Pseudomonas aeruginosa ExoS Induces Intrinsic Apoptosis in Target Host Cells in a Manner That is Dependent on its GAP Domain Activity

Sci Rep. 2018 Sep 19;8(1):14047. doi: 10.1038/s41598-018-32491-2.


Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in immunocompromised individuals and cystic fibrosis patients. ExoS and ExoT are two homologous bifunctional Type III Secretion System (T3SS) virulence factors that induce apoptosis in target host cells. They possess a GTPase Activating Protein (GAP) domain at their N-termini, which share ~76% homology, and an ADP-ribosyltransferase (ADPRT) domain at their C-termini, which target non-overlapping substrates. Both the GAP and the ADPRT domains contribute to ExoT's cytotoxicity in target epithelial cells, whereas, ExoS-induced apoptosis is reported to be primarily due to its ADPRT domain. In this report, we demonstrate that ExoS/GAP domain is both necessary and sufficient to induce mitochondrial apoptosis. Our data demonstrate that intoxication with ExoS/GAP domain leads to enrichment of Bax and Bim into the mitochondrial outer-membrane, disruption of mitochondrial membrane and release of and cytochrome c into the cytosol, which activates initiator caspase-9 and effector caspase-3, that executes cellular death. We posit that the contribution of the GAP domain in ExoS-induced apoptosis was overlooked in prior studies due to its slower kinetics of cytotoxicity as compared to ADPRT. Our data clarify the field and reveal a novel virulence function for ExoS/GAP as an inducer of apoptosis.

Publication types

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

MeSH terms

  • ADP Ribose Transferases / chemistry*
  • ADP Ribose Transferases / metabolism*
  • Apoptosis
  • Bacterial Toxins / chemistry*
  • Bacterial Toxins / metabolism*
  • Bcl-2-Like Protein 11 / metabolism
  • Caspase 3 / metabolism
  • Caspase 9 / metabolism
  • Cell Cycle Proteins / metabolism
  • Chondroitin Sulfate Proteoglycans / metabolism
  • Chromosomal Proteins, Non-Histone / metabolism
  • Cytochromes c / metabolism
  • Cytosol / metabolism
  • HeLa Cells
  • Humans
  • Mitochondria / metabolism*
  • Protein Domains
  • Pseudomonas Infections / metabolism*
  • Pseudomonas Infections / microbiology
  • Pseudomonas aeruginosa / metabolism
  • Pseudomonas aeruginosa / pathogenicity*
  • Time Factors
  • Time-Lapse Imaging


  • BCL2L11 protein, human
  • Bacterial Toxins
  • Bcl-2-Like Protein 11
  • Cell Cycle Proteins
  • Chondroitin Sulfate Proteoglycans
  • Chromosomal Proteins, Non-Histone
  • SMC3 protein, human
  • Cytochromes c
  • ADP Ribose Transferases
  • exoenzyme S
  • CASP3 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 9