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Gaisina I, Li P, Du R, Cui Q, Dong M, Zhang C, Manicassamy B, Caffrey M, Moore T, Cooper L, Rong L. An orally active entry inhibitor of influenza A viruses protects mice and synergizes with oseltamivir and baloxavir marboxil. Sci Adv 2024; 10:eadk9004. [PMID: 38394202 PMCID: PMC10889430 DOI: 10.1126/sciadv.adk9004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Accepted: 01/22/2024] [Indexed: 02/25/2024]
Abstract
Seasonal or pandemic illness caused by influenza A viruses (IAVs) is a major public health concern due to the high morbidity and notable mortality. Although there are several approved drugs targeting different mechanisms, the emergence of drug resistance calls for new drug candidates that can be used alone or in combinations. Small-molecule IAV entry inhibitor, ING-1466, binds to hemagglutinin (HA) and blocks HA-mediated viral infection. Here, we show that this inhibitor demonstrates preventive and therapeutic effects in a mouse model of IAV with substantial improvement in the survival rate. When administered orally it elicits a therapeutic effect in mice, even after the well-established infection. Moreover, the combination of ING-1466 with oseltamivir phosphate or baloxavir marboxil enhances the therapeutic effect in a synergistic manner. Overall, ING-1466 has excellent oral bioavailability and in vitro absorption, distribution, metabolism, excretion, and toxicity profile, suggesting that it can be developed for monotherapy or combination therapy for the treatment of IAV infections.
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Affiliation(s)
- Irina Gaisina
- Department of Pharmaceutical Sciences, College of Pharmacy and UICentre, University of Illinois at Chicago, Chicago, IL 60612, USA
- Chicago BioSolutions Inc., Chicago, IL 60612, USA
| | - Ping Li
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
| | - Ruikun Du
- Innovation Research Institute of Traditional Chinese Medicine, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
| | - Qinghua Cui
- Innovation Research Institute of Traditional Chinese Medicine, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
| | - Meiyue Dong
- Innovation Research Institute of Traditional Chinese Medicine, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
| | - Chengcheng Zhang
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, Shandong 250355, China
| | - Balaji Manicassamy
- Department of Microbiology and Immunology, College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Terry Moore
- Department of Pharmaceutical Sciences, College of Pharmacy and UICentre, University of Illinois at Chicago, Chicago, IL 60612, USA
- University of Illinois Cancer Center, University of Illinois at Chicago, Chicago, IL 26 60612, USA
| | - Laura Cooper
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Lijun Rong
- Chicago BioSolutions Inc., Chicago, IL 60612, USA
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
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Caffrey M, Jayakumar N, Caffrey V, Anirudan V, Rong L, Paprotny I. VLP-Based Model for Study of Airborne Viral Pathogens. bioRxiv 2024:2024.01.03.574055. [PMID: 38260552 PMCID: PMC10802359 DOI: 10.1101/2024.01.03.574055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The recent COVID-19 pandemic has underscored the danger of airborne viral pathogens. The lack of model systems to study airborne pathogens limits the understanding of airborne pathogen distribution, as well as potential surveillance and mitigation strategies. In this work, we develop a novel model system to study airborne pathogens using virus like particles (VLP). Specifically, we demonstrate the ability to aerosolize VLP and detect and quantify aerosolized VLP RNA by Reverse Transcription-Loop-Mediated Isothermal Amplification (RT-LAMP) in real-time fluorescent and colorimetric assays. Importantly, the VLP model presents many advantages for the study of airborne viral pathogens: (i) similarity in size and surface components; (ii) ease of generation and noninfectious nature enabling study of BSL3 and BSL4 viruses; (iii) facile characterization of aerosolization parameters; (iv) ability to adapt the system to other viral envelope proteins including those of newly discovered pathogens and mutant variants; (v) the ability to introduce viral sequences to develop nucleic acid amplification assays.
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Affiliation(s)
- Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607
| | - Nitin Jayakumar
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607
| | - Veronique Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607
| | - Varada Anirudan
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612
| | - Lijun Rong
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612
| | - Igor Paprotny
- Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607
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3
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Abstract
Influenza hemagglutinin (HA) is a viral membrane bound protein that plays a critical role in the viral life cycle by mediating entry into target cells. HA exploits the lowering of the pH in the endosomal compartment to initiate a series of conformational changes that promote access of the viral genetic material to the cytoplasm, and hence viral replication. In this review we will first discuss what is known about the structural properties of HA as a function of pH. Next, we will discuss the dynamics and intermediate states of HA. We will then discuss the specific residues that are thought to be titrated by the change in pH and possible mechanisms for the pH triggered conformational changes. Finally, we will discuss small molecules that disrupt the pH trigger and thus serve as potential therapeutic strategies to prevent influenza infection.
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Affiliation(s)
- Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, United States
| | - Arnon Lavie
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, United States
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4
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Chen Z, Cui Q, Caffrey M, Rong L, Du R. Small Molecule Inhibitors of Influenza Virus Entry. Pharmaceuticals (Basel) 2021; 14:ph14060587. [PMID: 34207368 PMCID: PMC8234048 DOI: 10.3390/ph14060587] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 06/13/2021] [Accepted: 06/15/2021] [Indexed: 12/16/2022] Open
Abstract
Hemagglutinin (HA) plays a critical role during influenza virus receptor binding and subsequent membrane fusion process, thus HA has become a promising drug target. For the past several decades, we and other researchers have discovered a series of HA inhibitors mainly targeting its fusion machinery. In this review, we summarize the advances in HA-targeted development of small molecule inhibitors. Moreover, we discuss the structural basis and mode of action of these inhibitors, and speculate upon future directions toward more potent inhibitors of membrane fusion and potential anti-influenza drugs.
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Affiliation(s)
- Zhaoyu Chen
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan 250355, China; (Z.C.); (Q.C.)
| | - Qinghua Cui
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan 250355, China; (Z.C.); (Q.C.)
- Experimental Center, Shandong University of Traditional Chinese Medicine, Jinan 250355, China
- Qingdao Academy of Chinese Medicinal Sciences, Shandong University of Traditional Chinese Medicine, Qingdao 266122, China
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA;
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
- Correspondence: (L.R.); (R.D.); Tel.: +1-312-355-0203 (L.R.); +86-0531-89628505 (R.D.)
| | - Ruikun Du
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan 250355, China; (Z.C.); (Q.C.)
- Experimental Center, Shandong University of Traditional Chinese Medicine, Jinan 250355, China
- Qingdao Academy of Chinese Medicinal Sciences, Shandong University of Traditional Chinese Medicine, Qingdao 266122, China
- Correspondence: (L.R.); (R.D.); Tel.: +1-312-355-0203 (L.R.); +86-0531-89628505 (R.D.)
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5
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Schafer A, Xiong R, Cooper L, Nowar R, Lee H, Li Y, Ramirez BE, Peet NP, Caffrey M, Thatcher GRJ, Saphire EO, Cheng H, Rong L. Evidence for distinct mechanisms of small molecule inhibitors of filovirus entry. PLoS Pathog 2021; 17:e1009312. [PMID: 33539432 PMCID: PMC7888603 DOI: 10.1371/journal.ppat.1009312] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 02/17/2021] [Accepted: 01/14/2021] [Indexed: 12/18/2022] Open
Abstract
Many small molecules have been identified as entry inhibitors of filoviruses. However, a lack of understanding of the mechanism of action for these molecules limits further their development as anti-filoviral agents. Here we provide evidence that toremifene and other small molecule entry inhibitors have at least three distinctive mechanisms of action and lay the groundwork for future development of anti-filoviral agents. The three mechanisms identified here include: (1) direct binding to the internal fusion loop region of Ebola virus glycoprotein (GP); (2) the HR2 domain is likely the main binding site for Marburg virus GP inhibitors and a secondary binding site for some EBOV GP inhibitors; (3) lysosome trapping of GP inhibitors increases drug exposure in the lysosome and further improves the viral inhibition. Importantly, small molecules targeting different domains on GP are synergistic in inhibiting EBOV entry suggesting these two mechanisms of action are distinct. Our findings provide important mechanistic insights into filovirus entry and rational drug design for future antiviral development.
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Affiliation(s)
- Adam Schafer
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Rui Xiong
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Laura Cooper
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America.,Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Raghad Nowar
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America.,Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Hyun Lee
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America.,Biophysics core, Research Resources Center, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Yangfeng Li
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Benjamin E Ramirez
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America.,NMR Core, Research Resources Center, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Norton P Peet
- Chicago BioSolutions Inc., Chicago, Illinois, United States of America
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Gregory R J Thatcher
- Department of Pharmaceutical Sciences, College of Pharmacy, and UICentre, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | | | - Han Cheng
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
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6
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Wiens RC, Maurice S, Robinson SH, Nelson AE, Cais P, Bernardi P, Newell RT, Clegg S, Sharma SK, Storms S, Deming J, Beckman D, Ollila AM, Gasnault O, Anderson RB, André Y, Michael Angel S, Arana G, Auden E, Beck P, Becker J, Benzerara K, Bernard S, Beyssac O, Borges L, Bousquet B, Boyd K, Caffrey M, Carlson J, Castro K, Celis J, Chide B, Clark K, Cloutis E, Cordoba EC, Cousin A, Dale M, Deflores L, Delapp D, Deleuze M, Dirmyer M, Donny C, Dromart G, George Duran M, Egan M, Ervin J, Fabre C, Fau A, Fischer W, Forni O, Fouchet T, Fresquez R, Frydenvang J, Gasway D, Gontijo I, Grotzinger J, Jacob X, Jacquinod S, Johnson JR, Klisiewicz RA, Lake J, Lanza N, Laserna J, Lasue J, Le Mouélic S, Legett C, Leveille R, Lewin E, Lopez-Reyes G, Lorenz R, Lorigny E, Love SP, Lucero B, Madariaga JM, Madsen M, Madsen S, Mangold N, Manrique JA, Martinez JP, Martinez-Frias J, McCabe KP, McConnochie TH, McGlown JM, McLennan SM, Melikechi N, Meslin PY, Michel JM, Mimoun D, Misra A, Montagnac G, Montmessin F, Mousset V, Murdoch N, Newsom H, Ott LA, Ousnamer ZR, Pares L, Parot Y, Pawluczyk R, Glen Peterson C, Pilleri P, Pinet P, Pont G, Poulet F, Provost C, Quertier B, Quinn H, Rapin W, Reess JM, Regan AH, Reyes-Newell AL, Romano PJ, Royer C, Rull F, Sandoval B, Sarrao JH, Sautter V, Schoppers MJ, Schröder S, Seitz D, Shepherd T, Sobron P, Dubois B, Sridhar V, Toplis MJ, Torre-Fdez I, Trettel IA, Underwood M, Valdez A, Valdez J, Venhaus D, Willis P. The SuperCam Instrument Suite on the NASA Mars 2020 Rover: Body Unit and Combined System Tests. Space Sci Rev 2021; 217:4. [PMID: 33380752 PMCID: PMC7752893 DOI: 10.1007/s11214-020-00777-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Accepted: 11/27/2020] [Indexed: 05/16/2023]
Abstract
The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam's body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245-340 and 385-465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535-853 nm ( 105 - 7070 cm - 1 Raman shift relative to the 532 nm green laser beam) with 12 cm - 1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well.
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Affiliation(s)
| | - Sylvestre Maurice
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | | | | | - Philippe Cais
- Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Bordeaux, France
| | - Pernelle Bernardi
- Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Meudon, France
| | | | - Sam Clegg
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | | | | | | | | | - Olivier Gasnault
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Ryan B. Anderson
- U.S. Geological Survey Astrogeology Science Center, Flagstaff, AZ USA
| | - Yves André
- Centre National d’Etudes Spatiales, Toulouse, France
| | | | - Gorka Arana
- University of Basque Country, UPV/EHU, Bilbao, Spain
| | | | - Pierre Beck
- Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble Alpes, Grenoble, France
| | | | - Karim Benzerara
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | - Sylvain Bernard
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | - Olivier Beyssac
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | - Louis Borges
- Los Alamos National Laboratory, Los Alamos, NM USA
| | - Bruno Bousquet
- Centre Lasers Intenses et Applications, University of Bordeaux, Bordeaux, France
| | - Kerry Boyd
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | | | - Kepa Castro
- University of Basque Country, UPV/EHU, Bilbao, Spain
| | - Jorden Celis
- Los Alamos National Laboratory, Los Alamos, NM USA
| | - Baptiste Chide
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
- Institut Supérieur de l’Aéronautique et de l’Espace (ISAE), Toulouse, France
| | - Kevin Clark
- Jet Propulsion Laboratory/Caltech, Pasadena, CA USA
| | | | | | - Agnes Cousin
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | | | | | | | | | | | | | - Gilles Dromart
- Univ Lyon, ENSL, Univ Lyon 1, CNRS, LGL-TPE, 69364 Lyon, France
| | | | | | - Joan Ervin
- Jet Propulsion Laboratory/Caltech, Pasadena, CA USA
| | - Cecile Fabre
- GeoRessources, Université de Lorraine, Nancy, France
| | - Amaury Fau
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | | | - Olivier Forni
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Thierry Fouchet
- Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Meudon, France
| | | | | | | | | | | | - Xavier Jacob
- Institut de mécanique des fluides de Toulouse (CNRS, INP, Univ. Toulouse), Toulouse, France
| | - Sophie Jacquinod
- Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Meudon, France
| | | | | | - James Lake
- Los Alamos National Laboratory, Los Alamos, NM USA
| | - Nina Lanza
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | - Jeremie Lasue
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Stéphane Le Mouélic
- Laboratoire de Planétologie et Géodynamique, Université de Nantes, Université d’Angers, CNRS UMR 6112, Nantes, France
| | - Carey Legett
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | - Eric Lewin
- Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble Alpes, Grenoble, France
| | | | - Ralph Lorenz
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Eric Lorigny
- Centre National d’Etudes Spatiales, Toulouse, France
| | | | | | | | | | - Soren Madsen
- Jet Propulsion Laboratory/Caltech, Pasadena, CA USA
| | - Nicolas Mangold
- Laboratoire de Planétologie et Géodynamique, Université de Nantes, Université d’Angers, CNRS UMR 6112, Nantes, France
| | | | | | | | | | | | | | | | | | - Pierre-Yves Meslin
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | | | - David Mimoun
- Institut Supérieur de l’Aéronautique et de l’Espace (ISAE), Toulouse, France
| | | | | | - Franck Montmessin
- Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris, France
| | | | - Naomi Murdoch
- Institut Supérieur de l’Aéronautique et de l’Espace (ISAE), Toulouse, France
| | | | - Logan A. Ott
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | - Laurent Pares
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Yann Parot
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | | | | | - Paolo Pilleri
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Patrick Pinet
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Gabriel Pont
- Centre National d’Etudes Spatiales, Toulouse, France
| | | | | | - Benjamin Quertier
- Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Bordeaux, France
| | | | - William Rapin
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | - Jean-Michel Reess
- Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Meudon, France
| | - Amy H. Regan
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | | | - Clement Royer
- Institut d’Astrophysique Spatiale (IAS), Orsay, France
| | | | | | | | - Violaine Sautter
- Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS, Museum National d’Histoire Naturelle, Sorbonne Université, Paris, France
| | | | - Susanne Schröder
- Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Optical Sensor Systems, Berlin, Germany
| | - Daniel Seitz
- Los Alamos National Laboratory, Los Alamos, NM USA
| | | | | | - Bruno Dubois
- Université de Toulouse; UPS-OMP, Toulouse, France
| | | | - Michael J. Toplis
- Institut de Recherche en Astrophysique et Planetologie (IRAP), Université de Toulouse, UPS, CNRS, Toulouse, France
| | | | | | | | | | - Jacob Valdez
- Los Alamos National Laboratory, Los Alamos, NM USA
| | - Dawn Venhaus
- Los Alamos National Laboratory, Los Alamos, NM USA
| | - Peter Willis
- Jet Propulsion Laboratory/Caltech, Pasadena, CA USA
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7
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Antanasijevic A, Durst MA, Cheng H, Gaisina IN, Perez JT, Manicassamy B, Rong L, Lavie A, Caffrey M. Structure of avian influenza hemagglutinin in complex with a small molecule entry inhibitor. Life Sci Alliance 2020; 3:3/8/e202000724. [PMID: 32611549 PMCID: PMC7335401 DOI: 10.26508/lsa.202000724] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/12/2020] [Accepted: 06/15/2020] [Indexed: 12/14/2022] Open
Abstract
The binding properties of fusion inhibitor CBS1117 to hemagglutinin by x-ray crystallography, NMR, and mutagenesis give insights into mechanism and guidance for chemical optimization. HA plays a critical role in influenza infection and, thus HA is a potential target for antivirals. Recently, our laboratories have described a novel fusion inhibitor, termed CBS1117, with EC50 ∼3 μM against group 1 HA. In this work, we characterize the binding properties of CBS1117 to avian H5 HA by x-ray crystallography, NMR, and mutagenesis. The x-ray structure of the complex shows that the compound binds near the HA fusion peptide, a region that plays a critical role in HA-mediated fusion. NMR studies demonstrate binding of CBS1117 to H5 HA in solution and show extensive hydrophobic contacts between the compound and HA surface. Mutagenesis studies further support the location of the compound binding site proximal to the HA fusion peptide and identify additional amino acids that are important to compound binding. Together, this work gives new insights into the CBS1117 mechanism of action and can be exploited to further optimize this compound and better understand the group specific activity of small-molecule inhibitors of HA-mediated entry.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Matthew A Durst
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Han Cheng
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
| | | | - Jasmine T Perez
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Balaji Manicassamy
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Lijun Rong
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
| | - Arnon Lavie
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
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8
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Hussein AFA, Cheng H, Tundup S, Antanasijevic A, Varhegyi E, Perez J, AbdulRahman EM, Elenany MG, Helal S, Caffrey M, Peet N, Manicassamy B, Rong L. Identification of entry inhibitors with 4-aminopiperidine scaffold targeting group 1 influenza A virus. Antiviral Res 2020; 177:104782. [PMID: 32222293 PMCID: PMC7243365 DOI: 10.1016/j.antiviral.2020.104782] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/20/2020] [Accepted: 03/22/2020] [Indexed: 01/09/2023]
Abstract
Influenza A viruses (IAVs) cause seasonal flu and occasionally pandemics. The current therapeutics against IAVs target two viral proteins - neuraminidase (NA) and M2 ion-channel protein. However, M2 ion channel inhibitors (amantadine and rimantadine) are no longer recommended by CDC for use due to the emergence of high level of antiviral resistance among the circulating influenza viruses, and resistant strains to NA inhibitors (oseltamivir and zanamivir) have also been reported. Therefore, development of novel anti-influenza therapies is urgently needed. As one of the viral surface glycoproteins, hemagglutinin (HA) mediates critical virus entry steps including virus binding to host cells and virus-host membrane fusion, which makes it a potential target for anti-influenza drug development. In this study, we report the identification of compound CBS1116 with a 4-aminopiperidine scaffold from a chemical library screen as an entry inhibitor specifically targeting two group 1 influenza A viruses, A/Puerto Rico/8/34 (H1N1) and recombinant low pathogenic avian H5N1 virus (A/Vietnam/1203/04, VN04Low). Mechanism of action studies show that CBS1116 interferes with the HA-mediated fusion process. Further structure activity relationship study generated a more potent compound CBS1117 which has a 50% inhibitory concentration of 70 nM and a selectivity index of ~4000 against A/Puerto Rico/8/34 (H1N1) infection in human lung epithelial cell line (A549).
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Affiliation(s)
- Amira F A Hussein
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA; Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Han Cheng
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Smanla Tundup
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, IL, 60439, USA; Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Elizabeth Varhegyi
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Jasmine Perez
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Eiman M AbdulRahman
- Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mervat G Elenany
- Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Soheir Helal
- Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Norton Peet
- Chicago BioSolutions, Inc., 2242 West Harrison Suite 201, Chicago, IL, 60612, USA
| | - Balaji Manicassamy
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, IL, 60439, USA; Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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9
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Gaisina IN, Peet NP, Cheng H, Li P, Du R, Cui Q, Furlong K, Manicassamy B, Caffrey M, Thatcher GRJ, Rong L. Optimization of 4-Aminopiperidines as Inhibitors of Influenza A Viral Entry That Are Synergistic with Oseltamivir. J Med Chem 2020; 63:3120-3130. [PMID: 32069052 DOI: 10.1021/acs.jmedchem.9b01900] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Vaccination is the most prevalent prophylactic means for controlling seasonal influenza infections. However, an effective vaccine usually takes at least 6 months to develop for the circulating strains. Therefore, new therapeutic options are needed for the acute treatment of influenza infections to control this virus and prevent epidemics/pandemics from developing. We have discovered fast-acting, orally bioavailable acylated 4-aminopiperidines with an effective mechanism of action targeting viral hemagglutinin (HA). Our data show that these compounds are potent entry inhibitors of influenza A viruses. We present docking studies that suggest an HA binding site for these inhibitors on H5N1. Compound 16 displayed a significant decrease of viral titer when evaluated in the infectious assays with influenza virus H1N1 (A/Puerto Rico/8/1934) or H5N1 (A/Vietnam/1203/2004) strains and the oseltamivir-resistant strain with the most common H274Y mutation. In addition, compound 16 showed significant synergistic activity with oseltamivir in vitro.
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Affiliation(s)
- Irina N Gaisina
- UICentre (Drug Discovery@UIC) and Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612, United States.,Chicago BioSolutions, Inc., 2242 West Harrison Street, Chicago, Illinois 60612, United States
| | - Norton P Peet
- Chicago BioSolutions, Inc., 2242 West Harrison Street, Chicago, Illinois 60612, United States
| | - Han Cheng
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, 909 South Wolcott Avenue, Chicago, Illinois 60612, United States
| | - Ping Li
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, 16369 Jinshi Road, Jinan, Shandong 250355, China
| | - Ruikun Du
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, 16369 Jinshi Road, Jinan, Shandong 250355, China
| | - Qinghua Cui
- College of Pharmacy, Shandong University of Traditional Chinese Medicine, 16369 Jinshi Road, Jinan, Shandong 250355, China
| | - Kevin Furlong
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, Illinois 60637, United States
| | - Balaji Manicassamy
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, Illinois 60637, United States.,Department of Microbiology and Immunology, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, United States
| | - Gregory R J Thatcher
- UICentre (Drug Discovery@UIC) and Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612, United States
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, 909 South Wolcott Avenue, Chicago, Illinois 60612, United States
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10
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Antanasijevic A, Durst MA, Lavie A, Caffrey M. Identification of a pH sensor in Influenza hemagglutinin using X-ray crystallography. J Struct Biol 2019; 209:107412. [PMID: 31689502 PMCID: PMC7111647 DOI: 10.1016/j.jsb.2019.107412] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 11/15/2022]
Abstract
X-ray crystallography identifies a conserved histidine, HA1-H38, that changes side chain conformation at low pH. We attribute the observed conformational change to cation-cation repulsion between protonated HA1-H18 and HA1-H38. We suggest that the HA1-H18 and HA1-H38 pair plays a role in the pathway toward the postfusion conformation of HA.
Hemagglutnin (HA) mediates entry of influenza virus through a series of conformational changes triggered by the low pH of the endosome. The residue or combination of residues acting as pH sensors has not yet been fully elucidated. In this work, we assay pH effects on the structure of H5 HA by soaking HA crystallized at pH 6.5 in a series of buffers with lower pH, mimicking the conditions of the endosome. We find that HA1-H38, which is conserved in Group 1 HA, undergoes a striking change in side chain conformation, which we attribute to its protonation and cation-cation repulsion with conserved HA1-H18. This work suggests that x-ray crystallography can be applied for studying small-scale pH-induced conformational changes providing valuable information on the location of pH sensors in HA. Importantly, the observed change in HA1-H38 conformation is further evidence that the pH-induced conformational changes of HA are the result of a series of protonation events to conserved and non-conserved pH sensors.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, 60607 Chicago, USA
| | - Matthew A Durst
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, 60607 Chicago, USA
| | - Arnon Lavie
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, 60607 Chicago, USA.
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, 60607 Chicago, USA.
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11
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Nguyen HA, Su Y, Zhang JY, Antanasijevic A, Caffrey M, Schalk AM, Liu L, Rondelli D, Oh A, Mahmud DL, Bosland MC, Kajdacsy-Balla A, Peirs S, Lammens T, Mondelaers V, De Moerloose B, Goossens S, Schlicht MJ, Kabirov KK, Lyubimov AV, Merrill BJ, Saunthararajah Y, Van Vlierberghe P, Lavie A. A Novel l-Asparaginase with low l-Glutaminase Coactivity Is Highly Efficacious against Both T- and B-cell Acute Lymphoblastic Leukemias In Vivo. Cancer Res 2018; 78:1549-1560. [PMID: 29343523 DOI: 10.1158/0008-5472.can-17-2106] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 12/13/2017] [Accepted: 01/11/2018] [Indexed: 01/04/2023]
Abstract
Acute lymphoblastic leukemia (ALL) is the most common type of pediatric cancer, although about 4 of every 10 cases occur in adults. The enzyme drug l-asparaginase serves as a cornerstone of ALL therapy and exploits the asparagine dependency of ALL cells. In addition to hydrolyzing the amino acid l-asparagine, all FDA-approved l-asparaginases also have significant l-glutaminase coactivity. Since several reports suggest that l-glutamine depletion correlates with many of the side effects of these drugs, enzyme variants with reduced l-glutaminase coactivity might be clinically beneficial if their antileukemic activity would be preserved. Here we show that novel low l-glutaminase variants developed on the backbone of the FDA-approved Erwinia chrysanthemi l-asparaginase were highly efficacious against both T- and B-cell ALL, while displaying reduced acute toxicity features. These results support the development of a new generation of safer l-asparaginases without l-glutaminase activity for the treatment of human ALL.Significance: A new l-asparaginase-based therapy is less toxic compared with FDA-approved high l-glutaminase enzymes Cancer Res; 78(6); 1549-60. ©2018 AACR.
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Affiliation(s)
- Hien Anh Nguyen
- The Jesse Brown VA Medical Center, Chicago, Illinois.,Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Ying Su
- The Jesse Brown VA Medical Center, Chicago, Illinois.,Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Jenny Y Zhang
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Amanda M Schalk
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Li Liu
- Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois
| | - Damiano Rondelli
- Division of Hematology/Oncology, University of Illinois Hospital and Health Sciences System, Chicago, Illinois
| | - Annie Oh
- Division of Hematology/Oncology, University of Illinois Hospital and Health Sciences System, Chicago, Illinois
| | - Dolores L Mahmud
- Division of Hematology/Oncology, University of Illinois Hospital and Health Sciences System, Chicago, Illinois
| | - Maarten C Bosland
- Department of Pathology, University of Illinois at Chicago, Chicago, Illinois
| | | | - Sofie Peirs
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium.,Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Tim Lammens
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium.,Department of Pediatric Hematology-Oncology and Stem Cell Transplantation, Ghent University Hospital, Ghent, Belgium
| | - Veerle Mondelaers
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium.,Department of Pediatric Hematology-Oncology and Stem Cell Transplantation, Ghent University Hospital, Ghent, Belgium
| | - Barbara De Moerloose
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium.,Department of Pediatric Hematology-Oncology and Stem Cell Transplantation, Ghent University Hospital, Ghent, Belgium
| | - Steven Goossens
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium.,Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Michael J Schlicht
- Department of Pathology, University of Illinois at Chicago, Chicago, Illinois
| | - Kasim K Kabirov
- Toxicology Research Laboratory, Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois
| | - Alexander V Lyubimov
- Toxicology Research Laboratory, Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois
| | - Bradley J Merrill
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
| | - Yogen Saunthararajah
- Department of Translational Hematology & Oncology Research, Cleveland Clinic Foundation, Cleveland, Ohio
| | - Pieter Van Vlierberghe
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium. .,Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Arnon Lavie
- The Jesse Brown VA Medical Center, Chicago, Illinois. .,Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois,
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12
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Leiva R, Barniol-Xicota M, Codony S, Ginex T, Vanderlinden E, Montes M, Caffrey M, Luque FJ, Naesens L, Vázquez S. Aniline-Based Inhibitors of Influenza H1N1 Virus Acting on Hemagglutinin-Mediated Fusion. J Med Chem 2017; 61:98-118. [PMID: 29220568 DOI: 10.1021/acs.jmedchem.7b00908] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Two series of easily accessible anilines were identified as inhibitors of influenza A virus subtype H1N1, and extensive chemical synthesis and analysis of the structure-activity relationship were performed. The compounds were shown to interfere with low pH-induced membrane fusion mediated by the H1 and H5 (group 1) hemagglutinin (HA) subtypes. A combination of virus resistance, HA interaction, and molecular dynamics simulation studies elucidated the binding site of these aniline-based influenza fusion inhibitors, which significantly overlaps with the pocket occupied by some H3 HA-specific inhibitors, indicating the high relevance of this cavity for drug design.
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Affiliation(s)
- Rosana Leiva
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Marta Barniol-Xicota
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Sandra Codony
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Tiziana Ginex
- Department of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and Food Sciences, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Prat de la Riba 171, Santa Coloma de Gramanet E-08921, Spain
| | | | - Marta Montes
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Michael Caffrey
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago , 900 South Ashland Avenue, Chicago, Illinois 60607, United States
| | - F Javier Luque
- Department of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and Food Sciences, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Prat de la Riba 171, Santa Coloma de Gramanet E-08921, Spain
| | - Lieve Naesens
- Rega Institute for Medical Research, KU Leuven , B-3000 Leuven, Belgium
| | - Santiago Vázquez
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
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13
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Kingsley CN, Antanasijevic A, Palka-Hamblin H, Durst M, Ramirez B, Lavie A, Caffrey M. Probing the metastable state of influenza hemagglutinin. J Biol Chem 2017; 292:21590-21597. [PMID: 29127198 DOI: 10.1074/jbc.m117.815043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/05/2017] [Indexed: 12/24/2022] Open
Abstract
Viral entry into host cells is mediated by membrane proteins in a metastable state that transition to a more stable state upon a stimulus. For example, in the influenza envelope protein hemagglutinin (HA), the low pH in the endosome triggers a transition from the metastable prefusion conformation to the stable fusion conformation. To identify probes that interfere with HA function, here we screened a library of H7 HA peptides for inhibition of H7 HA-mediated entry. We discovered a peptide, PEP87 (WSYNAELLVAMENQHTI), that inhibited H7 and H5 HA-mediated entry. PEP87 corresponds to a highly conserved helical region of the HA2 subunit of HA that self-interacts in the neutral pH conformation. Mutagenesis experiments indicated that PEP87 binds to its native region in the HA trimer. We also found that PEP87 is unstructured in isolation but tends to form a helix as evidenced by CD and NMR studies. Fluorescence, chemical cross-linking, and saturation transfer difference NMR data suggested that PEP87 binds to the neutral pH conformation of HA and disrupts the HA structure without affecting its oligomerization state. Together, this work provides support for a model in which PEP87 disrupts HA function by displacing native interactions of the neutral pH conformation. Moreover, our observations indicate that the HA prefusion structure (and perhaps the metastable states of other viral entry proteins) is more dynamic with transient motions being larger than generally appreciated. These findings also suggest that the ensemble of prefusion structures presents many potential sites for targeting in therapeutic interventions.
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Affiliation(s)
- Carolyn N Kingsley
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Aleksandar Antanasijevic
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Helena Palka-Hamblin
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Matthew Durst
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Benjamin Ramirez
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Arnon Lavie
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Michael Caffrey
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
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14
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Deibler KK, Mishra RK, Clutter MR, Antanasijevic A, Bergan R, Caffrey M, Scheidt KA. A Chemical Probe Strategy for Interrogating Inhibitor Selectivity Across the MEK Kinase Family. ACS Chem Biol 2017; 12:1245-1256. [PMID: 28263556 PMCID: PMC5652073 DOI: 10.1021/acschembio.6b01060] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
MEK4 is an upstream kinase in MAPK signaling pathways where it phosphorylates p38 MAPK and JNK in response to mitogenic and cellular stress queues. MEK4 is overexpressed and induces metastasis in advanced prostate cancer lesions. However, the value of MEK4 as an oncology target has not been pharmacologically validated because selective chemical probes targeting MEK4 have not been developed. Despite a high level of sequence homology in the ATP-binding site, most reported MEK inhibitors are selective for MEK1/2 and display reduced potency toward other MEKs. Here, we present the first functional and binding selectivity-profiling platform of the MEK family. We applied the platform to profile a set of known kinase inhibitors and used the results to develop an in silico approach for small molecule docking against MEK proteins. The docking studies identified molecular features of the ligands and corresponding amino acids in MEK proteins responsible for high affinity binding versus those driving selectivity. WaterLOGSY and saturation transfer difference (STD) NMR spectroscopy techniques were utilized to understand the binding modes of active compounds. Further minor synthetic manipulations provide a proof of concept by showing how information gained through this platform can be utilized to perturb selectivity across the MEK family. This inhibitor-based approach pinpoints key features governing MEK family selectivity and clarifies empirical selectivity profiles for a set of kinase inhibitors. Going forward, the platform provides a rationale for facilitating the development of MEK-selective inhibitors, particularly MEK4 selective inhibitors, and repurposing of kinase inhibitors for probing the structural selectivity of isoforms.
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Affiliation(s)
- Kristine K. Deibler
- Department of Chemistry, Northwestern University, Evanston, 60208, Illinois, United States
| | - Rama K. Mishra
- Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, United States
| | - Matthew R. Clutter
- Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, United States
| | - Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, Chicago, Illinois 60607, United States
| | - Raymond Bergan
- Knight Cancer Institute, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Portland, Oregon 97239, United States
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland Ave, Chicago, Illinois 60607, United States
| | - Karl A. Scheidt
- Department of Chemistry, Northwestern University, Evanston, 60208, Illinois, United States
- Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, United States
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States
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15
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Basu A, Komazin-Meredith G, McCarthy C, Antanasijevic A, Cardinale SC, Mishra RK, Barnard DL, Caffrey M, Rong L, Bowlin TL. Molecular Mechanism Underlying the Action of Influenza A Virus Fusion Inhibitor MBX2546. ACS Infect Dis 2017; 3:330-335. [PMID: 28301927 DOI: 10.1021/acsinfecdis.6b00194] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Influenza A virus envelop protein hemagglutinin (HA) plays important roles in viral entry. We previously have reported that MBX2546, a novel influenza A virus inhibitor, binds to HA and inhibits HA-mediated membrane fusion. In this report, we show that (i) both binding and stabilization of HA by MBX2546 are required for the inhibition of viral infection and (ii) the binding of HA by MBX2546 represses the low-pH-induced conformational change in the HA, which is a prerequisite for membrane fusion. Mutations in MBX2546-resistant influenza A/PR/8/34 (H1N1) viruses are mapped in the HA stem region near the amino terminus of HA2. Finally, we have modeled the binding site of MBX2546 using molecular dynamics and find that the resulting structure is in good agreement with our results. Together, these studies underscore the importance of the HA stem loop region as a potential target for therapeutic intervention.
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Affiliation(s)
- Arnab Basu
- Microbiotix Inc., One Innovation Drive, Worcester, Massachusetts 01605, United States
| | | | - Courtney McCarthy
- Microbiotix Inc., One Innovation Drive, Worcester, Massachusetts 01605, United States
| | - Aleksandar Antanasijevic
- Department
of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Steven C. Cardinale
- Microbiotix Inc., One Innovation Drive, Worcester, Massachusetts 01605, United States
| | - Rama K. Mishra
- Center for Molecular
Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208, United States
| | - Dale L. Barnard
- Institute
for
Antiviral Research, Utah State University, Logan, Utah 84322, United States
| | - Michael Caffrey
- Department
of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Lijun Rong
- Department
of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Terry L. Bowlin
- Microbiotix Inc., One Innovation Drive, Worcester, Massachusetts 01605, United States
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16
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Antanasijevic A, Hafeman NJ, Tundup S, Kingsley C, Mishra RK, Rong L, Manicassamy B, Wardrop D, Caffrey M. Stabilization and Improvement of a Promising Influenza Antiviral: Making a PAIN PAINless. ACS Infect Dis 2016; 2:608-615. [PMID: 27759373 DOI: 10.1021/acsinfecdis.6b00046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The viral envelope protein hemagglutinin (HA) plays a critical role in influenza entry and thus is an attractive target for novel therapeutics. The small molecule tert-butylhydroquinone (TBHQ) has previously been shown to bind to HA and inhibit HA-mediated entry with low micromolar potency. However, enthusiasm for the use of TBHQ has diminished due to the compound's antioxidant properties. In this work we show that the antioxidant properties of TBHQ are not responsible for the inhibition of HA-mediated entry. In addition, we have performed a structure-activity relationship (SAR) analysis of TBHQ derivatives. We find that the most promising compound, 3-tert-butyl-4-methoxyphenol, exhibits enhanced potency (IC50 = 0.6 μM), decreased toxicity (CC50 = 340 μM), and increased stability (t1/2 > 48 h). Finally, we have characterized the binding properties of 3-tert-butyl-4-methoxyphenol using NMR and molecular dynamics to guide future efforts for chemical optimization.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, United States
| | - Nicholas J. Hafeman
- Department
of Chemistry, University of Illinois at Chicago, 845 West Taylor
Street, Chicago, Illinois 60607, United States
| | - Smanla Tundup
- Department
of Microbiology and Immunology, University of Chicago, 920 East
58th Street, Chicago, Illinois 60637, United States
| | - Carolyn Kingsley
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, United States
| | - Rama K. Mishra
- Center for Molecular Innovation and Drug Discovery, Northwestern University, 2135 Sheridan Road, Evanston, Illinois 60208, United States
| | - Lijun Rong
- Department of Microbiology & Immunology, University of Illinois at Chicago, 835 South Wolcott, Chicago, Illinois 60612, United States
| | - Balaji Manicassamy
- Department
of Microbiology and Immunology, University of Chicago, 920 East
58th Street, Chicago, Illinois 60637, United States
| | - Duncan Wardrop
- Department
of Chemistry, University of Illinois at Chicago, 845 West Taylor
Street, Chicago, Illinois 60607, United States
| | - Michael Caffrey
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, United States
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17
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Antanasijevic A, Kingsley C, Basu A, Bowlin TL, Rong L, Caffrey M. Application of virus-like particles (VLP) to NMR characterization of viral membrane protein interactions. J Biomol NMR 2016; 64:255-65. [PMID: 26921030 PMCID: PMC4826305 DOI: 10.1007/s10858-016-0025-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/22/2016] [Indexed: 05/10/2023]
Abstract
The membrane proteins of viruses play critical roles in the virus life cycle and are attractive targets for therapeutic intervention. Virus-like particles (VLP) present the possibility to study the biochemical and biophysical properties of viral membrane proteins in their native environment. Specifically, the VLP constructs contain the entire protein sequence and are comprised of native membrane components including lipids, cholesterol, carbohydrates and cellular proteins. In this study we prepare VLP containing full-length hemagglutinin (HA) or neuraminidase (NA) from influenza and characterize their interactions with small molecule inhibitors. Using HA-VLP, we first show that VLP samples prepared using the standard sucrose gradient purification scheme contain significant amounts of serum proteins, which exhibit high potential for non-specific interactions, thereby complicating NMR studies of ligand-target interactions. We then show that the serum contaminants may be largely removed with the addition of a gel filtration chromatography step. Next, using HA-VLP we demonstrate that WaterLOGSY NMR is significantly more sensitive than Saturation Transfer Difference (STD) NMR for the study of ligand interactions with membrane bound targets. In addition, we compare the ligand orientation to HA embedded in VLP with that of recombinant HA by STD NMR. In a subsequent step, using NA-VLP we characterize the kinetic and binding properties of substrate analogs and inhibitors of NA, including study of the H274Y-NA mutant, which leads to wide spread resistance to current influenza antivirals. In summary, our work suggests that VLP have high potential to become standard tools in biochemical and biophysical studies of viral membrane proteins, particularly when VLP are highly purified and combined with control VLP containing native membrane proteins.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland, Chicago, IL, 60607, USA
| | - Carolyn Kingsley
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland, Chicago, IL, 60607, USA
| | - Arnab Basu
- Microbiotix Inc., Worcester, MA, 01605, USA
| | | | - Lijun Rong
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland, Chicago, IL, 60607, USA.
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18
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Schalk AM, Antansijevic A, Caffrey M, Lavie A. Experimental Data in Support of a Direct Displacement Mechanism for Type I/II L-Asparaginases. J Biol Chem 2016; 291:5088-100. [PMID: 26733195 DOI: 10.1074/jbc.m115.699884] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Indexed: 01/02/2023] Open
Abstract
Bacterial L-asparaginases play an important role in the treatment of certain types of blood cancers. We are exploring the guinea pig L-asparaginase (gpASNase1) as a potential replacement of the immunogenic bacterial enzymes. The exact mechanism used by L-asparaginases to catalyze the hydrolysis of asparagine into aspartic acid and ammonia has been recently put into question. Earlier experimental data suggested that the reaction proceeds via a covalent intermediate using a ping-pong mechanism, whereas recent computational work advocates the direct displacement of the amine by an activated water. To shed light on this controversy, we generated gpASNase1 mutants of conserved active site residues (T19A, T116A, T19A/T116A, K188M, and Y308F) suspected to play a role in hydrolysis. Using x-ray crystallography, we determined the crystal structures of the T19A, T116A, and K188M mutants soaked in asparagine. We also characterized their steady-state kinetic properties and analyzed the conversion of asparagine to aspartate using NMR. Our structures reveal bound asparagine in the active site that has unambiguously not formed a covalent intermediate. Kinetic and NMR assays detect significant residual activity for all of the mutants. Furthermore, no burst of ammonia production was observed that would indicate covalent intermediate formation and the presence of a ping-pong mechanism. Hence, despite using a variety of techniques, we were unable to obtain experimental evidence that would support the formation of a covalent intermediate. Consequently, our observations support a direct displacement rather than a ping-pong mechanism for l-asparaginases.
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Affiliation(s)
- Amanda M Schalk
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607 and
| | - Aleksandar Antansijevic
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607 and
| | - Michael Caffrey
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607 and
| | - Arnon Lavie
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607 and the Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612
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19
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Light SH, Minasov G, Shuvalova L, Duban ME, Caffrey M, Anderson WF, Lavie A. Insights into the mechanism of type I dehydroquinate dehydratases from structures of reaction intermediates. J Biol Chem 2015; 290:19008. [PMID: 26232400 PMCID: PMC4521023 DOI: 10.1074/jbc.a110.192831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/27/2023] Open
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20
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Nomme J, Antanasijevic A, Caffrey M, Van Itallie CM, Anderson JM, Fanning AS, Lavie A. Structural Basis of a Key Factor Regulating the Affinity between the Zonula Occludens First PDZ Domain and Claudins. J Biol Chem 2015; 290:16595-606. [PMID: 26023235 DOI: 10.1074/jbc.m115.646695] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 11/06/2022] Open
Abstract
The molecular seal between epithelial cells, called the tight junction (TJ), is built by several membrane proteins, with claudins playing the most prominent role. The scaffold proteins of the zonula occludens family are required for the correct localization of claudins and hence formation of the TJ. The intracellular C terminus of claudins binds to the N-terminal PDZ domain of zonula occludens proteins (PDZ1). Of the 23 identified human claudin proteins, nine possess a tyrosine at the -6 position. Here we show that the claudin affinity for PDZ1 is dependent on the presence or absence of this tyrosine and that the affinity is reduced if the tyrosine is modified by phosphorylation. The PDZ1 β2-β3 loop undergoes a significant conformational change to accommodate this tyrosine. Cell culture experiments support a regulatory role for this tyrosine. Plasticity has been recognized as a critical property of TJs that allow cell remodeling and migration. Our work provides a molecular framework for how TJ plasticity may be regulated.
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Affiliation(s)
- Julian Nomme
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Aleksandar Antanasijevic
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Michael Caffrey
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Christina M Van Itallie
- Laboratory of Tight Junction Structure and Function, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, and
| | - James M Anderson
- Laboratory of Tight Junction Structure and Function, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Alan S Fanning
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Arnon Lavie
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607,
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21
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Abstract
NMR has proven to be an invaluable technique for identifying and characterizing ligand interactions with biomolecules. NMR-based detection of ligand binding to protein targets is described. Specifically, the use of the WaterLOGSY NMR experiment to screen mixtures of compounds from a fragment library for binding to influenza H5 hemagglutinin is detailed.
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Affiliation(s)
- Benjamin E Ramirez
- Center for Structural Biology, University of Illinois at Chicago, 1100 S. Ashland Ave, Chicago, IL, 60607, USA
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22
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Antanasijevic A, Ramirez B, Caffrey M. Comparison of the sensitivities of WaterLOGSY and saturation transfer difference NMR experiments. J Biomol NMR 2014; 60:37-44. [PMID: 25015532 PMCID: PMC4201884 DOI: 10.1007/s10858-014-9848-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 07/08/2014] [Indexed: 05/15/2023]
Abstract
The WaterLOGSY (WL) and saturation transfer difference (STD) NMR experiments have proven to be extremely useful techniques to characterize interactions between small molecules and large biomolecules. In this work we compare the relative sensitivities of WL and STD NMR using 3 experimental systems: ketoprofen (KET)-bovine serum albumin (BSA), tert-butyl hydroquinone (TBHQ)-hemagglutinin (HA), and chloramphenicol (CAM)-ribosome (70S). In all cases we find that WL is more sensitive than STD for a given experimental time with the ratios ranging from 3.2 for KET-BSA to 16 for TBHQ-HA and CAM-70S. We attribute the increased sensitivity of WL to be due to simultaneous saturation of multiple sources of cross correlation, including direct NOEs of 1H of water and exchangeable groups and indirect NOEs of 1H-C groups. We suggest that the outstanding sensitivity of WL make it ideally suited for drug screening efforts targeting very large biomolecules at relatively low concentrations.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607 USA
| | - Benjamin Ramirez
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607 USA
| | - Michael Caffrey
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607 USA
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23
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Antanasijevic A, Basu A, Bowlin TL, Mishra RK, Rong L, Caffrey M. Mutagenesis studies of the H5 influenza hemagglutinin stem loop region. J Biol Chem 2014; 289:22237-45. [PMID: 24947513 DOI: 10.1074/jbc.m114.572974] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Influenza outbreaks, particularly the pandemic 1918 H1 and avian H5 strains, are of high concern to public health. The hemagglutinin envelope protein of influenza plays a critical role in viral entry and thus is an attractive target for inhibition of virus entry. The highly conserved stem loop region of hemagglutinin has been shown to undergo critically important conformational changes during the entry process and, moreover, to be a site for inhibition of virus entry by antibodies, small proteins, and small drug-like molecules. In this work we probe the structure-function properties of the H5 hemagglutinin stem loop region by site-directed mutagenesis. We find that most mutations do not disrupt expression, proteolytic processing, incorporation into virus, or receptor binding; however, many of the mutations disrupt the entry process. We further assess the effects of mutations on inhibition of entry by a neutralizing monoclonal antibody (C179) and find examples of increased and decreased sensitivity to the antibody, consistent with the antibody binding site observed by x-ray crystallography. In addition, we tested the sensitivity of the mutants to MBX2329, a small molecule inhibitor of influenza entry. Interestingly, the mutants exhibit increased and decreased sensitivities to MBX2329, which gives further insight into the binding site of the compound on HA and potential mechanisms of escape. Finally, we have modeled the binding site of MBX2329 using molecular dynamics and find that the resulting structure is in good agreement with the mutagenesis results. Together these studies underscore the importance of the stem loop region to HA function and suggest potential sites for therapeutic intervention of influenza entry.
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Affiliation(s)
- Aleksandar Antanasijevic
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607
| | - Arnab Basu
- Microbiotix Inc., Worcester, Massachusetts 01605
| | | | - Rama K Mishra
- the Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208, and
| | - Lijun Rong
- the Department of Microbiology and Immunology, University of Illinois, Chicago, Illinois 60612
| | - Michael Caffrey
- From the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607,
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24
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Ratia K, Light SH, Antanasijevic A, Anderson WF, Caffrey M, Lavie A. Discovery of selective inhibitors of the Clostridium difficile dehydroquinate dehydratase. PLoS One 2014; 9:e89356. [PMID: 24586713 PMCID: PMC3931744 DOI: 10.1371/journal.pone.0089356] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 01/18/2014] [Indexed: 12/18/2022] Open
Abstract
A vibrant and healthy gut flora is essential for preventing the proliferation of Clostridium difficile, a pathogenic bacterium that causes severe gastrointestinal symptoms. In fact, most C. difficile infections (CDIs) occur after broad-spectrum antibiotic treatment, which, by eradicating the commensal gut bacteria, allows its spores to proliferate. Hence, a C. difficile specific antibiotic that spares the gut flora would be highly beneficial in treating CDI. Towards this goal, we set out to discover small molecule inhibitors of the C. difficile enzyme dehydroquinate dehydratase (DHQD). DHQD is the 3(rd) of seven enzymes that compose the shikimate pathway, a metabolic pathway absent in humans, and is present in bacteria as two phylogenetically and mechanistically distinct types. Using a high-throughput screen we identified three compounds that inhibited the type I C. difficile DHQD but not the type II DHQD from Bacteroides thetaiotaomicron, a highly represented commensal gut bacterial species. Kinetic analysis revealed that the compounds inhibit the C. difficile enzyme with Ki values ranging from 10 to 20 µM. Unexpectedly, kinetic and biophysical studies demonstrate that inhibitors also exhibit selectivity between type I DHQDs, inhibiting the C. difficile but not the highly homologous Salmonella enterica DHQD. Therefore, the three identified compounds seem to be promising lead compounds for the development of C. difficile specific antibiotics.
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Affiliation(s)
- Kiira Ratia
- Research Resources Center, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Samuel H. Light
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Aleksandar Antanasijevic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Wayne F. Anderson
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Arnon Lavie
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
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25
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Light SH, Antanasijevic A, Krishna SN, Caffrey M, Anderson WF, Lavie A. Crystal structures of type I dehydroquinate dehydratase in complex with quinate and shikimate suggest a novel mechanism of Schiff base formation. Biochemistry 2014; 53:872-80. [PMID: 24437575 PMCID: PMC3985847 DOI: 10.1021/bi4015506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
A component of the shikimate biosynthetic
pathway, dehydroquinate
dehydratase (DHQD) catalyzes the dehydration of 3-dehydroquniate (DHQ)
to 3-dehydroshikimate. In the type I DHQD reaction mechanism a lysine
forms a Schiff base intermediate with DHQ. The Schiff base acts as
an electron sink to facilitate the catalytic dehydration. To address
the mechanism of Schiff base formation, we determined structures of
the Salmonella enterica wild-type DHQD in complex
with the substrate analogue quinate and the product analogue shikimate.
In addition, we determined the structure of the K170M mutant (Lys170
being the Schiff base forming residue) in complex with quinate. Combined
with nuclear magnetic resonance and isothermal titration calorimetry
data that revealed altered binding of the analogue to the K170M mutant,
these structures suggest a model of Schiff base formation characterized
by the dynamic interplay of opposing forces acting on either side
of the substrate. On the side distant from the substrate 3-carbonyl
group, closure of the enzyme’s β8−α8 loop
is proposed to guide DHQ into the proximity of the Schiff base-forming
Lys170. On the 3-carbonyl side of the substrate, Lys170 sterically
alters the position of DHQ’s reactive ketone, aligning it at
an angle conducive for nucleophilic attack. This study of a type I
DHQD reveals the interplay between the enzyme and substrate required
for the correct orientation of a functional group constrained within
a cyclic substrate.
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Affiliation(s)
- Samuel H Light
- Center for Structural Genomics of Infectious Diseases and Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University , Chicago, Illinois 60611, United States
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26
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Abstract
The recent outbreak of H7N9 influenza in China is of high concern to public health. H7 hemagglutinin (HA) plays a critical role in influenza entry and thus HA presents an attractive target for antivirals. Previous studies have suggested that the small molecule tert-butyl hydroquinone (TBHQ) inhibits the entry of influenza H3 HA by binding to the stem loop of HA and stabilizing the neutral pH conformation of HA, thereby disrupting the membrane fusion step. Based on amino acid sequence, structure and immunogenicity, H7 is a related Group 2 HA. In this work we show, using a pseudovirus entry assay, that TBHQ inhibits H7 HA-mediated entry, as well as H3 HA-mediated entry, with an IC50 ~ 6 µM. Using NMR, we show that TBHQ binds to the H7 stem loop region. STD NMR experiments indicate that the aromatic ring of TBHQ makes extensive contact with the H7 HA surface. Limited proteolysis experiments indicate that TBHQ inhibits influenza entry by stabilizing the H7 HA neutral pH conformation. Together, this work suggests that the stem loop region of H7 HA is an attractive target for therapeutic intervention and that TBHQ, which is a widely used food preservative, is a promising lead compound.
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Affiliation(s)
- Aleksandar Antanasijevic
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Han Cheng
- Department of Microbiology & Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Duncan J. Wardrop
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Lijun Rong
- Department of Microbiology & Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Michael Caffrey
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
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27
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Abstract
In influenza, the envelope protein hemagglutinin (HA) plays a critical role in viral entry by first binding to sialic acid receptors on the cell surface and subsequently mediating fusion of the viral and target membranes. In this work, the receptor binding properties of influenza A HA from different subtypes (H1 A/California/04/09, H5 A/Vietnam/1205/04, H5 A/bar-headed goose/Qinghai/1A/05, and H9 A/Hong Kong/1073/99) have been characterized by NMR spectroscopy. Using saturation transfer difference (STD) NMR, we find that all HAs bind to the receptor analogs 2,3-sialyllactose and 2,6-sialyllactose, with subtle differences in the binding mode. Using competition STD NMR, we determine the receptor preferences for the HA subtypes. We find that H5-Qinghai and H9-Hong Kong HA bind to both receptor analogs with similar affinity. On the other hand, H1 exhibits a clear preference for 2,6-sialyllactose while H5-Vietnam exhibits a clear preference for 2,3-sialyllactose. Together, these results are interpreted within the context of differences in both the amino acid sequence and structures of HA from the different subtypes in determining receptor preference.
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Affiliation(s)
- Christopher McCullough
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Minxiu Wang
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Lijun Rong
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
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28
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Abstract
In severe acute respiratory syndrome coronavirus, the envelope heptad repeat 2 (HR2) plays a critical role in viral entry. Moreover, HR2 is both the target for novel antiviral therapies and, as an isolated peptide, presents a potential antiviral therapeutic. The structure of HR2, as determined by NMR spectroscopy in the presence of the co-solvent trifluoroethanol (TFE), is a trimer of parallel helices, whereas the structure of HR2, as determined by X-ray crystallography, is a tetramer of anti-parallel helices. In this work, we added a nitroxide spin label to the N-terminal region of HR2 and used paramagnetic relaxation enhancement to assess the orientation of the HR2 helices under different solution conditions. We find that the relaxation effects are consistent with an orientation corresponding to a trimer of parallel helices in both the presence and absence of TFE. This work suggests that the different orientation and oligomerization states observed by NMR and X-ray are due to the 11 additional residues present at the N-terminus of the NMR construct.
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Affiliation(s)
| | | | - Michael Caffrey
- Department of Biochemistry & Molecular Genetics, University of Illinois at ChicagoChicago, Illinois 60607
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29
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Nomme J, Fanning AS, Caffrey M, Lye MF, Anderson JM, Lavie A. The Src homology 3 domain is required for junctional adhesion molecule binding to the third PDZ domain of the scaffolding protein ZO-1. J Biol Chem 2011; 286:43352-60. [PMID: 22030391 DOI: 10.1074/jbc.m111.304089] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Tight junctions are cell-cell contacts that regulate the paracellular flux of solutes and prevent pathogen entry across cell layers. The assembly and permeability of this barrier are dependent on the zonula occludens (ZO) membrane-associated guanylate kinase (MAGUK) proteins ZO-1, -2, and -3. MAGUK proteins are characterized by a core motif of protein-binding domains that include a PDZ domain, a Src homology 3 (SH3) domain, and a region of homology to guanylate kinase (GUK); the structure of this core motif has never been determined for any MAGUK. To better understand how ZO proteins organize the assembly of protein complexes we have crystallized the entire PDZ3-SH3-GUK core motif of ZO-1. We have also crystallized this core motif in complex with the cytoplasmic tail of the ZO-1 PDZ3 ligand, junctional adhesion molecule A (JAM-A) to determine how the activity of different domains is coordinated. Our study shows a new feature for PDZ class II ligand binding that implicates the two highly conserved Phe(-2) and Ser(-3) residues of JAM. Our x-ray structures and NMR experiments also show for the first time a role for adjacent domains in the binding of ligands to PDZ domains in the MAGUK proteins family.
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Affiliation(s)
- Julian Nomme
- Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, USA
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30
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Celigoy J, McReynolds S, Caffrey M. The SARS-CoV heptad repeat 2 exhibits pH-induced helix formation. Biochem Biophys Res Commun 2011; 412:483-6. [PMID: 21835164 PMCID: PMC7092892 DOI: 10.1016/j.bbrc.2011.07.126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 07/27/2011] [Indexed: 11/28/2022]
Abstract
The heptad repeats 1 and 2 of SARS-CoV spike, termed HR1 and HR2, play critical roles in viral entry. Moreover, HR1 and HR2 derived free peptides are inhibitors of SARS-CoV entry. In this work we used circular dichroism to show that HR2 helix formation is induced at pH 5, the pH of the endosome. In addition, we demonstrate that the HR2 helix is further stabilized at physiological ionic strengths. Together, these observations provide new insight into the mechanism of SARS-CoV entry and suggest that HR2 may be an attractive target for therapeutic intervention.
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Affiliation(s)
- Jessica Celigoy
- Department of Biochemistry & Molecular Genetics University of Illinois at Chicago, Chicago, IL 60607, USA
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31
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Celigoy J, Ramirez B, Tao L, Rong L, Yan L, Feng YR, Quinnan GV, Broder CC, Caffrey M. Probing the HIV gp120 envelope glycoprotein conformation by NMR. J Biol Chem 2011; 286:23975-81. [PMID: 21592971 DOI: 10.1074/jbc.m111.251025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The HIV envelope glycoprotein gp120 plays a critical role in virus entry, and thus, its structure is of extreme interest for the development of novel therapeutics and vaccines. To date, high resolution structural information about gp120 in complex with gp41 has proven intractable. In this study, we characterize the structural properties of gp120 in the presence and absence of gp41 domains by NMR. Using the peptide probe 12p1 (sequence, RINNIPWSEAMM), which was identified previously as an entry inhibitor that binds to gp120, we identify atoms of 12p1 in close contact with gp120 in the monomeric and trimeric states. Interestingly, the binding mode of 12p1 with gp120 is similar for clades B and C. In addition, we show a subtle difference in the binding mode of 12p1 in the presence of gp41 domains, i.e. the trimeric state, which we interpret as small differences in the gp120 structure in the presence of gp41.
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Affiliation(s)
- Jessica Celigoy
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Caffrey M. HIV envelope: challenges and opportunities for development of entry inhibitors. Trends Microbiol 2011; 19:191-7. [PMID: 21377881 PMCID: PMC3071980 DOI: 10.1016/j.tim.2011.02.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/29/2011] [Accepted: 02/03/2011] [Indexed: 01/24/2023]
Abstract
The HIV envelope proteins glycoprotein 120 (gp120) and glycoprotein 41 (gp41) play crucial roles in HIV entry, therefore they are of extreme interest in the development of novel therapeutics. Studies using diverse methods, including structural biology and mutagenesis, have resulted in a detailed model for envelope-mediated entry, which consists of multiple conformations, each a potential target for therapeutic intervention. In this review, the challenges, strategies and progress to date for developing novel entry inhibitors directed at disrupting HIV gp120 and gp41 function are discussed.
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Affiliation(s)
- Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, IL 60607, USA.
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Light SH, Minasov G, Shuvalova L, Peterson SN, Caffrey M, Anderson WF, Lavie A. A conserved surface loop in type I dehydroquinate dehydratases positions an active site arginine and functions in substrate binding. Biochemistry 2011; 50:2357-63. [PMID: 21291284 DOI: 10.1021/bi102020s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dehydroquinate dehydratase (DHQD) catalyzes the third step in the biosynthetic shikimate pathway. We present three crystal structures of the Salmonella enterica type I DHQD that address the functionality of a surface loop that is observed to close over the active site following substrate binding. Two wild-type structures with differing loop conformations and kinetic and structural studies of a mutant provide evidence of both direct and indirect mechanisms of involvement of the loop in substrate binding. In addition to allowing amino acid side chains to establish a direct interaction with the substrate, closure of the loop necessitates a conformational change of a key active site arginine, which in turn positions the substrate productively. The absence of DHQD in humans and its essentiality in many pathogenic bacteria make the enzyme a target for the development of nontoxic antimicrobials. The structures and ligand binding insights presented here may inform the design of novel type I DHQD inhibiting molecules.
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Affiliation(s)
- Samuel H Light
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States
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Yermolina MV, Wang J, Caffrey M, Rong LL, Wardrop DJ. Discovery, synthesis, and biological evaluation of a novel group of selective inhibitors of filoviral entry. J Med Chem 2011; 54:765-81. [PMID: 21204524 PMCID: PMC3081529 DOI: 10.1021/jm1008715] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Herein, we report the development of an antifiloviral screening system, based on a pseudotyping strategy, and its application in the discovery of a novel group of small molecules that selectively inhibit the Ebola and Marburg glycoprotein (GP)-mediated infection of human cells. Using Ebola Zaire GP-pseudotyped HIV particles bearing a luciferase reporter gene and 293T cells, a library of 237 small molecules was screened for inhibition of GP-mediated viral entry. From this assay, lead compound 8a was identified as a selective inhibitor of filoviral entry with an IC(50) of 30 μM. To analyze functional group requirements for efficacy, a structure-activity relationship analysis of this 3,5-disubstituted isoxazole was then conducted with 56 isoxazole and triazole derivatives prepared using "click" chemistry. This study revealed that while the isoxazole ring can be replaced by a triazole system, the 5-(diethylamino)acetamido substituent found in 8a is required for inhibition of viral-cell entry. Variation of the 3-aryl substituent provided a number of more potent antiviral agents with IC(50) values ranging to 2.5 μM. Lead compound 8a and three of its derivatives were also found to block the Marburg glycoprotein (GP)-mediated infection of human cells.
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Affiliation(s)
- Maria V. Yermolina
- Department of Chemistry, University of Illinois, 845 West Taylor Street, Chicago, Illinois 60607
| | - Jizhen Wang
- Department of Microbiology & Immunology, University of Illinois at Chicago, 835 South Wolcott, Chicago, Illinois 60612
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S Ashland, Chicago, IL 60607
| | - Lijun L. Rong
- Department of Microbiology & Immunology, University of Illinois at Chicago, 835 South Wolcott, Chicago, Illinois 60612
| | - Duncan J. Wardrop
- Department of Chemistry, University of Illinois, 845 West Taylor Street, Chicago, Illinois 60607
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Light SH, Minasov G, Shuvalova L, Duban ME, Caffrey M, Anderson WF, Lavie A. Insights into the mechanism of type I dehydroquinate dehydratases from structures of reaction intermediates. J Biol Chem 2010; 286:3531-9. [PMID: 21087925 DOI: 10.1074/jbc.m110.192831] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The biosynthetic shikimate pathway consists of seven enzymes that catalyze sequential reactions to generate chorismate, a critical branch point in the synthesis of the aromatic amino acids. The third enzyme in the pathway, dehydroquinate dehydratase (DHQD), catalyzes the dehydration of 3-dehydroquinate to 3-dehydroshikimate. We present three crystal structures of the type I DHQD from the intestinal pathogens Clostridium difficile and Salmonella enterica. Structures of the enzyme with substrate and covalent pre- and post-dehydration reaction intermediates provide snapshots of successive steps along the type I DHQD-catalyzed reaction coordinate. These structures reveal that the position of the substrate within the active site does not appreciably change upon Schiff base formation. The intermediate state structures reveal a reaction state-dependent behavior of His-143 in which the residue adopts a conformation proximal to the site of catalytic dehydration only when the leaving group is present. We speculate that His-143 is likely to assume differing catalytic roles in each of its observed conformations. One conformation of His-143 positions the residue for the formation/hydrolysis of the covalent Schiff base intermediates, whereas the other conformation positions the residue for a role in the catalytic dehydration event. The fact that the shikimate pathway is absent from humans makes the enzymes of the pathway potential targets for the development of non-toxic antimicrobials. The structures and mechanistic insight presented here may inform the design of type I DHQD enzyme inhibitors.
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Affiliation(s)
- Samuel H Light
- Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Sen J, Yan T, Wang J, Rong L, Tao L, Caffrey M. Alanine scanning mutagenesis of HIV-1 gp41 heptad repeat 1: insight into the gp120-gp41 interaction. Biochemistry 2010; 49:5057-65. [PMID: 20481578 DOI: 10.1021/bi1005267] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
On the basis of mutagenesis, biochemical, and structural studies, heptad repeat 1 of HIV gp41 (HR1) has been shown to play numerous critical roles in HIV entry, including interacting with gp120 in prefusion states and interacting with gp41 heptad repeat 2 (HR2) in the fusion state. Moreover, HR1 is the site of therapeutic intervention by enfuviritide, a peptide analogue of HR2. In this study, the functional importance of each amino acid residue in gp41 HR1 has been systematically examined by alanine scanning mutagenesis, with subsequent characterization of the mutagenic effects on folding (as measured by incorporation into virions), association with gp120, and membrane fusion. The mutational effects on entry can be grouped into three classes: (1) wild type (defined as >40% of wild-type entry), (2) impaired (defined as 5-40% of wild-type entry), and (3) nonfunctional (defined as <5% of wild-type entry). Interestingly, the majority of HR1 mutations (77%) exhibit impaired or nonfunctional entry. Surprisingly, effects of mutations on folding, association, or fusion are not correlated to heptad position; however, folding defects are most often found in the N-terminal region of HR1. Moreover, disruption of the gp41-gp120 interaction is correlated to the C-terminal region of HR1, suggesting that this region interacts most closely with gp120. In summary, the sensitivity of gp41 HR1 to alanine substitutions suggests that even subtle changes in the local environment may severely affect envelope function, thereby strengthening the notion that HR1 is an attractive site for therapeutic intervention.
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Affiliation(s)
- Jayita Sen
- Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, USA
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McReynolds S, Jiang S, Rong L, Caffrey M. Dynamics of SARS-coronavirus HR2 domain in the prefusion and transition states. J Magn Reson 2009; 201:218-221. [PMID: 19819173 PMCID: PMC2794128 DOI: 10.1016/j.jmr.2009.09.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 09/15/2009] [Accepted: 09/17/2009] [Indexed: 05/28/2023]
Abstract
The envelope glycoproteins S1 and S2 of severe acute respiratory syndrome coronavirus (SARS-CoV) mediate viral entry by conformational change from a prefusion state to a postfusion state that enables fusion of the viral and target membranes. In this work we present the characterization of the dynamic properties of the SARS-CoV S2-HR2 domain (residues 1141-1193 of S) in the prefusion and newly discovered transition states by NMR (15)N relaxation studies. The dynamic properties of the different states, which are stabilized under different experimental conditions, extend the current model of viral membrane fusion and give insight into the design of structure-based antagonists of SARS-CoV in particular, as well as other enveloped viruses such as HIV.
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Affiliation(s)
- Susanna McReynolds
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA
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Guo Y, Tisoncik J, McReynolds S, Farzan M, Prabhakar BS, Gallagher T, Rong L, Caffrey M. Identification of a new region of SARS-CoV S protein critical for viral entry. J Mol Biol 2009; 394:600-5. [PMID: 19853613 PMCID: PMC2794126 DOI: 10.1016/j.jmb.2009.10.032] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/29/2009] [Accepted: 10/14/2009] [Indexed: 11/19/2022]
Abstract
Infection by severe acute respiratory syndrome coronavirus (SARS-CoV) is initiated by specific interactions between the SARS-CoV spike (S) protein and its receptor ACE2. In this report, we screened a peptide library representing the SARS-CoV S protein sequence using a human immunodeficiency virus-based pseudotyping system to identify specific regions that affect viral entry. One of the 169 peptides screened, peptide 9626 (S residues 217–234), inhibited SARS-CoV S-mediated entry of the pseudotyped virions in 293T cells expressing a functional SARS-CoV receptor (human angiotensin-converting enzyme 2) in a dose-dependent manner (IC50 ∼ 11 μM). Alanine scanning mutagenesis was performed to assess the roles of individual residues within this region of S, which was previously uncharacterized. The effects included significant reductions in expression (K223A), viral incorporation (L218A, I230A, and N232A), and reduced viral entry (L224A, L226A, I228A, T231A, and F233A). Taken together, these results reveal a new region of the S protein that is crucial for SARS-CoV entry.
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Affiliation(s)
- Ying Guo
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Jennifer Tisoncik
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Susanna McReynolds
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Michael Farzan
- Partners AIDS Research Center, 65 Landsdowne Street, Cambridge, MA 02139, USA
| | - Bellur S. Prabhakar
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Thomas Gallagher
- Department of Microbiology and Immunology, Loyola University Medical Center, 2160 South First Avenue, Maywood, IL 60153, USA
| | - Lijun Rong
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA
- Corresponding author.
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Rumschlag-Booms E, Guo Y, Wang J, Caffrey M, Rong L. Comparative analysis between a low pathogenic and a high pathogenic influenza H5 hemagglutinin in cell entry. Virol J 2009; 6:76. [PMID: 19515258 PMCID: PMC2699337 DOI: 10.1186/1743-422x-6-76] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 06/10/2009] [Indexed: 11/10/2022] Open
Abstract
Avian influenza viruses continue to threaten globally with pandemic potential. The first step in a potential pandemic is the ability of the virus to enter human cells which is mediated by the viral surface glycoprotein hemagglutinin (HA). Viral entry of influenza is dependent upon the processing of the HA0 polypeptide precursor protein into HA1 and HA2 which is mediated by host cellular proteases. The sequence of the cleavage site which is recognized by host proteases has been linked with pathogenesis of various influenza viruses. Here we examined the effects of cleavage site sequences between a highly pathogenic H5N1 strain and a low pathogenic H5N2 strain to determine their effects on viral entry. From this analysis we determined that at the level of viral entry, the only observed difference between the low and high pathogenic strains is their ability to be cleaved by host cellular proteases.
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Affiliation(s)
- Emily Rumschlag-Booms
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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40
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Aigbirhio FI, Allen P, Andersson S, Anton M, Barron D, Bloom AJ, Botting NP, Brandau W, Brichard L, Brown JA, Brown RT, Cable KM, Caffrey M, Carroll MA, Chaplin DJ, Coissard V, Cuyckens F, Demmer O, Dijkgraaf I, Dyke AM, Gill DM, Hall KA, Hester AJ, Hickey M, Irvine S, Janssen C, Kerr WJ, Kessler H, Kingston LP, Landreau C, Lawrie KWM, Lloyd-Jones G, Loaring H, Lockley WJS, Marshall LJ, Mo B, Moseley JD, Murrell VL, Nilsson GN, Oekonomopulos R, Pinney KG, Pleasance S, Raddatz S, Rees AT, Reid RG, Renny JS, Robert F, Rustidge D, Schumacher U, Schwaiger DM, Sharma S, Soloviev D, Spivey AC, Sriram M, Thijssen J, Tseng CC, Verluyten W, Viton F, Vliegen M, Weldon H, Wester HJ, Wilkinson DJ, Williams JMJ, Williamson G, Willis CL, Yan R. Abstracts of the 17th International Isotope Society (UK group) Symposium Synthesis and Applications of Labelled Compounds 2008. J Labelled Comp Radiopharm 2009. [DOI: 10.1002/jlcr.1590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Guo Y, Rumschlag-Booms E, Wang J, Xiao H, Yu J, Wang J, Guo L, Gao GF, Cao Y, Caffrey M, Rong L. Analysis of hemagglutinin-mediated entry tropism of H5N1 avian influenza. Virol J 2009; 6:39. [PMID: 19341465 PMCID: PMC2679739 DOI: 10.1186/1743-422x-6-39] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Accepted: 04/02/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Avian influenza virus H5N1 is a major concern as a potential global pandemic. It is thought that multiple key events must take place before efficient human-to-human transmission of the virus occurs. The first step in overcoming host restriction is viral entry which is mediated by HA, responsible for both viral attachment and viral/host membrane fusion. HA binds to glycans-containing receptors with terminal sialic acid (SA). It has been shown that avian influenza viruses preferentially bind to alpha2,3-linked SAs, while human influenza A viruses exhibit a preference for alpha2,6-linked SAs. Thus it is believed the precise linkage of SAs on the target cells dictate host tropism of the viruses. RESULTS We demonstrate that H5N1 HA/HIV pseudovirus can efficiently transduce several human cell lines including human lung cells. Interestingly, using a lectin binding assay we show that the presence of both alpha2,6-linked and alpha2,3-linked SAs on the target cells does not always correlate with efficient transduction. Further, HA substitutions of the residues implicated in switching SA-binding between avian and human species did not drastically affect HA-mediated transduction of the target cells or target cell binding. CONCLUSION Our results suggest that a host factor(s), which is yet to be identified, is required for H5N1 entry in the host cells.
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Affiliation(s)
- Ying Guo
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Abstract
The importance of the N-terminal region of HIV gp120 conserved domain 1 (gp120-C1) to envelope function has been examined by alanine-scanning mutagenesis and subsequent characterization of the mutagenic effects on viral entry; envelope expression, processing, and incorporation; and gp120 association with gp41. With respect to the wild-type gp120, mutational effects on viral entry fall into two classes: functional, as defined by >20% entry with respect to wild type, and impaired, as defined by <20% entry with respect to wild type. Based on Western blot analyses of cell lysates and virions, the entry impairment of W35A, V38A, Y39A, Y40A, G41A, V42A, and I52A is due primarily to disruption of envelope processing. The entry impairment of P43A and W45A is apparently due to a combination of effects on processing and incorporation into virions. In contrast, the entry impairment of V44A and F53A is primarily due to disruption of the gp120-gp41 interaction, which results in dissociation of gp120 from the virion. We present a model for gp120-C1 interactions with gp120-C5 and the gp41 disulfide loop in unprocessed gp160 and processed gp120/gp41.
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Affiliation(s)
- Jizhen Wang
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Lavie A, Su Y, Ghassemi M, Novak RM, Caffrey M, Sekulic N, Monnerjahn C, Konrad M, Cook JL. Restoration of the antiviral activity of 3'-azido-3'-deoxythymidine (AZT) against AZT-resistant human immunodeficiency virus by delivery of engineered thymidylate kinase to T cells. J Gen Virol 2008; 89:1672-1679. [PMID: 18559937 DOI: 10.1099/vir.0.2008/000273-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Emergence of antiviral drug resistance is a major challenge to human immunodeficiency virus (HIV) therapy. The archetypal example of this problem is loss of antiviral activity of the nucleoside analogue 3'-azido-3'-deoxythymidine (AZT), caused by mutations in reverse transcriptase (RT), the viral polymerase. AZT resistance results from an imbalance between rates of AZT-induced proviral DNA chain termination and RT-induced excision of the chain-terminating nucleotide. Conversion of the AZT prodrug from its monophosphorylated to diphosphorylated form by human thymidylate kinase (TMPK) is inefficient, resulting in accumulation of the monophosphorylated AZT metabolite (AZT-MP) and a low concentration of the active triphosphorylated metabolite (AZT-TP). We reasoned that introduction of an engineered, highly active TMPK into T cells would overcome this functional bottleneck in AZT activation and thereby shift the balance of AZT activity sufficiently to block replication of formerly AZT-resistant HIV. Molecular engineering was used to link highly active, engineered TMPKs to the protein transduction domain of Tat for direct cell delivery. Combined treatment of HIV-infected T cells with AZT and these cell-permeable, engineered TMPKs restored AZT-induced repression of viral production. These results provide an experimental basis for the development of new strategies to therapeutically increase the intracellular concentrations of active nucleoside analogue metabolites as a means to overcome emerging drug resistance.
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Affiliation(s)
- Arnon Lavie
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Ying Su
- Section of Infectious Diseases, Immunology and International Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Mahmood Ghassemi
- Section of Infectious Diseases, Immunology and International Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Richard M Novak
- Section of Infectious Diseases, Immunology and International Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Michael Caffrey
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Nikolina Sekulic
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Christian Monnerjahn
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Manfred Konrad
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - James L Cook
- Section of Infectious Diseases, Immunology and International Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
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McReynolds S, Jiang S, Guo Y, Celigoy J, Schar C, Rong L, Caffrey M. Characterization of the prefusion and transition states of severe acute respiratory syndrome coronavirus S2-HR2. Biochemistry 2008; 47:6802-8. [PMID: 18540634 DOI: 10.1021/bi800622t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The envelope glycoproteins of the class I family, which include human immunodeficiency virus (HIV), influenza, and severe acute respiratory syndrome coronavirus (SARS-CoV), mediate viral entry by first binding to their cellular receptors and subsequently inducing fusion of the viral and cellular membranes. In the case of SARS-CoV, heptad repeat domains of the envelope glycoprotein, termed S2-HR1 and S2-HR2, are thought to undergo structural changes from a prefusion state, in which S2-HR1 and S2-HR2 do not interact, to a postfusion state in which S2-HR1 and S2-HR2 associate to form a six-helix bundle. In the present work, the structural and dynamic properties of S2-HR2 have been characterized. Evidence is presented for an equilibrium between a structured trimer thought to represent a prefusion state and an ensemble of unstructured monomers thought to represent a novel transition state. A model for viral entry is presented in which S2-HR2 is in a dynamic equilibrium between an ensemble of unstructured monomers in the transition state and a structured trimer in the prefusion state. Conversion from the prefusion state to the postfusion state requires passage through the transition state, a state that may give insight into the design of structure-based antagonists of SARS-CoV in particular, as well as other enveloped viruses in general.
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Affiliation(s)
- Susanna McReynolds
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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46
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Boyle-Roden E, Hoefer N, Dey KK, Grandinetti PJ, Caffrey M. High resolution 1H NMR of a lipid cubic phase using a solution NMR probe. J Magn Reson 2007; 189:13-9. [PMID: 17855136 DOI: 10.1016/j.jmr.2007.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 08/08/2007] [Accepted: 08/11/2007] [Indexed: 05/17/2023]
Abstract
The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of (1)H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional (1)H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, L-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that L-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer.
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Affiliation(s)
- E Boyle-Roden
- Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
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47
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Abstract
The importance of the HIV gp41 conserved disulfide loop to envelope function has been examined by mutational and functional analyses. Based on a luciferase-reporter entry assay, mutants gp41-CC/AA (C598A/C604A) and gp41-Delta (deletion of residues 596-606) result in a nonfunctional envelope protein. Western blot analysis shows both mutants to be properly expressed but not processed to form gp120 and gp41, which explains their nonfunctionality. The presence of mutant gp160 on the cell surface, as well as their ability to bind to sCD4, suggests that the mutations have disrupted processing at the furin recognition site encoded within the gp120 conserved domain 5, without resulting in an overall misfolding of the protein. With respect to the furin recognition site, the mutations are sequentially distant, which implies that the gp41 disulfide loop is interacting with gp120 C5 in gp160. In addition, we have modeled the gp120-gp41 interaction in unprocessed precursor gp160 using structural data available for gp120 and gp41 domains in isolation, supplemented by mutagenesis data. We suggest that the mutations have altered the interaction between gp120 C5 and the gp41 disulfide loop, resulting in decreased accessibility of the furin recognition site and implying that the interaction between the gp120 C5 and gp41 loop is a conformational requirement for gp160 processing. The sensitivity of this interaction could be exploited in future antivirals designed to disrupt HIV pathogenesis by disrupting gp160 processing.
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Affiliation(s)
- Jayita Sen
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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48
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Abstract
The coxsackievirus and adenovirus receptor (CAR) mediates entry of coxsackievirus and adenovirus. CAR possesses an extracellular region that is comprised of 2 immunoglobulin domains termed CAR-D1 and CAR-D2. In the present work, the solution structure of CAR-D2, consisting of residues 142-235 of human CAR, has been determined by NMR spectroscopy. CAR-D2 is shown to be a beta-sandwich motif comprised of two beta-sheets, which are stabilized by two disulfide bonds. The first beta-sheet is comprised of beta-strands A, B, and E, and the second beta-sheet is comprised of beta-strands C, F, and G. A relatively hydrophobic helix is found between beta-strands C and E, which replaces beta-strand D of the classical c-type immunoglobulin fold.
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Affiliation(s)
- Shaokai Jiang
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Cherezov V, Yamashita E, Liu W, Zhalnina M, Cramer WA, Caffrey M. In meso structure of the cobalamin transporter, BtuB, at 1.95 A resolution. J Mol Biol 2006; 364:716-34. [PMID: 17028020 PMCID: PMC1808586 DOI: 10.1016/j.jmb.2006.09.022] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 08/31/2006] [Accepted: 09/05/2006] [Indexed: 11/30/2022]
Abstract
Crystals of the apo form of the vitamin B12 and colicin receptor, BtuB, that diffract to 1.95 A have been grown by the membrane-based in meso technique. The structure of the protein differs in several details from that of its counterpart grown by the more traditional, detergent-based (in surfo) method. Some of these differences include (i) the five N-terminal residues are resolved in meso, (ii) residues 57-62 in the hatch domain and residues 574-581 in loop 21-22 are disordered in meso and are ordered in surfo, (iii) residues 278-287 in loop 7-8 are resolved in meso, (iv) residues 324-331 in loop 9-10, 396-411 in loop 13-14, 442-458 in loop 15-16 and 526-541 in loop 19-20 have large differences in position between the two crystal forms, as have residues 86-96 in the hatch domain, and (v) the conformation of residues 6 and 7 in the Ton box (considered critical to signal transduction and substrate transport) are entirely different in the two structures. Importantly, the in meso orientation of residues 6 and 7 is similar to that of the vitamin B12-charged state. These data suggest that the "substrate-induced" 180 degrees -rotation of residues 6 and 7 reported in the literature may not be a unique signalling event. The extent to which these findings agree with structural, dynamic and functional insights gleaned from site-directed spin labelling and electron paramagnetic resonance measurements is evaluated. Packing in in meso grown crystals is dense and layered, consistent with the current model for crystallogenesis of membrane proteins in lipidic mesophases. Layered packing has been used to locate the transmembrane hydrophobic surface of the protein. Generally, this is consistent with tryptophan, tyrosine, lipid and CalphaB-factor distributions in the protein, and with predictions based on transfer free energy calculations.
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Affiliation(s)
- V. Cherezov
- Chemistry, The Ohio State University, Columbus, OH 43210, USA
| | - E. Yamashita
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - W. Liu
- Biophysics, The Ohio State University, Columbus, OH 43210, USA
| | - M. Zhalnina
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - WA Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - M. Caffrey
- Chemical and Environmental Science Department and Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
- Biochemistry, The Ohio State University, Columbus, OH 43210, USA
- Biophysics, The Ohio State University, Columbus, OH 43210, USA
- Chemistry, The Ohio State University, Columbus, OH 43210, USA
- *Corresponding author: M. Cafffey, E-mail:
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Abstract
The HIV and SIV gp41 ectodomains are extremely stable to chemical and thermal denaturation and the observed stability has been proposed to be an important thermodynamic driving force for gp41-mediated fusion of the viral and target cell membranes. The importance of the disulphide bond and surrounding residues within the HIV gp41 loop have been assayed by DSC studies of wild type and mutant HIV gp41. Based on the thermal transition temperature, the disulphide bond and surrounding residues do not contribute to the thermal stability of gp41 and thus do not contribute to gp41-mediated membrane fusion.
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Affiliation(s)
- Amy Jacobs
- Department of Biochemistry and Molecular Genetics,University of Illinois at Chicago, Chicago, IL 60607, USA
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