Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein

ABSTRACT Human cytomegalovirus (HCMV) glycoproteins gB and gH/gL are both necessary and sufficient for cell-cell fusion. However, it is not clear what roles these glycoproteins play in virus entry, whether acting directly in membrane fusion or in binding receptors. With other herpesviruses, it appea...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Paul T. Wille, Todd W. Wisner, Brent Ryckman, David C. Johnson
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/0531c9c615b847cda9893946045f0291
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:0531c9c615b847cda9893946045f0291
record_format	dspace
spelling	oai:doaj.org-article:0531c9c615b847cda9893946045f02912021-11-15T15:40:05ZHuman Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein10.1128/mBio.00332-132150-7511https://doaj.org/article/0531c9c615b847cda9893946045f02912013-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00332-13https://doaj.org/toc/2150-7511ABSTRACT Human cytomegalovirus (HCMV) glycoproteins gB and gH/gL are both necessary and sufficient for cell-cell fusion. However, it is not clear what roles these glycoproteins play in virus entry, whether acting directly in membrane fusion or in binding receptors. With other herpesviruses, it appears that gB is the fusion protein and is triggered by gH/gL, which, in some cases, binds receptors. However, for HCMV, there is published evidence that gB binds cellular ligands necessary to promote virus entry into or signaling of cells. Most mechanistic information on herpesvirus fusion proteins involves cell-cell fusion assays, which do not allow a determination of whether gB or gH/gL in the virion envelope must be oriented toward cellular membranes that contain receptors. Here, we showed that HCMV virions lacking gB were unable to enter normal cells but entered cells that expressed gB. Analyses of gB mutants lacking the cytoplasmic domain or with substitutions in putative “fusion loops” provided evidence that gB fusion activity was required for this “entry in trans.” In gB-mediated entry in trans, gB is oriented toward the virion envelope that apparently lacks receptors, arguing against an essential role for gB in binding receptors or signaling molecules. In contrast, particles lacking gH/gL did not enter cells expressing gH/gL, apparently because gH/gL must be oriented toward cellular membranes (which have receptors). Coupled with our previous interference studies, in which gH/gL expressed in cells blocked HCMV entry, our findings here support the hypothesis that HCMV gH/gL binds cellular receptors before triggering gB, which acts as the fusion protein. IMPORTANCE Human cytomegalovirus (HCMV) produces major disease in neonates and immunosuppressed transplant patients. As with other herpesviruses, HCMV requires two membrane glycoproteins, gB and gH/gL, to enter host cells. However, it has not been clear how gB and gH/gL function in two steps of the HCMV entry pathway, i.e., (i) binding of cellular receptors and (ii) fusion of the virion envelope with cellular membranes. There are studies that suggest that HCMV gB is required for receptor binding and other studies suggesting that gH/gL is the receptor binding protein and gB is the fusion protein. Here, we show that HCMV virions lacking gB can enter cells that express gB in cellular membranes. In contrast, virus particles lacking gH/gL could not enter cells expressing gH/gL. Our study supports the hypothesis that gB is the fusion protein and gH/gL acts upstream of gB to bind receptors and then activate gB for fusion.Paul T. WilleTodd W. WisnerBrent RyckmanDavid C. JohnsonAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 3 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Paul T. Wille Todd W. Wisner Brent Ryckman David C. Johnson Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
description	ABSTRACT Human cytomegalovirus (HCMV) glycoproteins gB and gH/gL are both necessary and sufficient for cell-cell fusion. However, it is not clear what roles these glycoproteins play in virus entry, whether acting directly in membrane fusion or in binding receptors. With other herpesviruses, it appears that gB is the fusion protein and is triggered by gH/gL, which, in some cases, binds receptors. However, for HCMV, there is published evidence that gB binds cellular ligands necessary to promote virus entry into or signaling of cells. Most mechanistic information on herpesvirus fusion proteins involves cell-cell fusion assays, which do not allow a determination of whether gB or gH/gL in the virion envelope must be oriented toward cellular membranes that contain receptors. Here, we showed that HCMV virions lacking gB were unable to enter normal cells but entered cells that expressed gB. Analyses of gB mutants lacking the cytoplasmic domain or with substitutions in putative “fusion loops” provided evidence that gB fusion activity was required for this “entry in trans.” In gB-mediated entry in trans, gB is oriented toward the virion envelope that apparently lacks receptors, arguing against an essential role for gB in binding receptors or signaling molecules. In contrast, particles lacking gH/gL did not enter cells expressing gH/gL, apparently because gH/gL must be oriented toward cellular membranes (which have receptors). Coupled with our previous interference studies, in which gH/gL expressed in cells blocked HCMV entry, our findings here support the hypothesis that HCMV gH/gL binds cellular receptors before triggering gB, which acts as the fusion protein. IMPORTANCE Human cytomegalovirus (HCMV) produces major disease in neonates and immunosuppressed transplant patients. As with other herpesviruses, HCMV requires two membrane glycoproteins, gB and gH/gL, to enter host cells. However, it has not been clear how gB and gH/gL function in two steps of the HCMV entry pathway, i.e., (i) binding of cellular receptors and (ii) fusion of the virion envelope with cellular membranes. There are studies that suggest that HCMV gB is required for receptor binding and other studies suggesting that gH/gL is the receptor binding protein and gB is the fusion protein. Here, we show that HCMV virions lacking gB can enter cells that express gB in cellular membranes. In contrast, virus particles lacking gH/gL could not enter cells expressing gH/gL. Our study supports the hypothesis that gB is the fusion protein and gH/gL acts upstream of gB to bind receptors and then activate gB for fusion.
format	article
author	Paul T. Wille Todd W. Wisner Brent Ryckman David C. Johnson
author_facet	Paul T. Wille Todd W. Wisner Brent Ryckman David C. Johnson
author_sort	Paul T. Wille
title	Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
title_short	Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
title_full	Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
title_fullStr	Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
title_full_unstemmed	Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein
title_sort	human cytomegalovirus (hcmv) glycoprotein gb promotes virus entry in <italic toggle="yes">trans</italic> acting as the viral fusion protein rather than as a receptor-binding protein
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/0531c9c615b847cda9893946045f0291
work_keys_str_mv	AT paultwille humancytomegalovirushcmvglycoproteingbpromotesvirusentryinitalictoggleyestransitalicactingastheviralfusionproteinratherthanasareceptorbindingprotein AT toddwwisner humancytomegalovirushcmvglycoproteingbpromotesvirusentryinitalictoggleyestransitalicactingastheviralfusionproteinratherthanasareceptorbindingprotein AT brentryckman humancytomegalovirushcmvglycoproteingbpromotesvirusentryinitalictoggleyestransitalicactingastheviralfusionproteinratherthanasareceptorbindingprotein AT davidcjohnson humancytomegalovirushcmvglycoproteingbpromotesvirusentryinitalictoggleyestransitalicactingastheviralfusionproteinratherthanasareceptorbindingprotein
_version_	1718427745501839360

Human Cytomegalovirus (HCMV) Glycoprotein gB Promotes Virus Entry In <italic toggle="yes">Trans</italic> Acting as the Viral Fusion Protein Rather than as a Receptor-Binding Protein

Ejemplares similares