Fragment-Based Discovery of a Regulatory Site in Thioredoxin Glutathione Reductase Acting as “Doorstop” for NADPH Entry

• DOI: 10.1021/acschembio.8b00349
• Publication Date: 2018-05-25T22:53:20Z
• Authors: Ilaria Silvestri; Haining Lyu; Francesca Fata; Giovanna Boumis; Adriana E. Miele; Matteo Ardini; Rodolfo Ippoliti; Andrea Bellelli; Ajit Jadhav; Wendy A. Lea; Anton Simeonov; Qing Cheng; Elias S. J. Arnér; Gregory R. J. Tha...; Pavel A. Petukhov; David L. Williams; Francesco Angelucci
• Keywords: Anthelmintics; Models, Molecular; 0301 basic medicine; Conformation, Inhibition, Inhibitors, Peptides and proteins, Redox reactions; Schistosoma mansoni; Crystallography, X-Ray; Schistosomiasis mansoni; 3. Good health; Mice; 03 medical and health sciences; biochemistry; molecular medicine; Multienzyme Complexes; Drug Discovery; Animals; Humans; NADH, NADPH Oxidoreductases; [SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM]; Enzyme Inhibitors; NADP

Members of the FAD/NAD-linked reductase family are recognized as crucial targets in drug development for cancers, inflammatory disorders, and infectious diseases. However, individual FAD/NAD reductases are difficult to inhibit in a selective manner with off-target inhibition reducing usefulness of identified compounds. Thioredoxin glutathione reductase (TGR), a high molecular weight thioredoxin reductase-like enzyme, has emerged as a promising drug target for the treatment of schistosomiasis, a parasitosis afflicting more than 200 million people. Taking advantage of small molecules selected from a high-throughput screen and using X-ray crystallography, functional assays, and docking studies, we identify a critical secondary site of the enzyme. Compounds binding at this site interfere with well-known and conserved conformational changes associated with NADPH reduction, acting as a doorstop for cofactor entry. They selectively inhibit TGR from Schistosoma mansoni and are active against parasites in culture. Since many members of the FAD/NAD-linked reductase family have similar catalytic mechanisms, the unique mechanism of inhibition identified in this study for TGR broadly opens new routes to selectively inhibit homologous enzymes of central importance in numerous diseases.