Structural and functional aspects of intercellular junctions in vascular endothelium

Cell-to-cell-junctions of endothelial cells are specialized and differentia ted areas of the plasma membrane. The main functions include the separation of the intravascular and extravascular compartments, the mechanical connec tion of the cells, and the maintenance of the cell polarity. Although a wide heterogeneity of endothelial cell-to-cell junctions exists in situ, they should be considered in general as adherens type junctions in which gap and tight junctions are morphologically inserted. Under certain pathological conditions, such as wound healing, angiogenesis and many types of inflammation, the interendothelial junctions have to be d issociated and reorganized in which proteins of the junctions are crucially involved. These important mechanisms predict a sophisticated regulation of junctional proteins. The present paper describes the organization and func tional aspects of the occludin/ZO-1 complex typically found in tight juncti ons, the cadherin/ catenin complex of the adherens junctions and the connec tion of these protein complexes to the dense peripheral band via actin fila ments. In addition, special attention has been drawn on the function of jun ction-associated proteins with respect to their role under fluid shear stre ss and interendothelial gap formation during inflammation.