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Movements of HIV-1 genomic RNA-APOBEC3F complexes and PKR reveal cytoplasmic and nuclear PKR defenses and HIV-1 evasion strategies. Virus Res 2016; 213:124-139. [PMID: 26626364 DOI: 10.1016/j.virusres.2015.11.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/21/2015] [Accepted: 11/21/2015] [Indexed: 11/22/2022]
Abstract
APOBEC3 cytidine deaminases and viral genomic RNA (gRNA) occur in virions, polysomes, and cytoplasmic granules, but have not been tracked together. Moreover, gRNA traffic is important, but the factors that move it into granules are unknown. Using in situ hybridization of transfected cells and protein synthesis inhibitors that drive mRNAs between locales, we observed APOBEC3F cotrafficking with gRNA without altering its movements. Whereas cells with little cytoplasmic gRNA were translationally active and accumulated Gag, suprathreshold amounts induced autophosphorylation of the cytoplasmic double-stranded RNA (dsRNA)-dependent protein kinase (PKR), causing eIF2α phosphorylation, protein synthesis suppression, and gRNA sequestration in stress granules. Additionally, we confirmed recent evidence that PKR is activated by chromosome-associated cellular dsRNAs after nuclear membranes disperse in prophase. By arresting cells in G2, HIV-1 blocks this mechanism for PKR activation and eIF2α phosphorylation. However, cytopathic membrane damage in CD4- and coreceptor-positive cultures infected with laboratory-adapted fusogenic HIV-1LAI eventually enabled PKR entry and activation in interphase nuclei. These results reveal multiple stages in the PKR-HIV-1 battleground that culminate in cell death. We discuss evidence suggesting that HIV-1s evolve in vivo to prevent or delay PKR activation by all these mechanisms.
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Rostami M, Sirous H, Zabihollahi R, Aghasadeghi MR, Sadat SM, Namazi R, Saghaie L, Memarian HR, Fassihi A. Design, synthesis and anti-HIV-1 evaluation of a series of 5-hydroxypyridine-4-one derivatives as possible integrase inhibitors. Med Chem Res 2015. [DOI: 10.1007/s00044-015-1443-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Sirous H, Zabihollahi R, Aghasadeghi MR, Sadat SM, Saghaie L, Fassihi A. Docking studies of some 5-hydroxypyridine-4-one derivatives: evaluation of integrase and ribonuclease H domain of reverse transcriptase as possible targets for anti-HIV-1 activity. Med Chem Res 2014. [DOI: 10.1007/s00044-014-1289-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Reversible and efficient activation of HIV-1 cell entry by a tyrosine-sulfated peptide dissects endocytic entry and inhibitor mechanisms. J Virol 2014; 88:4304-18. [PMID: 24478426 DOI: 10.1128/jvi.03447-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED HIV-1 membranes contain gp120-gp41 trimers. Binding of gp120 to CD4 and a coreceptor (CCR5 or CXCR4) reduces the constraint on metastable gp41, enabling a series of conformational changes that cause membrane fusion. An analytic difficulty occurs because these steps occur slowly and asynchronously within cohorts of adsorbed virions. We previously isolated HIV-1JRCSF variants that efficiently use CCR5 mutants severely damaged in the tyrosine-sulfated amino terminus or extracellular loop 2. Surprisingly, both independent adaptations included gp120 mutations S298N, F313L, and N403S, supporting other evidence that they function by weakening gp120's grip on gp41 rather than by altering gp120 binding to specific CCR5 sites. Although several natural HIV-1 isolates reportedly use CCR5(Δ18) (CCR5 with a deletion of 18 N-terminal amino acids, including the tyrosine-sulfated region) when the soluble tyrosine-sulfated peptide is present, we show that HIV-1JRCSF with the adaptive mutations [HIV-1JRCSF(Ad)] functions approximately 100 times more efficiently and that coreceptor activation is reversible, enabling synchronous efficient entry control under physiological conditions. This system revealed that three-stranded gp41 folding intermediates susceptible to the inhibitor enfuvirtide form slowly and asynchronously on cell surface virions but resolve rapidly, with virions generally forming only one target. Adsorbed virions asynchronously and transiently become competent for entry at 37°C but are inactivated if the CCR5 peptide is absent during their window of opportunity. This competency is conferred by endocytosis, which results in inactivation if the peptide is absent. For both wild-type and adapted HIV-1 isolates, early gp41 refolding steps obligatorily occur on cell surfaces, whereas the final step(s) is endosomal. This system powerfully dissects HIV-1 entry and inhibitor mechanisms. IMPORTANCE We present a powerful means to reversibly and efficiently activate or terminate HIV-1 entry by adding or removing a tyrosine-sulfated CCR5 peptide from the culture medium. This system uses stable cell clones and a variant of HIV-1JRCSF with three adaptive mutations. It enabled us to show that CCR5 coreceptor activation is rapidly reversible and to dissect aspects of entry that had previously been relatively intractable. Our analyses elucidate enfuvirtide (T-20) function and suggest that HIV-1 virions form only one nonredundant membrane fusion complex on cell surfaces. Additionally, we obtained novel and conclusive evidence that HIV-1 entry occurs in an assembly line manner, with some steps obligatorily occurring on cell surfaces and with final membrane fusion occurring in endosomes. Our results were confirmed for wild-type HIV-1. Thus, our paper provides major methodological and mechanistic insights about HIV-1 infection.
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Aghasadeghi MR, Zabihollahi R, Sadat SM, Esfahani AF, Ashtiani SH, Namazi R, Kashanizadeh N, Azadmanesh K. Production and evaluation of immunologic characteristics of mzNL4-3, a non-infectious HIV-1 clone with a large deletion in the pol-Sequence. Mol Biol 2013. [DOI: 10.1134/s0026893313020027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Inhibiting early-stage events in HIV-1 replication by small-molecule targeting of the HIV-1 capsid. J Virol 2012; 86:8472-81. [PMID: 22647699 DOI: 10.1128/jvi.05006-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The HIV-1 capsid (CA) protein plays essential roles in both early and late stages of virl replication and has emerged as a novel drug target. We report hybrid structure-based virtual screening to identify small molecules with the potential to interact with the N-terminal domain (NTD) of HIV-1 CA and disrupt early, preintegration steps of the HIV-1 replication cycle. The small molecule 4,4'-[dibenzo[b,d]furan-2,8-diylbis(5-phenyl-1H-imidazole-4,2-diyl)]dibenzoic acid (CK026), which had anti-HIV-1 activity in single- and multiple-round infections but failed to inhibit viral replication in peripheral blood mononuclear cells (PBMCs), was identified. Three analogues of CK026 with reduced size and better drug-like properties were synthesized and assessed. Compound I-XW-053 (4-(4,5-diphenyl-1H-imidazol-2-yl)benzoic acid) retained all of the antiviral activity of the parental compound and inhibited the replication of a diverse panel of primary HIV-1 isolates in PBMCs, while displaying no appreciable cytotoxicity. This antiviral activity was specific to HIV-1, as I-XW-053 displayed no effect on the replication of SIV or against a panel of nonretroviruses. Direct interaction of I-XW-053 was quantified with wild-type and mutant CA protein using surface plasmon resonance and isothermal titration calorimetry. Mutation of Ile37 and Arg173, which are required for interaction with compound I-XW-053, crippled the virus at an early, preintegration step. Using quantitative PCR, we demonstrated that treatment with I-XW-053 inhibited HIV-1 reverse transcription in multiple cell types, indirectly pointing to dysfunction in the uncoating process. In summary, we have identified a CA-specific compound that targets and inhibits a novel region in the NTD-NTD interface, affects uncoating, and possesses broad-spectrum anti-HIV-1 activity.
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T-cell changes after a short-term exposure to maraviroc in HIV-infected patients are related to antiviral activity. J Infect 2011; 64:417-23. [PMID: 22227467 DOI: 10.1016/j.jinf.2011.12.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 12/23/2011] [Accepted: 12/24/2011] [Indexed: 11/21/2022]
Abstract
OBJECTIVES Analyze the short-term immunological effect directly attributable to MRV without interference of other drugs. METHODS MRV group included experienced HIV-infected patients undergoing an 8-day MRV monotherapy. A comparison population included naïve HIV-infected patients starting combined antiretroviral therapy (cART group). Absolute CD4(+) and CD8(+) T-cells and T-lymphocyte subsets were determined at day 0 and 8. RESULTS Fifty-nine patients who underwent MRV monotherapy and 28 naïve patients were analyzed. Forty-one patients in the MRV group experienced a significant viral load decrease (MRV positive subgroup). Virological response and CD4(+) T-cell change were comparable in the MRV positive and cART groups. CD8(+) T-cell increase in the MRV positive subgroup showed a trend toward superiority when compared with the cART group. T-lymphocyte subset changes showed a similar profile in the MRV positive and cART groups with a differential effect in the TemRA cells related to MRV. No immunological effect (absolute lymphocyte counts or subsets) was observed in patients without virological response to MRV. CONCLUSIONS MRV produced CD4(+) and CD8(+) T-cell gains related to antiviral activity and comparable or even superior in terms of CD8(+) T-cells to naïve patients starting cART. No immunological effect occurred in subjects without virological response to MRV.
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Gift SK, Zentner IJ, Schön A, McFadden K, Umashankara M, Rajagopal S, Contarino M, Duffy C, Courter JR, Zhang MY, Gershoni JM, Cocklin S, Dimitrov DS, Smith AB, Freire E, Chaiken IM. Conformational and structural features of HIV-1 gp120 underlying the dual receptor antagonism by cross-reactive neutralizing antibody m18. Biochemistry 2011; 50:2756-68. [PMID: 21351734 DOI: 10.1021/bi101160r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the interaction between cross-reactive HIV-1 neutralizing human monoclonal antibody m18 and HIV-1YU-2 gp120 in an effort to understand how this antibody inhibits the entry of virus into cells. m18 binds to gp120 with high affinity (KD≈5 nM) as measured by surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). SPR analysis further showed that m18 inhibits interactions of gp120 with both soluble CD4 and CD4-induced antibodies that have epitopes overlapping the coreceptor binding site. This dual receptor site antagonism, which occurs with equal potency for both inhibition effects, argues that m18 is not functioning as a mimic of CD4, in spite of the presence of a putative CD4-like loop formed by HCDR3 in the antibody. Consistent with this view, m18 was found to interact with gp120 in the presence of saturating concentrations of a CD4-mimicking small molecule gp120 inhibitor, suggesting that m18 does not require unoccupied CD4 Phe43 binding cavity residues of gp120. Thermodynamic analysis of the m18-gp120 interaction suggests that m18 stabilizes a conformation of gp120 that is unique from and less structured than the CD4-stabilized conformation. Conformational mutants of gp120 were studied for their impact on m18 interaction. Mutations known to disrupt the coreceptor binding region and to lead to complete suppression of 17b binding had minimal effects on m18 binding. This argues that energetically important epitopes for m18 binding lie outside the disrupted bridging sheet region used for 17b and coreceptor binding. In contrast, mutations in the CD4 region strongly affected m18 binding. Overall, the results obtained in this work argue that m18, rather than mimicking CD4 directly, suppresses both receptor binding site functions of HIV-1 gp120 by stabilizing a nonproductive conformation of the envelope protein. These results can be related to prior findings about the importance of conformational entrapment as a common mode of action for neutralizing CD4bs antibodies, with differences mainly in epitope utilization and the extent of gp120 structuring.
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Affiliation(s)
- Syna Kuriakose Gift
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
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Zhukovsky MA, Basmaciogullari S, Pacheco B, Wang L, Madani N, Haim H, Sodroski J. Thermal stability of the human immunodeficiency virus type 1 (HIV-1) receptors, CD4 and CXCR4, reconstituted in proteoliposomes. PLoS One 2010; 5:e13249. [PMID: 20967243 PMCID: PMC2954141 DOI: 10.1371/journal.pone.0013249] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 09/13/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The entry of human immunodeficiency virus (HIV-1) into host cells involves the interaction of the viral exterior envelope glycoprotein, gp120, and receptors on the target cell. The HIV-1 receptors are CD4 and one of two chemokine receptors, CCR5 or CXCR4. METHODOLOGY/PRINCIPAL FINDINGS We created proteoliposomes that contain CD4, the primary HIV-1 receptor, and one of the coreceptors, CXCR4. Antibodies against CD4 and CXCR4 specifically bound the proteoliposomes. CXCL12, the natural ligand for CXCR4, and the small-molecule CXCR4 antagonist, AMD3100, bound the proteoliposomes with affinities close to those associated with the binding of these molecules to cells expressing CXCR4 and CD4. The HIV-1 gp120 exterior envelope glycoprotein bound tightly to proteoliposomes expressing only CD4 and, in the presence of soluble CD4, bound weakly to proteoliposomes expressing only CXCR4. The thermal stability of CD4 and CXCR4 inserted into liposomes was examined. Thermal denaturation of CXCR4 followed second-order kinetics, with an activation energy (E(a)) of 269 kJ/mol (64.3 kcal/mol) and an inactivation temperature (T(i)) of 56°C. Thermal inactivation of CD4 exhibited a reaction order of 1.3, an E(a) of 278 kJ/mol (66.5 kcal/mol), and a T(i) of 52.2°C. The second-order denaturation kinetics of CXCR4 is unusual among G protein-coupled receptors, and may result from dimeric interactions between CXCR4 molecules. CONCLUSIONS/SIGNIFICANCE Our studies with proteoliposomes containing the native HIV-1 receptors allowed an examination of the binding of biologically important ligands and revealed the higher-order denaturation kinetics of these receptors. CD4/CXCR4-proteoliposomes may be useful for the study of virus-target cell interactions and for the identification of inhibitors.
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Affiliation(s)
- Mikhail A. Zhukovsky
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Structural Dynamics of (Bio)chemical Systems, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Stéphane Basmaciogullari
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Beatriz Pacheco
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Liping Wang
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Navid Madani
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Hillel Haim
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joseph Sodroski
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Pathology, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
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Psomas KC, Corbeau P, Reynes J. [CCR5 antagonists and HIV-1 infection: Bases and consequences of this therapeutic approach]. ACTA ACUST UNITED AC 2010; 12:27-41. [PMID: 32288525 PMCID: PMC7146793 DOI: 10.1016/j.antib.2010.01.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
La molécule CCR5 est un récepteur de chimiokines qui joue un rôle important en pathologie infectieuse : corécepteur des souches du VIH-1 à tropisme R5, il est également impliqué dans la défense immunitaire contre certains agents transmissibles. Les antagonistes de CCR5 constituent une nouvelle approche thérapeutique antirétrovirale. Trois inhibiteurs du CCR5 ont atteint les phases IIb et III de développement clinique : aplaviroc (GlaxoSmithKine), vicriviroc (Schering-Plough) et maraviroc (Pfizer). Le développement de l’aplaviroc a été interrompu pour toxicité hépatique. Les essais ACTG 5211 et Motivate ont démontré une amélioration de la réponse antirétrovirale par l’addition respectivement de vicriviroc (actuellement en phase III) et de maraviroc (ayant déjà obtenu l’Autorisation de Mise sur le Marché) à un traitement optimisé chez des patients en échec thérapeutique. Le rôle de cette nouvelle cible thérapeutique dans les stratégies de traitement initial, de substitution ou de sauvetage reste à préciser, de même que leur intérêt chez des patients ayant une réponse immunovirologique dissociée, en immunodépresssion sévère ou infectés par des souches à tropisme non-R5. Plusieurs points sont également à éclaircir comme la tolérance à long terme, le risque d’induire une commutation R5-X4, en particulier dans les tissus, le risque d’interférer avec les réponses immunitaires, ainsi que l’impact d’une discordance de tropisme entre le plasma et les autres compartiments de l’organisme.
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Affiliation(s)
- K C Psomas
- Institut de génétique humaine, CNRS, 142, rue de la Cardonille, 34396 Montpellier cedex 5, France.,Service des maladies infectieuses et tropicales, CHU Gui-de-Chauliac, 80, avenue Augustin-Fliche, 34295 Montpellier cedex 5, France
| | - P Corbeau
- Institut de génétique humaine, CNRS, 142, rue de la Cardonille, 34396 Montpellier cedex 5, France.,Fonctionnelle d'immunologie, hôpital Carémeau, place du Pr-Robert-Debré, 30029 Nîmes cedex, France.,Faculté de médecine, université Montpellier 1, 2, rue École-de-Médecine, 34060 Montpellier cedex 2, France
| | - J Reynes
- Faculté de médecine, université Montpellier 1, 2, rue École-de-Médecine, 34060 Montpellier cedex 2, France.,Service des maladies infectieuses et tropicales, CHU Gui-de-Chauliac, 80, avenue Augustin-Fliche, 34295 Montpellier cedex 5, France.,UMR 145, 911, avenue Agropolis, 34394 Montpellier cedex 5, France
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Rapid dissociation of HIV-1 from cultured cells severely limits infectivity assays, causes the inactivation ascribed to entry inhibitors, and masks the inherently high level of infectivity of virions. J Virol 2009; 84:3106-10. [PMID: 20042508 DOI: 10.1128/jvi.01958-09] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By using immunofluorescence microscopy to observe and analyze freshly made HIV-1 virions adsorbed onto cells, we found that they are inherently highly infectious, rather than predominantly defective as previously suggested. Surprisingly, polycations enhance titers 20- to 30-fold by stabilizing adsorption and preventing a previously undescribed process of rapid dissociation, strongly implying that infectivity assays for many viruses are limited not only by inefficient virus diffusion onto cells but also by a postattachment race between entry and dissociation. This kinetic competition underlies inhibitory effects of CCR5 antagonists and explains why adaptive HIV-1 mutations overcome many cell entry limitations by accelerating entry.
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Poizot-Martin I. [Impact of a new family among the therapeutic strategies: the clinician's point of view]. Med Mal Infect 2009; 39:H10-2. [PMID: 19837345 DOI: 10.1016/s0399-077x(09)75323-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- I Poizot-Martin
- Service d'Immuno-hématologie Clinique, Centre d'Informations et de Soins de l'Immunodéficience Humaine, Hôpital Sainte-Marguerite, Assistance-publique-Hôpitaux de Marseille, 270, boulevard de Sainte-Marguerite, 13009 Marseille, France
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Haim H, Si Z, Madani N, Wang L, Courter JR, Princiotto A, Kassa A, DeGrace M, McGee-Estrada K, Mefford M, Gabuzda D, Smith AB, Sodroski J. Soluble CD4 and CD4-mimetic compounds inhibit HIV-1 infection by induction of a short-lived activated state. PLoS Pathog 2009; 5:e1000360. [PMID: 19343205 PMCID: PMC2655723 DOI: 10.1371/journal.ppat.1000360] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 03/02/2009] [Indexed: 11/19/2022] Open
Abstract
Binding to the CD4 receptor induces conformational changes in the human immunodeficiency virus (HIV-1) gp120 exterior envelope glycoprotein. These changes allow gp120 to bind the coreceptor, either CCR5 or CXCR4, and prime the gp41 transmembrane envelope glycoprotein to mediate virus–cell membrane fusion and virus entry. Soluble forms of CD4 (sCD4) and small-molecule CD4 mimics (here exemplified by JRC-II-191) also induce these conformational changes in the HIV-1 envelope glycoproteins, but typically inhibit HIV-1 entry into CD4-expressing cells. To investigate the mechanism of inhibition, we monitored at high temporal resolution inhibitor-induced changes in the conformation and functional competence of the HIV-1 envelope glycoproteins that immediately follow engagement of the soluble CD4 mimics. Both sCD4 and JRC-II-191 efficiently activated the envelope glycoproteins to mediate infection of cells lacking CD4, in a manner dependent on coreceptor affinity and density. This activated state, however, was transient and was followed by spontaneous and apparently irreversible changes of conformation and by loss of functional competence. The longevity of the activated intermediate depended on temperature and the particular HIV-1 strain, but was indistinguishable for sCD4 and JRC-II-191; by contrast, the activated intermediate induced by cell-surface CD4 was relatively long-lived. The inactivating effects of these activation-based inhibitors predominantly affected cell-free virus, whereas virus that was prebound to the target cell surface was mainly activated, infecting the cells even at high concentrations of the CD4 analogue. These results demonstrate the ability of soluble CD4 mimics to inactivate HIV-1 by prematurely triggering active but transient intermediate states of the envelope glycoproteins. This novel strategy for inhibition may be generally applicable to high–potential-energy viral entry machines that are normally activated by receptor binding. Human immunodeficiency virus type 1 (HIV-1) is the cause of the global AIDS epidemic. HIV-1 gains entry into its target cells by fusing with the cell membrane, a process that begins with the interaction of the viral envelope glycoproteins with cell-surface receptors. HIV-1 uses two receptors on the target cell: CD4 and CCR5/CXCR4. Binding of the virus to the primary receptor, CD4, primes the viral envelope glycoproteins to mediate the fusion of the viral membrane and the membrane of the target cell. Soluble forms of the CD4 receptor and small molecules that mimic the effects of CD4 can inhibit virus infection; however, how this inhibition occurs is still unknown. In this report, we show that soluble mimics of CD4 inhibit HIV-1 infection by prematurely triggering the viral envelope glycoproteins. The unstable activated state of the virus lasts only a few minutes, after which the virus loses the ability to infect cells. This novel strategy for inhibition may be generally applicable to other viruses besides HIV-1, some of which are also activated by binding to their receptors.
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Affiliation(s)
- Hillel Haim
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zhihai Si
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Navid Madani
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Liping Wang
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joel R. Courter
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amy Princiotto
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Aemro Kassa
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marciella DeGrace
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kathleen McGee-Estrada
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Megan Mefford
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Dana Gabuzda
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Amos B. Smith
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Joseph Sodroski
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
- * E-mail:
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Engel A, Walter P. Membrane lysis during biological membrane fusion: collateral damage by misregulated fusion machines. ACTA ACUST UNITED AC 2008; 183:181-6. [PMID: 18852300 PMCID: PMC2568015 DOI: 10.1083/jcb.200805182] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In the canonical model of membrane fusion, the integrity of the fusing membranes is never compromised, preserving the identity of fusing compartments. However, recent molecular simulations provided evidence for a pathway to fusion in which holes in the membrane evolve into a fusion pore. Additionally, two biological membrane fusion models-yeast cell mating and in vitro vacuole fusion-have shown that modifying the composition or altering the relative expression levels of membrane fusion complexes can result in membrane lysis. The convergence of these findings showing membrane integrity loss during biological membrane fusion suggests new mechanistic models for membrane fusion and the role of membrane fusion complexes.
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Affiliation(s)
- Alex Engel
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
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Platt EJ, Durnin JP, Shinde U, Kabat D. An allosteric rheostat in HIV-1 gp120 reduces CCR5 stoichiometry required for membrane fusion and overcomes diverse entry limitations. J Mol Biol 2007; 374:64-79. [PMID: 17920626 DOI: 10.1016/j.jmb.2007.09.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 08/09/2007] [Accepted: 09/04/2007] [Indexed: 10/22/2022]
Abstract
Binding of the human immunodeficiency virus (HIV-1) envelope glycoprotein gp120 to the CCR5 co-receptor reduces constraints on the metastable transmembrane subunit gp41, thereby enabling gp41 refolding, fusion of viral and cellular membranes, and infection. We previously isolated adapted HIV-1(JRCSF) variants that more efficiently use mutant CCR5s, including CCR5(Delta18) lacking the important tyrosine sulfate-containing amino terminus. Effects of mutant CCR5 concentrations on HIV-1 infectivities were highly cooperative, implying that several may be required. However, because wild-type CCR5 efficiently mediates infections at trace concentrations that were difficult to measure accurately, analyses of its cooperativity were not feasible. New HIV-1(JRCSF) variants efficiently use CCR5(HHMH), a chimera containing murine extracellular loop 2. The adapted virus induces large syncytia in cells containing either wild-type or mutant CCR5s and has multiple gp120 mutations that occurred independently in CCR5(Delta18)-adapted virus. Accordingly, these variants interchangeably use CCR5(HHMH) or CCR5(Delta18). Additional analyses strongly support a novel energetic model for allosteric proteins, implying that the adaptive mutations reduce quaternary constraints holding gp41, thus lowering the activation energy barrier for membrane fusion without affecting bonds to specific CCR5 sites. In accordance with this mechanism, highly adapted HIV-1s require only one associated CCR5(HHMH), whereas poorly adapted viruses require several. However, because they are allosteric ensembles, complexes with additional co-receptors fuse more rapidly and efficiently than minimal ones. Similarly, wild-type HIV-1(JRCSF) is highly adapted to wild-type CCR5 and minimally requires one. The adaptive mutations cause resistances to diverse entry inhibitors and cluster appropriately in the gp120 trimer interface overlying gp41. We conclude that membrane fusion complexes are allosteric machines with an ensemble of compositions, and that HIV-1 adapts to entry limitations by gp120 mutations that reduce its allosteric hold on gp41. These results provide an important foundation for understanding the mechanisms that control membrane fusion and HIV-1's facile adaptability.
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Affiliation(s)
- Emily J Platt
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239, USA
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