Vessel wall-dependent metabolic pathways of the adhesive proteins, von-Willebrand-factor and vitronectin

The integrity of the vessel wall under quiescent conditions as well as its appropriate responsiveness under conditions of stimulation, inflammation or vascular injury is controlled by a number of adhesive interactions involving distinct cellular receptor systems and various multifunctional adhesive ligands. While a number of these extracellular matrix components of the vessel wall are endogenously produced, secreted and deposited, exogenous adhesion proteins may become translocated from the intra- to the extravascular space by virtue of endothelial cell-specific transport systems. Two prominent examples for each metabolic pathway are discussed. Endothelial cell-specific biosynthesis and secretion as well as deposition of multimeric von-Willebrand-factor within intracellular granules (Weibel-Palade bodies) relates to the first possibility of processing, whereas binding of reactive forms of circulating vitronectin to diverse cellular receptors with subsequent extravasation and deposition into the extracellular matrix appears to be characteristic for the second case. In this review the known features of the metabolic routes of both adhesion proteins are discussed and set in perspective to their functional properties. Their localized mode of action in the vessel wall appears to be crucial for balanced haemostasis and immune systems, two major defence mechanisms of the organism.