title: Different host cell proteases activate the SARS-coronavirus spike-protein for cell-cell and virus-cell fusion.
abstract: Severe acute respiratory syndrome coronavirus (SARS-CoV) poses a considerable threat to human health. Activation of the viral spike (S)-protein by host cell proteases is essential for viral infectivity. However, the cleavage sites in SARS-S and the protease(s) activating SARS-S are incompletely defined. We found that R667 was dispensable for SARS-S-driven virus-cell fusion and for SARS-S-activation by trypsin and cathepsin L in a virus-virus fusion assay. Mutation T760R, which optimizes the minimal furin consensus motif 758-RXXR-762, and furin overexpression augmented SARS-S activity, but did not result in detectable SARS-S cleavage. Finally, SARS-S-driven cell-cell fusion was independent of cathepsin L, a protease essential for virus-cell fusion. Instead, a so far unknown leupeptin-sensitive host cell protease activated cellular SARS-S for fusion with target cells expressing high levels of ACE2. Thus, different host cell proteases activate SARS-S for virus-cell and cell-cell fusion and SARS-S cleavage at R667 and 758-RXXR-762 can be dispensable for SARS-S activation.
authors: Blood Systems Research Institute and Department of Laboratory Medicine, University of California, San Francisco, CA, USA. gsimmons@bloodsystems.org
authors: Graham
authors: G
authors: Simmons
authors: Stephanie
authors: S
authors: Bertram
authors: Ilona
authors: I
authors: Glowacka
authors: Imke
authors: I
authors: Steffen
authors: Chawaree
authors: C
authors: Chaipan
authors: Juliet
authors: J
authors: Agudelo
authors: Kai
authors: K
authors: Lu
authors: Andrew J
authors: AJ
authors: Rennekamp
authors: Heike
authors: H
authors: Hofmann
authors: Paul
authors: P
authors: Bates
authors: Stefan
authors: S
authors: Pöhlmann
mesh_terms: D002459:Cell Fusion; D002460:Cell Line; D045683:Furin / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D006801:Humans; D007976:Leupeptins; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000502:physiology*; D014357:Trypsin; D053586:Virus Internalization
chemical_list: D007976:Leupeptins; D010447:Peptide Hydrolases; D014357:Trypsin; D045683:Furin; C032854:leupeptin