Letter | Published:

Toremifene interacts with and destabilizes the Ebola virus glycoprotein

Nature volume 535, pages 169172 (07 July 2016) | Download Citation

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 fusion1,2,3,4,5,6,7. 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 deciphered8,9,10. 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.

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Accessions

Primary accessions

Data deposits

The atomic coordinates and structure factors have been deposited with the RCSB Protein Data Bank under accession codes 5JQ3 (native GP), 5JQ7 (GP-toremifene) and 5JQB (GP-ibuprofen).

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Acknowledgements

We thank Diamond scientists at I02 and I03 for assistance with data collection, T. S. Walter for help with crystallization and thermal-shift essay. Y.Z. was supported by the Biostruct-X project (283570) funded by the EU seventh Framework Programme (FP7), J.R. by the Wellcome Trust, and D.I.S., E.E.F. and K.H. by the UK Medical Research Council (MR/N00065X/1). This is a contribution from the UK Instruct Centre. The Wellcome Trust Centre for Human Genetics is supported by the Wellcome Trust (grant 090532/Z/09/Z). A.Z. is supported by a Marie Curie Fellowship (658363), T.A.B. is supported by the MRC (MR/L009528/1). SP-P is funded by a Nuffield Department of Medicine Leadership Fellowship. D.I.S. is a Jenner Investigator.

Author information

Author notes

    • Yuguang Zhao
    •  & Jingshan Ren

    These authors contributed equally to this work.

Affiliations

  1. Division of Structural Biology, University of Oxford, Wellcome Trust Centre for Human Genetics, Headington, Oxford OX3 7BN, UK

    • Yuguang Zhao
    • , Jingshan Ren
    • , Karl Harlos
    • , Daniel M. Jones
    • , Antra Zeltina
    • , Thomas A. Bowden
    • , Sergi Padilla-Parra
    • , Elizabeth E. Fry
    •  & David I. Stuart
  2. Cellular Imaging Core, University of Oxford, Wellcome Trust Centre for Human Genetics, Headington, Oxford OX3 7BN

    • Sergi Padilla-Parra
  3. Diamond Light Source Ltd, Harwell Science &Innovation Campus, Didcot OX11 0DE, UK

    • David I. Stuart

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Contributions

Y.Z., J.R. and D.I.S designed the project. Y.Z. made the protein and grew the crystals together with J.R., collected X-ray data and determined the structures. K.H. helped with crystal mounting and data collection. D.M.J. and S.P. carried out cell imaging experiments. A.Z. and T.A.B. provided the cDNA. Y.Z., J.R., E.E.F. and D.I.S. analysed the results and wrote the manuscript in discussions with all authors.

Competing interests

D.I.S., T.A.B. and A.Z. are listed as inventors on the International Patent Application No. PCT/GB2016/050321 ‘Filovirus therapy’.

Corresponding author

Correspondence to David I. Stuart.

Reviewer Information Nature thanks E. Saphire, W. Weissenhorn and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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DOI

https://doi.org/10.1038/nature18615

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