Envelope Glycoprotein Incorporation, Not Shedding of Surface Envelope Glycoprotein (gp120/SU), Is the Primary Determinant of SU Content of Purified Human Immunodeficiency Virus Type 1 and Simian Immunodeficiency Virus

Chertova, Elena; Bess, Julian W.; Crise, Bruce; Sowder, Raymond C.; Schaden, Terra M.; Hilburn, Joanne M.; Hoxie, James A.; Benveniste, Raoul Ė.; Lifson, Jeffrey D.; Henderson, Louis E.; Arthur, Larry O.

doi:10.1128/jvi.76.11.5315-5325.2002

Cited by 262 publications

(277 citation statements)

References 55 publications

Supporting

Mentioning

248

Contrasting

Order By: Relevance

“…In the main, HIV is thought to assemble at the plasma membrane of T-cells. 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.…”

Section: Discussionmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Byland

Vance

Hoxie

et al. 2007

MBoC

Self Cite

123

133

View full text Add to dashboard Cite

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...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

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

Self Cite

123

133

View full text Add to dashboard Cite

show abstract

“…We used AT-2 HIV-1 viral preparations at a concentration of 3 g/ml Gag p24 Ag, which corresponds to an estimated gp120 concentration of 2 nM, given a Gag to gp120 ratio of ϳ60 (62). These data suggest that virion-associated gp120 can signal in the nanomolar range.…”

Section: Discussionmentioning

confidence: 99%

CXCR4-Tropic HIV-1 Envelope Glycoprotein Functions as a Viral Chemokine in Unstimulated Primary CD4+ T Lymphocytes

Balabanian

Harriague

Décrion

et al. 2004

The Journal of Immunology

View full text Add to dashboard Cite

Interaction of HIV-1 envelope glycoprotein gp120 with the chemokine receptor CXCR4 triggers not only viral entry but also an array of signal transduction cascades. Whether gp120 induces an incomplete or aberrant set of signals, or whether it can function as a full CXCR4 agonist, remains unclear. We report that, in unstimulated human primary CD4+ T cells, the spectrum of signaling responses induced by gp120 through CXCR4 paralleled that induced by the natural ligand stromal cell-derived factor 1/CXCL12. gp120 activated heterotrimeric G proteins and the major G protein-dependent pathways, including calcium mobilization, phosphoinositide-3 kinase, and Erk-1/2 MAPK activation. Interestingly, gp120 caused rapid actin cytoskeleton rearrangements and profuse membrane ruffling, as evidenced by dynamic confocal imaging. This coordinated set of events resulted in a bona fide chemotactic response. Inactivated HIV-1 virions that harbored conformationally intact envelope glycoproteins also caused actin polymerization and chemotaxis, while similar virions devoid of envelope glycoproteins did not. Thus gp120, in monomeric as well as oligomeric, virion-associated form, elicited a complex cellular response that mimicked the effects of a chemokine. HIV-1 has therefore the capacity to dysregulate the vast CD4+ T cell population that expresses CXCR4. In addition, HIV-1 may exploit its chemotactic properties to retain potential target cells and locally perturb their cytoskeleton, thereby facilitating viral transmission.

show abstract

“…The number of gp120/gp41 trimers per virion ranges between 10 and 100 depending on the isolate (10). HIV gp120 is ϳ50% carbohydrate and is one of the most glycosylated proteins known (11).…”

Section: The Virus and Its Targetmentioning

confidence: 99%

HIV Entry and Envelope Glycoprotein-mediated Fusion

Blumenthal

Durell

Viard

2012

Journal of Biological Chemistry

183

203

View full text Add to dashboard Cite

HIV entry involves binding of the trimeric viral envelope glycoprotein (Env) gp120/gp41 to cell surface receptors, which triggers conformational changes in Env that drive the membrane fusion reaction. The conformational landscape that the lipids and Env navigate en route to fusion has been examined by biophysical measurements on the microscale, whereas electron tomography, x-rays, and NMR have provided insights into the process on the nanoscale and atomic scale. However, the coupling between the lipid and protein pathways that give rise to fusion has not been resolved. Here, we discuss the known and unknown about the overall HIV Env-mediated fusion process. The Virus and Its TargetHIV virions exist as roughly spherical nanoparticles ϳ100 nm in diameter and are coated by the viral envelope membrane (1). The viral membrane is a lipid bilayer ϳ4 nm thick, interspersed with membrane-embedded glycoproteins. The HIV matrix protein Gag Pr55 drives viral assembly by recruiting all the building blocks, which include both viral and cellular components required for the formation of a fully infectious virion (2). A typical HIV viral membrane contains ϳ300,000 lipids, with a rather unique distribution of lipids compared with the lipid composition of cells from which it is derived (3,4). In addition to the virally encoded envelope glycoprotein gp120/ gp41, the HIV membrane also incorporates a plethora of cell membrane proteins in the process of assembly and budding (5). The HIV envelope proteins are expressed in the endoplasmic reticulum as a precursor protein, gp160, which transits the Golgi apparatus, where glycosylation is completed (6, 7). The precursor is cleaved in the trans-Golgi by the cellular protease furin into two proteins, gp120 and gp41 (8). These proteins are present on the cell surface as the envelope complex, a mushroomshaped trimer of heterodimers of gp120 and gp41, incorporated into the viral envelope through the transmembrane region of gp41 as virus particles bud from the cell surface (9).The number of gp120/gp41 trimers per virion ranges between 10 and 100 depending on the isolate (10). HIV gp120 is ϳ50% carbohydrate and is one of the most glycosylated proteins known (11). The number of accessory HIV membrane proteins has, in general, not been determined, with the exception of HLA class II in HIV-1 MN derived from H9 cells, which has ϳ50 native HLA class II complexes (12). The lipids and proteins are glycoconjugated, providing an additional shield for HIV against immune and environmental challenges. The viral genome is thus comfortably ensconced in a wrapper of lipid and protein covered by carbohydrate. However, mannose-type carbohydrates on HIV are recognized by DC-SIGN (dendritic cellspecific intercellular adhesion molecule-3-grabbing non-integrin), which is a C-type lectin receptor present on dendritic cells (13). The dendritic cells internalize HIV-DC-SIGN complexes and migrate to the lymph nodes, where they interact with T cells. The HIV-DC-SIGN complexes are then recycled to the cell periphery, and ...

show abstract

Envelope Glycoprotein Incorporation, Not Shedding of Surface Envelope Glycoprotein (gp120/SU), Is the Primary Determinant of SU Content of Purified Human Immunodeficiency Virus Type 1 and Simian Immunodeficiency Virus

Cited by 262 publications

References 55 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

CXCR4-Tropic HIV-1 Envelope Glycoprotein Functions as a Viral Chemokine in Unstimulated Primary CD4+ T Lymphocytes

HIV Entry and Envelope Glycoprotein-mediated Fusion

Contact Info

Product

Resources

About