Phosphatidylserine-exposed membrane (PS-membrane)

Negatively charged phospholipid membranes, specifically those characterized by the externalization of phosphatidylserine (PS), act as essential catalytic surfaces for the coagulation cascade on activated platelets. In quiescent platelets, PS is restricted to the inner leaflet of the plasma membrane by the action of flippases, but platelet activation triggers a loss of membrane asymmetry via scramblases (Heemskerk et al., 2002). This externalization exposes a negatively charged surface that facilitates the calcium-dependent assembly of the tenase and prothrombinase complexes (Zwaal & Schroit, 1997). These complexes are required for the rapid generation of thrombin, which is the central enzyme in blood clot formation. Because PS exposure is a hallmark of activated platelets and procoagulant microparticles, it serves as a specific target for both diagnostic imaging and therapeutic intervention in thrombotic disorders (Schutters & Reutelingsperger, 2010). Therapeutic agents like Annexin A5 bind to exposed PS with high affinity, sterically hindering the binding of coagulation factors and thereby inhibiting thrombosis (Kenis & Reutelingsperger, 2009). This targeting strategy is particularly attractive because it focuses on the site of active platelet involvement, potentially minimizing systemic bleeding risks associated with conventional anticoagulants. Additionally, PS-targeting agents are being explored for their ability to deliver imaging isotopes or thrombolytic drugs directly to the site of an active thrombus.

Other names

Procoagulant membraneActivated platelet surfaceNegatively charged phospholipid surfacePhosphatidylserine-rich membranePS-exposed membrane

Binding to externalized phosphatidylserine on the surface of activated platelets to competitively inhibit the assembly of procoagulant complexes (tenase and prothrombinase), thereby reducing thrombin generation and thrombus growth.