Herpes simplex virus type 1 ICP27-dependent activation of NF-κB

Department of Microbiology and Immunology, 837 MEJB, University of North Carolina, Chapel Hill, NC 27599-7290, USA.
Journal of Virology (Impact Factor: 4.44). 12/2006; 80(21):10565-78. DOI: 10.1128/JVI.01119-06
Source: PubMed


The ability of herpes simplex virus type 1 (HSV-1) to activate NF-kappaB has been well documented. Beginning at 3 to 5 h postinfection, HSV-1 induces a robust and persistent nuclear translocation of an NF-kappaB-dependent (p50/p65 heterodimer) DNA binding activity, as measured by electrophoretic mobility shift assay. Activation requires virus binding and entry, as well as de novo infected-cell protein synthesis, and is accompanied by loss of both IkappaBalpha and IkappaBbeta. In this study, we identified loss of IkappaBalpha as a marker of NF-kappaB activation, and infection with mutants with individual immediate-early (IE) regulatory proteins deleted indicated that ICP27 was necessary for IkappaBalpha loss. Analysis of both N-terminal and C-terminal mutants of ICP27 identified the region from amino acids 21 to 63 as being necessary for IkappaBalpha loss. Additional experiments with mutant viruses with combinations of IE genes deleted revealed that the ICP27-dependent mechanism of NF-kappaB activation may be augmented by functional ICP4. We also analyzed two additional markers for NF-kappaB activation, phosphorylation of the p65 subunit on Ser276 and Ser536. Phosphorylation of both serines was induced upon HSV infection and required functional ICP4 and ICP27. Pharmacological inhibitor studies revealed that both IkappaBalpha and Ser276 phosphorylation were dependent on Jun N-terminal protein kinase activity, while Ser536 phosphorylation was not affected during inhibitor treatment. These results demonstrate that there are several layers of regulation of NF-kappaB activation during HSV infection, highlighting the important role that NF-kappaB may play in infection.

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Available from: Steven L. Bachenheimer, Apr 23, 2015
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    • "It has been reported that suppression of MAPK or NF-jB signaling pathway could block HSV replication (Faith et al., 2006; Qiu et al., 2013; Song et al., 2014). Early studies from Hargett et al. demonstrated that ICP27 was important for activation of NF-jB (Hargett et al., 2006) as well as for activation of JNK and P38 (Hargett et al., 2005) in HSV-1 infected cells. Our data showed that harmine inhibited immediate early viral gene expression including ICP0, ICP4 and ICP27 in HSV-1 infected cells (Fig. 2). "
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    ABSTRACT: Herpes simplex virus types 1 and 2 (HSV-1 and -2) are highly prevalent in many populations and therapeutic options are limited. Both viruses can establish latency by maintaining viral genomes in neurons of sensory ganglia. Primary or recurrent HSV infections may lead to deleterious outcomes: HSV-1 infection may result in corneal blindness and encephalitis and HSV-2 infection leads to herpes genitalis. While no effective vaccine is available, acyclovir is widely used for therapy, which targets and inhibits viral DNA polymerase. Although acyclovir is of low toxicity, resistant strains arise due to persistent use, mainly in immune compromised patients. In our effort to identify new HSV inhibitory molecules, harmine was found to potently inhibit HSV infection. Harmine, a beta-carbone alkaloid with an indole core structure and a pyridine ring, is widely distributed in plants. Earlier studies showed that harmine exhibited pharmacological activities such as antifungal, antimicrobial, antitumor, antiplasmodoal and antioxidants. In the current study, we showed that harmine was a potent inhibitor of HSV-2 infection in vitro assays with EC50 value at around 1.47 μM and CC50 value at around 337.10 μM. The HSV RNA transcription, protein synthesis, and virus titers were reduced by the presence of harmine in a dose dependent manner. Further study on the mechanism of the anti-HSV activity showed that harmine blocked HSV-induced ROS production and the upregulated cytokine/chemokine expression, but our evidence showed that the inhibition of viral replication was unlikely mediated by the blocking of ROS production. We demonstrated that harmine significantly reduced HSV-2-induced NF-κB activation, as well as IκB-α degradation and p65 nuclear translocation. We found that harmine also inhibited HSV-2-mediated p38 kinase and c-Jun N-terminal kinases (JNK) phosphorylation.
    Full-text · Article · Sep 2015 · Antiviral research
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    • "The virion gD is also thought to stimulate NF-kB signaling (Medici et al., 2003; Sciortino et al., 2008) so multiple virion proteins affect NF-kB signaling. Once the immediate-early proteins are expressed, the ICP0 protein can inhibit TLR2 signaling (van Lint et al., 2010), and the ICP27 protein leads to a stimulation of NF-kB signaling in cells that do not express TLR2 (Hargett et al., 2006). This complex regulation and the opposing effects of these proteins may have evolved to provide some NF-kB stimulation to allow optimal replication and infected cell survival while restricting the NF-kB stimulation so that a strong antiviral innate response is not induced. "
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    ABSTRACT: Herpes simplex virus (HSV) has evolved multiple strategies to modulate host immune responses. In a screen of HSV open reading frames to identify additional HSV-encoded proteins that affect NF-κB signaling, we identified the viral US3 tegument protein as an inhibitor of NF-κB signaling. We found that the US3 protein is required for inhibition of TLR2 signaling induced by viral infection and that this inhibition occurs at very early times post-infection. Expression of US3 in transfected cells inhibits TLR2 signaling induced by Zymosan, and this inhibition occurs at or downstream of MyD88 and upstream of p65. Polyubiquitination of TRAF6 is critical for its function in TLR2 signaling. Using US3-null and US3 kinase-defective mutant viruses, we demonstrate that HSV US3 reduces TRAF6 polyubiquitination and that the kinase activity of US3 is necessary for this effect. Therefore, US3 is necessary and sufficient for inhibiting TLR2 signaling at or before the stage of TRAF6 ubiquitination.
    Full-text · Article · Mar 2013 · Virology
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    • "Lipopolysaccharide from Salmonella enterica was shown to activate both canonical and non-canonical pathways in primary B cells with activation of both NFκB p50/RELA and p52/RELB heterodimers [26]. Herpes simplex virus type 1 ICP27 protein was shown to activate NFκB via the canonical pathway [30]. While the role of NFκB in apoptosis following adenoviral infection has been explored [31], its role in cytokine regulation due to viral infection has been less fully addressed. "
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