Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Physical Sciences, Biochemistry & Molecular Biology, Chemistry, Multidisciplinary, Chemistry, plasminogen activator inhibitor 1, cardiovascular disease, fibrinolysis, thrombolysis, PAI-1 inhibitor, X-ray crystallography, PLASMINOGEN-ACTIVATOR INHIBITOR-1, CRYSTAL-STRUCTURE, SERPIN, PROTEIN, IDENTIFICATION, INACTIVATION, OPTIMIZATION, TIPLAXTININ, ANTAGONIST, TRANSITION, Binding Sites, Catalytic Domain, Crystallization, Crystallography, X-Ray, Dose-Response Relationship, Drug, Humans, Models, Molecular, Plasminogen Activator Inhibitor 1, Protein Conformation, Structure-Activity Relationship, G072915N#53213916, 0399 Other Chemical Sciences, 0604 Genetics, 0699 Other Biological Sciences, Chemical Physics, 3101 Biochemistry and cell biology, 3107 Microbiology, 3404 Medicinal and biomolecular chemistry

Abstract:

Plasminogen activator inhibitor-1 (PAI-1), a key regulator of the fibrinolytic system, is the main physiological inhibitor of plasminogen activators. By interacting with matrix components, including vitronectin (Vn), PAI-1 plays a regulatory role in tissue remodeling, cell migration, and intracellular signaling. Emerging evidence points to a role for PAI-1 in various pathological conditions, including cardiovascular diseases, cancer, and fibrosis. Targeting PAI-1 is therefore a promising therapeutic strategy in PAI-1-related pathologies. A class of small molecule inhibitors including TM5441 and TM5484, designed to bind the cleft in the central β-sheet A of PAI-1, showed to be potent PAI-1 inhibitors in vivo. However, their binding site has not yet been confirmed. Here, we report two X-ray crystallographic structures of PAI-1 in complex with TM5484. The structures revealed a binding site at the flexible joint region, which is distinct from the presumed binding site. Based on the structural analysis and biochemical data we propose a mechanism for the observed dose-dependent two-step mechanism of PAI-1 inhibition. By binding to the flexible joint region in PAI-1, TM5484 might restrict the structural flexibility of this region, thereby inducing a substrate form of PAI-1 followed by a conversion to an inert form.