Small Molecule Inhibitors of the BfrB-Bfd Interaction Decrease Pseudomonas aeruginosa Fitness and Potentiate...

Area of Science:

• Bacterial iron homeostasis
• Protein-protein interaction inhibitors
• Drug discovery

Background:

• Bacterioferritin (BfrB) is crucial for bacterial iron storage and homeostasis.
• Iron mobilization from BfrB by ferredoxin (Bfd) regulates cytosolic iron levels in P. aeruginosa.
• Targeting protein-protein interactions offers a novel therapeutic strategy.

Purpose of the Study:

• To develop small molecule inhibitors of the BfrB-Bfd protein-protein interaction.
• To investigate the impact of these inhibitors on P. aeruginosa iron homeostasis and growth.
• To evaluate the potential of these inhibitors in combination with antibiotics.

Main Methods:

• Structure-guided drug design based on fragment screening.
• Synthesis and characterization of 4-substituted isoindoline-1,3-dione analogs.
• In vitro and in vivo assays using P. aeruginosa, including growth inhibition and iron staining.

Main Results:

• Developed isoindoline analogs that selectively bind BfrB at the Bfd binding site.
• Inhibitors caused dose-dependent growth inhibition and pyoverdin hyperproduction in P. aeruginosa.
• Analogs led to iron accumulation in BfrB and depletion in the cytosol, confirmed by native PAGE and Ferene S staining.
• Combination therapy with fluoroquinolones significantly reduced P. aeruginosa survival.

Conclusions:

• Small molecule inhibitors targeting the BfrB-Bfd interaction effectively dysregulate bacterial iron homeostasis.
• These findings demonstrate proof of concept for targeting protein-protein interactions in bacterial iron storage.
• The developed analogs show promise as adjuncts to existing antibiotic therapies.