Pathogens responsible for nosocomial pneumonia elicit production of lung endothelial cell amyloids. These amyloids can have antimicrobial properties and be beneficial to the host, or they can have cytotoxic properties and be detrimental to the host. In the latter case, endothelial-derived amyloids may contribute to end organ dysfunction in the aftermath of critical illness. Bacterial virulence factors, such as the Pseudomonas aeruginosa type III secretion system effectors, and most notably exoenzyme Y, convert endothelial amyloids from antimicrobial to cytotoxic species. Amyloid-beta (A?) is one of the cytotoxic amyloids generated following endothelial infection. A? is released from endothelium where it becomes a transmissible and self-replicating prion cytotoxin. Our preliminary data reveals that ?-secretase activating protein plays a critical role in generating cytotoxic A?. We found ?-secretase activating protein expression in endothelial cells using non- biased microarray, RNAseq, methylation and miRNA screens, and confirmed protein expression and function in microvascular endothelium. ?-secretase activating protein deletion prevented formation of the cytotoxic A? species. Rather, following ?-secretase activating protein deletion the Pseudomonas aeruginosa- and exoenzyme Y-induced A? had antimicrobial properties. Exoenzyme Y is a promiscuous nucleotidyl cyclase that results in protein kinase A activation, which may phosphorylate A? necessary to increase its cytotoxic activity. These data suggest production of cytotoxic A? is due to two inter-related mechanisms, including an increase in ?-secretase activating protein function and the phosphorylation of A? once it is produced. Hence, this proposal tests the hypothesis that exoenzyme Y promotes the production of cytotoxic A?, dependent upon ?-secretase activating protein.
Nosocomial pneumonia represents a major cause of patient morbidity and mortality. Even after patients are released from the hospital, critically ill patients who developed infection during their hospital stay have high rates of death. In this application we investigate a mechanism of cellular injury induced by bacteria that is transmissible and self-replicating among cells in the lung, and as such, may contribute to both the short term and long term consequences of infection.
