Compensatory Link between Fusion and Endocytosis of Human Immunodeficiency Virus Type 1 in Human CD4 T Lymphocytes

Schaeffer, Evelyne; Soros, Vanessa B.; Greene, Warner C.

doi:10.1128/jvi.78.3.1375-1383.2004

Cited by 104 publications

(115 citation statements)

References 34 publications

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“…Upon HIV-1 engagement of CD4, as the pool of coreceptors reside in a phase-separated domain; infectivity is reduced due to the low probability of coreceptor engagement. This perturbation of membrane structure may result in the trafficking of virions via an endocytic pathway that leads to nonproductive infection (25). Future studies are warranted to test this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

Ceramide, a target for antiretroviral therapy

Finnegan

Rawat

Puri

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

100

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Section: Discussionmentioning

confidence: 99%

Ceramide, a target for antiretroviral therapy

Finnegan

Rawat

Puri

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

100

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“…41,42,75 This could be important, since several lines of evidence imply that productive HIV-1 entry into cells occurs through an endocytic route. 41,42,52,[76][77][78][79] Furthermore, cell fusion-based assays are generally not sensitive to inhibitors that inactivate diverse enveloped viruses through disrupting their membrane, while having no adverse effect on cell membranes. 39,40 Our observation that P2X1 receptor antagonists inhibit HIV-1 fusion is in agreement with the literature.…”

Section: Discussionmentioning

confidence: 99%

High-Throughput HIV–Cell Fusion Assay for Discovery of Virus Entry Inhibitors

Marin

Giroud

et al. 2015

ASSAY and Drug Development Technologies

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HIV-1 initiates infection by merging its envelope membrane with the target cell membrane, a process that is mediated by the viral Env glycoprotein following its sequential binding to CD4 and coreceptors, CXCR4 or CCR5. Although HIV-1 fusion has been a target for antiviral therapy, the virus has developed resistance to drugs blocking the CCR5 binding or Env refolding steps of this process. This highlights the need for novel inhibitors. Here, we adapted and optimized an enzymatic HIV-cell fusion assay, which reports the transfer of virus-encapsulated b-lactamase into the cytoplasm, to high-throughput screening (HTS) with a 384-well format. The assay was robustly performed in HTS format and was validated by the pilot screen of a small library of pharmacologically active compounds. Several hits identified by screening included a prominent cluster of purinergic receptor antagonists. Functional studies demonstrated that P2X1 receptor antagonists selectively inhibited HIV-1 fusion without affecting the fusion activity of an unrelated virus that enters cells through an endocytic route. The inhibition of HIV-cell fusion by P2X1 antagonists was not through downmodulation of the cell surface expression of CD4 or coreceptors, thus implicating P2X1 receptor in the HIV-1 fusion step. The ability of these antagonists to inhibit viruses regardless of their coreceptor (CXCR4 or CCR5) preference indicates that fusion is blocked at a late step downstream of coreceptor binding. A future large-scale screening campaign for HIV-1 fusion inhibitors, using the above functional readout, will likely reveal novel classes of inhibitors and suggest potential targets for antiviral therapy.

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“…Inhibitors of dynaminand clathrin-dependent endocytosis (62, 65) have been invoked to argue for HIV entry via endocytosis, but such inhibitors have multifaceted effects on cellular processes, including cell-cell fusion (66). Endosomal acidification inhibitors could prevent degradation and allow endocytic fusion at neutral pH, but enhanced endocytosis causes lysosomal degradation of HIV (67,68). Interestingly "fusion from without" has been used as a measure of virus-cell fusion, which is followed by Env-induced cell fusion (69).…”

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confidence: 99%

HIV Entry and Envelope Glycoprotein-mediated Fusion

Blumenthal

Durell

Viard

2012

Journal of Biological Chemistry

186

203

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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 ...

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Compensatory Link between Fusion and Endocytosis of Human Immunodeficiency Virus Type 1 in Human CD4 T Lymphocytes

Cited by 104 publications

References 34 publications

Ceramide, a target for antiretroviral therapy

Ceramide, a target for antiretroviral therapy

High-Throughput HIV–Cell Fusion Assay for Discovery of Virus Entry Inhibitors

HIV Entry and Envelope Glycoprotein-mediated Fusion

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