American Society for Biochemistry and Molecular Biology
Journal of Biological Chemistry vol:287 issue:12 pages:9461-9472
The von Willebrand Factor (VWF) A1 - glycoprotein (GP) Ibα interaction is of major importance during thrombosis mainly at sites of high shear stress. Inhibitors of this interaction prevent platelet-dependent thrombus formation in vivo, without major bleeding complications. However, the size and/or protein nature of the inhibitors currently in development limit oral bioavailability and clinical development. We therefore aimed to search for a small molecule protein-protein interaction inhibitor (SMPPII) interfering with the VWF-GPIbα binding. After determination of putative small molecule binding pockets on the surface of VWF-A1 and GPIbα using site finding algorithms and molecular dynamics, high-throughput molecular docking was performed on both binding partners. A selection of compounds showing good in silico docking scores into the predicted pockets was retained for testing their in vitro effect on VWF-GPIbα complex formation, by which we identified a compound that surprisingly stimulated the VWF-GPIbα binding in a ristocetin co-factor ELISA and increased platelet adhesion in whole blood to collagen under arterial shear rate, but that in contrast inhibited ristocetin-induced platelet aggregation. The selected compound is adhering to the predicted binding partner GPIbα as could be confirmed by saturation transfer difference NMR spectroscopy. We thus clearly identified a small molecule that modulates VWF-GPIbα binding, and that will now serve as a starting point for further studies and chemical modifications to fully characterize the interaction and to manipulate the compounds specific activity.