Role of Glycosphingolipids in HIV-1 Entry: Requirement of Globotriosylceramide (Gb3) in CD4/CXCR4-dependent Fusion

We have recently shown that addition of human erythrocyte glycosphingolipids (GSL) to non-human CD4+ or GSL-depleted human CD4+ cells rendered those cells susceptible to gp120-gp41-mediated cell fusion (Puri et al., BBRC, 1998). One GSL fraction (Fraction 3) isolated from human erythrocyte GSL mixture exhibited the highest recovery of fusion following incorporation into CD4+ non-human and GSL-depleted HeLa-CD4 cells (HeLa-CD4/GSL-). Structural analysis of Fraction 3 showed that this GSL had identical head group as the known GSL, Gal(α1→4)Gal(β1→4)Glc-Ceramide (Gb3) (Puri et al., PNAS, 1998). Here we report that presence of Gb3 in CD4+/CXCR4+ cells but not CD4+/CXCR4- cells allows fusion with HIV-1Lai-envelope glycoprotein expressing cells (TF228). Therefore, Gb3 functions in conjunction with HIV-1 co-receptor, CXCR4 to promote fusion. We propose that Gb3 functions by recruiting CD4 and/or CXCR4 at the fusion site through structurally specific interactions.

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Human Erythrocyte Glycolipids Promote HIV-1 Envelope Glycoprotein-Mediated Fusion of CD4+Cells

Biochemical and Biophysical Research Communications ◽

10.1006/bbrc.1997.7941 ◽

1998 ◽

Vol 242 (1) ◽

pp. 219-225 ◽

Cited By ~ 27

Author(s):

Anu Puri ◽

Peter Hug ◽

Isabel Muñoz-Barroso ◽

Robert Blumenthal

Keyword(s):

Envelope Glycoprotein ◽

Human Erythrocyte ◽

Cd4 Cells ◽

Hiv 1

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Role of the Membrane-Spanning Domain of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein in Cell-Cell Fusion and Virus Infection

Journal of Virology ◽

10.1128/jvi.02666-07 ◽

2008 ◽

Vol 82 (11) ◽

pp. 5417-5428 ◽

Cited By ~ 59

Author(s):

Liang Shang ◽

Ling Yue ◽

Eric Hunter

Keyword(s):

Amino Acid ◽

Cell Fusion ◽

Viral Entry ◽

Envelope Glycoprotein ◽

Amino Acid Residues ◽

Immunodeficiency Virus ◽

Membrane Spanning ◽

Hiv 1

ABSTRACT The membrane-spanning domain (MSD) of the human immunodeficiency virus type 1 (HIV-1) gp41 glycoprotein is critical for its biological activity. Previous C-terminal truncation studies have predicted an almost invariant core structure of 12 amino acid residues flanked by basic amino acids in the HIV-1 MSD that function to anchor the glycoprotein in the lipid bilayer. To further understand the role of specific amino acids within the MSD core, we initially replaced the core region with 12 leucine residues and then constructed recovery-of-function mutants in which specific amino acid residues (including a GGXXG motif) were reintroduced. We show here that conservation of the MSD core sequence is not required for normal expression, processing, intracellular transport, and incorporation into virions of the envelope glycoprotein (Env). However, the amino acid composition of the MSD core does influence the ability of Env to mediate cell-cell fusion and plays a critical role in the infectivity of HIV-1. Replacement of conserved amino acid residues with leucine blocked virus-to-cell fusion and subsequent viral entry into target cells. This restriction could not be released by C-terminal truncation of the gp41 glycoprotein. These studies imply that the highly conserved core residues of the HIV Env MSD, in addition to serving as a membrane anchor, play an important role in mediating membrane fusion during viral entry.

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The mechanism by which molecules containing the HIV gp41 core-binding motif HXXNPF inhibit HIV-1 envelope glycoprotein-mediated syncytium formation

Biochemical Journal ◽

10.1042/bj20061275 ◽

2007 ◽

Vol 403 (3) ◽

pp. 565-571 ◽

Cited By ~ 15

Author(s):

Jing-He Huang ◽

Heng-Wen Yang ◽

Shuwen Liu ◽

Jing Li ◽

Shibo Jiang ◽

...

Keyword(s):

Envelope Glycoprotein ◽

Critical Role ◽

Syncytium Formation ◽

Phage Clone ◽

Fusion Process ◽

Binding Motif ◽

Active Core ◽

Different Temperatures ◽

Hiv 1

The HIV-1 gp41 (glycoprotein 41) core plays a critical role in fusion between the viral and target cell membranes. We previously identified a gp41 core-binding motif, HXXNPF, by screening the phage display peptide libraries. In the present study, we elucidated the mechanism of action of HXXNPF motif-containing molecules of different sizes, including the phage clone L7.8 (a selected positive phage clone), L7.8-g3p* (a 10–kDa fragment of the gene 3 protein) and JCH-4 (a peptide containing 13 residues of L7.8-g3p*), regarding their respective binding abilities to the six-helix bundle and inhibition on syncytium formation at different temperatures. We found that all of the HXXNPF motif-containing molecules could bind to the gp41 core, and that their binding sites may be located in the N-helix domain. L7.8-g3p* and JCH-4 effectively inhibited HIV-1 Env (envelope glycoprotein)-mediated syncytium formation at 37 °C, while the phage clone L7.8 showed no inhibition under the same conditions. However, at suboptimal temperature (31.5 °C), all of these HXXNPF motif-containing molecules were capable of inhibiting syncytium formation. These results suggest that these HXXNPF motif-containing molecules mainly bind to the gp41 core and stop the fusion process mediated by the fusion-active core, resulting in inhibition of HIV-1 fusion and entry. The HXXNPF motif-containing molecules may be used as probes for studying the role of the HIV-1 gp41 core in the late stage of the membrane-fusion process.

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Target of HIV-1 Envelope Glycoprotein gp120–Induced Hippocampal Neuron Damage: Role of Voltage-Gated K+ Channel Kv2.1

Viral Immunology ◽

10.1089/vim.2015.0020 ◽

2015 ◽

Vol 28 (9) ◽

pp. 495-503 ◽

Cited By ~ 7

Author(s):

Qing Zhu ◽

Xu Song ◽

Jing Zhou ◽

Yixin Wang ◽

Jianxun Xia ◽

...

Keyword(s):

Envelope Glycoprotein ◽

Hippocampal Neuron ◽

K Channel ◽

Voltage Gated ◽

Envelope Glycoprotein Gp120 ◽

Glycoprotein Gp120 ◽

Neuron Damage ◽

Hiv 1

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A Novel Role of Proline Oxidase in HIV-1 Envelope Glycoprotein-induced Neuronal Autophagy

Journal of Biological Chemistry ◽

10.1074/jbc.m115.652776 ◽

2015 ◽

Vol 290 (42) ◽

pp. 25439-25451 ◽

Cited By ~ 14

Author(s):

Jui Pandhare ◽

Sabyasachi Dash ◽

Bobby Jones ◽

Fernando Villalta ◽

Chandravanu Dash

Keyword(s):

Envelope Glycoprotein ◽

Proline Oxidase ◽

Hiv 1 ◽

Neuronal Autophagy

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The Polar Region of the HIV-1 Envelope Protein Determines Viral Fusion and Infectivity by Stabilizing the gp120-gp41 Association

Journal of Virology ◽

10.1128/jvi.02128-18 ◽

2019 ◽

Vol 93 (7) ◽

Cited By ~ 2

Author(s):

Wuxun Lu ◽

Shuliang Chen ◽

Jingyou Yu ◽

Ryan Behrens ◽

Joshua Wiggins ◽

...

Keyword(s):

Membrane Fusion ◽

Cell Fusion ◽

Viral Entry ◽

Polar Region ◽

Targeted Mutagenesis ◽

Target Cells ◽

Viral Fusion ◽

Underlying Mechanisms ◽

Hiv 1

ABSTRACT HIV-1 enters cells through binding between viral envelope glycoprotein (Env) and cellular receptors to initiate virus and cell fusion. HIV-1 Env precursor (gp160) is cleaved into two units noncovalently bound to form a trimer on virions, including a surface unit (gp120) and a transmembrane unit (gp41) responsible for virus binding and membrane fusion, respectively. The polar region (PR) at the N terminus of gp41 comprises 17 residues, including 7 polar amino acids. Previous studies suggested that the PR contributes to HIV-1 membrane fusion and infectivity; however, the precise role of the PR in Env-mediated viral entry and the underlying mechanisms remain unknown. Here, we show that the PR is critical for HIV-1 fusion and infectivity by stabilizing Env trimers. Through analyzing the PR sequences of 57,645 HIV-1 isolates, we performed targeted mutagenesis and functional studies of three highly conserved polar residues in the PR (S532P, T534A, and T536A) which have not been characterized previously. We found that single or combined mutations of these three residues abolished or significantly decreased HIV-1 infectivity without affecting viral production. These PR mutations abolished or significantly reduced HIV-1 fusion with target cells and also Env-mediated cell-cell fusion. Three PR mutations containing S532P substantially reduced gp120 and gp41 association, Env trimer stability, and increased gp120 shedding. Furthermore, S532A mutation significantly reduced HIV-1 infectivity and fusogenicity but not Env expression and cleavage. Our findings suggest that the PR of gp41, particularly the key residue S532, is structurally essential for maintaining HIV-1 Env trimer, viral fusogenicity, and infectivity. IMPORTANCE Although extensive studies of the transmembrane unit (gp41) of HIV-1 Env have led to a fusion inhibitor clinically used to block viral entry, the functions of different domains of gp41 in HIV-1 fusion and infectivity are not fully elucidated. The polar region (PR) of gp41 has been proposed to participate in HIV-1 membrane fusion in biochemical analyses, but its role in viral entry and infectivity remain unclear. In our effort to characterize three nucleotide mutations of an HIV-1 RNA element that partially overlaps the PR coding sequence, we identified a novel function of the PR that determines viral fusion and infectivity. We further demonstrated the structural and functional impact of six PR mutations on HIV-1 Env stability, viral fusion, and infectivity. Our findings reveal the previously unappreciated function of the PR and the underlying mechanisms, highlighting the important role of the PR in regulating HIV-1 fusion and infectivity.

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Molecular Cloning, Expression, and Biological Characterization of an HTLV-II Envelope Glycoprotein: HIV-1 Expression Is Permissive for HTLV-II-Induced Cell Fusion

AIDS Research and Human Retroviruses ◽

10.1089/aid.1993.9.849 ◽

1993 ◽

Vol 9 (9) ◽

pp. 849-860 ◽

Cited By ~ 13

Author(s):

BIN WANG ◽

MICHAEL G. AGADJANYAN ◽

VASANTHA SRIKANTAN ◽

KENNETH E. UGEN ◽

WILLIAM HALL ◽

...

Keyword(s):

Molecular Cloning ◽

Cell Fusion ◽

Envelope Glycoprotein ◽

Biological Characterization ◽

Hiv 1

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Role of Fas Ligand and Receptor in the Mechanism of T-Cell Depletion in Acquired Immunodeficiency Syndrome: Effect on CD4+ Lymphocyte Depletion and Human Immunodeficiency Virus Replication

Blood ◽

10.1182/blood.v89.4.1357 ◽

1997 ◽

Vol 89 (4) ◽

pp. 1357-1363 ◽

Cited By ~ 126

Author(s):

E.M. Sloand ◽

N.S. Young ◽

P. Kumar ◽

F.F. Weichold ◽

T. Sato ◽

...

Keyword(s):

Fas Ligand ◽

Cd4 Cells ◽

Fas Receptor ◽

Immunodeficiency Virus ◽

Acquired Immunodeficiency ◽

Fas L ◽

Immunodeficiency Syndrome ◽

Hiv 1 ◽

Normal Controls

Abstract Direct killing of CD4+ lymphocytes by human immunodeficiency virus-1 (HIV-1) probably cannot account for the magnitude of the loss of these cells during the course of HIV-1 infection. Experimental evidence supports a pathophysiologic role of the apoptotic process in depletion of CD4 cells in acquired immunodeficiency syndrome (AIDS). The Fas-receptor/Fas-ligand (Fas-R/Fas-L) system mediates signals for apoptosis of susceptible lymphocytes and lympoblastoid cell lines. A number of investigators have recently reported increased expression of the Fas receptor in individuals with HIV infection, along with increased sensitivity of their lymphocytes to anti-Fas antibody mimicking Fas ligand. We attempted to determine the role of Fas-mediated apoptosis in disease progression and viral replication. Increased Fas-receptor (CD95) expression on CD4+ and CD8+ lymphocytes was found in a large group of HIV-1–infected patients compared with normal controls; individuals with a diagnosis of AIDS and a history of opportunistic infection had significantly more Fas receptor expression than did asymptomatic HIV-infected persons and normal blood donor controls (P < .01). Triggering of the Fas-R by agonistic anti-Fas monoclonal antibody, CH11, was preferentially associated with apoptosis in the CD4+ cells; this effect was more pronounced in lymphocytes derived from HIV+ individuals. Soluble and membrane-bound forms of Fas-L were produced in greater amounts in peripheral blood mononuclear cells (PBMC) cultures and in plasma obtained from HIV-1–infected persons than from normal controls. Furthermore, triggering of lymphocytes from HIV-infected persons by CH11 increased levels of interleukin-1β converting enzyme (ICE), a protein associated with apoptosis. When PBMC were cultured in the presence of CH11, p24 production per number of viable cells was decreased as compared with the same PBMC without CH11 (P < .01). These findings suggest that multiple mechanisms, including increased production of Fas-L by infected PBMC, increased Fas-R expression, and induction of a protease of ICE family, may play roles in the apoptotic depletion of CD4+ cells in HIV infection.

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