Mini-plasmin Found in the Epithelial Cells of Bronchioles Triggers Infection by Broad-Spectrum Influenza A Viruses and Sendai Virus

Eur J Biochem. 2001 May;268(10):2847-55. doi: 10.1046/j.1432-1327.2001.02166.x.


Extracellular cleavage of virus envelope fusion glycoproteins by host cellular proteases is a prerequisite for the infectivity of mammalian and nonpathogenic avian influenza viruses, and Sendai virus. Here we report a protease present in the airway that, like tryptase Clara, can process influenza A virus haemagglutinin and Sendai virus envelope fusion glycoprotein. This protease was extracted from the membrane fraction of rat lungs, purified and then identified as a mini-plasmin. Mini-plasmin was distributed predominantly in the epithelial cells of the upward divisions of bronchioles and potentiated the replication of broad-spectrum influenza A viruses and Sendai virus, even that of the plasmin-insensitive influenza A virus strain. In comparison with plasmin, its increased hydrophobicity, leading to its higher local concentrations on membranes, and decreased molecular mass may enable mini-plasmin to gain ready access to the cleavage sites of various haemagglutinins and fusion glycoproteins after expression of these viral proteins on the cell surface. These findings suggest that mini-plasmin in the airway may play a pivotal role in the spread of viruses and their pathogenicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Western
  • Bronchi / cytology*
  • Bronchi / metabolism
  • Bronchi / pathology
  • Bronchi / virology
  • Cell Membrane / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoresis, Polyacrylamide Gel
  • Epithelial Cells / chemistry*
  • Fibrinolysin / chemistry*
  • Humans
  • Immunohistochemistry
  • Infections*
  • Influenza A virus / metabolism*
  • Isoflurophate / pharmacology
  • Lung / metabolism
  • Lung / pathology
  • Lung / virology
  • Male
  • Molecular Sequence Data
  • Peptide Fragments / chemistry*
  • Rats
  • Rats, Wistar
  • Respirovirus / metabolism*
  • Sequence Analysis, Protein
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Viral Envelope Proteins / chemistry
  • Viral Envelope Proteins / metabolism


  • Peptide Fragments
  • Viral Envelope Proteins
  • miniplasmin
  • Isoflurophate
  • Fibrinolysin