AnxA5

Annexin A5 (AnxA5, Annexin V) is a Ca²⁺-dependent phosphatidylserine (PS)-binding protein that functions at the interface of membrane biology, apoptosis, coagulation, and inflammation^[1][2]. Through its high-affinity interaction with exposed PS, AnxA5 regulates cellular responses associated with apoptotic cell clearance and membrane remodeling, while also modulating procoagulant phospholipid surfaces^[1][3]. Mechanistically, extracellular AnxA5 forms organized assemblies on PS-expressing membranes and participates in biological processes including apoptosis, phagocytosis, blood coagulation, and microparticle formation^[3][4]. In disease-relevant settings, AnxA5 suppresses endothelial inflammatory responses induced by activated platelets and microvesicles through PS-dependent mechanisms, supporting its role in vascular inflammation and sepsis-related pathology^[5]. AnxA5 has also emerged as a widely used biomarker and molecular probe for the detection of apoptosis because externalization of PS is an early hallmark of apoptotic cells and can be specifically recognized by annexin-based assays^[6][7]. Compared with other annexin family members, AnxA5 is distinguished by its extensive experimental application as a PS-targeting molecule for apoptosis detection, molecular imaging, and investigation of PS-mediated signaling pathways^[2][6][8]. Structural studies further demonstrate that efficient PS binding and anticoagulant activity depend on intact AnxA5 membrane-interaction domains, highlighting the importance of PS recognition for its biological and research functions^[9]. Recombinant human AnxA5 is therefore broadly employed as an experimental reagent for studying apoptosis, inflammation, coagulation, and membrane-associated pathophysiology^[5][10].