Developing Inhibitors of the p47phox-p22phox Protein-Protein Interaction by Fragment-Based Drug Discovery.

Nicotinamide adenine dinucleotide phosphate oxidase isoform 2 is an enzyme complex, which generates reactive oxygen species and contributes to oxidative stress. The p47phox-p22phox interaction is critical for the activation of the catalytical NOX2 domain, and p47phox is a potential target for therapeutic intervention. By screening 2500 fragments using fluorescence polarization and a thermal shift assay and validation by surface plasmon resonance, we found eight hits toward the tandem SH3 domain of p47phox (p47phox(SH3A-B)) with K-D values of 400-600 mu M. Structural studies revealed that fragments 1 and 2 bound two separate binding sites in the elongated conformation of p47phox(SH3A-B) and these competed with p22phox for binding to p47phox(SH3A-B). Chemical optimization led to a dimeric compound with the ability to potently inhibit the p47phox(SH3A-B)-p22phox interaction (K-i of 20 mu M). Thereby, we reveal a new way of targeting p47phox and present the first report of drug-like molecules with the ability to bind p47phox and inhibit its interaction with p22phox.