title: Lysophospholipase A activity of Pseudomonas aeruginosa type III secretory toxin ExoU.
abstract: Acute lung injury in Pseudomonas aeruginosa pneumonia depends primarily on ExoU that is delivered directly into the eukaryotic cell via the type III secretion system. Recent studies demonstrated that ExoU has lipase activity, and that the cytotoxicity of ExoU is dependent on its patatin-like phospholipase domain. We investigated the phospholipase A (PLA) activity of ExoU. ExoU, but not non-catalytic ExoU-S142A, preincubated with the BEAS-2B cell lysate showed a weak increase of Ca(2+)-independent PLA(2) activity. When activated ExoU was mixed with secretory type PLA(2), more phospholipase activity was observed, suggesting that ExoU has lysophospholipase A (lysoPLA) activity. A significant increase in lysoPLA activity was also observed. Glycerol enhanced this activity and inhibitors of iPLA(2) suppressed ExoU's lysoPLA activity. Our results suggest that ExoU has a potent lysoPLA activity that requires the presence of the catalytically active site Ser(142) with an unknown eukaryotic cell factor(s) for its activation.
authors.affiliation: Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA 94143-0542, USA.
authors.forename: Miki
authors.initials: M
authors.lastname: Tamura
authors.forename: Temitayo
authors.initials: T
authors.lastname: Ajayi
authors.forename: Leonard R
authors.initials: LR
authors.lastname: Allmond
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Moriyama
authors.forename: Jeanine P
authors.initials: JP
authors.lastname: Wiener-Kronish
authors.forename: Teiji
authors.initials: T
authors.lastname: Sawa
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D004492:Edetic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008245:Lysophospholipase / Q000378:metabolism*; D017830:Octoxynol / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004791:Enzyme Inhibitors; C111749:pseudomonas exoprotein A protein, Pseudomonas aeruginosa; D000255:Adenosine Triphosphate; D017830:Octoxynol; D004492:Edetic Acid; D010741:Phospholipases A; D008245:Lysophospholipase; D005990:Glycerol; D002118:Calcium