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Heinrich F, Thomas CE, Alvarado JJ, Eells R, Thomas A, Doucet M, Whitlatch KN, Aryal M, Lösche M, Smithgall TE. Neutron Reflectometry and Molecular Simulations Demonstrate HIV-1 Nef Homodimer Formation on Model Lipid Bilayers. J Mol Biol 2023; 435:168009. [PMID: 36773691 PMCID: PMC10079580 DOI: 10.1016/j.jmb.2023.168009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/16/2023] [Accepted: 02/03/2023] [Indexed: 02/12/2023]
Abstract
The HIV-1 Nef protein plays a critical role in viral infectivity, high-titer replication in vivo, and immune escape of HIV-infected cells. Nef lacks intrinsic biochemical activity, functioning instead through interactions with diverse host cell signaling proteins and intracellular trafficking pathways. Previous studies have established an essential role for Nef homodimer formation at the plasma membrane for most if not all its functions. Here we combined neutron reflectometry of full-length myristoylated Nef bound to model lipid bilayers with molecular simulations based on previous X-ray crystal structures of Nef homodimers. This integrated approach provides direct evidence that Nef associates with the membrane as a homodimer with its structured core region displaced from the membrane for partner protein engagement. Parallel studies of a dimerization-defective mutant, Nef-L112D, demonstrate that the helical dimerization interface present in previous crystal structures stabilizes the membrane-bound dimer. X-ray crystallography of the Nef-L112D mutant in complex with the SH3 domain of the Nef-associated host cell kinase Hck revealed a monomeric 1:1 complex instead of the 2:2 dimer complex formed with wild-type Nef. Importantly, the crystal structure of the Nef-L112D core and SH3 interface are virtually identical to the wild-type complex, indicating that this mutation does not affect the overall Nef fold. These findings support the intrinsic capacity of Nef to homodimerize at lipid bilayers using structural features present in X-ray crystal structures of dimeric complexes.
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Affiliation(s)
- Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; NIST Center for Neutron Research, Gaithersburg, MD 20899, USA
| | - Catherine E Thomas
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - John J Alvarado
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Rebecca Eells
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Alyssa Thomas
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Mathieu Doucet
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Kindra N Whitlatch
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Manish Aryal
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; NIST Center for Neutron Research, Gaithersburg, MD 20899, USA
| | - Thomas E Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
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HIV-1 Nef Protein Affects Cytokine and Extracellular Vesicles Production in the GEN2.2 Plasmacytoid Dendritic Cell Line. Viruses 2021; 14:v14010074. [PMID: 35062278 PMCID: PMC8780779 DOI: 10.3390/v14010074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 12/24/2021] [Accepted: 12/28/2021] [Indexed: 11/16/2022] Open
Abstract
Plasmacytoid dendritic cells (pDCs) are a unique dendritic cell subset specialized in type I interferon production, whose role in Human Immunodeficiency Virus (HIV) infection and pathogenesis is complex and not yet well defined. Considering the crucial role of the accessory protein Nef in HIV pathogenicity, possible alterations in intracellular signalling and extracellular vesicle (EV) release induced by exogenous Nef on uninfected pDCs have been investigated. As an experimental model system, a human plasmacytoid dendritic cell line, GEN2.2, stimulated with a myristoylated recombinant NefSF2 protein was employed. In GEN2.2 cells, Nef treatment induced the tyrosine phosphorylation of STAT-1 and STAT-2 and the production of a set of cytokines, chemokines and growth factors including IP-10, MIP-1β, MCP-1, IL-8, TNF-α and G-CSF. The released factors differed both in type and amount from those released by macrophages treated with the same viral protein. Moreover, Nef treatment slightly reduces the production of small EVs, and the protein was found associated with the small (size < 200 nm) but not the medium/large vesicles (size > 200 nm) collected from GEN2.2 cells. These results add new information on the interactions between this virulence factor and uninfected pDCs, and may provide the basis for further studies on the interactions of Nef protein with primary pDCs.
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Multifunctional Roles of the N-Terminal Region of HIV-1 SF2Nef Are Mediated by Three Independent Protein Interaction Sites. J Virol 2019; 94:JVI.01398-19. [PMID: 31597760 DOI: 10.1128/jvi.01398-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 10/01/2019] [Indexed: 01/23/2023] Open
Abstract
HIV-1 Nef promotes virus spread and disease progression by altering host cell transport and signaling processes through interaction with multiple host cell proteins. The N-terminal region in HIV-1 Nef encompassing residues 12 to 39 has been implicated in many Nef activities, including disruption of CD4 T lymphocyte polarization and homing to lymph nodes, antagonism of SERINC5 restriction to virion infectivity, downregulation of cell surface CD4 and major histocompatibility complex class I (MHC-I), release of Nef-containing extracellular vesicles, and phosphorylation of Nef by recruitment of the Nef-associated kinase complex (NAKC). How this region mediates these pleiotropic functions is unclear. Characterization of a panel of alanine mutants spanning the N-terminal region to identify specific functional determinants revealed this region to be dispensable for effects of Nef from HIV-1 strain SF2 (HIV-1SF2Nef) on T cell actin organization and chemotaxis, retargeting of the host cell kinase Lck to the trans-Golgi network, and incorporation of Nef into extracellular vesicles. MHC-I downmodulation was specific to residue M20, and inhibition of T cell polarization by Nef required the integrity of the entire region. In contrast, downmodulation of cell surface CD4 and SERINC5 antagonism were mediated by a specific motif encompassing residues 32 to 39 that was also essential for efficient HIV replication in primary CD4 T lymphocytes. Finally, Nef phosphorylation via association with the NAKC was mediated by two EP repeats within residues 24 to 29 but was dispensable for other functions. These results identify the N-terminal region as a multifunctional interaction module for at least three different host cell ligands that mediate independent functions of HIV-1SF2Nef to facilitate immune evasion and virus spread.IMPORTANCE HIV-1 Nef critically determines virus spread and disease progression in infected individuals by acting as a protein interaction adaptor via incompletely defined mechanisms and ligands. Residues 12 to 39 near the N terminus of Nef have been described as an interaction platform for the Nef-associated kinase complex (NAKC) and were recently identified as essential determinants for a broad range of Nef activities. Here, we report a systematic mapping of this amino acid stretch that revealed the presence of three independent interaction motifs with specific ligands and activities. While downmodulation of cell surface MHC-I depends on M20, two EP repeats are the minimal binding site for the NAKC, and residues 32 to 39 mediate antagonism of the host cell restriction factor SERINC5 as well as downmodulation of cell surface CD4. These results reveal that the N-terminal region of HIV-1SF2Nef is a versatile and multifunctional protein interaction module that exerts essential functions of the pathogenicity factor via independent mechanisms.
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Abstract
The accessory protein Nef of human immunodeficiency virus (HIV) is a primary determinant of viral pathogenesis. Nef is abundantly expressed during infection and reroutes a variety of cell surface proteins to disrupt host immunity and promote the viral replication cycle. Nef counteracts host defenses by sequestering and/or degrading its targets via the endocytic and secretory pathways. Nef does this by physically engaging a number of host trafficking proteins. Substantial progress has been achieved in identifying the targets of Nef, and a structural and mechanistic understanding of Nef's ability to command the protein trafficking machinery has recently started to coalesce. Comparative analysis of HIV and simian immunodeficiency virus (SIV) Nef proteins in the context of recent structural advances sheds further light on both viral evolution and the mechanisms whereby trafficking is hijacked. This review describes how advances in cell and structural biology are uncovering in growing detail how Nef subverts the host immune system, facilitates virus release, and enhances viral infectivity.
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Palmeira JDF, Argañaraz GA, de Oliveira GXLM, Argañaraz ER. Physiological relevance of ACOT8-Nef interaction in HIV infection. Rev Med Virol 2019; 29:e2057. [PMID: 31179598 DOI: 10.1002/rmv.2057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 04/29/2019] [Accepted: 05/01/2019] [Indexed: 11/06/2022]
Abstract
During human immunodeficiency virus (HIV) infection, Nef viral protein plays a crucial role in viral pathogenesis and progression of acquired immunodeficiency syndrome. Nef is expressed in the early stages of infection and alters the cellular environment increasing infectivity, viral replication, and the evasion of host immune response through several mechanisms. Nef has numerous functional domains that allow it to interact with a number of proteins, interfering with intracellular traffic. Among these proteins, human peroxisomal thioesterase 8, ACOT8, has been shown to be an important cellular partner of Nef. It has been suggested that this interaction may be involved in Nef-dependent endocytosis and also in the modulation of lipid composition in membrane rafts. However, the actual role of this interaction, as well as the mechanisms involved, has not yet been fully elucidated. In this review, we focused on the interplay between Nef and ACOT8 proteins, highlighting the possible physiological relevance in HIV infection.
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Affiliation(s)
| | - Gustavo A Argañaraz
- Laboratory of Molecular Neurovirology, Faculty of Health Science, University of Brasília, Brazil
| | | | - Enrique R Argañaraz
- Laboratory of Molecular Neurovirology, Faculty of Health Science, University of Brasília, Brazil
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Slow Release of HIV-1 Protein Nef from Vesicle-like Structures Is Inhibited by Cytosolic Calcium Elevation in Single Human Microglia. Mol Neurobiol 2018; 56:102-118. [DOI: 10.1007/s12035-018-1072-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/09/2018] [Indexed: 12/14/2022]
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De Cicco M, Milroy LG, Dames SA. Target of rapamycin FATC domain as a general membrane anchor: The FKBP-12 like domain of FKBP38 as a case study. Protein Sci 2017; 27:546-560. [PMID: 29024217 DOI: 10.1002/pro.3321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 01/11/2023]
Abstract
Increased efforts have been undertaken to better understand the formation of signaling complexes at cellular membranes. Since the preparation of proteins containing a transmembrane domain or a prenylation motif is generally challenging an alternative membrane anchoring unit that is easy to attach, water-soluble and binds to different membrane mimetics would find broad application. The 33-residue long FATC domain of yeast TOR1 (y1fatc) fulfills these criteria and binds to neutral and negatively charged micelles, bicelles, and liposomes. As a case study, we fused it to the FKBP506-binding region of the protein FKBP38 (FKBP38-BD) and used 1 H-15 N NMR spectroscopy to characterize localization of the chimeric protein to micelles, bicelles, and liposomes. Based on these and published data for y1fatc, its use as a C-terminally attachable membrane anchor for other proteins is compatible with a wide range of buffer conditions (pH circa 6-8.5, NaCl 0 to >150 mM, presence of reducing agents, different salts such as MgCl2 and CaCl2 ). The high water-solubility of y1fatc enables its use for titration experiments against a membrane-localized interaction partner of the fused target protein. Results from studies with peptides corresponding to the C-terminal 17-11 residues of the 33-residue long domain by 1D 1 H NMR and CD spectroscopy indicate that they still can interact with membrane mimetics. Thus, they may be used as membrane anchors if the full y1fatc sequence is disturbing or if a chemically synthesized y1fatc peptide shall be attached by native chemical ligation, for example, unlabeled peptide to 15 N-labeled target protein for NMR studies.
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Affiliation(s)
- Maristella De Cicco
- Department of Chemistry, Technische Universität München, Biomolecular NMR Spectroscopy, Garching, Germany
| | - Lech-G Milroy
- Department of Biomedical Technology, Laboratory of Chemical Biology, Technische Universiteit Eindhoven, Eindhoven, The Netherlands
| | - Sonja A Dames
- Department of Chemistry, Technische Universität München, Biomolecular NMR Spectroscopy, Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany
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Manrique S, Sauter D, Horenkamp FA, Lülf S, Yu H, Hotter D, Anand K, Kirchhoff F, Geyer M. Endocytic sorting motif interactions involved in Nef-mediated downmodulation of CD4 and CD3. Nat Commun 2017; 8:442. [PMID: 28874665 PMCID: PMC5585231 DOI: 10.1038/s41467-017-00481-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 07/03/2017] [Indexed: 12/24/2022] Open
Abstract
Lentiviral Nefs recruit assembly polypeptide complexes and target sorting motifs in cellular receptors to induce their internalization. While Nef-mediated CD4 downmodulation is conserved, the ability to internalize CD3 was lost in HIV-1 and its precursors. Although both functions play key roles in lentiviral replication and pathogenicity, the underlying structural requirements are poorly defined. Here, we determine the structure of SIVmac239 Nef bound to the ExxxLM motif of another Nef molecule at 2.5 Å resolution. This provides a basis for a structural model, where a hydrophobic crevice in simian immunodeficiency virus (SIV) Nef targets a dileucine motif in CD4 and a tyrosine-based motif in CD3. Introducing key residues into this crevice of HIV-1 Nef enables CD3 binding but an additional N-terminal tyrosine motif is required for internalization. Our resolution of the CD4/Nef/AP2 complex and generation of HIV-1 Nefs capable of CD3 downregulation provide insights into sorting motif interactions and target discrimination of Nef.HIV and simian immunodeficiency virus (SIV) Nef proteins both stimulate the clathrin-mediated endocytosis of CD4 but differ in downmodulation of the immune receptor CD3. Here, the authors present the structure of SIV Nef bound to the ExxxLM motif of another Nef molecule, which allows them to propose a model how Nef recognizes these motifs in CD3 and CD4.
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Affiliation(s)
- Santiago Manrique
- Institute of Innate Immunity, Department of Structural Immunology, University of Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Germany.,Max Planck-Institute of Molecular Physiology, Department Physical Biochemistry, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Daniel Sauter
- Institute of Molecular Virology, Ulm University Medical Center, Meyerhofstr. 1, 89081, Ulm, Germany
| | - Florian A Horenkamp
- Max Planck-Institute of Molecular Physiology, Department Physical Biochemistry, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Sebastian Lülf
- Max Planck-Institute of Molecular Physiology, Department Physical Biochemistry, Otto-Hahn-Str. 11, 44227, Dortmund, Germany.,Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany
| | - Hangxing Yu
- Institute of Molecular Virology, Ulm University Medical Center, Meyerhofstr. 1, 89081, Ulm, Germany
| | - Dominik Hotter
- Institute of Molecular Virology, Ulm University Medical Center, Meyerhofstr. 1, 89081, Ulm, Germany
| | - Kanchan Anand
- Institute of Innate Immunity, Department of Structural Immunology, University of Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Germany.,Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany
| | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, Meyerhofstr. 1, 89081, Ulm, Germany
| | - Matthias Geyer
- Institute of Innate Immunity, Department of Structural Immunology, University of Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Germany. .,Max Planck-Institute of Molecular Physiology, Department Physical Biochemistry, Otto-Hahn-Str. 11, 44227, Dortmund, Germany. .,Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
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Affiliation(s)
- Tom Mejuch
- Department
of Chemical Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Herbert Waldmann
- Department
of Chemical Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
- Department
of Chemistry and Chemical Biology, Technical University of Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany
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Hunegnaw R, Vassylyeva M, Dubrovsky L, Pushkarsky T, Sviridov D, Anashkina AA, Üren A, Brichacek B, Vassylyev DG, Adzhubei AA, Bukrinsky M. Interaction Between HIV-1 Nef and Calnexin: From Modeling to Small Molecule Inhibitors Reversing HIV-Induced Lipid Accumulation. Arterioscler Thromb Vasc Biol 2016; 36:1758-71. [PMID: 27470515 DOI: 10.1161/atvbaha.116.307997] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 07/13/2016] [Indexed: 01/22/2023]
Abstract
OBJECTIVE HIV-infected patients are at an increased risk of developing atherosclerosis, in part because of downmodulation and functional impairment of ATP-binding cassette A1 (ABCA1) cholesterol transporter by the HIV-1 protein Nef. The mechanism of this effect involves Nef interacting with an ER chaperone calnexin and disrupting calnexin binding to ABCA1, leading to ABCA1 retention in ER, its degradation and resulting suppression of cholesterol efflux. However, molecular details of Nef-calnexin interaction remained unknown, limiting the translational impact of this finding. APPROACH AND RESULTS Here, we used molecular modeling and mutagenesis to characterize Nef-calnexin interaction and to identify small molecule compounds that could block it. We demonstrated that the interaction between Nef and calnexin is direct and can be reconstituted using recombinant proteins in vitro with a binding affinity of 89.1 nmol/L measured by surface plasmon resonance. The cytoplasmic tail of calnexin is essential and sufficient for interaction with Nef, and binds Nef with an affinity of 9.4 nmol/L. Replacing lysine residues in positions 4 and 7 of Nef with alanines abrogates Nef-calnexin interaction, prevents ABCA1 downregulation by Nef, and preserves cholesterol efflux from HIV-infected cells. Through virtual screening of the National Cancer Institute library of compounds, we identified a compound, 1[(7-oxo-7H-benz[de]anthracene-3-yl)amino]anthraquinone, which blocked Nef-calnexin interaction, partially restored ABCA1 activity in HIV-infected cells, and reduced foam cell formation in a culture of HIV-infected macrophages. CONCLUSION This study identifies potential targets that can be exploited to block the pathogenic effect of HIV infection on cholesterol metabolism and prevent atherosclerosis in HIV-infected subjects.
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Affiliation(s)
- Ruth Hunegnaw
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Marina Vassylyeva
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Larisa Dubrovsky
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Tatiana Pushkarsky
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Dmitri Sviridov
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Anastasia A Anashkina
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Aykut Üren
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Beda Brichacek
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Dmitry G Vassylyev
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü)
| | - Alexei A Adzhubei
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü).
| | - Michael Bukrinsky
- From the George Washington University School of Medicine and Health Sciences, Washington, DC (R.H., L.D., T.P., B.B., A.A.A., M.B.); University of Alabama School of Medicine and Dentistry, Birmingham, (M.V., D.V.); Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia (D.S.); Engelhardt Institute of Molecular Biology RAS, Moscow, Russia (A.A. Anashkina, A.A. Adzhubei); and Georgetown University Medical Center, Lombardi Comprehensive Cancer Center, Washington, DC (A.Ü).
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Flamm AG, Le Roux AL, Mateos B, Díaz-Lobo M, Storch B, Breuker K, Konrat R, Pons M, Coudevylle N. N-Lauroylation during the Expression of Recombinant N-Myristoylated Proteins: Implications and Solutions. Chembiochem 2016; 17:82-9. [PMID: 26522884 PMCID: PMC4736449 DOI: 10.1002/cbic.201500454] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Indexed: 12/12/2022]
Abstract
Incorporation of myristic acid onto the N terminus of a protein is a crucial modification that promotes membrane binding and correct localization of important components of signaling pathways. Recombinant expression of N-myristoylated proteins in Escherichia coli can be achieved by co-expressing yeast N-myristoyltransferase and supplementing the growth medium with myristic acid. However, undesired incorporation of the 12-carbon fatty acid lauric acid can also occur (leading to heterogeneous samples), especially when the available carbon sources are scarce, as it is the case in minimal medium for the expression of isotopically enriched samples. By applying this method to the brain acid soluble protein 1 and the 1-185 N-terminal region of c-Src, we show the significant, and protein-specific, differences in the membrane binding properties of lauroylated and myristoylated forms. We also present a robust strategy for obtaining lauryl-free samples of myristoylated proteins in both rich and minimal media.
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Affiliation(s)
- Andrea Gabriele Flamm
- Department of Computational and Structural Biology, F. Max Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Anabel-Lise Le Roux
- Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac 10-12, 08028, Barcelona, Spain
| | - Borja Mateos
- Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Baldiri Reixac 10-12, 08028, Barcelona, Spain
| | - Mireia Díaz-Lobo
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac 10-12, 08028, Barcelona, Spain
| | - Barbara Storch
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, CCB, Innrain 80/82, 6020, Innsbruck, Austria
| | - Kathrin Breuker
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, CCB, Innrain 80/82, 6020, Innsbruck, Austria
| | - Robert Konrat
- Department of Computational and Structural Biology, F. Max Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Miquel Pons
- Biomolecular NMR Laboratory, Department of Organic Chemistry, University of Barcelona, Baldiri Reixac 10-12, 08028, Barcelona, Spain
| | - Nicolas Coudevylle
- Department of Computational and Structural Biology, F. Max Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria.
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Pirrone GF, Emert-Sedlak LA, Wales TE, Smithgall TE, Kent MS, Engen JR. Membrane-Associated Conformation of HIV-1 Nef Investigated with Hydrogen Exchange Mass Spectrometry at a Langmuir Monolayer. Anal Chem 2015; 87:7030-5. [PMID: 26133569 PMCID: PMC4509969 DOI: 10.1021/acs.analchem.5b01725] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the companion paper to this work, we described development of a new type of hydrogen exchange (HX) mass spectrometry (MS) measurement that integrates Langmuir monolayers. With Langmuir monolayers, the lipid packing density can be reproducibly controlled and changed as desired. Analysis of HX in proteins that may undergo conformational changes as a function of lipid packing (for example, conformational rearrangements after insertion into a lipid layer) are then possible. We previously used neutron reflection to characterize just such a conformational change in the myristoylated HIV-1 Nef protein (myrNef): at high lipid packing density, myrNef could not insert into the lipids and maintained a compact conformation adjacent to the monolayer, whereas at lower lipid packing density, myrNef was able to insert N-terminal arm residues, causing displacement of the core domain away from the monolayer. In order to locate where conformation may have been altered by lipid association, we applied the HX MS Langmuir monolayer method to myrNef associated with monolayers of packing densities identical to those used for the prior neutron reflection measurements. The results show that the N-terminal region and the C-terminal unstructured loop undergo conformational changes when associated with a low density lipid monolayer. The results are not consistent with the hypothesis of myrNef dimerization upon membrane association in the absence of other myrNef binding partners. The HX MS Langmuir monolayer method provides new and meaningful information for myrNef that helps explain necessary conformational changes required for function at the membrane.
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Affiliation(s)
- Gregory F. Pirrone
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115
| | - Lori A. Emert-Sedlak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219
| | - Thomas E. Wales
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115
| | - Thomas E. Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219
| | - Michael S. Kent
- Bioenergy and Defense Technologies, Sandia National Laboratories, Albuquerque, NM 87185
| | - John R. Engen
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115
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13
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HIV-1 Myristoylated Nef Treatment of Murine Microglial Cells Activates Inducible Nitric Oxide Synthase, NO2 Production and Neurotoxic Activity. PLoS One 2015; 10:e0130189. [PMID: 26066624 PMCID: PMC4465743 DOI: 10.1371/journal.pone.0130189] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 05/17/2015] [Indexed: 12/21/2022] Open
Abstract
Background The potential role of the human immunodeficiency virus-1 (HIV-1) accessory protein Nef in the pathogenesis of neuroAIDS is still poorly understood. Nef is a molecular adapter that influences several cellular signal transduction events and membrane trafficking. In human macrophages, Nef expression induces the production of extracellular factors (e.g. pro-inflammatory chemokines and cytokines) and the recruitment of T cells, thus favoring their infection and its own transfer to uninfected cells via exosomes, cellular protrusions or cell-to-cell contacts. Murine cells are normally not permissive for HIV-1 but, in transgenic mice, Nef is a major disease determinant. Both in human and murine macrophages, myristoylated Nef (myr+Nef) treatment has been shown to activate NF-κB, MAP kinases and interferon responsive factor 3 (IRF-3), thereby inducing tyrosine phosphorylation of signal transducers and activator of transcription (STAT)-1, STAT-2 and STAT-3 through the production of proinflammatory factors. Methodology/Principal Findings We report that treatment of BV-2 murine microglial cells with myr+Nef leads to STAT-1, -2 and -3 tyrosine phosphorylation and upregulates the expression of inducible nitric oxide synthase (iNOS) with production of nitric oxide. We provide evidence that extracellular Nef regulates iNOS expression through NF-κB activation and, at least in part, interferon-β (IFNβ) release that acts in concert with Nef. All of these effects require both myristoylation and a highly conserved acidic cluster in the viral protein. Finally, we report that Nef induces the release of neurotoxic factors in the supernatants of microglial cells. Conclusions These results suggest a potential role of extracellular Nef in promoting neuronal injury in the murine model. They also indicate a possible interplay between Nef and host factors in the pathogenesis of neuroAIDS through the production of reactive nitrogen species in microglial cells.
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14
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Kumar S, Sharma RK. N-terminal region of the catalytic domain of human N-myristoyltransferase 1 acts as an inhibitory module. PLoS One 2015; 10:e0127661. [PMID: 26000639 PMCID: PMC4441422 DOI: 10.1371/journal.pone.0127661] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 04/17/2015] [Indexed: 11/18/2022] Open
Abstract
N-myristoyltransferase (NMT) plays critical roles in the modulation of various signaling molecules, however, the regulation of this enzyme in diverse cellular states remains poorly understood. We provide experimental evidence to show for the first time that for the isoform 1 of human NMT (hNMT1), the regulatory roles extend into the catalytic core. In our present study, we expressed, purified, and characterized a truncation mutant devoid of 28 N-terminal amino acids from the catalytic module (Δ28-hNMT1s) and compared its properties to the full-length catalytic domain of hNMT1. The deletion of the N-terminal peptide had no effect on the enzyme stability. Our findings suggest that the N-terminal region in the catalytic module of hNMT1 functions serves as a regulatory control element. The observations of an ~3 fold increase in enzymatic efficiency following removal of the N-terminal peptide of hNMT1s indicates that N-terminal amino acids acts as an inhibitory segment and negatively regulate the enzyme activity. Our findings that the N-terminal region confers control over activity, taken together with the earlier observations that the N-terminal of hNMT1 is differentially processed in diverse cellular states, suggests that the proteolytic processing of the peptide segment containing the inhibitory region provides a molecular mechanism for physiological up-regulation of myristoyltransferase activity.
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Affiliation(s)
- Sujeet Kumar
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Rajendra K. Sharma
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail: (RKS)
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15
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Monillas ES, Caplan JL, Thévenin AF, Bahnson BJ. Oligomeric state regulated trafficking of human platelet-activating factor acetylhydrolase type-II. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:469-75. [PMID: 25707358 DOI: 10.1016/j.bbapap.2015.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 02/06/2015] [Accepted: 02/12/2015] [Indexed: 01/19/2023]
Abstract
The intracellular enzyme platelet-activating factor acetylhydrolase type-II (PAFAH-II) hydrolyzes platelet-activating factor and oxidatively fragmented phospholipids. PAFAH-II in its resting state is mainly cytoplasmic, and it responds to oxidative stress by becoming increasingly bound to endoplasmic reticulum and Golgi membranes. Numerous studies have indicated that this enzyme is essential for protecting cells from oxidative stress induced apoptosis. However, the regulatory mechanism of the oxidative stress response by PAFAH-II has not been fully resolved. Here, changes to the oligomeric state of human PAFAH-II were investigated as a potential regulatory mechanism toward enzyme trafficking. Native PAGE analysis in vitro and photon counting histogram within live cells showed that PAFAH-II is both monomeric and dimeric. A Gly-2-Ala site-directed mutation of PAFAH-II demonstrated that the N-terminal myristoyl group is required for homodimerization. Additionally, the distribution of oligomeric PAFAH-II is distinct within the cell; homodimers of PAFAH-II were localized to the cytoplasm while monomers were associated to the membranes of the endoplasmic reticulum and Golgi. We propose that the oligomeric state of PAFAH-II drives functional protein trafficking. PAFAH-II localization to the membrane is critical for substrate acquisition and effective oxidative stress protection. It is hypothesized that the balance between monomer and dimer serves as a regulatory mechanism of a PAFAH-II oxidative stress response.
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Affiliation(s)
- Elizabeth S Monillas
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Jeffrey L Caplan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Anastasia F Thévenin
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Brian J Bahnson
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA.
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16
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Percario ZA, Ali M, Mangino G, Affabris E. Nef, the shuttling molecular adaptor of HIV, influences the cytokine network. Cytokine Growth Factor Rev 2014; 26:159-73. [PMID: 25529283 DOI: 10.1016/j.cytogfr.2014.11.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 11/05/2014] [Indexed: 12/17/2022]
Abstract
Several viruses manipulate host innate immune responses to avoid immune recognition and improve viral replication and spreading. The viral protein Nef of Human Immunodeficiency Virus is mainly involved in this "hijacking" activity and is a well established virulence factor. In the last few years there have been remarkable advances in outlining a defined framework of its functions. In particular Nef appears to be a shuttling molecular adaptor able to exert its effects both on infected and non infected bystander cell. In addition it is emerging fact that it has an important impact on the chemo-cytokine network. Nef protein represents an interesting new target to develop therapeutic drugs for treatment of seropositive patients. In this review we have tried to provide a unifying view of the multiple functions of this viral protein on the basis of recently available experimental data.
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Affiliation(s)
| | - Muhammad Ali
- Department of Sciences, University Roma Tre, Rome, Italy
| | - Giorgio Mangino
- Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Italy
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17
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Basmaciogullari S, Pizzato M. The activity of Nef on HIV-1 infectivity. Front Microbiol 2014; 5:232. [PMID: 24904546 PMCID: PMC4033043 DOI: 10.3389/fmicb.2014.00232] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 04/30/2014] [Indexed: 12/29/2022] Open
Abstract
The replication and pathogenicity of lentiviruses is crucially modulated by “auxiliary proteins” which are expressed in addition to the canonical retroviral ORFs gag, pol, and env. Strategies to inhibit the activity of such proteins are often sought and proposed as possible additions to increase efficacy of the traditional antiretroviral therapy. This requires the acquisition of an in-depth knowledge of the molecular mechanisms underlying their function. The Nef auxiliary protein is expressed uniquely by primate lentiviruses and plays an important role in virus replication in vivo and in the onset of AIDS. Among its several activities Nef enhances the intrinsic infectivity of progeny virions through a mechanism which remains today enigmatic. Here we review the current knowledge surrounding such activity and we discuss its possible role in HIV biology.
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Affiliation(s)
- Stéphane Basmaciogullari
- Hôpital Necker-Enfants Malades, Sorbonne Paris Cité, Université Paris Descartes Paris, France ; INSERM U845 Paris, France
| | - Massimo Pizzato
- Centre for Integrative Biology, University of Trento Trento, Italy
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18
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Cui HL, Ditiatkovski M, Kesani R, Bobryshev YV, Liu Y, Geyer M, Mukhamedova N, Bukrinsky M, Sviridov D. HIV protein Nef causes dyslipidemia and formation of foam cells in mouse models of atherosclerosis. FASEB J 2014; 28:2828-39. [PMID: 24642731 DOI: 10.1096/fj.13-246876] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Patients with HIV are at an increased risk of cardiovascular disease. In this study we investigated the effect of Nef, a secreted HIV protein responsible for the impairment of cholesterol efflux, on the development of atherosclerosis in two animal models. ApoE(-/-) mice fed a high-fat diet and C57BL/6 mice fed a high-fat, high-cholesterol diet were injected with recombinant Nef (40 ng/injection) or vehicle, and the effects of Nef on development of atherosclerosis, inflammation, and dyslipidemia were assessed. In apoE(-/-) mice, Nef significantly increased the size of atherosclerotic lesions and caused vessel remodeling. Nef caused elevation of total cholesterol and triglyceride levels in the plasma while reducing high-density lipoprotein cholesterol levels. These changes were accompanied by a reduction of ABCA1 abundance in the liver, but not in the vessels. In C57BL/6 mice, Nef caused a significant number of lipid-laden macrophages presented in adventitia of the vessels; these cells were absent from the vessels of control mice. Nef caused sharp elevations of plasma triglyceride levels and body weight. Taken together, our findings suggest that Nef causes dyslipidemia and accumulation of cholesterol in macrophages within the vessel wall, supporting the role of Nef in pathogenesis of atherosclerosis in HIV-infected patients.-Cui, H. L., Ditiatkovski, M., Kesani, R., Bobryshev, Y. V., Liu, Y., Geyer, M., Mukhamedova, N., Bukrinsky, M., Sviridov, D. HIV protein Nef causes dyslipidemia and formation of foam cells in mouse models of atherosclerosis.
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Affiliation(s)
- Huanhuan L Cui
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | | | - Rajitha Kesani
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Yuri V Bobryshev
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Yingying Liu
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Matthias Geyer
- Center for Advanced European Studies and Research (CAESAR), Bonn, Germany; and
| | | | - Michael Bukrinsky
- Department of Microbiology, Immunology, and Tropical Medicine, George Washington University, Washington, District of Columbia, USA
| | - Dmitri Sviridov
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia;
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19
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Lülf S, Matz J, Rouyez MC, Järviluoma A, Saksela K, Benichou S, Geyer M. Structural basis for the inhibition of HIV-1 Nef by a high-affinity binding single-domain antibody. Retrovirology 2014; 11:24. [PMID: 24620746 PMCID: PMC4007562 DOI: 10.1186/1742-4690-11-24] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Accepted: 03/04/2014] [Indexed: 04/01/2023] Open
Abstract
Background The HIV-1 Nef protein is essential for AIDS pathogenesis by its interaction with host cell surface receptors and signaling factors. Despite its critical role as a virulence factor Nef is not targeted by current antiviral strategies. Results We have determined the crystal structure of the complex formed by a camelid single-domain antibody fragment, termed sdAb19, bound to HIV-1 Nef together with a stabilizing SH3 domain. sdAb19 forms a stoichiometric 1:1 complex with Nef and binds to a conformationally conserved surface at the C-terminus of Nef that overlaps with functionally important interaction sites involved in Nef-induced perturbations of signaling and trafficking pathways. The antibody fragment binds Nef with low nanomolar affinity, which could be attenuated to micromolar affinity range by site-directed mutagenesis of key interaction residues in sdAb19. Fusion of the SH3 domain to sdAb19, termed Neffin, leads to a significantly increased affinity for Nef and formation of a stoichiometric 2:2 Nef–Neffin complex. The 19 kDa Neffin protein inhibits all functions of Nef as CD4 and MHC-I downregulation, association with Pak2, and the increase in virus infectivity and replication. Conclusions Together, sdAb19 and Neffin thus represent efficient tools for the rational development of antiviral strategies against HIV-1 Nef.
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Affiliation(s)
| | | | | | | | | | | | - Matthias Geyer
- Center of Advanced European Studies and Research, Group Physical Biochemistry, Bonn, Germany.
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20
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Chandrasekaran P, Moore V, Buckley M, Spurrier J, Kehrl JH, Venkatesan S. HIV-1 Nef down-modulates C-C and C-X-C chemokine receptors via ubiquitin and ubiquitin-independent mechanism. PLoS One 2014; 9:e86998. [PMID: 24489825 PMCID: PMC3906104 DOI: 10.1371/journal.pone.0086998] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 12/16/2013] [Indexed: 12/29/2022] Open
Abstract
Human and Simian Immunodeficiency virus (HIV-1, HIV-2, and SIV) encode an accessory protein, Nef, which is a pathogenesis and virulence factor. Nef is a multivalent adapter that dysregulates the trafficking of many immune cell receptors, including chemokine receptors (CKRs). Physiological endocytic itinerary of agonist occupied CXCR4 involves ubiquitinylation of the phosphorylated receptor at three critical lysine residues and dynamin-dependent trafficking through the ESCRT pathway into lysosomes for degradation. Likewise, Nef induced CXCR4 degradation was critically dependent on the three lysines in the C-terminal -SSLKILSKGK- motif. Nef directly recruits the HECT domain E3 ligases AIP4 or NEDD4 to CXCR4 in the resting state. This mechanism was confirmed by ternary interactions of Nef, CXCR4 and AIP4 or NEDD4; by reversal of Nef effect by expression of catalytically inactive AIP4-C830A mutant; and siRNA knockdown of AIP4, NEDD4 or some ESCRT-0 adapters. However, ubiquitinylation dependent lysosomal degradation was not the only mechanism by which Nef downregulated CKRs. Agonist and Nef mediated CXCR2 (and CXCR1) degradation was ubiquitinylation independent. Nef also profoundly downregulated the naturally truncated CXCR4 associated with WHIM syndrome and engineered variants of CXCR4 that resist CXCL12 induced internalization via an ubiquitinylation independent mechanism.
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Affiliation(s)
- Prabha Chandrasekaran
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Victoria Moore
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Monica Buckley
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Joshua Spurrier
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - John H. Kehrl
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sundararajan Venkatesan
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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21
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Hochkoeppler A. Expanding the landscape of recombinant protein production in Escherichia coli. Biotechnol Lett 2013; 35:1971-81. [DOI: 10.1007/s10529-013-1396-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/26/2013] [Indexed: 12/11/2022]
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22
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Akgun B, Satija S, Nanda H, Pirrone GF, Shi X, Engen JR, Kent MS. Conformational transition of membrane-associated terminally acylated HIV-1 Nef. Structure 2013; 21:1822-33. [PMID: 24035710 DOI: 10.1016/j.str.2013.08.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 07/08/2013] [Accepted: 08/02/2013] [Indexed: 01/26/2023]
Abstract
Many proteins are posttranslationally modified by acylation targeting them to lipid membranes. While methods such as X-ray crystallography and nuclear magnetic resonance are available to determine the structure of folded proteins in solution, the precise position of folded domains relative to a membrane remains largely unknown. We used neutron and X-ray reflection methods to measure the displacement of the core domain of HIV Nef from lipid membranes upon insertion of the N-terminal myristate group. Nef is one of several HIV-1 accessory proteins and an essential factor in AIDS progression. Upon insertion of the myristate and residues from the N-terminal arm, Nef transitions from a closed-to-open conformation that positions the core domain 70 Å from the lipid headgroups. This work rules out previous speculation that the Nef core remains closely associated with the membrane to optimize interactions with the cytoplasmic domain of MHC-1.
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Affiliation(s)
- Bulent Akgun
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA; Department of Chemistry, Boğaziçi University, Bebek 34342, Istanbul, Turkey
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23
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Breuer S, Espinola S, Morelli X, Torbett BE, Arold ST, Engels IH. A Biochemical/Biophysical Assay Dyad for HTS-Compatible Triaging of Inhibitors of the HIV-1 Nef/Hck SH3 Interaction. Curr Chem Genom Transl Med 2013; 7:16-20. [PMID: 24396731 PMCID: PMC3854662 DOI: 10.2174/2213988501307010016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 05/09/2013] [Accepted: 05/20/2013] [Indexed: 11/25/2022] Open
Abstract
The current treatment regimens for HIV include over 20 anti-retrovirals. However, adverse drug effects and the emergence of drug resistance necessitates the continued improvement of the existing drug classes as well as the development of novel drugs that target as yet therapeutically unexploited viral and cellular pathways. Here we demonstrate a strategy for the discovery of protein-protein interaction inhibitors of the viral pathogenicity factor HIV-1 Nef and its interaction with the host factor SH3. A combination of a time-resolved fluorescence resonance energy resonance energy transfer-based assay and a label-free resonant waveguide grating-based assay was optimized for high-throughput screening formats.
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Affiliation(s)
- Sebastian Breuer
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Sheryll Espinola
- Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Dr, San Diego, CA 92121, USA
| | - Xavier Morelli
- CRCM, CNRS UMR7258, Laboratory of Integrative Structural and Chemical Biology (ISCB); INSERM, U1068; Institut Paoli-Calmettes; Aix-Marseille Université, UM105, F-13009, Marseille, France
| | - Bruce E Torbett
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Stefan T Arold
- Department of Biochemistry and Molecular Biology, Unit 1000, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA ; King Abdullah University of Science and Technology (KAUST), Division of Biological and Environmental Sciencesand Engineering, Computational Bioscience Research Center, Thuwal 23955-6900, Saudi Arabia
| | - Ingo H Engels
- Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Dr, San Diego, CA 92121, USA
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24
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Mangino G, Serra V, Borghi P, Percario ZA, Horenkamp FA, Geyer M, Affabris E. Exogenous nef induces proinflammatory signaling events in murine macrophages. Viral Immunol 2012; 25:117-30. [PMID: 22413916 DOI: 10.1089/vim.2011.0082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Despite the fact that murine cells are not permissive for human immunodeficiency virus type 1 (HIV-1) infection, several investigators have constructed transgenic (Tg) mice to model HIV-1-induced diseases to overcome this restriction. The generation of Tg mice expressing selected HIV-1 genes revealed that Nef harbors a major disease determinant. HIV-1 Nef protein is a molecular adapter able to interact with several cellular partners, interfering with cellular functions. The phenotype of Nef Tg mice was extensively characterized regarding in vivo development of AIDS-like disease and the effects of Nef expression in T lymphocytes, but the functions eventually corrupted by Nef in monocytes and macrophages were less studied. Nef treatment of human monocyte-derived macrophages induces the internalization of the protein and modulates the production and secretion of different chemokines and cytokines by activating specific intracellular signaling pathways (i.e., NF-κB, MAPK, and IRF3). Therefore we set up an in vitro murine macrophage-based model using stabilized cell lines and primary peritoneal macrophages, and treated them with recombinant myristoylated Nef(SF2) (recNef). Like human cells, murine macrophages responded to Nef treatment, activating IKK-α and IKK-β, JNK, and p38 MAP kinases. Activation of the NF-κB pathway is mandatory for the synthesis and release of a pool of cytokines and chemokines, including IFN-β, that induce tyrosine phosphorylation of the signal transducer and activator of transcription (STAT)-1, STAT-2, and STAT-3, in an autocrine and paracrine manner, confirming that murine macrophages respond to Nef similarly to human ones. These data extend the results previously obtained in human primary macrophages, allowing the use of murine cells in culture to study signaling events modulated by Nef in myeloid-derived cells. In particular, it may be feasible to use macrophages derived from mice knocked out in specific signaling intermediates to obtain greater insight into the mechanism of Nef-induced effects.
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25
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Eisenhaber B, Sammer M, Lua WH, Benetka W, Liew LL, Yu W, Lee HK, Koranda M, Eisenhaber F, Adhikari S. Nuclear import of a lipid-modified transcription factor: mobilization of NFAT5 isoform a by osmotic stress. Cell Cycle 2011; 10:3897-911. [PMID: 22071693 DOI: 10.4161/cc.10.22.18043] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Lipid-modified transcription factors (TFs) are biomolecular oddities since their reduced mobility and membrane attachment appear to contradict nuclear import required for their gene-regulatory function. NFAT5 isoform a (selected from an in silico screen for predicted lipid-modified TFs) is shown to contribute about half of all endogenous expression of human NFAT5 isoforms in the isotonic state. Wild-type NFAT5a protein is indeed myristoylated and palmitoylated on its transport to the plasmalemma via the endoplasmic reticulum and the Golgi. In contrast, its lipid anchor-deficient mutants as well as isoforms NFAT5b/c are diffusely localized in the cytoplasm without preference to vesicular structures. Quantitative/live microscopy shows the plasmamembrane-bound fraction of NFAT5a moving into the nucleus upon osmotic stress despite the lipid anchoring. The mobilization mechanism is not based on proteolytic processing of the lipid-anchored N-terminus but appears to involve reversible palmitoylation. Thus, NFAT5a is an example of TFs immobilized with lipid anchors at cyotoplasmic membranes in the resting state and that, nevertheless, can translocate into the nucleus upon signal induction.
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26
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Lugari A, Breuer S, Coursindel T, Opi S, Restouin A, Shi X, Nazabal A, Torbett BE, Martinez J, Collette Y, Parrot I, Arold ST, Morelli X. A specific protein disorder catalyzer of HIV-1 Nef. Bioorg Med Chem 2011; 19:7401-6. [PMID: 22061824 DOI: 10.1016/j.bmc.2011.10.051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 10/11/2011] [Accepted: 10/17/2011] [Indexed: 11/29/2022]
Abstract
The HIV-1 auxiliary protein Nef is required for the onset and progression of AIDS in HIV-1-infected persons. Here, we have deciphered the mode of action of a second-generation inhibitor of Nef, DLC27-14, presenting a competitive IC(50) of ∼16 μM measured by MALDI-TOF experiments. Thermal protein denaturation experiments revealed a negative effect on stability of Nef in the presence of a saturating concentration of the inhibitor. The destabilizing action of DLC27-14 was confirmed by a HIV protease-based experiment, in which the protease sensitivity of DLC27-14-bound Nef was three times as high as that of apo Nef. The only compatible docking modes of action for DLC27-14 suggest that DLC27-14 promotes an opening of two α-helices that would destabilize the Nef core domain. DLC27-14 thus acts as a specific protein disorder catalyzer that destabilizes the folded conformation of the protein. Our results open novel avenues toward the development of next-generation Nef inhibitors.
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Affiliation(s)
- Adrien Lugari
- IMR Laboratory, CNRS-UPR 3243, Centre National de Recherche Scientifique, Institut de Microbiologie de Méditerranée and Aix-Marseille Universités, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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HIV-1 Nef induces proinflammatory state in macrophages through its acidic cluster domain: involvement of TNF alpha receptor associated factor 2. PLoS One 2011; 6:e22982. [PMID: 21886773 PMCID: PMC3160284 DOI: 10.1371/journal.pone.0022982] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 07/11/2011] [Indexed: 01/06/2023] Open
Abstract
Background HIV-1 Nef is a virulence factor that plays multiple roles during HIV replication. Recently, it has been described that Nef intersects the CD40 signalling in macrophages, leading to modification in the pattern of secreted factors that appear able to recruit, activate and render T lymphocytes susceptible to HIV infection. The engagement of CD40 by CD40L induces the activation of different signalling cascades that require the recruitment of specific tumor necrosis factor receptor-associated factors (i.e. TRAFs). We hypothesized that TRAFs might be involved in the rapid activation of NF-κB, MAPKs and IRF-3 that were previously described in Nef-treated macrophages to induce the synthesis and secretion of proinflammatory cytokines, chemokines and IFNβ to activate STAT1, -2 and -3. Methodology/Principal Findings Searching for possible TRAF binding sites on Nef, we found a TRAF2 consensus binding site in the AQEEEE sequence encompassing the conserved four-glutamate acidic cluster. Here we show that all the signalling effects we observed in Nef treated macrophages depend on the integrity of the acidic cluster. In addition, Nef was able to interact in vitro with TRAF2, but not TRAF6, and this interaction involved the acidic cluster. Finally silencing experiments in THP-1 monocytic cells indicate that both TRAF2 and, surprisingly, TRAF6 are required for the Nef-induced tyrosine phosphorylation of STAT1 and STAT2. Conclusions Results reported here revealed TRAF2 as a new possible cellular interactor of Nef and highlighted that in monocytes/macrophages this viral protein is able to manipulate both the TRAF/NF-κB and TRAF/IRF-3 signalling axes, thereby inducing the synthesis of proinflammatory cytokines and chemokines as well as IFNβ.
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Breuer S, Schievink SI, Schulte A, Blankenfeldt W, Fackler OT, Geyer M. Molecular design, functional characterization and structural basis of a protein inhibitor against the HIV-1 pathogenicity factor Nef. PLoS One 2011; 6:e20033. [PMID: 21625496 PMCID: PMC3098852 DOI: 10.1371/journal.pone.0020033] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 04/10/2011] [Indexed: 12/31/2022] Open
Abstract
Increased spread of HIV-1 and rapid emergence of drug resistance warrants development of novel antiviral strategies. Nef, a critical viral pathogenicity factor that interacts with host cell factors but lacks enzymatic activity, is not targeted by current antiviral measures. Here we inhibit Nef function by simultaneously blocking several highly conserved protein interaction surfaces. This strategy, referred to as “wrapping Nef”, is based on structure-function analyses that led to the identification of four target sites: (i) SH3 domain interaction, (ii) interference with protein transport processes, (iii) CD4 binding and (iv) targeting to lipid membranes. Screening combinations of Nef-interacting domains, we developed a series of small Nef interacting proteins (NIs) composed of an SH3 domain optimized for binding to Nef, fused to a sequence motif of the CD4 cytoplasmic tail and combined with a prenylation signal for membrane association. NIs bind to Nef in the low nM affinity range, associate with Nef in human cells and specifically interfere with key biological activities of Nef. Structure determination of the Nef-inhibitor complex reveals the molecular basis for binding specificity. These results establish Nef-NI interfaces as promising leads for the development of potent Nef inhibitors.
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Affiliation(s)
- Sebastian Breuer
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany
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Horenkamp FA, Breuer S, Schulte A, Lülf S, Weyand M, Saksela K, Geyer M. Conformation of the dileucine-based sorting motif in HIV-1 Nef revealed by intermolecular domain assembly. Traffic 2011; 12:867-77. [PMID: 21477083 DOI: 10.1111/j.1600-0854.2011.01205.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The human immunodeficiency virus 1 (HIV-1) Nef protein is a pathogenicity factor required for effective progression to AIDS, which modulates host cell signaling pathways and T-cell receptor internalization. We have determined the crystal structure of Nef, allele SF2, in complex with an engineered SH3 domain of human Hck showing unnaturally tight binding and inhibitory potential toward Nef. This complex provides the most complete Nef structure described today, and explains the structural basis of the high affinity of this interaction. Intriguingly, the 33-residue C-terminal flexible loop is resolved in the structure by its interactions with a highly conserved hydrophobic groove on the core domain of an adjacent Nef molecule. The loop mediates the interaction of Nef with the cellular adaptor protein machinery for the stimulated internalization of surface receptors. The endocytic dileucine-based sorting motif is exposed at the tip of the acidic loop, giving the myristoylated Nef protein a distinctly dipolar character. The intermolecular domain assembly of Nef provides insights into a possible regulation mechanism for cargo trafficking.
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Affiliation(s)
- Florian A Horenkamp
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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30
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Abstract
The HIV-1 accessory protein Nef is N-terminally myristoylated, and this post-translational modification is essential for Nef function in AIDS progression. Transfer of a myristate group from myristoyl coenzyme A to Nef occurs cotranslationally and is catalyzed by human N-myristoyltransferase 1 (NMT). To investigate the conformational effects of myristoylation on Nef structure as well as to probe the nature of the Nef:NMT complex, we investigated various forms of Nef with hydrogen exchange mass spectrometry. Conformational changes in Nef were not detected as a result of myristoylation, and NMT had no effect on deuterium uptake by Nef in a myrNef:NMT complex. However, myrNef binding did have an effect on NMT deuterium uptake. Major HX differences in NMT were primarily located around the active site, with more subtle differences, at the longer time points, across the structure. At the shortest time point, significant differences between the two states were observed in two regions which interact strongly with the phosphate groups of coenzyme A. On the basis of our results, we propose a model of the Nef:NMT complex in which only the myristoyl moiety holds the two proteins together in complex and speculate that perhaps NMT chaperones Nef to the membrane and thereby protects the myristic acid group from the cytosol rather than Nef operating through a myristoyl switch mechanism.
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Affiliation(s)
- Christopher R. Morgan
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
| | - Brian V. Miglionico
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
| | - John R. Engen
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
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Dames SA, Schönichen A, Geyer M. 1H, 15N, and 13C assignments of the N-terminal activation domain of Dictyostelium discoideum Formin C. BIOMOLECULAR NMR ASSIGNMENTS 2011; 5:47-49. [PMID: 20927614 DOI: 10.1007/s12104-010-9264-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 09/22/2010] [Indexed: 05/30/2023]
Abstract
Dictyostelium discoideum Formin C (ForC) plays an important role in the fruiting body formation during the multicellular stages of the slime mold. Formins are multidomain proteins that are known to regulate the actin cytoskeleton. Here, we report the assignments of the (1)H, (15)N, and (13)C nuclei of the N-terminal activation domain (residues 1-100) of ForC. Chemical shifts have been deposited at the BioMagResBank under the BMRB accession number 17,029. The N-terminal region of the 131 kDa ForC protein is supposed to form a GTPase-binding domain required for activation of the formin.
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Affiliation(s)
- Sonja A Dames
- Department of Chemistry, Biomolecular NMR Spectroscopy, Technische Universität München, Garching, Germany.
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32
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Kent MS, Murton JK, Sasaki DY, Satija S, Akgun B, Nanda H, Curtis JE, Majewski J, Morgan CR, Engen JR. Neutron reflectometry study of the conformation of HIV Nef bound to lipid membranes. Biophys J 2011; 99:1940-8. [PMID: 20858440 DOI: 10.1016/j.bpj.2010.07.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 06/16/2010] [Accepted: 07/06/2010] [Indexed: 01/04/2023] Open
Abstract
Nef is an HIV-1 accessory protein that directly contributes to AIDS progression. Nef is myristoylated on the N-terminus, associates with membranes, and may undergo a transition from a solution conformation to a membrane-associated conformation. It has been hypothesized that conformational rearrangement enables membrane-associated Nef to interact with cellular proteins. Despite its medical relevance, to our knowledge there is no direct information about the conformation of membrane-bound Nef. In this work, we used neutron reflection to reveal what we believe are the first details of the conformation of membrane-bound Nef. The conformation of Nef was probed upon binding to Langmuir monolayers through the interaction of an N-terminal His tag with a synthetic metal-chelating lipid, which models one of the possible limiting cases for myr-Nef. The data indicate that residues are inserted into the lipid headgroups during interaction, and that the core domain lies directly against the lipid headgroups, with a thickness of ∼40 A. Binding of Nef through the N-terminal His tag apparently facilitates insertion of residues, as no insertion occurred upon binding of Nef through weak electrostatic interactions in the absence of the specific interaction through the His tag.
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Affiliation(s)
- Michael S Kent
- Sandia National Laboratories, Albuquerque, New Mexico, USA.
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Gvritishvili AG, Leung KW, Tombran-Tink J. Codon preference optimization increases heterologous PEDF expression. PLoS One 2010; 5:e15056. [PMID: 21152082 PMCID: PMC2994832 DOI: 10.1371/journal.pone.0015056] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2010] [Accepted: 10/04/2010] [Indexed: 12/26/2022] Open
Abstract
Pigment epithelium-derived factor (PEDF) is widely known for its neurotrophic and antiangiogenic functions. Efficacy studies of PEDF in animal models are limited because of poor heterologous protein yields. Here, we redesigned the human PEDF gene to preferentially match codon frequencies of E coli without altering the amino acid sequence. Following de novo synthesis, codon optimized PEDF (coPEDF) and the wtPEDF genes were cloned into pET32a containing a 5′ thioredoxin sequence (Trx) and the recombinant Trx-coPEDF or Trx-wtPEDF fusion constructs expressed in native and two tRNA augmented E coli hosts - BL21-CodonPlus(DE3)-RIL and BL21-CodonPlus(DE3)-RP, carrying extra copies of tRNAarg,ile,leu and tRNAarg,pro genes , respectively. Trx-PEDF fusion proteins were isolated using Ni-NTA metal affinity chromatography and PEDF purified after cleavage with factor Xα. Protein purity and identity were confirmed by western blot, MALDI-TOF, and UV/CD spectral analyses. Expression of the synthetic gene was ∼3.4 fold greater (212.7 mg/g; 62.1 mg/g wet cells) and purified yields ∼4 fold greater (41.1 mg/g; 11.3 mg/g wet cell) than wtPEDF in the native host. A small increase in expression of both genes was observed in hosts supplemented with rare tRNA genes compared to the native host but expression of coPEDF was ∼3 fold greater than wtPEDF in both native and codon-bias-adjusted E coli strains. ΔGs at −3 to +50 of the Trx site of both fusion genes were −3.9 kcal/mol. Functionally, coPEDF was equally as effective as wtPEDF in reducing oxidative stress, promoting neurite outgrowth, and blocking endothelial tube formation. These findings suggest that while rare tRNA augmentation and mRNA folding energies can significantly contribute to increased protein expression, preferred codon usage, in this case, is advantageous to translational efficiency of biologically active PEDF in E coli. This strategy will undoubtedly fast forward studies to validate therapeutic utility of PEDF in vivo.
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Affiliation(s)
- Anzor G. Gvritishvili
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Kar Wah Leung
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Joyce Tombran-Tink
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania, United States of America
- Department of Ophthalmology, Penn State University College of Medicine, Hershey, Pennsylvania, United States of America
- * E-mail:
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Kwak YT, Raney A, Kuo LS, Denial SJ, Temple BRS, Garcia JV, Foster JL. Self-association of the Lentivirus protein, Nef. Retrovirology 2010; 7:77. [PMID: 20863404 PMCID: PMC2955668 DOI: 10.1186/1742-4690-7-77] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 09/23/2010] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND The HIV-1 pathogenic factor, Nef, is a multifunctional protein present in the cytosol and on membranes of infected cells. It has been proposed that a spatial and temporal regulation of the conformation of Nef sequentially matches Nef's multiple functions to the process of virion production. Further, it has been suggested that dimerization is required for multiple Nef activities. A dimerization interface has been proposed based on intermolecular contacts between Nefs within hexagonal Nef/FynSH3 crystals. The proposed dimerization interface consists of the hydrophobic B-helix and flanking salt bridges between R105 and D123. Here, we test whether Nef self-association is mediated by this interface and address the overall significance of oligomerization. RESULTS By co-immunoprecipitation assays, we demonstrated that HIV-1Nef exists as monomers and oligomers with about half of the Nef protomers oligomerized. Nef oligomers were found to be present in the cytosol and on membranes. Removal of the myristate did not enhance the oligomerization of soluble Nef. Also, SIVNef oligomerizes despite lacking a dimerization interface functionally homologous to that proposed for HIV-1Nef. Moreover, HIV-1Nef and SIVNef form hetero-oligomers demonstrating the existence of homologous oligomerization interfaces that are distinct from that previously proposed (R105-D123). Intracellular cross-linking by formaldehyde confirmed that SF2Nef dimers are present in intact cells, but surprisingly self-association was dependent on R105, but not D123. SIV(MAC239)Nef can be cross-linked at its only cysteine, C55, and SF2Nef is also cross-linked, but at C206 instead of C55, suggesting that Nefs exhibit multiple dimeric structures. ClusPro dimerization analysis of HIV-1Nef homodimers and HIV-1Nef/SIVNef heterodimers identified a new potential dimerization interface, including a dibasic motif at R105-R106 and a six amino acid hydrophobic surface. CONCLUSIONS We have demonstrated significant levels of intracellular Nef oligomers by immunoprecipitation from cellular extracts. However, our results are contrary to the identification of salt bridges between R105 and D123 as necessary for self-association. Importantly, binding between HIV-1Nef and SIVNef demonstrates evolutionary conservation and therefore significant function(s) for oligomerization. Based on modeling studies of Nef self-association, we propose a new dimerization interface. Finally, our findings support a stochastic model of Nef function with a dispersed intracellular distribution of Nef oligomers.
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Affiliation(s)
- Youn Tae Kwak
- Baylor Institute for Immunology Research, 3434 Live Oak, Dallas, TX 75204, USA
| | - Alexa Raney
- Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Y9.206, Dallas, Texas 75390, USA
| | - Lillian S Kuo
- Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Y9.206, Dallas, Texas 75390, USA
| | - Sarah J Denial
- Division of Infectious Diseases, Center for AIDS Research, University of North Carolina, Chapel Hill, North Carolina 27599-7042, USA
| | - Brenda RS Temple
- Department of Biochemistry and Biophysics, R. L. Juliano Structural Bioinformatics Core, University of North Carolina, Chapel Hill, North Carolina 27599-7042, USA
| | - J Victor Garcia
- Division of Infectious Diseases, Center for AIDS Research, University of North Carolina, Chapel Hill, North Carolina 27599-7042, USA
| | - John L Foster
- Division of Infectious Diseases, Center for AIDS Research, University of North Carolina, Chapel Hill, North Carolina 27599-7042, USA
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Schönichen A, Bigalke JM, Urbanke C, Grzesiek S, Dames SA, Geyer M. A flexible bipartite coiled coil structure is required for the interaction of Hexim1 with the P-TEFB subunit cyclin T1. Biochemistry 2010; 49:3083-91. [PMID: 20210365 DOI: 10.1021/bi902072f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transcription elongation is regulated by the cellular protein Hexim1, which inhibits phosphorylation of RNA polymerase II by interacting with the positive transcription elongation factor P-TEFb. Hexim1 binds directly to Cyclin T1 of P-TEFb with its coiled coil domain that is subdivided into a highly polar N-terminal segment containing nonconservative residues in the dimer interface and a C-terminal segment with an evolutionarily conserved sequence composition. Here we show that the noncanonical sequence composition of the first coiled coil segment is required for the interaction with Cyclin T1 while the second segment keeps the Cyclin T-binding domain dimeric upon binding. Both coiled coil segments exhibit distinct melting points as shown by heat denaturation experiments using circular dichroism spectroscopy. Deletion of the central stammer motif (Delta316-318) leads to a single denaturation reaction, suggesting formation of a continuous coiled coil. Mutation of noncanonical coiled coil residues K284 and Y291 to valines in the dimer interface of the first segment only slightly increases its stability. Concomitantly, deletion of the stammer but not the double point mutation led to a reduced affinity for Cyclin T1 as shown by isothermal titration calorimetry. Moreover, Cyclin T1 bound Hexim1 with a 1:2 stoichiometry, whereas truncation of the C-terminal coiled coil led to formation of an equimolar complex. These observations suggest that binding to Cyclin T1 induces an asymmetry or sterical hindrance in the first coiled coil segment of dimeric Hexim1 that disallows formation of a 2:2 complex as further supported by analytical ultracentrifugation and cross-linking experiments.
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Affiliation(s)
- André Schönichen
- Max-Planck-Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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Glück JM, Hoffmann S, Koenig BW, Willbold D. Single vector system for efficient N-myristoylation of recombinant proteins in E. coli. PLoS One 2010; 5:e10081. [PMID: 20404920 PMCID: PMC2852408 DOI: 10.1371/journal.pone.0010081] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 03/17/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND N-myristoylation is a crucial covalent modification of numerous eukaryotic and viral proteins that is catalyzed by N-myristoyltransferase (NMT). Prokaryotes are lacking endogenous NMT activity. Recombinant production of N-myristoylated proteins in E. coli cells can be achieved by coexpression of heterologous NMT with the target protein. In the past, dual plasmid systems were used for this purpose. METHODOLOGY/PRINCIPAL FINDINGS Here we describe a single vector system for efficient coexpression of substrate and enzyme suitable for production of co- or posttranslationally modified proteins. The approach was validated using the HIV-1 Nef protein as an example. A simple and efficient protocol for production of highly pure and completely N-myristoylated Nef is presented. The yield is about 20 mg myristoylated Nef per liter growth medium. CONCLUSIONS/SIGNIFICANCE The single vector strategy allows diverse modifications of target proteins recombinantly coexpressed in E. coli with heterologous enzymes. The method is generally applicable and provides large amounts of quantitatively processed target protein that are sufficient for comprehensive biophysical and structural studies.
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Affiliation(s)
- Julian M. Glück
- Institute of Structural Biology and Biophysics, Research Centre Jülich, Jülich, Germany
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Silke Hoffmann
- Institute of Structural Biology and Biophysics, Research Centre Jülich, Jülich, Germany
| | - Bernd W. Koenig
- Institute of Structural Biology and Biophysics, Research Centre Jülich, Jülich, Germany
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Dieter Willbold
- Institute of Structural Biology and Biophysics, Research Centre Jülich, Jülich, Germany
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
- * E-mail:
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HIV-1 Nef membrane association depends on charge, curvature, composition and sequence. Nat Chem Biol 2009; 6:46-53. [PMID: 19935658 DOI: 10.1038/nchembio.268] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 10/01/2009] [Indexed: 12/30/2022]
Abstract
Nef-mediated internalization of T-cell receptor molecules from the surface of an infected cell is required for the pathogenicity of HIV and disease progression to AIDS. This function depends on the N-terminal myristoylation of Nef, a lipid modification that targets the protein to membranes. We have analyzed how specific membrane properties and sequence motifs within Nef determine this interaction. Using time-resolved techniques we find that the association with membranes is a biphasic process with a fast rate for an electrostatic-driven protein-liposome interaction and a slow rate for the formation of an amphipathic helix. The rate of myristate insertion into liposomes depends on membrane curvature, while changes in the lipid composition with respect to phosphoinositides, cholesterol or sphingomyelin did not significantly alter the interaction. Moreover, Nef binding to membranes requires negatively charged liposomes, and mutations of basic and hydrophobic residues strongly diminished the association and changed the binding kinetics differently.
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Czudnochowski N, Vollmuth F, Baumann S, Vogel-Bachmayr K, Geyer M. Specificity of Hexim1 and Hexim2 complex formation with cyclin T1/T2, importin alpha and 7SK snRNA. J Mol Biol 2009; 395:28-41. [PMID: 19883659 DOI: 10.1016/j.jmb.2009.10.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 10/26/2009] [Accepted: 10/27/2009] [Indexed: 10/20/2022]
Abstract
Positive transcription elongation factor b (P-TEFb) stimulates the transition from transcription initiation to productive elongation by phosphorylation of the C-terminal domain of RNA polymerase II. P-TEFb consists of the cyclin-dependent kinase Cdk9 and a T-type cyclin and is regulated by the small nuclear RNA 7SK and the coupling protein Hexim1 or Hexim2. In this study, we analyzed the tripartite protein-RNA complex formation between Hexim, Cyclin T and 7SK snRNA. Using isothermal titration calorimetry, we observed higher affinities for Cyclin T1-Hexim1 and Cyclin T2-Hexim2 complex formations compared with the interactions in reverse. Importin alpha, which is part of the Ran-mediated nuclear import pathway, bound Hexim1 and Hexim2 with dissociation constants of 2.0 and 0.5 muM, respectively. Furthermore, tripartite complex formations between Cyclin T, Hexim and Importin alpha showed the suitability of a collaborative nuclear import pathway for Cyclin T. Electrophoretic mobility shift assays using radioactively labelled full-length 7SK snRNA revealed a tight association of the RNA to Cyclin T1-Hexim1 with dissociation constants lower than 0.3 muM. Similar binding affinities were recorded for both Hexim orthologues to a 66-mer double-stranded 5' hairpin loop encompassing nucleotides 23-88 of 7SK, while a 39-mer fragment, resulting from different RNA folding predictions, did not bind as tightly. These results provide the molecular basis for the generation of a core complex for the inhibition of P-TEFb.
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Affiliation(s)
- Nadine Czudnochowski
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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Poe JA, Smithgall TE. HIV-1 Nef dimerization is required for Nef-mediated receptor downregulation and viral replication. J Mol Biol 2009; 394:329-42. [PMID: 19781555 DOI: 10.1016/j.jmb.2009.09.047] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/15/2009] [Accepted: 09/17/2009] [Indexed: 10/20/2022]
Abstract
Nef, a human immunodeficiency virus type 1 (HIV-1) accessory factor capable of interaction with a diverse array of host cell signaling molecules, is essential for high-titer HIV replication and AIDS progression. Previous biochemical and structural studies have suggested that Nef may form homodimers and higher-order oligomers in HIV-infected cells, which may be required for both immune and viral receptor downregulation as well as viral replication. Using bimolecular fluorescence complementation, we provide the first direct evidence for Nef dimers within HIV host cells and identify the structural requirements for dimerization in vivo. Bimolecular fluorescence complementation analysis shows that the multiple hydrophobic and electrostatic interactions found within the dimerization interface of the Nef X-ray crystal structure are essential for dimerization in cells. Nef dimers localized to the plasma membrane as well as the trans-Golgi network, two subcellular localizations essential for Nef function. Mutations in the Nef dimerization interface dramatically reduced both Nef-induced CD4 downregulation and HIV replication. Viruses expressing dimerization-defective Nef mutants were disabled to the same extent as HIV that fails to express Nef in terms of replication. These results identify the Nef dimerization region as a potential molecular target for antiretroviral drug discovery.
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Affiliation(s)
- Jerrod A Poe
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, E1240 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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Dual acylation accounts for the localization of {alpha}19-giardin in the ventral flagellum pair of Giardia lamblia. EUKARYOTIC CELL 2009; 8:1567-74. [PMID: 19684283 DOI: 10.1128/ec.00136-09] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A Giardia-specific protein family denominated as alpha-giardins, represents the major protein component, besides tubulin, of the cytoskeleton of the human pathogenic parasite Giardia lamblia. One of its members, alpha19-giardin, carries an N-terminal sequence extension of MGCXXS, which in many proteins serves as a target for dual lipid conjugation: myristoylation at the glycine residue after removal of the methionine and palmitoylation at the cysteine residue. As the first experimental evidence of a lipid modification, we found alpha19-giardin to be associated with the membrane fraction of disrupted trophozoites. After heterologous coexpression of alpha19-giardin with giardial N-myristoyltransferase (NMT) in Escherichia coli, we found the protein in a myristoylated form. Additionally, after heterologous expression together with the palmitoyl transferase Pfa3 in Saccharomyces cerevisiae, alpha19-giardin associates with the membrane of the main vacuole. Immunocytochemical colocalization studies on wild-type Giardia trophozoites with tubulin provide evidence that alpha19-giardin exclusively localizes to the ventral pair of the giardial flagella. A mutant in which the putatively myristoylated N-terminal glycine residue was replaced by alanine lost this specific localization. Our findings suggest that the dual lipidation of alpha19-giardin is responsible for its specific flagellar localization.
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Szilluweit R, Boll A, Lukowski S, Gerlach H, Fackler OT, Geyer M, Steinem C. HIV-1 Nef perturbs artificial membranes: investigation of the contribution of the myristoyl anchor. Biophys J 2009; 96:3242-50. [PMID: 19383468 DOI: 10.1016/j.bpj.2008.12.3947] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 12/03/2008] [Accepted: 12/30/2008] [Indexed: 12/19/2022] Open
Abstract
Nef, an accessory protein from human immunodeficiency virus type 1, is critical for optimal viral replication and pathogenesis. Here, we analyzed the influence of full-length myristoylated and nonmyristoylated Nef on artificial lipid bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). By means of cosedimentation assays, we found that neither nonmyristoylated nor myristoylated Nef stably binds to POPC unilamellar vesicles. Time-resolved ellipsometry rather indicates that the proteins perturb the assembly of POPC planar bilayers. This observation was corroborated by fluorescence and scanning force microscopy, suggesting that membrane disordering occurs upon interaction of full-length myristoylated and nonmyristoylated Nef with planar POPC membranes immobilized on SiO(2) surfaces resulting in loss of material from the surface. The membrane perturbations were further investigated by vesicle release experiments, demonstrating that the disordering results in defects through which the fluorophor carboxyfluorescein can pass. From these results, we conclude that Nef is capable of disordering and perturbing lipid membranes and that the myristoyl group is not the decisive determinant for the action of the protein on lipid membranes.
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Affiliation(s)
- Ruth Szilluweit
- Institute of Organic and Biomolecular Chemistry, Georg-August University, 37077 Göttingen, Germany
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Abstract
The development of anti-virals has blunted the AIDS epidemic in the Western world but globally the epidemic has not been curtailed. Standard vaccines have not worked, and attenuated vaccines are not being developed because of safety concerns. Interest in attenuated vaccines has centered on isolated cases of patients infected with HIV-1 containing a deleted nef gene. Nef is a multifunctional accessory protein that is necessary for full HIV-1 virulence. Unfortunately, some patients infected with the nef-deleted virus eventually lose their CD4+ T cells to levels indicating progression to AIDS. This renders the possibility of an attenuated HIV-1 based solely on a deleted nef remote. In this review we discuss the knowledge gained both from the study of these patients and from in vitro investigations of Nef function to assess the possibility of developing new anti-HIV-1 drugs based on Nef. Specifically, we consider CD4 downregulation, major histocompatibility complex I downregulation, Pak2 activation, and enhancement of virion infectivity. We also consider the recent proposal that simian immunodeficiency viruses are non-pathogenic in their hosts because they have Nefs that downregulate CD3, but HIV-1 is pathogenic because its Nef fails to downregulate CD3. The possibility of incorporating the CD3 downregulation function into HIV-1 Nef as a therapeutic option is also considered. Finally, we conclude that inhibiting the CD4 downregulation function is the most promising Nef-targeted approach for developing a new anti-viral as a contribution to combating AIDS.
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Affiliation(s)
- John L Foster
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Brown PH, Balbo A, Schuck P. Characterizing protein-protein interactions by sedimentation velocity analytical ultracentrifugation. CURRENT PROTOCOLS IN IMMUNOLOGY 2008; Chapter 18:18.15.1-18.15.39. [PMID: 18491296 DOI: 10.1002/0471142735.im1815s81] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This unit introduces the basic principles and practice of sedimentation velocity analytical ultracentrifugation for the study of reversible protein interactions, such as the characterization of self-association, heterogeneous association, multi-protein complexes, binding stoichiometry, and the determination of association constants. The analytical tools described include sedimentation coefficient and molar mass distributions, multi-signal sedimentation coefficient distributions, Gilbert-Jenkins theory, different forms of isotherms, and global Lamm equation modeling. Concepts for the experimental design are discussed, and a detailed step-by-step protocol guiding the reader through the experiment and the data analysis is available as an Internet resource.
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Affiliation(s)
| | - Andrea Balbo
- National Institutes of Health, Bethesda, Maryland
| | - Peter Schuck
- National Institutes of Health, Bethesda, Maryland
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Pylypenko O, Schönichen A, Ludwig D, Ungermann C, Goody RS, Rak A, Geyer M. Farnesylation of the SNARE protein Ykt6 increases its stability and helical folding. J Mol Biol 2008; 377:1334-45. [PMID: 18329045 DOI: 10.1016/j.jmb.2008.01.099] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/28/2008] [Accepted: 01/29/2008] [Indexed: 11/28/2022]
Abstract
The evolutionarily conserved soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are involved in the fusion of vesicles with their target membranes. While most SNAREs are permanently anchored to membranes by their transmembrane domains, the vesicle-associated SNARE Ykt6 has been found both in soluble and in membrane-bound pools. The R-SNARE Ykt6 is thought to mediate interactions between various Q-SNAREs by a reversible membrane-targeting cycle. Membrane attachment of Ykt6 is achieved by its C-terminal prenylation and palmitoylation motif succeeding the SNARE motif. In this study, we have analyzed full-length farnesylated Ykt6 from yeast and humans by biochemical and structural means. In vitro farnesylation of the C-terminal CAAX box of recombinant full-length Ykt6 resulted in stabilization of the native protein and a more compactly folded structure, as shown by size exclusion chromatography and limited proteolysis. Circular dichroism spectroscopy indicated a specific increase in the helical content of the farnesylated Ykt6 compared to the nonlipidated form or the single-longin domain, which correlated with a marked increase in stability as observed by heat denaturation experiments. Although highly soluble, farnesylated Ykt6 is capable of lipid membrane binding independent of the membrane charge, as shown by surface plasmon resonance. The crystal structure of the N-terminal longin domain of yeast Ykt6 (1-140) was determined at 2.5 A resolution. As similarly found in a previous NMR structure, the Ykt6 longin domain contains a hydrophobic patch at its surface that may accommodate the lipid moiety. In the crystal structure, this hydrophobic surface is buried in a crystallographic homomeric dimer interface. Together, these observations support a previously suggested closed conformation of cytosolic Ykt6, where the C-terminal farnesyl moiety folds onto a hydrophobic groove in the N-terminal longin domain.
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Affiliation(s)
- Olena Pylypenko
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
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45
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Brügger B, Krautkrämer E, Tibroni N, Munte CE, Rauch S, Leibrecht I, Glass B, Breuer S, Geyer M, Kräusslich HG, Kalbitzer HR, Wieland FT, Fackler OT. Human immunodeficiency virus type 1 Nef protein modulates the lipid composition of virions and host cell membrane microdomains. Retrovirology 2007; 4:70. [PMID: 17908312 PMCID: PMC2065869 DOI: 10.1186/1742-4690-4-70] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 10/01/2007] [Indexed: 01/03/2023] Open
Abstract
Background The Nef protein of Human Immunodeficiency Viruses optimizes viral spread in the infected host by manipulating cellular transport and signal transduction machineries. Nef also boosts the infectivity of HIV particles by an unknown mechanism. Recent studies suggested a correlation between the association of Nef with lipid raft microdomains and its positive effects on virion infectivity. Furthermore, the lipidome analysis of HIV-1 particles revealed a marked enrichment of classical raft lipids and thus identified HIV-1 virions as an example for naturally occurring membrane microdomains. Since Nef modulates the protein composition and function of membrane microdomains we tested here if Nef also has the propensity to alter microdomain lipid composition. Results Quantitative mass spectrometric lipidome analysis of highly purified HIV-1 particles revealed that the presence of Nef during virus production from T lymphocytes enforced their raft character via a significant reduction of polyunsaturated phosphatidylcholine species and a specific enrichment of sphingomyelin. In contrast, Nef did not significantly affect virion levels of phosphoglycerolipids or cholesterol. The observed alterations in virion lipid composition were insufficient to mediate Nef's effect on particle infectivity and Nef augmented virion infectivity independently of whether virus entry was targeted to or excluded from membrane microdomains. However, altered lipid compositions similar to those observed in virions were also detected in detergent-resistant membrane preparations of virus producing cells. Conclusion Nef alters not only the proteome but also the lipid composition of host cell microdomains. This novel activity represents a previously unrecognized mechanism by which Nef could manipulate HIV-1 target cells to facilitate virus propagation in vivo.
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Affiliation(s)
- Britta Brügger
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | | | - Nadine Tibroni
- Abteilung Virologie, Universität Heidelberg, Heidelberg, Germany
| | - Claudia E Munte
- Institut für Biophysik und Physikalische Biochemie, Universität Regensburg, Regensburg, Germany
| | - Susanne Rauch
- Abteilung Virologie, Universität Heidelberg, Heidelberg, Germany
| | - Iris Leibrecht
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Bärbel Glass
- Abteilung Virologie, Universität Heidelberg, Heidelberg, Germany
| | - Sebastian Breuer
- Max-Planck-Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Dortmund, Germany
| | - Matthias Geyer
- Max-Planck-Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Dortmund, Germany
| | | | - Hans Robert Kalbitzer
- Institut für Biophysik und Physikalische Biochemie, Universität Regensburg, Regensburg, Germany
| | - Felix T Wieland
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Oliver T Fackler
- Abteilung Virologie, Universität Heidelberg, Heidelberg, Germany
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Dames SA, Schönichen A, Schulte A, Barboric M, Peterlin BM, Grzesiek S, Geyer M. Structure of the Cyclin T binding domain of Hexim1 and molecular basis for its recognition of P-TEFb. Proc Natl Acad Sci U S A 2007; 104:14312-7. [PMID: 17724342 PMCID: PMC1955226 DOI: 10.1073/pnas.0701848104] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hexim1 is a cellular protein that associates with the positive transcription elongation factor b (P-TEFb) to regulate RNA polymerase II elongation of nascent mRNA transcripts. It directly binds to Cyclin T1 of P-TEFb and inhibits the kinase activity of Cdk9, leading to an arrest of transcription elongation. Here, we report the solution structure of the Cyclin T binding domain (TBD) of Hexim1 that forms a parallel coiled-coil homodimer composed of two segments and a preceding alpha helix that folds back onto the first coiled-coil unit. NMR titration, fluorescence, and immunoprecipitation experiments revealed the binding interface to Cyclin T1, which covers a large surface on the first coiled-coil segment. Electrostatic interactions between an acidic patch on Hexim1 and positively charged residues of Cyclin T1 drive the complex formation that is confirmed by mutagenesis data on Hexim1 mediated transcription regulation in cells. Thus, our studies provide structural insights how Hexim1 recognizes the Cyclin T1 subunit of P-TEFb, which is a key step toward the regulation of transcription elongation.
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Affiliation(s)
- Sonja A. Dames
- *Department of Structural Biology, Biozentrum Basel, University of Basel, 4003 Basel, Switzerland
- To whom correspondence may be addressed. E-mail: and
| | - André Schönichen
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, 44227 Dortmund, Germany; and
| | - Antje Schulte
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, 44227 Dortmund, Germany; and
| | - Matjaz Barboric
- Departments of Medicine, Microbiology, and Immunology, Rosalind Russell Medical Research Center, University of California, San Francisco, CA 94143
| | - B. Matija Peterlin
- Departments of Medicine, Microbiology, and Immunology, Rosalind Russell Medical Research Center, University of California, San Francisco, CA 94143
| | - Stephan Grzesiek
- *Department of Structural Biology, Biozentrum Basel, University of Basel, 4003 Basel, Switzerland
| | - Matthias Geyer
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, 44227 Dortmund, Germany; and
- To whom correspondence may be addressed. E-mail: and
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47
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Pizzato M, Helander A, Popova E, Calistri A, Zamborlini A, Palù G, Göttlinger HG. Dynamin 2 is required for the enhancement of HIV-1 infectivity by Nef. Proc Natl Acad Sci U S A 2007; 104:6812-7. [PMID: 17412836 PMCID: PMC1871867 DOI: 10.1073/pnas.0607622104] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nef is a virulence factor of HIV-1 and other primate lentiviruses that is crucial for rapid progression to AIDS. In cell culture, Nef increases the infectivity of HIV-1 progeny virions by an unknown mechanism. We now show that dynamin 2 (Dyn2), a key regulator of vesicular trafficking, is a binding partner of Nef that is required for its ability to increase viral infectivity. Dominant-negative Dyn2 or the depletion of Dyn2 by small interfering RNA potently inhibited the effect of Nef on HIV-1 infectivity. Furthermore, in Dyn2-depleted cells, this function of Nef could be rescued by ectopically expressed Dyn2 but not by Dyn1, a closely related isoform that does not bind Nef. The infectivity enhancement by Nef also depended on clathrin, because it was diminished in clathrin-depleted cells and profoundly inhibited in cells expressing the clathrin-binding domain of AP180, which blocks clathrin-coated pit formation but not clathrin-independent endocytosis. Together, these findings imply that the infectivity enhancement activity of Nef depends on Dyn2- and clathrin-mediated membrane invagination events.
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Affiliation(s)
- Massimo Pizzato
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
- Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, I-35121 Padua, Italy; and
- Department of Infectious Diseases, Division of Medicine, Imperial College London, London W2 1PG, United Kingdom
- To whom correspondence may be addressed. E-mail: or
| | - Anna Helander
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
| | - Elena Popova
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
| | - Arianna Calistri
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
- Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, I-35121 Padua, Italy; and
| | - Alessia Zamborlini
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
- Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, I-35121 Padua, Italy; and
| | - Giorgio Palù
- Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, I-35121 Padua, Italy; and
| | - Heinrich G. Göttlinger
- *Department of Cancer Immunology and AIDS, Dana–Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115
- To whom correspondence may be addressed. E-mail: or
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48
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Xia X. The +4G site in Kozak consensus is not related to the efficiency of translation initiation. PLoS One 2007; 2:e188. [PMID: 17285142 PMCID: PMC1781341 DOI: 10.1371/journal.pone.0000188] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 01/05/2007] [Indexed: 01/19/2023] Open
Abstract
The optimal context for translation initiation in mammalian species is GCCRCCaugG (where R = purine and “aug” is the initiation codon), with the -3R and +4G being particularly important. The presence of +4G has been interpreted as necessary for efficient translation initiation. Accumulated experimental and bioinformatic evidence has suggested an alternative explanation based on amino acid constraint on the second codon, i.e., amino acid Ala or Gly are needed as the second amino acid in the nascent peptide for the cleavage of the initiator Met, and the consequent overuse of Ala and Gly codons (GCN and GGN) leads to the +4G consensus. I performed a critical test of these alternative hypotheses on +4G based on 34169 human protein-coding genes and published gene expression data. The result shows that the prevalence of +4G is not related to translation initiation. Among the five G-starting codons, only alanine codons (GCN), and glycine codons (GGN) to a much smaller extent, are overrepresented at the second codon, whereas the other three codons are not overrepresented. While highly expressed genes have more +4G than lowly expressed genes, the difference is caused by GCN and GGN codons at the second codon. These results are inconsistent with +4G being needed for efficient translation initiation, but consistent with the proposal of amino acid constraint hypothesis.
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Affiliation(s)
- Xuhua Xia
- Department of Biology, University of Ottawa, Ottawa, Canada.
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49
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Mangino G, Percario ZA, Fiorucci G, Vaccari G, Manrique S, Romeo G, Federico M, Geyer M, Affabris E. In vitro treatment of human monocytes/macrophages with myristoylated recombinant Nef of human immunodeficiency virus type 1 leads to the activation of mitogen-activated protein kinases, IkappaB kinases, and interferon regulatory factor 3 and to the release of beta interferon. J Virol 2006; 81:2777-91. [PMID: 17182689 PMCID: PMC1865981 DOI: 10.1128/jvi.01640-06] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The viral protein Nef is a virulence factor that plays multiple roles during the early and late phases of human immunodeficiency virus (HIV) replication. Nef regulates the cell surface expression of critical proteins (including down-regulation of CD4 and major histocompatibility complex class I), T-cell receptor signaling, and apoptosis, inducing proapoptotic effects in uninfected bystander cells and antiapoptotic effects in infected cells. It has been proposed that Nef intersects the CD40 ligand signaling pathway in macrophages, leading to modification in the pattern of secreted factors that appear able to recruit and activate T lymphocytes, rendering them susceptible to HIV infection. There is also increasing evidence that in vitro cell treatment with Nef induces signaling effects. Exogenous Nef treatment is able to induce apoptosis in uninfected T cells, maturation in dendritic cells, and suppression of CD40-dependent immunoglobulin class switching in B cells. Previously, we reported that Nef treatment of primary human monocyte-derived macrophages (MDMs) induces a cycloheximide-independent activation of NF-kappaB and the synthesis and secretion of a set of chemokines/cytokines that activate STAT1 and STAT3. Here, we show that Nef treatment is capable of hijacking cellular signaling pathways, inducing a very rapid regulatory response in MDMs that is characterized by the rapid and transient phosphorylation of the alpha and beta subunits of the IkappaB kinase complex and of JNK, ERK1/2, and p38 mitogen-activated protein kinase family members. In addition, we have observed the activation of interferon regulatory factor 3, leading to the synthesis of beta interferon mRNA and protein, which in turn induces STAT2 phosphorylation. All of these effects require Nef myristoylation.
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Affiliation(s)
- Giorgio Mangino
- Department of Biology-University Roma Tre, Viale G. Marconi 446, 00146 Rome, Italy
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50
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Lehmann MH, Walter S, Ylisastigui L, Striebel F, Ovod V, Geyer M, Gluckman JC, Erfle V. Extracellular HIV-1 Nef increases migration of monocytes. Exp Cell Res 2006; 312:3659-68. [PMID: 16978607 DOI: 10.1016/j.yexcr.2006.08.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Revised: 07/21/2006] [Accepted: 08/11/2006] [Indexed: 02/01/2023]
Abstract
Infiltration of human immunodeficiency virus type 1 (HIV-1)-infected and uninfected monocytes/macrophages in organs and tissues is a general phenomenon observed in progression of acquired immunodeficiency syndrome (AIDS). HIV-1 protein Nef is considered as a progression factor in AIDS, and is released from HIV-1-infected cells. Here, we show that extracellular Nef increases migration of monocytes. This effect is (i) concentration-dependent, (ii) reaches the order of magnitude of that induced by formyl-methyonyl-leucyl-proline (fMLP) or CC chemokine ligand 2 (CCL2)/monocyte chemotactic protein (MCP)-1, (iii) inhibited by anti-Nef monoclonal antibodies as well as by heating, and (iv) depends on a concentration gradient of Nef. Further, Nef does not elicit monocytic THP-1 cells to express chemokines such as CCL2, macrophage inhibitory protein-1alpha (CCL3) and macrophage inhibitory protein-1beta (CCL4). These data suggest that extracellular Nef may contribute to disease progression as well as HIV-1 spreading through affecting migration of monocytes.
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Affiliation(s)
- Michael H Lehmann
- Institute of Molecular Virology, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
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