TMPRSS2 and furin are both essential for proteolytic activation and spread of SARS-CoV-2 in human airway epithelial cells and provide promising drug targets

Dorothea Bestle; Miriam Ruth Heindl; Hannah Limburg; Thuy Van Lam van; Oliver Pilgram; Hong Moulton; David A. Stein; Kornelia Hardes; Markus Eickmann; Olga Dolnik; Cornelius Rohde; Stephan Becker; Hans-Dieter Klenk; Wolfgang Garten; Torsten Steinmetzer; Eva Böttcher-Friebertshäuser

. CC-BY-NC-ND 4.0 International license author/funder. It is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.04.15.042085 doi: bioRxiv preprint i) S must be cleaved at two sites, S1/S2 and S2', to trigger fusion of viral and cellular membranes during virus entry in order to release the virus genome into the host cell. CoV S cleavage is believed to occur sequentially, with cleavage at the S1/S2 site occurring first and subsequent cleavage at the S2′ site. Furin processes the S1/S2 site, whereas TMPRSS2 cleaves at the S2' site, and both proteases cannot compensate each other. Inhibition of either furin (ii) or TMPRSS2 (iii) or simultaneous inhibition of both proteases (iv) renders the S protein fusion-inactive and prevents virus entry. Inhibition of TMPRSS2 prevents exposure of the fusion peptide at the N-terminus of the S2' subunit (iii and iv). Inhibition of furin cleavage at the S1/S2 site may directly interfere with virus entry and membrane fusion by steric blockage of conformational changes (ii, upper scheme) or may prevent exposure of the S2' site to TMPRSS2 (ii, lower scheme). Fusion-competent S is indicated in blue, fusionincompetent S in grey.