Pseudomonas aeruginosa ExsA Regulates a Metalloprotease, ImpA, That Inhibits Phagocytosis of Macrophages

Infect Immun. 2019 Nov 18;87(12):e00695-19. doi: 10.1128/IAI.00695-19. Print 2019 Dec.

Abstract

Pseudomonas aeruginosa is an opportunistic pathogenic bacterium whose type III secretion system (T3SS) plays a critical role in acute infections. Translocation of the T3SS effectors into host cells induces cytotoxicity. In addition, the T3SS promotes the intracellular growth of P. aeruginosa during host infections. The T3SS regulon genes are regulated by an AraC-type regulator, ExsA. In this study, we found that an extracellular metalloprotease encoded by impA (PA0572) is under the regulation of ExsA. An ExsA consensus binding sequence was identified upstream of the impA gene, and direct binding of the site by ExsA was demonstrated via an electrophoretic mobility shift assay. We further demonstrate that secreted ImpA cleaves the macrophage surface protein CD44, which inhibits the phagocytosis of the bacterial cells by macrophages. Combined, our results reveal a novel ExsA-regulated virulence factor that cooperatively inhibits the functions of macrophages with the T3SS.

Keywords: ExsA; ImpA; Pseudomonas aeruginosa; macrophages; phagocytosis; type III secretion system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cell Line, Tumor
  • Electrophoretic Mobility Shift Assay
  • Female
  • Gene Expression Regulation, Bacterial / genetics
  • HeLa Cells
  • Humans
  • Hyaluronan Receptors / metabolism
  • Macrophages / immunology*
  • Metalloproteases / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • Phagocytosis / immunology*
  • Protein Binding
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / immunology*
  • Serine Endopeptidases / metabolism*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Type III Secretion Systems / genetics
  • Type III Secretion Systems / metabolism

Substances

  • Bacterial Proteins
  • ExsA protein, Pseudomonas aeruginosa
  • Hyaluronan Receptors
  • Trans-Activators
  • Type III Secretion Systems
  • Metalloproteases
  • Serine Endopeptidases