Cleavage and activation of the severe acute respiratory syndrome coronavirus spike protein by human airway trypsin-like protease

J Virol. 2011 Dec;85(24):13363-72. doi: 10.1128/JVI.05300-11. Epub 2011 Oct 12.


The highly pathogenic severe acute respiratory syndrome coronavirus (SARS-CoV) poses a constant threat to human health. The viral spike protein (SARS-S) mediates host cell entry and is a potential target for antiviral intervention. Activation of SARS-S by host cell proteases is essential for SARS-CoV infectivity but remains incompletely understood. Here, we analyzed the role of the type II transmembrane serine proteases (TTSPs) human airway trypsin-like protease (HAT) and transmembrane protease, serine 2 (TMPRSS2), in SARS-S activation. We found that HAT activates SARS-S in the context of surrogate systems and authentic SARS-CoV infection and is coexpressed with the viral receptor angiotensin-converting enzyme 2 (ACE2) in bronchial epithelial cells and pneumocytes. HAT cleaved SARS-S at R667, as determined by mutagenesis and mass spectrometry, and activated SARS-S for cell-cell fusion in cis and trans, while the related pulmonary protease TMPRSS2 cleaved SARS-S at multiple sites and activated SARS-S only in trans. However, TMPRSS2 but not HAT expression rendered SARS-S-driven virus-cell fusion independent of cathepsin activity, indicating that HAT and TMPRSS2 activate SARS-S differentially. Collectively, our results show that HAT cleaves and activates SARS-S and might support viral spread in patients.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin-Converting Enzyme 2
  • Cell Line
  • Gene Expression
  • Host-Pathogen Interactions*
  • Humans
  • Membrane Glycoproteins / metabolism*
  • Peptidyl-Dipeptidase A / biosynthesis
  • Proteolysis
  • Receptors, Virus / biosynthesis
  • SARS Virus / pathogenicity*
  • Serine Endopeptidases / metabolism*
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins / metabolism*


  • Membrane Glycoproteins
  • Receptors, Virus
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins
  • Peptidyl-Dipeptidase A
  • ACE2 protein, human
  • Angiotensin-Converting Enzyme 2
  • Serine Endopeptidases
  • human airway trypsin-like protease