Herpes Simplex Virus 1 UL34 Protein Regulates the Global Architecture of the Endoplasmic Reticulum in Infected Cells

ABSTRACT Upon herpes simplex virus 1 (HSV-1) infection, the CD98 heavy chain (CD98hc) is redistributed around the nuclear membrane (NM), where it promotes viral de-envelopment during the nuclear egress of nucleocapsids. In this study, we attempted to identify the factor(s) involved in CD98hc accumulation and demonstrated the following: (i) the null mutation of HSV-1 UL34 caused specific dispersion throughout the cytoplasm of CD98hc and the HSV-1 de-envelopment regulators, glycoproteins B and H (gB and gH); (ii) as observed with CD98hc, gB, and gH, wild-type HSV-1 infection caused redistribution of the endoplasmic reticulum (ER) markers calnexin and ERp57 around the NM, whereas the UL34-null mutation caused cytoplasmic dispersion of these markers; (iii) the ER markers colocalized efficiently with CD98hc, gB, and gH in the presence and absence of UL34 in HSV-1-infected cells; (iv) at the ultrastructural level, wild-type HSV-1 infection caused ER compression around the NM, whereas the UL34-null mutation caused cytoplasmic dispersion of the ER; and (v) the UL34-null mutation significantly decreased the colocalization efficiency of lamin protein markers of the NM with CD98hc and gB. Collectively, these results indicate that HSV-1 infection causes redistribution of the ER around the NM, with resulting accumulation of ER-associated CD98hc, gB, and gH around the NM and that UL34 is required for ER redistribution, as well as for efficient recruitment to the NM of the ER-associated de-envelopment factors. Our study suggests that HSV-1 induces remodeling of the global ER architecture for recruitment of regulators mediating viral nuclear egress to the NM. IMPORTANCE The ER is an important cellular organelle that exists as a complex network extending throughout the cytoplasm. Although viruses often remodel the ER to facilitate viral replication, information on the effects of herpesvirus infections on ER morphological integrity is limited. Here, we showed that HSV-1 infection led to compression of the global ER architecture around the NM, resulting in accumulation of ER-associated regulators associated with nuclear egress of HSV-1 nucleocapsids. We also identified HSV-1 UL34 as a viral factor that mediated ER remodeling. Furthermore, we demonstrated that UL34 was required for efficient targeting of these regulators to the NM. To our knowledge, this is the first report showing that a herpesvirus remodels ER global architecture. Our study also provides insight into the mechanism by which the regulators for HSV-1 nuclear egress are recruited to the NM, where this viral event occurs.

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Protein Kinase B/Akt Is Present in Activated Form throughout the Entire Replicative Cycle of ΔUS3 Mutant Virus but Only at Early Times after Infection with Wild-Type Herpes Simplex Virus 1

Journal of Virology ◽

10.1128/jvi.80.7.3341-3348.2006 ◽

2006 ◽

Vol 80 (7) ◽

pp. 3341-3348 ◽

Cited By ~ 51

Author(s):

Luca Benetti ◽

Bernard Roizman

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Protein Kinase ◽

Protein Kinase B ◽

Mutant Virus ◽

Wild Type ◽

Herpes Simplex Virus 1 ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

ABSTRACT The product of the herpes simplex virus 1 (HSV-1) US3 gene is a multifunctional serine-threonine protein kinase that can block apoptosis induced by proapoptotic cellular proteins, exogenous agents, or replication-defective viruses. Earlier studies showed that the US3 kinase activates and functionally overlaps cellular protein kinase A (PKA). In this study we examined the status of phosphatidylinositol 3-kinase [PI(3)K] and of its effector, protein kinase B/Akt (PKB/Akt), a component of a major pathway of mammalian antiapoptotic signaling systems. We report the following. (i) Infection of target cells with HSV-1 induces transient phosphorylation of serine 473 of PKB/Akt early in infection, with a mechanism that is dependent on PI(3)K. Inhibition of PI(3)K induced apoptosis in mock-infected or ΔUS3 mutant-virus-infected but not in wild-type-virus-infected cells and reduced the accumulation of specific viral gene products, including the US3 protein kinase, but had a marginal effect on virus yields. (ii) At later times after infection, the total amounts of PKB/Akt decreased and phosphorylated PKB/Akt forms disappeared in a US3-dependent and protein phosphatase 2A-independent manner. (iii) Activation of PKA by forskolin did not mediate significant dephosphorylation of PKB/Akt. Our results are consistent with the model that PKB/Akt is activated early in infection and acts to block apoptosis in infected cells prior to the accumulation of US3 protein kinase and that it persists and continues to function as an antiapoptotic protein in the absence of US3 but becomes redundant or even inimical once US3 protein kinase accumulates in effective amounts.

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Overexpression of Promyelocytic Leukemia Protein Precludes the Dispersal of ND10 Structures and Has No Effect on Accumulation of Infectious Herpes Simplex Virus 1 or Its Proteins

Journal of Virology ◽

10.1128/jvi.76.18.9355-9367.2002 ◽

2002 ◽

Vol 76 (18) ◽

pp. 9355-9367 ◽

Cited By ~ 51

Author(s):

Pascal Lopez ◽

Robert J. Jacob ◽

Bernard Roizman

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Viral Replication ◽

Promyelocytic Leukemia ◽

Wild Type ◽

Herpes Simplex Virus 1 ◽

Promyelocytic Leukemia Protein ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

ABSTRACT A key early event in the replication of herpes simplex virus 1 (HSV-1) is the localization of infected-cell protein no. 0 (ICP0) in nuclear structures knows as ND10 or promyelocytic leukemia oncogenic domains (PODs). This is followed by dispersal of ND10 constituents such as the promyelocytic leukemia protein (PML), CREB-binding protein (CBP), and Daxx. Numerous experiments have shown that this dispersal is mediated by ICP0. PML is thought to be the organizing structural component of ND10. To determine whether the virus targets PML because it is inimical to viral replication, telomerase-immortalized human foreskin fibroblasts and HEp-2 cells were transduced with wild-type baculovirus or a baculovirus expressing the M r 69,000 form of PML. The transduced cultures were examined for expression and localization of PML in mock-infected and HSV-1-infected cells. The results obtained from studies of cells overexpressing PML were as follows. (i) Transduced cells accumulate large amounts of unmodified and SUMO-I-modified PML. (ii) Mock-infected cells exhibited enlarged ND10 structures containing CBP and Daxx in addition to PML. (iii) In infected cells, ICP0 colocalized with PML in ND10 early in infection, but the two proteins did not overlap or were juxtaposed in orderly structures. (iv) The enlarged ND10 structures remained intact at least until 12 h after infection and retained CBP and Daxx in addition to PML. (v) Overexpression of PML had no effect on the accumulation of viral proteins representative of α, β, or γ groups and had no effect on the accumulation of infectious virus in cells infected with wild-type virus or a mutant (R7910) from which the α0 genes had been deleted. These results indicate the following: (i) PML overexpressed in transduced cells cannot be differentiated from endogenous PML with respect to sumoylation and localization in ND10 structures. (ii) PML does not affect viral replication or the changes in the localization of ICP0 through infection. (iii) Disaggregation of ND10 structures is not an obligatory event essential for viral replication.

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

Journal of Virology ◽

10.1128/jvi.01220-15 ◽

2015 ◽

Vol 89 (17) ◽

pp. 8982-8998 ◽

Cited By ~ 32

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.

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Assembly of VP26 in herpes simplex virus-1 capsid implicated by 3-D structure of recombinant capsid

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140579 ◽

1995 ◽

Vol 53 ◽

pp. 840-841

Author(s):

Z. Hong Zhou ◽

Jing He ◽

Joanita Jakana ◽

J. D. Tatman ◽

Frazer J. Rixon ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

3D Structure ◽

Structure Study ◽

Herpes Simplex Virus 1 ◽

Shell Proteins ◽

Life Threatening ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

Herpes simplex virus-1 (HSV-1) is a ubiquitous virus which is implicated in diseases ranging from self-curing cold sores to life-threatening infections. The 2500 Å diameter herpes virion is composed of a glycoprotein spike containing, lipid envelope, enclosing a protein layer (the tegument) in which is embedded the capsid (which contains the dsDNA genome). The B-, and A- and C-capsids, representing different morphogenetic stages in HSV-1 infected cells, are composed of 7, and 5 structural proteins respectively. The three capsid types are organized in similar T=16 icosahedral shells with 12 pentons, 150 hexons, and 320 connecting triplexes. Our previous 3D structure study at 26 Å revealed domain features of all these structural components and suggested probable locations for the outer shell proteins, VP5, VP26, VP19c and VP23. VP5 makes up most of both pentons and hexons. VP26 appeared to bind to the VP5 subunit in hexon but not to that in penton.

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Antiviral Activity of the G-Quadruplex Ligand TMPyP4 against Herpes Simplex Virus-1

Viruses ◽

10.3390/v13020196 ◽

2021 ◽

Vol 13 (2) ◽

pp. 196

Author(s):

Sara Artusi ◽

Emanuela Ruggiero ◽

Matteo Nadai ◽

Beatrice Tosoni ◽

Rosalba Perrone ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Dna Replication ◽

Herpes Simplex ◽

Antiviral Activity ◽

Herpes Simplex Virus 1 ◽

Tem Analysis ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

The herpes simplex virus 1 (HSV-1) genome is extremely rich in guanine tracts that fold into G-quadruplexes (G4s), nucleic acid secondary structures implicated in key biological functions. Viral G4s were visualized in HSV-1 infected cells, with massive virus cycle-dependent G4-formation peaking during viral DNA replication. Small molecules that specifically interact with G4s have been shown to inhibit HSV-1 DNA replication. We here investigated the antiviral activity of TMPyP4, a porphyrin known to interact with G4s. The analogue TMPyP2, with lower G4 affinity, was used as control. We showed by biophysical analysis that TMPyP4 interacts with HSV-1 G4s, and inhibits polymerase progression in vitro; in infected cells, it displayed good antiviral activity which, however, was independent of inhibition of virus DNA replication or entry. At low TMPyP4 concentration, the virus released by the cells was almost null, while inside the cell virus amounts were at control levels. TEM analysis showed that virus particles were trapped inside cytoplasmatic vesicles, which could not be ascribed to autophagy, as proven by RT-qPCR, western blot, and immunofluorescence analysis. Our data indicate a unique mechanism of action of TMPyP4 against HSV-1, and suggest the unprecedented involvement of currently unknown G4s in viral or antiviral cellular defense pathways.

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Nucleolin Is Required for Efficient Nuclear Egress of Herpes Simplex Virus Type 1 Nucleocapsids

Journal of Virology ◽

10.1128/jvi.02007-09 ◽

2009 ◽

Vol 84 (4) ◽

pp. 2110-2121 ◽

Cited By ~ 29

Author(s):

Ken Sagou ◽

Masashi Uema ◽

Yasushi Kawaguchi

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Nuclear Membrane ◽

Herpes Simplex Virus Type ◽

Viral Dna ◽

Nuclear Egress ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

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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Simultaneous Tracking of Capsid, Tegument, and Envelope Protein Localization in Living Cells Infected with Triply Fluorescent Herpes Simplex Virus 1

Journal of Virology ◽

10.1128/jvi.02681-07 ◽

2008 ◽

Vol 82 (11) ◽

pp. 5198-5211 ◽

Cited By ~ 98

Author(s):

Ken Sugimoto ◽

Masashi Uema ◽

Hiroshi Sagara ◽

Michiko Tanaka ◽

Tetsutaro Sata ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Envelope Protein ◽

Fluorescent Proteins ◽

Protein Localization ◽

Envelope Proteins ◽

Herpes Simplex Virus 1 ◽

Infected Cells ◽

Simplex Virus ◽

Hsv 1

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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Cbl E3 Ligase Mediates the Removal of Nectin-1 from the Surface of Herpes Simplex Virus 1-Infected Cells

Journal of Virology ◽

10.1128/jvi.00393-17 ◽

2017 ◽

Vol 91 (12) ◽

Cited By ~ 6

Author(s):

Thibaut Deschamps ◽

Christos Dogrammatzis ◽

Ranajoy Mullick ◽

Maria Kalamvoki

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Growth Factor ◽

Cell Surface ◽

E3 Ligase ◽

Herpes Simplex Virus 1 ◽

Infected Cells ◽

Simplex Virus ◽

Entry Receptor ◽

Hsv 1

ABSTRACT The Cbl E3 ligase has been linked to the down-modulation of surface signaling responses by inducing internalization of surface receptors. The adaptor protein CIN85 is a partner of Cbl that augments many of these interactions. Previously, an interaction was demonstrated between ICP0 and CIN85, which results in the removal of epidermal growth factor receptor (EGFR) from the surface of the infected cells with a concomitant attenuation of EGFR signaling. Here, we examined whether Cbl mediates the removal of the herpes simplex virus 1 (HSV-1) entry receptor Nectin-1 from the surface of infected cells. We found the following: (i) that Cbl, Nectin-1, and the viral glycoprotein D (gD) form a complex in infected cells; (ii) that during infection Nectin-1 is removed from the surface of the infected cells but is retained on the surface of cells that have been depleted of Cbl; and (iii) that in cells infected with a ΔICP0 mutant virus, Nectin-1 remained on the cell surface. Thus, Cbl is necessary but not sufficient for the removal of Nectin-1 from the cell surface. In addition, we observed that in Cbl-depleted cells there was enhanced entry after infection. These cells were susceptible to secondary infections by HSV-1. Viral entry in CIN85-depleted cells was only moderately enhanced compared to that in the Cbl-depleted cells, suggesting that the Cbl–Nectin-1 interaction is likely the key to the downregulation of surface Nectin-1. The removal of the HSV-1 entry receptor Nectin-1 from the surface of the infected cells may be part of the strategy of the virus to efficiently spread to uninfected cells. IMPORTANCE The Cbl E3 ligase suppresses surface signaling responses by inducing internalization of surface components. The targets of Cbl include such components as immune system receptors, growth factor receptors, adhesion, and cell-to-cell contact molecules. The immediate early protein ICP0 of herpes simplex virus 1 (HSV-1) interacts with CIN85, an adaptor protein that augments Cbl functions. The consequence of this interaction is the removal of the epidermal growth factor receptor (EGFR) from the surface of the infected cells with concomitant suppression of the EGF ligand signaling. The viral entry receptor Nectin-1 is also internalized during HSV-1 infection in a Cbl-dependent mechanism, and that increases the opportunity of the virus to spread to uninfected cells. The diversion of the Cbl/CIN85 endocytic machinery may be a strategy utilized by the virus to alter the cell surface pattern to prevent detrimental host responses.

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Herpes Simplex Virus 1 Latency and the Kinetics of Reactivation Are Regulated by a Complex Network of Interactions between the Herpesvirus Entry Mediator, Its Ligands (gD, BTLA, LIGHT, and CD160), and the Latency-Associated Transcript

Journal of Virology ◽

10.1128/jvi.01451-18 ◽

2018 ◽

Vol 92 (24) ◽

Cited By ~ 9

Author(s):

Shaohui Wang ◽

Alexander V. Ljubimov ◽

Ling Jin ◽

Klaus Pfeffer ◽

Mitchell Kronenberg ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Trigeminal Ganglia ◽

Wild Type ◽

Herpes Simplex Virus 1 ◽

Latently Infected ◽

Simplex Virus ◽

Kinetics Of ◽

Herpesvirus Entry Mediator ◽

Hsv 1

ABSTRACTRecently, we reported that the herpesvirus entry mediator (HVEM; also called TNFRSF14 or CD270) is upregulated by the latency-associated transcript (LAT) of herpes simplex virus 1 (HSV-1) and that the absence of HVEM affects latency reactivation but not primary infection in ocularly infected mice. gD has been shown to bind to HVEM. LIGHT (TNFSF14), CD160, and BTLA (B- and T-lymphocyte attenuator) also interact with HVEM and can interfere with HSV gD binding. It was not known if LIGHT, CD160, or BTLA affected the level of latency reactivation in the trigeminal ganglia (TG) of latently infected mice. To address this issue, we ocularly infected LIGHT−/−, CD160−/−, and BTLA−/−mice with LAT(+) and LAT(−) viruses, using similarly infected wild-type (WT) and HVEM−/−mice as controls. The amount of latency, as determined by the levels of gB DNA in the TG of the LIGHT−/−, CD160−/−, and BTLA−/−mice infected with either LAT(+) or LAT(−) viruses, was lower than that in WT mice infected with LAT(+) virus and was similar in WT mice infected with LAT(−) virus. The levels of LAT RNA in HVEM−/−, LIGHT−/−, CD160−/−, and BTLA−/−mice infected with LAT(+) virus were similar and were lower than the levels of LAT RNA in WT mice. However, LIGHT−/−, CD160−/−, and BTLA−/−mice, independent of the presence of LAT, had levels of reactivation similar to those of WT mice infected with LAT(+) virus. Faster reactivation correlated with the upregulation of HVEM transcript. The LIGHT−/−, CD160−/−, and BTLA−/−mice had higher levels of HVEM expression, and this, along with the absence of BTLA, LIGHT, or CD160, may contribute to faster reactivation, while the absence of each molecule, independent of LAT, may have contributed to lower latency. This study suggests that, in the absence of competition with gD for binding to HVEM, LAT RNA is important for WT levels of latency but not for WT levels of reactivation.IMPORTANCEThe effects of BTLA, LIGHT, and CD160 on latency reactivation are not known. We show here that in BTLA, LIGHT, or CD160 null mice, latency is reduced; however, HVEM expression is upregulated compared to that of WT mice, and this upregulation is associated with higher reactivation that is independent of LAT but dependent on gD expression. Thus, one of the mechanisms by which BTLA, LIGHT, and CD160 null mice enhance reactivation appears to be the increased expression of HVEM in the presence of gD. Thus, our results suggest that blockade of HVEM-LIGHT-BTLA-CD160 contributes to reduced HSV-1 latency and reactivation.

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hnRNPA2B1 Associated with Recruitment of RNA into Exosomes Plays a Key Role in Herpes Simplex Virus 1 Release from Infected Cells

Journal of Virology ◽

10.1128/jvi.00367-20 ◽

2020 ◽

Vol 94 (13) ◽

Author(s):

Xusha Zhou ◽

Lei Wang ◽

Weixuan Zou ◽

Xiaoqing Chen ◽

Bernard Roizman ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Cell Contact ◽

Apical Surface ◽

Herpes Simplex Virus 1 ◽

Fold Reduction ◽

Infected Cells ◽

Simplex Virus ◽

Extracellular Environment ◽

Hsv 1

ABSTRACT hnRNPA2B1, an abundant cellular protein, has been reported to recruit RNAs bearing a specific sequence (EXO motif) into exosomes. We characterized an exosome population averaging 100 ± 50 nm in diameter and containing a defined set of constitutive exosome markers. This population packages microRNAs (miRNAs) and can be directed to block targeted gene expression in a dose-dependent fashion. The objective of this study was to characterize the role of hnRNPA2B1 in the recruitment of miRNA. We report the following four key findings. (i) hnRNPA2B1 is not a component of exosomes produced in HEp-2 or HEK293T cells. Hence, hnRNPA2B1 carries its cargo, at most, to the site of exosome assembly, but it is not itself incorporated into exosomes. (ii) The accumulation of exosomes produced by cells in which the gene encoding hnRNPA2B1 has been knocked out (ΔhnRNPA2B1 cells) was reduced 3-fold. (iii) In uninfected HEp-2 cells, hnRNPA2B1 is localized in the nucleus. In cells infected with herpes simplex virus 1 (HSV-1), hnRNPA2B1 was quantitatively exported to the cytoplasm and at least a fraction of hnRNPA2B1 colocalized with a Golgi marker. (iv) Lastly, in ΔhnRNPA2B1 cells, there was a 2- to 3-fold reduction in virus yield but a significant (>10-fold) reduction in HSV-1 released through the apical surface into the extracellular environment. The absence of hnRNPA2B1 had no significant impact on the basolateral export of HSV-1 from infected to uninfected cells by direct cell-to-cell contact. The results suggest that hnRNPA2B1 plays a key role in the transport of enveloped virus from its site of assembly to the extracellular environment. IMPORTANCE In this report, we show that hnRNPA2B1 is not a component of exosomes produced in HEp-2 or HEK293T cells. In herpes simplex virus 1 (HSV-1)-infected cells, hnRNPA2B1 was quantitatively translocated from the nucleus into the cytoplasm. In infected ΔhnRNPA2B1 cells, Golgi-dependent transport of virus from the apical surface to the extracellular medium was significantly reduced. In essence, this report supports the hypothesis that hnRNPA2B1 plays a key role in the egress of exosomes and HSV-1 from infected cells.

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