The Structural Analogy of MASP-2 with Thrombin and MASP-1 Reveals Strong Binding with PAR4

INTRODUCTION: The historical discovery that thrombin activates Protease-Activated Receptor 4 (PAR4) has paved the way for several novel findings. Besides thrombin, the complement lectin pathway protease Mannose-Binding Lectin-Associated Serine Protease-1 (MASP-1) also binds to PAR4, albeit with lower affinity. Similar to thrombin, MASP-1 activates Ca². signaling pathways in endothelial cells. MASP-2, a homolog of MASP-1, plays an important role in complement activation; however, its direct interaction with PAR4 has not yet been elucidated. In this study, we performed structural investigations of thrombin, MASP-1, and MASP-2 to evaluate their binding affinities toward the PAR4 peptide. METHODS: We employed in silico docking, binding affinity calculations, molecular dynamics simulations, and mutagenesis studies to test our hypothesis. RESULTS: For the first time, we demonstrate that, like thrombin and MASP-1, MASP-2 binds to PAR4 with appreciable affinity and could serve as a potential agonist of the PAR4 receptor and its associated inflammatory signaling pathways. DISCUSSION: The high sequence similarity of MASP-2 with MASP-1 and thrombin is an important factor in attaining comparable binding with the PAR4 peptide. CONCLUSION: Our findings may pave the way for future investigations into the signaling mechanisms and therapeutic potential of PAR4-mediated inflammatory diseases.