Herpes Simplex Virus 1 Protein Kinase Us3 Phosphorylates Viral Envelope Glycoprotein B and Regulates Its Expression on the Cell Surface

Herpes simplex viruses (HSVs) are prevalent human pathogens that establish latency in human neuronal cells and efficiently evade the immune system. It has been a major medical challenge to eradicate them and, despite intensive efforts, an effective vaccine is not available. We previously showed that upon infection of antigen-presenting cells, HSV type 1 (HSV-1) rapidly and efficiently downregulates the major histocompatibility complex class I-like antigen-presenting molecule, CD1d, and potently inhibits its recognition by CD1d-restricted natural killer T (NKT) cells. It suppresses CD1d expression primarily by inhibiting its recycling to the cell surface after endocytosis. We identify here the viral glycoprotein B (gB) as the predominant CD1d-interacting protein. gB initiates the interaction with CD1d in the endoplasmic reticulum and stably associates with it throughout CD1d trafficking. However, an additional HSV-1 component, the serine-threonine kinase US3, is required for optimal CD1d downregulation. US3 expression in infected cells leads to gB enrichment in the trans-Golgi network (TGN) and enhances the relocalization of both gB and CD1d to this compartment, suggesting that following internalization CD1d is translocated from the endocytic pathway to the TGN by its association with gB. Importantly, both US3 and gB are required for efficient inhibition of CD1d antigen presentation and NKT cell activation. In summary, our results suggest that HSV-1 uses gB and US3 to rapidly inhibit NKT cell function in the initial antiviral response.

Section: Resultsmentioning

confidence: 99%

Section: Vol 85 2011mentioning

confidence: 99%

Herpes Simplex Virus 1 Glycoprotein B and US3 Collaborate To Inhibit CD1d Antigen Presentation and NKT Cell Function

Rao

Pham

Kulkarni

et al. 2011

“…The US3 kinase is conserved throughout the alphaherpesvirus subfamily but is not present in other herpesvirus genomes. The consensus target sequence for US3 of the porcine alphaherpesvirus PRV was characterized as R n X(S/T)ZZ, where n is greater than or equal to 2; X can be absent or Arg, Ala, Val, Pro, or Ser; and Z can be any amino acid except an acidic residue (116,183) and was found to be broadly similar for HSV-1 and -2 and VZV (48,58,183) and the cellular protein kinase A (17,89). Recent findings indicate that HSV-1 US3 is more promiscuous than previously thought and suggest the existence of more substrates than originally predicted (153).…”

Section: Herpesvirusesmentioning

confidence: 99%

Viral Serine/Threonine Protein Kinases

Jacob

Broeke

Favoreel

2011

109

Phosphorylation represents one the most abundant and important posttranslational modifications of proteins, including viral proteins. Virus-encoded serine/threonine protein kinases appear to be a feature that is unique to large DNA viruses. Although the importance of these kinases for virus replication in cell culture is variable, they invariably play important roles in virus virulence. The current review provides an overview of the different viral serine/threonine protein kinases of several large DNA viruses and discusses their function, importance, and potential as antiviral drug targets.

“…HSV-1 strain F, F-derived US3 Ϫ mutant vRR1202, vRR1202rep (US3-R; a repaired version of vRR1202), and the US3 kinase-inactive mutant vRR1205 (48) were all propagated and titered using Vero cells. HSV recombinant YK551, encoding a mutant form of gB (gBT887A), and a repaired version of this virus, YK553, were recently described (20). HSV gB Ϫ mutants were all propagated in VB38 cells that express gB, and HSV gB Ϫ gH Ϫ mutants were propagated in Vero-derived F6/gB12 cells, which express both gB and gH (14).…”

Section: Cells and Virusesmentioning

confidence: 99%

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

Wisner

Wright

Kato

et al. 2009

Self Cite

126

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.Most enveloped viruses assemble their capsids in the cytoplasm and then become enveloped by budding from the plasma membrane or into cytoplasmic (CT) membranes. Viruses that assemble capsids in the nucleus face the fundamental problem of transporting capsids across the nuclear envelope (NE). Nonenveloped viruses, such as polyomaviruses, that are relatively small can move through nuclear pores, and larger nonenveloped viruses, such as adenoviruses (Ad), disrupt the NE (12, 55). Herpesvirus capsids are too large to move through nuclear pores (18), and, instead, herpesviruses encode machinery which promotes envelopment at the inner nuclear membrane (NM) followed by fusion with the outer NM (29, 52). There appears to be very rapid fusion at the NE because few enveloped herpesvirus particles are normally observed within the perinuclear space. Once present in the cytoplasm, nonenveloped capsids acquire a secondary envelope, producing virions that bud into the Golgi apparatus or trans-Golgi network (13, 29, 52). These mature virions are then secreted from cells.Some aspects of the envelopment of herpesviruses at the inner NM are known. Here, the viruses encounter a major obstacle, the nuclear lamina, a rigid network of lamin proteins lining the inner NM. Herpesviruses disrupt the nuclear lamina in order to assemble along the inner surface of the NM...