scholarly journals Role of Vesicle-Associated Membrane Protein-Associated Proteins (VAP) A and VAPB in Nuclear Egress of the Alphaherpesvirus Pseudorabies Virus

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1117
Author(s):  
Anna D. Dorsch ◽  
Julia E. Hölper ◽  
Kati Franzke ◽  
Luca M. Zaeck ◽  
Thomas C. Mettenleiter ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Nuclear Membrane ◽  
Pseudorabies Virus ◽  
Rabbit Kidney ◽  
Double Knockout ◽  
Virus Propagation ◽  
Herpes Simplex Virus 1 ◽  
Nuclear Egress ◽  
Virion Envelope ◽  
Simplex Virus

The molecular mechanism affecting translocation of newly synthesized herpesvirus nucleocapsids from the nucleus into the cytoplasm is still not fully understood. The viral nuclear egress complex (NEC) mediates budding at and scission from the inner nuclear membrane, but the NEC is not sufficient for efficient fusion of the primary virion envelope with the outer nuclear membrane. Since no other viral protein was found to be essential for this process, it was suggested that a cellular machinery is recruited by viral proteins. However, knowledge on fusion mechanisms involving the nuclear membranes is rare. Recently, vesicle-associated membrane protein-associated protein B (VAPB) was shown to play a role in nuclear egress of herpes simplex virus 1 (HSV-1). To test this for the related alphaherpesvirus pseudorabies virus (PrV), we mutated genes encoding VAPB and VAPA by CRISPR/Cas9-based genome editing in our standard rabbit kidney cells (RK13), either individually or in combination. Single as well as double knockout cells were tested for virus propagation and for defects in nuclear egress. However, no deficiency in virus replication nor any effect on nuclear egress was obvious suggesting that VAPB and VAPA do not play a significant role in this process during PrV infection in RK13 cells.

scholarly journals Phosphorylation of the UL31 Protein of Herpes Simplex Virus 1 by the US3-Encoded Kinase Regulates Localization of the Nuclear Envelopment Complex and Egress of Nucleocapsids

2009 ◽  
Vol 83 (10) ◽  
pp. 5181-5191 ◽  
Author(s):  
Fan Mou ◽  
Elizabeth Wills ◽  
Joel D. Baines
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Nuclear Membrane ◽  
Normal Function ◽  
Viral Envelope ◽  
Productive Infection ◽  
Herpes Simplex Virus 1 ◽  
Nuclear Egress ◽  
Virion Envelope ◽  
Simplex Virus

ABSTRACT Herpes simplex virus 1 nucleocapsids bud through the inner nuclear membrane (INM) into the perinuclear space to obtain a primary viral envelope. This process requires a protein complex at the INM composed of the UL31 and UL34 gene products. While it is clear that the viral kinase encoded by the US3 gene regulates the localization of pUL31/pUL34 within the INM, the molecular mechanism by which this is accomplished remains enigmatic. Here, we have determined the following. (i) The N terminus of pUL31 is indispensable for the protein's normal function and contains up to six serines that are phosphorylated by the US3 kinase during infection. (ii) Phosphorylation at these six serines was not essential for a productive infection but was required for optimal viral growth kinetics. (iii) In the presence of active US3 kinase, changing the serines to alanine caused the pUL31/pUL34 complex to aggregate at the nuclear rim and caused some virions to accumulate aberrantly in herniations of the nuclear membrane, much as in cells infected with a US3 kinase-dead mutant. (iv) The replacement of the six serines of pUL31 with glutamic acid largely restored the smooth distribution of pUL34/pUL31 at the nuclear membrane and precluded the accumulation of virions in herniations whether or not US3 kinase was active but also precluded the optimal primary envelopment of nucleocapsids. These observations indicate that the phosphorylation of pUL31 by pUS3 represents an important regulatory event in the virion egress pathway that can account for much of pUS3's role in nuclear egress. The data also suggest that the dynamics of pUL31 phosphorylation modulate both the primary envelopment and the subsequent fusion of the nascent virion envelope with the outer nuclear membrane.

scholarly journals Identification of the Capsid Binding Site in the Herpes Simplex Virus 1 Nuclear Egress Complex and Its Role in Viral Primary Envelopment and Replication

2019 ◽  
Vol 93 (21) ◽  
Author(s):  
Kosuke Takeshima ◽  
Jun Arii ◽  
Yuhei Maruzuru ◽  
Naoto Koyanagi ◽  
Akihisa Kato ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Binding Site ◽  
Nuclear Membrane ◽  
Capsid Proteins ◽  
Herpes Simplex Virus 1 ◽  
Nuclear Egress ◽  
Perinuclear Space ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT During nuclear egress of nascent progeny herpesvirus nucleocapsids, the nucleocapsids acquire a primary envelope by budding through the inner nuclear membrane of infected cells into the perinuclear space between the inner and outer nuclear membranes. Herpes simplex virus 1 (HSV-1) UL34 and UL31 proteins form a nuclear egress complex (NEC) and play critical roles in this budding process, designated primary envelopment. To clarify the role of NEC binding to progeny nucleocapsids in HSV-1 primary envelopment, we established an assay system for HSV-1 NEC binding to nucleocapsids and capsid proteins in vitro. Using this assay system, we showed that HSV-1 NEC bound to nucleocapsids and to capsid protein UL25 but not to the other capsid proteins tested (i.e., VP5, VP23, and UL17) and that HSV-1 NEC binding of nucleocapsids was mediated by the interaction of NEC with UL25. UL31 residues arginine-281 (R281) and aspartic acid-282 (D282) were required for efficient NEC binding to nucleocapsids and UL25. We also showed that alanine substitution of UL31 R281 and D282 reduced HSV-1 replication, caused aberrant accumulation of capsids in the nucleus, and induced an accumulation of empty vesicles that were similar in size and morphology to primary envelopes in the perinuclear space. These results suggested that NEC binding via UL31 R281 and D282 to nucleocapsids, and probably to UL25 in the nucleocapsids, has an important role in HSV-1 replication by promoting the incorporation of nucleocapsids into vesicles during primary envelopment. IMPORTANCE Binding of HSV-1 NEC to nucleocapsids has been thought to promote nucleocapsid budding at the inner nuclear membrane and subsequent incorporation of nucleocapsids into vesicles during nuclear egress of nucleocapsids. However, data to directly support this hypothesis have not been reported thus far. In this study, we have present data showing that two amino acids in the membrane-distal face of the HSV-1 NEC, which contains the putative capsid binding site based on the solved NEC structure, were in fact required for efficient NEC binding to nucleocapsids and for efficient incorporation of nucleocapsids into vesicles during primary envelopment. This is the first report showing direct linkage between NEC binding to nucleocapsids and an increase in nucleocapsid incorporation into vesicles during herpesvirus primary envelopment.

scholarly journals The Torsin Activator LULL1 Is Required for Efficient Growth of Herpes Simplex Virus 1

2015 ◽  
Vol 89 (16) ◽  
pp. 8444-8452 ◽  
Author(s):  
Elizabeth M. Turner ◽  
Rebecca S. H. Brown ◽  
Ethan Laudermilch ◽  
Pei-Ling Tsai ◽  
Christian Schlieker
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Genome Engineering ◽  
Phenotypic Analysis ◽  
Double Knockout ◽  
Herpes Simplex Virus 1 ◽  
Aaa Atpase ◽  
Nuclear Egress ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTTorsinA is a membrane-tethered AAA+ ATPase implicated in nuclear envelope dynamics as well as the nuclear egress of herpes simplex virus 1 (HSV-1). The activity of TorsinA and the related ATPase TorsinB strictly depends on LAP1 and LULL1, type II transmembrane proteins that are integral parts of the Torsin/cofactor AAA ring, forming a composite, membrane-spanning assembly. Here, we use CRISPR/Cas9-mediated genome engineering to create single- and double knockout (KO) cell lines of TorA and TorB as well as their activators, LAP1 and LULL1, to investigate the effect on HSV-1 production. Consistent with LULL1 being the more potent Torsin activator, a LULL1 KO reduces HSV-1 growth by one order of magnitude, while the deletion of other components of the Torsin system in combination causes subtle defects. Notably, LULL1 deficiency leads to a 10-fold decrease in the number of viral genomes per host cell without affecting viral protein production, allowing us to tentatively assign LULL1 to an unexpected role that precedes HSV-1 nuclear egress.IMPORTANCEIn this study, we conduct the first comprehensive genetic and phenotypic analysis of the Torsin/cofactor system in the context of HSV-1 infection, establishing LULL1 as the most important component of the Torsin system with respect to viral production.

scholarly journals Function of Torsin AAA+ ATPases in Pseudorabies Virus Nuclear Egress

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 738
Author(s):  
Julia E. Hölper ◽  
Barbara G. Klupp ◽  
G. W. Gant Luxton ◽  
Kati Franzke ◽  
Thomas C. Mettenleiter
Keyword(s):  
Nuclear Membrane ◽  
Pseudorabies Virus ◽  
Gene Knockout ◽  
Early Time ◽  
Wild Type ◽  
Mutant Proteins ◽  
Nuclear Egress ◽  
Cytoplasmic Transport ◽  
Virion Envelope ◽  
Aaa Atpases

Newly assembled herpesvirus nucleocapsids traverse the intact nuclear envelope by a vesicle-mediated nucleo-cytoplasmic transport for final virion maturation in the cytoplasm. For this, they bud at the inner nuclear membrane resulting in primary enveloped particles in the perinuclear space (PNS) followed by fusion of the primary envelope with the outer nuclear membrane (ONM). While the conserved viral nuclear egress complex orchestrates the first steps, effectors of fusion of the primary virion envelope with the ONM are still mostly enigmatic but might include cellular proteins like SUN2 or ESCRT-III components. Here, we analyzed the influence of the only known AAA+ ATPases located in the endoplasmic reticulum and the PNS, the Torsins (Tor), on nuclear egress of the alphaherpesvirus pseudorabies virus. For this overexpression of wild type and mutant proteins as well as CRISPR/Cas9 genome editing was applied. Neither single overexpression nor gene knockout (KO) of TorA or TorB had a significant impact. However, TorA/B double KO cells showed decreased viral titers at early time points of infection and an accumulation of primary virions in the PNS pointing to a delay in capsid release during nuclear egress.

scholarly journals Highly Basic Clusters in the Herpes Simplex Virus 1 Nuclear Egress Complex Drive Membrane Budding by Inducing Lipid Ordering

mBio ◽  
2021 ◽  
Author(s):  
Michael K. Thorsen ◽  
Alex Lai ◽  
Michelle W. Lee ◽  
David P. Hoogerheide ◽  
Gerard C. L. Wong ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Nuclear Membrane ◽  
Herpes Simplex Virus 1 ◽  
Nuclear Egress ◽  
Membrane Budding ◽  
Simplex Virus

Herpesviruses are large viruses that infect nearly all vertebrates and some invertebrates and cause lifelong infections in most of the world’s population. During replication, herpesviruses export their capsids from the nucleus into the cytoplasm by an unusual mechanism in which the viral nuclear egress complex (NEC) deforms the nuclear membrane around the capsid.

scholarly journals Extragenic Suppression of a Mutation in Herpes Simplex Virus 1 UL34 That Affects Lamina Disruption and Nuclear Egress

2016 ◽  
Vol 90 (23) ◽  
pp. 10738-10751 ◽  
Author(s):  
Amber Vu ◽  
Chelsea Poyzer ◽  
Richard Roller
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Nuclear Shape ◽  
Lamin A ◽  
Herpes Simplex Virus 1 ◽  
Inner Nuclear Membrane ◽  
Nuclear Egress ◽  
Simplex Virus

ABSTRACT Nuclear egress of herpesviruses is accompanied by changes in the architecture of the nuclear membrane and nuclear lamina that are thought to facilitate capsid access to the inner nuclear membrane (INM) and curvature of patches of the INM around the capsid during budding. Here we report the properties of a point mutant of pUL34 (Q163A) that fails to induce gross changes in nuclear architecture or redistribution of lamin A/C. The UL34(Q163A) mutant shows a roughly 100-fold defect in single-step growth, and it forms small plaques. This mutant has a defect in nuclear egress, and furthermore, it fails to disrupt nuclear shape or cause observable displacement of lamin A/C despite retaining the ability to recruit the pUS3 and PKC protein kinases and to mediate phosphorylation of emerin. Extragenic suppressors of the UL34(Q163A) phenotype were isolated, and all of them carry a single mutation of arginine 229 to leucine in UL31. Surprisingly, although this UL31 mutation largely restores virus replication, it does not correct the lamina disruption defect, suggesting that, in Vero cells, changes in nuclear shape and gross displacements of lamin A/C may facilitate but are unnecessary for nuclear egress. IMPORTANCE Herpesvirus nuclear egress is an essential and conserved process that requires close association of the viral capsid with the inner nuclear membrane and budding of the capsid into that membrane. Access to the nuclear membrane and tight curvature of that membrane are thought to require disruption of the nuclear lamina that underlies the inner nuclear membrane, and consistent with this idea, herpesvirus infection induces biochemical and architectural changes at the nuclear membrane. The significance of the nuclear membrane architectural changes is poorly characterized. The results presented here address that deficiency in our understanding and show that a combination of mutations in two of the viral nuclear egress factors results in a failure to accomplish at least two components of lamina disruption while still allowing relatively efficient viral replication, suggesting that changes in nuclear shape and displacement of lamins are not necessary for herpes simplex virus 1 (HSV-1) nuclear egress.

scholarly journals Role of Host Cell p32 in Herpes Simplex Virus 1 De-Envelopment during Viral Nuclear Egress

2015 ◽  
Vol 89 (17) ◽  
pp. 8982-8998 ◽  
Author(s):  
Zhuoming Liu ◽  
Akihisa Kato ◽  
Masaaki Oyama ◽  
Hiroko Kozuka-Hata ◽  
Jun Arii ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Nuclear Membrane ◽  
Cell Protein ◽  
Structural Protein ◽  
Herpes Simplex Virus 1 ◽  
Nuclear Egress ◽  
Infected Cells ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACTTo clarify the function(s) of the herpes simplex virus 1 (HSV-1) major virion structural protein UL47 (also designated VP13/14), we screened cells overexpressing UL47 for UL47-binding cellular proteins. Tandem affinity purification of transiently expressed UL47 coupled with mass spectrometry-based proteomics technology and subsequent analyses showed that UL47 interacted with cell protein p32 in HSV-1-infected cells. Unlike in mock-infected cells, p32 accumulated at the nuclear rim in HSV-1-infected cells, and this p32 recruitment to the nuclear rim required UL47. p32 formed a complex(es) with HSV-1 proteins UL31, UL34, Us3, UL47, and/or ICP22 in HSV-1-infected cells. All these HSV-1 proteins were previously reported to be important for HSV-1 nuclear egress, in which nucleocapsids bud through the inner nuclear membrane (primary envelopment) and the enveloped nucleocapsids then fuse with the outer nuclear membrane (de-envelopment). Like viral proteins UL31, UL34, Us3, and UL47, p32 was detected in primary enveloped virions. p32 knockdown reduced viral replication and induced membranous invaginations adjacent to the nuclear rim containing primary enveloped virions and aberrant localization of UL31 and UL34 in punctate structures at the nuclear rim. These effects of p32 knockdown were reduced in the absence of UL47. Therefore, the effects of p32 knockdown in HSV-1 nuclear egress were similar to those of the previously reported mutation(s) in HSV-1 regulatory proteins for HSV-1 de-envelopment during viral nuclear egress. Collectively, these results suggested that p32 regulated HSV-1 de-envelopment and replication in a UL47-dependent manner.IMPORTANCEIn this study, we have obtained data suggesting that (i) the HSV-1 major virion structural protein UL47 interacted with host cell protein p32 and mediated the recruitment of p32 to the nuclear rim in HSV-1-infected cells; (ii) p32 was a component of the HSV-1 nuclear egress complex (NEC), whose core components were UL31 and UL34; and (iii) p32 regulated HSV-1 de-envelopment during viral nuclear egress. It has been reported that p32 was a component of human cytomegalovirus NEC and was required for efficient disintegration of nuclear lamina, which has been thought to facilitate HSV-1 primary envelopment during viral nuclear egress. Thus, p32 appeared to be a core component of herpesvirus NECs, like UL31 and UL34 homologs in other herpesviruses, and to play multiple roles in herpesvirus nuclear egress.

scholarly journals Herpesvirus gB-Induced Fusion between the Virion Envelope and Outer Nuclear Membrane during Virus Egress Is Regulated by the Viral US3 Kinase

2009 ◽  
Vol 83 (7) ◽  
pp. 3115-3126 ◽  
Author(s):  
Todd W. Wisner ◽  
Catherine C. Wright ◽  
Akihisa Kato ◽  
Yasushi Kawaguchi ◽  
Fan Mou ◽  
...  
Keyword(s):  
Nuclear Membrane ◽  
In Vitro Assays ◽  
Nuclear Fraction ◽  
Dependent Manner ◽  
Outer Nuclear Membrane ◽  
Nuclear Egress ◽  
Perinuclear Space ◽  
Virion Envelope ◽  
Simplex Virus

ABSTRACT Herpesvirus capsids collect along the inner surface of the nuclear envelope and bud into the perinuclear space. Enveloped virions then fuse with the outer nuclear membrane (NM). We previously showed that herpes simplex virus (HSV) glycoproteins gB and gH act in a redundant fashion to promote fusion between the virion envelope and the outer NM. HSV mutants lacking both gB and gH accumulate enveloped virions in herniations, vesicles that bulge into the nucleoplasm. Earlier studies had shown that HSV mutants lacking the viral serine/threonine kinase US3 also accumulate herniations. Here, we demonstrate that HSV gB is phosphorylated in a US3-dependent manner in HSV-infected cells, especially in a crude nuclear fraction. Moreover, US3 directly phosphorylated the gB cytoplasmic (CT) domain in in vitro assays. Deletion of gB in the context of a US3-null virus did not add substantially to defects in nuclear egress. The majority of the US3-dependent phosphorylation of gB involved the CT domain and amino acid T887, a residue present in a motif similar to that recognized by US3 in other proteins. HSV recombinants lacking gH and expressing either gB substitution mutation T887A or a gB truncated at residue 886 displayed substantial defects in nuclear egress. We concluded that phosphorylation of the gB CT domain is important for gB-mediated fusion with the outer NM. This suggested a model in which the US3 kinase is incorporated into the tegument layer (between the capsid and envelope) in HSV virions present in the perinuclear space. By this packaging, US3 might be brought close to the gB CT tail, leading to phosphorylation and triggering fusion between the virion envelope and the outer NM.

scholarly journals Glycoproteins Required for Entry Are Not Necessary for Egress of Pseudorabies Virus

2008 ◽  
Vol 82 (13) ◽  
pp. 6299-6309 ◽  
Author(s):  
Barbara Klupp ◽  
Jan Altenschmidt ◽  
Harald Granzow ◽  
Walter Fuchs ◽  
Thomas C. Mettenleiter
Keyword(s):  
Nuclear Membrane ◽  
Pseudorabies Virus ◽  
Virus Entry ◽  
Viral Envelope ◽  
Detectable Effect ◽  
Nuclear Egress ◽  
Viral Glycoproteins ◽  
Simplex Virus

ABSTRACT In the current perception of the herpesvirus replication cycle, two fusion processes are thought to occur during entry and nuclear egress. For penetration, glycoproteins gB and gH/gL have been shown to be essential, whereas a possible role of these glycoproteins in nuclear egress remains unclear. Viral envelope glycoproteins have been detected by immunolabeling in the nuclear membrane as well as in primary enveloped particles in several herpesviruses, indicating that they might be involved in the fusion process. Moreover, a herpes simplex virus type 1 mutant simultaneously lacking gB and gH was described to be deficient in nuclear egress (A. Farnsworth, T. W. Wisner, M. Webb, R. Roller, G. Cohen, R. Eisenberg, and D. C. Johnson, Proc. Natl. Acad. Sci. USA 104:10187-10192, 2007). To analyze the situation in the related alphaherpesvirus pseudorabies virus (PrV), mutants carrying single and double deletions of glycoproteins gB, gD, gH, and gL were constructed and characterized. We show here that the simultaneous deletion of gB and gD, gB and gH, gD and gH, or gH and gL has no detectable effect on PrV egress, implying that none of these glycoproteins either singly or in the tested combinations is required for nuclear egress. In addition, immunolabeling studies using different mono- or polyclonal sera raised against various PrV glycoproteins did not reveal the presence of viral glycoproteins in the inner nuclear membrane or in primary virions. Thus, our data strongly suggest that different fusion mechanisms are active during virus entry and egress.

scholarly journals Host and Viral Factors Involved in Nuclear Egress of Herpes Simplex Virus 1

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 754
Author(s):  
Jun Arii
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Nuclear Membrane ◽  
Molecular Mechanisms ◽  
Nucleocytoplasmic Transport ◽  
Herpes Simplex Virus 1 ◽  
Similar System ◽  
Nuclear Egress ◽  
Simplex Virus ◽  
Hsv 1

Herpes simplex virus 1 (HSV-1) replicates its genome and packages it into capsids within the nucleus. HSV-1 has evolved a complex mechanism of nuclear egress whereby nascent capsids bud on the inner nuclear membrane to form perinuclear virions that subsequently fuse with the outer nuclear membrane, releasing capsids into the cytosol. The viral-encoded nuclear egress complex (NEC) plays a crucial role in this vesicle-mediated nucleocytoplasmic transport. Nevertheless, similar system mediates the movement of other cellular macromolecular complexes in normal cells. Therefore, HSV-1 may utilize viral proteins to hijack the cellular machinery in order to facilitate capsid transport. However, little is known about the molecular mechanisms underlying this phenomenon. This review summarizes our current understanding of the cellular and viral factors involved in the nuclear egress of HSV-1 capsids.

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