title: Toremifene interacts with and destabilizes the Ebola virus glycoprotein.
abstract: Ebola viruses (EBOVs) are responsible for repeated outbreaks of fatal infections, including the recent deadly epidemic in West Africa. There are currently no approved therapeutic drugs or vaccines for the disease. EBOV has a membrane envelope decorated by trimers of a glycoprotein (GP, cleaved by furin to form GP1 and GP2 subunits), which is solely responsible for host cell attachment, endosomal entry and membrane fusion. GP is thus a primary target for the development of antiviral drugs. Here we report the first, to our knowledge, unliganded structure of EBOV GP, and high-resolution complexes of GP with the anticancer drug toremifene and the painkiller ibuprofen. The high-resolution apo structure gives a more complete and accurate picture of the molecule, and allows conformational changes introduced by antibody and receptor binding to be deciphered. Unexpectedly, both toremifene and ibuprofen bind in a cavity between the attachment (GP1) and fusion (GP2) subunits at the entrance to a large tunnel that links with equivalent tunnels from the other monomers of the trimer at the three-fold axis. Protein–drug interactions with both GP1 and GP2 are predominately hydrophobic. Residues lining the binding site are highly conserved among filoviruses except Marburg virus (MARV), suggesting that MARV may not bind these drugs. Thermal shift assays show up to a 14 °C decrease in the protein melting temperature after toremifene binding, while ibuprofen has only a marginal effect and is a less potent inhibitor. These results suggest that inhibitor binding destabilizes GP and triggers premature release of GP2, thereby preventing fusion between the viral and endosome membranes. Thus, these complex structures reveal the mechanism of inhibition and may guide the development of more powerful anti-EBOV drugs.
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Jingshan
authors.initials: J
authors.lastname: Ren
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Karl
authors.initials: K
authors.lastname: Harlos
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Jones
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Antra
authors.initials: A
authors.lastname: Zeltina
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Bowden
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.|Cellular Imaging Core, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.
authors.forename: Sergi
authors.initials: S
authors.lastname: Padilla-Parra
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Fry
authors.affiliation: Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.|Diamond Light Source Ltd, Harwell Science &Innovation Campus, Didcot, OX11 0DE, UK.
authors.forename: David I
authors.initials: DI
authors.lastname: Stuart
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000998:Antiviral Agents / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D002460:Cell Line; D017124:Conserved Sequence; D029043:Ebolavirus / Q000737:chemistry* / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007052:Ibuprofen / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008024:Ligands; D029024:Marburgvirus / Q000737:chemistry; D008561:Membrane Fusion / Q000187:drug effects; D008958:Models, Molecular; D011485:Protein Binding; D055550:Protein Stability / Q000187:drug effects; D020836:Protein Structure, Quaternary / Q000187:drug effects; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D013696:Temperature; D017312:Toremifene / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D014759:Viral Envelope Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D053585:Virus Attachment / Q000187:drug effects
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000998:Antiviral Agents; D008024:Ligands; D021122:Protein Subunits; D014759:Viral Envelope Proteins; C113189:envelope glycoprotein, Ebola virus; D017312:Toremifene; D007052:Ibuprofen