Phosphatidylserine-exposed membrane of activated platelets (PS-exposed membrane) (PS-exposed membrane)

Phosphatidylserine-rich phospholipid membranes on activated platelets serve as a critical catalytic platform for the assembly of blood coagulation factor complexes (Heemskerk et al., 2013). In resting platelets, phosphatidylserine (PS) is actively sequestered in the inner leaflet of the plasma membrane by flippase enzymes. Upon activation by agonists such as thrombin or collagen, a process known as "flip-flop" occurs via scramblase activity, exposing PS on the outer surface (Lentz, 2003). This negatively charged surface facilitates the calcium-dependent binding of vitamin K-dependent coagulation factors, including Factors IX, X, and prothrombin. This assembly is essential for the rapid generation of thrombin and subsequent fibrin clot formation, a process often referred to as the cell-based model of coagulation. Because PS exposure is a hallmark of both activated platelets and apoptotic cells, it represents a unique therapeutic target for anticoagulants and imaging agents (Schutters & Reutelingsperger, 2010). Drugs like Diannexin work by masking these exposed PS sites to prevent the formation of the prothrombinase complex, thereby reducing the risk of thrombosis (Rand et al., 2004). Additionally, PS-targeting strategies are explored in oncology to disrupt the procoagulant environment of the tumor vasculature and enhance immune responses.

Other names

Procoagulant phospholipid surfacePhosphatidylserine-rich membraneActivated platelet surfacePS-exposed leafletAnionic phospholipid surface

Binding to anionic phosphatidylserine headgroups to sterically hinder the assembly of tenase and prothrombinase complexes, thereby inhibiting thrombin generation (Rand et al., 2004; Lentz, 2003).