Effects of Pseudomonas aeruginosa bacterial membrane vesicles on human lung cell physiology

Bacterial membrane vesicles (BMVs), secreted by pathogens such as Pseudomonas aeruginosa, play a crucial role in mediating diverse host responses upon infection. As they contain cellular components, including DNA, and present pathogen-associated molecular patterns like lipopolysaccharide on their surface, BMVs are recognized by various cellular receptors, leading to the activation of immune responses in the host cell. While receptor-mediated signaling pathways activated by BMVs are well-characterized, emerging evidence suggests that BMVs also modulate host cell physiology by affecting metabolic processes. In this thesis, I demonstrate the profound impact of P. aeruginosa PA14 BMVs on the physiology of human lung cells. My findings reveal that PA14 BMVs significantly impair cell growth and viability while inducing a global metabolic reprogramming in the host cell. Specifically, PA14 BMVs downregulate cholesterol biosynthesis, disrupt TCA cycle activity, and impair mitochondrial respiration by inhibiting complex III of the electron transport chain. The resulting mitochondrial dysfunction then activates AMP-activated protein kinase (AMPK) signaling, leading to the downregulation of global protein synthesis via phosphorylation of the eukaryotic elongation factor 2. Moreover, I identify the P. aeruginosa SuhB protein as a key regulator of PA14 BMV secretion and pathogenicity. Additionally, I show that the redox-active pigment pyocyanin is associated with PA14 BMVs and potentially contributes to their significant impact on host cell physiology.