Modulation of Env Content in Virions of Simian Immunodeficiency Virus: Correlation with Cell Surface Expression and Virion Infectivity

Yuste, Eloísa; Reeves, Jacqueline D.; Doms, Robert W.; Desrosiers, Ronald C.

doi:10.1128/jvi.78.13.6775-6785.2004

Cited by 86 publications

(120 citation statements)

References 60 publications

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“…The finding that endocytosis signals function to maintain low levels of Env on the cell surface may explain why HIV particles collected from cultured T-cell lines have relatively low Env levels (average 7-10 spikes/virion; Chertova et al, 2002;Zhu et al, 2003). In addition, the levels of Env expression on the cell surface and on virions could be a determinant for host humoral immune responses and viral evasion (Yuste et al, 2004(Yuste et al, , 2005. In contrast, endocytosis signals may play a different role in infected macrophages where HIV assembles on intracellular membranes.…”

Section: Discussionmentioning

confidence: 99%

A Conserved Dileucine Motif Mediates Clathrin and AP-2–dependent Endocytosis of the HIV-1 Envelope Protein

Byland

Vance

Hoxie

et al. 2007

MBoC

124

133

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During the assembly of enveloped viruses viral and cellular components essential for infectious particles must colocalize at specific membrane locations. For the human and simian immunodeficiency viruses (HIV and SIV), sorting of the viral envelope proteins (Env) to assembly sites is directed by trafficking signals located in the cytoplasmic domain of the transmembrane protein gp41 (TM). A membrane proximal conserved GYxxØ motif mediates endocytosis through interaction with the clathrin adaptor AP-2. However, experiments with SIV mac239 Env indicate the presence of additional signals. Here we show that a conserved C-terminal dileucine in HIV HxB2 also mediates endocytosis. Biochemical and morphological assays demonstrate that the C-terminal dileucine motif mediates internalization as efficiently as the GYxxØ motif and that both must be removed to prevent Env internalization. RNAi experiments show that depletion of the clathrin adaptor AP-2 leads to increased plasma membrane expression of HIV Env and that this adaptor is required for efficient internalization mediated by both signals. The redundancy of conserved endocytosis signals and the role of the SIV mac239 Env GYxxØ motif in SIV pathogenesis, suggest that these motifs have functions in addition to endocytosis, possibly related to Env delivery to the site of viral assembly and/or incorporation into budding virions. INTRODUCTIONThe assembly of enveloped animal viruses requires that the viral and cellular components needed to make infectious particles are brought to the same site within the infected cell at the same time. For the primate lentiviruses (the human immunodeficiency viruses types 1 and 2 [HIV-1 and -2] and the simian immunodeficiency viruses [SIV]) the key viral structural proteins required to generate infectious particles are Gag, Gag-Pol, and Env. Although Gag alone can promote the formation of virus-like particles, Env and Gag-Pol are both essential for the formation of infectious virions. Although a considerable amount is known about these proteins, little is understood of the mechanisms through which they are targeted to the sites of assembly in infected cells.In many cell types, HIV assembles at the plasma membrane and, in the course of Gag assembly, the particles derive their membrane from the plasma membrane. For these particles to be infectious, Env must be transported to the cell surface, but the level to which it is incorporated into budding virions is unclear. Recent data have suggested that fewer than 10 Env protein complexes (trimers) are incorporated per virion (Chertova et al., 2002;Zhu et al., 2003), and early studies of HIV infected T-cells showed that much of the newly synthesized Env is transported to lysosomes and degraded (Willey et al., 1988). However, it has recently become evident that in macrophages the assembly of Envcontaining infectious HIV occurs on intracellular membranes, that have some characteristics in common with late endosomes (Raposo et al., 2002;Pelchen-Matthews et al., 2003). The assembly of virus in distinct...

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Section: Discussionmentioning

confidence: 99%

A Conserved Dileucine Motif Mediates Clathrin and AP-2–dependent Endocytosis of the HIV-1 Envelope Protein

Byland

Vance

Hoxie

et al. 2007

MBoC

124

133

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“…This means that in the context of full-length HIV-Env, the tested heterologous SPs, which include an SP which, in contrast to the HIV-SP, is only very weakly charged (Epo-SP), do not lead to an increase in Env expression or particle incorporation levels. Since the extent of incorporation into particles is at least partially determined by the level of surface expression of retroviral glycoproteins [23], these analyses make it unlikely that the heterologous SPs increase HIV-Env transport to the cell surface. On the contrary, the decreased incorporation of Env from into pNL-tPA-SP particles would rather point to a deleterious effect, perhaps as a result of incomplete SP removal or to incorrect folding as a result of premature SP removal.…”

Section: Expression Of Proviral Constructs Encoding Env Proteins Withmentioning

confidence: 99%

Effects of signal peptide exchange on HIV‐1 glycoprotein expression and viral infectivity in mammalian cells

et al. 2006

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In certain cell systems, exchange of the human immunodeficiency virus (HIV) Env signal peptide (SP) sequence with that of heterologous SPs has been shown to increase gp120 transport and secretion. Here we demonstrate that exchange of the HIV-Env-SP with those from erythropoietin or tissue plasminogen activator in the proviral context does not increase wild-type membrane-bound Env expression or incorporation into released virions. In fact, virion infectivities were decreased. These infectivity decreases were largely due to effects on Env transport and/or function and only to a minor extent to cis effects as a result of the sequence exchanges themselves. Thus, in fact, it is not advantageous to employ heterologous SPs to achieve highlevel expression of functional cell surface membrane-or virionassociated HIV-Env.

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“…36 Other regions of gp41 have also been implicated in interacting with viral matrix proteins during virion assembly. 35 Published data indicate that point mutations or truncations in the CT of HIV or SIV can increase Env fusogenicity and surface expression, [8][9][10][11] whereas Env incorporation into virions can be increased or decreased. 10 In addition, CT truncations are also associated with CD4-independent infection of some HIV variants.…”

Section: Discussionmentioning

confidence: 99%

“…35 Published data indicate that point mutations or truncations in the CT of HIV or SIV can increase Env fusogenicity and surface expression, [8][9][10][11] whereas Env incorporation into virions can be increased or decreased. 10 In addition, CT truncations are also associated with CD4-independent infection of some HIV variants. 37 Our own data also suggest that the CT-truncated gp41 mediates cell-cell fusion as well as or superior to its full-length counterpart (data not shown).…”

Section: Discussionmentioning

confidence: 99%

“…However, published data suggest that HIV or SIV variants with a truncated cytoplasmic domain of gp41 increase in Env fusogenicity. [8][9][10][11] There has been a growing interest in new anti-HIV agents to tackle the increasing problems of multidrug resistance. Host and viral molecules involved in various stages of HIV entry have been explored as novel targets for the discovery of anti-HIV agents.…”

mentioning

confidence: 99%

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Development of a Moloney Murine Leukemia Virus–Based Pseudotype Anti-HIV Assay Suitable for Accurate and Rapid Evaluation of HIV Entry Inhibitors

Chan¹,

Heilek-Snyder²,

Cammack³

et al. 2006

SLAS Discovery

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There has been increasing interest in the identification of novel HIV entry inhibitors. For the discovery of these entry inhibitors, robust surrogate anti-HIV assays are highly desired. The authors report a novel anti-HIV assay system using Moloney murine leukemia viruses (MMLVs) pseudotyped with cytoplasmic tail-truncated HIV envelope protein gp140. These pseudotyped MMLV-HIVgp140 viral particles carry luciferase transcripts; therefore, robust luciferase signal can be detected in cells infected by these pseudotypes. Polycationic agent polybrene and spinoculation markedly enhanced the infection efficiency of these pseudotypes. It was demonstrated that the tropism of these pseudotypes is dependent on the pseudotyped HIV envelope proteins. MMLV viruses pseudotyped with gp140 from an R5 HIV virus specifically infect CCR5-expressing cells, and viruses pseudotyped with gp140 from an X4 HIV virus specifically infect CXCR4-expressing cells. Furthermore, CCR5 antagonists inhibited only MMLV-gp140(R5) infections, and CXCR4 antagonists inhibited only MMLV-gp140(X4) infections. A variety of known HIV entry inhibitors were tested in both R5-and X4-dependent pseudotype antiviral assays, and the IC 50 values generated were consistent with published results. The pseudotype antiviral assay was also used in the characterization of hundreds of novel CCR5 antagonists. The IC 50 values determined in this assay were compared with those determined in HIV antiviral and cell-cell fusion (CCF) assays, and good correlation was found between pseudotype antiviral assay and HIV antiviral assay (R 2 = 0.9) or CCF assay (R 2 = 0.8). (Journal of Biomolecular Screening 2006:652-663)

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Modulation of Env Content in Virions of Simian Immunodeficiency Virus: Correlation with Cell Surface Expression and Virion Infectivity

Cited by 86 publications

References 60 publications

A Conserved Dileucine Motif Mediates Clathrin and AP-2–dependent Endocytosis of the HIV-1 Envelope Protein

A Conserved Dileucine Motif Mediates Clathrin and AP-2–dependent Endocytosis of the HIV-1 Envelope Protein

Effects of signal peptide exchange on HIV‐1 glycoprotein expression and viral infectivity in mammalian cells

Development of a Moloney Murine Leukemia Virus–Based Pseudotype Anti-HIV Assay Suitable for Accurate and Rapid Evaluation of HIV Entry Inhibitors

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