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Perilla JR, Hadden-Perilla JA, Gronenborn AM, Polenova T. Integrative structural biology of HIV-1 capsid protein assemblies: combining experiment and computation. Curr Opin Virol 2021; 48:57-64. [PMID: 33901736 DOI: 10.1016/j.coviro.2021.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/11/2021] [Accepted: 03/20/2021] [Indexed: 12/31/2022]
Abstract
HIV-1 is the causative agent of acquired immunodeficiency syndrome (AIDS), a global pandemic that has claimed 32.7 million lives since 1981. Despite decades of research, there is no cure for the disease, with 38 million people currently infected with HIV. Attractive therapeutic targets for drug development are mature HIV-1 capsids, immature Gag polyprotein assemblies, and Gag maturation intermediates, although their complex architectures, pleomorphism, and dynamics render these assemblies challenging for structural biology. The recent development of integrative approaches, combining experimental and computational methods has enabled atomic-level characterization of structures and dynamics of capsid and Gag assemblies, and revealed their interactions with small-molecule inhibitors and host factors. These structures provide important insights that will guide the development of capsid and maturation inhibitors.
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Affiliation(s)
- Juan R Perilla
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, United States; Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Jodi A Hadden-Perilla
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, United States
| | - Angela M Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States; Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States.
| | - Tatyana Polenova
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, United States; Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States.
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2
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Renner N, Mallery DL, Faysal KMR, Peng W, Jacques DA, Böcking T, James LC. A lysine ring in HIV capsid pores coordinates IP6 to drive mature capsid assembly. PLoS Pathog 2021; 17:e1009164. [PMID: 33524070 PMCID: PMC7850482 DOI: 10.1371/journal.ppat.1009164] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 11/13/2020] [Indexed: 02/07/2023] Open
Abstract
The HIV capsid self-assembles a protective conical shell that simultaneously prevents host sensing whilst permitting the import of nucleotides to drive DNA synthesis. This is accomplished through the construction of dynamic, highly charged pores at the centre of each capsid multimer. The clustering of charges required for dNTP import is strongly destabilising and it is proposed that HIV uses the metabolite IP6 to coordinate the pore during assembly. Here we have investigated the role of inositol phosphates in coordinating a ring of positively charged lysine residues (K25) that forms at the base of the capsid pore. We show that whilst IP5, which can functionally replace IP6, engages an arginine ring (R18) at the top of the pore, the lysine ring simultaneously binds a second IP5 molecule. Dose dependent removal of K25 from the pore severely inhibits HIV infection and concomitantly prevents DNA synthesis. Cryo-tomography reveals that K25A virions have a severe assembly defect that inhibits the formation of mature capsid cones. Monitoring both the kinetics and morphology of capsids assembled in vitro reveals that while mutation K25A can still form tubes, the ability of IP6 to drive assembly of capsid cones has been lost. Finally, in single molecule TIRF microscopy experiments, capsid lattices in permeabilised K25 mutant virions are rapidly lost and cannot be stabilised by IP6. These results suggest that the coordination of IP6 by a second charged ring in mature hexamers drives the assembly of conical capsids capable of reverse transcription and infection.
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Affiliation(s)
- Nadine Renner
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - 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, Australia
| | - Wang Peng
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Australia
| | - David A. Jacques
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Australia
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW Sydney, Australia
| | - Leo C. James
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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3
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Xu C, Fischer DK, Rankovic S, Li W, Dick RA, Runge B, Zadorozhnyi R, Ahn J, Aiken C, Polenova T, Engelman AN, Ambrose Z, Rousso I, Perilla JR. Permeability of the HIV-1 capsid to metabolites modulates viral DNA synthesis. PLoS Biol 2020; 18:e3001015. [PMID: 33332391 PMCID: PMC7775124 DOI: 10.1371/journal.pbio.3001015] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 12/31/2020] [Accepted: 11/26/2020] [Indexed: 02/07/2023] Open
Abstract
Reverse transcription, an essential event in the HIV-1 life cycle, requires deoxynucleotide triphosphates (dNTPs) to fuel DNA synthesis, thus requiring penetration of dNTPs into the viral capsid. The central cavity of the capsid protein (CA) hexamer reveals itself as a plausible channel that allows the passage of dNTPs into assembled capsids. Nevertheless, the molecular mechanism of nucleotide import into the capsid remains unknown. Employing all-atom molecular dynamics (MD) simulations, we established that cooperative binding between nucleotides inside a CA hexamer cavity results in energetically favorable conditions for passive translocation of dNTPs into the HIV-1 capsid. Furthermore, binding of the host cell metabolite inositol hexakisphosphate (IP6) enhances dNTP import, while binding of synthesized molecules like benzenehexacarboxylic acid (BHC) inhibits it. The enhancing effect on reverse transcription by IP6 and the consequences of interactions between CA and nucleotides were corroborated using atomic force microscopy, transmission electron microscopy, and virological assays. Collectively, our results provide an atomistic description of the permeability of the HIV-1 capsid to small molecules and reveal a novel mechanism for the involvement of metabolites in HIV-1 capsid stabilization, nucleotide import, and reverse transcription. This study shows that the HIV-1 capsid protein, in addition to its structural role, regulates reverse transcription, an essential metabolic process of the virus, by mediating the import of nucleotides. In addition, host cell metabolites such as inositol phosphates are recruited by the capsid to regulate viral DNA synthesis.
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Affiliation(s)
- Chaoyi Xu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Douglas K. Fischer
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Sanela Rankovic
- Department of Physiology and Cell Biology, Ben-Gurion University of Negev, Beer Sheva, Israel
| | - Wen Li
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Robert A. Dick
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Brent Runge
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Roman Zadorozhnyi
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Jinwoo Ahn
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Christopher Aiken
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Alan N. Engelman
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zandrea Ambrose
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (ZA); (IR); (JRP)
| | - Itay Rousso
- Department of Physiology and Cell Biology, Ben-Gurion University of Negev, Beer Sheva, Israel
- * E-mail: (ZA); (IR); (JRP)
| | - Juan R. Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
- Pittsburgh Center for HIV Protein Interactions (PCHPI), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (ZA); (IR); (JRP)
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4
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Lu M, Russell RW, Bryer AJ, Quinn CM, Hou G, Zhang H, Schwieters CD, Perilla JR, Gronenborn AM, Polenova T. Atomic-resolution structure of HIV-1 capsid tubes by magic-angle spinning NMR. Nat Struct Mol Biol 2020; 27:863-869. [PMID: 32901160 PMCID: PMC7490828 DOI: 10.1038/s41594-020-0489-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/30/2020] [Indexed: 11/16/2022]
Abstract
HIV-1 capsid plays multiple key roles in viral replication, and inhibition of capsid assembly is an attractive target for therapeutic intervention. Here, we report the atomic-resolution structure of the capsid protein (CA) tubes, determined by magic-angle-spinning NMR and data-guided molecular dynamics simulations. Functionally important regions, including the NTD β-hairpin, the cyclophilin A loop, residues in the hexamer center pore, and the NTD-CTD linker region, are well defined. The structure of individual CA chains, their arrangement in the pseudo-hexameric units of the tube and the inter-hexamer interfaces are consistent with those in intact capsid cores and substantially different from the organization in crystal structures, which featured flat hexamers. The inherent curvature in the CA tubes is controlled by conformational variability of residues in the linker region and of dimer and trimer interfaces. The present structure reveals atomic-level detail into capsid architecture and provides important guidance for the design of novel capsid inhibitors.
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Affiliation(s)
- Manman Lu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Ryan W Russell
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Alexander J Bryer
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA.,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Guangjin Hou
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA.,State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian, P. R. China
| | - Huilan Zhang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Charles D Schwieters
- Imaging Sciences Laboratory, Center for Information Technology, National Institutes of Health, Bethesda, MD, USA
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA. .,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Angela M Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. .,Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA. .,Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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5
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Ahmed SF, Quadeer AA, Morales-Jimenez D, McKay MR. Sub-dominant principal components inform new vaccine targets for HIV Gag. Bioinformatics 2020; 35:3884-3889. [PMID: 31250884 DOI: 10.1093/bioinformatics/btz524] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 06/18/2019] [Accepted: 06/26/2019] [Indexed: 12/14/2022] Open
Abstract
MOTIVATION Patterns of mutational correlations, learnt from patient-derived sequences of human immunodeficiency virus (HIV) proteins, are informative of biochemically linked networks of interacting sites that may enable viral escape from the host immune system. Accurate identification of these networks is important for rationally designing vaccines which can effectively block immune escape pathways. Previous computational methods have partly identified such networks by examining the principal components (PCs) of the mutational correlation matrix of HIV Gag proteins. However, driven by a conservative approach, these methods analyze the few dominant (strongest) PCs, potentially missing information embedded within the sub-dominant (relatively weaker) ones that may be important for vaccine design. RESULTS By using sequence data for HIV Gag, complemented by model-based simulations, we revealed that certain networks of interacting sites that appear important for vaccine design purposes are not accurately reflected by the dominant PCs. Rather, these networks are encoded jointly by both dominant and sub-dominant PCs. By incorporating information from the sub-dominant PCs, we identified a network of interacting sites of HIV Gag that associated very strongly with viral control. Based on this network, we propose several new candidates for a potent T-cell-based HIV vaccine. AVAILABILITY AND IMPLEMENTATION Accession numbers of all sequences used and the source code scripts for all analysis and figures reported in this work are available online at https://github.com/faraz107/HIV-Gag-Immunogens. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Syed Faraz Ahmed
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Ahmed A Quadeer
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - David Morales-Jimenez
- Institute of Electronics, Communications and Information Technology, Queen's University Belfast, Belfast, UK
| | - Matthew R McKay
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.,Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
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6
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Sun L, Huang T, Dick A, Meuser ME, Zalloum WA, Chen CH, Ding X, Gao P, Cocklin S, Lee KH, Zhan P, Liu X. Design, synthesis and structure-activity relationships of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as novel HIV-1 capsid inhibitors with promising antiviral activities. Eur J Med Chem 2020; 190:112085. [PMID: 32066010 PMCID: PMC7053825 DOI: 10.1016/j.ejmech.2020.112085] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/18/2019] [Accepted: 01/20/2020] [Indexed: 02/03/2023]
Abstract
HIV-1 CA is involved in different stages of the viral replication cycle, performing essential roles in both early (uncoating, reverse transcription, nuclear import, integration) and late events (assembly). Recent efforts have demonstrated HIV-1 CA protein as a prospective therapeutic target for the development of new antivirals. The most extensively studied CA inhibitor, PF-3450074 (PF-74, discovered by Pfizer), that targets an inter-protomer pocket within the CA hexamer. Herein we reported the design, synthesis, and biological evaluation of a series of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as HIV-1 CA inhibitors based on PF-74 scaffold. Most of the analogues demonstrated potent antiviral activities, among them, the anti-HIV-1 activity of 6a-9 (EC50 = 3.13 μM) is particularly prominent. The SPR binding assay of selected compounds (6a-9, 6a-10, 5b) suggested direct and effective interaction with recombinant CA proteins. The mechanism of action studies also demonstrated that 6a-9 displays the effects in both the early and late stages of HIV-1 replication. To explore the potential binding mode of the here presented analogues, 6a-9 was analyzed by MD simulation to predict its binding to the active site of HIV-1 CA monomer. In conclusion, this novel series of antivirals can serve as a starting point for the development of a new generation of HIV-1 treatment regimen and highlights the potentiality of CA as a therapeutic target.
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Affiliation(s)
- Lin Sun
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Tianguang Huang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Alexej Dick
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Megan E Meuser
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Waleed A Zalloum
- Department of Pharmacy, Faculty of Health Science, American University of Madaba, P.O Box 2882, Amman, 11821, Jordan
| | - Chin-Ho Chen
- Duke University Medical Center, Box 2926, Surgical Oncology Research Facility, Durham, NC, 27710, USA
| | - Xiao Ding
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Ping Gao
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Simon Cocklin
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA.
| | - Kuo-Hsiung Lee
- Natural Products Research Laboratories, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, 27599, USA.
| | - Peng Zhan
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China.
| | - Xinyong Liu
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China.
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7
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Alfadhli A, Staubus AO, Tedbury PR, Novikova M, Freed EO, Barklis E. Analysis of HIV-1 Matrix-Envelope Cytoplasmic Tail Interactions. J Virol 2019; 93:e01079-19. [PMID: 31375589 PMCID: PMC6803273 DOI: 10.1128/jvi.01079-19] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 07/30/2019] [Indexed: 01/08/2023] Open
Abstract
The matrix (MA) domains of HIV-1 precursor Gag (PrGag) proteins direct PrGag proteins to plasma membrane (PM) assembly sites where envelope (Env) protein trimers are incorporated into virus particles. MA targeting to PM sites is facilitated by its binding to phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2], and MA binding to cellular RNAs appears to serve a chaperone function that prevents MA from associating with intracellular membranes prior to arrival at the PI(4,5)P2-rich PM. Investigations have shown genetic evidence of an interaction between MA and the cytoplasmic tails (CTs) of Env trimers that contributes to Env incorporation into virions, but demonstrations of direct MA-CT interactions have proven more difficult. In direct binding assays, we show here that MA binds to Env CTs. Using MA mutants, matrix-capsid (MACA) proteins, and MA proteins incubated in the presence of inositol polyphosphate, we show a correlation between MA trimerization and CT binding. RNA ligands with high affinities for MA reduced MA-CT binding levels, suggesting that MA-RNA binding interferes with trimerization and/or directly or indirectly blocks MA-CT binding. Rough-mapping studies indicate that C-terminal CT helices are involved in MA binding and are in agreement with cell culture studies with replication-competent viruses. Our results support a model in which full-length HIV-1 Env trimers are captured in assembling PrGag lattices by virtue of their binding to MA trimers.IMPORTANCE The mechanism by which HIV-1 envelope (Env) protein trimers assemble into virus particles is poorly understood but involves an interaction between Env cytoplasmic tails (CTs) and the matrix (MA) domain of the structural precursor Gag (PrGag) proteins. We show here that direct binding of MA to Env CTs correlates with MA trimerization, suggesting models where MA lattices regulate CT interactions and/or MA-CT trimer-trimer associations increase the avidity of MA-CT binding. We also show that MA binding to RNA ligands impairs MA-CT binding, potentially by interfering with MA trimerization and/or directly or allosterically blocking MA-CT binding sites. Rough mapping implicated CT C-terminal helices in MA binding, in agreement with cell culture studies on MA-CT interactions. Our results indicate that targeting HIV-1 MA-CT interactions may be a promising avenue for antiviral therapy.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
| | - August O Staubus
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
| | - Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Mariia Novikova
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
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8
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Jiang X, Wu G, Zalloum WA, Meuser ME, Dick A, Sun L, Chen CH, Kang D, Jing L, Jia R, Cocklin S, Lee KH, Liu X, Zhan P. Discovery of novel 1,4-disubstituted 1,2,3-triazole phenylalanine derivatives as HIV-1 capsid inhibitors. RSC Adv 2019; 9:28961-28986. [PMID: 32089839 PMCID: PMC7034945 DOI: 10.1039/c9ra05869a] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The HIV-1 capsid (CA) protein plays crucial roles in both early and late stages of the viral life cycle, which has intrigued researchers to target it to develop anti-HIV drugs. Accordingly, in this research, we report the design, synthesis and biological evaluation of a series of novel phenylalanine derivatives as HIV-1 CA protein inhibitors using the Cu(I)-catalyzed azide and alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. Among this series of inhibitors, compound II-10c displayed a remarkable anti-HIV activity (EC50 = 2.13 μM, CC50 > 35.49 μM). Furthermore, surface plasmon resonance (SPR) binding assays showed that compounds II-10c and PF-74 (lead compound) have similar affinities to HIV-1 CA monomer. Further investigation showed that the weak permeability and water solubility of representative compounds were probably the important factors that restricted their cell-based activity. Preliminary structure-activity relationships (SARs) were inferred based on the activities of these compounds, and their known structure. The most promising new compound was studied with molecular dynamics simulation (MD) to determine the preferred interactions with the drug target. Finally, the activities of members of this series of inhibitors were deeply inspected to find the potential reasons for their anti-HIV-1 activity from various perspectives. This highlights the important factors required to design compounds with improved potency.
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Affiliation(s)
- Xiangyi Jiang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Gaochan Wu
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Waleed A Zalloum
- Department of Pharmacy, Faculty of Health Science, /Department of pharmacy, American University of Madaba, P.O Box 2882, Amman, 11821, Jordan
| | - Megan E Meuser
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Alexej Dick
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Lin Sun
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Chin-Ho Chen
- Duke University Medical Center, Box 2926, Surgical Oncology Research Facility, Durham, NC, 27710, USA
| | - Dongwei Kang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Lanlan Jing
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Ruifang Jia
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Simon Cocklin
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Kuo-Hsiung Lee
- Natural Products Research Laboratories, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Xinyong Liu
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
| | - Peng Zhan
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012, Ji'nan, Shandong, PR China
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9
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Quinn CM, Wang M, Fritz MP, Runge B, Ahn J, Xu C, Perilla JR, Gronenborn AM, Polenova T. Dynamic regulation of HIV-1 capsid interaction with the restriction factor TRIM5α identified by magic-angle spinning NMR and molecular dynamics simulations. Proc Natl Acad Sci U S A 2018; 115:11519-11524. [PMID: 30333189 PMCID: PMC6233135 DOI: 10.1073/pnas.1800796115] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The host factor protein TRIM5α plays an important role in restricting the host range of HIV-1, interfering with the integrity of the HIV-1 capsid. TRIM5 triggers an antiviral innate immune response by functioning as a capsid pattern recognition receptor, although the precise mechanism by which the restriction is imposed is not completely understood. Here we used an integrated magic-angle spinning nuclear magnetic resonance and molecular dynamics simulations approach to characterize, at atomic resolution, the dynamics of the capsid's hexameric and pentameric building blocks, and the interactions with TRIM5α in the assembled capsid. Our data indicate that assemblies in the presence of the pentameric subunits are more rigid on the microsecond to millisecond timescales than tubes containing only hexamers. This feature may be of key importance for controlling the capsid's morphology and stability. In addition, we found that TRIM5α binding to capsid induces global rigidification and perturbs key intermolecular interfaces essential for higher-order capsid assembly, with structural and dynamic changes occurring throughout the entire CA polypeptide chain in the assembly, rather than being limited to a specific protein-protein interface. Taken together, our results suggest that TRIM5α uses several mechanisms to destabilize the capsid lattice, ultimately inducing its disassembly. Our findings add to a growing body of work indicating that dynamic allostery plays a pivotal role in capsid assembly and HIV-1 infectivity.
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Affiliation(s)
- Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
| | - Mingzhang Wang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
| | - Matthew P Fritz
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
| | - Brent Runge
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
| | - Jinwoo Ahn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260
| | - Chaoyi Xu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716;
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
| | - Angela M Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260;
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716;
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, PA 15260
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10
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Discovery of phenylalanine derivatives as potent HIV-1 capsid inhibitors from click chemistry-based compound library. Eur J Med Chem 2018; 158:478-492. [PMID: 30243152 DOI: 10.1016/j.ejmech.2018.09.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 09/05/2018] [Accepted: 09/10/2018] [Indexed: 12/15/2022]
Abstract
The HIV-1 capsid (CA) protein plays essential roles in both early and late stages of HIV-1 replication and is considered an important, clinically unexploited therapeutic target. As such, small drug-like molecules that inhibit this critical HIV-1 protein have become a priority for several groups. Therefore, in this study we explore small molecule targeting of the CA protein, and in particular a very attractive inter-protomer pocket. We report the design, parallel synthesis, and anti-HIV-1 activity evaluation of a series of novel phenylalanine derivatives as HIV-1 CA protein inhibitors synthesized via Cu(I)-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction. We demonstrate robust inhibitory activity over a range of potencies against the HIV-1 NL4-3 reference strain. In particular, compound 13m exhibited the greatest potency and lowest toxicity within this new series with an EC50 value of 4.33 μM and CC50 value of >57.74 μM (SI > 13.33). These values are very similar to the lead compound PF-74 (EC50 = 5.95 μM, CC50 > 70.50 μM, SI > 11.85) in our assay, despite significant structural difference. Furthermore, we demonstrate via surface plasmon resonance (SPR) binding assays that 13m interacts robustly with recombinant HIV-1 CA and exhibits antiviral activity in both the early and late stages of HIV-1 replication. Overall, the novel parallel synthesis and structure-activity relationships (SARs) identified within this study set the foundation for further rational optimization and discovery of CA-targeting compounds with improved potency.
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11
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In vitro assembly of the Rous Sarcoma Virus capsid protein into hexamer tubes at physiological temperature. Sci Rep 2017; 7:2913. [PMID: 28588198 PMCID: PMC5460288 DOI: 10.1038/s41598-017-02060-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 04/06/2017] [Indexed: 12/21/2022] Open
Abstract
During a proteolytically-driven maturation process, the orthoretroviral capsid protein (CA) assembles to form the convex shell that surrounds the viral genome. In some orthoretroviruses, including Rous Sarcoma Virus (RSV), CA carries a short and hydrophobic spacer peptide (SP) at its C-terminus early in the maturation process, which is progressively removed as maturation proceeds. In this work, we show that RSV CA assembles in vitro at near-physiological temperatures, forming hexamer tubes that effectively model the mature capsid surface. Tube assembly is strongly influenced by electrostatic effects, and is a nucleated process that remains thermodynamically favored at lower temperatures, but is effectively arrested by the large Gibbs energy barrier associated with nucleation. RSV CA tubes are multi-layered, being formed by nested and concentric tubes of capsid hexamers. However the spacer peptide acts as a layering determinant during tube assembly. If only a minor fraction of CA-SP is present, multi-layered tube formation is blocked, and single-layered tubes predominate. This likely prevents formation of biologically aberrant multi-layered capsids in the virion. The generation of single-layered hexamer tubes facilitated 3D helical image reconstruction from cryo-electron microscopy data, revealing the basic tube architecture.
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12
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Thenin-Houssier S, Valente ST. HIV-1 Capsid Inhibitors as Antiretroviral Agents. Curr HIV Res 2016; 14:270-82. [PMID: 26957201 DOI: 10.2174/1570162x14999160224103555] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 08/12/2015] [Accepted: 09/01/2015] [Indexed: 01/09/2023]
Abstract
BACKGROUND The infectious human immunodeficiency virus (HIV) particle is characterized by a conical capsid that encloses the viral RNA genome. The capsid is essential for HIV-1 replication and plays crucial roles in both early and late stages of the viral life cycle. Early on, upon fusion of the viral and cellular membranes, the viral capsid is released into the host cell cytoplasm and dissociates in a process known as uncoating, tightly associated with the reverse transcription of the viral genome. During the late stages of viral replication, the Gag polyprotein, precursor of the capsid protein, assemble at the plasma membrane to form immature non-infectious viral particles. After a maturation step by the viral protease, the capsid assembles to form a fullerene-like conical shape characteristic of the mature infectious particle. Mutations affecting the uncoating process, or capsid assembly and maturation, have been shown to hamper viral infectivity. The key role of capsid in viral replication and the absence of approved drugs against this protein have promoted the development of antiretrovirals. Screening based on the inhibition of capsid assembly and virtual screening for molecules binding to the capsid have successfully identified a number of potential small molecule compounds. Unfortunately, none of these molecules is currently used in the clinic. CONCLUSION Here we review the discovery and the mechanism of action of the small molecules and peptides identified as capsid inhibitors, and discuss their therapeutic potential.
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Affiliation(s)
| | - Susana T Valente
- Department Immunology and Microbial Sciences, The Scripps Research Institute, 130 Scripps Way, 3C1, Jupiter, FL 33458, USA.
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13
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Ebselen, a Small-Molecule Capsid Inhibitor of HIV-1 Replication. Antimicrob Agents Chemother 2016; 60:2195-208. [PMID: 26810656 DOI: 10.1128/aac.02574-15] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 01/20/2016] [Indexed: 12/21/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) capsid plays crucial roles in HIV-1 replication and thus represents an excellent drug target. We developed a high-throughput screening method based on a time-resolved fluorescence resonance energy transfer (HTS-TR-FRET) assay, using the C-terminal domain (CTD) of HIV-1 capsid to identify inhibitors of capsid dimerization. This assay was used to screen a library of pharmacologically active compounds, composed of 1,280in vivo-active drugs, and identified ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], an organoselenium compound, as an inhibitor of HIV-1 capsid CTD dimerization. Nuclear magnetic resonance (NMR) spectroscopic analysis confirmed the direct interaction of ebselen with the HIV-1 capsid CTD and dimer dissociation when ebselen is in 2-fold molar excess. Electrospray ionization mass spectrometry revealed that ebselen covalently binds the HIV-1 capsid CTD, likely via a selenylsulfide linkage with Cys198 and Cys218. This compound presents anti-HIV activity in single and multiple rounds of infection in permissive cell lines as well as in primary peripheral blood mononuclear cells. Ebselen inhibits early viral postentry events of the HIV-1 life cycle by impairing the incoming capsid uncoating process. This compound also blocks infection of other retroviruses, such as Moloney murine leukemia virus and simian immunodeficiency virus, but displays no inhibitory activity against hepatitis C and influenza viruses. This study reports the use of TR-FRET screening to successfully identify a novel capsid inhibitor, ebselen, validating HIV-1 capsid as a promising target for drug development.
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14
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Lampel A, Varenik M, Regev O, Gazit E. Hierarchical multi-step organization during viral capsid assembly. Colloids Surf B Biointerfaces 2015; 136:674-7. [DOI: 10.1016/j.colsurfb.2015.10.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 10/06/2015] [Accepted: 10/08/2015] [Indexed: 01/18/2023]
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15
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Bocanegra R, Fuertes MÁ, Rodríguez-Huete A, Neira JL, Mateu MG. Biophysical analysis of the MHR motif in folding and domain swapping of the HIV capsid protein C-terminal domain. Biophys J 2015; 108:338-49. [PMID: 25606682 DOI: 10.1016/j.bpj.2014.11.3472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 11/03/2014] [Accepted: 11/24/2014] [Indexed: 02/06/2023] Open
Abstract
Infection by human immunodeficiency virus (HIV) depends on the function, in virion morphogenesis and other stages of the viral cycle, of a highly conserved structural element, the major homology region (MHR), within the carboxyterminal domain (CTD) of the capsid protein. In a modified CTD dimer, MHR is swapped between monomers. While no evidence for MHR swapping has been provided by structural models of retroviral capsids, it is unknown whether it may occur transiently along the virus assembly pathway. Whatever the case, the MHR-swapped dimer does provide a novel target for the development of anti-HIV drugs based on the concept of trapping a nonnative capsid protein conformation. We have carried out a thermodynamic and kinetic characterization of the domain-swapped CTD dimer in solution. The analysis includes a dissection of the role of conserved MHR residues and other amino acids at the dimerization interface in CTD folding, stability, and dimerization by domain swapping. The results revealed some energetic hotspots at the domain-swapped interface. In addition, many MHR residues that are not in the protein hydrophobic core were nevertheless found to be critical for folding and stability of the CTD monomer, which may dramatically slow down the swapping reaction. Conservation of MHR residues in retroviruses did not correlate with their contribution to domain swapping, but it did correlate with their importance for stable CTD folding. Because folding is required for capsid protein function, this remarkable MHR-mediated conformational stabilization of CTD may help to explain the functional roles of MHR not only during immature capsid assembly but in other processes associated with retrovirus infection. This energetic dissection of the dimerization interface in MHR-swapped CTD may also facilitate the design of anti-HIV compounds that inhibit capsid assembly by conformational trapping of swapped CTD dimers.
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Affiliation(s)
- Rebeca Bocanegra
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid, Spain
| | - Miguel Ángel Fuertes
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid, Spain
| | - Alicia Rodríguez-Huete
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid, Spain
| | - José Luis Neira
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, and Instituto de Biocomputación y Física de los Sistemas Complejos, Zaragoza, Spain
| | - Mauricio G Mateu
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid, Spain.
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16
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López CS, Tsagli SM, Sloan R, Eccles J, Barklis E. Second site reversion of a mutation near the amino terminus of the HIV-1 capsid protein. Virology 2013; 447:95-103. [PMID: 24210103 DOI: 10.1016/j.virol.2013.08.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 08/20/2013] [Accepted: 08/21/2013] [Indexed: 11/19/2022]
Abstract
During HIV-1 morphogenesis, the precursor Gag protein is processed to release capsid (CA) proteins that form the mature virus core. In this process, the CA proteins assemble a lattice in which N-terminal domain (NTD) helices 1-3 are critical for multimer formation. Mature core assembly requires refolding of the N-terminus of CA into a β-hairpin, but the precise contribution of the hairpin core morphogenesis is unclear. We found that mutations at isoleucine 15 (I15), between the β-hairpin and NTD helix 1 are incompatible with proper mature core assembly. However, a compensatory mutation of histidine 12 in the β-hairpin to a tyrosine was selected by long term passage of an I15 mutant virus in T cells. The tyrosine does not interact directly with residue 15, but with NTD helix 3, supporting a model in which β-hairpin folding serves to align helix 3 for mature NTD multimerization.
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Affiliation(s)
- Claudia S López
- Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA.
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17
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Bell NM, Lever AML. HIV Gag polyprotein: processing and early viral particle assembly. Trends Microbiol 2013; 21:136-44. [PMID: 23266279 DOI: 10.1016/j.tim.2012.11.006] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/22/2012] [Accepted: 11/29/2012] [Indexed: 12/22/2022]
Affiliation(s)
- Neil M Bell
- Department of Medicine, University of Cambridge, Level 5, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK
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18
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Chen K, Piszczek G, Carter C, Tjandra N. The maturational refolding of the β-hairpin motif of equine infectious anemia virus capsid protein extends its helix α1 at capsid assembly locus. J Biol Chem 2012. [PMID: 23184932 PMCID: PMC3548464 DOI: 10.1074/jbc.m112.425140] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A retroviral capsid (CA) protein consists of two helical domains, CAN and CAC, which drive hexamer and dimer formations, respectively, to form a capsid lattice. The N-terminal 13 residues of CA refold to a β-hairpin motif upon processing from its precursor polyprotein Gag. The β-hairpin is essential for correct CA assembly but unexpectedly it is not within any CA oligomeric interfaces. To understand the β-hairpin function we studied the full-length CA protein from equine infectious anemia virus (EIAV), a lentivirus sharing the same cone-shaped capsid core as HIV-1. Solution NMR spectroscopy is perfectly suited to study EIAV-CA that dimerizes weaker than HIV-1-CA. Comparison between the wild-type (wt) EIAV-CA and a variant lacking the β-hairpin structure demonstrated that folding of the β-hairpin specifically extended the N terminus of helix α1 from Tyr20 to Pro17. This coil to helix transition involves the conserved sequence of Thr16-Pro17-Arg18 (Ser16-Pro17-Arg18 in HIV-1-CA). The extended region of helix α1 constituted an expanded EIAV-CAN oligomeric interface and overlapped with the HIV-1-CA hexamer-core residue Arg18, helical in structure and pivotal in assembly. Therefore we propose the function of the maturational refolding of the β-hairpin in CA assembly is to extend helix α1 at the N terminus to enhance the CAN oligomerization along the capsid assembly core interface. In addition, NMR resonance line broadening indicated the presence of micro-millisecond exchange kinetics due to the EIAV-CAN domain oligomerization, independent to the faster EIAV-CAC domain dimerization.
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Affiliation(s)
- Kang Chen
- Laboratory of Molecular Biophysics, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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