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Lerner G, Ding L, Spearman P. Tryptophan-based motifs in the LLP3 region of the HIV-1 envelope glycoprotein cytoplasmic tail direct trafficking to the endosomal recycling compartment and mediate particle incorporation. J Virol 2023; 97:e0063123. [PMID: 37796124 PMCID: PMC10617417 DOI: 10.1128/jvi.00631-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 08/23/2023] [Indexed: 10/06/2023] Open
Abstract
IMPORTANCE The HIV-1 envelope glycoprotein (Env) is an essential component of the virus and has an exceedingly long cytoplasmic tail (CT). Previous studies have suggested that trafficking signals in the CT interact with host factors to regulate the incorporation of Env into particles. One particular area of interest is termed lentiviral lytic peptide 3 (LLP3), as small deletions in this region have been shown to disrupt Env incorporation. In this study, we identify a small region within LLP3 that regulates how Env associates with cellular recycling compartments. Mutants that reduced or eliminated Env from the recycling compartment also reduced Env incorporation into particles. These findings emphasize the importance of two tryptophan motifs in LLP3 for the incorporation of Env into particles and provide additional support for the idea that the CT interacts with host recycling pathways to determine particle incorporation.
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Affiliation(s)
- Grigoriy Lerner
- Molecular and Cellular Biosciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Lingmei Ding
- Infectious Diseases, Cincinnati Children’s Hospital Medical Center and University of Cincinnati, Cincinnati, Ohio, USA
| | - Paul Spearman
- Infectious Diseases, Cincinnati Children’s Hospital Medical Center and University of Cincinnati, Cincinnati, Ohio, USA
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2
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Lerner G, Ding L, Spearman P. Tryptophan-based motifs in the LLP3 Region of the HIV-1 envelope glycoprotein cytoplasmic tail direct trafficking to the endosomal recycling compartment and mediate particle incorporation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.28.538708. [PMID: 37162911 PMCID: PMC10168361 DOI: 10.1101/2023.04.28.538708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The HIV-1 envelope glycoprotein complex (Env) is incorporated into developing particles at the plasma membrane (PM). The cytoplasmic tail (CT) of Env is known to play an essential role in particle incorporation, while the exact mechanisms underlying this function of the CT remain uncertain. Upon reaching the PM, trafficking signals in the CT interact with host cell endocytic machinery, directing Env into endosomal compartments within the cell. Prior studies have suggested that Env must traffic through the endosomal recycling compartment (ERC) in order for Env to return to the plasma membrane (PM) site of particle assembly. Expression of a truncated form of the ERC-resident trafficking adaptor Rab11-Family Interacting Proteins C (FIP1C) resulted in CT-dependent sequestration of Env in the condensed ERC, preventing recycling of Env to the PM. In this work, the motifs within the CT responsible for ERC localization of Env were systematically mapped. A small deletion encompassing the N-terminal portion of LLP3 eliminated ERC localization. Site-directed mutagenesis identified two tryptophan-based motifs (WE 790-791 and WW 796-797 ) within the N-terminus of LLP3 that were essential for ERC localization of Env. Mutant viruses bearing substitutions in these motifs were deficient in Env incorporation, with a corresponding loss of particle infectivity and a significant defect in replication in a spreading infection assay. These results identify two tryptophan-based motifs at the N-terminal portion of LLP3 that mediate ERC localization and Env incorporation, providing additional supporting evidence for the importance of cellular recycling pathways in HIV-1 particle assembly. IMPORTANCE The HIV-1 envelope glycoprotein (Env) is an essential component of the virus, and has an exceedingly long cytoplasmic tail (CT). Previous studies have suggested that trafficking signals in the CT interact with host factors to regulate the incorporation of Env into particles. One particular area of interest is termed lentiviral lytic peptide 3 (LLP3), as small deletions in this region have been shown to disrupt Env incorporation. In this study, we identify a small region within LLP3 that regulates how Env associates with cellular recycling compartments. Mutants that reduced or eliminated Env from the recycling compartment also reduced Env incorporation into particles. These findings emphasize the importance of two tryptophan motifs in LLP3 to the incorporation of Env into particles, and provide additional support for the idea that the CT interacts with host recycling pathways to determine particle incorporation.
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Affiliation(s)
- Grigoriy Lerner
- Molecular and Cellular Biosciences, University of Cincinnati College of Medicine, Cincinnati, OH
| | - Lingmei Ding
- Infectious Diseases, Cincinnati Children’s Hospital Medical Center and University of Cincinnati, Cincinnati, OH
| | - Paul Spearman
- Infectious Diseases, Cincinnati Children’s Hospital Medical Center and University of Cincinnati, Cincinnati, OH
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3
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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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4
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Cooper L, Schafer A, Li Y, Cheng H, Medegan Fagla B, Shen Z, Nowar R, Dye K, Anantpadma M, Davey RA, Thatcher GRJ, Rong L, Xiong R. Screening and Reverse-Engineering of Estrogen Receptor Ligands as Potent Pan-Filovirus Inhibitors. J Med Chem 2020; 63:11085-11099. [PMID: 32886512 DOI: 10.1021/acs.jmedchem.0c01001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Filoviridae, including Ebola (EBOV) and Marburg (MARV) viruses, are emerging pathogens that pose a serious threat to public health. No agents have been approved to treat filovirus infections, representing a major unmet medical need. The selective estrogen receptor modulator (SERM) toremifene was previously identified from a screen of FDA-approved drugs as a potent EBOV viral entry inhibitor, via binding to EBOV glycoprotein (GP). A focused screen of ER ligands identified ridaifen-B as a potent dual inhibitor of EBOV and MARV. Optimization and reverse-engineering to remove ER activity led to a novel compound 30 (XL-147) showing potent inhibition against infectious EBOV Zaire (0.09 μM) and MARV (0.64 μM). Mutagenesis studies confirmed that inhibition of EBOV viral entry is mediated by the direct interaction with GP. Importantly, compound 30 displayed a broad-spectrum antifilovirus activity against Bundibugyo, Tai Forest, Reston, and Měnglà viruses and is the first submicromolar antiviral agent reported for some of these strains, therefore warranting further development as a pan-filovirus inhibitor.
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Affiliation(s)
- Laura Cooper
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States.,Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Adam Schafer
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Yangfeng Li
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Han Cheng
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Bani Medegan Fagla
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Zhengnan Shen
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Raghad Nowar
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Katherine Dye
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Manu Anantpadma
- Department of Microbiology, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories, Boston, Massachusetts 02118, United States.,Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas 78227, United States
| | - Robert A Davey
- Department of Microbiology, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories, Boston, Massachusetts 02118, United States.,Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas 78227, United States
| | - Gregory R J Thatcher
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Rui Xiong
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois 60612, United States
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Gaisina IN, Peet NP, Wong L, Schafer AM, Cheng H, Anantpadma M, Davey RA, Thatcher GRJ, Rong L. Discovery and Structural Optimization of 4-(Aminomethyl)benzamides as Potent Entry Inhibitors of Ebola and Marburg Virus Infections. J Med Chem 2020; 63:7211-7225. [PMID: 32490678 DOI: 10.1021/acs.jmedchem.0c00463] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The recent Ebola epidemics in West Africa underscore the great need for effective and practical therapies for future Ebola virus outbreaks. We have discovered a new series of remarkably potent small molecule inhibitors of Ebola virus entry. These 4-(aminomethyl)benzamide-based inhibitors are also effective against Marburg virus. Synthetic routes to these compounds allowed for the preparation of a wide variety of structures, including a conformationally restrained subset of indolines (compounds 41-50). Compounds 20, 23, 32, 33, and 35 are superior inhibitors of Ebola (Mayinga) and Marburg (Angola) infectious viruses. Representative compounds (20, 32, and 35) have shown good metabolic stability in plasma and liver microsomes (rat and human), and 32 did not inhibit CYP3A4 nor CYP2C9. These 4-(aminomethyl)benzamides are suitable for further optimization as inhibitors of filovirus entry, with the potential to be developed as therapeutic agents for the treatment and control of Ebola virus infections.
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Affiliation(s)
- Irina N Gaisina
- UICentre (Drug Discovery @ UIC) and Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612, United States.,Chicago BioSolutions Inc., 2242 W Harrison Street, Chicago, Illinois 60612, United States
| | - Norton P Peet
- Chicago BioSolutions Inc., 2242 W Harrison Street, Chicago, Illinois 60612, United States
| | - Letitia Wong
- Chicago BioSolutions Inc., 2242 W Harrison Street, Chicago, Illinois 60612, United States
| | - Adam M Schafer
- College of Medicine, Department of Microbiology and Immunology, University of Illinois at Chicago, 909 S Wolcott Ave, Chicago, Illinois 60612, United States
| | - Han Cheng
- College of Medicine, Department of Microbiology and Immunology, University of Illinois at Chicago, 909 S Wolcott Ave, Chicago, Illinois 60612, United States
| | - Manu Anantpadma
- Texas Biomedical Research Institute, 8715 W Military Drive, San Antonio, Texas 78227, United States.,Department of Microbiology, Boston University, 620 Albany Street, Boston, Massachusetts 02118, United States
| | - Robert A Davey
- Texas Biomedical Research Institute, 8715 W Military Drive, San Antonio, Texas 78227, United States.,Department of Microbiology, Boston University, 620 Albany Street, Boston, Massachusetts 02118, United States
| | - Gregory R J Thatcher
- UICentre (Drug Discovery @ UIC) and Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612, United States
| | - Lijun Rong
- College of Medicine, Department of Microbiology and Immunology, University of Illinois at Chicago, 909 S Wolcott Ave, Chicago, Illinois 60612, United States
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6
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Junková P, Pleskot R, Prchal J, Sýs J, Ruml T. Differences and commonalities in plasma membrane recruitment of the two morphogenetically distinct retroviruses HIV-1 and MMTV. J Biol Chem 2020; 295:8819-8833. [PMID: 32385109 DOI: 10.1074/jbc.ra119.011991] [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: 11/21/2019] [Revised: 05/05/2020] [Indexed: 11/06/2022] Open
Abstract
Retroviral Gag polyproteins are targeted to the inner leaflet of the plasma membrane through their N-terminal matrix (MA) domain. Because retroviruses of different morphogenetic types assemble their immature particles in distinct regions of the host cell, the mechanism of MA-mediated plasma membrane targeting differs among distinct retroviral morphogenetic types. Here, we focused on possible mechanistic differences of the MA-mediated plasma membrane targeting of the B-type mouse mammary tumor virus (MMTV) and C-type HIV-1, which assemble in the cytoplasm and at the plasma membrane, respectively. Molecular dynamics simulations, together with surface mapping, indicated that, similarly to HIV-1, MMTV uses a myristic switch to anchor the MA to the membrane and electrostatically interacts with phosphatidylinositol 4,5-bisphosphate to stabilize MA orientation. We observed that the affinity of MMTV MA to the membrane is lower than that of HIV-1 MA, possibly related to their different topologies and the number of basic residues in the highly basic MA region. The latter probably reflects the requirement of C-type retroviruses for tighter membrane binding, essential for assembly, unlike for D/B-type retroviruses, which assemble in the cytoplasm. A comparison of the membrane topology of the HIV-1 MA, using the surface-mapping method and molecular dynamics simulations, revealed that the residues at the HIV-1 MA C terminus help stabilize protein-protein interactions within the HIV-1 MA lattice at the plasma membrane. In summary, HIV-1 and MMTV share common features such as membrane binding of the MA via hydrophobic interactions and exhibit several differences, including lower membrane affinity of MMTV MA.
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Affiliation(s)
- Petra Junková
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Roman Pleskot
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium; VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Jan Prchal
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic
| | - Jakub Sýs
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic
| | - Tomáš Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic.
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7
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Variable infectivity and conserved engagement in cell-to-cell viral transfer by HIV-1 Env from Clade B transmitted founder clones. Virology 2018; 526:189-202. [PMID: 30415130 DOI: 10.1016/j.virol.2018.10.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 10/16/2018] [Accepted: 10/16/2018] [Indexed: 12/12/2022]
Abstract
HIV-1 transmission is usually initiated by a single viral strain called transmitted/ founder (T/F) virus. In in vitro models, HIV-1 can efficiently spread via cell-free and virological synapse (VS)-mediated cell-to-cell infection. Both modes of infection require the viral glycoprotein Envelope (Env). The efficiency with which T/F Envs initiate VS and mediate cell-to-cell infection has not been well characterized. Here we tested a panel of isogenic HIV-1 molecular clones that carry different Clade B T/F Envs. We found that despite variable infectivity among different Env clones in the two modes of infection, T/F Envs generally mediated efficient VS formation and subsequent cell-to-cell transfer. In contrast, in vitro infectivity of the T/F Env clones was more variable and strongly correlated with intrinsic fusogenicity of various Envs. We speculate that the conservation of cell-to-cell transfer by T/F Env is indicative of a biologically important function of Env.
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8
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Prokšová PG, Lipov J, Zelenka J, Hunter E, Langerová H, Rumlová M, Ruml T. Mason-Pfizer Monkey Virus Envelope Glycoprotein Cycling and Its Vesicular Co-Transport with Immature Particles. Viruses 2018; 10:E575. [PMID: 30347798 PMCID: PMC6212865 DOI: 10.3390/v10100575] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 10/10/2018] [Accepted: 10/18/2018] [Indexed: 12/25/2022] Open
Abstract
The envelope glycoprotein (Env) plays a crucial role in the retroviral life cycle by mediating primary interactions with the host cell. As described previously and expanded on in this paper, Env mediates the trafficking of immature Mason-Pfizer monkey virus (M-PMV) particles to the plasma membrane (PM). Using a panel of labeled RabGTPases as endosomal markers, we identified Env mostly in Rab7a- and Rab9a-positive endosomes. Based on an analysis of the transport of recombinant fluorescently labeled M-PMV Gag and Env proteins, we propose a putative mechanism of the intracellular trafficking of M-PMV Env and immature particles. According to this model, a portion of Env is targeted from the trans-Golgi network (TGN) to Rab7a-positive endosomes. It is then transported to Rab9a-positive endosomes and back to the TGN. It is at the Rab9a vesicles where the immature particles may anchor to the membranes of the Env-containing vesicles, preventing Env recycling to the TGN. These Gag-associated vesicles are then transported to the plasma membrane.
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Affiliation(s)
- Petra Grznárová Prokšová
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
- Imaging methods core facility at BIOCEV, Faculty of Science, Charles University, 252 50 Prague, Czech Republic.
| | - Jan Lipov
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
| | - Jaroslav Zelenka
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
| | - Eric Hunter
- Emory Vaccine Center at the Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA.
| | - Hana Langerová
- Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
| | - Michaela Rumlová
- Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
| | - Tomáš Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
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Russo AG, Eden JS, Enosi Tuipulotu D, Shi M, Selechnik D, Shine R, Rollins LA, Holmes EC, White PA. Viral Discovery in the Invasive Australian Cane Toad ( Rhinella marina) Using Metatranscriptomic and Genomic Approaches. J Virol 2018; 92:JVI.00768-18. [PMID: 29899109 PMCID: PMC6096826 DOI: 10.1128/jvi.00768-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 06/07/2018] [Indexed: 12/19/2022] Open
Abstract
Cane toads are poisonous amphibians that were introduced to Australia in 1935 for insect control. Since then, their population has increased dramatically, and they now threaten many native Australian species. One potential method to control the population is to release a cane toad virus with high mortality rates, yet few cane toad viruses have been characterized. This study samples cane toads from different Australian locations and uses an RNA sequencing and computational approach to find new viruses. We report novel complete picornavirus and retrovirus sequences that were genetically similar to viruses infecting frogs, reptiles, and fish. Using data generated in other studies, we show that these viral sequences are present in cane toads from distinct Australian locations. Three sequences related to circoviruses were also found in the toad genome. The identification of new viral sequences will aid future studies that investigate their prevalence and potential as agents for biocontrol. Cane toads are a notorious invasive species, inhabiting over 1.2 million km2 of Australia and threatening native biodiversity. The release of pathogenic cane toad viruses is one possible biocontrol strategy yet is currently hindered by the poorly described cane toad virome. Metatranscriptomic analysis of 16 cane toad livers revealed the presence of a novel and full-length picornavirus, Rhimavirus A (RhiV-A), a member of a reptile- and amphibian-specific cluster of the Picornaviridae basal to the Kobuvirus-like group. In the combined liver transcriptome, we also identified a complete genome sequence of a distinct epsilonretrovirus, Rhinella marina endogenous retrovirus (RMERV). The recently sequenced cane toad genome contains 8 complete RMERV proviruses as well as 21 additional truncated insertions. The oldest full-length RMERV provirus was estimated to have inserted 1.9 million years ago (MYA). To screen for these viral sequences in additional toads, we analyzed publicly available transcriptomes from six diverse Australian locations. RhiV-A transcripts were identified in toads sampled from three locations across 1,000 km of Australia, stretching to the current Western Australia (WA) invasion front, while RMERV transcripts were observed at all six sites. Finally, we scanned the cane toad genome for nonretroviral endogenous viral elements, finding three sequences related to small DNA viruses in the family Circoviridae. This shows ancestral circoviral infection with subsequent genomic integration. The identification of these current and past viral infections enriches our knowledge of the cane toad virome, an understanding of which will facilitate future work on infection and disease in this important invasive species. IMPORTANCE Cane toads are poisonous amphibians that were introduced to Australia in 1935 for insect control. Since then, their population has increased dramatically, and they now threaten many native Australian species. One potential method to control the population is to release a cane toad virus with high mortality rates, yet few cane toad viruses have been characterized. This study samples cane toads from different Australian locations and uses an RNA sequencing and computational approach to find new viruses. We report novel complete picornavirus and retrovirus sequences that were genetically similar to viruses infecting frogs, reptiles, and fish. Using data generated in other studies, we show that these viral sequences are present in cane toads from distinct Australian locations. Three sequences related to circoviruses were also found in the toad genome. The identification of new viral sequences will aid future studies that investigate their prevalence and potential as agents for biocontrol.
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Affiliation(s)
- Alice G. Russo
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - John-Sebastian Eden
- Marie Bashir Institute for Infectious Disease and Biosecurity, School of Life and Environmental Sciences and Sydney Medical School, Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
- The Westmead Institute of Medical Research, Centre for Virus Research, Westmead, NSW, Australia
| | - Daniel Enosi Tuipulotu
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Mang Shi
- Marie Bashir Institute for Infectious Disease and Biosecurity, School of Life and Environmental Sciences and Sydney Medical School, Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Daniel Selechnik
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Richard Shine
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Lee Ann Rollins
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Edward C. Holmes
- Marie Bashir Institute for Infectious Disease and Biosecurity, School of Life and Environmental Sciences and Sydney Medical School, Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Peter A. White
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
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10
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Beraud C, Lemaire M, Perez Bercoff D. Reassessment of the capacity of the HIV-1 Env cytoplasmic domain to trigger NF-κB activation. Virol J 2018; 15:35. [PMID: 29454367 PMCID: PMC5816530 DOI: 10.1186/s12985-018-0941-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/31/2018] [Indexed: 02/07/2023] Open
Abstract
The cytoplasmic domain of lentiviral Envelopes (EnvCD) ensures Env incorporation into nascent virions and regulates Env trafficking to and from the plasma membrane. It has also been reported to promote transcription from the viral LTR both directly and indirectly. Noticeably, the HIV-1 and SIVmac239 EnvCDs were described to trigger nuclear translocation of NF-κB (Postler, Cell Host Microbes 2012). Given the paramount importance of identifying viral and host factors regulating HIV transcription, cellular signaling pathways and latency, and given that viral replication capacity is dependent on Env, we asked whether HIV EnvCDs from different HIV-1 subtypes differently modulated NF-κB. To that aim, we evaluated the ability of primary HIV-1 Envs from subtypes B and C to activate the NF-κB pathway. Primary subtype B and C Envs all failed to activate the NF-κB pathway. In contrast, when the EnvCD of HIV-1 Envs was fused to the the CD8-α chain, it induced ~ 10-fold increase in NF-κB induction, and this increase was much stronger with a truncated form of the HIV EnvCD lacking the 76 C-terminal residues and containing the proposed TAK-1 binding domain. Our results indicate that the HIV-1 EnvCD is unlikely to trigger the NF-κB pathway in its native trimeric form.
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Affiliation(s)
- Cyprien Beraud
- Department of Infection and Immunity, Molecular Signaling and Virus-Host Interactions group, Luxembourg Institute of Health, 29, rue Henri Koch, L-4354, Esch-sur-Alzette, Luxembourg
| | - Morgane Lemaire
- Department of Infection and Immunity, Molecular Signaling and Virus-Host Interactions group, Luxembourg Institute of Health, 29, rue Henri Koch, L-4354, Esch-sur-Alzette, Luxembourg
| | - Danielle Perez Bercoff
- Department of Infection and Immunity, Molecular Signaling and Virus-Host Interactions group, Luxembourg Institute of Health, 29, rue Henri Koch, L-4354, Esch-sur-Alzette, Luxembourg.
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11
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HIV-1 Envelope Glycoprotein Trafficking through the Endosomal Recycling Compartment Is Required for Particle Incorporation. J Virol 2018; 92:JVI.01893-17. [PMID: 29212940 DOI: 10.1128/jvi.01893-17] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 11/22/2017] [Indexed: 01/31/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) encodes specific trafficking signals within its long cytoplasmic tail (CT) that regulate incorporation into HIV-1 particles. Rab11-family interacting protein 1C (FIP1C) and Rab14 are host trafficking factors required for Env particle incorporation, suggesting that Env undergoes sorting from the endosomal recycling compartment (ERC) to the site of particle assembly on the plasma membrane. We disrupted outward sorting from the ERC by expressing a C-terminal fragment of FIP1C (FIP1C560-649) and examined the consequences on Env trafficking and incorporation into particles. FIP1C560-649 reduced cell surface levels of Env and prevented its incorporation into HIV-1 particles. Remarkably, Env was trapped in an exaggerated perinuclear ERC in a CT-dependent manner. Mutation of either the Yxxϕ endocytic motif or the YW795 motif in the CT prevented Env trapping in the ERC and restored incorporation into particles. In contrast, simian immunodeficiency virus SIVmac239 Env was not retained in the ERC, while substitution of the HIV-1 CT for the SIV CT resulted in SIV Env retention in this compartment. These results provide the first direct evidence that Env traffics through the ERC and support a model whereby HIV-1 Env is specifically targeted to the ERC prior to FIP1C- and CT-dependent outward sorting to the particle assembly site on the plasma membrane.IMPORTANCE The HIV envelope protein is an essential component of the viral particle. While many aspects of envelope protein structure and function have been established, the pathway it follows in the cell prior to reaching the site of particle assembly is not well understood. The envelope protein has a very long cytoplasmic tail that interacts with the host cell trafficking machinery. Here, we utilized a truncated form of the trafficking adaptor FIP1C protein to arrest the intracellular transport of the envelope protein, demonstrating that it becomes trapped inside the cell within the endosomal recycling compartment. Intracellular trapping resulted in a loss of envelope protein on released particles and a corresponding loss of infectivity. Mutations of specific trafficking motifs in the envelope protein tail prevented its trapping in the recycling compartment. These results establish that trafficking to the endosomal recycling compartment is an essential step in HIV envelope protein particle incorporation.
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Th17 Cells Are Preferentially Infected Very Early after Vaginal Transmission of SIV in Macaques. Cell Host Microbe 2016; 19:529-40. [PMID: 27078070 DOI: 10.1016/j.chom.2016.03.005] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 02/22/2016] [Accepted: 03/15/2016] [Indexed: 02/07/2023]
Abstract
The difficulty in detecting rare infected cells immediately after mucosal HIV transmission has hindered our understanding of the initial cells targeted by the virus. Working with the macaque simian immunodeficiency virus (SIV) vaginal challenge model, we developed methodology to identify discrete foci of SIV (mac239) infection 48 hr after vaginal inoculation. We find infectious foci throughout the reproductive tract, from labia to ovary. Phenotyping infected cells reveals that SIV has a significant bias for infection of CCR6+ CD4+ T cells. SIV-infected cells expressed the transcriptional regulator RORγt, confirming that the initial target cells are specifically of the Th17 lineage. Furthermore, we detect host responses to infection, as evidenced by apoptosis, cell lysis, and phagocytosis of infected cells. Thus, our analysis identifies Th17-lineage CCR6+ CD4+ T cells as primary targets of SIV during vaginal transmission. This opens new opportunities for interventions to protect these cells and prevent HIV transmission.
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The Envelope Cytoplasmic Tail of HIV-1 Subtype C Contributes to Poor Replication Capacity through Low Viral Infectivity and Cell-to-Cell Transmission. PLoS One 2016; 11:e0161596. [PMID: 27598717 PMCID: PMC5012655 DOI: 10.1371/journal.pone.0161596] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/08/2016] [Indexed: 12/15/2022] Open
Abstract
The cytoplasmic tail (gp41CT) of the HIV-1 envelope (Env) mediates Env incorporation into virions and regulates Env intracellular trafficking. Little is known about the functional impact of variability in this domain. To address this issue, we compared the replication of recombinant virus pairs carrying the full Env (Env viruses) or the Env ectodomain fused to the gp41CT of NL4.3 (EnvEC viruses) (12 subtype C and 10 subtype B pairs) in primary CD4+ T-cells and monocyte-derived-macrophages (MDMs). In CD4+ T-cells, replication was as follows: B-EnvEC = B-Env>C-EnvEC>C-Env, indicating that the gp41CT of subtype C contributes to the low replicative capacity of this subtype. In MDMs, in contrast, replication capacity was comparable for all viruses regardless of subtype and of gp41CT. In CD4+ T-cells, viral entry, viral release and viral gene expression were similar. However, infectivity of free virions and cell-to-cell transmission of C-Env viruses released by CD4+ T-cells was lower, suggestive of lower Env incorporation into virions. Subtype C matrix only minimally rescued viral replication and failed to restore infectivity of free viruses and cell-to-cell transmission. Taken together, these results show that polymorphisms in the gp41CT contribute to viral replication capacity and suggest that the number of Env spikes per virion may vary across subtypes. These findings should be taken into consideration in the design of vaccines.
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Stieh DJ, King DF, Klein K, Aldon Y, McKay PF, Shattock RJ. Discrete partitioning of HIV-1 Env forms revealed by viral capture. Retrovirology 2015; 12:81. [PMID: 26399966 PMCID: PMC4581120 DOI: 10.1186/s12977-015-0207-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/15/2015] [Indexed: 11/25/2022] Open
Abstract
Background The structure of HIV-1 envelope glycoprotein (Env) is flexible and heterogeneous on whole virions. Although functional Env complexes are thought to require trimerization of cleaved gp41/gp120 heterodimers, variable processing can result in the potential incorporation of non-functional uncleaved proteins (gp160), non-trimeric arrangements of gp41/gp120 heterodimers, and gp120 depleted gp41 stumps. The potential distribution of functional and non-functional Env forms across replication-competent viral populations may have important implications for neutralizing and non-neutralizing antibody functions. This study applied an immuno-bead viral capture assay (VCA) to interrogate the potential distribution (heterologous vs homologous) of functional and non-functional forms of virion associated Env. Results The VCA revealed a significant association between depletion of infectious virions and virion Env incorporation, but not between infectivity and p24-gag. Three distinct subpopulations of virions were identified within pools of genetically homogenous viral particles. Critically, a significant subpopulation of infectious virions were exclusively captured by neutralizing antibodies (nAbs) indicative of a homologous distribution of functional trimeric Env forms. A second infectious subpopulation bound both neutralizing and non-neutralizing antibodies (nnAbs) representative of a heterologous distribution of Env forms, while a third non-infectious subpopulation was predominantly bound by nnAbs recognizing gp41 stumps. Conclusions The observation that a distinct and significant subpopulation of infectious virions is exclusively captured by neutralizing antibodies has important implications for understanding antibody binding and neutralization, as well as other antibody effector functions. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0207-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Daniel J Stieh
- Department of Cellular and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.
| | - Deborah F King
- Mucosal Infection and Immunity Group, Section of Infectious Diseases, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
| | - Katja Klein
- Mucosal Infection and Immunity Group, Section of Infectious Diseases, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
| | - Yoann Aldon
- Mucosal Infection and Immunity Group, Section of Infectious Diseases, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
| | - Paul F McKay
- Mucosal Infection and Immunity Group, Section of Infectious Diseases, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
| | - Robin J Shattock
- Mucosal Infection and Immunity Group, Section of Infectious Diseases, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
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Ye J. Roles of regulated intramembrane proteolysis in virus infection and antiviral immunity. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1828:2926-32. [PMID: 24099010 PMCID: PMC3837687 DOI: 10.1016/j.bbamem.2013.05.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 01/24/2023]
Abstract
Regulated intramembrane proteolysis (RIP) is a signaling mechanism through which transmembrane precursor proteins are cleaved to liberate their cytoplasmic and/or luminal/extracellular fragments from membranes so that these fragments are able to function at a new location. Recent studies have indicated that this proteolytic reaction plays an important role in host-virus interaction. On one hand, RIP transfers the signal from the endoplasmic reticulum (ER) to nucleus to activate antiviral genes in response to alteration of the ER caused by viral infection. On the other hand, RIP can be hijacked by virus to process transmembrane viral protein precursors and to destroy transmembrane antiviral proteins. Understanding this Yin and Yang side of RIP may lead to new strategies to combat viral infection. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Jin Ye
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9046, USA.
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16
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Wang J, Cheng H, Ratia K, Varhegyi E, Hendrickson WG, Li J, Rong L. A comparative high-throughput screening protocol to identify entry inhibitors of enveloped viruses. ACTA ACUST UNITED AC 2013; 19:100-7. [PMID: 23821643 DOI: 10.1177/1087057113494405] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Emerging and reemerging human viral pathogens pose great public health concerns since therapeutics against these viruses are limited. Thus, there is an urgent need to develop novel drugs that can block infection of either a specific virus or a number of viruses. Viral entry is thought to be an ideal target for potential therapeutic prevention. One of the challenges of developing antivirals is that most of these viruses are highly pathogenic and therefore require high biosafety-level containment. In this study, we have adopted a comparative high-throughput screening protocol to identify entry inhibitors for three enveloped viruses (Marburg virus, influenza virus H5N1, and Lassa virus) using a human immunodeficiency virus-based pseudotyping platform. We demonstrate the utility of this approach by screening a small compound library and identifying putative entry inhibitors for these viruses. One major advantage of this protocol is to reduce the number of false positives in hit selection, and we believe that the protocol is useful for inhibitor screening for many enveloped viruses.
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Affiliation(s)
- Juan Wang
- 1Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, IL, USA
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Santos da Silva E, Mulinge M, Perez Bercoff D. The frantic play of the concealed HIV envelope cytoplasmic tail. Retrovirology 2013; 10:54. [PMID: 23705972 PMCID: PMC3686653 DOI: 10.1186/1742-4690-10-54] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 05/01/2013] [Indexed: 11/18/2022] Open
Abstract
Lentiviruses have unusually long envelope (Env) cytoplasmic tails, longer than those of other retroviruses. Whereas the Env ectodomain has received much attention, the gp41 cytoplasmic tail (gp41-CT) is one of the least studied parts of the virus. It displays relatively high conservation compared to the rest of Env. It has been long established that the gp41-CT interacts with the Gag precursor protein to ensure Env incorporation into the virion. The gp41-CT contains distinct motifs and domains that mediate both intensive Env intracellular trafficking and interactions with numerous cellular and viral proteins, optimizing viral infectivity. Although they are not fully understood, a multiplicity of interactions between the gp41-CT and cellular factors have been described over the last decade; these interactions illustrate how Env expression and incorporation into virions is a finely tuned process that has evolved to best exploit the host system with minimized genetic information. This review addresses the structure and topology of the gp41-CT of lentiviruses (mainly HIV and SIV), their domains and believed functions. It also considers the cellular and viral proteins that have been described to interact with the gp41-CT, with a particular focus on subtype-related polymorphisms.
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18
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Qi M, Williams JA, Chu H, Chen X, Wang JJ, Ding L, Akhirome E, Wen X, Lapierre LA, Goldenring JR, Spearman P. Rab11-FIP1C and Rab14 direct plasma membrane sorting and particle incorporation of the HIV-1 envelope glycoprotein complex. PLoS Pathog 2013; 9:e1003278. [PMID: 23592992 PMCID: PMC3616983 DOI: 10.1371/journal.ppat.1003278] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Accepted: 02/12/2013] [Indexed: 11/19/2022] Open
Abstract
The incorporation of the envelope glycoprotein complex (Env) onto the developing particle is a crucial step in the HIV-1 lifecycle. The long cytoplasmic tail (CT) of Env is required for the incorporation of Env onto HIV particles in T cells and macrophages. Here we identify the Rab11a-FIP1C/RCP protein as an essential cofactor for HIV-1 Env incorporation onto particles in relevant human cells. Depletion of FIP1C reduced Env incorporation in a cytoplasmic tail-dependent manner, and was rescued by replenishment of FIP1C. FIP1C was redistributed out of the endosomal recycling complex to the plasma membrane by wild type Env protein but not by CT-truncated Env. Rab14 was required for HIV-1 Env incorporation, and FIP1C mutants incapable of binding Rab14 failed to rescue Env incorporation. Expression of FIP1C and Rab14 led to an enhancement of Env incorporation, indicating that these trafficking factors are normally limiting for CT-dependent Env incorporation onto particles. These findings support a model for HIV-1 Env incorporation in which specific targeting to the particle assembly microdomain on the plasma membrane is mediated by FIP1C and Rab14. Enveloped viruses must develop strategies to ensure that a sufficient quantity of their receptor-binding envelope proteins are incorporated onto the surface of viruses as they form. The HIV envelope glycoprotein is specifically incorporated onto assembling virions in relevant cells such as T lymphocytes in a manner that requires its long cytoplasmic tail. The mechanism underlying this specific incorporation has remained unknown. Here, we identify a cellular trafficking pathway that is required for the incorporation of HIV envelope onto virions. A combination of the adaptor protein Rab11-FIP1C and Rab14 directs the envelope protein onto assembling virions, and loss of either of these host factors results in the production of virus particles lacking envelope. We also found that FIP1C was required for replication in T cell lines. This study identifies a trafficking complex required for HIV envelope incorporation and for the formation of infectious HIV particles.
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Affiliation(s)
- Mingli Qi
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Janice A. Williams
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Hin Chu
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Xuemin Chen
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Jaang-Jiun Wang
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Lingmei Ding
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Ehiole Akhirome
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Xiaoyun Wen
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Lynne A. Lapierre
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - James R. Goldenring
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail: (JRG); (PS)
| | - Paul Spearman
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail: (JRG); (PS)
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Retroviral env glycoprotein trafficking and incorporation into virions. Mol Biol Int 2012; 2012:682850. [PMID: 22811910 PMCID: PMC3395148 DOI: 10.1155/2012/682850] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/08/2012] [Accepted: 05/31/2012] [Indexed: 11/17/2022] Open
Abstract
Together with the Gag protein, the Env glycoprotein is a major retroviral structural protein and is essential for forming infectious virus particles. Env is synthesized, processed, and transported to certain microdomains at the plasma membrane and takes advantage of the same host machinery for its trafficking as that used by cellular glycoproteins. Incorporation of Env into progeny virions is probably mediated by the interaction between Env and Gag, in some cases with the additional involvement of certain host factors. Although several general models have been proposed to explain the incorporation of retroviral Env glycoproteins into virions, the actual mechanism for this process is still unclear, partly because structural data on the Env protein cytoplasmic tail is lacking. This paper presents the current understanding of the synthesis, trafficking, and virion incorporation of retroviral Env proteins.
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20
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Gnanakaran S, Bhattacharya T, Daniels M, Keele BF, Hraber PT, Lapedes AS, Shen T, Gaschen B, Krishnamoorthy M, Li H, Decker JM, Salazar-Gonzalez JF, Wang S, Jiang C, Gao F, Swanstrom R, Anderson JA, Ping LH, Cohen MS, Markowitz M, Goepfert PA, Saag MS, Eron JJ, Hicks CB, Blattner WA, Tomaras GD, Asmal M, Letvin NL, Gilbert PB, DeCamp AC, Magaret CA, Schief WR, Ban YEA, Zhang M, Soderberg KA, Sodroski JG, Haynes BF, Shaw GM, Hahn BH, Korber B. Recurrent signature patterns in HIV-1 B clade envelope glycoproteins associated with either early or chronic infections. PLoS Pathog 2011; 7:e1002209. [PMID: 21980282 PMCID: PMC3182927 DOI: 10.1371/journal.ppat.1002209] [Citation(s) in RCA: 113] [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: 12/05/2010] [Accepted: 06/26/2011] [Indexed: 12/15/2022] Open
Abstract
Here we have identified HIV-1 B clade Envelope (Env) amino acid signatures from early in infection that may be favored at transmission, as well as patterns of recurrent mutation in chronic infection that may reflect common pathways of immune evasion. To accomplish this, we compared thousands of sequences derived by single genome amplification from several hundred individuals that were sampled either early in infection or were chronically infected. Samples were divided at the outset into hypothesis-forming and validation sets, and we used phylogenetically corrected statistical strategies to identify signatures, systematically scanning all of Env. Signatures included single amino acids, glycosylation motifs, and multi-site patterns based on functional or structural groupings of amino acids. We identified signatures near the CCR5 co-receptor-binding region, near the CD4 binding site, and in the signal peptide and cytoplasmic domain, which may influence Env expression and processing. Two signatures patterns associated with transmission were particularly interesting. The first was the most statistically robust signature, located in position 12 in the signal peptide. The second was the loss of an N-linked glycosylation site at positions 413-415; the presence of this site has been recently found to be associated with escape from potent and broad neutralizing antibodies, consistent with enabling a common pathway for immune escape during chronic infection. Its recurrent loss in early infection suggests it may impact fitness at the time of transmission or during early viral expansion. The signature patterns we identified implicate Env expression levels in selection at viral transmission or in early expansion, and suggest that immune evasion patterns that recur in many individuals during chronic infection when antibodies are present can be selected against when the infection is being established prior to the adaptive immune response.
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Affiliation(s)
- S. Gnanakaran
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Tanmoy Bhattacharya
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
| | - Marcus Daniels
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Brandon F. Keele
- SAIC-Frederick, National Cancer Institute, Frederick, Maryland, United States of America
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Peter T. Hraber
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Alan S. Lapedes
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Tongye Shen
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- Center for Molecular Biophysics and Department of Biochemistry, Cellular & Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Brian Gaschen
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Mohan Krishnamoorthy
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Hui Li
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Julie M. Decker
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Jesus F. Salazar-Gonzalez
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Shuyi Wang
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Chunlai Jiang
- National Engineering Laboratory of AIDS Vaccine School of Life Science, Jilin University, Changchun, China
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - Feng Gao
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - Ronald Swanstrom
- Department of Biochemistry and Biophysics and the Division of Infectious Diseases Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Jeffrey A. Anderson
- Department of Biochemistry and Biophysics and the Division of Infectious Diseases Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Li-Hua Ping
- Department of Biochemistry and Biophysics and the Division of Infectious Diseases Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Myron S. Cohen
- Department of Biochemistry and Biophysics and the Division of Infectious Diseases Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Martin Markowitz
- Aaron Diamond AIDS Research Center, an affiliate of the Rockefeller University, New York, New York, United States of America
| | - Paul A. Goepfert
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Michael S. Saag
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Joseph J. Eron
- Department of Biochemistry and Biophysics and the Division of Infectious Diseases Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Charles B. Hicks
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - William A. Blattner
- Institute of Human Virology, University of Maryland, School of Medicine, Baltimore, Maryland, United States of America
| | - Georgia D. Tomaras
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - Mohammed Asmal
- Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Norman L. Letvin
- Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- Division of Viral Pathogenesis, Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Peter B. Gilbert
- Vaccine Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United State of America
| | - Allan C. DeCamp
- Vaccine Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United State of America
| | - Craig A. Magaret
- Vaccine Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United State of America
| | - William R. Schief
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Yih-En Andrew Ban
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Arzeda Corporation, Seattle, Washington, United States of America
| | - Ming Zhang
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia, United States of America
| | - Kelly A. Soderberg
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - Joseph G. Sodroski
- Dana-Farber Cancer Institute, Department of Cancer Immunology and AIDS, Boston, Massachusetts, United States of America
| | - Barton F. Haynes
- Duke University Medical Center, the Departments of Medicine and Surgery, and the Duke Human Vaccine Institute, Duke University, Durham, North Carolina, United States of America
| | - George M. Shaw
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Beatrice H. Hahn
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Bette Korber
- Theoretical Biology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
- * E-mail:
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Maturation-induced cloaking of neutralization epitopes on HIV-1 particles. PLoS Pathog 2011; 7:e1002234. [PMID: 21931551 PMCID: PMC3169560 DOI: 10.1371/journal.ppat.1002234] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Accepted: 07/08/2011] [Indexed: 11/19/2022] Open
Abstract
To become infectious, HIV-1 particles undergo a maturation process involving proteolytic cleavage of the Gag and Gag-Pol polyproteins. Immature particles contain a highly stable spherical Gag lattice and are impaired for fusion with target cells. The fusion impairment is relieved by truncation of the gp41 cytoplasmic tail (CT), indicating that an interaction between the immature viral core and gp41 within the particle represses HIV-1 fusion by an unknown mechanism. We hypothesized that the conformation of Env on the viral surface is regulated allosterically by interactions with the HIV-1 core during particle maturation. To test this, we quantified the binding of a panel of monoclonal antibodies to mature and immature HIV-1 particles by immunofluorescence imaging. Surprisingly, immature particles exhibited markedly enhanced binding of several gp41-specific antibodies, including two that recognize the membrane proximal external region (MPER) and neutralize diverse HIV-1 strains. Several of the differences in epitope exposure on mature and immature particles were abolished by truncation of the gp41 CT, thus linking the immature HIV-1 fusion defect with altered Env conformation. Our results suggest that perturbation of fusion-dependent Env conformational changes contributes to the impaired fusion of immature particles. Masking of neutralization-sensitive epitopes during particle maturation may contribute to HIV-1 immune evasion and has practical implications for vaccine strategies targeting the gp41 MPER. The conformation of HIV-1 Env is of tremendous importance from an immunological standpoint. While several human monoclonal antibodies that exhibit broadly neutralizing activity have been identified, efforts to elicit such antibodies have met with minimal success. Here, we show that the conformation of Env is altered on the surface of immature vs. mature HIV-1 particles in such a way that certain epitopes recognized by some broadly neutralizing antibodies are more exposed on immature virions. This maturation-dependent conformational masking may represent an important mechanism of HIV-1 immune evasion.
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Yi Y, Noh MJ, Lee KH. Current advances in retroviral gene therapy. Curr Gene Ther 2011; 11:218-28. [PMID: 21453283 PMCID: PMC3182074 DOI: 10.2174/156652311795684740] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 03/15/2011] [Indexed: 12/25/2022]
Abstract
There have been major changes since the incidents of leukemia development in X-SCID patients after the treatments using retroviral gene therapy. Due to the risk of oncogenesis caused by retroviral insertional activation of host genes, most of the efforts focused on the lentiviral therapies. However, a relative clonal dominance was detected in a patient with β-thalassemia Major, two years after the subject received genetically modified hematopoietic stem cells using lentiviral vectors. This disappointing result of the recent clinical trial using lentiviral vector tells us that the current and most advanced vector systems does not have enough safety. In this review, various safety features that have been tried for the retroviral gene therapy are introduced and the possible new ways of improvements are discussed. Additional feature of chromatin insulators, co-transduction of a suicidal gene under the control of an inducible promoter, conditional expression of the transgene only in appropriate target cells, targeted transduction, cell type-specific expression, targeted local administration, splitting of the viral genome, and site specific insertion of retroviral vector are discussed here.
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Checkley MA, Luttge BG, Freed EO. HIV-1 envelope glycoprotein biosynthesis, trafficking, and incorporation. J Mol Biol 2011; 410:582-608. [PMID: 21762802 PMCID: PMC3139147 DOI: 10.1016/j.jmb.2011.04.042] [Citation(s) in RCA: 341] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 04/14/2011] [Accepted: 04/15/2011] [Indexed: 12/13/2022]
Abstract
The HIV-1 envelope (Env) glycoproteins play an essential role in the virus replication cycle by mediating the fusion between viral and cellular membranes during the entry process. The Env glycoproteins are synthesized as a polyprotein precursor (gp160) that is cleaved by cellular proteases to the mature surface glycoprotein gp120 and the transmembrane glycoprotein gp41. During virus assembly, the gp120/gp41 complex is incorporated as heterotrimeric spikes into the lipid bilayer of nascent virions. These gp120/gp41 complexes then initiate the infection process by binding receptor and coreceptor on the surface of target cells. Much is currently known about the HIV-1 Env glycoprotein trafficking pathway and the structure of gp120 and the extracellular domain of gp41. However, the mechanism by which the Env glycoprotein complex is incorporated into virus particles remains incompletely understood. Genetic data support a major role for the cytoplasmic tail of gp41 and the matrix domain of Gag in Env glycoprotein incorporation. Still to be defined are the identities of host cell factors that may promote Env incorporation and the role of specific membrane microdomains in this process. Here, we review our current understanding of HIV-1 Env glycoprotein trafficking and incorporation into virions.
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Affiliation(s)
- Mary Ann Checkley
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
| | - Benjamin G. Luttge
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
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Bhakta SJ, Shang L, Prince JL, Claiborne DT, Hunter E. Mutagenesis of tyrosine and di-leucine motifs in the HIV-1 envelope cytoplasmic domain results in a loss of Env-mediated fusion and infectivity. Retrovirology 2011; 8:37. [PMID: 21569545 PMCID: PMC3117779 DOI: 10.1186/1742-4690-8-37] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 05/14/2011] [Indexed: 12/30/2022] Open
Abstract
Background The gp41 component of the Human Immunodeficiency Virus (HIV) envelope glycoprotein (Env) contains a long cytoplasmic domain (CD) with multiple highly conserved tyrosine (Y) and dileucine (LL) motifs. Studies suggest that the motifs distal to major endocytosis motif (Y712HRL), located at residues 712-715 of Env, may contribute to Env functionality in the viral life cycle. In order to examine the biological contribution of these motifs in the biosynthesis, transport, and function of Env, we constructed two panels of mutants in which the conserved Y- and LL-motifs were sequentially substituted by alternative residues, either in the presence or absence of Y712. Additional mutants targeting individual motifs were then constructed. Results All mutant Envs, when expressed in the absence of other viral proteins, maintained at least WT levels of Env surface staining by multiple antibodies. The Y712 mutation (Y712C) contributed to at least a 4-fold increase in surface expression for all mutants containing this change. Sequential mutagenesis of the Y- and LL-motifs resulted in a generally progressive decrease in Env fusogenicity. However, additive mutation of dileucine and tyrosine motifs beyond the tyrosine at residue 768 resulted in the most dramatic effects on Env incorporation into virions, viral infectivity, and virus fusion with target cells. Conclusions From the studies reported here, we show that mutations of the Y- and LL-motifs, which effectively eliminate the amphipathic nature of the lytic peptide 2 (LLP2) domain or disrupt YW and LL motifs in a region spanning residues 795-803 (YWWNLLQYW), just C-terminal of LLP2, can dramatically interfere with biological functions of HIV-1 Env and abrogate virus replication. Because these mutant proteins are expressed at the cell surface, we conclude that tyrosine and di-leucine residues within the cytoplasmic domain of gp41 play critical roles in HIV-1 replication that are distinct from that of targeting the plasma membrane.
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Affiliation(s)
- Sushma J Bhakta
- Emory Vaccine Center at the Yerkes National Primate Research Center and Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30329, USA
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Shi W, Bohon J, Han DP, Habte H, Qin Y, Cho MW, Chance MR. Structural characterization of HIV gp41 with the membrane-proximal external region. J Biol Chem 2010; 285:24290-8. [PMID: 20525690 PMCID: PMC2911339 DOI: 10.1074/jbc.m110.111351] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 05/05/2010] [Indexed: 11/06/2022] Open
Abstract
Human immunodeficiency virus, type 1 (HIV-1) envelope glycoprotein (gp120/gp41) plays a critical role in virus infection and pathogenesis. Three of the six monoclonal antibodies considered to have broadly neutralizing activities (2F5, 4E10, and Z13e1) bind to the membrane-proximal external region (MPER) of gp41. This makes the MPER a desirable template for developing immunogens that can elicit antibodies with properties similar to these monoclonal antibodies, with a long term goal of developing antigens that could serve as novel HIV vaccines. In order to provide a structural basis for rational antigen design, an MPER construct, HR1-54Q, was generated for x-ray crystallographic and x-ray footprinting studies to provide both high resolution atomic coordinates and verification of the solution state of the antigen, respectively. The crystal structure of HR1-54Q reveals a trimeric, coiled-coil six-helical bundle, which probably represents a postfusion form of gp41. The MPER portion extends from HR2 in continuation of a slightly bent long helix and is relatively flexible. The structures observed for the 2F5 and 4E10 epitopes agree well with existing structural data, and enzyme-linked immunosorbent assays indicate that the antigen binds well to antibodies that recognize the above epitopes. Hydroxyl radical-mediated protein footprinting of the antigen in solution reveals specifically protected and accessible regions consistent with the predictions based on the trimeric structure from the crystallographic data. Overall, the HR1-54Q antigen, as characterized by crystallography and footprinting, represents a postfusion, trimeric form of HIV gp41, and its structure provides a rational basis for gp41 antigen design suitable for HIV vaccine development.
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Affiliation(s)
- Wuxian Shi
- Center for Synchrotron Biosciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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Opposing effects of a tyrosine-based sorting motif and a PDZ-binding motif regulate human T-lymphotropic virus type 1 envelope trafficking. J Virol 2010; 84:6995-7004. [PMID: 20463077 DOI: 10.1128/jvi.01853-09] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) envelope (Env) glycoprotein mediates binding of the virus to its receptor on the surface of target cells and subsequent fusion of virus and cell membranes. To better understand the mechanisms that control HTLV-1 Env trafficking and activity, we have examined two protein-protein interaction motifs in the cytoplasmic domain of Env. One is the sequence YSLI, which matches the consensus YXXPhi motifs that are known to interact with various adaptor protein complexes; the other is the sequence ESSL at the C terminus of Env, which matches the consensus PDZ-binding motif. We show here that mutations that destroy the YXXPhi motif increased Env expression on the cell surface and increased cell-cell fusion activity. In contrast, mutation of the PDZ-binding motif greatly diminished Env expression in cells, which could be restored to wild-type levels either by mutating the YXXPhi motif or by silencing AP2 and AP3, suggesting that interactions with PDZ proteins oppose an Env degradation pathway mediated by AP2 and AP3. Silencing of the PDZ protein hDlg1 did not affect Env expression, suggesting that hDlg1 is not a binding partner for Env. Substitution of the YSLI sequence in HTLV-1 Env with YXXPhi elements from other cell or virus membrane-spanning proteins resulted in alterations in Env accumulation in cells, incorporation into virions, and virion infectivity. Env variants containing YXXPhi motifs that are predicted to have high-affinity interaction with AP2 accumulated to lower steady-state levels. Interestingly, mutations that destroy the YXXPhi motif resulted in viruses that were not infectious by cell-free or cell-associated routes of infection. Unlike YXXPhi, the function of the PDZ-binding motif manifests itself only in the producer cells; AP2 silencing restored the incorporation of PDZ-deficient Env into virus-like particles (VLPs) and the infectivity of these VLPs to wild-type levels.
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Abstract
Tetraspanins are small integral membrane proteins that are known to control a variety of cellular processes, including signaling, migration and cell-cell fusion. Research over the past few years established that they are also regulators of various steps in the HIV-1 replication cycle, but the mechanisms through which these proteins either enhance or repress virus spread remain largely unknown.
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Affiliation(s)
- Markus Thali
- Department of Microbiology and Molecular Genetics, College of Medicine and CALS, University of Vermont, 318 Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0084, USA.
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Role of a putative gp41 dimerization domain in human immunodeficiency virus type 1 membrane fusion. J Virol 2010; 84:201-9. [PMID: 19846514 DOI: 10.1128/jvi.01558-09] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The entry of human immunodeficiency virus type 1 (HIV-1) into a target cell entails a series of conformational changes in the gp41 transmembrane glycoprotein that mediates the fusion of the viral and target cell membranes. A trimer-of-hairpins structure formed by the association of two heptad repeat (HR) regions of the gp41 ectodomain has been implicated in a late step of the fusion pathway. Earlier native and intermediate states of the protein are postulated to mediate the antiviral activity of the fusion inhibitor enfuvirtide and of broadly neutralizing monoclonal antibodies (NAbs), but the details of these structures remain unknown. Here, we report the identification and crystal structure of a dimerization domain in the C-terminal ectodomain of gp41 (residues 630 to 683, or C54). Two C54 monomers associate to form an asymmetric, antiparallel coiled coil with two distinct C-terminal alpha-helical overhangs. This dimer structure is conferred largely by interactions within a central core that corresponds to the sequence of enfuvirtide. The mutagenic alteration of the dimer interface severely impairs the infectivity of Env-pseudotyped viruses. Moreover, the C54 structure binds tightly to both the 2F5 and 4E10 NAbs and likely represents a potential intermediate conformation of gp41. These results should enhance our understanding of the molecular basis of the gp41 fusogenic structural transitions and thereby guide rational, structure-based efforts to design new fusion inhibitors and vaccine candidates intended to induce broadly neutralizing antibodies.
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Morozov V, Morozov A, Lagaye S. Short communication: Simultaneous substitutions of V38M and N43T-N44K in the gp41 heptad repeat 1 (HR1) disrupt HIV type 1 gPr160 endoproteolytic cleavage (*). AIDS Res Hum Retroviruses 2010; 26:73-7. [PMID: 20055586 DOI: 10.1089/aid.2009.0079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We cloned and sequenced gp41 HIV-1 from plasma of AIDS patients under HAART and T-20 (enfuvirtide, Fuzeon) therapy and revealed several T-20 resistance-associated mutations. Two mutations, a single V38A and a double N43T-N44K were the most frequent; however, they were not found together in one clone. We anticipated that simultaneous mutations of these three residues might play a vital role in the viral life cycle. To address this problem, we introduced N43T-N44K and V38M + N43T-N44K substitutions to a cloned gp41 and introduced modified gp41 into the pNL4-3 molecular clone. HEK293T cells were transfected with the obtained vectors and released viruses were examined for reverse transcriptase (RT) activity, infectivity on reporter TZM-bl cells, and in Western blotting. Nearly equal RT activity was demonstrated in viruses with and without mutations. However, viruses with the V38M + N43T-N44K mutations were not infectious and, as shown by Western blotting, gPr160 cleavage was impaired. These data suggest that V38M + N43T-N44K mutations perturbed the natural conformation of gPr160 in a way that access of furin to the cleavage site (REKR) was blocked. Therefore, the residues V38 + N43-N44 retain the gPr160 conformation in proximity to the furin cleavage site and, as a consequence, are critical for virus infectivity. These data may explain why viruses with V38M + N43T-N44K mutations were not previously detected in the plasma of T-20-experienced patients.
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Affiliation(s)
- V.A. Morozov
- Institute of Human Virology, School of Medicine, University of Maryland, Baltimore, Maryland 21201
- Robert Koch-Institute, 13353 Berlin, Germany
| | - A.V. Morozov
- Institute of Human Virology, School of Medicine, University of Maryland, Baltimore, Maryland 21201
- W.A. Engelhardt Institute of Molecular Biology RAS, Moscow, Russia
| | - S. Lagaye
- Institut Cochin, UMR 8104 CNRS, U567 INSERM, Université Paris Descartes, 75014 Paris, France
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Reconstitution of the ancestral glycoprotein of human endogenous retrovirus k and modulation of its functional activity by truncation of the cytoplasmic domain. J Virol 2009; 83:12790-800. [PMID: 19812154 DOI: 10.1128/jvi.01368-09] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Endogenous retroviruses present in the human genome provide a rich record of ancient infections. All presently recognized elements, including the youngest and most intact proviruses of the human endogenous retrovirus K(HML-2) [HERV-K(HML-2)] family, have suffered postinsertional mutations during their time of chromosomal residence, and genes encoding the envelope glycoprotein (Env) have not been spared these mutations. In this study, we have, for the first time, reconstituted an authentic Env of a HERV-K(HML-2) provirus by back mutation of putative postinsertional amino acid changes of the protein encoded by HERV-K113. Aided by codon-optimized expression, we demonstrate that the reconstituted Env regained its ability to be incorporated into retroviral particles and to mediate entry. The original ancient HERV-K113 Env was synthesized as a moderately glycosylated gp95 precursor protein cleaved into surface and transmembrane (TM) subunits. Of the nine N-linked oligosaccharides, four are part of the TM subunit, contributing 15 kDa to its apparent molecular mass of 41 kDa. The carbohydrates, as well as the cytoplasmic tail, are critical for efficient intracellular trafficking, processing, stability, and particle incorporation. Whereas deletions of the carboxy-terminal 6 residues completely abrogated cleavage and virion association, more extensive truncations slightly enhanced incorporation but dramatically increased the ability to mediate entry of pseudotyped lentiviruses. Although the first HERV-K(HML-2) elements infected human ancestors about 30 million years ago, our findings indicate that their glycoproteins are in most respects remarkably similar to those of classical contemporary retroviruses and can still mediate efficient entry into mammalian cells.
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Matrix and envelope coevolution revealed in a patient monitored since primary infection with human immunodeficiency virus type 1. J Virol 2009; 83:9875-89. [PMID: 19625403 DOI: 10.1128/jvi.01213-09] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Lentiviruses, including human immunodeficiency virus type 1 (HIV-1), typically encode envelope glycoproteins (Env) with long cytoplasmic tails (CTs). The strong conservation of CT length in primary isolates of HIV-1 suggests that this factor plays a key role in viral replication and persistence in infected patients. However, we report here the emergence and dominance of a primary HIV-1 variant carrying a natural 20-amino-acid truncation of the CT in vivo. We demonstrated that this truncation was deleterious for viral replication in cell culture. We then identified a compensatory amino acid substitution in the matrix protein that reversed the negative effects of CT truncation. The loss or rescue of infectivity depended on the level of Env incorporation into virus particles. Interestingly, we found that a virus mutant with defective Env incorporation was able to spread by cell-to-cell transfer. The effects on viral infectivity of compensation between the CT and the matrix protein have been suggested by in vitro studies based on T-cell laboratory-adapted virus mutants, but we provide here the first demonstration of the natural occurrence of similar mechanisms in an infected patient. Our findings provide insight into the potential of HIV-1 to evolve in vivo and its ability to overcome major structural alterations.
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32
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Expression of Ebolavirus glycoprotein on the target cells enhances viral entry. Virol J 2009; 6:75. [PMID: 19505320 PMCID: PMC2699336 DOI: 10.1186/1743-422x-6-75] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 06/08/2009] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Entry of Ebolavirus to the target cells is mediated by the viral glycoprotein GP. The native GP exists as a homotrimer on the virions and contains two subunits, a surface subunit (GP1) that is involved in receptor binding and a transmembrane subunit (GP2) that mediates the virus-host membrane fusion. Previously we showed that over-expression of GP on the target cells blocks GP-mediated viral entry, which is mostly likely due to receptor interference by GP1. RESULTS In this study, using a tetracycline inducible system, we report that low levels of GP expression on the target cells, instead of interfering, specifically enhance GP mediated viral entry. Detailed mapping analysis strongly suggests that the fusion subunit GP2 is primarily responsible for this novel phenomenon, here referred to as trans enhancement. CONCLUSION Our data suggests that GP2 mediated trans enhancement of virus fusion occurs via a mechanism analogous to eukaryotic membrane fusion processes involving specific trans oligomerization and cooperative interaction of fusion mediators. These findings have important implications in our current understanding of virus entry and superinfection interference.
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Identification of a critical motif for the human immunodeficiency virus type 1 (HIV-1) gp41 core structure: implications for designing novel anti-HIV fusion inhibitors. J Virol 2008; 82:6349-58. [PMID: 18417584 DOI: 10.1128/jvi.00319-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) entry into the host cell involves a cascade of events and currently represents one of most attractive targets in the search for new antiviral drugs. The fusion-active gp41 core structure is a stable six-helix bundle (6-HB) folded by its trimeric N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR). Peptides derived from the CHR region of HIV-1 gp41 are potent fusion inhibitors that target the NHR to block viral and cellular membrane fusion in a dominant negative fashion. However, all CHR peptides reported to date are derived primarily from residues 628 to 673 of gp41; little attention has been paid to the upstream sequence of the pocket binding domain (PBD) in the CHR. Here, we have identified a motif ((621)QIWNNMT(627)) located at the upstream region of the gp41 CHR, immediately adjacent to the PBD ((628)WMEWEREI(635)). Biophysical characterization demonstrated that this motif is critical for the stabilization of the gp41 6-HB core. The peptide CP621-652, containing the (621)QIWNNMT(627) motif, was able to interact with T21, a counterpart peptide derived from the NHR, to form a typical 6-HB structure with a high thermostability (thermal unfolding transition [T(m)] value of 82 degrees C). In contrast, the 6-HB formed by the peptides N36 and C34, which has been considered to be a core structure of the fusion-active gp41, had a T(m) of 64 degrees C. Different from T-20 (brand name Fuseon), which is the first and only HIV-1 fusion inhibitor approved for clinical use, CP621-652 could efficiently block 6-HB formation in a dose-dependent manner. Significantly, CP621-652 had potent inhibitory activity against HIV-1-mediated cell-cell fusion and infection, especially against T-20- and C34-resistant virus. Therefore, our works provide important information for understanding the core structure of the fusion-active gp41 and for designing novel anti-HIV peptides.
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Lu L, Zhu Y, Huang J, Chen X, Yang H, Jiang S, Chen YH. Surface exposure of the HIV-1 env cytoplasmic tail LLP2 domain during the membrane fusion process: interaction with gp41 fusion core. J Biol Chem 2008; 283:16723-31. [PMID: 18408000 DOI: 10.1074/jbc.m801083200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HIV-1 gp41 cytoplasmic tail (CT) is highly conserved among HIV-1 isolates, particularly the region designated lentivirus lytic peptide (LLP1-2), which includes two alpha-helical domains LLP1 and LLP2. Although the gp41 CT is recognized as a modulator of viral fusogenicity, little is known about the regulatory mechanism of this region in the viral fusion process. Here we report that anti-LLP1-2 and anti-LLP2 antibodies (IgG) inhibited HIV-1 Env-mediated cell fusion and bound to the interface between effector and target cells at a suboptimal temperature (31.5 degrees C), which slows down the fusion process and prolongs the fusion intermediate state. This suggests that LLP1-2, especially the LLP2 region located inside the viral membrane, is transiently exposed on the membrane surface during the fusion process. Synthetic LLP2 peptide could bind to the gp41 six-helix bundle core with high binding affinity. These results suggest that the gp41 CT may interact with the gp41 core, via the surface-exposed LLP2 domain, to regulate Env-mediated membrane fusion.
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Affiliation(s)
- Lu Lu
- Laboratory of Immunology, Department of Biology, Tsinghua University, Beijing Key Laboratory for Protein Therapeutics, Beijing 100084, China
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Valas S, Rolland M, Perrin C, Perrin G, Mamoun RZ. Characterization of a new 5' splice site within the caprine arthritis encephalitis virus genome: evidence for a novel auxiliary protein. Retrovirology 2008; 5:22. [PMID: 18312636 PMCID: PMC2291067 DOI: 10.1186/1742-4690-5-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 02/29/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Lentiviral genomes encode multiple structural and regulatory proteins. Expression of the full complement of viral proteins is accomplished in part by alternative splicing of the genomic RNA. Caprine arthritis encephalitis virus (CAEV) and maedi-visna virus (MVV) are two highly related small-ruminant lentiviruses (SRLVs) that infect goats and sheep. Their genome seems to be less complex than those of primate lentiviruses since SRLVs encode only three auxiliary proteins, namely, Tat, Rev, and Vif, in addition to the products of gag, pol, and env genes common to all retroviruses. Here, we investigated the central part of the SRLV genome to identify new splice elements and their relevance in viral mRNA and protein expression. RESULTS We demonstrated the existence of a new 5' splice (SD) site located within the central part of CAEV genome, 17 nucleotides downstream from the SD site used for the rev mRNA synthesis, and perfectly conserved among SRLV strains. This new SD site was found to be functional in both transfected and infected cells, leading to the production of a transcript containing an open reading frame generated by the splice junction with the 3' splice site used for the rev mRNA synthesis. This open reading frame encodes two major protein isoforms of 18- and 17-kDa, named Rtm, in which the N-terminal domain shared by the Env precursor and Rev proteins is fused to the entire cytoplasmic tail of the transmembrane glycoprotein. Immunoprecipitations using monospecific antibodies provided evidence for the expression of the Rtm isoforms in infected cells. The Rtm protein interacts specifically with the cytoplasmic domain of the transmembrane glycoprotein in vitro, and its expression impairs the fusion activity of the Env protein. CONCLUSION The characterization of a novel CAEV protein, named Rtm, which is produced by an additional multiply-spliced mRNA, indicated that the splicing pattern of CAEV genome is more complex than previously reported, generating greater protein diversity. The high conservation of the SD site used for the rtm mRNA synthesis among CAEV and MVV strains strongly suggests that the Rtm protein plays a role in SRLV propagation in vivo, likely by competing with Env protein functions.
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Affiliation(s)
- Stephen Valas
- AFSSA-Niort, Laboratoire d'Etudes et de Recherches Caprines, 79012 Niort, France.
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36
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Enhanced cell surface expression, immunogenicity and genetic stability resulting from a spontaneous truncation of HIV Env expressed by a recombinant MVA. Virology 2007; 372:260-72. [PMID: 18048074 DOI: 10.1016/j.virol.2007.10.033] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 06/28/2007] [Accepted: 10/26/2007] [Indexed: 11/20/2022]
Abstract
During propagation of modified vaccinia virus Ankara (MVA) encoding HIV 89.6 Env, a few viral foci stained very prominently. Virus cloned from such foci replicated to higher titers than the parent and displayed enhanced genetic stability on passage. Sequence analysis showed a single nucleotide deletion in the 89.6 env gene of the mutant that caused a frame shift and truncation of 115 amino acids from the cytoplasmic domain. The truncated Env was more highly expressed on the cell surface, induced higher antibody responses than the full-length Env, reacted with HIV neutralizing monoclonal antibodies and mediated CD4/co-receptor-dependent fusion. Intramuscular (i.m.), intradermal (i.d.) needleless, and intrarectal (i.r.) catheter inoculations gave comparable serum IgG responses. However, intraoral (i.o.) needleless injector route gave the highest IgA in lung washings and i.r. gave the highest IgA and IgG responses in fecal extracts. Induction of CTL responses in the spleens of individual mice as assayed by intracellular cytokine staining was similar with both the full-length and truncated Env constructs. Induction of acute and memory CTL in the spleens of mice immunized with the truncated Env construct by i.d., i.o., and i.r. routes was comparable and higher than by the i.m. route, but only the i.r. route induced CTL in the gut-associated lymphoid tissue. Thus, truncation of Env enhanced genetic stability as well as serum and mucosal antibody responses, suggesting the desirability of a similar modification in MVA-based candidate HIV vaccines.
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Jiang J, Aiken C. Maturation-dependent human immunodeficiency virus type 1 particle fusion requires a carboxyl-terminal region of the gp41 cytoplasmic tail. J Virol 2007; 81:9999-10008. [PMID: 17609279 PMCID: PMC2045384 DOI: 10.1128/jvi.00592-07] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Lentiviruses, including human immunodeficiency virus type 1 (HIV-1), typically encode fusion glycoproteins with long cytoplasmic tails (CTs). We previously reported that immature HIV-1 particles are inhibited for fusion with target cells by a mechanism requiring the 152-amino-acid CT of gp41. The gp41 CT was also shown to mediate the detergent-resistant association of the HIV-1 envelope glycoprotein complex with immature HIV-1 particles, indicating that the gp41 CT forms a stable complex with Gag in immature virions. In the present study, we analyzed the effects of progressive truncations and point mutations in the gp41 CT on the fusion of mature and immature HIV-1 particles with target cells. We also determined the effects of these mutations on the detergent-resistant association of gp41 with immature HIV-1 particles. Removal of the C-terminal 28 amino acids relieved the dependence of HIV-1 fusion on maturation. However, a mutant Env protein lacking this region remained associated with immature HIV-1 particles treated with nonionic detergent. Further mutational analysis of the C-terminal region of gp41 revealed two specific sequences required for maturation-dependent HIV-1 fusion. Collectively, our results demonstrate that the extreme C terminus of gp41 plays a key role in coupling HIV-1 fusion competence to virion maturation. They further indicate that the stable association of gp41 with Gag in immature virions is not sufficient for inhibition of immature HIV-1 particle fusion.
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Affiliation(s)
- Jiyang Jiang
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, A-5301 Medical Center North, Nashville, TN 37232-2363, USA
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Newman JT, Sturgeon TJ, Gupta P, Montelaro RC. Differential functional phenotypes of two primary HIV-1 strains resulting from homologous point mutations in the LLP domains of the envelope gp41 intracytoplasmic domain. Virology 2007; 367:102-16. [PMID: 17582453 PMCID: PMC2034414 DOI: 10.1016/j.virol.2007.05.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 04/09/2007] [Accepted: 05/21/2007] [Indexed: 01/10/2023]
Abstract
We previously reported that selected mutations of highly conserved arginine residues within the LLP regions of HIV-1(ME46) gp41 had diverse effects on Env function. In the current study, we sought to test if the observed LLP mutant phenotypes would be similar in HIV-1(89.6). The results of the current studies revealed that the LLP-1 mutations conferred reduced Env incorporation, infectivity, and replication phenotypes in both viruses, while homologous LLP-2 mutations had differential phenotypical effects between the two strains. In particular, several of the 89.6 LLP-2 mutant viruses were replication defective in CEMX174 cells despite having increased levels of Env incorporation, and with both strains, there were differential effects on infectivity. This comparison of homologous point mutations in two different strains of HIV supports the role of LLPs as determinants of Env function, but reveals for the first time the influence of virus strain on LLP mutant phenotypes.
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Affiliation(s)
- Jason T Newman
- Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, PA 15261, USA
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Prabakaran P, Dimitrov AS, Fouts TR, Dimitrov DS. Structure and function of the HIV envelope glycoprotein as entry mediator, vaccine immunogen, and target for inhibitors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2007; 55:33-97. [PMID: 17586312 PMCID: PMC7111665 DOI: 10.1016/s1054-3589(07)55002-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This chapter discusses the advances of the envelope glycoprotein (Env) structure as related to the interactions of conserved Env structures with receptor molecules and antibodies with implications for the design of vaccine immunogens and inhibitors. The human immunodeficiency virus (HIV) Env binds to cell surface–associated receptor (CD4) and coreceptor (CCR5 or CXCR4) by one of its two non-covalently associated subunits, gp120. The induced conformational changes activate the other subunit (gp41), which causes the fusion of the viral with the plasma cell membranes resulting in the delivery of the viral genome into the cell and the initiation of the infection cycle. As the only HIV protein exposed to the environment, the Env is also a major immunogen to which neutralizing antibodies are directed and a target that is relatively easy to access by inhibitors. A fundamental problem in the development of effective vaccines and inhibitors against HIV is the rapid generation of alterations at high levels of expression during long chronic infection and the resulting significant heterogeneity of the Env. The preservation of the Env function as an entry mediator and limitations on size and expression impose restrictions on its variability and lead to the existence of conserved structures.
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Affiliation(s)
- Ponraj Prabakaran
- Protein Interactions Group, CCRNP, CCR, NCI-Frederick, NIH Frederick, MD 21702, USA
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40
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Dey AK, David KB, Klasse PJ, Moore JP. Specific amino acids in the N-terminus of the gp41 ectodomain contribute to the stabilization of a soluble, cleaved gp140 envelope glycoprotein from human immunodeficiency virus type 1. Virology 2006; 360:199-208. [PMID: 17092531 PMCID: PMC1857345 DOI: 10.1016/j.virol.2006.09.046] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 09/15/2006] [Accepted: 09/29/2006] [Indexed: 12/30/2022]
Abstract
The HIV-1 envelope glycoprotein is expressed on the viral membrane as a trimeric complex, formed by three gp120 surface glycoproteins non-covalently associated with three membrane-anchored gp41 subunits. The labile nature of the association between gp120 and gp41 hinders the expression of soluble, fully cleaved, trimeric gp140 proteins for structural and immunization studies. Disruption of the primary cleavage site within gp160 allows the production of stable gp140 trimers, but cleavage-defective trimers are antigenically dissimilar from their cleaved counterparts. Soluble, stabilized, proteolytically cleaved, trimeric gp140 proteins can be generated by engineering an intermolecular disulfide bond between gp120 and gp41 (SOS), combined with a single residue change, I559P, within gp41 (SOSIP). We have found that SOSIP gp140 proteins based on the subtype A HIV-1 strain KNH1144 form particularly homogenous trimers compared to a prototypic strain (JR-FL, subtype B). We now show that the determinants of this enhanced stability are located in the N-terminal region of KNH11144 gp41 and that, when substituted into heterologous Env sequences (e.g., JR-FL and Ba-L) they have a similarly beneficial effect on trimer stability. The stabilized trimers retain the epitopes for several neutralizing antibodies (b12, 2G12, 2F5 and 4E10) and the CD4-IgG2 molecule, suggesting that the overall antigenic structure of the gp140 protein has not been adversely impaired by the trimer-stabilizing substitutions. The ability to increase the stability of gp140 trimers might be useful for neutralizing antibody-based vaccine strategies based on the use of this type of immunogen.
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Affiliation(s)
| | | | | | - John P. Moore
- *Corresponding author. Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, Room W-805, New York, NY 10021. Phone (212) 746 4463; Fax. (212) 746 8340;
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41
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Lambelé M, Labrosse B, Roch E, Moreau A, Verrier B, Barin F, Roingeard P, Mammano F, Brand D. Impact of natural polymorphism within the gp41 cytoplasmic tail of human immunodeficiency virus type 1 on the intracellular distribution of envelope glycoproteins and viral assembly. J Virol 2006; 81:125-40. [PMID: 17050592 PMCID: PMC1797254 DOI: 10.1128/jvi.01659-06] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The motifs involved in the various functions of the human immunodeficiency virus type 1 (HIV-1) gp41 cytoplasmic tail (CT), particularly those related to the intracellular trafficking and assembly of envelope glycoproteins (Env) onto core particles, have generally been assessed with a restricted panel of T-cell laboratory-adapted virus strains. Here, we investigated gp41 CT sequences derived from individuals infected with HIV-1 viruses of various subtypes. We identified four patients harboring HIV variants with a natural polymorphism in the membrane-proximal tyrosine-based signal Y(712)SPL or the Y(802)W(803) diaromatic motif, which are two major determinants of Env intracellular trafficking. Confocal microscopy showed that the intracellular distribution of Env with a mutation in the tyrosine or diaromatic motif differed from that of Env with no mutation in these motifs. Surprisingly, the gp41 CTs of the primary viruses also had differential effects on the intracellular distribution of Env, independently of mutations in the tyrosine or diaromatic motifs, suggesting the involvement of additional determinants. Furthermore, analyses of virus replication kinetics indicated that the effects of mutations in the tyrosine or diaromatic motifs on viral replication depended on the gp41 CT context. These effects were at least partly due to differences in the efficiency of Env incorporation into virions. Thus, polymorphisms in primary HIV-1 gp41 CTs at the quasispecies or subtype level can influence the intracellular distribution of Env, its incorporation into virions, and viral replication capacity.
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Blot G, Lopez-Vergès S, Treand C, Kubat NJ, Delcroix-Genête D, Emiliani S, Benarous R, Berlioz-Torrent C. Luman, a new partner of HIV-1 TMgp41, interferes with Tat-mediated transcription of the HIV-1 LTR. J Mol Biol 2006; 364:1034-47. [PMID: 17054986 DOI: 10.1016/j.jmb.2006.09.080] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 09/25/2006] [Accepted: 09/27/2006] [Indexed: 11/18/2022]
Abstract
In our search for new partners of the HIV-1 envelope glycoprotein (Env), we found that the cytoplasmic domain of the TMgp41 (TMgp41 CD) subunit of HIV-1 Env interacted with Luman, a transcription factor of the CREB/ATF family. Luman is anchored in the endoplasmic reticulum membrane and subjected to activation by regulated intramembrane proteolysis (RIP). The RIP process permits the release of the activated amino-terminal fragment of Luman into the cytoplasm, and its import into the nucleus. Here, we demonstrate that interaction between the TMgp41 CD and Luman requires a region encompassing the b-Zip and TM domains of Luman and decreases the stability of this factor. Moreover, we found that overexpression of a constitutively active form of Luman in cells transfected with HXB2R HIV-1 provirus decreased the intracellular expression of Gag and Env and led to a decrease in virion release. This negative effect of activated Luman on HIV-1 production was correlated to the inhibition of Tat transactivation of the HIV-1 LTR, which might be related to an interaction of activated Luman with Tat. Altogether, these results show that Luman acts as a partner of two major HIV-1 proteins: the TMgp41 Env subunit and Tat. The interaction between the TMgp41 subunit of Env and Luman affects the stability of the full-length Luman protein, the precursor of the activated, nuclear form of Luman, which acts negatively on Tat-mediated HIV-1 transactivation.
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Affiliation(s)
- Guillaume Blot
- Institut Cochin, Département Maladies Infectieuses, Paris F-75014, France
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43
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Lopez-Vergès S, Camus G, Blot G, Beauvoir R, Benarous R, Berlioz-Torrent C. Tail-interacting protein TIP47 is a connector between Gag and Env and is required for Env incorporation into HIV-1 virions. Proc Natl Acad Sci U S A 2006; 103:14947-52. [PMID: 17003132 PMCID: PMC1595456 DOI: 10.1073/pnas.0602941103] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The presence of the envelope glycoprotein Env in HIV-1 virions is essential for infectivity. To date, the molecular mechanism by which Env is packaged into virions has been largely unknown. Here, we show that TIP47 (tail-interacting protein of 47 kDa), which has been shown to interact with Env, also binds the MA (matrix) domain of HIV-1 Gag protein and that these three proteins form a ternary complex. Mutations in Gag that abrogate interaction with TIP47 inhibit Env incorporation and virion infectivity as well as colocalization between Gag and Env. We also show that TIP47 silencing impairs Env incorporation and infectivity and abolishes coimmunoprecipitation of Gag with Env. In contrast, overexpression of TIP47 increases Env packaging. Last, we demonstrate that TIP47 can interact simultaneously with Env and Gag. Taken together, our results show that TIP47 is a cellular cofactor that plays an essential role in Env incorporation, allowing the encounter and the physical association between HIV-1 Gag and Env proteins during the viral assembly process.
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Affiliation(s)
- Sandra Lopez-Vergès
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
| | - Grégory Camus
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
| | - Guillaume Blot
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
| | - Roxane Beauvoir
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
| | - Richard Benarous
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
- *To whom correspondence may be addressed at:
Institut Cochin, 27 Rue du Faubourg Saint Jacques, F-75014 Paris, France. E-mail:
or
| | - Clarisse Berlioz-Torrent
- Institut Cochin, Département Maladies Infectieuses, F-75014 Paris, France; Institut National de la Santé et de la Recherche Médicale, U567, F-75014 Paris, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, F-75014 Paris, France; and Faculté de Médecine René Descartes, Université Paris 5, Unité Mixte de Recherche 3, F-75014 Paris, France
- *To whom correspondence may be addressed at:
Institut Cochin, 27 Rue du Faubourg Saint Jacques, F-75014 Paris, France. E-mail:
or
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44
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Blot V, Lopez-Vergès S, Breton M, Pique C, Berlioz-Torrent C, Grange MP. The conserved dileucine- and tyrosine-based motifs in MLV and MPMV envelope glycoproteins are both important to regulate a common Env intracellular trafficking. Retrovirology 2006; 3:62. [PMID: 16978406 PMCID: PMC1592117 DOI: 10.1186/1742-4690-3-62] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 09/15/2006] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Retrovirus particles emerge from the assembly of two structural protein components, Gag that is translated as a soluble protein in the cytoplasm of the host cells, and Env, a type I transmembrane protein. Because both components are translated in different intracellular compartments, elucidating the mechanisms of retrovirus assembly thus requires the study of their intracellular trafficking. RESULTS We used a CD25 (Tac) chimera-based approach to study the trafficking of Moloney murine leukemia virus and Mason-Pfizer monkey virus Env proteins. We found that the cytoplasmic tails (CTs) of both Env conserved two major signals that control a complex intracellular trafficking. A dileucine-based motif controls the sorting of the chimeras from the trans-Golgi network (TGN) toward endosomal compartments. Env proteins then follow a retrograde transport to the TGN due to the action of a tyrosine-based motif. Mutation of either motif induces the mis-localization of the chimeric proteins and both motifs are found to mediate interactions of the viral CTs with clathrin adaptors. CONCLUSION This data reveals the unexpected complexity of the intracellular trafficking of retrovirus Env proteins that cycle between the TGN and endosomes. Given that Gag proteins hijack endosomal host proteins, our work suggests that the endosomal pathway may be used by retroviruses to ensure proper encountering of viral structural Gag and Env proteins in cells, an essential step of virus assembly.
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Affiliation(s)
- Vincent Blot
- Institut Cochin, DépartementBiologie Cellulaire, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
- Weill Medical College of Cornell, Biochemistry Dept, New York, NY10021 USA
| | - Sandra Lopez-Vergès
- Institut Cochin, DépartementMaladies Infectieuses, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
| | - Marie Breton
- Institut Cochin, DépartementBiologie Cellulaire, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
| | - Claudine Pique
- Institut Cochin, DépartementBiologie Cellulaire, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
| | - Clarisse Berlioz-Torrent
- Institut Cochin, DépartementMaladies Infectieuses, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
| | - Marie-Pierre Grange
- Institut Cochin, DépartementBiologie Cellulaire, Paris, F-75014 France
- Inserm, U567, Paris, F-75014 France
- CNRS, UMR 8104, Paris, F-75014 France
- Université Paris 5, Faculté de Médecine René Descartes, UMR3, Paris, F-75014 France
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45
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Song C, Micoli K, Bauerova H, Pichova I, Hunter E. Amino acid residues in the cytoplasmic domain of the Mason-Pfizer monkey virus glycoprotein critical for its incorporation into virions. J Virol 2005; 79:11559-68. [PMID: 16140733 PMCID: PMC1212598 DOI: 10.1128/jvi.79.18.11559-11568.2005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Assembly of an infectious retrovirus requires the incorporation of the envelope glycoprotein complex during the process of particle budding. We have recently demonstrated that amino acid substitutions of a tyrosine residue in the cytoplasmic domain block glycoprotein incorporation into budding Mason-Pfizer monkey virus (M-PMV) particles and abrogate infectivity (C. Song, S. R. Dubay, and E. Hunter, J. Virol. 77:5192-5200, 2003). To investigate the contribution of other amino acids in the cytoplasmic domain to the process of glycoprotein incorporation, we introduced alanine-scanning mutations into this region of the transmembrane protein. The effects of the mutations on glycoprotein biosynthesis and function, as well as on virus infectivity, have been examined. Mutation of two cytoplasmic residues, valine 20 and histidine 21, inhibits viral protease-mediated cleavage of the cytoplasmic domain that is observed during virion maturation, but the mutant virions show only moderately reduced infectivity. We also demonstrate that the cytoplasmic domain of the M-PMV contains three amino acid residues that are absolutely essential for incorporation of glycoprotein into virions. In addition to the previously identified tyrosine at residue 22, an isoleucine at position 18 and a leucine at position 25 each mediate the process of incorporation and efficient release of virions. While isoleucine 18 may be involved in direct interactions with immature capsids, antibody uptake studies showed that leucine 25 and tyrosine 22 are part of an efficient internalization signal in the cytoplasmic domain of the M-PMV glycoprotein. These results demonstrate that the cytoplasmic domain of M-PMV Env, in part through its YXXL-mediated endocytosis and intracellular trafficking signals, plays a critical role in the incorporation of glycoprotein into virions.
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Affiliation(s)
- Chisu Song
- Department of Microbiology, University of Alabama at Birmingham, 35294, USA
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46
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Song C, Micoli K, Hunter E. Activity of the Mason-Pfizer monkey virus fusion protein is modulated by single amino acids in the cytoplasmic tail. J Virol 2005; 79:11569-79. [PMID: 16140734 PMCID: PMC1212599 DOI: 10.1128/jvi.79.18.11569-11579.2005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mason-Pfizer monkey virus (M-PMV) encodes a transmembrane glycoprotein with a 38-amino-acid-long cytoplasmic tail. After the release of the immature virus, a viral protease-mediated cleavage of the cytoplasmic tail (CT) results in the loss of 17 amino acids from the carboxy terminus and renders the envelope protein fusion competent. To investigate the role of individual amino acid residues in the CT in fusion, a series of mutations was introduced, and the effects of these mutations on glycoprotein biosynthesis and fusion were examined. Most of the alanine-scanning mutations in the CT had little effect on fusion activity. However, four amino acid substitutions (threonine 4, lysine 7, glutamine 9, and isoleucine 10) resulted in substantially increased fusogenicity, while six (leucine 2, phenylalanine 5, isoleucine 13, lysine 16, proline 17, and glycine 31) resulted in much-reduced fusion. Interestingly, the bulk of these mutations are located upstream of the CT cleavage site in a region that has the potential to form a coiled-coil in the Env trimer. Substitutions at glutamine 9 and isoleucine 10 with alanine had the most dramatic positive effect and resulted in the formation of large syncytia. Taken together, these data demonstrate that individual residues within the cytoplasmic domain of M-PMV Env can modulate, in both a positive and negative manner, biological functions that are associated with the extracellular domains of the glycoprotein complex.
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Affiliation(s)
- Chisu Song
- Department of Microbiology, University of Alabama at Birmingham, 35294, USA
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47
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Kalia V, Sarkar S, Gupta P, Montelaro RC. Antibody neutralization escape mediated by point mutations in the intracytoplasmic tail of human immunodeficiency virus type 1 gp41. J Virol 2005; 79:2097-107. [PMID: 15681412 PMCID: PMC546547 DOI: 10.1128/jvi.79.4.2097-2107.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The persistence of human immunodeficiency virus type 1 (HIV-1) infection in the presence of robust host immunity has been associated in part with variation in viral envelope proteins leading to antigenic variation and escape from neutralizing antibodies. Previous studies of natural neutralization escape mutants have predominantly focused on gp120 and gp41 ectodomain sequence variations that alter antibody binding via changes in conformation or glycosylation pattern of the Env, likely due to the immune pressure exerted on the exposed ectodomain component of the glycoprotein. Here, we show for the first time a novel mechanism by which point mutations in the intracytoplasmic tail of the transmembrane component (gp41) of envelope can render the virus resistant to neutralization by monoclonal antibodies and broadly neutralizing polyclonal serum antibodies. Point mutations in a highly conserved structural motif within the intracytoplasmic tail resulted in decreased binding of neutralizing antibodies to the Env ectodomain, evidently due to allosteric changes both in the gp41 ectodomain and in gp120. While receptor binding and infectivity of the mutant virus remained unaltered, the changes in Env antigenicity were associated with an increase in neutralization resistance of the mutant virus. These studies demonstrate the structurally integrated nature of gp120 and gp41 and underscore a previously unrecognized potentially critical role for even minor sequence variation of the intracytoplasmic tail in modulating the antigenicity of the ectodomain of HIV-1 envelope glycoprotein complex.
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Affiliation(s)
- Vandana Kalia
- University of Pittsburgh, Department of Molecular Genetics and Biochemistry, School of Medicine, W1144 BST, Pittsburgh, PA 15261, USA
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48
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Cheng SF, Wu CW, Kantchev EAB, Chang DK. Structure and membrane interaction of the internal fusion peptide of avian sarcoma leukosis virus. ACTA ACUST UNITED AC 2005; 271:4725-36. [PMID: 15606759 DOI: 10.1111/j.1432-1033.2004.04436.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structure and membrane interaction of the internal fusion peptide (IFP) fragment of the avian sarcoma and leucosis virus (ASLV) envelope glycoprotein was studied by an array of biophysical methods. The peptide was found to induce lipid mixing of vesicles more strongly than the fusion peptide derived from the N-terminal fusion peptide of influenza virus (HA2-FP). It was observed that the helical structure was enhanced in association with the model membranes, particularly in the N-terminal portion of the peptide. According to the infrared study, the peptide inserted into the membrane in an oblique orientation, but less deeply than the influenza HA2-FP. Analysis of NMR data in sodium dodecyl sulfate micelle suspension revealed that Pro13 of the peptide was located near the micelle-water interface. A type II beta-turn was deduced from NMR data for the peptide in aqueous medium, demonstrating a conformational flexibility of the IFP in analogy to the N-terminal FP such as that of gp41. A loose and multimodal self-assembly was deduced from the rhodamine fluorescence self-quenching experiments for the peptide bound to the membrane bilayer. Oligomerization of the peptide and its variants can also be observed in the electrophoretic experiments, suggesting a property in common with other N-terminal FP of class I fusion proteins.
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Affiliation(s)
- Shu-Fang Cheng
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, Republic of China
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49
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Cheynet V, Ruggieri A, Oriol G, Blond JL, Boson B, Vachot L, Verrier B, Cosset FL, Mallet F. Synthesis, assembly, and processing of the Env ERVWE1/syncytin human endogenous retroviral envelope. J Virol 2005; 79:5585-93. [PMID: 15827173 PMCID: PMC1082723 DOI: 10.1128/jvi.79.9.5585-5593.2005] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Syncytin is a fusogenic protein involved in the formation of the placental syncytiotrophoblast layer. This protein is encoded by the envelope gene of the ERVWE1 proviral locus belonging to the human endogenous retrovirus W (HERV-W) family. The HERV-W infectious ancestor entered the primate lineage 25 to 40 million years ago. Although the syncytin fusion property has been clearly demonstrated, little is known about this cellular protein maturation process with respect to classical infectious retrovirus envelope proteins. Here we show that the cellular syncytin protein is synthesized as a glycosylated gPr73 precursor cleaved into two mature proteins, a gp50 surface subunit (SU) and a gp24 transmembrane subunit (TM). These SU and TM subunits are found associated as homotrimers. The intracytoplasmic tail is critical to the fusogenic phenotype, although its cleavage requirements seem to have diverged from those of classical retroviral maturation.
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Affiliation(s)
- V Cheynet
- Laboratoire de Vectorologie Rétrovirale et Thérapie Génique, INSERM U412, Ecole Normale Supérieure de Lyon, 69364 Lyon, France
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50
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Ye L, Bu Z, Vzorov A, Taylor D, Compans RW, Yang C. Surface stability and immunogenicity of the human immunodeficiency virus envelope glycoprotein: role of the cytoplasmic domain. J Virol 2004; 78:13409-19. [PMID: 15564451 PMCID: PMC533911 DOI: 10.1128/jvi.78.24.13409-13419.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of two functional domains, the membrane-proximal YXXPhi motif and the membrane-distal inhibitory sequence in the long cytoplasmic tail of the human immunodeficiency virus type 1 (HIV-1) envelope protein (Env), on immunogenicity of the envelope protein were investigated. Genes with codons optimized for mammalian expression were synthesized for the HIV 89.6 Env and a truncated Env with 50 amino acids in the cytoplasmic domain to delete the membrane distal inhibitory sequence for surface expression. Additional genes were generated in which the tyrosine residue in the YXXPhi motif was changed into a serine. Pulse-chase radioactive labeling and immunoprecipitation studies indicated that both domains can mediate endocytosis of the HIV Env, and removal of both domains is required to enhance HIV Env protein surface stability. Analysis of immune responses induced by DNA immunization of mice showed that the DNA construct for the mutant Env exhibiting enhanced surface stability induced significantly higher levels of antibody responses against the HIV Env protein. Our results suggest that the HIV Env cytoplasmic domain may play important roles in virus infection and pathogenesis by modulating its immunogenicity.
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Affiliation(s)
- Ling Ye
- Department of Microbiology and Immunology and Vaccine Center, Emory University School of Medicine, 1510 Clifton Rd., Room 3033, Rollins Research Center, Atlanta, GA 30322, USA
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