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Alfadhli A, Romanaggi C, Barklis RL, Barklis E. Second site reversion of HIV-1 envelope protein baseplate mutations maps to the matrix protein. J Virol 2024; 98:e0174223. [PMID: 38193694 PMCID: PMC10878238 DOI: 10.1128/jvi.01742-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 12/07/2023] [Indexed: 01/10/2024] Open
Abstract
The HIV-1 Envelope (Env) protein cytoplasmic tail (CT) recently has been shown to assemble an unusual trimeric baseplate structure that locates beneath Env ectodomain trimers. Mutations at linchpin residues that help organize the baseplate impair virus replication in restrictive T cell lines but not in permissive cell lines. We have identified and characterized a second site suppressor of these baseplate mutations, located at residue 34 in the viral matrix (MA) protein, that rescues viral replication in restrictive cells. The suppressor mutation was dependent on the CT to exert its activity and did not appear to affect Env protein traffic or fusion functions in restrictive cells. Instead, the suppressor mutation increased Env incorporation into virions 3-fold and virus infectivity in single-round infections 10-fold. We also found that a previously described suppressor of Env-incorporation defects that stabilizes the formation of MA trimers was ineffective at rescuing Env baseplate mutations. Our results support an interpretation in which changes at MA residue 34 induce conformational changes that stabilize MA lattice trimer-trimer interactions and/or direct MA-CT associations.IMPORTANCEHow HIV-1 Env trimers assemble into virus particles remains incompletely understood. In restrictive cells, viral incorporation of Env is dependent on the Env CT and on the MA protein, which assembles lattices composed of hexamers of trimers in immature and mature viruses. Recent evidence indicates that CT assembles trimeric baseplate structures that require membrane-proximal residues to interface with trimeric transmembrane domains and C-terminal helices in the CT. We found that mutations of these membrane-proximal residues impaired replication in restrictive cells. This defect was countered by a MA mutation that does not localize to any obvious interprotein regions but was only inefficiently suppressed by a MA mutation that stabilizes MA trimers and has been shown to suppress other CT-dependent Env defects. Our results suggest that efficient suppression of baseplate mutations involves stabilization of MA inter-trimer contacts and/or direct MA-CT associations. These observations shed new light on how Env assembles into virions.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
| | - CeAnn Romanaggi
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
| | - Robin Lid Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, Portland, Oregon, USA
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Alfadhli A, Romanaggi C, Barklis RL, Barklis E. Analysis of HIV-1 envelope cytoplasmic tail effects on viral replication. Virology 2023; 579:54-66. [PMID: 36603533 PMCID: PMC10003682 DOI: 10.1016/j.virol.2022.12.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/27/2022] [Accepted: 12/28/2022] [Indexed: 01/03/2023]
Abstract
Trimers of the HIV-1 envelope (Env) protein perform receptor binding and virus-cell fusion functions during the virus life cycle. The cytoplasmic tail (CT) of Env forms an unusual baseplate structure, and is palmitoylated, rich in arginines, carries trafficking motifs, binds cholesterol, and interacts with host proteins. To dissect CT activities, we examined a panel of Env variants, including CT truncations, mutations, and an extension. We found that whereas all variants could replicate in permissive cells, viruses with CT truncations or baseplate mutations were defective in restrictive cells. We also identified a determinant in HIV-1 amphotericin sensitivity, and characterized variants that escape amphotericin inhibition via viral protease-mediated CT cleavage. Results additionally showed that full-length, his tagged Env can oligomerize and be co-assembled with CT truncations that delete portions of the baseplate, host protein binding sites, and trafficking signals. Our observations illuminate novel aspects of HIV-1 CT structure, interactions, and functions.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, OR, USA
| | - CeAnn Romanaggi
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, OR, USA
| | - Robin Lid Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, OR, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, OR, USA.
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3
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Atomic view of the HIV-1 matrix lattice; implications on virus assembly and envelope incorporation. Proc Natl Acad Sci U S A 2022; 119:e2200794119. [PMID: 35658080 PMCID: PMC9191676 DOI: 10.1073/pnas.2200794119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
SignificanceThe assembly of immature HIV-1 particles is initiated by targeting of the Gag polyproteins to the plasma membrane (PM). Gag binding to the PM is mediated by the N-terminally myristoylated matrix (myrMA) domain. Formation of a Gag lattice on the PM is obligatory for the assembly of immature HIV-1 and envelope (Env) incorporation. The structure of the myrMA lattice presented here provided insights on the molecular factors that stabilize the lattice and hence favor Env incorporation. Our data support a mechanism for Gag binding to the PM during the assembly of immature particles and upon maturation. These findings advance our understanding of a critical step in HIV-1 assembly.
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Valadés-Alcaraz A, Reinosa R, Holguín Á. HIV Transmembrane Glycoprotein Conserved Domains and Genetic Markers Across HIV-1 and HIV-2 Variants. Front Microbiol 2022; 13:855232. [PMID: 35694284 PMCID: PMC9184819 DOI: 10.3389/fmicb.2022.855232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/29/2022] [Indexed: 11/13/2022] Open
Abstract
HIV envelope transmembrane glycoproteins gp41 (HIV-1) and gp36 (HIV-2) present high variability and play a key role in the HIV-host cell membrane's fusion, as a target for human broadly neutralizing antibodies (bnAbs) and drugs. Thus, a better knowledge of amino acid (aa) conservation across structural domains and HIV variants can help to identify conserved targets to direct new therapeutic and diagnostic strategies. All available gp41/gp36 nucleotide sequences were downloaded from Los Alamos National Laboratory (LANL) HIV Sequence Database, selecting 17,078 sequences ascribed to HIV-1 and HIV-2 variants with ≥3 sequences. After aligning and translating into aa with MEGAv6.0, an in-house bioinformatics program (EpiMolBio) was used to identify the most conserved aa and the aa changes that were specific for each variant (V-markers) vs. HXB2/BEN (HIV-1/HIV-2) reference sequence. We analyzed the presence of specific aa changes among V-markers affecting infectivity, gp41 structure, function, or resistance to the enfuvirtide viral fusion inhibitor (T-20). We also inferred the consensus sequences per HIV variant, describing in each HIV-1 group (M, N, O, P) the conservation level along the complete gp41 per structural domain and locating in each binding site the anti-gp41 human Abs (bnAbs and non bnAbs) described in LANL. We found 38.3/59.7% highly conserved aa present in ≥90% of the 16,803/275 gp41/gp36 sequences ascribed to 105/3 HIV-1/HIV-2 variants, with 9/12.6% of them showing complete conservation across LANL sequences. The fusion peptide, its proximal region, the N-heptad repeat, and the membrane-proximal external region were the gp41 domains with ≥84% of conserved aa in the HIV-1 consensus sequence, the target of most Abs. No natural major resistance mutations to T-20 were observed. Our results show, for the first time, a complete conservation study of gp41/gp36 per variant in the largest panel of HIV variants analyzed to date, providing useful information for a more rational design of drugs, vaccines, and molecular detection tests targeting the HIV transmembrane glycoprotein.
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Potential Associations of Mutations within the HIV-1 Env and Gag Genes Conferring Protease Inhibitor (PI) Drug Resistance. MICROBIOLOGY RESEARCH 2021. [DOI: 10.3390/microbiolres12040071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
An increasing number of patients in Africa are experiencing virological failure on a second-line antiretroviral protease inhibitor (PI)-containing regimen, even without resistance-associated mutations in the protease region, suggesting a potential role of other genes in PI resistance. Here, we investigated the prevalence of mutations associated with Lopinavir/Ritonavir (LPV/r) failure in the Envelope gene and the possible coevolution with mutations within the Gag-protease (gag-PR) region. Env and Gag-PR sequences generated from 24 HIV-1 subtype C infected patients failing an LPV/r inclusive treatment regimen and 344 subtype C drug-naïve isolates downloaded from the Los Alamos Database were analyzed. Fisher’s exact test was used to determine the differences in mutation frequency. Bayesian network probability was applied to determine the relationship between mutations occurring within the env and gag-PR regions and LPV/r treatment. Thirty-five mutations in the env region had significantly higher frequencies in LPV/r-treated patients. A combination of Env and Gag-PR mutations was associated with a potential pathway to LPV/r resistance. While Env mutations were not directly associated with LPV/r resistance, they may exert pressure through the Gag and minor PR mutation pathways. Further investigations using site-directed mutagenesis are needed to determine the impact of Env mutations alone and in combination with Gag-PR mutations on viral fitness and LPV/r efficacy.
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Bou-Nader C, Muecksch F, Brown JB, Gordon JM, York A, Peng C, Ghirlando R, Summers MF, Bieniasz PD, Zhang J. HIV-1 matrix-tRNA complex structure reveals basis for host control of Gag localization. Cell Host Microbe 2021; 29:1421-1436.e7. [PMID: 34384537 PMCID: PMC8650744 DOI: 10.1016/j.chom.2021.07.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/24/2021] [Accepted: 07/19/2021] [Indexed: 10/20/2022]
Abstract
The HIV-1 virion structural polyprotein, Gag, is directed to particle assembly sites at the plasma membrane by its N-terminal matrix (MA) domain. MA also binds to host tRNAs. To understand the molecular basis of MA-tRNA interaction and its potential function, we present a co-crystal structure of HIV-1 MA-tRNALys3 complex. The structure reveals a specialized group of MA basic and aromatic residues preconfigured to recognize the distinctive structure of the tRNA elbow. Mutational, cross-linking, fluorescence, and NMR analyses show that the crystallographically defined interface drives MA-tRNA binding in solution and living cells. The structure indicates that MA is unlikely to bind tRNA and membrane simultaneously. Accordingly, single-amino-acid substitutions that abolish MA-tRNA binding caused striking redistribution of Gag to the plasma membrane and reduced HIV-1 replication. Thus, HIV-1 exploits host tRNAs to occlude a membrane localization signal and control the subcellular distribution of its major structural protein.
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Affiliation(s)
- Charles Bou-Nader
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Frauke Muecksch
- Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA
| | - Janae B Brown
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
| | - Jackson M Gordon
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Ashley York
- Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA
| | - Chen Peng
- Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Michael F Summers
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD 21250, USA; Howard Hughes Medical Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
| | - Paul D Bieniasz
- Laboratory of Retrovirology, The Rockefeller University, New York, NY 10065, USA; Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA.
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA.
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7
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Ciftci H, Tateishi H, Koiwai K, Koga R, Anraku K, Monde K, Dağ Ç, Destan E, Yuksel B, Ayan E, Yildirim G, Yigin M, Ertem FB, Shafiei A, Guven O, Besler SO, Sierra RG, Yoon CH, Su Z, Liang M, Acar B, Haliloglu T, Otsuka M, Yumoto F, Fujita M, Senda T, DeMirci H. Structural insight into host plasma membrane association and assembly of HIV-1 matrix protein. Sci Rep 2021; 11:15819. [PMID: 34349176 PMCID: PMC8339130 DOI: 10.1038/s41598-021-95236-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/15/2021] [Indexed: 11/25/2022] Open
Abstract
Oligomerization of Pr55Gag is a critical step of the late stage of the HIV life cycle. It has been known that the binding of IP6, an abundant endogenous cyclitol molecule at the MA domain, has been linked to the oligomerization of Pr55Gag. However, the exact binding site of IP6 on MA remains unknown and the structural details of this interaction are missing. Here, we present three high-resolution crystal structures of the MA domain in complex with IP6 molecules to reveal its binding mode. Additionally, extensive Differential Scanning Fluorimetry analysis combined with cryo- and ambient-temperature X-ray crystallography and GNM-based transfer entropy calculations identify the key residues that participate in IP6 binding. Our data provide novel insights about the multilayered HIV-1 virion assembly process that involves the interplay of IP6 with PIP2, a phosphoinositide essential for the binding of Pr55Gag to membrane. IP6 and PIP2 have neighboring alternate binding sites within the same highly basic region (residues 18-33). This indicates that IP6 and PIP2 bindings are not mutually exclusive and may play a key role in coordinating virion particles' membrane localization. Based on our three different IP6-MA complex crystal structures, we propose a new model that involves IP6 coordination of the oligomerization of outer MA and inner CA domain's 2D layers during assembly and budding.
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Affiliation(s)
- Halilibrahim Ciftci
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, 862-0973, Japan
- Department of Drug Discovery, Science Farm Ltd, Kumamoto, 862-0976, Japan
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Hiroshi Tateishi
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, 862-0973, Japan
| | - Kotaro Koiwai
- Structural Biology Research Center, Institute of Materials Structure Science, KEK/High Energy Accelerator Research Organization, Tsukuba, Ibaraki, 305-0801, Japan
| | - Ryoko Koga
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, 862-0973, Japan
| | - Kensaku Anraku
- Department of Medical Technology, Kumamoto Health Science University, Kumamoto, 861-5598, Japan
| | - Kazuaki Monde
- Department of Microbiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, 860-8556, Japan
| | - Çağdaş Dağ
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey
| | - Ebru Destan
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Busra Yuksel
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Esra Ayan
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Gunseli Yildirim
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Merve Yigin
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - F Betul Ertem
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey
| | - Alaleh Shafiei
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey
| | - Omur Guven
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey
| | - Sabri O Besler
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey
| | - Raymond G Sierra
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Chun Hong Yoon
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Zhen Su
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
- Department of Applied Physics, Stanford University, Stanford, CA, USA
| | - Mengling Liang
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Burcin Acar
- Polymer Research Center, Bogazici University, 34342, Istanbul, Turkey
| | - Turkan Haliloglu
- Department of Chemical Engineering, Bogazici University, 34342, Istanbul, Turkey
- Polymer Research Center, Bogazici University, 34342, Istanbul, Turkey
| | - Masami Otsuka
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, 862-0973, Japan
- Department of Drug Discovery, Science Farm Ltd, Kumamoto, 862-0976, Japan
| | - Fumiaki Yumoto
- Structural Biology Research Center, Institute of Materials Structure Science, KEK/High Energy Accelerator Research Organization, Tsukuba, Ibaraki, 305-0801, Japan
| | - Mikako Fujita
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, 862-0973, Japan.
| | - Toshiya Senda
- Structural Biology Research Center, Institute of Materials Structure Science, KEK/High Energy Accelerator Research Organization, Tsukuba, Ibaraki, 305-0801, Japan.
- School of High Energy Accelerator Science, SOKENDAI University, Tsukuba, Ibaraki, 305-0801, Japan.
- Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, 305-8571, Japan.
| | - Hasan DeMirci
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
- Department of Molecular Biology and Genetics, Koc University, 34450, Istanbul, Turkey.
- Koc University Isbank Center for Infectious Diseases (KUISCID), 34450, Istanbul, Turkey.
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Alfadhli A, Romanaggi C, Barklis RL, Merutka I, Bates TA, Tafesse FG, Barklis E. Capsid-specific nanobody effects on HIV-1 assembly and infectivity. Virology 2021; 562:19-28. [PMID: 34246112 DOI: 10.1016/j.virol.2021.07.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/01/2021] [Accepted: 07/01/2021] [Indexed: 11/15/2022]
Abstract
The capsid (CA) domain of the HIV-1 precursor Gag (PrGag) protein plays multiple roles in HIV-1 replication, and is central to the assembly of immature virions, and mature virus cores. CA proteins themselves are composed of N-terminal domains (NTDs) and C-terminal domains (CTDs). We have investigated the interactions of CA with anti-CA nanobodies, which derive from the antigen recognition regions of camelid heavy chain-only antibodies. The one CA NTD-specific and two CTD-specific nanobodies we analyzed proved sensitive and specific HIV-1 CA detection reagents in immunoassays. When co-expressed with HIV-1 Gag proteins in cells, the NTD-specific nanobody was efficiently assembled into virions and did not perturb virus assembly. In contrast, the two CTD-specific nanobodies reduced PrGag processing, virus release and HIV-1 infectivity. Our results demonstrate the feasibility of Gag-targeted nanobody inhibition of HIV-1.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - CeAnn Romanaggi
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Robin Lid Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Ilaria Merutka
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Timothy A Bates
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Fikadu G Tafesse
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
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9
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Eastep GN, Ghanam RH, Green TJ, Saad JS. Structural characterization of HIV-1 matrix mutants implicated in envelope incorporation. J Biol Chem 2021; 296:100321. [PMID: 33485964 PMCID: PMC7952133 DOI: 10.1016/j.jbc.2021.100321] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 01/05/2021] [Accepted: 01/20/2021] [Indexed: 11/28/2022] Open
Abstract
During the late phase of HIV-1 infection, viral Gag polyproteins are targeted to the plasma membrane (PM) for assembly. Gag localization at the PM is a prerequisite for the incorporation of the envelope protein (Env) into budding particles. Gag assembly and Env incorporation are mediated by the N-terminal myristoylated matrix (MA) domain of Gag. Nonconservative mutations in the trimer interface of MA (A45E, T70R, and L75G) were found to impair Env incorporation and infectivity, leading to the hypothesis that MA trimerization is an obligatory step for Env incorporation. Conversely, Env incorporation can be rescued by a compensatory mutation in the MA trimer interface (Q63R). The impact of these MA mutations on the structure and trimerization properties of MA is not known. In this study, we employed NMR spectroscopy, X-ray crystallography, and sedimentation techniques to characterize the structure and trimerization properties of HIV-1 MA A45E, Q63R, T70R, and L75G mutant proteins. NMR data revealed that these point mutations did not alter the overall structure and folding of MA but caused minor structural perturbations in the trimer interface. Analytical ultracentrifugation data indicated that mutations had a minimal effect on the MA monomer–trimer equilibrium. The high-resolution X-ray structure of the unmyristoylated MA Q63R protein revealed hydrogen bonding between the side chains of adjacent Arg-63 and Ser-67 on neighboring MA molecules, providing the first structural evidence for an additional intermolecular interaction in the trimer interface. These findings advance our knowledge of the interplay of MA trimerization and Env incorporation into HIV-1 particles.
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Affiliation(s)
- Gunnar N Eastep
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Ruba H Ghanam
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Todd J Green
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jamil S Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
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Interaction Interface of Mason-Pfizer Monkey Virus Matrix and Envelope Proteins. J Virol 2020; 94:JVI.01146-20. [PMID: 32796061 DOI: 10.1128/jvi.01146-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 08/03/2020] [Indexed: 02/06/2023] Open
Abstract
Retroviral envelope glycoprotein (Env) is essential for the specific recognition of the host cell and the initial phase of infection. As reported for human immunodeficiency virus (HIV), the recruitment of Env into a retroviral membrane envelope is mediated through its interaction with a Gag polyprotein precursor of structural proteins. This interaction, occurring between the matrix domain (MA) of Gag and the cytoplasmic tail (CT) of the transmembrane domain of Env, takes place at the host cell plasma membrane. To determine whether the MA of Mason-Pfizer monkey virus (M-PMV) also interacts directly with the CT of Env, we mimicked the in vivo conditions in an in vitro experiment by using a CT in its physiological trimeric conformation mediated by the trimerization motif of the GCN4 yeast transcription factor. The MA protein was used at the concentration shifting the equilibrium to its trimeric form. The direct interaction between MA and CT was confirmed by a pulldown assay. Through the combination of nuclear magnetic resonance (NMR) spectroscopy and protein cross-linking followed by mass spectrometry analysis, the residues involved in mutual interactions were determined. NMR has shown that the C terminus of the CT is bound to the C-terminal part of MA. In addition, protein cross-linking confirmed the close proximity of the N-terminal part of CT and the N terminus of MA, which is enabled in vivo by their location at the membrane. These results are in agreement with the previously determined orientation of MA on the membrane and support the already observed mechanisms of M-PMV virus-like particle transport and budding.IMPORTANCE By a combination of nuclear magnetic resonance (NMR) and mass spectroscopy of cross-linked peptides, we show that in contrast to human immunodeficiency virus type 1 (HIV-1), the C-terminal residues of the unstructured cytoplasmic tail of Mason-Pfizer monkey virus (M-PMV) Env interact with the matrix domain (MA). Based on biochemical data and molecular modeling, we propose that individual cytoplasmic tail (CT) monomers of a trimeric complex bind MA molecules belonging to different neighboring trimers, which may stabilize the MA orientation at the membrane by the formation of a membrane-bound net of interlinked Gag and CT trimers. This also corresponds with the concept that the membrane-bound MA of Gag recruits Env through interaction with the full-length CT, while CT truncation during maturation attenuates the interaction to facilitate uncoating. We propose a model suggesting different arrangements of MA-CT complexes between a D-type and C-type retroviruses with short and long CTs, respectively.
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Wen Y, Feigenson GW, Vogt VM, Dick RA. Mechanisms of PI(4,5)P2 Enrichment in HIV-1 Viral Membranes. J Mol Biol 2020; 432:5343-5364. [PMID: 32739462 PMCID: PMC8262684 DOI: 10.1016/j.jmb.2020.07.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 07/12/2020] [Accepted: 07/26/2020] [Indexed: 01/10/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) is critical for HIV-1 virus assembly. The viral membrane is enriched in PIP2, suggesting that the virus assembles at PIP2-rich microdomains. We showed previously that in model membranes PIP2 can form nanoscopic clusters bridged by multivalent cations. Here, using purified proteins we quantitated the binding of HIV-1 Gag-related proteins to giant unilamellar vesicles containing either clustered or free PIP2. Myristoylated MA strongly preferred binding to clustered PIP2. By contrast, unmyristoylated HIV-1 MA, RSV MA, and a PH domain all preferred to interact with free PIP2. We also found that HIV-1 Gag multimerization promotes PIP2 clustering. Truncated Gag proteins comprising the MA, CA, and SP domains (MACASP) or the MA and CA domains (MACA) induced self-quenching of acyl chain-labeled fluorescent PIP2 in liposomes, implying clustering. However, HIV-1 MA itself did not induce PIP2 clustering. A CA inter-hexamer dimer interface mutation led to a loss of induced PIP2 clustering in MACA, indicating the importance of protein multimerization. Cryo-electron tomography of liposomes with bound MACA showed an amorphous protein layer on the membrane surface. Thus, it appears that while protein–protein interactions are required for PIP2 clustering, formation of a regular lattice is not. Protein-induced PIP2 clustering and multivalent cation-induced PIP2 clustering are additive. Taken together, these results provide the first evidence that HIV-1 Gag can selectively target pre-existing PIP2-enriched domains of the plasma membrane for viral assembly, and that Gag multimerization can further enrich PIP2 at assembly sites. These effects could explain the observed PIP2 enrichment in HIV-1.
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Affiliation(s)
- Yi Wen
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Gerald W Feigenson
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Volker M Vogt
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Robert A Dick
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA.
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12
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Murphy RE, Saad JS. The Interplay between HIV-1 Gag Binding to the Plasma Membrane and Env Incorporation. Viruses 2020; 12:E548. [PMID: 32429351 PMCID: PMC7291237 DOI: 10.3390/v12050548] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/14/2020] [Accepted: 05/14/2020] [Indexed: 12/21/2022] Open
Abstract
Advancement in drug therapies and patient care have drastically improved the mortality rates of HIV-1 infected individuals. Many of these therapies were developed or improved upon by using structure-based techniques, which underscore the importance of understanding essential mechanisms in the replication cycle of HIV-1 at the structural level. One such process which remains poorly understood is the incorporation of the envelope glycoprotein (Env) into budding virus particles. Assembly of HIV particles is initiated by targeting of the Gag polyproteins to the inner leaflet of the plasma membrane (PM), a process mediated by the N-terminally myristoylated matrix (MA) domain and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). There is strong evidence that formation of the Gag lattice on the PM is a prerequisite for the incorporation of Env into budding particles. It is also suggested that Env incorporation is mediated by an interaction between its cytoplasmic tail (gp41CT) and the MA domain of Gag. In this review, we highlight the latest developments and current efforts to understand the interplay between gp41CT, MA, and the membrane during assembly. Elucidation of the molecular determinants of Gag-Env-membrane interactions may help in the development of new antiviral therapeutic agents that inhibit particle assembly, Env incorporation and ultimately virus production.
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Affiliation(s)
| | - Jamil S. Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA;
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13
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HIV-1 Matrix Trimerization-Impaired Mutants Are Rescued by Matrix Substitutions That Enhance Envelope Glycoprotein Incorporation. J Virol 2019; 94:JVI.01526-19. [PMID: 31619553 DOI: 10.1128/jvi.01526-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/02/2019] [Indexed: 12/23/2022] Open
Abstract
The matrix (MA) domain of HIV-1 Gag plays key roles in virus assembly by targeting the Gag precursor to the plasma membrane and directing the incorporation of the viral envelope (Env) glycoprotein into virions. The latter function appears to be in part dependent on trimerization of the MA domain of Gag during assembly, as disruption of the MA trimer interface impairs Env incorporation. Conversely, many MA mutations that impair Env incorporation can be rescued by compensatory mutations in the trimer interface. In this study, we sought to investigate further the biological significance of MA trimerization by isolating and characterizing compensatory mutations that rescue MA trimer interface mutants with severely impaired Env incorporation. By serially propagating MA trimerization-defective mutants in T cell lines, we identified a number of changes in MA, both within and distant from the trimer interface. The compensatory mutations located within or near the trimer interface restored Env incorporation and particle infectivity and permitted replication in culture. The structure of the MA lattice was interrogated by measuring the cleavage of the murine leukemia virus (MLV) transmembrane Env protein by the viral protease in MLV Env-pseudotyped HIV-1 particles bearing the MA mutations and by performing crystallographic studies of in vitro-assembled MA lattices. These results demonstrate that rescue is associated with structural alterations in MA organization and rescue of MA domain trimer formation. Our data highlight the significance of the trimer interface of the MA domain of Gag as a critical site of protein-protein interaction during HIV-1 assembly and establish the functional importance of trimeric MA for Env incorporation.IMPORTANCE The immature Gag lattice is a critical structural feature of assembling HIV-1 particles, which is primarily important for virion formation and release. While Gag forms a hexameric lattice, driven primarily by the capsid domain, the MA domain additionally trimerizes where three Gag hexamers meet. MA mutants that are defective for trimerization are deficient for Env incorporation and replication, suggesting a requirement for trimerization of the MA domain of Gag in Env incorporation. This study used a gain-of-function, forced viral evolution approach to rescue HIV-1 mutants that are defective for MA trimerization. Compensatory mutations that rescue virus replication do so by restoring Env incorporation and MA trimer formation. This study supports the importance of MA domain trimerization in HIV-1 replication and the potential of the trimer interface as a therapeutic target.
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14
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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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15
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Murphy RE, Samal AB, Vlach J, Mas V, Prevelige PE, Saad JS. Structural and biophysical characterizations of HIV-1 matrix trimer binding to lipid nanodiscs shed light on virus assembly. J Biol Chem 2019; 294:18600-18612. [PMID: 31640987 PMCID: PMC6901326 DOI: 10.1074/jbc.ra119.010997] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 10/16/2019] [Indexed: 12/17/2022] Open
Abstract
During the late phase of the HIV-1 replication cycle, the viral Gag polyproteins are targeted to the plasma membrane for assembly. The Gag-membrane interaction is mediated by binding of Gag's N-terminal myristoylated matrix (MA) domain to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). The viral envelope (Env) glycoprotein is then recruited to the assembly sites and incorporated into budding particles. Evidence suggests that Env incorporation is mediated by interactions between Gag's MA domain and the cytoplasmic tail of the gp41 subunit of Env (gp41CT). MA trimerization appears to be an obligatory step for this interaction. Insufficient production of a recombinant MA trimer and unavailability of a biologically relevant membrane system have been barriers to detailed structural and biophysical characterization of the putative MA-gp41CT-membrane interactions. Here, we engineered a stable recombinant HIV-1 MA trimer construct by fusing a foldon domain (FD) of phage T4 fibritin to the MA C terminus. Results from NMR experiments confirmed that the FD attachment does not adversely alter the MA structure. Employing hydrogen-deuterium exchange MS, we identified an MA-MA interface in the MA trimer that is implicated in Gag assembly and Env incorporation. Utilizing lipid nanodiscs as a membrane mimetic, we show that the MA trimer binds to membranes 30-fold tighter than does the MA monomer and that incorporation of PI(4,5)P2 and phosphatidylserine enhances the binding of MA to nanodiscs. These findings advance our understanding of a fundamental mechanism in HIV-1 assembly and provide a template for investigating the interaction of MA with gp41CT.
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Affiliation(s)
- R Elliot Murphy
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Alexandra B Samal
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jiri Vlach
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Vicente Mas
- Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Peter E Prevelige
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jamil S Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294.
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16
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Staubus AO, Alfadhli A, Barklis RL, Barklis E. Replication of HIV-1 envelope protein cytoplasmic domain variants in permissive and restrictive cells. Virology 2019; 538:1-10. [PMID: 31550607 DOI: 10.1016/j.virol.2019.09.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 09/13/2019] [Accepted: 09/17/2019] [Indexed: 01/01/2023]
Abstract
Wild type (WT) HIV-1 envelope (Env) protein cytoplasmic tails (CTs) appear to be composed of membrane-proximal, N-terminal unstructured regions, and three C-terminal amphipathic helices. Previous studies have shown that WT and CT-deleted (ΔCT) Env proteins are incorporated into virus particles via different mechanisms. WT Env proteins traffic to cell plasma membranes (PMs), are rapidly internalized, recycle to PMs, and are incorporated into virions in permissive and restrictive cells in a Gag matrix (MA) protein-dependent fashion. In contrast, previously described ΔCT proteins do not appear to be internalized after their arrival to PMs, and do not require MA, but are only incorporated into virions in permissive cell lines. We have analyzed a new set of HIV-1 CT variants with respect to their replication in permissive and restrictive cells. Our results provide novel details as to how CT elements regulate HIV-1 Env protein function.
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Affiliation(s)
- August O Staubus
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Robin Lid Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.
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17
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Barklis E, Stephen AG, Staubus AO, Barklis RL, Alfadhli A. Organization of Farnesylated, Carboxymethylated KRAS4B on Membranes. J Mol Biol 2019; 431:3706-3717. [PMID: 31330153 PMCID: PMC6733658 DOI: 10.1016/j.jmb.2019.07.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/10/2019] [Accepted: 07/12/2019] [Indexed: 11/24/2022]
Abstract
Mutations of the Ras proteins HRAS, KRAS4A, KRAS4B, and NRAS are associated with a high percentage of all human cancers. The proteins are composed of highly homologous N-terminal catalytic or globular domains, plus C-terminal hypervariable regions (HVRs). Post-translational modifications of all RAS HVRs helps target RAS proteins to cellular membrane locations where they perform their signaling functions. For the predominant KRAS4 isoform, KRAS4B, post-translational farnesylation and carboxymethylation, along with a patch of HVR basic residues help foster membrane binding. Recent investigations implicate membrane-bound RAS dimers, oligomers, and nanoclusters as landing pads for effector proteins that relay RAS signals. The details of these RAS signaling platforms have not been elucidated completely, in part due to the difficulties in preparing modified proteins. We have employed properly farnesylated and carboxymethylated KRAS4B in lipid monolayer incubations to examine how the proteins assemble on membranes. Our results reveal novel insights into to how KRAS4B may organize on membranes.
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Affiliation(s)
- Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, 97239, OR, USA.
| | - Andrew G Stephen
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21072, USA
| | - August O Staubus
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, 97239, OR, USA
| | - Robin Lid Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, 97239, OR, USA
| | - Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, 97239, OR, USA
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18
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Lin C, Mendoza-Espinosa P, Rouzina I, Guzmán O, Moreno-Razo JA, Francisco JS, Bruinsma R. Specific inter-domain interactions stabilize a compact HIV-1 Gag conformation. PLoS One 2019; 14:e0221256. [PMID: 31437199 PMCID: PMC6705756 DOI: 10.1371/journal.pone.0221256] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/04/2019] [Indexed: 01/01/2023] Open
Abstract
HIV-1 Gag is a large multidomain poly-protein with flexible unstructured linkers connecting its globular subdomains. It is compact when in solution but assumes an extended conformation when assembled within the immature HIV-1 virion. Here, we use molecular dynamics (MD) simulations to quantitatively characterize the intra-domain interactions of HIV-1 Gag. We find that the matrix (MA) domain and the C-terminal subdomain CActd of the CA capsid domain can form a bound state. The bound state, which is held together primarily by interactions between complementary charged and polar residues, stabilizes the compact state of HIV-1 Gag. We calculate the depth of the attractive free energy potential between the MA/ CActd sites and find it to be about three times larger than the dimerization interaction between the CActd domains. Sequence analysis shows high conservation within the newly-found intra-Gag MA/CActd binding site, as well as its spatial proximity to other well known elements of Gag -such as CActd's SP1 helix region, its inositol hexaphosphate (IP6) binding site and major homology region (MHR), as well as the MA trimerization site. Our results point to a high, but yet undetermined, functional significance of the intra-Gag binding site. Recent biophysical experiments that address the binding specificity of Gag are interpreted in the context of the MA/CActd bound state, suggesting an important role in selective packaging of genomic RNA by Gag.
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Affiliation(s)
- Chen Lin
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Paola Mendoza-Espinosa
- Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, Ciudad de México, México
| | - Ioulia Rouzina
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States of America
| | - Orlando Guzmán
- Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, Ciudad de México, México
| | - José Antonio Moreno-Razo
- Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, Ciudad de México, México
| | - Joseph S. Francisco
- Department of Chemistry, The University of Pennsylvania, Philadelphia, PA, United States of America
| | - Robijn Bruinsma
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, United States of America
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19
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Fernandez MV, Freed EO. Meeting Review: 2018 International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail. Viruses 2018; 10:E613. [PMID: 30405009 PMCID: PMC6266243 DOI: 10.3390/v10110613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 11/03/2018] [Indexed: 01/09/2023] Open
Abstract
Recent developments in defining the role of the lentiviral envelope glycoprotein (Env) cytoplasmic tail (CT) in Env trafficking and incorporation into virus particles have advanced our understanding of viral replication and transmission. To stimulate additional progress in this field, the two-day International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail, co-organized by Eric Freed and James Hoxie, was held at the National Cancer Institute in Frederick, MD (26⁻27 April 2018). The meeting served to bring together experts focused on the role of gp41 in HIV replication and to discuss the emerging mechanisms of CT-dependent trafficking, Env conformation and structure, host protein interaction, incorporation, and viral transmission. The conference was organized around the following three main hot topics in gp41 research: the role of host factors in CT-dependent Env incorporation, Env structure, and CT-mediated trafficking and transmission. This review highlights important topics and the advances in gp41 research that were discussed during the conference.
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Affiliation(s)
- Melissa V Fernandez
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
| | - Eric O Freed
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
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20
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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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21
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Narasimhulu VGS, Bellamy-McIntyre AK, Laumaea AE, Lay CS, Harrison DN, King HAD, Drummer HE, Poumbourios P. Distinct functions for the membrane-proximal ectodomain region (MPER) of HIV-1 gp41 in cell-free and cell-cell viral transmission and cell-cell fusion. J Biol Chem 2018; 293:6099-6120. [PMID: 29496992 DOI: 10.1074/jbc.ra117.000537] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 02/21/2018] [Indexed: 11/06/2022] Open
Abstract
HIV-1 is spread by cell-free virions and by cell-cell viral transfer. We asked whether the structure and function of a broad neutralizing antibody (bNAb) epitope, the membrane-proximal ectodomain region (MPER) of the viral gp41 transmembrane glycoprotein, differ in cell-free and cell-cell-transmitted viruses and whether this difference could be related to Ab neutralization sensitivity. Whereas cell-free viruses bearing W666A and I675A substitutions in the MPER lacked infectivity, cell-associated mutant viruses were able to initiate robust spreading infection. Infectivity was restored to cell-free viruses by additional substitutions in the cytoplasmic tail (CT) of gp41 known to disrupt interactions with the viral matrix protein. We observed contrasting effects on cell-free virus infectivity when W666A was introduced to two transmitted/founder isolates, but both mutants could still mediate cell-cell spread. Domain swapping indicated that the disparate W666A phenotypes of the cell-free transmitted/founder viruses are controlled by sequences in variable regions 1, 2, and 4 of gp120. The sequential passaging of an MPER mutant (W672A) in peripheral blood mononuclear cells enabled selection of viral revertants with loss-of-glycan suppressor mutations in variable region 1, suggesting a functional interaction between variable region 1 and the MPER. An MPER-directed bNAb neutralized cell-free virus but not cell-cell viral spread. Our results suggest that the MPER of cell-cell-transmitted virions has a malleable structure that tolerates mutagenic disruption but is not accessible to bNAbs. In cell-free virions, interactions mediated by the CT impose an alternative MPER structure that is less tolerant of mutagenic alteration and is efficiently targeted by bNAbs.
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Affiliation(s)
- Vani G S Narasimhulu
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004.,the Department of Microbiology and Immunology at the Peter Doherty Institute, University of Melbourne, Parkville, Victoria 3010, and
| | - Anna K Bellamy-McIntyre
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004.,the Departments of Microbiology and
| | - Annamarie E Laumaea
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004.,the Department of Microbiology and Immunology at the Peter Doherty Institute, University of Melbourne, Parkville, Victoria 3010, and
| | - Chan-Sien Lay
- Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - David N Harrison
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004
| | - Hannah A D King
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004.,the Department of Microbiology and Immunology at the Peter Doherty Institute, University of Melbourne, Parkville, Victoria 3010, and
| | - Heidi E Drummer
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004.,the Department of Microbiology and Immunology at the Peter Doherty Institute, University of Melbourne, Parkville, Victoria 3010, and.,the Departments of Microbiology and
| | - Pantelis Poumbourios
- From the Virus Entry and Vaccines Laboratory, Burnet Institute, Melbourne, Victoria 3004, .,the Departments of Microbiology and.,Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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22
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Alfadhli A, Mack A, Harper L, Berk S, Ritchie C, Barklis E. Analysis of quinolinequinone reactivity, cytotoxicity, and anti-HIV-1 properties. Bioorg Med Chem 2016; 24:5618-5625. [PMID: 27663546 DOI: 10.1016/j.bmc.2016.09.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 09/07/2016] [Accepted: 09/10/2016] [Indexed: 12/15/2022]
Abstract
We have analyzed a set of quinolinequinones with respect to their reactivities, cytotoxicities, and anti-HIV-1 properties. Most of the quinolinequinones were reactive with glutathione, and several acted as sulfhydryl crosslinking agents. Quinolinequinones inhibited binding of the HIV-1 matrix protein to RNA to varying degrees, and several quinolinequinones showed the capacity to crosslink HIV-1 matrix proteins in vitro, and HIV-1 structural proteins in virus particles. Cytotoxicity assays yielded quinolinequinone CC50 values in the low micromolar range, reducing the potential therapeutic value of these compounds. However, one compound, 6,7-dichloro-5,8-quinolinequinone potently inactivated HIV-1, suggesting that quinolinequinones may prove useful in the preparation of inactivated virus vaccines or for other virucidal purposes.
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Affiliation(s)
- Ayna Alfadhli
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States
| | - Andrew Mack
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States
| | - Logan Harper
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States
| | - Sam Berk
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States
| | - Christopher Ritchie
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States
| | - Eric Barklis
- Oregon Health & Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, United States.
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