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Kleinpeter AB, Zhu Y, Mallery DL, Ablan SD, Chen L, Hardenbrook N, Saiardi A, James LC, Zhang P, Freed EO. The Effect of Inositol Hexakisphosphate on HIV-1 Particle Production and Infectivity can be Modulated by Mutations that Affect the Stability of the Immature Gag Lattice. J Mol Biol 2023; 435:168037. [PMID: 37330292 PMCID: PMC10544863 DOI: 10.1016/j.jmb.2023.168037] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 02/24/2023] [Accepted: 02/25/2023] [Indexed: 06/19/2023]
Abstract
The assembly of an HIV-1 particle begins with the construction of a spherical lattice composed of hexamer subunits of the Gag polyprotein. The cellular metabolite inositol hexakisphosphate (IP6) binds and stabilizes the immature Gag lattice via an interaction with the six-helix bundle (6HB), a crucial structural feature of Gag hexamers that modulates both virus assembly and infectivity. The 6HB must be stable enough to promote immature Gag lattice formation, but also flexible enough to be accessible to the viral protease, which cleaves the 6HB during particle maturation. 6HB cleavage liberates the capsid (CA) domain of Gag from the adjacent spacer peptide 1 (SP1) and IP6 from its binding site. This pool of IP6 molecules then promotes the assembly of CA into the mature conical capsid that is required for infection. Depletion of IP6 in virus-producer cells results in severe defects in assembly and infectivity of wild-type (WT) virions. Here we show that in an SP1 double mutant (M4L/T8I) with a hyperstable 6HB, IP6 can block virion infectivity by preventing CA-SP1 processing. Thus, depletion of IP6 in virus-producer cells markedly increases M4L/T8I CA-SP1 processing and infectivity. We also show that the introduction of the M4L/T8I mutations partially rescues the assembly and infectivity defects induced by IP6 depletion on WT virions, likely by increasing the affinity of the immature lattice for limiting IP6. These findings reinforce the importance of the 6HB in virus assembly, maturation, and infection and highlight the ability of IP6 to modulate 6HB stability.
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Affiliation(s)
- Alex B Kleinpeter
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA. https://twitter.com/AlexKleinpeter
| | - Yanan Zhu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Donna L Mallery
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Sherimay D Ablan
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Long Chen
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Nathan Hardenbrook
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Adolfo Saiardi
- Laboratory for Molecular Cell Biology, University College London, London, UK. https://twitter.com/SaiardiLab
| | - Leo C James
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK. https://twitter.com/JamesLab9
| | - Peijun Zhang
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK; Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, Oxford OX3 7BN, UK
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
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Juntit OA, Sornsuwan K, Wisitponchai T, Sanghiran Lee V, Sakkhachornphop S, Yasamut U, Tayapiwatana C. Dimeric Ankyrin with Inverted Module Promotes Bifunctional Property in Capturing Capsid to Impede HIV-1 Replication. Int J Mol Sci 2023; 24:ijms24065266. [PMID: 36982337 PMCID: PMC10048781 DOI: 10.3390/ijms24065266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/02/2023] [Accepted: 03/07/2023] [Indexed: 03/12/2023] Open
Abstract
Several anti-HIV scaffolds have been proposed as complementary treatments to highly active antiretroviral therapy. AnkGAG1D4, a designed ankyrin repeat protein, formerly demonstrated anti-HIV-1 replication by interfering with HIV-1 Gag polymerization. However, the improvement of the effectiveness was considered. Recently, the dimeric molecules of AnkGAG1D4 were accomplished in enhancing the binding activity against HIV-1 capsid (CAp24). In this study, the interaction of CAp24 against the dimer conformations was elucidated to elaborate the bifunctional property. The accessibility of the ankyrin binding domains was inspected by bio-layer interferometry. By inverting the second module of dimeric ankyrin (AnkGAG1D4NC-CN), the CAp24 interaction KD was significantly reduced. This reflects the capability of AnkGAG1D4NC-CN in simultaneously capturing CAp24. On the contrary, the binding activity of dimeric AnkGAG1D4NC-NC was indistinguishable from the monomeric AnkGAG1D4. The bifunctional property of AnkGAG1D4NC-CN was subsequently confirmed in the secondary reaction with additional p17p24. This data correlates with the MD simulation, which suggested the flexibility of the AnkGAG1D4NC-CN structure. The CAp24 capturing capacity was influenced by the distance of the AnkGAG1D4 binding domains to introduce the avidity mode of AnkGAG1D4NC-CN. Consequently, AnkGAG1D4NC-CN showed superior potency in interfering with HIV-1 NL4-3 WT and HIV-1 NL4-3 MIRCAI201V replication than AnkGAG1D4NC-NC and an affinity improved AnkGAG1D4-S45Y.
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Affiliation(s)
- On-anong Juntit
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand; (O.-a.J.); (K.S.); (T.W.); (U.Y.)
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Kanokporn Sornsuwan
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand; (O.-a.J.); (K.S.); (T.W.); (U.Y.)
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Tanchanok Wisitponchai
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand; (O.-a.J.); (K.S.); (T.W.); (U.Y.)
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Vannajan Sanghiran Lee
- Department of Chemistry, Drug Design Development Research Group, Center of Theoretical and Computational Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia;
| | | | - Umpa Yasamut
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand; (O.-a.J.); (K.S.); (T.W.); (U.Y.)
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Chatchai Tayapiwatana
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand; (O.-a.J.); (K.S.); (T.W.); (U.Y.)
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Correspondence: ; Tel.: +66-8-1-8845141; Fax: +66-53-946042
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3
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Sarkar S, Zadrozny KK, Zadorozhnyi R, Russell RW, Quinn CM, Kleinpeter A, Ablan S, Meshkin H, Perilla JR, Freed EO, Ganser-Pornillos BK, Pornillos O, Gronenborn AM, Polenova T. Structural basis of HIV-1 maturation inhibitor binding and activity. Nat Commun 2023; 14:1237. [PMID: 36871077 PMCID: PMC9985623 DOI: 10.1038/s41467-023-36569-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 02/03/2023] [Indexed: 03/06/2023] Open
Abstract
HIV-1 maturation inhibitors (MIs), Bevirimat (BVM) and its analogs interfere with the catalytic cleavage of spacer peptide 1 (SP1) from the capsid protein C-terminal domain (CACTD), by binding to and stabilizing the CACTD-SP1 region. MIs are under development as alternative drugs to augment current antiretroviral therapies. Although promising, their mechanism of action and associated virus resistance pathways remain poorly understood at the molecular, biochemical, and structural levels. We report atomic-resolution magic-angle-spinning NMR structures of microcrystalline assemblies of CACTD-SP1 complexed with BVM and/or the assembly cofactor inositol hexakisphosphate (IP6). Our results reveal a mechanism by which BVM disrupts maturation, tightening the 6-helix bundle pore and quenching the motions of SP1 and the simultaneously bound IP6. In addition, BVM-resistant SP1-A1V and SP1-V7A variants exhibit distinct conformational and binding characteristics. Taken together, our study provides a structural explanation for BVM resistance as well as guidance for the design of new MIs.
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Affiliation(s)
- Sucharita Sarkar
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Kaneil K Zadrozny
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Roman Zadorozhnyi
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Ryan W Russell
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Alex Kleinpeter
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Sherimay Ablan
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Hamed Meshkin
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Eric O Freed
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Barbie K Ganser-Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
| | - Owen Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
| | - Angela M Gronenborn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
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4
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Anti-HIV Potential of Beesioside I Derivatives as Maturation Inhibitors: Synthesis, 3D-QSAR, Molecular Docking and Molecular Dynamics Simulations. Int J Mol Sci 2023; 24:ijms24021430. [PMID: 36674943 PMCID: PMC9867151 DOI: 10.3390/ijms24021430] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/04/2023] [Accepted: 01/09/2023] [Indexed: 01/13/2023] Open
Abstract
HIV-1 maturation is the final step in the retroviral lifecycle that is regulated by the proteolytic cleavage of the Gag precursor protein. As a first-in-class HIV-1 maturation inhibitor (MI), bevirimat blocks virion maturation by disrupting capsid-spacer peptide 1 (CA-SP1) cleavage, which acts as the target of MIs. Previous alterations of beesioside I (1) produced (20S,24S)-15ꞵ,16ꞵ-diacetoxy-18,24; 20,24-diepoxy-9,19-cyclolanostane-3ꞵ,25-diol 3-O-3′,3′-dimethylsuccinate (3, DSC), showing similar anti-HIV potency compared to bevirimat. To ascertain the binding modes of this derivative, further modification of compound 1 was conducted. Three-dimensional quantitative structure−activity relationship (3D-QSAR) analysis combined with docking simulations and molecular dynamics (MD) were conducted. Five new derivatives were synthesized, among which compound 3b showed significant activity against HIV-1NL4-3 with an EC50 value of 0.28 µM. The developed 3D-QSAR model resulted in great predictive ability with training set (r2 = 0.99, q2 = 0.55). Molecular docking studies were complementary to the 3D-QSAR analysis, showing that DSC was differently bound to CA-SP1 with higher affinity than that of bevirimat. MD studies revealed that the complex of the ligand and the protein was stable, with root mean square deviation (RMSD) values <2.5 Å. The above results provided valuable insights into the potential of DSC as a prototype to develop new antiviral agents.
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Johnson MM, Jones CE, Clark DN. The Effect of Treatment-Associated Mutations on HIV Replication and Transmission Cycles. Viruses 2022; 15:107. [PMID: 36680147 PMCID: PMC9861436 DOI: 10.3390/v15010107] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 12/31/2022] Open
Abstract
HIV/AIDS mortality has been decreasing over the last decade. While promising, this decrease correlated directly with increased use of antiretroviral drugs. As a natural consequence of its high mutation rate, treatments provide selection pressure that promotes the natural selection of escape mutants. Individuals may acquire drug-naive strains, or those that have already mutated due to treatment. Even within a host, mutation affects HIV tropism, where initial infection begins with R5-tropic virus, but the clinical transition to AIDS correlates with mutations that lead to an X4-tropic switch. Furthermore, the high mutation rate of HIV has spelled failure for all attempts at an effective vaccine. Pre-exposure drugs are currently the most effective drug-based preventatives, but their effectiveness is also threatened by viral mutation. From attachment and entry to assembly and release, the steps in the replication cycle are also discussed to describe the drug mechanisms and mutations that arise due to those drugs. Revealing the patterns of HIV-1 mutations, their effects, and the coordinated attempt to understand and control them will lead to effective use of current preventative measures and treatment options, as well as the development of new ones.
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Affiliation(s)
- Madison M. Johnson
- Department of Microbiology, Weber State University, Ogden, UT 84408, USA
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6
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The HIV-1 Gag Protein Displays Extensive Functional and Structural Roles in Virus Replication and Infectivity. Int J Mol Sci 2022; 23:ijms23147569. [PMID: 35886917 PMCID: PMC9323242 DOI: 10.3390/ijms23147569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/15/2022] [Accepted: 06/19/2022] [Indexed: 01/10/2023] Open
Abstract
Once merely thought of as the protein responsible for the overall physical nature of the human immunodeficiency virus type 1 (HIV-1), the Gag polyprotein has since been elucidated to have several roles in viral replication and functionality. Over the years, extensive research into the polyproteins’ structure has revealed that Gag can mediate its own trafficking to the plasma membrane, it can interact with several host factors and can even aid in viral genome packaging. Not surprisingly, Gag has also been associated with HIV-1 drug resistance and even treatment failure. Therefore, this review provides an extensive overview of the structural and functional roles of the HIV-1 Gag domains in virion integrity, functionality and infectivity.
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7
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Saito A, Yamashita M. HIV-1 capsid variability: viral exploitation and evasion of capsid-binding molecules. Retrovirology 2021; 18:32. [PMID: 34702294 PMCID: PMC8549334 DOI: 10.1186/s12977-021-00577-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 10/13/2021] [Indexed: 11/17/2022] Open
Abstract
The HIV-1 capsid, a conical shell encasing viral nucleoprotein complexes, is involved in multiple post-entry processes during viral replication. Many host factors can directly bind to the HIV-1 capsid protein (CA) and either promote or prevent HIV-1 infection. The viral capsid is currently being explored as a novel target for therapeutic interventions. In the past few decades, significant progress has been made in our understanding of the capsid–host interactions and mechanisms of action of capsid-targeting antivirals. At the same time, a large number of different viral capsids, which derive from many HIV-1 mutants, naturally occurring variants, or diverse lentiviruses, have been characterized for their interactions with capsid-binding molecules in great detail utilizing various experimental techniques. This review provides an overview of how sequence variation in CA influences phenotypic properties of HIV-1. We will focus on sequence differences that alter capsid–host interactions and give a brief account of drug resistant mutations in CA and their mutational effects on viral phenotypes. Increased knowledge of the sequence-function relationship of CA helps us deepen our understanding of the adaptive potential of the viral capsid.
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Affiliation(s)
- Akatsuki Saito
- Department of Veterinary Medicine, Faculty of Agriculture, University of Miyazaki, Miyazaki, Miyazaki, Japan.,Center for Animal Disease Control, University of Miyazaki, Miyazaki, Miyazaki, Japan
| | - Masahiro Yamashita
- Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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Sornsuwan K, Thongkhum W, Pamonsupornwichit T, Carraway TS, Soponpong S, Sakkhachornphop S, Tayapiwatana C, Yasamut U. Performance of Affinity-Improved DARPin Targeting HIV Capsid Domain in Interference of Viral Progeny Production. Biomolecules 2021; 11:biom11101437. [PMID: 34680070 PMCID: PMC8533564 DOI: 10.3390/biom11101437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/17/2021] [Accepted: 09/28/2021] [Indexed: 01/22/2023] Open
Abstract
Previously, a designed ankyrin repeat protein, AnkGAG1D4, was generated for intracellular targeting of the HIV-1 capsid domain. The efficiency was satisfactory in interfering with the HIV assembly process. Consequently, improved AnkGAG1D4 binding affinity was introduced by substituting tyrosine (Y) for serine (S) at position 45. However, the intracellular anti-HIV-1 activity of AnkGAG1D4-S45Y has not yet been validated. In this study, the performance of AnkGAG1D4 and AnkGAG1D4-S45Y in inhibiting wild-type HIV-1 and HIV-1 maturation inhibitor-resistant replication in SupT1 cells was evaluated. HIV-1 p24 and viral load assays were used to verify the biological activity of AnkGAG1D4 and AnkGAG1D4-S45Y as assembly inhibitors. In addition, retardation of syncytium formation in infected SupT1 cells was observed. Of note, the defense mechanism of both ankyrins did not induce the mutation of target amino acids in the capsid domain. The present data show that the potency of AnkGAG1D4-S45Y was superior to AnkGAG1D4 in interrupting either HIV-1 wild-type or the HIV maturation inhibitor-resistant strain.
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Affiliation(s)
- Kanokporn Sornsuwan
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Weeraya Thongkhum
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Thanathat Pamonsupornwichit
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Tanawan Samleerat Carraway
- Division of Clinical Microbiology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Suthinee Soponpong
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | | | - Chatchai Tayapiwatana
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Umpa Yasamut
- Division of Clinical Immunology, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Biomolecular Therapy and Diagnostic, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
- Center of Innovative Immunodiagnostic Development, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
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Poston D, Zang T, Bieniasz P. Derivation and characterization of an HIV-1 mutant that rescues IP 6 binding deficiency. Retrovirology 2021; 18:25. [PMID: 34454514 PMCID: PMC8403458 DOI: 10.1186/s12977-021-00571-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/19/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND A critical step in the HIV-1 replication cycle is the assembly of Gag proteins to form virions at the plasma membrane. Virion assembly and maturation are facilitated by the cellular polyanion inositol hexaphosphate (IP6), which is proposed to stabilize both the immature Gag lattice and the mature capsid lattice by binding to rings of primary amines at the center of Gag or capsid protein (CA) hexamers. The amino acids comprising these rings are critical for proper virion formation and their substitution results in assembly deficits or impaired infectiousness. To better understand the nature of the deficits that accompany IP6 binding deficiency, we passaged HIV-1 mutants that had substitutions in IP6 coordinating residues to select for compensatory mutations. RESULTS We found a mutation, a threonine to isoleucine substitution at position 371 (T371I) in Gag, that restored replication competence to an IP6-binding-deficient HIV-1 mutant. Notably, unlike wild-type HIV-1, the assembly and infectiousness of resulting virus was not impaired when IP6 biosynthetic enzymes were genetically ablated. Surprisingly, we also found that the maturation inhibitor Bevirimat (BVM) could restore the assembly and replication of an IP6-binding deficient mutant. Moreover, using BVM-dependent mutants we were able to image BVM-induced assembly of individual HIV-1 particles assembly in living cells. CONCLUSIONS Overall these results suggest that IP6-Gag and Gag-Gag contacts are finely tuned to generate a Gag lattice of optimal stability, and that under certain conditions BVM can rescue IP6 deficiency. Additionally, our work identifies an inducible virion assembly system that can be utilized to visualize HIV-1 assembly events using live cell microscopy.
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Affiliation(s)
- Daniel Poston
- Laboratory of Retrovirology, The Rockefeller University, New York, NY, USA
- Weill Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Trinity Zang
- Laboratory of Retrovirology, The Rockefeller University, New York, NY, USA
- Howard Hughes Medical Institute, New York, NY, USA
| | - Paul Bieniasz
- Laboratory of Retrovirology, The Rockefeller University, New York, NY, USA.
- Howard Hughes Medical Institute, New York, NY, USA.
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10
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Mendonça L, Sun D, Ning J, Liu J, Kotecha A, Olek M, Frosio T, Fu X, Himes BA, Kleinpeter AB, Freed EO, Zhou J, Aiken C, Zhang P. CryoET structures of immature HIV Gag reveal six-helix bundle. Commun Biol 2021; 4:481. [PMID: 33863979 PMCID: PMC8052356 DOI: 10.1038/s42003-021-01999-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/18/2021] [Indexed: 11/09/2022] Open
Abstract
Gag is the HIV structural precursor protein which is cleaved by viral protease to produce mature infectious viruses. Gag is a polyprotein composed of MA (matrix), CA (capsid), SP1, NC (nucleocapsid), SP2 and p6 domains. SP1, together with the last eight residues of CA, have been hypothesized to form a six-helix bundle responsible for the higher-order multimerization of Gag necessary for HIV particle assembly. However, the structure of the complete six-helix bundle has been elusive. Here, we determined the structures of both Gag in vitro assemblies and Gag viral-like particles (VLPs) to 4.2 Å and 4.5 Å resolutions using cryo-electron tomography and subtomogram averaging by emClarity. A single amino acid mutation (T8I) in SP1 stabilizes the six-helix bundle, allowing to discern the entire CA-SP1 helix connecting to the NC domain. These structures provide a blueprint for future development of small molecule inhibitors that can lock SP1 in a stable helical conformation, interfere with virus maturation, and thus block HIV-1 infection.
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Affiliation(s)
- Luiza Mendonça
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Dapeng Sun
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Jiying Ning
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Jiwei Liu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Abhay Kotecha
- Thermo Fisher Scientific, Eindhoven, The Netherlands
| | - Mateusz Olek
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
- Department of Chemistry, University of York, York, UK
| | - Thomas Frosio
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Xiaofeng Fu
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Benjamin A Himes
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Alex B Kleinpeter
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Jing Zhou
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Christopher Aiken
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Peijun Zhang
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK.
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11
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Ghimire D, Kc Y, Timilsina U, Goel K, Nitz TJ, Wild CT, Gaur R. A single G10T polymorphism in HIV-1 subtype C Gag-SP1 regulates sensitivity to maturation inhibitors. Retrovirology 2021; 18:9. [PMID: 33836787 PMCID: PMC8033686 DOI: 10.1186/s12977-021-00553-5] [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] [Received: 12/18/2020] [Accepted: 03/23/2021] [Indexed: 08/30/2023] Open
Abstract
BACKGROUND Maturation inhibitors (MIs) potently block HIV-1 maturation by inhibiting the cleavage of the capsid protein and spacer peptide 1 (CA-SP1). Bevirimat (BVM), a highly efficacious first-in-class MI against HIV-1 subtype B isolates, elicited sub-optimal efficacy in clinical trials due to polymorphisms in the CA-SP1 region of the Gag protein (SP1:V7A). HIV-1 subtype C inherently contains this polymorphism thus conferring BVM resistance, however it displayed sensitivity to second generation BVM analogs. RESULTS In this study, we have assessed the efficacy of three novel second-generation MIs (BVM analogs: CV-8611, CV-8612, CV-8613) against HIV-1 subtype B and C isolates. The BVM analogs were potent inhibitors of both HIV-1 subtype B (NL4-3) and subtype C (K3016) viruses. Serial passaging of the subtype C, K3016 virus strain in the presence of BVM analogs led to identification of two mutant viruses-Gag SP1:A1V and CA:I201V. While the SP1:A1V mutant was resistant to the MIs, the CA:I120V mutant displayed partial resistance and a MI-dependent phenotype. Further analysis of the activity of the BVM analogs against two additional HIV-1 subtype C strains, IndieC1 and ZM247 revealed that they had reduced sensitivity as compared to K3016. Sequence analysis of the three viruses identified two polymorphisms at SP1 residues 9 and 10 (K3016: N9, G10; IndieC1/ZM247: S9, T10). The N9S and S9N mutants had no change in MI-sensitivity. On the other hand, replacing glycine at residue 10 with threonine in K3016 reduced its MI sensitivity whereas introducing glycine at SP1 10 in place of threonine in IndieC1 and ZM247 significantly enhanced their MI sensitivity. Thus, the specific glycine residue 10 of SP1 in the HIV-1 subtype C viruses determined sensitivity towards BVM analogs. CONCLUSIONS We have identified an association of a specific glycine at position 10 of Gag-SP1 with an MI susceptible phenotype of HIV-1 subtype C viruses. Our findings have highlighted that HIV-1 subtype C viruses, which were inherently resistant to BVM, may also be similarly predisposed to exhibit a significant degree of resistance to second-generation BVM analogs. Our work has strongly suggested that genetic differences between HIV-1 subtypes may produce variable MI sensitivity that needs to be considered in the development of novel, potent, broadly-active MIs.
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Affiliation(s)
- Dibya Ghimire
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, 110021, India
| | - Yuvraj Kc
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, 110021, India
| | - Uddhav Timilsina
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, 110021, India.,Department of Microbiology and Immunology, University at Buffalo, Buffalo, NY, 14203, USA
| | - Kriti Goel
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, 110021, India
| | - T J Nitz
- DFH Pharma, Gaithersburg, MD, 20886, USA
| | | | - Ritu Gaur
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, 110021, India.
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12
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Mallery DL, Kleinpeter AB, Renner N, Faysal KMR, Novikova M, Kiss L, Wilson MSC, Ahsan B, Ke Z, Briggs JAG, Saiardi A, Böcking T, Freed EO, James LC. A stable immature lattice packages IP 6 for HIV capsid maturation. SCIENCE ADVANCES 2021; 7:7/11/eabe4716. [PMID: 33692109 PMCID: PMC7946374 DOI: 10.1126/sciadv.abe4716] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 01/21/2021] [Indexed: 05/05/2023]
Abstract
HIV virion assembly begins with the construction of an immature lattice consisting of Gag hexamers. Upon virion release, protease-mediated Gag cleavage leads to a maturation event in which the immature lattice disassembles and the mature capsid assembles. The cellular metabolite inositiol hexakisphosphate (IP6) and maturation inhibitors (MIs) both bind and stabilize immature Gag hexamers, but whereas IP6 promotes virus maturation, MIs inhibit it. Here we show that HIV is evolutionarily constrained to maintain an immature lattice stability that ensures IP6 packaging without preventing maturation. Replication-deficient mutant viruses with reduced IP6 recruitment display increased infectivity upon treatment with the MI PF46396 (PF96) or the acquisition of second-site compensatory mutations. Both PF96 and second-site mutations stabilise the immature lattice and restore IP6 incorporation, suggesting that immature lattice stability and IP6 binding are interdependent. This IP6 dependence suggests that modifying MIs to compete with IP6 for Gag hexamer binding could substantially improve MI antiviral potency.
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Affiliation(s)
- Donna L Mallery
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Alex B Kleinpeter
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Nadine Renner
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - K M Rifat Faysal
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Mariia Novikova
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Leo Kiss
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Miranda S C Wilson
- MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Bilal Ahsan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Zunlong Ke
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - John A G Briggs
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Adolfo Saiardi
- MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
| | - Leo C James
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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13
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Kleinpeter AB, Freed EO. HIV-1 Maturation: Lessons Learned from Inhibitors. Viruses 2020; 12:E940. [PMID: 32858867 PMCID: PMC7552077 DOI: 10.3390/v12090940] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/19/2020] [Accepted: 08/20/2020] [Indexed: 02/06/2023] Open
Abstract
Since the emergence of HIV and AIDS in the early 1980s, the development of safe and effective therapies has accompanied a massive increase in our understanding of the fundamental processes that drive HIV biology. As basic HIV research has informed the development of novel therapies, HIV inhibitors have been used as probes for investigating basic mechanisms of HIV-1 replication, transmission, and pathogenesis. This positive feedback cycle has led to the development of highly effective combination antiretroviral therapy (cART), which has helped stall the progression to AIDS, prolong lives, and reduce transmission of the virus. However, to combat the growing rates of virologic failure and toxicity associated with long-term therapy, it is important to diversify our repertoire of HIV-1 treatments by identifying compounds that block additional steps not targeted by current drugs. Most of the available therapeutics disrupt early events in the replication cycle, with the exception of the protease (PR) inhibitors, which act at the virus maturation step. HIV-1 maturation consists of a series of biochemical changes that facilitate the conversion of an immature, noninfectious particle to a mature infectious virion. These changes include proteolytic processing of the Gag polyprotein by the viral protease (PR), structural rearrangement of the capsid (CA) protein, and assembly of individual CA monomers into hexamers and pentamers that ultimately form the capsid. Here, we review the development and therapeutic potential of maturation inhibitors (MIs), an experimental class of anti-HIV-1 compounds with mechanisms of action distinct from those of the PR inhibitors. We emphasize the key insights into HIV-1 biology and structure that the study of MIs has provided. We will focus on three distinct groups of inhibitors that block HIV-1 maturation: (1) compounds that block the processing of the CA-spacer peptide 1 (SP1) cleavage intermediate, the original class of compounds to which the term MI was applied; (2) CA-binding inhibitors that disrupt capsid condensation; and (3) allosteric integrase inhibitors (ALLINIs) that block the packaging of the viral RNA genome into the condensing capsid during maturation. Although these three classes of compounds have distinct structures and mechanisms of action, they share the ability to block the formation of the condensed conical capsid, thereby blocking particle infectivity.
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Affiliation(s)
| | - Eric O. Freed
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA;
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14
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Dick A, Cocklin S. Recent Advances in HIV-1 Gag Inhibitor Design and Development. Molecules 2020; 25:molecules25071687. [PMID: 32272714 PMCID: PMC7181048 DOI: 10.3390/molecules25071687] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/31/2020] [Accepted: 04/05/2020] [Indexed: 02/06/2023] Open
Abstract
Acquired Immune Deficiency Syndrome (AIDS) treatment with combination antiretroviral therapy (cART) has improved the life quality of many patients since its implementation. However, resistance mutations and the accumulation of severe side effects associated with cART remain enormous challenges that need to be addressed with the continual design and redesign of anti-HIV drugs. In this review, we focus on the importance of the HIV-1 Gag polyprotein as the master coordinator of HIV-1 assembly and maturation and as an emerging drug target. Due to its multiple roles in the HIV-1 life cycle, the individual Gag domains are attractive but also challenging targets for inhibitor design. However, recent encouraging developments in targeting the Gag domains such as the capsid protein with highly potent and potentially long-acting inhibitors, as well as the exploration and successful targeting of challenging HIV-1 proteins such as the matrix protein, have demonstrated the therapeutic viability of this important protein. Such Gag-directed inhibitors have great potential for combating the AIDS pandemic and to be useful tools to dissect HIV-1 biology.
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15
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Dicker I, Zhang S, Ray N, Beno BR, Regueiro-Ren A, Joshi S, Cockett M, Krystal M, Lataillade M. Resistance profile of the HIV-1 maturation inhibitor GSK3532795 in vitro and in a clinical study. PLoS One 2019; 14:e0224076. [PMID: 31622432 PMCID: PMC6797179 DOI: 10.1371/journal.pone.0224076] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 10/05/2019] [Indexed: 12/11/2022] Open
Abstract
GSK3532795 (formerly BMS955176) is a second-generation maturation inhibitor (MI) that progressed through a Phase 2b study for treatment of HIV-1 infection. Resistance development to GSK3532795 was evaluated through in vitro methods and was correlated with information obtained in a Phase 2a proof-of-concept study in HIV-1 infected participants. Both low and high concentrations of GSK3532795 were used for selections in vitro, and reduced susceptibility to GSK3532795 mapped specifically to amino acids near the capsid/ spacer peptide 1 (SP1) junction, the cleavage of which is blocked by MIs. Two key substitutions, A364V or V362I, were selected, the latter requiring secondary substitutions to reduce susceptibility to GSK3532795. Three main types of secondary substitutions were observed, none of which reduced GSK3532795 susceptibility in isolation. The first type was in the capsid C-terminal domain and downstream SP1 region (including (Gag numbering) R286K, A326T, T332S/N, I333V and V370A/M). The second, was an R41G substitution in viral protease that occurred with V362I. The third was seen in the capsid N-terminal domain, within the cyclophilin A binding domain (V218A/M, H219Q and G221E). H219Q increased viral replication capacity and reduced susceptibility of poorly growing viruses. In the Phase 2a study, a subset of these substitutions was also observed at baseline and some were selected following GSK35323795 treatment in HIV-1-infected participants.
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Affiliation(s)
- Ira Dicker
- Department of HIV Discovery, ViiV Healthcare, Branford, Connecticut, United States of America
| | - Sharon Zhang
- Department of HIV Discovery, ViiV Healthcare, Branford, Connecticut, United States of America
| | - Neelanjana Ray
- Department of Early Development, Bristol-Myers Squibb Research and Development, Princeton, New Jersey, United States of America
| | - Brett R. Beno
- Department of Molecular Discovery Technologies, Bristol-Myers Squibb Research and Development, Wallingford, Connecticut, United States of America
| | - Alicia Regueiro-Ren
- Department of Chemistry Bristol-Myers Squibb Research and Development, Wallingford Connecticut, United States of America
| | - Samit Joshi
- Department of Early Development, ViiV Healthcare, Branford, Connecticut, United States of America
| | - Mark Cockett
- Department of HIV Discovery, ViiV Healthcare, Branford, Connecticut, United States of America
| | - Mark Krystal
- Department of HIV Discovery, ViiV Healthcare, Branford, Connecticut, United States of America
| | - Max Lataillade
- Department of Early Development, ViiV Healthcare, Branford, Connecticut, United States of America
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16
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Pornillos O, Ganser-Pornillos BK. Maturation of retroviruses. Curr Opin Virol 2019; 36:47-55. [PMID: 31185449 PMCID: PMC6730672 DOI: 10.1016/j.coviro.2019.05.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 04/29/2019] [Accepted: 05/03/2019] [Indexed: 01/10/2023]
Abstract
During retrovirus maturation, cleavage of the precursor structural Gag polyprotein by the viral protease induces architectural rearrangement of the virus particle from an immature into a mature, infectious form. The structural rearrangement encapsidates the viral RNA genome in a fullerene capsid, producing a diffusible viral core that can initiate infection upon entry into the cytoplasm of a host cell. Maturation is an important therapeutic window against HIV-1. In this review, we highlight recent breakthroughs in understanding of the structures of retroviral immature and mature capsid lattices that define the boundary conditions of maturation and provide novel insights on capsid transformation. We also discuss emerging insights on encapsidation of the viral genome in the mature capsid, as well as remaining questions for further study.
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Affiliation(s)
- Owen Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
| | - Barbie K Ganser-Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
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17
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Novikova M, Zhang Y, Freed EO, Peng K. Multiple Roles of HIV-1 Capsid during the Virus Replication Cycle. Virol Sin 2019; 34:119-134. [PMID: 31028522 PMCID: PMC6513821 DOI: 10.1007/s12250-019-00095-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Accepted: 01/16/2019] [Indexed: 11/29/2022] Open
Abstract
Human immunodeficiency virus-1 capsid (HIV-1 CA) is involved in different stages of the viral replication cycle. During virion assembly, CA drives the formation of the hexameric lattice in immature viral particles, while in mature virions CA monomers assemble in cone-shaped cores surrounding the viral RNA genome and associated proteins. In addition to its functions in late stages of the viral replication cycle, CA plays key roles in a number of processes during early phases of HIV-1 infection including trafficking, uncoating, recognition by host cellular proteins and nuclear import of the viral pre-integration complex. As a result of efficient cooperation of CA with other viral and cellular proteins, integration of the viral genetic material into the host genome, which is an essential step for productive viral infection, successfully occurs. In this review, we will summarize available data on CA functions in HIV-1 replication, describing in detail its roles in late and early phases of the viral replication cycle.
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Affiliation(s)
- Mariia Novikova
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Yulan Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
| | - Ke Peng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
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18
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Urano E, Timilsina U, Kaplan JA, Ablan S, Ghimire D, Pham P, Kuruppu N, Mandt R, Durell SR, Nitz TJ, Martin DE, Wild CT, Gaur R, Freed EO. Resistance to Second-Generation HIV-1 Maturation Inhibitors. J Virol 2019; 93:e02017-18. [PMID: 30567982 PMCID: PMC6401422 DOI: 10.1128/jvi.02017-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 12/10/2018] [Indexed: 12/26/2022] Open
Abstract
A betulinic acid-based compound, bevirimat (BVM), inhibits HIV-1 maturation by blocking a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA. Previous studies showed that mutations conferring resistance to BVM cluster around the CA-SP1 cleavage site. Single amino acid polymorphisms in the SP1 region of Gag and the C terminus of CA reduced HIV-1 susceptibility to BVM, leading to the discontinuation of BVM's clinical development. We recently reported a series of "second-generation" BVM analogs that display markedly improved potency and breadth of activity relative to the parent molecule. Here, we demonstrate that viral clones bearing BVM resistance mutations near the C terminus of CA are potently inhibited by second-generation BVM analogs. We performed de novo selection experiments to identify mutations that confer resistance to these novel compounds. Selection experiments with subtype B HIV-1 identified an Ala-to-Val mutation at SP1 residue 1 and a Pro-to-Ala mutation at CA residue 157 within the major homology region (MHR). In selection experiments with subtype C HIV-1, we identified mutations at CA residue 230 (CA-V230M) and SP1 residue 1 (SP1-A1V), residue 5 (SP1-S5N), and residue 10 (SP1-G10R). The positions at which resistance mutations arose are highly conserved across multiple subtypes of HIV-1. We demonstrate that the mutations confer modest to high-level maturation inhibitor resistance. In most cases, resistance was not associated with a detectable increase in the kinetics of CA-SP1 processing. These results identify mutations that confer resistance to second-generation maturation inhibitors and provide novel insights into the mechanism of resistance.IMPORTANCE HIV-1 maturation inhibitors are a class of small-molecule compounds that block a late step in the viral protease-mediated processing of the Gag polyprotein precursor, the viral protein responsible for the formation of virus particles. The first-in-class HIV-1 maturation inhibitor bevirimat was highly effective in blocking HIV-1 replication, but its activity was compromised by naturally occurring sequence polymorphisms within Gag. Recently developed bevirimat analogs, referred to as "second-generation" maturation inhibitors, overcome this issue. To understand more about how these second-generation compounds block HIV-1 maturation, here we selected for HIV-1 mutants that are resistant to these compounds. Selections were performed in the context of two different subtypes of HIV-1. We identified a small set of mutations at highly conserved positions within the capsid and spacer peptide 1 domains of Gag that confer resistance. Identification and analysis of these maturation inhibitor-resistant mutants provide insights into the mechanisms of resistance to these compounds.
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Affiliation(s)
- Emiko Urano
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Uddhav Timilsina
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India
| | - Justin A Kaplan
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Sherimay Ablan
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Dibya Ghimire
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India
| | - Phuong Pham
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Nishani Kuruppu
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Rebecca Mandt
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Stewart R Durell
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | | | | | | | - Ritu Gaur
- Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
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Insight into the mechanism of action of EP-39, a bevirimat derivative that inhibits HIV-1 maturation. Antiviral Res 2019; 164:162-175. [PMID: 30825471 DOI: 10.1016/j.antiviral.2019.02.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 02/19/2019] [Accepted: 02/22/2019] [Indexed: 12/15/2022]
Abstract
Maturation of human immunodeficiency virus type 1 (HIV-1) particles is a key step for viral infectivity. This process can be blocked using maturation inhibitors (MIs) that affect the cleavage of the capsid-spacer peptide 1 (CA-SP1) junction. Here, we investigated the mechanisms underlying the activity of EP-39, a bevirimat (BVM) derivative with better hydrosolubility. To this aim, we selected in vitro EP-39- and BVM-resistant mutants. We found that EP-39-resistant viruses have four mutations within the CA domain (CA-A194T, CA-T200N, CA-V230I, and CA-V230A) and one in the first residue of SP1 (SP1-A1V). We also identified six mutations that confer BVM resistance (CA-A194T, CA-L231F, CA-L231M, SP1-A1V, SP1-S5N and SP1-V7A). To characterize the EP-39 and BVM-resistant mutants, we studied EP-39 effects on mutant virus replication and performed a biochemical analysis with both MIs. We observed common and distinct characteristics, suggesting that, although EP-39 and BVM share the same chemical skeleton, they could interact in a different way with the Gag polyprotein precursor (Pr55Gag). Using an in silico approach, we observed that EP-39 and BVM present different predicted positions on the hexameric crystal structure of the CACTD-SP1 Gag fragment. To clearly understand the relationship between assembly and maturation, we investigated the impact of all identified mutations on virus assembly by expressing Pr55Gag mutants. Finally, using NMR, we have shown that the interaction of EP-39 with a peptide carrying the SP1-A1V mutation (CA-SP1(A1V)-NC) is almost suppressed in comparison with the wild type peptide. These results suggest that EP-39 and BVM could interact differently with the Pr55Gag lattice and that the mutation of the first SP1 residue induces a loss of interaction between Pr55Gag and EP-39.
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Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation. mBio 2018; 9:mBio.01567-18. [PMID: 30327442 PMCID: PMC6191540 DOI: 10.1128/mbio.01567-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Late in the HIV-1 replication cycle, the viral structural protein Gag is targeted to virus assembly sites at the plasma membrane of infected cells. The capsid (CA) domain of Gag plays a critical role in the formation of the hexameric Gag lattice in the immature virion, and, during particle release, CA is cleaved from the Gag precursor by the viral protease and forms the conical core of the mature virion. A highly conserved Pro-Pro-Ile-Pro (PPIP) motif (CA residues 122 to 125) [PPIP(122-125)] in a loop connecting CA helices 6 and 7 resides at a 3-fold axis formed by neighboring hexamers in the immature Gag lattice. In this study, we characterized the role of this PPIP(122-125) loop in HIV-1 assembly and maturation. While mutations P123A and P125A were relatively well tolerated, mutation of P122 and I124 significantly impaired virus release, caused Gag processing defects, and abolished infectivity. X-ray crystallography indicated that the P122A and I124A mutations induce subtle changes in the structure of the mature CA lattice which were permissive for in vitro assembly of CA tubes. Transmission electron microscopy and cryo-electron tomography demonstrated that the P122A and I124A mutations induce severe structural defects in the immature Gag lattice and abrogate conical core formation. Propagation of the P122A and I124A mutants in T-cell lines led to the selection of compensatory mutations within CA. Our findings demonstrate that the CA PPIP(122-125) loop comprises a structural element critical for the formation of the immature Gag lattice.IMPORTANCE Capsid (CA) plays multiple roles in the HIV-1 replication cycle. CA-CA domain interactions are responsible for multimerization of the Gag polyprotein at virus assembly sites, and in the mature virion, CA monomers assemble into a conical core that encapsidates the viral RNA genome. Multiple CA regions that contribute to the assembly and release of HIV-1 particles have been mapped and investigated. Here, we identified and characterized a Pro-rich loop in CA that is important for the formation of the immature Gag lattice. Changes in this region disrupt viral production and abrogate the formation of infectious, mature virions. Propagation of the mutants in culture led to the selection of second-site compensatory mutations within CA. These results expand our knowledge of the assembly and maturation steps in the viral replication cycle and may be relevant for development of antiviral drugs targeting CA.
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21
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High-resolution structures of HIV-1 Gag cleavage mutants determine structural switch for virus maturation. Proc Natl Acad Sci U S A 2018; 115:E9401-E9410. [PMID: 30217893 PMCID: PMC6176557 DOI: 10.1073/pnas.1811237115] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The main structural component of HIV-1 is the Gag polyprotein. During virus release, Gag is cleaved by the viral protease at five sites, triggering a major change in the structure and morphology of the virus. This transition, called maturation, is required to make an infectious virion. We used cryoelectron tomography to obtain high-resolution structures of Gag inside virus particles carrying mutations that block specific combinations of cleavage sites. Analysis of these structures suggests that different combinations of cleavages can destabilize a bundle of alpha-helices at the C terminus of CA. This destabilization, rather than formation of a beta-hairpin at the N terminus of CA as previously suggested, acts as the structural switch for maturation of the virus into its infectious form. HIV-1 maturation occurs via multiple proteolytic cleavages of the Gag polyprotein, causing rearrangement of the virus particle required for infectivity. Cleavage results in beta-hairpin formation at the N terminus of the CA (capsid) protein and loss of a six-helix bundle formed by the C terminus of CA and the neighboring SP1 peptide. How individual cleavages contribute to changes in protein structure and interactions, and how the mature, conical capsid forms, are poorly understood. Here, we employed cryoelectron tomography to determine morphology and high-resolution CA lattice structures for HIV-1 derivatives in which Gag cleavage sites are mutated. These analyses prompt us to revise current models for the crucial maturation switch. Unlike previously proposed, cleavage on either terminus of CA was sufficient, in principle, for lattice maturation, while complete processing was needed for conical capsid formation. We conclude that destabilization of the six-helix bundle, rather than beta-hairpin formation, represents the main determinant of structural maturation.
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Maturation inhibitors facilitate virus assembly and release of HIV-1 capsid P224 mutant. Virology 2018; 521:44-50. [DOI: 10.1016/j.virol.2018.05.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/28/2018] [Accepted: 05/29/2018] [Indexed: 01/25/2023]
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23
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The KT Jeang Retrovirology prize 2018: Eric Freed. Retrovirology 2018; 15:43. [PMID: 29966522 PMCID: PMC6027741 DOI: 10.1186/s12977-018-0430-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 06/26/2018] [Indexed: 11/10/2022] Open
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24
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Wang M, Quinn CM, Perilla JR, Zhang H, Shirra R, Hou G, Byeon IJ, Suiter CL, Ablan S, Urano E, Nitz TJ, Aiken C, Freed EO, Zhang P, Schulten K, Gronenborn AM, Polenova T. Quenching protein dynamics interferes with HIV capsid maturation. Nat Commun 2017; 8:1779. [PMID: 29176596 PMCID: PMC5701193 DOI: 10.1038/s41467-017-01856-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 10/19/2017] [Indexed: 11/14/2022] Open
Abstract
Maturation of HIV-1 particles encompasses a complex morphological transformation of Gag via an orchestrated series of proteolytic cleavage events. A longstanding question concerns the structure of the C-terminal region of CA and the peptide SP1 (CA–SP1), which represents an intermediate during maturation of the HIV-1 virus. By integrating NMR, cryo-EM, and molecular dynamics simulations, we show that in CA–SP1 tubes assembled in vitro, which represent the features of an intermediate assembly state during maturation, the SP1 peptide exists in a dynamic helix–coil equilibrium, and that the addition of the maturation inhibitors Bevirimat and DFH-055 causes stabilization of a helical form of SP1. Moreover, the maturation-arresting SP1 mutation T8I also induces helical structure in SP1 and further global dynamical and conformational changes in CA. Overall, our results show that dynamics of CA and SP1 are critical for orderly HIV-1 maturation and that small molecules can inhibit maturation by perturbing molecular motions. The process of HIV particle maturation involves complex molecular transitions. Here the authors combine NMR spectroscopy, cryo-EM, and molecular dynamics simulations to provide insight into the conformational equilibria in CA-SP1 assemblies relevant to HIV-1 maturation intermediates formation.
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Affiliation(s)
- Mingzhang Wang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA. .,University of Illinois, Theoretical and Computational Biophysics Group, Urbana, IL, 61801, USA.
| | - Huilan Zhang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Randall Shirra
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.,Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Guangjin Hou
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - In-Ja Byeon
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.,Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Christopher L Suiter
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA
| | - Sherimay Ablan
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Emiko Urano
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | | | - Christopher Aiken
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Eric O Freed
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Peijun Zhang
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.,Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.,Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK
| | - Klaus Schulten
- University of Illinois, Theoretical and Computational Biophysics Group, Urbana, IL, 61801, USA
| | - Angela M Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA. .,Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA. .,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA, 15261, USA.
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25
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Insights into the activity of maturation inhibitor PF-46396 on HIV-1 clade C. Sci Rep 2017; 7:43711. [PMID: 28252110 PMCID: PMC5333120 DOI: 10.1038/srep43711] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 01/26/2017] [Indexed: 12/03/2022] Open
Abstract
HIV maturation inhibitors are an emerging class of anti-retroviral compounds that inhibit the viral protease-mediated cleavage of the Gag, CA-SP1 (capsid-spacer peptide 1) peptide to mature CA. The first-in-class maturation inhibitor bevirimat (BVM) displayed potent activity against HIV-1 clade B but was ineffective against other HIV-1 clades including clade C. Another pyridone-based maturation inhibitor, PF-46396 displayed potent activity against HIV-1 clade B. In this study, we aimed at determining the activity of PF-46396 against HIV-1 clade C. We employed various biochemical and virological assays to demonstrate that PF-46396 is effective against HIV-1 clade C. We observed a dose dependent accumulation of CA-SP1 intermediate in presence of the compound. We carried out mutagenesis in the CA- SP1 region of HIV-1 clade C Gag and observed that the mutations conferred resistance against the compound. Many mutations inhibited Gag processing thereby reducing virus release in the absence of the compound. However, presence of PF-46396 rescued these defects and enhanced virus release, replication capacity and infectivity of HIV-1 clade C. These results put together identify PF-46396 as a broadly active maturation inhibitor against HIV-1 clade B and C and help in rational designing of novel analogs with reduced toxicity and increased efficacy for its potential use in clinics.
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26
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Ning J, Erdemci-Tandogan G, Yufenyuy EL, Wagner J, Himes BA, Zhao G, Aiken C, Zandi R, Zhang P. In vitro protease cleavage and computer simulations reveal the HIV-1 capsid maturation pathway. Nat Commun 2016; 7:13689. [PMID: 27958264 PMCID: PMC5159922 DOI: 10.1038/ncomms13689] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 10/24/2016] [Indexed: 12/23/2022] Open
Abstract
HIV-1 virions assemble as immature particles containing Gag polyproteins that are processed by the viral protease into individual components, resulting in the formation of mature infectious particles. There are two competing models for the process of forming the mature HIV-1 core: the disassembly and de novo reassembly model and the non-diffusional displacive model. To study the maturation pathway, we simulate HIV-1 maturation in vitro by digesting immature particles and assembled virus-like particles with recombinant HIV-1 protease and monitor the process with biochemical assays and cryoEM structural analysis in parallel. Processing of Gag in vitro is accurate and efficient and results in both soluble capsid protein and conical or tubular capsid assemblies, seemingly converted from immature Gag particles. Computer simulations further reveal probable assembly pathways of HIV-1 capsid formation. Combining the experimental data and computer simulations, our results suggest a sequential combination of both displacive and disassembly/reassembly processes for HIV-1 maturation. Two competing models—disassembly/reassembly and displacive—have been proposed for how immature spherical HIV virions transform into mature particles with conical cores. Here the authors provide evidence that both disassembly/reassembly and displacive processes occur sequentially during the maturation process.
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Affiliation(s)
- Jiying Ning
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, USA
| | - Gonca Erdemci-Tandogan
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Ernest L Yufenyuy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Jef Wagner
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Benjamin A Himes
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, Pennsylvania 15260, USA
| | - Gongpu Zhao
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, USA
| | - Christopher Aiken
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, USA.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Roya Zandi
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Peijun Zhang
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, USA.,Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford OX3 7BN, UK.,Electron Bio-Imaging Centre, Diamond Light Sources, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
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27
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Lin Z, Cantone J, Lu H, Nowicka-Sans B, Protack T, Yuan T, Yang H, Liu Z, Drexler D, Regueiro-Ren A, Meanwell NA, Cockett M, Krystal M, Lataillade M, Dicker IB. Mechanistic Studies and Modeling Reveal the Origin of Differential Inhibition of Gag Polymorphic Viruses by HIV-1 Maturation Inhibitors. PLoS Pathog 2016; 12:e1005990. [PMID: 27893830 PMCID: PMC5125710 DOI: 10.1371/journal.ppat.1005990] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 10/11/2016] [Indexed: 12/27/2022] Open
Abstract
HIV-1 maturation inhibitors (MIs) disrupt the final step in the HIV-1 protease-mediated cleavage of the Gag polyprotein between capsid p24 capsid (CA) and spacer peptide 1 (SP1), leading to the production of infectious virus. BMS-955176 is a second generation MI with improved antiviral activity toward polymorphic Gag variants compared to a first generation MI bevirimat (BVM). The underlying mechanistic reasons for the differences in polymorphic coverage were studied using antiviral assays, an LC/MS assay that quantitatively characterizes CA/SP1 cleavage kinetics of virus like particles (VLPs) and a radiolabel binding assay to determine VLP/MI affinities and dissociation kinetics. Antiviral assay data indicates that BVM does not achieve 100% inhibition of certain polymorphs, even at saturating concentrations. This results in the breakthrough of infectious virus (partial antagonism) regardless of BVM concentration. Reduced maximal percent inhibition (MPI) values for BVM correlated with elevated EC50 values, while rates of HIV-1 protease cleavage at CA/SP1 correlated inversely with the ability of BVM to inhibit HIV-1 Gag polymorphic viruses: genotypes with more rapid CA/SP1 cleavage kinetics were less sensitive to BVM. In vitro inhibition of wild type VLP CA/SP1 cleavage by BVM was not maintained at longer cleavage times. BMS-955176 exhibited greatly improved MPI against polymorphic Gag viruses, binds to Gag polymorphs with higher affinity/longer dissociation half-lives and exhibits greater time-independent inhibition of CA/SP1 cleavage compared to BVM. Virological (MPI) and biochemical (CA/SP1 cleavage rates, MI-specific Gag affinities) data were used to create an integrated semi-quantitative model that quantifies CA/SP1 cleavage rates as a function of both MI and Gag polymorph. The model outputs are in accord with in vitro antiviral observations and correlate with observed in vivo MI efficacies. Overall, these findings may be useful to further understand antiviral profiles and clinical responses of MIs at a basic level, potentially facilitating further improvements to MI potency and coverage.
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Affiliation(s)
- Zeyu Lin
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Joseph Cantone
- Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Hao Lu
- Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Beata Nowicka-Sans
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Tricia Protack
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Tian Yuan
- Discovery Chemistry Platforms, Princeton, New Jersey, United States of America
| | - Hong Yang
- Discovery Chemistry Platforms, Princeton, New Jersey, United States of America
| | - Zheng Liu
- Discovery Chemistry, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Dieter Drexler
- Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Alicia Regueiro-Ren
- Discovery Chemistry, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Nicholas A. Meanwell
- Discovery Chemistry, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Mark Cockett
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Mark Krystal
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Max Lataillade
- Global Clinical Development, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
| | - Ira B. Dicker
- Departments of Virology, Bristol-Myers Squibb Research & Development, Wallingford, Connecticut, United States of America
- * E-mail: ,
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28
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Spearman P. HIV-1 Gag as an Antiviral Target: Development of Assembly and Maturation Inhibitors. Curr Top Med Chem 2016; 16:1154-66. [PMID: 26329615 DOI: 10.2174/1568026615666150902102143] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 06/18/2015] [Accepted: 06/21/2015] [Indexed: 01/10/2023]
Abstract
HIV-1 Gag is the master orchestrator of particle assembly. The central role of Gag at multiple stages of the HIV lifecycle has led to efforts to develop drugs that directly target Gag and prevent the formation and release of infectious particles. Until recently, however, only the catalytic site protease inhibitors have been available to inhibit late stages of HIV replication. This review summarizes the current state of development of antivirals that target Gag or disrupt late events in the retrovirus lifecycle such as maturation of the viral capsid. Maturation inhibitors represent an exciting new series of antiviral compounds, including those that specifically target CA-SP1 cleavage and the allosteric integrase inhibitors that inhibit maturation by a completely different mechanism. Numerous small molecules and peptides targeting CA have been studied in attempts to disrupt steps in assembly. Efforts to target CA have recently gained considerable momentum from the development of small molecules that bind CA and alter capsid stability at the post-entry stage of the lifecycle. Efforts to develop antivirals that inhibit incorporation of genomic RNA or to inhibit late budding events remain in preliminary stages of development. Overall, the development of novel antivirals targeting Gag and the late stages in HIV replication appears much closer to success than ever, with the new maturation inhibitors leading the way.
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Affiliation(s)
- Paul Spearman
- Department of Pediatrics; Pediatric Infectious Diseases, Emory University, 2015 Uppergate Drive, Atlanta, GA 30322.
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29
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Structure-Activity Relationships of the Human Immunodeficiency Virus Type 1 Maturation Inhibitor PF-46396. J Virol 2016; 90:8181-97. [PMID: 27384665 PMCID: PMC5008107 DOI: 10.1128/jvi.01075-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 06/27/2016] [Indexed: 11/20/2022] Open
Abstract
HIV-1 maturation inhibitors are a novel class of antiretroviral compounds that consist of two structurally distinct chemical classes: betulinic acid derivatives and the pyridone-based compound PF-46396. It is currently believed that both classes act by similar modes of action to generate aberrant noninfectious particles via inhibition of CA-SP1 cleavage during Gag proteolytic processing. In this study, we utilized a series of novel analogues with decreasing similarity to PF-46396 to determine the chemical groups within PF-46396 that contribute to antiviral activity, Gag binding, and the relationship between these essential properties. A spectrum of antiviral activity (active, intermediate, and inactive) was observed across the analogue series with respect to CA-SP1 cleavage and HIV-1 (NL4-3) replication kinetics in Jurkat T cells. We demonstrate that selected inactive analogues are incorporated into wild-type (WT) immature particles and that one inactive analogue is capable of interfering with PF-46396 inhibition of CA-SP1 cleavage. Mutations that confer PF-46396 resistance can impose a defective phenotype on HIV-1 that can be rescued in a compound-dependent manner. Some inactive analogues retained the capacity to rescue PF-46396-dependent mutants (SP1-A3V, SP1-A3T, and CA-P157S), implying that they can also interact with mutant Gag. The structure-activity relationships observed in this study demonstrate that (i) the tert-butyl group is essential for antiviral activity but is not an absolute requirement for Gag binding, (ii) the trifluoromethyl group is optimal but not essential for antiviral activity, and (iii) the 2-aminoindan group is important for antiviral activity and Gag binding but is not essential, as its replacement is tolerated. IMPORTANCE Combinations of antiretroviral drugs successfully treat HIV/AIDS patients; however, drug resistance problems make the development of new mechanistic drug classes an ongoing priority. HIV-1 maturation inhibitors are novel as they target the Gag protein, specifically by inhibiting CA-SP1 proteolytic cleavage. The lack of high-resolution structural information of the CA-SP1 target in Gag has hindered our understanding of the inhibitor-binding pocket and maturation inhibitor mode of action. Therefore, we utilized analogues of the maturation inhibitor PF-46396 as chemical tools to determine the chemical components of PF-46396 that contribute to antiviral activity and Gag binding and the relationship between these essential properties. This is the first study to report structure-activity relationships of the maturation inhibitor PF-46396. PF-46396 is chemically distinct from betulinic acid-derived maturation inhibitors; therefore, our data provide a foundation of knowledge that will aid our understanding of how structurally distinct maturation inhibitors act by similar modes of action.
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30
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Wagner JM, Zadrozny KK, Chrustowicz J, Purdy MD, Yeager M, Ganser-Pornillos BK, Pornillos O. Crystal structure of an HIV assembly and maturation switch. eLife 2016; 5. [PMID: 27416583 PMCID: PMC4946879 DOI: 10.7554/elife.17063] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/13/2016] [Indexed: 12/25/2022] Open
Abstract
Virus assembly and maturation proceed through the programmed operation of molecular switches, which trigger both local and global structural rearrangements to produce infectious particles. HIV-1 contains an assembly and maturation switch that spans the C-terminal domain (CTD) of the capsid (CA) region and the first spacer peptide (SP1) of the precursor structural protein, Gag. The crystal structure of the CTD-SP1 Gag fragment is a goblet-shaped hexamer in which the cup comprises the CTD and an ensuing type II β-turn, and the stem comprises a 6-helix bundle. The β-turn is critical for immature virus assembly and the 6-helix bundle regulates proteolysis during maturation. This bipartite character explains why the SP1 spacer is a critical element of HIV-1 Gag but is not a universal property of retroviruses. Our results also indicate that HIV-1 maturation inhibitors suppress unfolding of the CA-SP1 junction and thereby delay access of the viral protease to its substrate. DOI:http://dx.doi.org/10.7554/eLife.17063.001 Viruses like HIV must undergo a process called maturation in order to successfully infect cells. Maturation involves a dramatic rearrangement in the architecture of the virus. That is to say, the virus’s internal protein coat – called the capsid – must change from an immature sphere into a mature cone-shaped coat. Notably, this maturation process is what is disrupted by the protease inhibitors that are a major component of anti-HIV drug cocktails. Structural changes in small portions of the capsid protein, termed molecular switches, commonly trigger the viral capsids to reorganize. The HIV capsid has two of these switches, and Wagner, Zadrozny et al. set out to understand how one of them – called the CA-SP1 switch – works. Solving the three-dimensional structure of the immature form of the CA-SP1 switch revealed that it forms a well-structured bundle of six helices. This helical bundle captures another section of the capsid protein that would otherwise be cut by a viral protease. The CA-SP1 switch therefore controls how quickly the protein is cut and the start of the maturation process. Wagner, Zadrozny et al. then discovered that other small molecule inhibitors of HIV, called maturation inhibitors, work by binding to and disrupting the transformation of the CA-SP1 switch. Finally, further experiments showed that the formation of the CA-SP1 helical bundle controls when the immature capsid shell forms and coordinates the process with the capsid gaining the genetic material of the virus. The new structure means that researchers now know what the HIV capsid looks like at the start and end of maturation. The next challenge will be to figure out exactly how the capsid changes from one form to the next as HIV matures. DOI:http://dx.doi.org/10.7554/eLife.17063.002
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Affiliation(s)
- Jonathan M Wagner
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Kaneil K Zadrozny
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Jakub Chrustowicz
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States.,Department of Medicine, Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, United States
| | - Barbie K Ganser-Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Owen Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
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31
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Schur FKM, Obr M, Hagen WJH, Wan W, Jakobi AJ, Kirkpatrick JM, Sachse C, Kräusslich HG, Briggs JAG. An atomic model of HIV-1 capsid-SP1 reveals structures regulating assembly and maturation. Science 2016; 353:506-8. [PMID: 27417497 DOI: 10.1126/science.aaf9620] [Citation(s) in RCA: 291] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 06/29/2016] [Indexed: 12/28/2022]
Abstract
Immature HIV-1 assembles at and buds from the plasma membrane before proteolytic cleavage of the viral Gag polyprotein induces structural maturation. Maturation can be blocked by maturation inhibitors (MIs), thereby abolishing infectivity. The CA (capsid) and SP1 (spacer peptide 1) region of Gag is the key regulator of assembly and maturation and is the target of MIs. We applied optimized cryo-electron tomography and subtomogram averaging to resolve this region within assembled immature HIV-1 particles at 3.9 angstrom resolution and built an atomic model. The structure reveals a network of intra- and intermolecular interactions mediating immature HIV-1 assembly. The proteolytic cleavage site between CA and SP1 is inaccessible to protease. We suggest that MIs prevent CA-SP1 cleavage by stabilizing the structure, and MI resistance develops by destabilizing CA-SP1.
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Affiliation(s)
- Florian K M Schur
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany. Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany
| | - Martin Obr
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany. Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Wim J H Hagen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - William Wan
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Arjen J Jakobi
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany. Hamburg Unit c/o DESY (Deutsches Elektronen-Synchrotron), European Molecular Biology Laboratory, Notkestraße 85, 22607 Hamburg, Germany
| | - Joanna M Kirkpatrick
- Proteomics Core Facility, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Carsten Sachse
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Hans-Georg Kräusslich
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany. Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - John A G Briggs
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany. Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany.
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32
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Stability of HIV Frameshift Site RNA Correlates with Frameshift Efficiency and Decreased Virus Infectivity. J Virol 2016; 90:6906-6917. [PMID: 27194769 DOI: 10.1128/jvi.00149-16] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/13/2016] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED Human immunodeficiency virus (HIV) replication is strongly dependent upon a programmed ribosomal frameshift. Here we investigate the relationships between the thermodynamic stability of the HIV type 1 (HIV-1) RNA frameshift site stem-loop, frameshift efficiency, and infectivity, using pseudotyped HIV-1 and HEK293T cells. The data reveal a strong correlation between frameshift efficiency and local, but not overall, RNA thermodynamic stability. Mutations that modestly increase the local stability of the frameshift site RNA stem-loop structure increase frameshift efficiency 2-fold to 3-fold in cells. Thus, frameshift efficiency is determined by the strength of the thermodynamic barrier encountered by the ribosome. These data agree with previous in vitro measurements, suggesting that there are no virus- or host-specific factors that modulate frameshifting. The data also indicate that there are no sequence-specific requirements for the frameshift site stem-loop. A linear correlation between Gag-polymerase (Gag-Pol) levels in cells and levels in virions supports the idea of a stochastic virion assembly mechanism. We further demonstrate that the surrounding genomic RNA secondary structure influences frameshift efficiency and that a mutation that commonly arises in response to protease inhibitor therapy creates a functional but inefficient secondary slippery site. Finally, HIV-1 mutants with enhanced frameshift efficiencies are significantly less infectious, suggesting that compounds that increase frameshift efficiency by as little as 2-fold may be effective at suppressing HIV-1 replication. IMPORTANCE HIV, like many retroviruses, utilizes a -1 programmed ribosomal frameshift to generate viral enzymes in the form of a Gag-Pol polyprotein precursor. Thus, frameshifting is essential for viral replication. Here, we utilized a panel of mutant HIV strains to demonstrate that in cells, frameshifting efficiency is correlated with the stability of the local thermodynamic barrier to ribosomal translocation. Increasing the stability of the frameshift site RNA increases the frameshift efficiency 2-fold to 3-fold. Mutant viruses with increased frameshift efficiencies have significantly reduced infectivity. These data suggest that this effect might be exploited in the development of novel antiviral strategies.
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Nowicka-Sans B, Protack T, Lin Z, Li Z, Zhang S, Sun Y, Samanta H, Terry B, Liu Z, Chen Y, Sin N, Sit SY, Swidorski JJ, Chen J, Venables BL, Healy M, Meanwell NA, Cockett M, Hanumegowda U, Regueiro-Ren A, Krystal M, Dicker IB. Identification and Characterization of BMS-955176, a Second-Generation HIV-1 Maturation Inhibitor with Improved Potency, Antiviral Spectrum, and Gag Polymorphic Coverage. Antimicrob Agents Chemother 2016; 60:3956-69. [PMID: 27090171 PMCID: PMC4914680 DOI: 10.1128/aac.02560-15] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 12/03/2015] [Indexed: 12/26/2022] Open
Abstract
BMS-955176 is a second-generation human immunodeficiency virus type 1 (HIV-1) maturation inhibitor (MI). A first-generation MI, bevirimat, showed clinical efficacy in early-phase studies, but ∼50% of subjects had viruses with reduced susceptibility associated with naturally occurring polymorphisms in Gag near the site of MI action. MI potency was optimized using a panel of engineered reporter viruses containing site-directed polymorphic changes in Gag that reduce susceptibility to bevirimat (including V362I, V370A/M/Δ, and T371A/Δ), leading incrementally to the identification of BMS-955176. BMS-955176 exhibits potent activity (50% effective concentration [EC50], 3.9 ± 3.4 nM [mean ± standard deviation]) toward a library (n = 87) of gag/pr recombinant viruses representing 96.5% of subtype B polymorphic Gag diversity near the CA/SP1 cleavage site. BMS-955176 exhibited a median EC50 of 21 nM toward a library of subtype B clinical isolates assayed in peripheral blood mononuclear cells (PBMCs). Potent activity was maintained against a panel of reverse transcriptase, protease, and integrase inhibitor-resistant viruses, with EC50s similar to those for the wild-type virus. A 5.4-fold reduction in EC50 occurred in the presence of 40% human serum plus 27 mg/ml of human serum albumin (HSA), which corresponded well to an in vitro measurement of 86% human serum binding. Time-of-addition and pseudotype reporter virus studies confirm a mechanism of action for the compound that occurs late in the virus replication cycle. BMS-955176 inhibits HIV-1 protease cleavage at the CA/SP1 junction within Gag in virus-like particles (VLPs) and in HIV-1-infected cells, and it binds reversibly and with high affinity to assembled Gag in purified HIV-1 VLPs. Finally, in vitro combination studies showed no antagonistic interactions with representative antiretrovirals (ARVs) of other mechanistic classes. In conclusion, BMS-955176 is a second-generation MI with potent in vitro anti-HIV-1 activity and a greatly improved preclinical profile compared to that of bevirimat.
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Affiliation(s)
- Beata Nowicka-Sans
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Tricia Protack
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Zeyu Lin
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Zhufang Li
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Sharon Zhang
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Yongnian Sun
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Himadri Samanta
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Brian Terry
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Zheng Liu
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Yan Chen
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Ny Sin
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Sing-Yuen Sit
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Jacob J Swidorski
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Jie Chen
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Brian L Venables
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Matthew Healy
- Bristol-Myers Squibb, Research and Development, Department of Genomics, Wallingford, Connecticut, USA
| | - Nicholas A Meanwell
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Mark Cockett
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Umesh Hanumegowda
- Bristol-Myers Squibb, Research and Development, Department of Preclinical Optimization, Wallingford, Connecticut, USA
| | - Alicia Regueiro-Ren
- Bristol-Myers Squibb, Research and Development, Department of Discovery Chemistry, Wallingford, Connecticut, USA
| | - Mark Krystal
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
| | - Ira B Dicker
- Bristol-Myers Squibb, Research and Development, Department of Virology, Wallingford, Connecticut, USA
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Identification of potent maturation inhibitors against HIV-1 clade C. Sci Rep 2016; 6:27403. [PMID: 27264714 PMCID: PMC4893694 DOI: 10.1038/srep27403] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/18/2016] [Indexed: 12/05/2022] Open
Abstract
Antiretroviral therapy has led to a profound improvement in the clinical care of HIV-infected patients. However, drug tolerability and the evolution of drug resistance have limited treatment options for many patients. Maturation inhibitors are a new class of antiretroviral agents for treatment of HIV-1. They act by interfering with the maturation of the virus by blocking the last step in Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA by the viral protease (PR). The first-in-class maturation inhibitor bevirimat (BVM) failed against a subset of HIV-1 isolates in clinical trials due to polymorphisms present in the CA-SP1 region of the Gag protein. Sequence analysis indicated that these polymorphisms are more common in non-clade B strains of HIV-1 such as HIV-1 clade C. Indeed, BVM was found to be ineffective against HIV-1 clade C molecular clones tested in this study. A number of BVM analogs were synthesized by chemical modifications at the C-28 position to improve its activity. The new BVM analogs displayed potent activity against HIV-1 clade B and C and also reduced infectivity of the virus. This study identifies novel and broadly active BVM analogs that may ultimately demonstrate efficacy in the clinic.
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Abstract
The virally encoded protease is an important drug target for AIDS therapy. Despite the potency of the current drugs, infections with resistant viral strains limit the long-term effectiveness of therapy. Highly resistant variants of HIV protease from clinical isolates have different combinations of about 20 mutations and several orders of magnitude worse binding affinity for clinical inhibitors. Strategies are being explored to inhibit these highly resistant mutants. The existing inhibitors can be modified by introducing groups with the potential to form new interactions with conserved protease residues, and the flexible flaps. Alternative strategies are discussed, including designing inhibitors to bind to the open conformation of the protease dimer, and inhibition of the protease-catalyzed processing of the Gag-Pol precursor.
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Mutations of Conserved Residues in the Major Homology Region Arrest Assembling HIV-1 Gag as a Membrane-Targeted Intermediate Containing Genomic RNA and Cellular Proteins. J Virol 2015; 90:1944-63. [PMID: 26656702 PMCID: PMC4734008 DOI: 10.1128/jvi.02698-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 11/25/2015] [Indexed: 12/22/2022] Open
Abstract
The major homology region (MHR) is a highly conserved motif that is found within the Gag protein of all orthoretroviruses and some retrotransposons. While it is widely accepted that the MHR is critical for assembly of HIV-1 and other retroviruses, how the MHR functions and why it is so highly conserved are not understood. Moreover, consensus is lacking on when HIV-1 MHR residues function during assembly. Here, we first addressed previous conflicting reports by confirming that MHR deletion, like conserved MHR residue substitution, leads to a dramatic reduction in particle production in human and nonhuman primate cells expressing HIV-1 proviruses. Next, we used biochemical analyses and immunoelectron microscopy to demonstrate that conserved residues in the MHR are required after assembling Gag has associated with genomic RNA, recruited critical host factors involved in assembly, and targeted to the plasma membrane. The exact point of inhibition at the plasma membrane differed depending on the specific mutation, with one MHR mutant arrested as a membrane-associated intermediate that is stable upon high-salt treatment and other MHR mutants arrested as labile, membrane-associated intermediates. Finally, we observed the same assembly-defective phenotypes when the MHR deletion or conserved MHR residue substitutions were engineered into Gag from a subtype B, lab-adapted provirus or Gag from a subtype C primary isolate that was codon optimized. Together, our data support a model in which MHR residues act just after membrane targeting, with some MHR residues promoting stability and another promoting multimerization of the membrane-targeted assembling Gag oligomer. IMPORTANCE The retroviral Gag protein exhibits extensive amino acid sequence variation overall; however, one region of Gag, termed the major homology region, is conserved among all retroviruses and even some yeast retrotransposons, although the reason for this conservation remains poorly understood. Highly conserved residues in the major homology region are required for assembly of retroviruses; however, when these residues are required during assembly is not clear. Here, we used biochemical and electron microscopic analyses to demonstrate that these conserved residues function after assembling HIV-1 Gag has associated with genomic RNA, recruited critical host factors involved in assembly, and targeted to the plasma membrane but before Gag has completed the assembly process. By revealing precisely when conserved residues in the major homology region are required during assembly, these studies resolve existing controversies and set the stage for future experiments aimed at a more complete understanding of how the major homology region functions.
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Identification of an HIV-1 Mutation in Spacer Peptide 1 That Stabilizes the Immature CA-SP1 Lattice. J Virol 2015; 90:972-8. [PMID: 26537676 DOI: 10.1128/jvi.02204-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 10/27/2015] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Upon release of HIV-1 particles from the infected cell, the viral protease cleaves the Gag polyprotein at specific sites, triggering maturation. During this process, which is essential for infectivity, the capsid protein (CA) reassembles into a conical core. Maturation inhibitors (MIs) block HIV-1 maturation by interfering with protease-mediated CA-spacer peptide 1 (CA-SP1) processing, concomitantly stabilizing the immature CA-SP1 lattice; virions from MI-treated cells retain an immature-like CA-SP1 lattice, whereas mutational abolition of cleavage at the CA-SP1 site results in virions in which the CA-SP1 lattice converts to a mature-like form. We previously reported that propagation of HIV-1 in the presence of MI PF-46396 selected for assembly-defective, compound-dependent mutants with amino acid substitutions in the major homology region (MHR) of CA. Propagation of these mutants in the absence of PF-46396 resulted in the acquisition of second-site compensatory mutations. These included a Thr-to-Ile substitution at SP1 residue 8 (T8I), which results in impaired CA-SP1 processing. Thus, the T8I mutation phenocopies PF-46396 treatment in terms of its ability to rescue the replication defect imposed by the MHR mutations and to impede CA-SP1 processing. Here, we use cryo-electron tomography to show that, like MIs, the T8I mutation stabilizes the immature-like CA-SP1 lattice. These results have important implications for the mechanism of action of HIV-1 MIs; they also suggest that T8I may provide a valuable tool for structural definition of the CA-SP1 boundary region, which has thus far been refractory to high-resolution analysis, apparently because of conformational flexibility in this region of Gag. IMPORTANCE HIV-1 maturation involves dissection of the Gag polyprotein by the viral protease and assembly of a conical capsid enclosing the viral ribonucleoprotein. Maturation inhibitors (MIs) prevent the final cleavage step at the site between the capsid protein (CA) and spacer peptide 1 (SP1), apparently by binding at this site and denying the protease access. Additionally, MIs stabilize the immature-like CA-SP1 lattice, preventing release of CA into the soluble pool. We previously found that T8I, a mutation in SP1, rescues a PF-46396-dependent CA mutant and blocks CA-SP1 cleavage. In this study, we imaged T8I virions by cryo-electron tomography and showed that T8I mutants, like MI-treated virions, contain an immature CA-SP1 lattice. These results lay the groundwork needed to understand the structure of the CA-SP1 interface region and further illuminate the mechanism of action of MIs.
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38
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Wang D, Lu W, Li F. Pharmacological intervention of HIV-1 maturation. Acta Pharm Sin B 2015; 5:493-9. [PMID: 26713265 PMCID: PMC4675807 DOI: 10.1016/j.apsb.2015.05.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 05/25/2015] [Indexed: 11/27/2022] Open
Abstract
Despite significant advances in antiretroviral therapy, increasing drug resistance and toxicities observed among many of the current approved human immunodeficiency virus (HIV) drugs indicate a need for discovery and development of potent and safe antivirals with a novel mechanism of action. Maturation inhibitors (MIs) represent one such new class of HIV therapies. MIs inhibit a late step in the HIV-1 Gag processing cascade, causing defective core condensation and the release of non-infectious virus particles from infected cells, thus blocking the spread of the infection to new cells. Clinical proof-of-concept for the MIs was established with betulinic acid derived bevirimat, the prototype HIV-1 MI. Despite the discontinuation of its further clinical development in 2010 due to a lack of uniform patient response caused by naturally occurring drug resistance Gag polymorphisms, several second-generation MIs with improved activity against viruses exhibiting Gag polymorphism mediated resistance have been recently discovered and are under clinical evaluation in HIV/AID patients. In this review, current understanding of HIV-1 MIs is described and recent progress made toward elucidating the mechanism of action, target identification and development of second-generation MIs is reviewed.
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Key Words
- BMS, Bristol-Myers Squibb
- Bevirimat
- CA, capsid
- GSK, GlaxoSmithKline
- Gag processing
- Gag-drug interaction
- HIV, human immunodeficiency virus
- HIV-1 maturation inhibitors
- MA, matrix
- MI, maturation inhibitor
- PI, protease inhibitor
- PR, protease
- SIV, Simian immunodeficiency virus
- SP1, spacer protein 1
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Alkyl Amine Bevirimat Derivatives Are Potent and Broadly Active HIV-1 Maturation Inhibitors. Antimicrob Agents Chemother 2015; 60:190-7. [PMID: 26482309 DOI: 10.1128/aac.02121-15] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 10/12/2015] [Indexed: 11/20/2022] Open
Abstract
Concomitant with the release of human immunodeficiency virus type 1 (HIV-1) particles from the infected cell, the viral protease cleaves the Gag polyprotein precursor at a number of sites to trigger virus maturation. We previously reported that a betulinic acid-derived compound, bevirimat (BVM), blocks HIV-1 maturation by disrupting a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA. BVM was shown in multiple clinical trials to be safe and effective in reducing viral loads in HIV-1-infected patients. However, naturally occurring polymorphisms in the SP1 region of Gag (e.g., SP1-V7A) led to a variable response in some BVM-treated patients. The reduced susceptibility of SP1-polymorphic HIV-1 to BVM resulted in the discontinuation of its clinical development. To overcome the loss of BVM activity induced by polymorphisms in SP1, we carried out an extensive medicinal chemistry campaign to develop novel maturation inhibitors. In this study, we focused on alkyl amine derivatives modified at the C-28 position of the BVM scaffold. We identified a set of derivatives that are markedly more potent than BVM against an HIV-1 clade B clone (NL4-3) and show robust antiviral activity against a variant of NL4-3 containing the V7A polymorphism in SP1. One of the most potent of these compounds also strongly inhibited a multiclade panel of primary HIV-1 isolates. These data demonstrate that C-28 alkyl amine derivatives of BVM can, to a large extent, overcome the loss of susceptibility imposed by polymorphisms in SP1.
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Hadravová R, Rumlová M, Ruml T. FAITH - Fast Assembly Inhibitor Test for HIV. Virology 2015; 486:78-87. [PMID: 26410239 DOI: 10.1016/j.virol.2015.08.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 08/25/2015] [Accepted: 08/27/2015] [Indexed: 11/17/2022]
Abstract
Due to the high number of drug-resistant HIV-1 mutants generated by highly active antiretroviral therapy (HAART), there is continuing demand for new types of inhibitors. Both the assembly of the Gag polyprotein into immature and mature HIV-1 particles are attractive candidates for the blocking of the retroviral life cycle. Currently, no therapeutically-used assembly inhibitor is available. One possible explanation is the lack of a reliable and simple assembly inhibitor screening method. To identify compounds potentially inhibiting the formation of both types of HIV-1 particles, we developed a new fluorescent high-throughput screening assay. This assay is based on the quantification of the assembly efficiency in vitro in a 96-well plate format. The key components of the assay are HIV-1 Gag-derived proteins and a dual-labelled oligonucleotide, which emits fluorescence only when the assembly of retroviral particles is inhibited. The method was validated using three (CAI, BM2, PF74) reported assembly inhibitors.
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Affiliation(s)
- Romana Hadravová
- Institute of Organic Chemistry and Biochemistry IOCB Research Centre & Gilead Sciences, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague, Czech Republic
| | - Michaela Rumlová
- Institute of Organic Chemistry and Biochemistry IOCB Research Centre & Gilead Sciences, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague, Czech Republic; Department of Biotechnology, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
| | - Tomáš Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Technická 3, 166 28 Prague, Czech Republic.
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Abstract
Major advances have occurred in recent years in our understanding of HIV-1 assembly, release and maturation, as work in this field has been propelled forwards by developments in imaging technology, structural biology, and cell and molecular biology. This increase in basic knowledge is being applied to the development of novel inhibitors designed to target various aspects of virus assembly and maturation. This Review highlights recent progress in elucidating the late stages of the HIV-1 replication cycle and the related interplay between virology, cell and molecular biology, and drug discovery.
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Affiliation(s)
- Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Bg. 535, Room 110, 1050 Boyles St., Frederick, Maryland 21702-1201, USA
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Tedbury PR, Freed EO. HIV-1 gag: an emerging target for antiretroviral therapy. Curr Top Microbiol Immunol 2015; 389:171-201. [PMID: 25731773 DOI: 10.1007/82_2015_436] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
The advances made in the treatment of HIV-1 infection represent a major success of modern biomedical research, prolonging healthy life and reducing virus transmission. There remain, however, many challenges relating primarily to side effects of long-term therapy and the ever-present danger of the emergence of drug-resistant strains. To counter these threats, there is a continuing need for new and better drugs, ideally targeting multiple independent steps in the HIV-1 replication cycle. The most successful current drugs target the viral enzymes: protease (PR), reverse transcriptase (RT), and integrase (IN). In this review, we outline the advances made in targeting the Gag protein and its mature products, particularly capsid and nucleocapsid, and highlight possible targets for future pharmacological intervention.
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Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Center for Cancer Research, Frederick, MD, 21702-1201, USA
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43
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Bird SW, Kirkegaard K, Agbandje-McKenna M, Freed EO. The ins and outs of viral infection: keystone meeting review. Viruses 2014; 6:3652-62. [PMID: 25256395 PMCID: PMC4189043 DOI: 10.3390/v6093652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 09/23/2014] [Accepted: 09/23/2014] [Indexed: 12/14/2022] Open
Abstract
Newly observed mechanisms for viral entry, assembly, and exit are challenging our current understanding of the replication cycle of different viruses. To address and better understand these mechanisms, a Keystone Symposium was organized in the snowy mountains of Colorado (“The Ins and Outs of Viral Infection: Entry, Assembly, Exit, and Spread”; 30 March–4 April 2014, Beaver Run Resort, Breckenridge, Colorado, organized by Karla Kirkegaard, Mavis Agbandje-McKenna, and Eric O. Freed). The meeting served to bring together cell biologists, structural biologists, geneticists, and scientists expert in viral pathogenesis to discuss emerging mechanisms of viral ins and outs. The conference was organized around different phases of the viral replication cycle, including cell entry, viral assembly and post-assembly maturation, virus structure, cell exit, and virus spread. This review aims to highlight important topics and themes that emerged during the conference.
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Affiliation(s)
- Sara W Bird
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Karla Kirkegaard
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
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MicroRNA binding to the HIV-1 Gag protein inhibits Gag assembly and virus production. Proc Natl Acad Sci U S A 2014; 111:E2676-83. [PMID: 24938790 DOI: 10.1073/pnas.1408037111] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
MicroRNAs (miRNAs) are small, 18-22 nt long, noncoding RNAs that act as potent negative gene regulators in a variety of physiological and pathological processes. To repress gene expression, miRNAs are packaged into RNA-induced silencing complexes (RISCs) that target mRNAs for degradation and/or translational repression in a sequence-specific manner. Recently, miRNAs have been shown to also interact with proteins outside RISCs, impacting cellular processes through mechanisms not involving gene silencing. Here, we define a previously unappreciated activity of miRNAs in inhibiting RNA-protein interactions that in the context of HIV-1 biology blocks HIV virus budding and reduces virus infectivity. This occurs by miRNA binding to the nucleocapsid domain of the Gag protein, the main structural component of HIV-1 virions. The resulting miRNA-Gag complexes interfere with viral-RNA-mediated Gag assembly and viral budding at the plasma membrane, with imperfectly assembled Gag complexes endocytosed and delivered to lysosomes. The blockade of virus production by miRNA is reversed by adding the miRNA's target mRNA and stimulated by depleting Argonaute-2, suggesting that when miRNAs are not mediating gene silencing, they can block HIV-1 production through disruption of Gag assembly on membranes. Overall, our findings have significant implications for understanding how cells modulate HIV-1 infection by miRNA expression and raise the possibility that miRNAs can function to disrupt RNA-mediated protein assembly processes in other cellular contexts.
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45
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Abstract
UNLABELLED During virion maturation, the Rous sarcoma virus (RSV) capsid protein is cleaved from the Gag protein as the proteolytic intermediate CA-SP. Further trimming at two C-terminal sites removes the spacer peptide (SP), producing the mature capsid proteins CA and CA-S. Abundant genetic and structural evidence shows that the SP plays a critical role in stabilizing hexameric Gag interactions that form immature particles. Freeing of CA-SP from Gag breaks immature interfaces and initiates the formation of mature capsids. The transient persistence of CA-SP in maturing virions and the identification of second-site mutations in SP that restore infectivity to maturation-defective mutant viruses led us to hypothesize that SP may play an important role in promoting the assembly of mature capsids. This study presents a biophysical and biochemical characterization of CA-SP and its assembly behavior. Our results confirm cryo-electron microscopy (cryo-EM) structures reported previously by Keller et al. (J. Virol. 87:13655-13664, 2013, doi:10.1128/JVI.01408-13) showing that monomeric CA-SP is fully capable of assembling into capsid-like structures identical to those formed by CA. Furthermore, SP confers aggressive assembly kinetics, which is suggestive of higher-affinity CA-SP interactions than observed with either of the mature capsid proteins. This aggressive assembly is largely independent of the SP amino acid sequence, but the formation of well-ordered particles is sensitive to the presence of the N-terminal β-hairpin. Additionally, CA-SP can nucleate the assembly of CA and CA-S. These results suggest a model in which CA-SP, once separated from the Gag lattice, can actively promote the interactions that form mature capsids and provide a nucleation point for mature capsid assembly. IMPORTANCE The spacer peptide is a documented target for antiretroviral therapy. This study examines the biochemical and biophysical properties of CA-SP, an intermediate form of the retrovirus capsid protein. The results demonstrate a previously unrecognized activity of SP in promoting capsid assembly during maturation.
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46
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A temporospatial map that defines specific steps at which critical surfaces in the Gag MA and CA domains act during immature HIV-1 capsid assembly in cells. J Virol 2014; 88:5718-41. [PMID: 24623418 DOI: 10.1128/jvi.03609-13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED During HIV-1 assembly, Gag polypeptides target to the plasma membrane, where they multimerize to form immature capsids that undergo budding and maturation. Previous mutational analyses identified residues within the Gag matrix (MA) and capsid (CA) domains that are required for immature capsid assembly, and structural studies showed that these residues are clustered on four exposed surfaces in Gag. Exactly when and where the three critical surfaces in CA function during assembly are not known. Here, we analyzed how mutations in these four critical surfaces affect the formation and stability of assembly intermediates in cells expressing the HIV-1 provirus. The resulting temporospatial map reveals that critical MA residues act during membrane targeting, residues in the C-terminal CA subdomain (CA-CTD) dimer interface are needed for the stability of the first membrane-bound assembly intermediate, CA-CTD base residues are necessary for progression past the first membrane-bound intermediate, and residues in the N-terminal CA subdomain (CA-NTD) stabilize the last membrane-bound intermediate. Importantly, we found that all four critical surfaces act while Gag is associated with the cellular facilitators of assembly ABCE1 and DDX6. When correlated with existing structural data, our findings suggest the following model: Gag dimerizes via the CA-CTD dimer interface just before or during membrane targeting, individual CA-CTD hexamers form soon after membrane targeting, and the CA-NTD hexameric lattice forms just prior to capsid release. This model adds an important new dimension to current structural models by proposing the potential order in which key contacts within the immature capsid lattice are made during assembly in cells. IMPORTANCE While much is known about the structure of the completed HIV-1 immature capsid and domains of its component Gag proteins, less is known about the sequence of events leading to formation of the HIV-1 immature capsid. Here we used biochemical and ultrastructural analyses to generate a temporospatial map showing the precise order in which four critical surfaces in Gag act during immature capsid formation in provirus-expressing cells. Because three of these surfaces make important contacts in the hexameric lattices that are found in the completed immature capsid, these data allow us to propose a model for the sequence of events leading to formation of the hexameric lattices. By providing a dynamic view of when and where critical Gag-Gag contacts form during the assembly process and how those contacts function in the nascent capsid, our study provides novel insights into how an immature capsid is built in infected cells.
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Abstract
UNLABELLED Purified retroviral Gag proteins can assemble in vitro to form immature virus-like particles (VLPs). By cryoelectron tomography, Rous sarcoma virus VLPs show an organized hexameric lattice consisting chiefly of the capsid (CA) domain, with periodic stalk-like densities below the lattice. We hypothesize that the structure represented by these densities is formed by amino acid residues immediately downstream of the folded CA, namely, the short spacer peptide SP, along with a dozen flanking residues. These 24 residues comprise the SP assembly (SPA) domain, and we propose that neighboring SPA units in a Gag hexamer coalesce to form a six-helix bundle. Using in vitro assembly, alanine scanning mutagenesis, and biophysical analyses, we have further characterized the structure and function of SPA. Most of the amino acid residues in SPA could not be mutated individually without abrogating assembly, with the exception of a few residues near the N and C termini, as well as three hydrophilic residues within SPA. We interpret these results to mean that the amino acids that do not tolerate mutations contribute to higher-order structures in VLPs. Hydrogen-deuterium exchange analyses of unassembled Gag compared that of assembled VLPs showed strong protection at the SPA region, consistent with a higher-order structure. Circular dichroism revealed that a 29mer SPA peptide shifts from a random coil to a helix in a concentration-dependent manner. Analytical ultracentrifugation showed concentration-dependent self-association of the peptide into a hexamer. Taken together, these results provide strong evidence for the formation of a critical six-helix bundle in Gag assembly. IMPORTANCE The structure of a retrovirus like HIV is created by several thousand molecules of the viral Gag protein, which assemble to form the known hexagonal protein lattice in the virus particle. How the Gag proteins pack together in the lattice is incompletely understood. A short segment of Gag known to be critical for proper assembly has been hypothesized to form a six-helix bundle, which may be the nucleating event that leads to lattice formation. The experiments reported here, using the avian Rous sarcoma virus as a model system, further define the nature of this segment of Gag, show that it is in a higher-order structure in the virus particle, and provide the first direct evidence that it forms a six-helix bundle in retrovirus assembly. Such knowledge may provide underpinnings for the development of antiretroviral drugs that interfere with virus assembly.
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Van Engelenburg SB, Shtengel G, Sengupta P, Waki K, Jarnik M, Ablan SD, Freed EO, Hess HF, Lippincott-Schwartz J. Distribution of ESCRT machinery at HIV assembly sites reveals virus scaffolding of ESCRT subunits. Science 2014; 343:653-6. [PMID: 24436186 DOI: 10.1126/science.1247786] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The human immunodeficiency virus (HIV) hijacks the endosomal sorting complexes required for transport (ESCRT) to mediate virus release from infected cells. The nanoscale organization of ESCRT machinery necessary for mediating viral abscission is unclear. Here, we applied three-dimensional superresolution microscopy and correlative electron microscopy to delineate the organization of ESCRT components at HIV assembly sites. We observed ESCRT subunits localized within the head of budding virions and released particles, with head-localized levels of CHMP2A decreasing relative to Tsg101 and CHMP4B upon virus abscission. Thus, the driving force for HIV release may derive from initial scaffolding of ESCRT subunits within the viral bud interior followed by plasma membrane association and selective remodeling of ESCRT subunits.
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Affiliation(s)
- Schuyler B Van Engelenburg
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
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A two-pronged structural analysis of retroviral maturation indicates that core formation proceeds by a disassembly-reassembly pathway rather than a displacive transition. J Virol 2013; 87:13655-64. [PMID: 24109217 DOI: 10.1128/jvi.01408-13] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Retrovirus maturation involves sequential cleavages of the Gag polyprotein, initially arrayed in a spherical shell, leading to formation of capsids with polyhedral or conical morphology. Evidence suggests that capsids assemble de novo inside maturing virions from dissociated capsid (CA) protein, but the possibility persists of a displacive pathway in which the CA shell remains assembled but is remodeled. Inhibition of the final cleavage between CA and spacer peptide SP1/SP blocks the production of mature capsids. We investigated whether retention of SP might render CA assembly incompetent by testing the ability of Rous sarcoma virus (RSV) CA-SP to assemble in vitro into icosahedral capsids. Capsids were indeed assembled and were indistinguishable from those formed by CA alone, indicating that SP was disordered. We also used cryo-electron tomography to characterize HIV-1 particles produced in the presence of maturation inhibitor PF-46396 or with the cleavage-blocking CA5 mutation. Inhibitor-treated virions have a shell that resembles the CA layer of the immature Gag shell but is less complete. Some CA protein is generated but usually not enough for a mature core to assemble. We propose that inhibitors like PF-46396 bind to the Gag lattice where they deny the protease access to the CA-SP1 cleavage site and prevent the release of CA. CA5 particles, which exhibit no cleavage at the CA-SP1 site, have spheroidal shells with relatively thin walls. It appears that this lattice progresses displacively toward a mature-like state but produces neither conical cores nor infectious virions. These observations support the disassembly-reassembly pathway for core formation.
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Coric P, Turcaud S, Souquet F, Briant L, Gay B, Royer J, Chazal N, Bouaziz S. Synthesis and biological evaluation of a new derivative of bevirimat that targets the Gag CA-SP1 cleavage site. Eur J Med Chem 2013; 62:453-65. [DOI: 10.1016/j.ejmech.2013.01.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 01/09/2013] [Accepted: 01/11/2013] [Indexed: 12/01/2022]
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