. Enveloped virions accumulated in the perinuclear space or in membrane vesicles that bulged into the nucleoplasm (herniations). By contrast, mutants lacking just gB or gH showed only minor or no defects in nuclear egress. We concluded that either HSV gB or gH can promote fusion between the virion envelope and the outer NM. It is noteworthy that fusion associated with HSV entry requires the cooperative action of both gB and gH, suggesting that the two types of fusion (egress versus entry) are dissimilar processes.
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Affiliation(s)
- Aaron Farnsworth
- *Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239
| | - Todd W. Wisner
- *Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239
| | - Michael Webb
- *Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239
| | - Richard Roller
- Department of Microbiology, University of Iowa, Iowa City, IA 52242; and
| | - Gary Cohen
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Roselyn Eisenberg
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - David C. Johnson
- *Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239
- To whom correspondence should be addressed. E-mail:
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