Retrieval of human cytomegalovirus glycoprotein B from the infected cell surface for virus envelopment

Radsak, K.; Eickmann, Markus; Mockenhaupt, T.; Bogner, Elke; Kern, H.; Eis‐Hübinger, Anna Maria; Reschke, M.

doi:10.1007/bf01718317

Cited by 77 publications

(93 citation statements)

References 33 publications

(48 reference statements)

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“…Thus, our results that demonstrate the importance of endocytosis of gpUL132 for optimal replication of HCMV are somewhat at odds with the previous findings on endocytosis of HCMV glycoproteins and replication efficiency. Early reports by Radsak showed that gB is incorporated into the virion following retrieval of the protein from the plasma membrane (45). These findings have been confirmed by others (56).…”

Section: Vol 84 2010 Hcmv Glycoprotein Endocytosis 7047supporting

confidence: 58%

“…In the case of HCMV little information is available on endocytosis of envelope glycoproteins. Radsak and colleagues were the first to show that gB is retrieved from the infected cell surface prior to incorporation into the virion (45). These findings were confirmed by others (56).…”

mentioning

confidence: 63%

“…For a large number of envelope glycoproteins, however, it has been shown that they follow an internalization pathway after having reached the plasma membrane and accumulate in interior compartments of the cell, such as the TGN or vesicles derived from this cellular structure (1,8,9,9,17,30,42,43). A wellstudied member of this group of proteins is glycoprotein B (gB), which has been shown for a number of herpesviruses to be internalized from the plasma membrane and incorporated into the virion (4,14,21,45,57). However, the functional relevance of endocytosis for viral replication and/or pathogenesis is less clear.…”

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confidence: 99%

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Optimal Replication of Human Cytomegalovirus Correlates with Endocytosis of Glycoprotein gpUL132

Kropff¹,

Koedel

Britt

et al. 2010

J Virol

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Envelopment of a herpesvirus particle is a complex process of which much is still to be learned. We previously identified the glycoprotein gpUL132 of human cytomegalovirus (HCMV) as an envelope component of the virion. In its carboxy-terminal portion, gpUL132 contains at least four motifs for sorting of transmembrane proteins to endosomes; among them are one dileucine-based signal and three tyrosine-based signals of the YXXØ and NPXY (where X stands for any amino acid, and Ø stands for any bulky hydrophobic amino acid) types. To investigate the role of each of these trafficking signals in intracellular localization and viral replication, we constructed a panel of expression plasmids and recombinant viruses in which the signals were rendered nonfunctional by mutagenesis. In transfected cells wild-type gpUL132 was mainly associated with the trans-Golgi network. Consecutive mutation of the trafficking signals resulted in increasing fractions of the protein localized at the cell surface, with gpUL132 mutated in all four trafficking motifs predominantly associated with the plasma membrane. Concomitant with increased surface expression, endocytosis of mutant gpUL132 was reduced, with a gpUL132 expressing all four motifs in mutated form being almost completely impaired in endocytosis. The replication of recombinant viruses harboring mutations in single trafficking motifs was comparable to replication of wild-type virus. In contrast, viruses containing mutations in three or four of the trafficking signals showed pronounced deficits in replication with a reduction of approximately 100-fold. Moreover, recombinant viruses expressing gpUL132 with three or four trafficking motifs mutated failed to incorporate the mutant protein into the virus particle. These results demonstrate a role of endocytosis of an HCMV envelope glycoprotein for incorporation into the virion and optimal virus replication.Morphogenesis of herpesviruses is a complex multistep process which requires the assembly of an infectious viral particle containing Ͼ70 proteins. The proteins are organized into distinct regions in the particle, including the capsid containing viral DNA, the tegument, and the envelope of the virion, suggesting an ordered addition of viral proteins during assembly.Most data in the literature favor a model in which the final virion is assembled by multiple budding and fusion events of the nascent particle. According to this model, genome-containing capsids acquire a first envelope by budding at the inner nuclear membrane in a step termed primary envelopment (34).

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Section: Vol 84 2010 Hcmv Glycoprotein Endocytosis 7047supporting

confidence: 58%

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confidence: 63%

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confidence: 99%

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Optimal Replication of Human Cytomegalovirus Correlates with Endocytosis of Glycoprotein gpUL132

Kropff¹,

Koedel

Britt

et al. 2010

J Virol

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“…In addition to gE of varicella-zoster virus (VZV), herpes simplex virus type 1 (HSV-1) gE and pseudorabies virus (PrV) gE undergo endocytosis (2,3,47,58,57). Also, PrV gB and human cytomegalovirus (HCMV) gB internalize in transfected cells (51,58,60). Unlike the situation for other human herpesviruses, the predominant VZV glycoprotein present on the envelope of the mature virion is gE (4,23,44).…”

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confidence: 99%

“…Endocytosis of several HCMV surface proteins, including gB, most likely plays a role in targeting these proteins to the organelle of virion assembly (18,19,51). However, inhibition of HCMV gB endocytosis had a variable effect on virus release or the production of infectious virions, depending on the study (5,36,51). These data, considered together with the observation that PrV gE endocytosis apparently is not required for incorporation (57,58), raise a question about the role of glycoprotein endocytosis in viral assembly.…”

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Incorporation of Three Endocytosed Varicella-Zoster Virus Glycoproteins, gE, gH, and gB, into the Virion Envelope

Marešová

Pasieka

Homan

et al. 2005

J Virol

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The cytoplasmic tails of all three major varicella-zoster virus (VZV) glycoproteins, gE, gH, and gB, harbor functional tyrosine-based endocytosis motifs that mediate internalization. The aim of the present study was to examine whether endocytosis from the plasma membrane is a cellular route by which VZV glycoproteins are delivered to the final envelopment compartment. In this study, we demonstrated that internalization of the glycoproteins occurred in the first 24 h postinfection but was reduced later in infection. Using surface biotinylation of VZV-infected cells followed by a glutathione cleavage assay, we showed that endocytosis was independent of antibody binding to gE, gH, and gB. Subsequently, with this assay, we demonstrated that biotinylated gE, gH, and gB retrieved from the cell surface were incorporated into nascent virus particles isolated after density gradient sedimentation. To confirm and extend this finding, we repeated the above sedimentation step and specifically detected envelopes decorated with Streptavidin-conjugated gold beads on a majority of complete virions through examination by transmission electron microscopy. In addition, a gE-gI complex and a gE-gH complex were found on the virions. Therefore, the above studies established that VZV subsumed a postendocytosis trafficking pathway as one mechanism by which to deliver viral glycoproteins to the site of virion assembly in the cytoplasm. Furthermore, since a recombinant VZV genome lacking only endocytosis-competent gE cannot replicate, these results supported the conclusion that the endocytosisenvelopment pathway is an essential component of the VZV life cycle.Endocytosis has now been demonstrated for numerous herpesvirus type 1 glycoproteins in transfected cell systems. In addition to gE of varicella-zoster virus (VZV), herpes simplex virus type 1 (HSV-1) gE and pseudorabies virus (PrV) gE undergo endocytosis (2,3,47,58,57). Also, PrV gB and human cytomegalovirus (HCMV) gB internalize in transfected cells (51,58,60). Unlike the situation for other human herpesviruses, the predominant VZV glycoprotein present on the envelope of the mature virion is gE (4,23,44). The gE protein traffics from the endoplasmic reticulum (ER) through the Golgi apparatus, where it is extensively processed, to the outer cell membrane. Both the ectodomain and the endodomain of gE have important functions. Based on the fact that a single point mutation in the VZV-MSP gE ectodomain changes the VZV-MSP egress pattern from a typical "viral highway" phenotype to a diffuse pattern similar to that observed in HSV-1-infected cells (53, 54), the ectodomain is likely to be critical for determining virus-cell interactions of mature virions.VZV gE endocytosis is mediated by a YAGL sequence located in the cytoplasmic tail of the protein (47). This sequence fits the consensus tyrosine-based YXX⌽ endocytosis motif (where Y is tyrosine, X is any amino acid, and ⌽ is any bulky hydrophobic amino acid) (6). Recycling of gE back to the plasma membrane postendocytosis has been demonst...

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Intracellular Transport and Maturation Pathway of Human Herpesvirus 6

et al. 1999

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A peculiar characteristic of cells infected with human herpesvirus 6 (HHV6) is the absence of viral glycoproteins on the plasma membrane, which may reflect an atypical intracellular transport of the virions and/or the viral glycoproteins, different from that of the other members of the herpesvirus family. To investigate the maturation pathway of HHV-6 in the human T lymphoid cell line HSB-2, we used lectin cytochemistry and immunogold labeling combined with several electron microscopical techniques, such as ultrathin frozen sections, postembedding, and fracture-label. Immunolabeling with anti-gp116 and anti-gp82-gp105 monoclonal antibodies revealed that the viral glycoproteins are undetectable on nuclear membranes and that at the inner nuclear membrane nucleocapsids acquire a primary envelope lacking viral glycoproteins. After de-envelopment, cytoplasmic nucleocapsids acquire a thick tegument and a secondary envelope with viral glycoproteins at the level of neo-formed annulate lamellae or at the cis-side of the Golgi complex. Cytochemical labeling using helix pomatia lectin revealed that the newly acquired secondary viral envelopes contain intermediate forms of glycocomponents, suggesting a sequential glycosylation of the virions during their transit through the Golgi area before their final release into the extracellular space. Immunogold labeling also showed that the viral glycoproteins, which are not involved in the budding process, reach and accumulate in the endosomal/lysosomal compartment. Pulse-chase analysis indicated degradation of the gp116, consistent with its endosomal localization and with the absence of viral glycoproteins on the cell surface of the infected cells.

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Retrieval of human cytomegalovirus glycoprotein B from the infected cell surface for virus envelopment

Cited by 77 publications

References 33 publications

Optimal Replication of Human Cytomegalovirus Correlates with Endocytosis of Glycoprotein gpUL132

Optimal Replication of Human Cytomegalovirus Correlates with Endocytosis of Glycoprotein gpUL132

Incorporation of Three Endocytosed Varicella-Zoster Virus Glycoproteins, gE, gH, and gB, into the Virion Envelope

Intracellular Transport and Maturation Pathway of Human Herpesvirus 6

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