1
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Xie P, Zhang H, Qin Y, Xiong H, Shi C, Zhou Z. Membrane Proteins and Membrane Curvature: Mutual Interactions and a Perspective on Disease Treatments. Biomolecules 2023; 13:1772. [PMID: 38136643 PMCID: PMC10741411 DOI: 10.3390/biom13121772] [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: 11/01/2023] [Revised: 11/30/2023] [Accepted: 12/07/2023] [Indexed: 12/24/2023] Open
Abstract
The pathogenesis of various diseases often involves an intricate interplay between membrane proteins and membrane curvature. Understanding the underlying mechanisms of this interaction could offer novel perspectives on disease treatment. In this review, we provide an introduction to membrane curvature and its association with membrane proteins. Furthermore, we delve into the impact and potential implications of this interaction in the context of disease treatment. Lastly, we discuss the prospects and challenges associated with harnessing these interactions for effective disease management, aiming to provide fresh insights into therapeutic strategies.
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Affiliation(s)
| | | | | | | | | | - Zijian Zhou
- State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedicine Laboratory & Center for Molecular Imaging and Translational Medicine, School of Public Health, Shenzhen Research Institute of Xiamen University, Xiamen University, Xiamen 361102, China; (P.X.); (H.Z.); (Y.Q.); (H.X.); (C.S.)
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2
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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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3
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Majumder S, Deganutti G, Pipitò L, Chaudhuri D, Datta J, Giri K. Computer-aided de novo design and optimization of novel potential inhibitors of HIV-1 Nef protein. Comput Biol Chem 2023; 104:107871. [PMID: 37084691 DOI: 10.1016/j.compbiolchem.2023.107871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 04/07/2023] [Accepted: 04/14/2023] [Indexed: 04/23/2023]
Abstract
Nef is a small accessory protein pivotal in the HIV-1 viral replication cycle. It is a multifunctional protein and its interactions with kinases in host cells have been well characterized through many in vitro and structural studies. Nef forms a homodimer to activate the kinases and subsequently the phosphorylation pathways. The disruption of its homodimerization represents a valuable approach in the search for novel classes of antiretroviral. However, this research avenue is still underdeveloped as just a few Nef inhibitors have been reported so far, with very limited structural information about their mechanism of action. To address this issue, we have employed an in silico structure-based drug design strategy that combines de novo ligand design with molecular docking and extensive molecular dynamics simulations. Since the Nef pocket involved in homodimerization has high lipophilicity, the initial de novo-designed structures displayed poor drug-likeness and solubility. Taking information from the hydration sites within the homodimerization pocket, structural modifications in the initial lead compound have been introduced to improve the solubility and drug-likeness, without affecting the binding profile. We propose lead compounds that can be the starting point for further optimizations to deliver long-awaited, rationally designed Nef inhibitors.
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Affiliation(s)
| | - Giuseppe Deganutti
- Centre for Sport, Exercise, and Life Sciences, Coventry University, Coventry CV1 5FB, UK
| | - Ludovico Pipitò
- Centre for Sport, Exercise, and Life Sciences, Coventry University, Coventry CV1 5FB, UK
| | | | - Joyeeta Datta
- Department of Life Sciences, Presidency University, Kolkata, India
| | - Kalyan Giri
- Department of Life Sciences, Presidency University, Kolkata, India.
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4
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Emert-Sedlak LA, Shi H, Tice CM, Chen L, Alvarado JJ, Shu ST, Du S, Thomas CE, Wrobel JE, Reitz AB, Smithgall TE. Antiretroviral Drug Discovery Targeting the HIV-1 Nef Virulence Factor. Viruses 2022; 14:v14092025. [PMID: 36146831 PMCID: PMC9503669 DOI: 10.3390/v14092025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 11/16/2022] Open
Abstract
While antiretroviral drugs have transformed the lives of HIV-infected individuals, chronic treatment is required to prevent rebound from viral reservoir cells. People living with HIV also are at higher risk for cardiovascular and neurocognitive complications, as well as cancer. Finding a cure for HIV-1 infection is therefore an essential goal of current AIDS research. This review is focused on the discovery of pharmacological inhibitors of the HIV-1 Nef accessory protein. Nef is well known to enhance HIV-1 infectivity and replication, and to promote immune escape of HIV-infected cells by preventing cell surface MHC-I display of HIV-1 antigens. Recent progress shows that Nef inhibitors not only suppress HIV-1 replication, but also restore sufficient MHC-I to the surface of infected cells to trigger a cytotoxic T lymphocyte response. Combining Nef inhibitors with latency reversal agents and therapeutic vaccines may provide a path to clearance of viral reservoirs.
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Affiliation(s)
- Lori A. Emert-Sedlak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Haibin Shi
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Colin M. Tice
- Fox Chase Chemical Diversity Center, Inc., Pennsylvania Biotechnology Center, Doylestown, PA 18902, USA
| | - Li Chen
- 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
| | - Sherry T. Shu
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Shoucheng Du
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Catherine E. Thomas
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Jay E. Wrobel
- Fox Chase Chemical Diversity Center, Inc., Pennsylvania Biotechnology Center, Doylestown, PA 18902, USA
| | - Allen B. Reitz
- Fox Chase Chemical Diversity Center, Inc., Pennsylvania Biotechnology Center, Doylestown, PA 18902, USA
| | - Thomas E. Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
- Correspondence:
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5
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Jin R, Cao R, Baumgart T. Curvature dependence of BAR protein membrane association and dissociation kinetics. Sci Rep 2022; 12:7676. [PMID: 35538113 PMCID: PMC9091223 DOI: 10.1038/s41598-022-11221-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 04/18/2022] [Indexed: 11/09/2022] Open
Abstract
BAR (Bin/Amphiphysin/Rvs) domain containing proteins function as lipid bilayer benders and curvature sensors, and they contribute to membrane shaping involved in cell signaling and metabolism. The mechanism for their membrane shape sensing has been investigated by both equilibrium binding and kinetic studies. In prior research, stopped-flow spectroscopy has been used to deduce a positive dependence on membrane curvature for the binding rate constant, kon, of a BAR protein called endophilin. However, the impact of bulk diffusion of endophilin, on the kinetic binding parameters has not been thoroughly considered. Employing similar methods, and using lipid vesicles of multiple sizes, we obtained a linear dependence of kon on vesicle curvature. However, we found that the observed relation can be explained without considering the local curvature sensing ability of endophilin in the membrane association process. In contrast, the diffusion-independent unbinding rate constant (koff) obtained from stopped-flow measurements shows a negative dependence on membrane curvature, which is controlled/mediated by endophilin-membrane interactions. This latter dependency, in addition to protein-protein interactions on the membrane, explains the selective binding of BAR proteins to highly curved membranes in equilibrium binding experiments.
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Affiliation(s)
- Rui Jin
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Rui Cao
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.,Division of Biostatistics, University of Minnesota, Minneapolis, MN, USA
| | - Tobias Baumgart
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
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6
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Liu C, Zhang Y, Ge L, Li L, Wu B, Wang J. Biochemical and NMR studies reveal specific interaction between STIMATE C-tail and PI(4,5)P 2 or PI(3,4,5)P 3-containing membrane. Biochem Biophys Res Commun 2022; 597:16-22. [PMID: 35121178 DOI: 10.1016/j.bbrc.2022.01.100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 11/28/2022]
Abstract
STIMATE is an endoplasmic reticulum (ER) resident membrane protein that plays key roles in regulating calcium signaling occurring at ER-plasma membrane (PM) junctions. It is also involved in the regulation of ER-PM junction maintenance. STIMATE contains multiple putative transmembrane domains with a polybasic C tail (STIMATE-CT) that directly interacts with stromal interaction molecule 1 (STIM1) to promote STIM1 conformational switch. Here using liposome pulldown assay, we show that STIMATE-CT can specifically interact with PI(4,5)P2 or PI(3,4,5)P3-containing membrane. NMR analysis indicates that STIMATE-CT is intrinsically disordered. Furthermore, NMR titration with bicelles and mutation analysis reveal that the regions of 242VRYR245 and 284KKKK287 in STIMATE-CT are both essential for its membrane binding.
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Affiliation(s)
- Chongxu Liu
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China; University of Science and Technology of China, Hefei, Anhui, 230036, PR China
| | - Youjia Zhang
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China; University of Science and Technology of China, Hefei, Anhui, 230036, PR China
| | - Liang Ge
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China
| | - Ling Li
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China; University of Science and Technology of China, Hefei, Anhui, 230036, PR China
| | - Bo Wu
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China.
| | - Junfeng Wang
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China; Institutes of Physical Science and Information Technology, Anhui University, Hefei, Anhui, 230601, PR China.
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7
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Jacob RA, Edgar CR, Prévost J, Trothen SM, Lurie A, Mumby MJ, Galbraith A, Kirchhoff F, Haeryfar SMM, Finzi A, Dikeakos JD. The HIV-1 accessory protein Nef increases surface expression of the checkpoint receptor Tim-3 in infected CD4 + T cells. J Biol Chem 2021; 297:101042. [PMID: 34358561 PMCID: PMC8390549 DOI: 10.1016/j.jbc.2021.101042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/28/2021] [Accepted: 08/02/2021] [Indexed: 12/17/2022] Open
Abstract
Prolonged immune activation drives the upregulation of multiple checkpoint receptors on the surface of virus-specific T cells, inducing their exhaustion. Reversing HIV-1-induced T cell exhaustion is imperative for efficient virus clearance; however, viral mediators of checkpoint receptor upregulation remain largely unknown. The enrichment of checkpoint receptors on T cells upon HIV-1 infection severely constrains the generation of an efficient immune response. Herein, we examined the role of HIV-1 Nef in mediating the upregulation of checkpoint receptors on peripheral blood mononuclear cells. We demonstrate that the HIV-1 accessory protein Nef upregulates cell surface levels of the checkpoint receptor T-cell immunoglobulin mucin domain-3 (Tim-3) and that this is dependent on Nef's dileucine motif LL164/165. Furthermore, we used a bimolecular fluorescence complementation assay to demonstrate that Nef and Tim-3 form a complex within cells that is abrogated upon mutation of the Nef dileucine motif. We also provide evidence that Nef moderately promotes Tim-3 shedding from the cell surface in a dileucine motif–dependent manner. Treating HIV-1-infected CD4+ T cells with a matrix metalloprotease inhibitor enhanced cell surface Tim-3 levels and reduced Tim-3 shedding. Finally, Tim-3-expressing CD4+ T cells displayed a higher propensity to release the proinflammatory cytokine interferon-gamma. Collectively, our findings uncover a novel mechanism by which HIV-1 directly increases the levels of a checkpoint receptor on the surface of infected CD4+ T cells.
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Affiliation(s)
- Rajesh Abraham Jacob
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Cassandra R Edgar
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Jérémie Prévost
- Centre de Recherche du CHUM, Montreal, Quebec, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, Quebec, Canada
| | - Steven M Trothen
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Antony Lurie
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Mitchell J Mumby
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Alexa Galbraith
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, UIm, Germany
| | - S M Mansour Haeryfar
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Andrés Finzi
- Centre de Recherche du CHUM, Montreal, Quebec, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, Quebec, Canada; Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
| | - Jimmy D Dikeakos
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
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8
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Adzhubei AA, Kulkarni A, Tolstova AP, Anashkina AA, Sviridov D, Makarov AA, Bukrinsky MI. Direct interaction between ABCA1 and HIV-1 Nef: Molecular modeling and virtual screening for inhibitors. Comput Struct Biotechnol J 2021; 19:3876-3884. [PMID: 34584633 PMCID: PMC8440812 DOI: 10.1016/j.csbj.2021.06.050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/23/2021] [Accepted: 06/30/2021] [Indexed: 12/18/2022] Open
Abstract
HIV-1 infection impairs cellular cholesterol efflux by downmodulating the cholesterol transporter ABCA1, leading to metabolic co-morbidities like cardio-vascular disease. The main mechanism of this effect is impairment by the HIV-1 protein Nef of the ABCA1 interaction with the endoplasmic reticulum chaperone calnexin, which leads to a block in ABCA1 maturation followed by its degradation. However, ABCA1 is also downmodulated by Nef delivered with the extracellular vesicles, suggesting involvement of a direct Nef:ABCA1 interaction at the plasma membrane. Here, we present an optimized model of the Nef:ABCA1 interaction, which identifies interaction sites and provides an opportunity to perform a virtual screening for potential inhibitors. Interestingly, the predicted sites on Nef involved in the ABCA1 interaction overlap with those involved in the interaction with calnexin. The compounds previously shown to block Nef:calnexin interaction were among the top ranking ligands in docking simulations with ABCA1-interacting sites on Nef, suggesting the possibility that both interactions can be inhibited by the same chemical compounds. This study identifies a series of compounds for potential development as inhibitors of Nef-mediated co-morbidities of HIV infection.
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Affiliation(s)
- Alexei A. Adzhubei
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Amol Kulkarni
- Howard University College of Pharmacy, Washington, District of Columbia, USA
| | - Anna P. Tolstova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | | | - Dmitri Sviridov
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Alexander A. Makarov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Michael I. Bukrinsky
- The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
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9
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Synergy and allostery in ligand binding by HIV-1 Nef. Biochem J 2021; 478:1525-1545. [PMID: 33787846 PMCID: PMC8079166 DOI: 10.1042/bcj20201002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/29/2021] [Accepted: 03/31/2021] [Indexed: 11/27/2022]
Abstract
The Nef protein of human and simian immunodeficiency viruses boosts viral pathogenicity through its interactions with host cell proteins. By combining the polyvalency of its large unstructured regions with the binding selectivity and strength of its folded core domain, Nef can associate with many different host cell proteins, thereby disrupting their functions. For example, the combination of a linear proline-rich motif and hydrophobic core domain surface allows Nef to bind tightly and specifically to SH3 domains of Src family kinases. We investigated whether the interplay between Nef's flexible regions and its core domain could allosterically influence ligand selection. We found that the flexible regions can associate with the core domain in different ways, producing distinct conformational states that alter the way in which Nef selects for SH3 domains and exposes some of its binding motifs. The ensuing crosstalk between ligands might promote functionally coherent Nef-bound protein ensembles by synergizing certain subsets of ligands while excluding others. We also combined proteomic and bioinformatics analyses to identify human proteins that select SH3 domains in the same way as Nef. We found that only 3% of clones from a whole-human fetal library displayed Nef-like SH3 selectivity. However, in most cases, this selectivity appears to be achieved by a canonical linear interaction rather than by a Nef-like ‘tertiary' interaction. Our analysis supports the contention that Nef's mode of hijacking SH3 domains is a virus-specific adaptation with no or very few cellular counterparts. Thus, the Nef tertiary binding surface is a promising virus-specific drug target.
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10
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Morita D, Iwashita C, Mizutani T, Mori N, Mikami B, Sugita M. Crystal structure of the ternary complex of TCR, MHC class I and lipopeptides. Int Immunol 2020; 32:805-810. [PMID: 32720986 DOI: 10.1093/intimm/dxaa050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/22/2020] [Indexed: 11/12/2022] Open
Abstract
The covalent conjugation of a 14-carbon fatty acid (myristic acid) to the N-terminal Gly residue, termed N-myristoylation, occurs in some viral proteins to dictate their pathological function. This protein lipidation reaction, however, is monitored by host cytotoxic T lymphocytes that are capable of recognizing N-terminal lipopeptide fragments in the context of major histocompatibility complex (MHC) class I molecules. In a rhesus model of human AIDS, for example, the classical MHC class I allomorph, Mamu-B*05104, was shown to bind SIV Nef-derived 4-mer lipopeptides (myristic acid-Gly-Gly-Ala-Ile; C14nef4) and present them to the CD8+ T-cell line, SN45. These lipopeptides accommodated in MHC class I molecules expose much shorter peptide chains than conventional MHC class I-presented 8-10-mer peptides, and the molecular mechanisms by which αβ T-cell receptors (TCRs) recognize lipopeptides currently remain unclear. An X-ray crystallographic analysis of the SN45 TCR α and β heterodimer in a form that was co-crystallized with the C14nef4-bound Mamu-B*05104 complex indicated that the amide group of the N-myristoylated glycine residue offered a primary T-cell epitope by establishing a sole hydrogen bond between its nitrogen atom and the side chain of Glu at position 101 of CDR3β. Accordingly, the Glu to Ala mutation at this position resulted in the loss of lipopeptide recognition. On the other hand, TCRs were positioned remotely from the peptide portion of C14nef4, and strong interactions were not observed. Thus, these observations provide novel structural insights into lipopeptide recognition by TCRs, which contrast sharply with the general molecular principle of peptide recognition.
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Affiliation(s)
- Daisuke Morita
- Laboratory of Cell Regulation, Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan.,Laboratory of Cell Regulation and Molecular Network, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, Japan
| | - Chieri Iwashita
- Laboratory of Cell Regulation, Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan.,Laboratory of Cell Regulation and Molecular Network, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, Japan
| | - Tatsuaki Mizutani
- Laboratory of Cell Regulation, Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan.,Laboratory of Cell Regulation and Molecular Network, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, Japan
| | - Naoki Mori
- Laboratory of Chemical Ecology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Bunzo Mikami
- Laboratory of Applied Structural Biology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto, Japan
| | - Masahiko Sugita
- Laboratory of Cell Regulation, Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan.,Laboratory of Cell Regulation and Molecular Network, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, Japan
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11
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Staudt RP, Alvarado JJ, Emert-Sedlak LA, Shi H, Shu ST, Wales TE, Engen JR, Smithgall TE. Structure, function, and inhibitor targeting of HIV-1 Nef-effector kinase complexes. J Biol Chem 2020; 295:15158-15171. [PMID: 32862141 DOI: 10.1074/jbc.rev120.012317] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/28/2020] [Indexed: 11/06/2022] Open
Abstract
Antiretroviral therapy has revolutionized the treatment of AIDS, turning a deadly disease into a manageable chronic condition. Life-long treatment is required because existing drugs do not eradicate HIV-infected cells. The emergence of drug-resistant viral strains and uncertain vaccine prospects highlight the pressing need for new therapeutic approaches with the potential to clear the virus. The HIV-1 accessory protein Nef is essential for viral pathogenesis, making it a promising target for antiretroviral drug discovery. Nef enhances viral replication and promotes immune escape of HIV-infected cells but lacks intrinsic enzymatic activity. Instead, Nef works through diverse interactions with host cell proteins primarily related to kinase signaling pathways and endosomal trafficking. This review emphasizes the structure, function, and biological relevance of Nef interactions with host cell protein-tyrosine kinases in the broader context of Nef functions related to enhancement of the viral life cycle and immune escape. Drug discovery targeting Nef-mediated kinase activation has allowed identification of promising inhibitors of multiple Nef functions. Pharmacological inhibitors of Nef-induced MHC-I down-regulation restore the adaptive immune response to HIV-infected cells in vitro and have the potential to enhance immune recognition of latent viral reservoirs as part of a strategy for HIV clearance.
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Affiliation(s)
- Ryan P Staudt
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - John J Alvarado
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Lori A Emert-Sedlak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Haibin Shi
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Sherry T Shu
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Thomas E Wales
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, USA
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, USA
| | - Thomas E Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
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12
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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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13
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Mailler E, Waheed AA, Park SY, Gershlick DC, Freed EO, Bonifacino JS. The autophagy protein ATG9A promotes HIV-1 infectivity. Retrovirology 2019; 16:18. [PMID: 31269971 PMCID: PMC6607583 DOI: 10.1186/s12977-019-0480-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 06/24/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Nef is a multifunctional accessory protein encoded by HIV-1, HIV-2 and SIV that plays critical roles in viral pathogenesis, contributing to viral replication, assembly, budding, infectivity and immune evasion, through engagement of various host cell pathways. RESULTS To gain a better understanding of the role of host proteins in the functions of Nef, we carried out tandem affinity purification-mass spectrometry analysis, and identified over 70 HIV-1 Nef-interacting proteins, including the autophagy-related 9A (ATG9A) protein. ATG9A is a transmembrane component of the machinery for autophagy, a catabolic process in which cytoplasmic components are degraded in lysosomal compartments. Pulldown experiments demonstrated that ATG9A interacts with Nef from not only HIV-1 and but also SIV (cpz, smm and mac). However, expression of HIV-1 Nef had no effect on the levels and localization of ATG9A, and on autophagy, in the host cells. To investigate a possible role for ATG9A in virus replication, we knocked out ATG9A in HeLa cervical carcinoma and Jurkat T cells, and analyzed virus release and infectivity. We observed that ATG9A knockout (KO) had no effect on the release of wild-type (WT) or Nef-defective HIV-1 in these cells. However, the infectivity of WT virus produced from ATG9A-KO HeLa and Jurkat cells was reduced by ~ fourfold and eightfold, respectively, relative to virus produced from WT cells. This reduction in infectivity was independent of the interaction of Nef with ATG9A, and was not due to reduced incorporation of the viral envelope (Env) glycoprotein into the virus. The loss of HIV-1 infectivity was rescued by pseudotyping HIV-1 virions with the vesicular stomatitis virus G glycoprotein. CONCLUSIONS These studies indicate that ATG9A promotes HIV-1 infectivity in an Env-dependent manner. The interaction of Nef with ATG9A, however, is not required for Nef to enhance HIV-1 infectivity. We speculate that ATG9A could promote infectivity by participating in either the removal of a factor that inhibits infectivity or the incorporation of a factor that enhances infectivity of the viral particles. These studies thus identify a novel host cell factor implicated in HIV-1 infectivity, which may be amenable to pharmacologic manipulation for treatment of HIV-1 infection.
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Affiliation(s)
- Elodie Mailler
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Abdul A Waheed
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA
| | - Sang-Yoon Park
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - David C Gershlick
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Eric O Freed
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA.
| | - Juan S Bonifacino
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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Jin SW, Markle TJ, Anmole G, Rahimi A, Kuang XT, Brumme ZL, Brockman MA. Modulation of TCR-dependent NFAT signaling is impaired in HIV-1 Nef isolates from elite controllers. Virology 2019; 530:39-50. [PMID: 30780124 DOI: 10.1016/j.virol.2019.02.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/09/2019] [Accepted: 02/10/2019] [Indexed: 12/24/2022]
Abstract
HIV-1 Nef modulates the activation state of CD4+ T cells by altering signaling events elicited by the T cell receptor (TCR). Primary nef sequences exhibit extensive inter-individual diversity that influences their ability to downregulate CD4 and HLA class I; however, the impact of nef variation on modulation of T cell signaling is poorly characterized. Here, we measured TCR-mediated activation of NFAT transcription factor in the presence of nef alleles isolated from 45 elite controllers (EC) and 46 chronic progressors (CP). EC Nef clones displayed lower ability to inhibit NFAT signaling (median 87 [IQR 75-93]% relative to SF2 Nef) compared to CP clones (94 [IQR 89-98]%) (p < 0.001). Polymorphisms in Nef's N-terminal domain impaired its ability to inhibit NFAT signaling. Results indicate that primary nef alleles exhibit a range of abilities to modulate TCR-dependent NFAT signaling, implicating natural variation in this function as a potential contributor to differential HIV-1 pathogenesis.
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Affiliation(s)
- Steven W Jin
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Tristan J Markle
- Dept. of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Gursev Anmole
- Dept. of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Asa Rahimi
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Xiaomei T Kuang
- Dept. of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Zabrina L Brumme
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada; British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - Mark A Brockman
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada; Dept. of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada; British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada.
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15
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Erwin N, Dwivedi M, Mejuch T, Waldmann H, Winter R. UNC119A Decreases the Membrane Binding of Myristoylated c-Src. Chembiochem 2018; 19:1482-1487. [PMID: 29700916 DOI: 10.1002/cbic.201800158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Indexed: 12/26/2022]
Abstract
Plasma membrane localization of myristoylated c-Src, a proto-oncogene protein-tyrosine kinase, is required for its signaling activity. Recent studies proposed that UNC119 protein functions as a solubilizing factor for myristoylated proteins, thereby regulating their subcellular distribution and signaling. The underlying molecular mechanism by which UNC119 regulates the membrane binding of c-Src has remained elusive. By combining different biophysical techniques, we have found that binding of a myristoylated c-Src-derived N-terminal peptide (Myr-Src) by UNC119A results in a reduced membrane binding affinity of the peptide, due to the competition of binding to membranes. The dissociation of Myr-Src from membranes is facilitated in the presence of UNC119A, as a consequence of which the clustering propensity of this peptide on the membrane is partially impaired. By these means, UNC119A is able to regulate c-Src spatially in the cytoplasm and on cellular membranes, and this has important implications for its cellular signaling.
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Affiliation(s)
- Nelli Erwin
- Physical Chemistry I, Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
| | - Mridula Dwivedi
- Physical Chemistry I, Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
| | - Tom Mejuch
- Department of Chemical Biology, Max-Plank-Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227, Dortmund, Germany
| | - Herbert Waldmann
- Department of Chemical Biology, Max-Plank-Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227, Dortmund, Germany
| | - Roland Winter
- Physical Chemistry I, Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Strasse 4a, 44227, Dortmund, Germany
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16
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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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17
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Birkholz O, Burns JR, Richter CP, Psathaki OE, Howorka S, Piehler J. Multi-functional DNA nanostructures that puncture and remodel lipid membranes into hybrid materials. Nat Commun 2018; 9:1521. [PMID: 29670084 PMCID: PMC5906680 DOI: 10.1038/s41467-018-02905-w] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 01/08/2018] [Indexed: 02/06/2023] Open
Abstract
Synthetically replicating key biological processes requires the ability to puncture lipid bilayer membranes and to remodel their shape. Recently developed artificial DNA nanopores are one possible synthetic route due to their ease of fabrication. However, an unresolved fundamental question is how DNA nanopores bind to and dynamically interact with lipid bilayers. Here we use single-molecule fluorescence microscopy to establish that DNA nanopores carrying cholesterol anchors insert via a two-step mechanism into membranes. Nanopores are furthermore shown to locally cluster and remodel membranes into nanoscale protrusions. Most strikingly, the DNA pores can function as cytoskeletal components by stabilizing autonomously formed lipid nanotubes. The combination of membrane puncturing and remodeling activity can be attributed to the DNA pores’ tunable transition between two orientations to either span or co-align with the lipid bilayer. This insight is expected to catalyze the development of future functional nanodevices relevant in synthetic biology and nanobiotechnology. DNA nanopores can span lipid bilayers but how they interact with lipids is not known. Here the authors establish at single-molecule level the insertion mechanism and show that DNA nanopores can locally cluster and remodel membranes, and stabilize autonomously formed lipid nanotubes.
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18
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Wu M, Alvarado JJ, Augelli-Szafran CE, Ptak RG, Smithgall TE. A single β-octyl glucoside molecule induces HIV-1 Nef dimer formation in the absence of partner protein binding. PLoS One 2018; 13:e0192512. [PMID: 29415006 PMCID: PMC5802939 DOI: 10.1371/journal.pone.0192512] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 01/24/2018] [Indexed: 01/05/2023] Open
Abstract
The HIV-1 Nef accessory protein is essential for viral pathogenicity and AIDS progression. Nef forms complexes with multiple host cell factors to facilitate viral replication and promote immune escape of HIV-infected cells. Previous X-ray crystal structures demonstrate that Nef forms homodimers, the orientation of which are influenced by host cell binding partners. In cell-based fluorescence complementation assays, Nef forms homodimers at the plasma membrane. However, recombinant Nef proteins often exist as monomers in solution, suggesting that membrane interaction may also trigger monomer to dimer transitions. In this study, we show that monomeric Nef core proteins can be induced to form dimers in the presence of low concentrations of the non-ionic surfactant, β-octyl glucoside (βOG). X-ray crystallography revealed that a single βOG molecule is present in the Nef dimer, with the 8-carbon acyl chain of the ligand binding to a hydrophobic pocket formed by the dimer interface. This Nef-βOG dimer interface involves helix αB, as observed in previous dimer structures, as well as a helix formed by N-terminal residues 54-66. Nef dimer formation is stabilized in solution by the addition of βOG, providing biochemical validation for the crystal structure. These observations together suggest that the interaction with host cell lipid mediators or other hydrophobic ligands may play a role in Nef dimerization, which has been previously linked to multiple Nef functions including host cell protein kinase activation, CD4 downregulation, and enhancement of HIV-1 replication.
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Affiliation(s)
- Mousheng Wu
- Department of Chemistry, Drug Discovery Division, Southern Research Institute, Birmingham, AL, United States of America
| | - John J. Alvarado
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Corinne E. Augelli-Szafran
- Department of Chemistry, Drug Discovery Division, Southern Research Institute, Birmingham, AL, United States of America
| | - Roger G. Ptak
- Department of Infectious Disease Research, Southern Research Institute, Frederick, MD, United States of America
| | - Thomas E. Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
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19
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Moroco JA, Alvarado JJ, Staudt RP, Shi H, Wales TE, Smithgall TE, Engen JR. Remodeling of HIV-1 Nef Structure by Src-Family Kinase Binding. J Mol Biol 2018; 430:310-321. [PMID: 29258818 PMCID: PMC5801098 DOI: 10.1016/j.jmb.2017.12.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/07/2017] [Accepted: 12/10/2017] [Indexed: 11/25/2022]
Abstract
The HIV-1 accessory protein Nef controls multiple aspects of the viral life cycle and host immune response, making it an attractive therapeutic target. Previous X-ray crystal structures of Nef in complex with key host cell binding partners have shed light on protein-protein interactions critical to Nef function. Crystal structures of Nef in complex with either the SH3 or tandem SH3-SH2 domains of Src-family kinases reveal distinct dimer conformations of Nef. However, the existence of these Nef dimer complexes in solution has not been established. Here we used hydrogen exchange mass spectrometry (HX MS) to compare the solution conformation of Nef alone and in complexes with the SH3 or the SH3-SH2 domains of the Src-family kinase Hck. HX MS revealed that interaction with the Hck SH3 or tandem SH3-SH2 domains induces protection of the Nef αB-helix from deuterium uptake, consistent with a role for αB in dimer formation. HX MS analysis of a Nef mutant (position Asp123, a site buried in the Nef:SH3 dimer but surface exposed in the Nef:SH3-SH2 complex), showed a Hck-induced conformational change in Nef relative to wild-type Nef. These results support a model in which Src-family kinase binding induces conformational changes in Nef to expose residues critical for interaction with the μ1 subunit of adaptor protein 1 and the major histocompatibility complex-1 tail, and subsequent major histocompatibility complex-1 downregulation and immune escape of HIV-infected cells required for functional interactions with downstream binding partners.
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Affiliation(s)
- Jamie A Moroco
- Department of Chemistry and Chemical Biology, Maildrop 412TF, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - John Jeff Alvarado
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 450 Technology Drive, Pittsburgh, PA 15219, USA.
| | - Ryan P Staudt
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 450 Technology Drive, Pittsburgh, PA 15219, USA.
| | - Haibin Shi
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 450 Technology Drive, Pittsburgh, PA 15219, USA.
| | - Thomas E Wales
- Department of Chemistry and Chemical Biology, Maildrop 412TF, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - Thomas E Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 450 Technology Drive, Pittsburgh, PA 15219, USA.
| | - John R Engen
- Department of Chemistry and Chemical Biology, Maildrop 412TF, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
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20
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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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Ray A, Jatana N, Thukral L. Lipidated proteins: Spotlight on protein-membrane binding interfaces. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 128:74-84. [DOI: 10.1016/j.pbiomolbio.2017.01.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 12/29/2016] [Accepted: 01/05/2017] [Indexed: 01/21/2023]
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22
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Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature. MEMBRANES 2017; 7:membranes7010015. [PMID: 28294967 PMCID: PMC5371976 DOI: 10.3390/membranes7010015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/07/2017] [Accepted: 03/11/2017] [Indexed: 12/11/2022]
Abstract
The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.
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Dirk BS, Van Nynatten LR, Dikeakos JD. Where in the Cell Are You? Probing HIV-1 Host Interactions through Advanced Imaging Techniques. Viruses 2016; 8:v8100288. [PMID: 27775563 PMCID: PMC5086620 DOI: 10.3390/v8100288] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/06/2016] [Accepted: 10/10/2016] [Indexed: 12/19/2022] Open
Abstract
Viruses must continuously evolve to hijack the host cell machinery in order to successfully replicate and orchestrate key interactions that support their persistence. The type-1 human immunodeficiency virus (HIV-1) is a prime example of viral persistence within the host, having plagued the human population for decades. In recent years, advances in cellular imaging and molecular biology have aided the elucidation of key steps mediating the HIV-1 lifecycle and viral pathogenesis. Super-resolution imaging techniques such as stimulated emission depletion (STED) and photoactivation and localization microscopy (PALM) have been instrumental in studying viral assembly and release through both cell-cell transmission and cell-free viral transmission. Moreover, powerful methods such as Forster resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) have shed light on the protein-protein interactions HIV-1 engages within the host to hijack the cellular machinery. Specific advancements in live cell imaging in combination with the use of multicolor viral particles have become indispensable to unravelling the dynamic nature of these virus-host interactions. In the current review, we outline novel imaging methods that have been used to study the HIV-1 lifecycle and highlight advancements in the cell culture models developed to enhance our understanding of the HIV-1 lifecycle.
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Affiliation(s)
- Brennan S Dirk
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada.
| | - Logan R Van Nynatten
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada.
| | - Jimmy D Dikeakos
- Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada.
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24
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Thukral L, Sengupta D, Ramkumar A, Murthy D, Agrawal N, Gokhale RS. The Molecular Mechanism Underlying Recruitment and Insertion of Lipid-Anchored LC3 Protein into Membranes. Biophys J 2016; 109:2067-78. [PMID: 26588566 DOI: 10.1016/j.bpj.2015.09.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 09/03/2015] [Accepted: 09/18/2015] [Indexed: 11/16/2022] Open
Abstract
Lipid modification of cytoplasmic proteins initiates membrane engagement that triggers diverse cellular processes. Despite the abundance of lipidated proteins in the human proteome, the key determinants underlying membrane recognition and insertion are poorly understood. Here, we define the course of spontaneous membrane insertion of LC3 protein modified with phosphatidylethanolamine using multiple coarse-grain simulations. The partitioning of the lipid anchor chains proceeds through a concerted process, with its two acyl chains inserting one after the other. Concurrently, a conformational rearrangement involving the α-helix III of LC3, especially in the three basic residues Lys65, Arg68, and Arg69, ensures stable insertion of the phosphatidylethanolamine anchor into membranes. Mutational studies validate the crucial role of these residues, and further live-cell imaging analysis shows a substantial reduction in the formation of autophagic vesicles for the mutant proteins. Our study captures the process of water-favored LC3 protein recruitment to the membrane and thus opens, to our knowledge, new avenues to explore the cellular dynamics underlying vesicular trafficking.
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Affiliation(s)
- Lipi Thukral
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India.
| | | | - Amrita Ramkumar
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - Divya Murthy
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - Nikhil Agrawal
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India
| | - Rajesh S Gokhale
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi, India.
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25
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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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26
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Affiliation(s)
- Anselm Sommer
- a Department of Dermatology , University of Kiel , Kiel , Germany
| | - Sucharit Bhakdi
- a Department of Dermatology , University of Kiel , Kiel , Germany
| | - Karina Reiss
- a Department of Dermatology , University of Kiel , Kiel , Germany
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27
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Pereira EA, daSilva LLP. HIV-1 Nef: Taking Control of Protein Trafficking. Traffic 2016; 17:976-96. [PMID: 27161574 DOI: 10.1111/tra.12412] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/05/2016] [Accepted: 05/05/2016] [Indexed: 12/25/2022]
Abstract
The Nef protein of the human immunodeficiency virus is a crucial determinant of viral pathogenesis and disease progression. Nef is abundantly expressed early in infection and is thought to optimize the cellular environment for viral replication. Nef controls expression levels of various cell surface molecules that play important roles in immunity and virus life cycle, by directly interfering with the itinerary of these proteins within the endocytic and late secretory pathways. To exert these functions, Nef physically interacts with host proteins that regulate protein trafficking. In recent years, considerable progress was made in identifying host-cell-interacting partners for Nef, and the molecular machinery used by Nef to interfere with protein trafficking has started to be unraveled. Here, we briefly review the knowledge gained and discuss new findings regarding the mechanisms by which Nef modifies the intracellular trafficking pathways to prevent antigen presentation, facilitate viral particle release and enhance the infectivity of HIV-1 virions.
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Affiliation(s)
- Estela A Pereira
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Luis L P daSilva
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
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28
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Sommer A, Kordowski F, Büch J, Maretzky T, Evers A, Andrä J, Düsterhöft S, Michalek M, Lorenzen I, Somasundaram P, Tholey A, Sönnichsen FD, Kunzelmann K, Heinbockel L, Nehls C, Gutsmann T, Grötzinger J, Bhakdi S, Reiss K. Phosphatidylserine exposure is required for ADAM17 sheddase function. Nat Commun 2016; 7:11523. [PMID: 27161080 PMCID: PMC4866515 DOI: 10.1038/ncomms11523] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 04/05/2016] [Indexed: 02/07/2023] Open
Abstract
ADAM17, a prominent member of the 'Disintegrin and Metalloproteinase' (ADAM) family, controls vital cellular functions through cleavage of transmembrane substrates. Here we present evidence that surface exposure of phosphatidylserine (PS) is pivotal for ADAM17 to exert sheddase activity. PS exposure is tightly coupled to substrate shedding provoked by diverse ADAM17 activators. PS dependency is demonstrated in the following: (a) in Raji cells undergoing apoptosis; (b) in mutant PSA-3 cells with manipulatable PS content; and (c) in Scott syndrome lymphocytes genetically defunct in their capacity to externalize PS in response to intracellular Ca(2+) elevation. Soluble phosphorylserine but not phosphorylcholine inhibits substrate cleavage. The isolated membrane proximal domain (MPD) of ADAM17 binds to PS but not to phosphatidylcholine liposomes. A cationic PS-binding motif is identified in this domain, replacement of which abrogates liposome-binding and renders the protease incapable of cleaving its substrates in cells. We speculate that surface-exposed PS directs the protease to its targets where it then executes its shedding function.
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Affiliation(s)
- Anselm Sommer
- Department of Dermatology, University of Kiel, Schittenhelmstrasse 7, Kiel 24105, Germany
| | - Felix Kordowski
- Department of Dermatology, University of Kiel, Schittenhelmstrasse 7, Kiel 24105, Germany
| | - Joscha Büch
- Department of Dermatology, University of Kiel, Schittenhelmstrasse 7, Kiel 24105, Germany
| | - Thorsten Maretzky
- Arthritis and Tissue Degeneration Program, Hospital for Special Surgery at Weill Medical College of Cornell University, New York, New York 10021, USA
| | - Astrid Evers
- Arthritis and Tissue Degeneration Program, Hospital for Special Surgery at Weill Medical College of Cornell University, New York, New York 10021, USA
| | - Jörg Andrä
- Hamburg University of Applied Science, Ulmenliet 20, Hamburg 21033, Germany
| | - Stefan Düsterhöft
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, Kiel 24098, Germany
| | - Matthias Michalek
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, Kiel 24098, Germany
| | - Inken Lorenzen
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, Kiel 24098, Germany
| | - Prasath Somasundaram
- Division of Systematic Proteome Research and Bioanalytics, Institute for Experimental Medicine, University of Kiel, Kiel 24105, Germany
| | - Andreas Tholey
- Division of Systematic Proteome Research and Bioanalytics, Institute for Experimental Medicine, University of Kiel, Kiel 24105, Germany
| | - Frank D Sönnichsen
- Otto Diels Institute for Organic Chemistry, University of Kiel, Kiel 24118, Germany
| | - Karl Kunzelmann
- Physiological Institute, University of Regensburg, Universitätsstrasse 31, Regensburg 93053, Germany
| | - Lena Heinbockel
- Forschungszentrum Borstel, Leibniz-Zentrum für Medizin and Biowissenschaften, Borstel 23845, Germany
| | - Christian Nehls
- Forschungszentrum Borstel, Leibniz-Zentrum für Medizin and Biowissenschaften, Borstel 23845, Germany
| | - Thomas Gutsmann
- Forschungszentrum Borstel, Leibniz-Zentrum für Medizin and Biowissenschaften, Borstel 23845, Germany
| | - Joachim Grötzinger
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, Kiel 24098, Germany
| | - Sucharit Bhakdi
- Department of Dermatology, University of Kiel, Schittenhelmstrasse 7, Kiel 24105, Germany
| | - Karina Reiss
- Department of Dermatology, University of Kiel, Schittenhelmstrasse 7, Kiel 24105, Germany
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29
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Membrane lipid compositional sensing by the inducible amphipathic helix of CCT. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1861:847-861. [PMID: 26747646 DOI: 10.1016/j.bbalip.2015.12.022] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/22/2015] [Accepted: 12/29/2015] [Indexed: 11/21/2022]
Abstract
The amphipathic helical (AH) membrane binding motif is recognized as a major device for lipid compositional sensing. We explore the function and mechanism of sensing by the lipid biosynthetic enzyme, CTP:phosphocholine cytidylyltransferase (CCT). As the regulatory enzyme in phosphatidylcholine (PC) synthesis, CCT contributes to membrane PC homeostasis. CCT directly binds and inserts into the surface of bilayers that are deficient in PC and therefore enriched in lipids that enhance surface charge and/or create lipid packing voids. These two membrane physical properties induce the folding of the CCT M domain into a ≥60 residue AH. Membrane binding activates catalysis by a mechanism that has been partially deciphered. We review the evidence for CCT compositional sensing, and the membrane and protein determinants for lipid selective membrane-interactions. We consider the factors that promote the binding of CCT isoforms to the membranes of the ER, nuclear envelope, or lipid droplets, but exclude CCT from other organelles and the plasma membrane. The CCT sensing mechanism is compared with several other proteins that use an AH motif for membrane compositional sensing. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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30
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Suladze S, Cinar S, Sperlich B, Winter R. Pressure Modulation of the Enzymatic Activity of Phospholipase A2, A Putative Membrane-Associated Pressure Sensor. J Am Chem Soc 2015; 137:12588-96. [DOI: 10.1021/jacs.5b07009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Saba Suladze
- Department of Chemistry and
Chemical Biology, Biophysical Chemistry, TU Dortmund University, Otto-Hahn-Str. 6, D-44221 Dortmund, Germany
| | - Suleyman Cinar
- Department of Chemistry and
Chemical Biology, Biophysical Chemistry, TU Dortmund University, Otto-Hahn-Str. 6, D-44221 Dortmund, Germany
| | - Benjamin Sperlich
- Department of Chemistry and
Chemical Biology, Biophysical Chemistry, TU Dortmund University, Otto-Hahn-Str. 6, D-44221 Dortmund, Germany
| | - Roland Winter
- Department of Chemistry and
Chemical Biology, Biophysical Chemistry, TU Dortmund University, Otto-Hahn-Str. 6, D-44221 Dortmund, Germany
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31
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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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32
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Luo X, Fan Y, Park IW, He JJ. Exosomes are unlikely involved in intercellular Nef transfer. PLoS One 2015; 10:e0124436. [PMID: 25919665 PMCID: PMC4412529 DOI: 10.1371/journal.pone.0124436] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 03/13/2015] [Indexed: 11/18/2022] Open
Abstract
HIV-1 Nef is an important pathogenic factor for HIV/AIDS pathogenesis. Several recent studies including ours have demonstrated that Nef can be transferred to neighboring cells and alters the function of these cells. However, how the intercellular Nef transfer occurs is in dispute. In the current study, we attempted to address this important issue using several complementary strategies, a panel of exosomal markers, and human CD4+ T lymphocyte cell line Jurkat and a commonly used cell line 293T. First, we showed that Nef was transferred from Nef-expressing or HIV-infected Jurkat to naïve Jurkat and other non-Jurkat cells and that the transfer required the membrane targeting function of Nef and was cell density-dependent. Then, we showed that Nef transfer was cell-cell contact-dependent, as exposure to culture supernatants or exosomes from HIV-infected Jurkat or Nef-expressing Jurkat and 293T led to little Nef detection in the target cells Jurkat. Thirdly, we demonstrated that Nef was only detected to be associated with HIV virions but not with acetylcholinesterase (AChE+) exosomes from HIV-infected Jurkat and not in the exosomes from Nef-expressing Jurkat. In comparison, when it was over-expressed in 293T, Nef was detected in detergent-insoluble AChE+/CD81low/TSG101low exosomes, but not in detergent-soluble AChE-/CD81high/TSG101high exosomes. Lastly, microscopic imaging showed no significant Nef detection in exosomal vesicle-like structures in and out 293T. Taken together, these results show that exosomes are unlikely involved in intercellular Nef transfer. In addition, this study reveals existence of two types of exosomes: AChE+/CD81low/TSG101low exosomes and AChE-/CD81high/TSG101high exosomes.
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Affiliation(s)
- Xiaoyu Luo
- Department of Cell Biology and Immunology, Graduate School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, Texas, 76107, United States of America
| | - Yan Fan
- Department of Cell Biology and Immunology, Graduate School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, Texas, 76107, United States of America
| | - In-Woo Park
- Department of Cell Biology and Immunology, Graduate School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, Texas, 76107, United States of America
| | - Johnny J. He
- Department of Cell Biology and Immunology, Graduate School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, Texas, 76107, United States of America
- * E-mail:
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33
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Ghosh R, de Campos MKF, Huang J, Huh SK, Orlowski A, Yang Y, Tripathi A, Nile A, Lee HC, Dynowski M, Schäfer H, Róg T, Lete MG, Ahyayauch H, Alonso A, Vattulainen I, Igumenova TI, Schaaf G, Bankaitis VA. Sec14-nodulin proteins and the patterning of phosphoinositide landmarks for developmental control of membrane morphogenesis. Mol Biol Cell 2015; 26:1764-81. [PMID: 25739452 PMCID: PMC4436786 DOI: 10.1091/mbc.e14-10-1475] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/26/2015] [Indexed: 12/12/2022] Open
Abstract
A Sec14-nodulin protein model is used to identify the nodulin domain as a novel phosphoinositide effector module with a role in controlling lateral organization of phosphoinositide. The domain organization of Sec14-nodulin proteins suggests a versatile principle for the bit mapping of membrane surfaces into high-definition lipid-signaling screens. Polarized membrane morphogenesis is a fundamental activity of eukaryotic cells. This process is essential for the biology of cells and tissues, and its execution demands exquisite temporal coordination of functionally diverse membrane signaling reactions with high spatial resolution. Moreover, mechanisms must exist to establish and preserve such organization in the face of randomizing forces that would diffuse it. Here we identify the conserved AtSfh1 Sec14-nodulin protein as a novel effector of phosphoinositide signaling in the extreme polarized membrane growth program exhibited by growing Arabidopsis root hairs. The data are consistent with Sec14-nodulin proteins controlling the lateral organization of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) landmarks for polarized membrane morphogenesis in plants. This patterning activity requires both the PtdIns(4,5)P2 binding and homo-oligomerization activities of the AtSfh1 nodulin domain and is an essential aspect of the polarity signaling program in root hairs. Finally, the data suggest a general principle for how the phosphoinositide signaling landscape is physically bit mapped so that eukaryotic cells are able to convert a membrane surface into a high-definition lipid-signaling screen.
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Affiliation(s)
- Ratna Ghosh
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843
| | - Marília K F de Campos
- Center for Plant Molecular Biology, Plant Physiology, Universität Tübingen, 72076 Tübingen, Germany
| | - Jin Huang
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843
| | - Seong K Huh
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843
| | - Adam Orlowski
- Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland
| | - Yuan Yang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843
| | - Ashutosh Tripathi
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843
| | - Aaron Nile
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843
| | - Hsin-Chieh Lee
- Center for Plant Molecular Biology, Plant Physiology, Universität Tübingen, 72076 Tübingen, Germany
| | - Marek Dynowski
- Zentrum für Datenverarbeitung, Universität Tübingen, 72074 Tübingen, Germany
| | - Helen Schäfer
- Center for Plant Molecular Biology, Plant Physiology, Universität Tübingen, 72076 Tübingen, Germany
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland
| | - Marta G Lete
- Unidad de Biofísica (CSIC, UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, 48940 Leioa, Spain
| | - Hasna Ahyayauch
- Unidad de Biofísica (CSIC, UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, 48940 Leioa, Spain Institut de Formation aux Carrieres de Sante de Rabat, 10000 Rabat, Morocco
| | - Alicia Alonso
- Unidad de Biofísica (CSIC, UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, 48940 Leioa, Spain
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843
| | - Gabriel Schaaf
- Center for Plant Molecular Biology, Plant Physiology, Universität Tübingen, 72076 Tübingen, Germany
| | - Vytas A Bankaitis
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Sciences Center, Texas A&M University, College Station, TX 77843 Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843 Department of Chemistry, Texas A&M University, College Station, TX 77843
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34
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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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Zens B, Sawa-Makarska J, Martens S. In vitro systems for Atg8 lipidation. Methods 2014; 75:37-43. [PMID: 25461810 PMCID: PMC4358837 DOI: 10.1016/j.ymeth.2014.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 01/24/2023] Open
Abstract
Atg8 lipidation can be efficiently reconstituted in vitro. Lipidation and de-lipidation of Atg8 by Atg4 can be analyzed. Reconstitution of Atg8-lipidation using giant unilamellar vesicles offers spatial insights. These assays allow determining the effect of modifications on Atg8 lipidation/de-lipidation.
Macroautophagy is a major bulk degradation pathway for cytoplasmic material in eukaryotic cells. During macroautophagy, double membrane-bound organelles called autophagosomes are formed in a de novo manner. In the course of their formation autophagosomes capture cytoplasmic material, which is subsequently degraded upon fusion with the lysosomal system in complex eukaryotes or the vacuole in yeast. Several proteins are required for autophagosome formation. Among these are the components of two ubiquitin-like conjugation reactions that collectively mediate the conjugation of the ubiquitin-like Atg12 to the Atg5 protein and of the ubiquitin-like protein Atg8 to the headgroup of the membrane lipid phosphatidylethanolamine. The lipidated form of Atg8 is membrane-bound and marks the growing autophagosomal membrane as well as the completed autophagosome. Here we describe assays for the in vitro reconstitution of the Atg8 lipidation reaction using recombinantly expressed and purified proteins derived from Saccharomycescerevisiae in combination with small and giant unilamellar vesicles. The assays enable the study of the biochemical mechanisms of action of the Atg8 lipidation machinery and to analyze the impact of mutations and post-translational modifications of the conjugation machinery on Atg8 lipidation.
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Affiliation(s)
- Bettina Zens
- Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Justyna Sawa-Makarska
- Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Sascha Martens
- Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria.
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Chu NK, Shabbir W, Bove-Fenderson E, Araman C, Lemmens-Gruber R, Harris DA, Becker CFW. A C-terminal membrane anchor affects the interactions of prion proteins with lipid membranes. J Biol Chem 2014; 289:30144-60. [PMID: 25217642 DOI: 10.1074/jbc.m114.587345] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Membrane attachment via a C-terminal glycosylphosphatidylinositol anchor is critical for conversion of PrP(C) into pathogenic PrP(Sc). Therefore the effects of the anchor on PrP structure and function need to be deciphered. Three PrP variants, including full-length PrP (residues 23-231, FL_PrP), N-terminally truncated PrP (residues 90-231, T_PrP), and PrP missing its central hydrophobic region (Δ105-125, ΔCR_PrP), were equipped with a C-terminal membrane anchor via a semisynthesis strategy. Analyses of the interactions of lipidated PrPs with phospholipid membranes demonstrated that C-terminal membrane attachment induces a different binding mode of PrP to membranes, distinct from that of non-lipidated PrPs, and influences the biochemical and conformational properties of PrPs. Additionally, fluorescence-based assays indicated pore formation by lipidated ΔCR_PrP, a variant that is known to be highly neurotoxic in transgenic mice. This finding was supported by using patch clamp electrophysiological measurements of cultured cells. These results provide new evidence for the role of the membrane anchor in PrP-lipid interactions, highlighting the importance of the N-terminal and the central hydrophobic domain in these interactions.
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Affiliation(s)
- Nam K Chu
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria
| | - Waheed Shabbir
- the Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, and
| | - Erin Bove-Fenderson
- the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Can Araman
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria
| | - Rosa Lemmens-Gruber
- the Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, and
| | - David A Harris
- the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Christian F W Becker
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria,
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Biophysical investigations with MARCKS-ED: dissecting the molecular mechanism of its curvature sensing behaviors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:3137-3144. [PMID: 25195712 DOI: 10.1016/j.bbamem.2014.08.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 08/24/2014] [Accepted: 08/27/2014] [Indexed: 11/21/2022]
Abstract
Curved membranes are a common and important attribute in cells. Protein and peptide curvature sensors are known to activate signaling pathways, initiate vesicle budding, trigger membrane fusion, and facilitate molecular transport across cell membranes. Nonetheless, there is little understanding how these proteins and peptides achieve preferential binding of different membrane curvatures. The current study is to elucidate specific factors required for curvature sensing. As a model system, we employed a recently identified peptide curvature sensor, MARCKS-ED, derived from the effector domain of the myristoylated alanine-rich C kinase substrate protein, for these biophysical investigations. An atomistic molecular dynamics (MD) simulation suggested an important role played by the insertion of the Phe residues within MARCKS-ED. To test these observations from our computational simulations, we performed electron paramagnetic resonance (EPR) studies to determine the insertion depth of MARCKS-ED into differently curved membrane bilayers. Next, studies with varied lipid compositions revealed their influence on curvature sensing by MARCKS-ED, suggesting contributions from membrane fluidity, rigidity, as well as various lipid structures. Finally, we demonstrated that the curvature sensing by MARCKS-ED is configuration independent. In summary, our studies have shed further light to the understanding of how MARCKS-ED differentiates between membrane curvatures, which may be generally applicable to protein curvature sensing behavior.
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38
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Geist MM, Pan X, Bender S, Bartenschlager R, Nickel W, Fackler OT. Heterologous Src homology 4 domains support membrane anchoring and biological activity of HIV-1 Nef. J Biol Chem 2014; 289:14030-44. [PMID: 24706755 DOI: 10.1074/jbc.m114.563528] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The HIV-1 pathogenicity factor Nef enhances viral replication by modulation of multiple host cell transport and signaling pathways. Nef associates with membranes via an N-terminal Src homology 4 (SH4) domain, and membrane association is believed to be essential for its biological functions. At which subcellular site(s) Nef exerts its different functions and how kinetics of membrane interactions contribute to its biological activity are unknown. To address how specific characteristics of Nef membrane association affect its biological properties, the SH4 domain of Nef was replaced by heterologous membrane targeting domains. The use of a panel of heterologous SH4 domains resulted in chimeric Nef proteins with distinct steady state subcellular localization, membrane association efficiency, and anterograde transport routes. Irrespective of these modifications, cardinal Nef functions affecting host cell vesicular transport and actin dynamics were fully preserved. In contrast, stable targeting of Nef to the surface of mitochondria, peroxisomes, or the Golgi apparatus, and thus prevention of plasma membrane delivery, caused potent and broad loss of Nef activity. These results support the concept that Nef adopts its active conformation in the membrane-associated state but exclude that membrane-associated Nef simply acts by recruiting soluble factors independently of its local microenvironment. Rather than its steady state subcellular localization or membrane affinity, the ability to undergo dynamic anterograde and internalization cycles appear to determine Nef function. These results reveal that functional membrane interactions of Nef underlie critical spatiotemporal regulation and suggest that delivery to distinct subcellular sites via such transport cycles provides the basis for the multifunctionality of Nef.
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Affiliation(s)
- Miriam M Geist
- From the Department of Infectious Diseases, Integrative Virology and
| | - Xiaoyu Pan
- From the Department of Infectious Diseases, Integrative Virology and
| | - Silke Bender
- Molecular Virology, University Hospital Heidelberg,69120 Heidelberg, Germany and
| | - Ralf Bartenschlager
- Molecular Virology, University Hospital Heidelberg,69120 Heidelberg, Germany and
| | - Walter Nickel
- the Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Oliver T Fackler
- From the Department of Infectious Diseases, Integrative Virology and
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Black JC, Cheney PP, Campbell T, Knowles MK. Membrane curvature based lipid sorting using a nanoparticle patterned substrate. SOFT MATTER 2014; 10:2016-23. [PMID: 24652483 DOI: 10.1039/c3sm52522h] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Cellular membranes contain a variety of shapes that likely act as motifs for sorting lipids and proteins. To understand the sorting that takes place within cells, a continuous, fluid bilayer with regions of membrane curvature was designed and characterized using confocal fluorescence and total internal reflection fluorescence microscopy techniques. A supported lipid bilayer was formed over fluorescently labelled nanoparticles deposited on a glass surface. The lipid composition and membrane shape are separately controlled and the nanoparticle dimensions (d = 40-200 nm) determine the extent of curvature. The bulk membrane is fluid as demonstrated by fluorescence recovery after photobleaching (FRAP) using dye labelled lipids. In bilayers that contain fluorescently labelled, single-tailed lipids, accumulation is observed at regions of curvature, yet the molecules retain fluidity. Using single particle imaging methods, lipids are observed to visit regions of curvature and exchange with the surrounding flat membrane. The nanoparticle patterned substrate described here allows for quantitative measurement of the transient interactions between fluorescently labelled biomolecules and regions of membrane curvature.
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Affiliation(s)
- Joshua C Black
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA.
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40
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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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41
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Li L, Shi X, Guo X, Li H, Xu C. Ionic protein–lipid interaction at the plasma membrane: what can the charge do? Trends Biochem Sci 2014; 39:130-40. [DOI: 10.1016/j.tibs.2014.01.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 01/13/2014] [Accepted: 01/14/2014] [Indexed: 11/30/2022]
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Rösner HI, Kragelund BB. Structure and dynamic properties of membrane proteins using NMR. Compr Physiol 2013; 2:1491-539. [PMID: 23798308 DOI: 10.1002/cphy.c110036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Integral membrane proteins are one of the most challenging groups of macromolecules despite their apparent conformational simplicity. They manage and drive transport, circulate information, and participate in cellular movements via interactions with other proteins and through intricate conformational changes. Their structural and functional decoding is challenging and has imposed demanding experimental development. Solution nuclear magnetic resonance (NMR) spectroscopy is one of the techniques providing the capacity to make a significant difference in the deciphering of the membrane protein structure-function paradigm. The method has evolved dramatically during the last decade resulting in a plethora of new experiments leading to a significant increase in the scientific repertoire for studying membrane proteins. Besides solving the three-dimensional structures using state-of-the-art approaches, a large variety of developments of well-established techniques are available providing insight into membrane protein flexibility, dynamics, and interactions. Inspired by the speed of development in the application of new strategies, by invention of methods to measure solvent accessibility and describe low-populated states, this review seeks to introduce the vast possibilities solution NMR can offer to the study of membrane protein structure-function analyses with special focus on applicability.
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Affiliation(s)
- Heike I Rösner
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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43
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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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44
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Lamers SL, Fogel GB, Singer EJ, Salemi M, Nolan DJ, Huysentruyt LC, McGrath MS. HIV-1 Nef in macrophage-mediated disease pathogenesis. Int Rev Immunol 2013; 31:432-50. [PMID: 23215766 DOI: 10.3109/08830185.2012.737073] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Combined anti-retroviral therapy (cART) has significantly reduced the number of AIDS-associated illnesses and changed the course of HIV-1 disease in developed countries. Despite the ability of cART to maintain high CD4+ T-cell counts, a number of macrophage-mediated diseases can still occur in HIV-infected subjects. These diseases include lymphoma, metabolic diseases, and HIV-associated neurological disorders. Within macrophages, the HIV-1 regulatory protein "Nef" can modulate surface receptors, interact with signaling pathways, and promote specific environments that contribute to each of these pathologies. Moreover, genetic variation in Nef may also guide the macrophage response. Herein, we review findings relating to the Nef-macrophage interaction and how this relationship contributes to disease pathogenesis.
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45
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Capraro BR, Shi Z, Wu T, Chen Z, Dunn JM, Rhoades E, Baumgart T. Kinetics of endophilin N-BAR domain dimerization and membrane interactions. J Biol Chem 2013; 288:12533-43. [PMID: 23482561 DOI: 10.1074/jbc.m112.435511] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The recruitment to plasma membrane invaginations of the protein endophilin is a temporally regulated step in clathrin-mediated endocytosis. Endophilin is believed to sense or stabilize membrane curvature, which in turn likely depends on the dimeric structure of the protein. The dynamic nature of the membrane association and dimerization of endophilin is thus functionally important and is illuminated herein. Using subunit exchange Förster resonance energy transfer (FRET), we determine dimer dissociation kinetics and find a dimerization equilibrium constant orders of magnitude lower than previously published values. We characterize N-BAR domain membrane association kinetics under conditions where the dimeric species predominates, by stopped flow, observing prominent electrostatic sensitivity of membrane interaction kinetics. Relative to membrane binding, we find that protein monomer/dimer species equilibrate with far slower kinetics. Complementary optical microscopy studies reveal strikingly slow membrane dissociation and an increase of dissociation rate constant for a construct lacking the amphipathic segment helix 0 (H0). We attribute the slow dissociation kinetics to higher-order protein oligomerization on the membrane. We incorporate our findings into a kinetic scheme for endophilin N-BAR membrane binding and find a significant separation of time scales for endophilin membrane binding and subsequent oligomerization. This separation may facilitate the regulation of membrane trafficking phenomena.
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Affiliation(s)
- Benjamin R Capraro
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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46
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Ras GTPase activating (RasGAP) activity of the dual specificity GAP protein Rasal requires colocalization and C2 domain binding to lipid membranes. Proc Natl Acad Sci U S A 2012; 110:111-6. [PMID: 23251034 DOI: 10.1073/pnas.1201658110] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Rasal, belonging to the GAP1 subfamily of Ras GTPase-activating proteins (RasGAPs) with dual RasGAP/RapGAP specificity, is epigenetically silenced in several tumor types. Surprisingly, the isolated protein has GAP activity on Rap but not on Ras. Its membrane recruitment is regulated by interaction with calcium and lipids, which simultaneously induces its RasGAP activity through a yet unknown mechanism. Here we show that the interaction of Rasal with membranes induces Rasal RasGAP activity by spatial and conformational regulation, although it does not have any effect on its RapGAP activity. Not only is colocalization of Rasal and Ras in the membrane essential for RasGAP activation, but direct and Ca-dependent interaction between the tandem C2 domains of Rasal and lipids of the membrane is also required. Whereas the C2A domain binds specifically phosphatidylserine, the C2B domain interacts with several phosphoinositol lipids. Finally we show, that similar to the C2 domains of synaptotagmins, the Rasal tandem C2 domains are able to sense and induce membrane curvature by the insertion of hydrophobic loops into the membrane.
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47
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Schramm CA, Hannigan BT, Donald JE, Keasar C, Saven JG, Degrado WF, Samish I. Knowledge-based potential for positioning membrane-associated structures and assessing residue-specific energetic contributions. Structure 2012; 20:924-35. [PMID: 22579257 DOI: 10.1016/j.str.2012.03.016] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 02/28/2012] [Accepted: 03/07/2012] [Indexed: 01/27/2023]
Abstract
The complex hydrophobic and hydrophilic milieus of membrane-associated proteins pose experimental and theoretical challenges to their understanding. Here, we produce a nonredundant database to compute knowledge-based asymmetric cross-membrane potentials from the per-residue distributions of C(β), C(γ) and functional group atoms. We predict transmembrane and peripherally associated regions from genomic sequence and position peptides and protein structures relative to the bilayer (available at http://www.degradolab.org/ez). The pseudo-energy topological landscapes underscore positional stability and functional mechanisms demonstrated here for antimicrobial peptides, transmembrane proteins, and viral fusion proteins. Moreover, experimental effects of point mutations on the relative ratio changes of dual-topology proteins are quantitatively reproduced. The functional group potential and the membrane-exposed residues display the largest energetic changes enabling to detect native-like structures from decoys. Hence, focusing on the uniqueness of membrane-associated proteins and peptides, we quantitatively parameterize their cross-membrane propensity, thus facilitating structural refinement, characterization, prediction, and design.
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Affiliation(s)
- Chaim A Schramm
- Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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48
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Membrane binding of Escherichia coli RNase E catalytic domain stabilizes protein structure and increases RNA substrate affinity. Proc Natl Acad Sci U S A 2012; 109:7019-24. [PMID: 22509045 DOI: 10.1073/pnas.1120181109] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RNase E plays an essential role in RNA processing and decay and tethers to the cytoplasmic membrane in Escherichia coli; however, the function of this membrane-protein interaction has remained unclear. Here, we establish a mechanistic role for the RNase E-membrane interaction. The reconstituted highly conserved N-terminal fragment of RNase E (NRne, residues 1-499) binds specifically to anionic phospholipids through electrostatic interactions. The membrane-binding specificity of NRne was confirmed using circular dichroism difference spectroscopy; the dissociation constant (K(d)) for NRne binding to anionic liposomes was 298 nM. E. coli RNase G and RNase E/G homologs from phylogenetically distant Aquifex aeolicus, Haemophilus influenzae Rd, and Synechocystis sp. were found to be membrane-binding proteins. Electrostatic potentials of NRne and its homologs were found to be conserved, highly positive, and spread over a large surface area encompassing four putative membrane-binding regions identified in the "large" domain (amino acids 1-400, consisting of the RNase H, S1, 5'-sensor, and DNase I subdomains) of E. coli NRne. In vitro cleavage assay using liposome-free and liposome-bound NRne and RNA substrates BR13 and GGG-RNAI showed that NRne membrane binding altered its enzymatic activity. Circular dichroism spectroscopy showed no obvious thermotropic structural changes in membrane-bound NRne between 10 and 60 °C, and membrane-bound NRne retained its normal cleavage activity after cooling. Thus, NRne membrane binding induced changes in secondary protein structure and enzymatic activation by stabilizing the protein-folding state and increasing its binding affinity for its substrate. Our results demonstrate that RNase E-membrane interaction enhances the rate of RNA processing and decay.
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Dikeakos JD, Thomas L, Kwon G, Elferich J, Shinde U, Thomas G. An interdomain binding site on HIV-1 Nef interacts with PACS-1 and PACS-2 on endosomes to down-regulate MHC-I. Mol Biol Cell 2012; 23:2184-97. [PMID: 22496420 PMCID: PMC3364181 DOI: 10.1091/mbc.e11-11-0928] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
HIV-1 Nef pirates PACS-1 and PACS-2 to downregulate MHC-I, but little is known about the Nef–PACS interaction. The sites on Nef and the PACS proteins required for their interaction are identified, and their importance for Nef trafficking and Nef-induced MHC-I downregulation is discussed. The results provide insight into the molecular basis of Nef action. The human immunodeficiency virus type 1 (HIV-1) accessory protein Nef directs virus escape from immune surveillance by subverting host cell intracellular signaling and membrane traffic to down-regulate cell-surface major histocompatibility complex class I (MHC-I). The interaction of Nef with the sorting proteins PACS-1 and PACS-2 mediates key signaling and trafficking steps required for Nef-mediated MHC-I down-regulation. Little is known, however, about the molecular basis underlying the Nef–PACS interaction. Here we identify the sites on Nef and the PACS proteins required for their interaction and describe the consequences of disrupting this interaction for Nef action. A previously unidentified cargo subsite on PACS-1 and PACS-2 interacted with a bipartite site on Nef formed by the EEEE65 acidic cluster on the N-terminal domain and W113 in the core domain. Mutation of these sites prevented the interaction between Nef and the PACS proteins on Rab5 (PACS-2 and PACS-1)- or Rab7 (PACS-1)-positive endosomes as determined by bimolecular fluorescence complementation and caused a Nef mutant defective in PACS binding to localize to distorted endosomal compartments. Consequently, disruption of the Nef–PACS interaction repressed Nef-induced MHC-I down-regulation in peripheral blood mononuclear cells. Our results provide insight into the molecular basis of Nef action and suggest new strategies to combat HIV-1.
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Affiliation(s)
- Jimmy D Dikeakos
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
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50
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Xue B, Mizianty MJ, Kurgan L, Uversky VN. Protein intrinsic disorder as a flexible armor and a weapon of HIV-1. Cell Mol Life Sci 2012; 69:1211-59. [PMID: 22033837 PMCID: PMC11114566 DOI: 10.1007/s00018-011-0859-3] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 09/28/2011] [Accepted: 10/03/2011] [Indexed: 01/19/2023]
Abstract
Many proteins and protein regions are disordered in their native, biologically active states. These proteins/regions are abundant in different organisms and carry out important biological functions that complement the functional repertoire of ordered proteins. Viruses, with their highly compact genomes, small proteomes, and high adaptability for fast change in their biological and physical environment utilize many of the advantages of intrinsic disorder. In fact, viral proteins are generally rich in intrinsic disorder, and intrinsically disordered regions are commonly used by viruses to invade the host organisms, to hijack various host systems, and to help viruses in accommodation to their hostile habitats and to manage their economic usage of genetic material. In this review, we focus on the structural peculiarities of HIV-1 proteins, on the abundance of intrinsic disorder in viral proteins, and on the role of intrinsic disorder in their functions.
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Affiliation(s)
- Bin Xue
- Department of Molecular Medicine, University of South Florida, College of Medicine, 12901 Bruce B. Downs Blvd, MDC07, Tampa, FL 33612 USA
| | - Marcin J. Mizianty
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 2V4 Canada
| | - Lukasz Kurgan
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 2V4 Canada
| | - Vladimir N. Uversky
- Department of Molecular Medicine, University of South Florida, College of Medicine, 12901 Bruce B. Downs Blvd, MDC07, Tampa, FL 33612 USA
- Institute for Biological Instrumentation, Russian Academy of Sciences, 142290 Pushchino, Moscow Region Russia
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