Epitopes of Herpes Simplex Virus Type 1 Glycoprotein B that Bind Type-Common Neutralizing Antibodies Elicit Type-Specific Antibody-Dependent Cellular Cytotoxicity

Herpes simplex virus 1 (HSV-1) Us3 protein kinase phosphorylates threonine at position 887 (Thr-887) in the cytoplasmic tail of envelope glycoprotein B (gB) in infected cells. This phosphorylation downregulates cell surface expression of gB and plays a role in viral pathogenesis in the mouse herpes stromal keratitis model. In the present study, we demonstrated that Us3 phosphorylation of gB Thr-887 upregulated the accumulation of endocytosed gB from the surfaces of infected cells. We also showed that two motifs in the cytoplasmic tail of gB, tyrosine at position 889 (Tyr-889) and dileucines at positions 871 and 872, were required for efficient downregulation of gB cell surface expression and upregulation of accumulation of endocytosed gB in infected cells. A systematic analysis of mutations in these three sequences in gB suggested that the expression of gB on the surfaces of infected cells was downregulated in part by the increase in the accumulation of endocytosed gB, which was coordinately and tightly regulated by the three gB trafficking signals. Tyr-889 appeared to be of predominant importance in regulating the intracellular transport of gB and was linked to HSV-1 neurovirulence in mice following intracerebral infection. These observations support the hypothesis that HSV-1 evolved the three gB sequences for proper regulation of gB intracellular transport and that this regulation plays a critical role in diverse aspects of HSV-1 pathogenesis.Herpes simplex virus 1 (HSV-1) envelope glycoprotein B (gB) is well conserved throughout the Herpesviridae family (36). Like the gBs of other members of the Herpesviridae family, HSV-1 gB plays an essential role in viral entry. In HSV-1 entry into a cell, gB together with envelope glycoprotein gC mediates virus attachment by interacting with cell surface glycosaminoglycans, primarily heparan sulfate (19,20). Although not essential for entry, this attachment provides a stable interaction between the virion and the cell that facilitates the next entry steps (44). These steps have been suggested to include both the binding of the envelope glycoprotein gD to one of its identified receptors and the binding of gB to one of its identified receptors (2,15,33,42,43,45). Subsequent fusion between the virion envelope and the host cell membrane, which requires the cooperative function of a heterodimer of HSV-1 envelope glycoproteins gH/gL, gD, a gD receptor, gB, and a gB receptor, delivers the nucleocapsid into the host cell (37, 50). Another potential role of HSV-1 gB is to regulate the nuclear egress of nucleocapsids, during which nucleocapsids acquire primary envelopes by budding through the inner nuclear membrane into the space between the inner and outer nuclear membranes, followed by fusion with the outer nuclear membrane. In this process, gB has been proposed to be involved in promoting the fusion of the virion envelope with the outer nuclear membrane (12).In general, cell membrane glycoproteins are synthesized at the endoplasmic reticulum (ER) and travel through the Golgi app...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Role of the Herpes Simplex Virus 1 Us3 Kinase Phosphorylation Site and Endocytosis Motifs in the Intracellular Transport and Neurovirulence of Envelope Glycoprotein B

Imai

Arii

Minowa

et al. 2011

“…Furthermore, the effect of the gB-T887D mutation, which was predicted to mimic the phosphorylation of Thr-887, was different from that of T887A in gB, and the phenotype of the gB-T887D virus was identical to that of wild-type virus. It has been reported that gB on the cell surface is a potent inducer of the immune response in vivo (4,5,49,50), and it has been speculated that the downregulation of the cell surface expression of gB by endocytosis could involve immune evasion (7). In fact, the lysis of HSV-1-infected cells by natural killer cells correlates with the cell surface expression of gB (4).…”

Section: Discussionmentioning

confidence: 99%

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

Kato

Arii

Shiratori

et al. 2009

107

“…In vitro, gB is essential for attachment and entry of the virus into host cells, fusion, and cell-to-cell spread (42, 53), and its role in viral egress has been suggested (40). In vivo, HSV-1 gB is a potent inducer of the immune response (4,20,43,47,49,50) and has also been involved in neuroinvasion (18,34,51,62).HSV-1 gB is a 904-amino-acid (aa) type I membrane glycoprotein composed of a 696-aa ectodomain, a 69-aa transmembrane domain, and a 109-aa carboxy-terminal domain. The cytoplasmic domain of gB is the longest among HSV-1 glycoproteins, which suggests that it might play a role during infection.…”

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confidence: 99%

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confidence: 99%

Effects of Mutations in the Cytoplasmic Domain of Herpes Simplex Virus Type 1 Glycoprotein B on Intracellular Transport and Infectivity

Zarate

Kaelin

Rozenberg

2004

Herpes simplex virus type 1 (HSV-1) is a human pathogen of the alphaherpesvirus family which infects and spreads in the nervous system. Glycoproteins play a key role in the process of assembly and maturation of herpesviruses, which is essential for neuroinvasion and transneuronal spread. Glycoprotein B (gB) is a main component of the HSV-1 envelope and is necessary for the production of infectious particles. The cytoplasmic domain of gB, the longest one among HSV-1 glycoproteins, contains several highly conserved peptide sequences homologous to motifs involved in intracellular sorting. To determine the specific roles of these motifs in processing, subcellular localization, and the capacity of HSV-1 gB to complement a gB-null virus, we generated truncated or point mutated forms of a green fluorescent protein (GFP)-tagged gB. GFP-gB with a deletion in the acidic cluster DGDADEDDL (amino acids [aa] 896 to 904) behaved the same as the parental form. Deletion or disruption of the YTQV motif (aa 889 to 892) abolished internalization and reduced complementation by 60%. Disruption of the LL motif (aa 871 to 872) impaired the return of the protein to the trans-Golgi network (TGN) while enhancing its recycling to the plasma membrane. Truncations from residue E 857 abolished transport and processing of the truncated proteins, which had null complementation activity, through the Golgi complex. Altogether, our results favor a model in which HSV-1 gets its final envelope in the TGN, and they suggest that endocytosis, albeit not necessary, might play a role in infectivity.Herpes simplex virus type 1 (HSV-1) is a human alphaherpesvirus which generally causes benign infections of the skin and mucosa. The virus also infects neurons of the sensory ganglia, where it establishes latency. HSV-1 periodically reactivates to cause peripheral recurrences and occasionally spreads transneuronally to cause severe central nervous system infections. Although the mechanisms of neuroinvasion and transneuronal spread of alphaherpesviruses are not fully understood, they seem to be linked to the process of assembly and maturation of virions in infected cells, in which glycoproteins play a major role (33, 56).How HSV-1 particles are assembled and enveloped in infected cells is not completely known. The current view is that after primary envelopment at the inner nuclear membrane, capsids are de-enveloped through their exit from the nucleus and acquire their final envelope at the trans-Golgi network (TGN), where mature glycoproteins are incorporated (reviewed in reference 32). In support of this model, it has been shown that retention of glycoprotein D (gD) or gH in the endoplasmic reticulum (ER) of infected cells prevents their insertion into virions (6, 52, 61). Thus, proper intracellular transport of glycoproteins is necessary for successful incorporation into virions.gB, one of the most conserved envelope glycoproteins among herpesviruses, is essential at many steps of the viral replication cycle. In vitro, gB is essential for attachment and entr...