Effects of Mycoplasma pneumoniae CARDS Toxin on mitochondrial homeostasis

Abstract

Abstract Mycoplasma pneumoniae is an atypical bacterial pathogen known to cause mild respiratory infections and pneumonia. M. pneumoniae produces Community-Acquired Respiratory Distress Syndrome toxin (CARDS toxin), a virulence factor that plays a primary role in pathogenesis. CARDS toxin is known to have dramatic vacuolating and inflammatory properties, however these properties have not been fully characterized. Recent evidence from our lab has supported that the toxin localizes on the mitochondria, affecting homeostasis and triggering inflammation. Our current study is focused on characterizing the effects of CARDS toxin on mitochondrial stress and production of mitochondrial reactive oxygen species (ROS). A549 lung epithelial cells and IMR-90 lung fibroblasts were treated with recombinant CARDS toxin exogenously, and mitochondrial ROS was measured. Additionally, we sought to determine whether ADP-ribosylation or vacuolization were required for CARDS toxin-induced mitochondrial stress by expressing CARDS toxin truncations on a mammalian expression plasmid. Endogenously expressed CARDS toxin truncations were fused to either EGFP or mCherry2. CARDS toxin was detected by western blot and IFA was used to track CARDS toxin localization in the cell. Our findings support our hypothesis that CARDS toxin disrupts mitochondrial homeostasis and triggers mitochondrial ROS production. Our results provide valuable insight into the effects of CARDS toxin on mitochondrial function, which will help us better characterize the role of CARDS toxin during M. pneumoniae pathogenesis. Supported by NIH T34GM008073