[Biosynthesis in the vascular endothelial cells, molecular structure and function of von Willebrand factor].

von Willebrand factor (vWf) is synthesized by vascular endothelial cells and megakaryocytes, and is present in plasma, platelets and subendothelium as a large multimeric glycoprotein that has a dual role in hemostasis. vWf mediates the adhesion of platelets at the site of vascular injury by linking to specific platelet membrane receptors (glycoprotein [GP] Ib-IX complex) and to constituents of subendothelial connective tissue. vWf also functions as a carrier protein for factor VIII; this interaction is necessary for normal factor VIII survival in the circulating plasma. Each vWf subunit has binding sites for collagen, heparin, GP Ib, GPIIb/IIIa and factor VIII. Deficiency of vWf results in defective platelet adhesion and a secondary deficiency of factor VIII, both causing abnormal bleeding. In addition, vWf plays an important role in thrombogenesis and the development of atherosclerosis.