Structural Insight into the Two-Step Mechanism of PAI-1 Inhibition by Small Molecule TM5484.

Machteld Sillen, Toshio Miyata, Douglas E Vaughan, Sergei V Strelkov, Paul J Declerck

International journal of molecular sciences 2021 Feb 02

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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.

Citation

Machteld Sillen, Toshio Miyata, Douglas E Vaughan, Sergei V Strelkov, Paul J Declerck. Structural Insight into the Two-Step Mechanism of PAI-1 Inhibition by Small Molecule TM5484. International journal of molecular sciences. 2021 Feb 02;22(3)