Changes in Glycosylation of Rubella Virus Envelope Proteins During Maturation

New hepatitis B virions released from infected hepatocytes are the result of an intricate maturation process that starts with the formation of the nucleocapsid providing a confined space where the viral DNA genome is synthesized via reverse transcription. Virion assembly is finalized by the enclosure of the icosahedral nucleocapsid within a heterogeneous envelope. The latter contains integral membrane proteins of three sizes, collectively known as hepatitis B surface antigen, and adopts multiple conformations in the course of the viral life cycle. The nucleocapsid conformation depends on the reverse transcription status of the genome, which in turn controls nucleocapsid interaction with the envelope proteins for virus exit. In addition, after secretion the virions undergo a distinct maturation step during which a topological switch of the large envelope protein confers infectivity. Here we review molecular determinants for envelopment and models that postulate molecular signals encoded in the capsid scaffold conducive or adverse to the recruitment of envelope proteins.

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Single point mutation in tick-borne encephalitis virus prM protein induces a reduction of virus particle secretion

Journal of General Virology ◽

10.1099/vir.0.80169-0 ◽

2004 ◽

Vol 85 (10) ◽

pp. 3049-3058 ◽

Cited By ~ 36

Author(s):

Kentarou Yoshii ◽

Akihiro Konno ◽

Akiko Goto ◽

Junko Nio ◽

Mayumi Obara ◽

...

Keyword(s):

Point Mutation ◽

Single Point ◽

Expression System ◽

Envelope Proteins ◽

Viral Envelope ◽

Single Point Mutation ◽

Virus Envelope ◽

Electron Microscopic ◽

Transport Pathway ◽

Tick Borne Encephalitis

Flaviviruses are assembled to bud into the lumen of the endoplasmic reticulum (ER) and are secreted through the vesicle transport pathway. Virus envelope proteins play important roles in this process. In this study, the effect of mutations in the envelope proteins of tick-borne encephalitis (TBE) virus on secretion of virus-like particles (VLPs), using a recombinant plasmid expression system was analysed. It was found that a single point mutation at position 63 in prM induces a reduction in secretion of VLPs. The mutation in prM did not affect the folding of the envelope proteins, and chaperone-like activity of prM was maintained. As observed by immunofluorescence microscopy, viral envelope proteins with the mutation in prM were scarce in the Golgi complex, and accumulated in the ER. Electron microscopic analysis of cells expressing the mutated prM revealed that many tubular structures were present in the lumen. The insertion of the prM mutation at aa 63 into the viral genome reduced the production of infectious virus particles. This data suggest that prM plays a crucial role in the virus budding process.

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PL-4 Expression of hepatitis C virus envelope proteins in transgenic mice

International Hepatology Communications ◽

10.1016/0928-4346(95)90175-7 ◽

1995 ◽

Vol 3 ◽

pp. S2

Author(s):

K KOIKE

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Transgenic Mice ◽

Envelope Proteins ◽

Virus Envelope

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Characterization of two engineered dimeric Zika virus envelope proteins as immunogens for neutralizing antibody selection and vaccine design

Journal of Biological Chemistry ◽

10.1074/jbc.ra119.007443 ◽

2019 ◽

Vol 294 (27) ◽

pp. 10638-10648 ◽

Cited By ~ 3

Author(s):

Chunpeng Yang ◽

Fang Zeng ◽

Xinyu Gao ◽

Shaojuan Zhao ◽

Xuan Li ◽

...

Keyword(s):

Zika Virus ◽

Vaccine Design ◽

Neutralizing Antibody ◽

Envelope Proteins ◽

Virus Envelope

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Analysis of the Cytosolic Domains of the Hepatitis B Virus Envelope Proteins for Their Function in Viral Particle Assembly and Infectivity

Journal of Virology ◽

10.1128/jvi.00621-06 ◽

2006 ◽

Vol 80 (24) ◽

pp. 11935-11945 ◽

Cited By ~ 43

Author(s):

Matthieu Blanchet ◽

Camille Sureau

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Self Assembly ◽

Inner Core ◽

Envelope Proteins ◽

Endoplasmic Reticulum Membrane ◽

Virus Envelope ◽

Particle Assembly ◽

B Virus

ABSTRACT The hepatitis B virus (HBV) envelope proteins have the ability to assemble three types of viral particles, (i) the empty subviral particles (SVPs), (ii) the mature HBV virions, and (iii) the hepatitis delta virus (HDV) particles, in cells that are coinfected with HBV and HDV. To gain insight into the function of the HBV envelope proteins in morphogenesis of HBV or HDV virions, we have investigated subdomains of the envelope proteins that have been shown or predicted to lie at the cytosolic face of the endoplasmic reticulum membrane during synthesis, a position prone to interaction with the inner core structure. These domains, referred to here as cytosolic loops I and II (CYL-I and -II, respectively), were subjected to mutagenesis. The mutations were introduced in the three HBV envelope proteins, designated small, middle, and large (S-HBsAg, M-HBsAg, and L-HBsAg, respectively). The mutants were expressed in HuH-7 cells to evaluate their capacity for self-assembly and formation of HBV or HDV virions when HBV nucleocapsid or HDV ribonucleoprotein, respectively, was provided. We found that SVP-competent CYL-I mutations between positions 23 and 78 of the S domain were permissive to HBV or HDV virion assembly. One mutation (P29A) was permissive for synthesis of the S- and M-HBsAg but adversely affected the synthesis or stability of L-HBsAg, thereby preventing the assembly of HBV virions. Furthermore, using an in vitro infection assay based on the HepaRG cells and the HDV model, we have shown that particles coated with envelope proteins bearing CYL-I mutations were fully infectious, hence indicating the absence of an infectivity determinant in this region. Finally, we demonstrated that the tryptophan residues at positions 196, 199, and 201 in CYL-II, which were shown to exert a matrix function for assembly of HDV particles (I. Komla-Soukha and C. Sureau, J. Virol. 80:4648-4655, 2006), were dispensable for both assembly and infectivity of HBV virions.

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Functional Analysis of Hepatitis C Virus Envelope Proteins, Using a Cell-Cell Fusion Assay

Journal of Virology ◽

10.1128/jvi.80.4.1817-1825.2006 ◽

2006 ◽

Vol 80 (4) ◽

pp. 1817-1825 ◽

Cited By ~ 29

Author(s):

Mariko Kobayashi ◽

Michael C. Bennett ◽

Theodore Bercot ◽

Ila R. Singh

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Cell Fusion ◽

Viral Entry ◽

Antiviral Agents ◽

Cell Types ◽

Envelope Proteins ◽

Virus Envelope ◽

Host Cell Membrane ◽

Cell Cell

ABSTRACT Hepatitis C virus (HCV) envelope proteins mediate the entry of virus into cells by binding to cellular receptors, resulting in fusion of the viral membrane with the host cell membrane and permitting the viral genome to enter the cytoplasm. We report the development of a robust and reproducible cell-cell fusion assay using envelope proteins from commonly occurring genotypes of HCV. The assay scored HCV envelope protein-mediated fusion by the production of fluorescent green syncytia and allowed us to elucidate many aspects of HCV fusion, including the pH of fusion, cell types that permit viral entry, and the conformation of envelope proteins essential for fusion. We found that fusion could be specifically inhibited by anti-HCV antibodies and by at least one peptide. We also generated a number of insertional mutations in the envelope proteins and tested nine of these using the fusion assay. We demonstrate that this fusion assay is a powerful tool for understanding the mechanism of HCV-mediated fusion, elucidating mutant function, and testing antiviral agents.

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