Cell Fusion Induced by Herpes Simplex Virus Glycoproteins gB, gD, and gH-gL Requires a gD Receptor but Not Necessarily Heparan Sulfate

Pertel, Peter; Fridberg, Alina; Parish, Mary Lynn; Spear, Patricia G.

doi:10.1006/viro.2000.0713

Cited by 259 publications

(361 citation statements)

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“…HSV-1 gH is present on the surface of infected cells and virus particles as a heterodimer with gL (6), and gL is absolutely required for cell-cell and virus-cell fusion (24,47). It is not clear at present whether gL has a role in hemifusion other than to ensure the appropriate folding and localization of gH.…”

Section: Discussionmentioning

confidence: 99%

Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B

Subramanian

Geraghty

2007

Proc. Natl. Acad. Sci. U.S.A.

158

145

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Virus-induced membrane fusion can be subdivided into three phases defined by studies of class I and class II fusion proteins. During Phase I, two membranes are brought into close apposition. Phase II marks the mixing of the outer membrane leaflets leading to formation of a hemifusion intermediate. A fusion pore stably forms and expands in Phase III, thereby completing the fusion process. Herpes simplex virus type 1 (HSV-1) requires four glycoproteins to complete membrane fusion, but none has been defined as class I or II. Therefore, we investigated whether HSV-1-induced membrane fusion occurred following the same general phases as those described for class I and II proteins. In this study we demonstrate that glycoprotein D (gD) and the glycoprotein H and glycoprotein L complex (gHL) mediated lipid mixing indicative of hemifusion. However, content mixing and full fusion required glycoprotein B (gB) to be present along with gD and gHL. Our results indicate that, like class I and II fusion proteins, fusion mediated by HSV-1 glycoproteins occurred through a hemifusion intermediate. In addition, both gB and gHL are probably directly involved in the fusion process. From this, we propose a sequential model for fusion via HSV-1 glycoproteins whereby gD is required for Phase I, gHL is required for Phase II, and gB is required for Phase III. We further propose that glycoprotein H and gB are likely to function sequentially to promote membrane fusion in other herpesviruses such as Epstein-Barr virus and human herpesvirus 8.lipid transfer ͉ membrane fusion ͉ fluorescence microscopy S tudies using class I and class II fusion proteins have demonstrated that virus-induced membrane fusion can be subdivided into three phases (1, 2). Phase I involves bringing opposing membranes into close proximity through a viral glycoprotein binding a cellular receptor. Phase II involves the initiation of lipid mixing between the two apposed membranes and is completed when the outer membrane leaflets are mixed to form an intermediate called hemifusion. Phase III begins when the inner membrane leaflets are mixed and continues the pore formation and expansion. The completion of Phase III signifies the completion of the fusion process. The three phases of membrane fusion (close apposition, hemifusion, and complete fusion) are useful to characterize functions of viral glycoproteins in the fusion process (1, 3, 4). Fusion proteins that have Phase I function bring membranes in close apposition and ultimately result in the initiation of the fusion process. Fusion proteins that have Phase II function are capable of mixing outer membrane leaflets leading to hemifusion. Phase III fusion proteins are capable of forming and expanding a fusion pore. For many viruses, one or two fusion proteins can carry out all phases of membrane fusion. The fusion process has yet to be characterized for viruses that require more than two fusion glycoproteins, and a major issue is whether multiple glycoproteins mediate fusion through a hemifusion intermediate.Herpes simplex ...

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Section: Discussionmentioning

confidence: 99%

Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B

Subramanian

Geraghty

2007

Proc. Natl. Acad. Sci. U.S.A.

158

145

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“…Fusion of cells mimics the fusion of virion and target cells that occurs during viral entry (36). In this experiment, Chinese hamster ovary (CHO-K1) cells, designated "effector" cells, were generated.…”

Section: -O-sulfated Octasaccharide Inhibited Herpes Simplex Virus 1mentioning

confidence: 99%

Using a 3-O-Sulfated Heparin Octasaccharide To Inhibit the Entry of Herpes Simplex Virus Type 1

et al. 2008

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Heparan sulfate (HS) is a highly sulfated polysaccharide and is present in large quantities on the cell surface and in the extracellular matrix. Herpes simplex virus type 1(HSV-1) utilizes a specialized cell surface HS, known as 3-O-sulfated HS, as an entry receptor to establish infection. Here, we exploit an approach to inhibit HSV-1 infection by using a 3-O-sulfated octasaccharide, mimicking the active domain of the entry receptor. The 3-O-sulfated octasaccharide was synthesized by incubating a heparin octasaccharide (3-OH octasaccharide) with HS 3-O-sulfotransferase isoform 3. The resultant 3-O-sulfated octasaccharide has a structure of ΔUA2S-GlcNS6S-IdoUA2S-GlcNS6S-IdoUA2S-GlcNS3S6S-IdoUA2S-GlcNS6S (where ΔUA is 4-deoxy-α-L-threo-hex-4-enopyranosyluronic acid, GlcN is D-glucosamine and IdoUA is L-iduronic acid). Results from cell based assays revealed that the 3-O-sulfated octasaccharide has stronger activity in blocking HSV-1 infection than that of the 3-OH octasaccharide, suggesting that the inhibition of HSV-1 infection requires a unique sulfation moiety. Our results suggest the feasibility of inhibiting HSV-1 infection by blocking viral entry with a specific oligosaccharide. KeywordsHeparin; heparan sulfate; herpes simplex virus; glycoprotein D; sulfotransferase; oligosaccharides Heparan sulfate (HS) is a highly sulfated linear polysaccharide present ubiquitously on the cell surface and in the extracellular matrix. HS plays a role in regulating embryonic development, inflammatory response, blood coagulation and assisting viral/bacterial infections (1). Heparin, a commonly used anticoagulant drug, is a special form of HS containing glucuronic (GlcUA)/ iduronic acid (IdoUA) and glucosamine, each carrying sulfo groups (Fig. 1A). The uniquely distributed sulfation pattern of HS polysaccharide is believed to regulate its functional specificity (2-4). Thus, understanding the structure and function relationship of HS attracts considerable interest in improving the anticoagulant efficacy of heparin and exploiting heparin *Corresponding author: Rm 309, Beard Hall, University of North Carolina, Chapel Hill, NC 27599. Tel.: 919-843-6511; Fax: 919-843-5432; E-mail: jian_liu@unc.edu. NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2009 May 27. Published in final edited form as:Biochemistry. 2008 May 27; 47(21): 5774-5783. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript or heparin-like molecules for the development of anticancer and antiviral drugs (5-7). The major difficulty in dissecting the structure and function relationship of HS is to obtain HS oligosaccharides or polysaccharides with defined structures. Chemical synthesis has been the major route to prepare structurally defined oligosaccharides to mimic the functions of HS. However, the synthesis of those molecules larger than hexasaccharides is extremely difficult. Using HS biosynthetic enzymes to prepare biologically active polysaccharides and oligosaccharides has recently gained momentum...

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“…More recent studies of recombinant viruses with specific deletions in gB has shown that gB is essential for the production of infectious virus (21,22). Finally, gB coexpressed with other viral glycoproteins is required for cell-cell fusion in cell-based fusion assays for pseudorabies virus, HSV-1, HSV-2, and EBV (8,[23][24][25][26][27].gB is one of the most conserved proteins within the herpesvirus family and consists of a large amino-terminal ectodomain, This paper was submitted directly (Track II) to the PNAS office.Abbreviations: HHV, human herpesvirus; HSV, herpes simplex virus; ER, endoplasmic reticulum; EBV, Epstein-Barr virus; HEK, human embryonic kidney; CHO, Chinese hamster ovary. …”

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Cell-surface expression of a mutated Epstein–Barr virus glycoprotein B allows fusion independent of other viral proteins

McShane

Longnecker

2004

Proc. Natl. Acad. Sci. U.S.A.

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Epstein-Barr virus (EBV) infects human B lymphocytes and epithelial cells. We have compared the requirements for EBV glycoprotein-induced cell fusion between Chinese hamster ovary effecter cells and human B lymphoblasts or epithelial cells by using a virus-free cell fusion assay. EBV-encoded gB, gH, gL, and gp42 glycoproteins were required for efficient B cell fusion, whereas EBV gB, gH, and gL glycoproteins were required for Chinese hamster ovary effecter cell fusion with epithelial cell lines (AGS and SCC68) or the human embryonic kidney cell line 293-P. Fusion with human embryonic kidney 293-P cells was greater than fusion observed with B cells, indicative of an important role for cell contact. An antibody directed against the gH and gL complex inhibited epithelial cell fusion. Increased surface expression of gB alone as a result of truncations or point mutants in the carboxyl-terminal tail allowed gB-mediated fusion with epithelial cells, albeit at a lower level than with coexpression of gB, gH, and gL. Overall, gB appears to be the critical component for EBV glycoprotein-mediated cell fusion. viral entry ͉ herpesvirus T he entry process of human herpesviruses entails a two-step process: binding followed by fusion. Specific herpesvirusencoded glycoproteins and cell-surface receptors are important for both events (1-3). Entry may occur by free virus infecting a cell or by cell-cell spread (2). In either case, fusion is a prerequisite for infection. Despite herpesvirus genomes encoding many viral glycoproteins, the glycoproteins implicated in entry and fusion are limited and conserved (1). Most herpesviruses require the conserved glycoproteins gH, gL, and gB, as well as an additional, family-specific viral glycoprotein, such as gD for ␣-herpesviruses or gp42 for the ␥-herpesvirus Epstein-Barr virus (EBV), for efficient entry and fusion (1). These nonconserved glycoproteins result in cell specificity by recognizing distinct cellular receptors. For example, EBV glycoprotein 42 binds to HLA class II on B cells, an interaction essential for the infection of B cells (4, 5). Additionally, EBV gp350͞220 binds to the B cell-surface receptor CD21͞CR2, and this binding mediates the initial interaction of EBV with B cells and is thought to tether the virus to promote the subsequent binding of gp42 to HLA class II (6, 7). The gp42-class II interaction is then proposed to trigger membrane fusion, a reaction mediated by gH (EBV gp85), gL (EBV gp25), and gB (EBV gp110) (8). The exact role each of these glycoproteins plays in fusion is unclear.EBV can enter cells by means of two routes, depending on the host cell type. In primary human lymphocytes, EBV is endocytosed before fusion, whereas, in B cells in culture, the virion envelope directly fuses with the plasma membrane (9, 10). Similarly to B cells in culture, fusion of EBV with epithelial cells occurs by direct fusion of the virion envelope with the plasma membrane. Despite B lymphocytes being the primary site for latency, the tropism of EBV for epithelial cells is suppor...

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Cell Fusion Induced by Herpes Simplex Virus Glycoproteins gB, gD, and gH-gL Requires a gD Receptor but Not Necessarily Heparan Sulfate

Cited by 259 publications

References 67 publications

Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B

Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B

Using a 3-O-Sulfated Heparin Octasaccharide To Inhibit the Entry of Herpes Simplex Virus Type 1

Cell-surface expression of a mutated Epstein–Barr virus glycoprotein B allows fusion independent of other viral proteins

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