Biosynthesis, processing and secretion of von Willebrand factor: biological implications

von Willebrand factor is a multimeric plasma glycoprotein that is required for normal haemostasis. von Willebrand factor is synthesized by endothelial cells and megakaryocytes, and originates from its precursor pro-von Willeb rand factor. The endoproteolytic processing of pro-von Willebrand factor re sults in mature von Willebrand factor and von Willebrand factor propeptide (also known as von Willebrand Ag II). In endothelial cells, the propeptide controls the polymerization and subsequent targeting of von Willebrand fact or to the storage vesicles, the so-called Weibel-Palade bodies. Upon stimul ation of the endothelial cells, the Weibel-Palade bod ies are translocated to the plasma membrane of the cell, and mature von Willebrand factor and it s propeptide are co-secreted. After release, these polypeptides have diverg ent fates and serve different biological functions. Mature von Willebrand f actor both controls platelet adhesion and aggregation at sites of vascular injury and acts as a chaperone protein for coagulation factor VIII. The von Willebrand factor propeptide may serve a role in modulating inflammatory p rocesses. This still growing body of information indicates that the biologi cal function of the von Willebrand factor gene product is more diverse than was previously thought.