Thrombin receptor (Protease-activated receptor 1) (PAR1)

Thrombin-induced platelet aggregation refers to the process by which thrombin, a serine protease generated during blood coagulation, activates platelets leading to their aggregation and formation of a hemostatic plug. This process is primarily mediated through the protease‐activated receptors on platelets, especially protease‐activated receptor 1 (PAR1) and, at higher concentrations of thrombin, protease‐activated receptor 4 (PAR4). Upon vascular injury, thrombin cleaves these receptors on the platelet surface; this cleavage exposes a new N-terminal sequence that acts as a tethered ligand to activate the same molecule in an autocrine fashion[3][6][7]. In addition to direct signaling through PARs, thrombin also binds glycoprotein Ibα on platelets, which amplifies activation by accelerating PAR1 signaling and may have additional direct effects[3][7]. The downstream effect is increased intracellular calcium flux and upregulation of integrin αIIbβ3 activity—this integrin mediates cross-linking between platelets via fibrinogen or von Willebrand factor binding, resulting in stable aggregate formation essential for clot stabilization[4]. Thrombin-induced platelet aggregation plays a central role in normal hemostasis but also contributes significantly to pathological arterial thrombosis such as myocardial infarction or stroke. Because of its importance in both physiological clotting and pathological thrombosis, components of this pathway—especially PAR1—are considered key therapeutic targets for antithrombotic drugs such as vorapaxar. However, inhibition carries an increased risk of bleeding complications due to impaired hemostatic function[7]. Note: "Thrombin-induced platelet aggregation" describes a biological process rather than a single molecular target; however, it is most accurately mapped onto "Protease‐activated receptor 1" when considering drug targeting or molecular classification purposes.

Other names

Protease-activated receptor 1PAR1Thrombin receptorF2R (gene symbol for PAR1)Protease-activated receptor 4 (PAR4, related but distinct)

Inhibition of thrombin-induced platelet activation via antagonism of PAR1[7][6]