Characterization of the Proteomic Response of A549 Cells Following Sequential Exposure to Aspergillus fumigatus and Pseudomonas aeruginosa

Aspergillus fumigatus and Pseudomonas aeruginosa are the most prevalent fungal and bacterial pathogens associated with cystic-fibrosis-related
infections, respectively. P. aeruginosa eventually predominates as the primary pathogen, though it is unknown
why this is the case. Label-free quantitative proteomics was employed
to investigate the cellular response of the alveolar epithelial cell
line, A549, to coexposure of A. fumigatus and P. aeruginosa. These studies
revealed a significant increase in the rate of P. aeruginosa proliferation where A. fumigatus was
present. Shotgun proteomics performed on A549 cells exposed to either A. fumigatus or P. aeruginosa or to A. fumigatus and P. aeruginosa sequentially revealed distinct changes
to the host cell proteome in response to either or both pathogens.
While key signatures of infection were retained among all pathogen-exposed
groups, including changes in mitochondrial activity and energy output,
the relative abundance of proteins associated with endocytosis, phagosomes,
and lysosomes was decreased in sequentially exposed cells compared
to cells exposed to either pathogen. Our findings indicate that A. fumigatus renders A549 cells unable to internalize
bacteria, thus providing an environment in which P.
aeruginosa can proliferate. This research provides
novel insights into the whole-cell proteomic response of A549 cells
to A. fumigatus and P. aeruginosa and highlights distinct differences
in the proteome following sequential exposure to both pathogens, which
may explain why P. aeruginosa can predominate.