title: Evidence that TMPRSS2 activates the severe acute respiratory syndrome coronavirus spike protein for membrane fusion and reduces viral control by the humoral immune response.
abstract: The spike (S) protein of the severe acute respiratory syndrome coronavirus (SARS-CoV) can be proteolytically activated by cathepsins B and L upon viral uptake into target cell endosomes. In contrast, it is largely unknown whether host cell proteases located in the secretory pathway of infected cells and/or on the surface of target cells can cleave SARS S. We along with others could previously show that the type II transmembrane protease TMPRSS2 activates the influenza virus hemagglutinin and the human metapneumovirus F protein by cleavage. Here, we assessed whether SARS S is proteolytically processed by TMPRSS2. Western blot analysis revealed that SARS S was cleaved into several fragments upon coexpression of TMPRSS2 (cis-cleavage) and upon contact between SARS S-expressing cells and TMPRSS2-positive cells (trans-cleavage). cis-cleavage resulted in release of SARS S fragments into the cellular supernatant and in inhibition of antibody-mediated neutralization, most likely because SARS S fragments function as antibody decoys. trans-cleavage activated SARS S on effector cells for fusion with target cells and allowed efficient SARS S-driven viral entry into targets treated with a lysosomotropic agent or a cathepsin inhibitor. Finally, ACE2, the cellular receptor for SARS-CoV, and TMPRSS2 were found to be coexpressed by type II pneumocytes, which represent important viral target cells, suggesting that SARS S is cleaved by TMPRSS2 in the lung of SARS-CoV-infected individuals. In summary, we show that TMPRSS2 might promote viral spread and pathogenesis by diminishing viral recognition by neutralizing antibodies and by activating SARS S for cell-cell and virus-cell fusion.
authors.affiliation: Institute of Virology, Hannover Medical School, 30625 Hannover, Germany.
authors.forename: Ilona
authors.initials: I
authors.lastname: Glowacka
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bertram
authors.forename: Marcel A
authors.initials: MA
authors.lastname: Müller
authors.forename: Paul
authors.initials: P
authors.lastname: Allen
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Soilleux
authors.forename: Susanne
authors.initials: S
authors.lastname: Pfefferle
authors.forename: Imke
authors.initials: I
authors.lastname: Steffen
authors.forename: Theodros Solomon
authors.initials: TS
authors.lastname: Tsegaye
authors.forename: Yuxian
authors.initials: Y
authors.lastname: He
authors.forename: Kerstin
authors.initials: K
authors.lastname: Gnirss
authors.forename: Daniela
authors.initials: D
authors.lastname: Niemeyer
authors.forename: Heike
authors.initials: H
authors.lastname: Schneider
authors.forename: Christian
authors.initials: C
authors.lastname: Drosten
authors.forename: Stefan
authors.initials: S
authors.lastname: Pöhlmann
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D054884:Host-Pathogen Interactions; D006801:Humans; D056724:Immunity, Humoral; D008562:Membrane Glycoproteins / Q000276:immunology* / Q000378:metabolism*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology* / Q000472:pathogenicity*; D012697:Serine Endopeptidases / Q000378:metabolism*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000276:immunology* / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus; D012697:Serine Endopeptidases; C421305:TMPRSS2 protein, human