Phosphatidylserine-exposed platelet membrane (PS-exposed platelet membrane)

The phosphatidylserine-exposed platelet membrane is a specialized procoagulant surface that forms on the exterior of activated platelets during the process of blood coagulation (Source: PubMed 12814644). Under physiological conditions, the phospholipid phosphatidylserine (PS) is actively sequestered in the inner leaflet of the platelet plasma membrane by flippases; however, upon strong activation by agonists like thrombin and collagen, a rapid increase in cytosolic calcium activates the scramblase TMEM16F, leading to the externalization of PS (Source: PNAS 10.1073/pnas.1218343110). This negatively charged surface serves as an essential scaffold for the assembly of coagulation factor complexes, including the tenase and prothrombinase complexes, which catalyze the explosive generation of thrombin required for fibrin formation and clot stability (Source: NIH PMC6178738). Pathologically, the presence of PS-exposed membranes is a key driver of arterial and venous thrombosis and is associated with the prothrombotic state in cancer and inflammatory diseases (Source: ResearchGate 1.2.4). Conversely, defects in PS exposure result in Scott syndrome, a rare bleeding disorder characterized by impaired thrombin generation (Source: NIH 1.2.3). Therapeutic and diagnostic strategies focus on using PS-binding proteins, such as Annexin V, for the molecular imaging of active thrombi or as templates for site-specific anticoagulants that block the procoagulant surface (Source: Science.gov 1.4.2). Drugs like Diannexin and Bavituximab target this membrane to modulate coagulation or immune responses, while small molecules like Niclosamide are being investigated for their ability to inhibit the scrambling process itself (Source: cam.ac.uk 1.1.1).

Other names

Activated platelet membraneProcoagulant platelet membranePS-positive platelet membraneAnionic phospholipid-exposed platelet membraneCOAT platelet membraneActivated platelets / phosphatidylserine-exposed platelet membrane

Drugs targeting the phosphatidylserine-exposed platelet membrane primarily function by binding to externalized phosphatidylserine, which sterically inhibits the assembly of the tenase and prothrombinase complexes, thereby reducing thrombin generation and clot stabilization. Additionally, some agents target the enzymatic processes responsible for phosphatidylserine exposure, such as inhibiting the scramblase TMEM16F or modulating flippase activity, while others use the exposed membrane as a docking site for the targeted delivery of imaging agents or thrombolytic therapy.