Quinoline Compounds Targeting the c-Ring of ATP Synthase Inhibit Drug-Resistant Pseudomonas aeruginosa.

Pseudomonas aeruginosa (PA) is a Gram-negative, biofilm-forming bacterium and an opportunistic pathogen. The growing drug resistance of PA is a serious threat that necessitates the discovery of novel antibiotics, ideally with previously underexplored mechanisms of action. Due to their central role in cell metabolism, bacterial bioenergetic processes are of increasing interest as drug targets, especially with the success of the ATP synthase inhibitor bedaquiline to treat drug-resistant tuberculosis. Like Mycobacterium tuberculosis, PA requires F1Fo ATP synthase for growth, even under anaerobic conditions, making the PA ATP synthase an ideal drug target for the treatment of drug-resistant infection. In previous work, we conducted an initial screen for quinoline compounds that inhibit ATP synthesis activity in PA. In the present study, we report additional quinoline derivatives, including one with increased potency against PA ATP synthase in vitro and antibacterial activity against drug-resistant PA. Moreover, by expressing the PA ATP synthase in Escherichia coli, we show that mutations in the H+ binding site on the membrane-embedded rotor ring alter inhibition by the reported quinoline compounds. Identification of a potent inhibitor and its probable binding site on ATP synthase enables further development of promising quinoline derivatives into a viable treatment for drug-resistant PA infection.

Synthesis and Evaluation of Pseudomonas aeruginosa ATP Synthase Inhibitors.

New antibiotics with unique biological targets are desperately needed to combat the growing number of resistant bacterial pathogens. ATP synthase, a critical protein found in all life, has recently become a target of interest for antibiotic development due to the success of the anti-tuberculosis drug bedaquiline, and while many groups have worked on developing drugs to target bacterial ATP synthase, few have been successful at inhibiting Pseudomonas aeruginosa (PA) ATP synthase specifically. PA is one of the leading causes of resistant nosocomial infections across the world and is extremely challenging to treat due to its various antibiotic resistance mechanisms for most commonly used antibiotics. Herein, we detail the synthesis and evaluation of a series of C1/C2 quinoline analogues for their ability to inhibit PA ATP synthase and act as antibiotics against wild-type PA. From this survey, we found six compounds capable of inhibiting PA ATP synthase in vitro showing that bulky/hydrophobic C1/C2 substitutions are preferred. The strongest inhibitor showed an IC50 of 10 µg/mL and decreased activity of PA ATP synthase to 24% relative to the control. While none of the compounds were able to inhibit wild-type PA in cell culture, two showed improved inhibition of PA growth when permeability of the outer membrane was increased or efflux was knocked out, thus demonstrating that these compounds could be further developed into efficacious antibiotics.