Pseudomonas aeruginosa exoenzymes U and Y induce a transmissible endothelial proteinopathy.

We tested the hypothesis that Pseudomonas aeruginosa type 3 secretion system effectors exoenzymes Y and U (ExoY and ExoU) induce release of a high-molecular-weight endothelial tau, causing transmissible cell injury characteristic of an infectious proteinopathy. Both the bacterial delivery of ExoY and ExoU and the conditional expression of an activity-attenuated ExoU induced time-dependent pulmonary microvascular endothelial cell gap formation that was paralleled by the loss of intracellular tau and the concomitant appearance of high-molecular-weight extracellular tau. Transfer of the high-molecular-weight tau in filtered supernatant to naïve endothelial cells resulted in intracellular accumulation of tau clusters, which was accompanied by cell injury, interendothelial gap formation, decreased endothelial network stability in Matrigel, and increased lung permeability.

Ubiquitin and ubiquitin-modified proteins activate the Pseudomonas aeruginosa T3SS cytotoxin, ExoU.

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that possesses a type III secretion system (T3SS) critical for evading innate immunity and establishing acute infections in compromised patients. Our research has focused on the structure-activity relationships of ExoU, the most toxic and destructive type III effector produced by P. aeruginosa.

Induced conformational changes in the activation of the Pseudomonas aeruginosa type III toxin, ExoU.

ExoU is a 74-kDa, water-soluble toxin injected directly into mammalian cells through the type III secretion system of the opportunistic pathogen, Pseudomonas aeruginosa. Previous studies have shown that ExoU is a Ca(2+)-independent phospholipase that requires a eukaryotic protein cofactor. One protein capable of activating ExoU and serving as a required cofactor was identified by biochemical and proteomic methods as superoxide dismutase (SOD1).

Activation of ExoU phospholipase activity requires specific C-terminal regions.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that utilizes a type III secretion system to subvert host innate immunity. Of the 4 known effector proteins injected into eukaryotic cells, ExoS and ExoU are cytotoxic. The cytotoxic phenotype of ExoU depends on the enzymatic activity of the patatin-like phospholipase A(2) domain localized to the N-terminal half of the protein.

A sensitive fluorescence-based assay for the detection of ExoU-mediated PLA(2) activity.

Background: Pseudomonas aeruginosa is an opportunistic pathogen that causes disease in immunocompromised individuals, burn victims, and cystic fibrosis patients. Strains that secrete ExoU induce host cell lysis and damage epithelial tissue, which can lead to severe outcomes including sepsis and mortality. ExoU is classified as an A2 phospholipase (PLA(2)) and activity is dependent on the eukaryotic protein, superoxide dismutase 1 (SOD1).