1
|
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.
Collapse
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
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Viral and Host Factors Regulating HIV-1 Envelope Protein Trafficking and Particle Incorporation. Viruses 2022; 14:v14081729. [PMID: 36016351 PMCID: PMC9415270 DOI: 10.3390/v14081729] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/25/2022] [Accepted: 08/02/2022] [Indexed: 11/17/2022] Open
Abstract
The HIV-1 envelope glycoprotein (Env) is an essential structural component of the virus, serving as the receptor-binding protein and principal neutralizing determinant. Env trimers are incorporated into developing particles at the plasma membrane of infected cells. Incorporation of HIV-1 Env into particles in T cells and macrophages is regulated by the long Env cytoplasmic tail (CT) and the matrix region of Gag. The CT incorporates motifs that interact with cellular factors involved in endosomal trafficking. Env follows an unusual pathway to arrive at the site of particle assembly, first traversing the secretory pathway to the plasma membrane (PM), then undergoing endocytosis, followed by directed sorting to the site of particle assembly on the PM. Many aspects of Env trafficking remain to be defined, including the sequential events that occur following endocytosis, leading to productive recycling and particle incorporation. This review focuses on the host factors and pathways involved in Env trafficking, and discusses leading models of Env incorporation into particles.
Collapse
|
4
|
Hoffman HK, Aguilar RS, Clark AR, Groves NS, Pezeshkian N, Bruns MM, van Engelenburg SB. Endocytosed HIV-1 Envelope Glycoprotein Traffics to Rab14 + Late Endosomes and Lysosomes to Regulate Surface Levels in T-Cell Lines. J Virol 2022; 96:e0076722. [PMID: 35770989 PMCID: PMC9327703 DOI: 10.1128/jvi.00767-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 06/06/2022] [Indexed: 11/20/2022] Open
Abstract
Production of infectious HIV-1 particles requires incorporation of the viral envelope glycoprotein (Env) at the plasma membrane (PM) of infected CD4+ T cells. Env trafficking to the PM exposes viral epitopes that can be exploited by the host immune system; however, HIV-1 can evade this response by endocytosis of excess Env from the PM. The fate of Env after internalization remains unclear, with evidence suggesting several different vesicular trafficking steps may be involved, including recycling pathways. To date, there have been very few studies documenting the trafficking pathways of native Env in infected T cells. Furthermore, it remains unclear whether there are T-cell-specific endosomal pathways regulating the fate of endocytic Env. Here, we use a pulse-labeling approach with a monovalent anti-Env Fab probe to characterize the trafficking of internalized Env within infected CD4+ T-cell lines, together with CRISPR/Cas9-mediated endogenous protein tagging, to assess the role of host cell Rab GTPases in Env trafficking. We show that endocytosed Env traffics to Rab14+ compartments that possess hallmarks of late endosomes and lysosomes. We also demonstrate that Env can recycle back to the PM, although we find that recycling does not occur at high rates when compared to the model recycling protein transferrin. These results help to resolve open questions about the fate and relevance of endocytosed Env in HIV-infected cells and suggest a novel role for Rab14 in a cell-type-specific late-endosomal/lysosomal trafficking pathway in T cells. IMPORTANCE HIV-1 envelope glycoprotein (Env) evades immune neutralization through many mechanisms. One immune evasion strategy may result from the internalization of excess surface-exposed Env to prevent antibody-dependent cellular cytotoxicity or neutralization. Characterization of the fate of endocytosed Env is critical to understand which vesicular pathways could be targeted to promote display of Env epitopes to the immune system. In this study, we characterize the endocytic fate of native Env, expressed from infected human T-cell lines. We demonstrate that Env is rapidly trafficked to a late-endosome/lysosome-like compartment and can be recycled to the cell surface for incorporation into virus assembly sites. This study implicates a novel intracellular compartment, marked by host-cell Rab14 GTPases, for the sequestration of Env. Therapeutic approaches aimed at mobilizing this intracellular pool of Env could lead to stronger immune control of HIV-1 infection via antibody-dependent cell-mediated cytotoxicity.
Collapse
Affiliation(s)
- Huxley K. Hoffman
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Rebekah S. Aguilar
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Austin R. Clark
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Nicholas S. Groves
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Nairi Pezeshkian
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Merissa M. Bruns
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| | - Schuyler B. van Engelenburg
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, Colorado, USA
| |
Collapse
|
5
|
Snetkov X, Haider T, Mesner D, Groves N, van Engelenburg SB, Jolly C. A Conserved Tryptophan in the Envelope Cytoplasmic Tail Regulates HIV-1 Assembly and Spread. Viruses 2022; 14:v14010129. [PMID: 35062333 PMCID: PMC8778169 DOI: 10.3390/v14010129] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 01/07/2022] [Indexed: 12/14/2022] Open
Abstract
The HIV-1 envelope (Env) is an essential determinant of viral infectivity, tropism and spread between T cells. Lentiviral Env contain an unusually long 150 amino acid cytoplasmic tail (EnvCT), but the function of the EnvCT and many conserved domains within it remain largely uncharacterised. Here, we identified a highly conserved tryptophan motif at position 757 (W757) in the LLP-2 alpha helix of the EnvCT as a key determinant for HIV-1 replication and spread between T cells. Alanine substitution at this position potently inhibited HIV-1 cell–cell spread (the dominant mode of HIV-1 dissemination) by preventing recruitment of Env and Gag to sites of cell–cell contact, inhibiting virological synapse (VS) formation and spreading infection. Single-molecule tracking and super-resolution imaging showed that mutation of W757 dysregulates Env diffusion in the plasma membrane and increases Env mobility. Further analysis of Env function revealed that W757 is also required for Env fusion and infectivity, which together with reduced VS formation, result in a potent defect in viral spread. Notably, W757 lies within a region of the EnvCT recently shown to act as a supporting baseplate for Env. Our data support a model in which W757 plays a key role in regulating Env biology, modulating its temporal and spatial recruitment to virus assembly sites and regulating the inherent fusogenicity of the Env ectodomain, thereby supporting efficient HIV-1 replication and spread.
Collapse
Affiliation(s)
- Xenia Snetkov
- Division of Infection and Immunity, University College London, London WC1E 6BT, UK; (X.S.); (T.H.); (D.M.)
| | - Tafhima Haider
- Division of Infection and Immunity, University College London, London WC1E 6BT, UK; (X.S.); (T.H.); (D.M.)
| | - Dejan Mesner
- Division of Infection and Immunity, University College London, London WC1E 6BT, UK; (X.S.); (T.H.); (D.M.)
| | - Nicholas Groves
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, CO 80210, USA; (N.G.); (S.B.v.E.)
| | - Schuyler B. van Engelenburg
- Molecular and Cellular Biophysics Program, Department of Biological Sciences, University of Denver, Denver, CO 80210, USA; (N.G.); (S.B.v.E.)
| | - Clare Jolly
- Division of Infection and Immunity, University College London, London WC1E 6BT, UK; (X.S.); (T.H.); (D.M.)
- Correspondence:
| |
Collapse
|
6
|
Barría MI, Alvarez RA, Law K, Wolfson DL, Huser T, Chen BK. Endocytic Motif on a Biotin-Tagged HIV-1 Env Modulates the Co-Transfer of Env and Gag during Cell-to-Cell Transmission. Viruses 2021; 13:v13091729. [PMID: 34578310 PMCID: PMC8471404 DOI: 10.3390/v13091729] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/17/2021] [Accepted: 08/24/2021] [Indexed: 12/24/2022] Open
Abstract
During HIV-1 transmission through T cell virological synapses, the recruitment of the envelope (Env) glycoprotein to the site of cell-cell contact is important for adhesion and for packaging onto nascent virus particles which assemble at the site. Live imaging studies in CD4 T cells have captured the rapid recruitment of the viral structural protein Gag to VSs. We explored the role of endocytic trafficking of Env initiated by a membrane proximal tyrosine motif during HIV transfer into target cells and examined the factors that allow Gag and Env to be transferred together across the synapse. To facilitate tracking of Env in live cells, we adapted an Env tagging method and introduced a biotin acceptor peptide (BAP) into the V4 loop of Env gp120, enabling sensitive fluorescent tracking of V4-biotinylated Env. The BAP-tagged and biotinylated HIVs were replication-competent in cell-free and cell-to-cell infection assays. Live cell fluorescent imaging experiments showed rapid internalized cell surface Env on infected cells. Cell-cell transfer experiments conducted with the Env endocytosis mutant (Y712A) showed increased transfer of Env. Paradoxically, this increase in Env transfer was associated with significantly reduced Gag transfer into target cells, when compared to viral transfer associated with WT Env. This Y712A Env mutant also exhibited an altered Gag/biotin Env fluorescence ratio during transfer that correlated with decreased productive cell-to-cell infection. These results may suggest that the internalization of Env into recycling pools plays an important role in the coordinated transfer of Gag and Env across the VS, which optimizes productive infection in target cells.
Collapse
Affiliation(s)
- María Inés Barría
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Puerto Montt 5501842, Chile;
| | - Raymond A. Alvarez
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (R.A.A.); (K.L.)
| | - Kenneth Law
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (R.A.A.); (K.L.)
| | - Deanna L. Wolfson
- Department of Physics and Technology, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway;
| | - Thomas Huser
- Biomolecular Photonics, Department of Physics, Bielefeld University, 33615 Bielefeld, Germany;
| | - Benjamin K. Chen
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Puerto Montt 5501842, Chile;
- Correspondence:
| |
Collapse
|
7
|
Differential utilization of CD4+ by transmitted/founder and chronic envelope glycoproteins in a MSM HIV-1 subtype B transmission cluster. AIDS 2020; 34:2187-2200. [PMID: 32932339 DOI: 10.1097/qad.0000000000002690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE HIV-1 transmission leads to a genetic bottleneck, with one or a few variants of the donor quasispecies establishing an infection in the new host. We aimed to characterize this bottleneck in more detail, by comparing the properties of HIV envelope glycoproteins from acute and chronic infections within the particular context of a male-to-male transmission cluster. DESIGN We compared the genotypic and phenotypic properties of envelope glycoproteins from viral variants derived from five study participants from the same transmission cluster. METHODS We used single-genome amplification to generate a collection of full-length env sequences. We then constructed pseudotyped viruses expressing selected Env variants from the quasispecies infecting each study participant and compared their infectivities and sensitivities to various entry inhibitors. RESULTS The genotypic analyses confirmed the genetic bottleneck expected after HIV transmission, with a limited number of variants identified in four study participants during acute infection. However, the transmitted sequences harbored no evident common signature and belonged to various genetic lineages. The phenotypic analyses revealed no difference in infectivity, susceptibility to the CCR5 antagonist maraviroc, the fusion inhibitor enfurvitide or type-I interferon between viruses from participants with acute and chronic infections. The key property distinguishing transmitted viruses was a higher resistance to soluble CD4, correlated with greater sensitivity to occupation of the CD4 receptor by the anti-CD4 antibodies LM52 and SK3. CONCLUSION These results suggest that envelope glycoproteins from transmitted/founder viruses bind CD4 less efficiently than those of viruses from chronic infections.
Collapse
|
8
|
Matsuura R, Inabe K, Otsuki H, Kurokawa K, Dohmae N, Aida Y. Three YXXL Sequences of a Bovine Leukemia Virus Transmembrane Protein are Independently Required for Fusion Activity by Controlling Expression on the Cell Membrane. Viruses 2019; 11:v11121140. [PMID: 31835517 PMCID: PMC6950344 DOI: 10.3390/v11121140] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/05/2019] [Accepted: 12/08/2019] [Indexed: 01/27/2023] Open
Abstract
Bovine leukemia virus (BLV), which is closely related to human T-cell leukemia viruses, is the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle. The transmembrane subunit of the BLV envelope glycoprotein, gp30, contains three completely conserved YXXL sequences that fit an endocytic sorting motif. The two N-terminal YXXL sequences are reportedly critical for viral infection. However, their actual function in the viral life cycle remains undetermined. Here, we identified the novel roles of each YXXL sequence. Syncytia formation ability was upregulated by a single mutation of the tyrosine (Tyr) residue in any of the three YXXL sequences, indicating that each YXXL sequence is independently able to regulate the fusion event. The alteration resulted from significantly high expression of gp51 on the cell surface, thereby decreasing the amount of gp51 in early endosomes and further revealing that the three YXXL sequences are independently required for internalization of the envelope (Env) protein, following transport to the cell surface. Moreover, the 2nd and 3rd YXXL sequences contributed to Env protein incorporation into the virion by functionally distinct mechanisms. Our findings provide new insights regarding the three YXXL sequences toward the BLV viral life cycle and for developing new anti-BLV drugs.
Collapse
Affiliation(s)
- Ryosuke Matsuura
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Laboratory of Viral Infectious Diseases, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Kazunori Inabe
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Hiroyuki Otsuki
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Kazuo Kurokawa
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Naoshi Dohmae
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Yoko Aida
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Laboratory of Viral Infectious Diseases, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Nakamura Laboratory, Baton Zone program, Riken Cluster for Science, Technology and Innovation Hub, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Correspondence:
| |
Collapse
|
9
|
Evolution of the Envelope Glycoprotein of HIV-1 Clade B toward Higher Infectious Properties over the Course of the Epidemic. J Virol 2019; 93:JVI.01171-18. [PMID: 30567994 DOI: 10.1128/jvi.01171-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 12/11/2018] [Indexed: 01/01/2023] Open
Abstract
We showed previously that during the HIV/AIDS epidemic, the envelope glycoprotein (Env) of HIV-1, and in particular, the gp120 subunit, evolved toward an increased resistance to neutralizing antibodies at a population level. Here, we considered whether the antigenic evolution of the HIV-1 Env is associated with modifications of its functional properties, focusing on cell entry efficacy and interactions with the receptor and coreceptors. We tested the infectivity of a panel of Env-pseudotyped viruses derived from patients infected by subtype B viruses at three periods of the epidemic (1987 to 1991, 1996 to 2000, and 2006 to 2010). Pseudotyped viruses harboring Env from patients infected during the most recent period were approximately 10-fold more infectious in cell culture than those from patients infected at the beginning of the epidemic. This was associated with faster viral entry kinetics: contemporary viruses entered target cells approximately twice as fast as historical viruses. Contemporary viruses were also twice as resistant as historical viruses to the fusion inhibitor enfuvirtide. Resistance to enfuvirtide correlated with a resistance to CCR5 antagonists, suggesting that contemporary viruses expanded their CCR5 usage efficiency. Viruses were equally captured by DC-SIGN, but after binding to DC-SIGN, contemporary viruses infected target cells more efficiently than historical viruses. Thus, we report evidence that the infectious properties of the envelope glycoprotein of HIV-1 increased during the course of the epidemic. It is plausible that these changes affected viral fitness during the transmission process and might have contributed to an increasing virulence of HIV-1.IMPORTANCE Following primary infection by HIV-1, neutralizing antibodies (NAbs) exert selective pressure on the HIV-1 envelope glycoprotein (Env), driving the evolution of the viral population. Previous studies suggested that, as a consequence, Env has evolved at the HIV species level since the start of the epidemic so as to display greater resistance to NAbs. Here, we investigated whether the antigenic evolution of the HIV-1 Env is associated with modifications of its functional properties, focusing on cell entry efficacy and interactions with the receptor and coreceptors. Our data provide evidence that the infectious properties of the HIV-1 Env increased during the course of the epidemic. These changes may have contributed to increasing virulence of HIV-1 and an optimization of transmission between individuals.
Collapse
|
10
|
Murphy RE, Samal AB, Vlach J, Saad JS. Solution Structure and Membrane Interaction of the Cytoplasmic Tail of HIV-1 gp41 Protein. Structure 2017; 25:1708-1718.e5. [PMID: 29056482 DOI: 10.1016/j.str.2017.09.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 08/17/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022]
Abstract
The cytoplasmic tail of gp41 (gp41CT) remains the last HIV-1 domain with an unknown structure. It plays important roles in HIV-1 replication such as mediating envelope (Env) intracellular trafficking and incorporation into assembling virions, mechanisms of which are poorly understood. Here, we present the solution structure of gp41CT in a micellar environment and characterize its interaction with the membrane. We show that the N-terminal 45 residues are unstructured and not associated with the membrane. However, the C-terminal 105 residues form three membrane-bound amphipathic α helices with distinctive structural features such as variable degree of membrane penetration, hydrophobic and basic surfaces, clusters of aromatic residues, and a network of cation-π interactions. This work fills a major gap by providing the structure of the last segment of HIV-1 Env, which will provide insights into the mechanisms of Gag-mediated Env incorporation as well as the overall Env mobility and conformation on the virion surface.
Collapse
Affiliation(s)
- R Elliot Murphy
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Alexandra B Samal
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jiri Vlach
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jamil S Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
11
|
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.
Collapse
|
12
|
HIV-1 Cell-Free and Cell-to-Cell Infections Are Differentially Regulated by Distinct Determinants in the Env gp41 Cytoplasmic Tail. J Virol 2015; 89:9324-37. [PMID: 26136566 DOI: 10.1128/jvi.00655-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 06/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The HIV-1 envelope (Env) glycoprotein mediates viral entry during both cell-free and cell-to-cell infection of CD4(+) T cells. The highly conserved long cytoplasmic tail (CT) of Env is required in a cell type-dependent manner for optimal infectivity of cell-free virus. To probe the role of the CT in cell-to-cell infection, we tested a panel of mutations in the CT region that maintain or attenuate cell-free infection to investigate whether the functions of the CT are conserved during cell-free and cell-to-cell infection. The mutations tested included truncations of structural motifs in the gp41 CT and two point mutations in lentiviral lytic peptide 3 (LLP-3) previously described as disrupting the infectivity of cell-free virus. We found that small truncations of 28 to 43 amino acids (aa) or two LLP-3 point mutations, YW_SL and LL_RQ, severely impaired single-round cell-free infectivity 10-fold or more relative to wild-type full-length CT. These mutants showed a modest 2-fold reduction in cell-to-cell infection assays. Conversely, large truncations of 93 to 124 aa severely impaired cell-to-cell infectivity 20-fold or more while resulting in a 50% increase in infectivity of cell-free viral particles when produced in 293T cells. Intermediate truncations of 46 to 90 aa showed profound impairment of both modes of infection. Our results show that the abilities of Env to support cell-free and cell-to-cell infection are genetically distinct. These differences are cell type dependent for large-CT-truncation mutants. Additionally, point mutants in LLP-3 can maintain multiround propagation from cell-to-cell in primary CD4(+) T cells. IMPORTANCE The functions of HIV Env gp41 CT remain poorly understood despite being widely studied in the context of cell-free infection. We have identified domains of the gp41 CT responsible for striking selective deficiencies in either cell-free or cell-to-cell infectivity. These differences may reflect a different intrinsic regulatory influence of the CT on cell-associated versus particle-associated Env or differential interaction with host or viral proteins. Our findings provide novel insight into the key regulatory potential of the gp41 CT in cell-free and cell-to-cell HIV-1 infection, particularly for short-truncation mutants of ≤43 amino acids or mutants with point mutations in the LLP-3 helical domain of the CT, which are able to propagate via cell-to-cell infection in the absence of infectious cell-free virus production. These mutants may also serve as tools to further define the contributions of cell-free and cell-to-cell infection in vitro and in vivo.
Collapse
|
13
|
A tyrosine-based motif in the HIV-1 envelope glycoprotein tail mediates cell-type- and Rab11-FIP1C-dependent incorporation into virions. Proc Natl Acad Sci U S A 2015; 112:7575-80. [PMID: 26034275 DOI: 10.1073/pnas.1504174112] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Lentiviruses such as HIV-1 encode envelope glycoproteins (Env) with long cytoplasmic tails (CTs) that include motifs mediating interactions with host-cell-trafficking factors. We demonstrated recently that Rab11-family interacting protein 1C (FIP1C) is required for CT-dependent incorporation of Env into HIV-1 particles. Here, we used viruses bearing targeted substitutions within CT to map the FIP1C-dependent incorporation of Env. We identified YW795 as a critical motif mediating cell-type-dependent Env incorporation. Disruption of YW795 reproduced the cell-type-dependent particle incorporation of Env that had previously been observed with large truncations of CT. A revertant virus bearing a single amino acid change near the C terminus of CT restored wild-type levels of Env incorporation, Gag-Env colocalization on the plasma membrane, and viral replication. These findings highlight the importance of YW795 in the cell-type-dependent incorporation of Env and support a model of HIV assembly in which FIP1C/RCP mediates Env trafficking to the particle assembly site.
Collapse
|
14
|
Tedbury PR, Freed EO. The cytoplasmic tail of retroviral envelope glycoproteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:253-84. [PMID: 25595807 DOI: 10.1016/bs.pmbts.2014.10.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Retroviruses comprise a large, diverse group that infects a broad range of host organisms. Pathogenicity varies widely; the human immunodeficiency virus is the causative agent of acquired immunodeficiency syndrome, one of the world's leading infectious causes of death, while many nonhuman retroviruses cause cancer in the host. Retroviruses have been studied intensively, and great strides have been made in understanding aspects of retroviral biology. While the principal functions of the viral structural proteins are well understood, there remain many incompletely characterized domains. One of these is the cytoplasmic tail (CT) of the envelope glycoprotein. Several functions of the CT are highly conserved, whereas other properties are unique to a specific retrovirus. For example, the lentiviruses encode envelope glycoproteins with particularly large cytoplasmic domains. The functions of the long lentiviral envelope CT are still being deciphered. The reported functions of retroviral envelope CTs are discussed in this chapter.
Collapse
Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
| |
Collapse
|
15
|
Tartour K, Appourchaux R, Gaillard J, Nguyen XN, Durand S, Turpin J, Beaumont E, Roch E, Berger G, Mahieux R, Brand D, Roingeard P, Cimarelli A. IFITM proteins are incorporated onto HIV-1 virion particles and negatively imprint their infectivity. Retrovirology 2014; 11:103. [PMID: 25422070 PMCID: PMC4251951 DOI: 10.1186/s12977-014-0103-y] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 11/04/2014] [Indexed: 12/22/2022] Open
Abstract
Background Interferon induced transmembrane proteins 1, 2 and 3 (IFITMs) belong to a family of highly related antiviral factors that have been shown to interfere with a large spectrum of viruses including Filoviruses, Coronaviruses, Influenza virus, Dengue virus and HIV-1. In all these cases, the reported mechanism of antiviral inhibition indicates that the pool of IFITM proteins present in target cells blocks incoming viral particles in endosomal vesicles where they are subsequently degraded. Results In this study, we describe an additional mechanism through which IFITMs block HIV-1. In virus-producing cells, IFITMs coalesce with forming virions and are incorporated into viral particles. Expression of IFITMs during virion assembly leads to the production of virion particles of decreased infectivity that are mostly affected during entry in target cells. This mechanism of inhibition is exerted against different retroviruses and does not seem to be dependent on the type of Envelope present on retroviral particles. Conclusions The results described here identify a novel mechanism through which IFITMs affect HIV-1 infectivity during the late phases of the viral life cycle. Put in the context of data obtained by other laboratories, these results indicate that IFITMs can target HIV at two distinct moments of its life cycle, in target cells as well as in virus-producing cells. These results raise the possibility that IFITMs could similarly affect distinct steps of the life cycle of a number of other viruses. Electronic supplementary material The online version of this article (doi:10.1186/s12977-014-0103-y) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Kevin Tartour
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Romain Appourchaux
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Julien Gaillard
- Plateforme des Microscopies, PPF ASB, Université F. Rabelais et CHRU de Tours, Tours, France.
| | - Xuan-Nhi Nguyen
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Stéphanie Durand
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Jocelyn Turpin
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Elodie Beaumont
- INSERM U966, Université F. Rabelais et CHRU de Tours, Tours, France.
| | - Emmanuelle Roch
- INSERM U966, Université F. Rabelais et CHRU de Tours, Tours, France.
| | - Gregory Berger
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France. .,Present address: Department of Infectious Diseases, King's College London School of Medicine, London, SE1 9RT, UK.
| | - Renaud Mahieux
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| | - Denys Brand
- INSERM U966, Université F. Rabelais et CHRU de Tours, Tours, France.
| | - Philippe Roingeard
- Plateforme des Microscopies, PPF ASB, Université F. Rabelais et CHRU de Tours, Tours, France. .,INSERM U966, Université F. Rabelais et CHRU de Tours, Tours, France.
| | - Andrea Cimarelli
- CIRI, Centre International de Recherche en Infectiologie, Lyon, F69364, France. .,INSERM, U1111, 46 Allée d'Italie, Lyon, F69364, France. .,Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, F69364, France. .,CNRS, UMR5308, 46 Allée d'Italie, Lyon, F69364, France. .,University of Lyon, Lyon I, UMS3444/US8 BioSciences Gerland, Lyon, F69364, France.
| |
Collapse
|
16
|
Bohl CR, Abrahamyan LG, Wood C. Human Ubc9 is involved in intracellular HIV-1 Env stability after trafficking out of the trans-Golgi network in a Gag dependent manner. PLoS One 2013; 8:e69359. [PMID: 23861967 PMCID: PMC3704627 DOI: 10.1371/journal.pone.0069359] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 06/07/2013] [Indexed: 01/03/2023] Open
Abstract
The cellular E2 Sumo conjugase, Ubc9 interacts with HIV-1 Gag, and is important for the assembly of infectious HIV-1 virions. In the previous study we demonstrated that in the absence of Ubc9, a defect in virion assembly was associated with decreased levels of mature intracellular Envelope (Env) that affected Env incorporation into virions and virion infectivity. We have further characterized the effect of Ubc9 knockdown on HIV Env processing and assembly. We found that gp160 stability in the endoplasmic reticulum (ER) and its trafficking to the trans-Golgi network (TGN) were unaffected, indicating that the decreased intracellular mature Env levels in Ubc9-depleted cells were due to a selective degradation of mature Env gp120 after cleavage from gp160 and trafficked out of the TGN. Decreased levels of Gag and mature Env were found to be associated with the plasma membrane and lipid rafts, which suggest that these viral proteins were not trafficked correctly to the assembly site. Intracellular gp120 were partially rescued when treated with a combination of lysosome inhibitors. Taken together our results suggest that in the absence of Ubc9, gp120 is preferentially degraded in the lysosomes likely before trafficking to assembly sites leading to the production of defective virions. This study provides further insight in the processing and packaging of the HIV-1 gp120 into mature HIV-1 virions.
Collapse
Affiliation(s)
- Christopher R. Bohl
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Levon G. Abrahamyan
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Charles Wood
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| |
Collapse
|
17
|
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.
Collapse
|
18
|
Mutational analysis of the internal membrane proximal domain of the HIV glycoprotein C-terminus. Virology 2013; 440:31-40. [DOI: 10.1016/j.virol.2013.01.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 01/28/2013] [Accepted: 01/31/2013] [Indexed: 01/26/2023]
|
19
|
Baalwa J, Wang S, Parrish NF, Decker JM, Keele BF, Learn GH, Yue L, Ruzagira E, Ssemwanga D, Kamali A, Amornkul PN, Price MA, Kappes JC, Karita E, Kaleebu P, Sanders E, Gilmour J, Allen S, Hunter E, Montefiori DC, Haynes BF, Cormier E, Hahn BH, Shaw GM. Molecular identification, cloning and characterization of transmitted/founder HIV-1 subtype A, D and A/D infectious molecular clones. Virology 2012; 436:33-48. [PMID: 23123038 DOI: 10.1016/j.virol.2012.10.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 09/25/2012] [Accepted: 10/05/2012] [Indexed: 11/18/2022]
Abstract
We report the molecular identification, cloning and initial biological characterization of 12 full-length HIV-1 subtype A, D and A/D recombinant transmitted/founder (T/F) genomes. T/F genomes contained intact canonical open reading frames and all T/F viruses were replication competent in primary human T-cells, although subtype D virus replication was more efficient (p<0.05). All 12 viruses utilized CCR5 but not CXCR4 as a co-receptor for entry and exhibited a neutralization profile typical of tier 2 primary virus strains, with significant differences observed between subtype A and D viruses with respect to sensitivity to monoclonal antibodies VRC01, PG9 and PG16 and polyclonal subtype C anti-HIV IgG (p<0.05 for each). The present report doubles the number of T/F HIV-1 clones available for pathogenesis and vaccine research and extends their representation to include subtypes A, B, C and D.
Collapse
Affiliation(s)
- Joshua Baalwa
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
HIV cell-to-cell transmission requires the production of infectious virus particles and does not proceed through env-mediated fusion pores. J Virol 2012; 86:3924-33. [PMID: 22258237 DOI: 10.1128/jvi.06478-11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Direct cell-to-cell transmission of human immunodeficiency virus (HIV) is a more potent and efficient means of virus propagation than infection by cell-free virus particles. The aim of this study was to determine whether cell-to-cell transmission requires the assembly of enveloped virus particles or whether nucleic acids with replication potential could translocate directly from donor to target cells through envelope glycoprotein (Env)-induced fusion pores. To this end, we characterized the transmission properties of viruses carrying mutations in the matrix protein (MA) that affect the incorporation of Env into virus particles but do not interfere with Env-mediated cell-cell fusion. By use of cell-free virus, the infectivity of MA mutant viruses was below the detection threshold both in single-cycle and in multiple-cycle assays. Truncation of the cytoplasmic tail (CT) of Env restored the incorporation of Env into MA mutant viruses and rescued their cell-free infectivity to different extents. In cell-to-cell transmission assays, MA mutations prevented HIV transmission from donor to target cells, despite efficient Env-dependent membrane fusion. HIV transmission was blocked at the level of virus core translocation into the cytosol of target cells. As in cell-free assays, rescue of Env incorporation by truncation of the Env CT restored the virus core translocation and cell-to-cell infectivity of MA mutant viruses. These data show that HIV cell-to-cell transmission requires the assembly of enveloped virus particles. The increased efficiency of this infection route may thus be attributed to the high local concentrations of virus particles at sites of cellular contacts rather than to a qualitatively different transmission process.
Collapse
|
21
|
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.
Collapse
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
| | | | | | | | | |
Collapse
|
22
|
Abstract
Infection of domestic cats with virulent strains of the feline immunodeficiency virus (FIV) leads to an acquired immunodeficiency syndrome (AIDS), similar to the pathogenesis induced in humans by infection with human immunodeficiency virus type 1 (HIV-1). Thus, FIV is a highly relevant model for anti-HIV therapy and vaccine development. FIV is not infectious in humans, so it is also a potentially effective non-toxic gene therapy vector. To make better use of this model, it is important to define the cellular machinery utilized by each virus to produce virus particles so that relevant similarities can be identified. It is well understood that all replication-competent retroviruses encode gag, pol, and env genes, which provide core elements for virus replication. As a result, most antiretroviral therapy targets pol-derived enzymes (protease, reverse transcriptase, and integrase) orenv-derived glycoproteins that mediate virus attachment and entry. However, resistance to drugs against these targets is a persistent problem, and novel targets must be identified to produce more effective drugs that can either substitute or be combined with current therapy. Elements of the gag gene (matrix, capsid, nucleocapsid, and "late" domains) have yet to be exploited as antiviral targets, even though the Gag precursor polyprotein is self-sufficient for the assembly and release of virus particles from cells. This process is far better understood in primate lentiviruses, especially HIV-1. However, there has been significant progress in recent years in defining how FIV Gag is targeted to the cellular plasma membrane, assembles into virions, incorporates FIV Env glycoproteins, and utilizes host cell machinery to complete virus release. Recent discoveries of intracellular restriction factors that target HIV-1 and FIV capsids after virus entry have also opened exciting new areas of research. This review summarizes currently known interactions involving HIV-1 and FIV Gag that affect virus release, infectivity, and replication.
Collapse
Affiliation(s)
- Benjamin G Luttge
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA
| | | |
Collapse
|
23
|
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.
Collapse
|
24
|
Bandawe GP, Martin DP, Treurnicht F, Mlisana K, Karim SSA, Williamson C. Conserved positive selection signals in gp41 across multiple subtypes and difference in selection signals detectable in gp41 sequences sampled during acute and chronic HIV-1 subtype C infection. Virol J 2008; 5:141. [PMID: 19025632 PMCID: PMC2630941 DOI: 10.1186/1743-422x-5-141] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 11/24/2008] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The high diversity of HIV variants driving the global AIDS epidemic has caused many to doubt whether an effective vaccine against the virus is possible. However, by identifying the selective forces that are driving the ongoing diversification of HIV and characterising their genetic consequences, it may be possible to design vaccines that pre-empt some of the virus' more common evasion tactics. One component of such vaccines might be the envelope protein, gp41. Besides being targeted by both the humoral and cellular arms of the immune system this protein mediates fusion between viral and target cell membranes and is likely to be a primary determinant of HIV transmissibility. RESULTS Using recombination aware analysis tools we compared site specific signals of selection in gp41 sequences from different HIV-1 M subtypes and circulating recombinant forms and identified twelve sites evolving under positive selection across multiple major HIV-1 lineages. To identify evidence of selection operating during transmission our analysis included two matched datasets sampled from patients with acute or chronic subtype C infections. We identified six gp41 sites apparently evolving under different selection pressures during acute and chronic HIV-1 infections. These sites mostly fell within functional gp41 domains, with one site located within the epitope recognised by the broadly neutralizing antibody, 4E10. CONCLUSION Whereas these six sites are potentially determinants of fitness and are therefore good candidate targets for subtype-C specific vaccines, the twelve sites evolving under diversifying selection across multiple subtypes might make good candidate targets for broadly protective vaccines.
Collapse
Affiliation(s)
- Gama P Bandawe
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925, South Africa
| | - Darren P Martin
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925, South Africa
| | - Florette Treurnicht
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925, South Africa
| | - Koleka Mlisana
- Doris Duke Medical Research Institute, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Private Bag X7, Congella, 4013, South Africa
| | - Salim S Abdool Karim
- Doris Duke Medical Research Institute, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Private Bag X7, Congella, 4013, South Africa
| | - Carolyn Williamson
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925, South Africa
| | | |
Collapse
|
25
|
Implications of recombination for HIV diversity. Virus Res 2008; 134:64-73. [PMID: 18308413 DOI: 10.1016/j.virusres.2008.01.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Revised: 01/08/2008] [Accepted: 01/09/2008] [Indexed: 01/20/2023]
Abstract
The human immunodeficiency virus (HIV) population is characterised by extensive genetic variability that results from high error and recombination rates of the reverse transcription process, and from the fast turnover of virions in HIV-infected individuals. Among the viral variants encountered at the global scale, recombinant forms are extremely abundant. Some of these recombinants (known as circulating recombinant forms) become fixed and undergo rapid expansion in the population. The reasons underlying their epidemiological success remain at present poorly understood and constitute a fascinating area for future research to improve our understanding of immune escape, pathogenicity and transmission. Recombinant viruses are generated during reverse transcription as a consequence of template switching between the two genetically different genomic RNAs present in a heterozygous virus. Recombination can thereby generate shortcuts in evolution by producing mosaic reverse transcription products of parental genomes. Therefore, in a single infectious cycle multiple mutations that are positively selected can be combined or, conversely, negatively selected mutations can be removed. Recombination is therefore involved in different aspects of HIV evolution, adaptation to its host, and escape from antiviral treatments.
Collapse
|
26
|
Nora T, Bouchonnet F, Labrosse B, Charpentier C, Mammano F, Clavel F, Hance AJ. Functional diversity of HIV-1 envelope proteins expressed by contemporaneous plasma viruses. Retrovirology 2008; 5:23. [PMID: 18312646 PMCID: PMC2270869 DOI: 10.1186/1742-4690-5-23] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 02/29/2008] [Indexed: 11/10/2022] Open
Abstract
Background Numerous studies have shown that viral quasi-species with genetically diverse envelope proteins (Env) replicate simultaneously in patients infected with the human immunodeficiency virus type 1 (HIV-1). Less information is available concerning the extent that envelope sequence diversity translates into a diversity of phenotypic properties, including infectivity and resistance to entry inhibitors. Methods To study these questions, we isolated genetically distinct contemporaneous clonal viral populations from the plasma of 5 HIV-1 infected individuals (n = 70), and evaluated the infectivity of recombinant viruses expressing Env proteins from the clonal viruses in several target cells. The sensitivity to entry inhibitors (enfuvirtide, TAK-799), soluble CD4 and monoclonal antibodies (2G12, 48d, 2F5) was also evaluated for a subset of the recombinant viruses (n = 20). Results Even when comparisons were restricted to viruses with similar tropism, the infectivity for a given target cell of viruses carrying different Env proteins from the same patient varied over an approximately 10-fold range, and differences in their relative ability to infect different target cells were also observed. Variable region haplotypes associated with high and low infectivity could be identified for one patient. In addition, clones carrying unique mutations in V3 often displayed low infectivity. No correlation was observed between viral infectivity and sensitivity to inhibition by any of the six entry inhibitors evaluated, indicating that these properties can be dissociated. Significant inter-patient differences, independent of infectivity, were observed for the sensitivity of Env proteins to several entry inhibitors and their ability to infect different target cells. Conclusion These findings demonstrate the marked functional heterogeneity of HIV-1 Env proteins expressed by contemporaneous circulating viruses, and underscore the advantage of clonal analyses in characterizing the spectrum of functional properties of the genetically diverse viral populations present in a given patient.
Collapse
Affiliation(s)
- Tamara Nora
- Unité de Recherche Antivirale, INSERM U 552, Université Denis Diderot Paris 7, Paris F-75018, France.
| | | | | | | | | | | | | |
Collapse
|
27
|
Blay WM, Kasprzyk T, Misher L, Richardson BA, Haigwood NL. Mutations in envelope gp120 can impact proteolytic processing of the gp160 precursor and thereby affect neutralization sensitivity of human immunodeficiency virus type 1 pseudoviruses. J Virol 2007; 81:13037-49. [PMID: 17855534 PMCID: PMC2169095 DOI: 10.1128/jvi.01215-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The design of an efficient human immunodeficiency virus (HIV) immunogen able to generate broad neutralizing antibodies (NAbs) remains an elusive goal. As more data emerge, it is becoming apparent that one important aspect of such an immunogen will be the proper representation of the envelope protein (Env) as it exists on native virions. Important questions that are yet to be fully addressed include what factors dictate Env processing, how different Env forms are represented on the virion, and ultimately how these issues influence the development and efficacy of NAbs. Recent data have begun to illuminate the extent to which changes in gp41 can impact the overall structure and neutralizing sensitivity of Env. Here, we present evidence to suggest that minor mutations in gp120 can significantly impact Env processing. We analyzed the gp120 sequences of 20 env variants that evolved in multiple macaques over 8 months of infection with simian/human immunodeficiency virus 89.6P. Variant gp120 sequences were subcloned into gp160 expression plasmids with identical cleavage motifs and gp41 sequences. Cells cotransfected with these plasmids and delta env genomes were able to produce competent virus. The resulting pseudoviruses incorporated high levels of Env onto virions that exhibited a range of degrees of virion-associated Env cleavage (15 to 40%). Higher levels of cleavage correlated with increased infectivity and increased resistance to macaque plasma, HIV immunoglobulin, soluble CD4, and human monoclonal antibodies 4E10, 2F5, and b12. Based on these data, we discuss a model whereby changes in gp120 of 89.6P impact Env processing and thereby mediate escape from a range of neutralizing agents.
Collapse
Affiliation(s)
- Wendy M Blay
- Seattle Biomedical Research Institute, 307 Westlake Ave. N, Seattle, WA 98019, USA
| | | | | | | | | |
Collapse
|
28
|
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.
Collapse
Affiliation(s)
- Jason T Newman
- Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, PA 15261, USA
| | | | | | | |
Collapse
|