ABSTRACT
Endothelial cells are specialized epithelial cells that cover all blood vessels of the cardiovascular system in the body (Simionescu and Simionescu 1988). The vascular network is responsible for the transport of blood from the heart to the peripheral tissues, assuring rapid exchange of nutrients and waste products. The study of macromolecule traffi cking in endothelial cells and the transmigration of cellular elements and pathogenic microorganisms clearly demonstrate that there are complex temporal and structural interactions between the intracellular cytoskeleton and associated components and the membrane proteins, governed by controlled energy production and involvement of different small protein kinases that mediate various signaling pathways. The transcellular transport of blood circulating macromolecules, cells or pathogens is severely restricted and
Institute of Cellular Biology and Pathology Nicolae Simionescu, Bucharest, Romania. Email: felicia.antohe@icbp.ro
requires specifi c processes and highly regulated pathways (Simionescu et al. 2002). To maintain the permeability and the non-thrombogenic surface of the endothelium, the integrity of the monolayer is crucial in order to prevent vascular endothelial cell dysfunctions. Thus, the proper structure and function of the endothelial cytoskeleton governs the complex interactions between the protein complexes during cell motility, cell-cell and cell-substratum adhesion, cell signaling and wound repair (Lee and Gotlieb 2003). The endothelial cell membranes consist of heterogeneous but regulated domains formed by proteins and lipids that form specialized membrane structures (lipid rafts, coated pits and vesicles, plasmalemmal pits and vesicles or caveolae and channels) in which specifi c receptors are located (Simionescu and Simionescu 1991). In addition, the endothelial cells are endowed with apparently less organized cytoskeleton, containing as major components the actin, myosin II, tropomyosin, α-actinin and actin-binding proteins, such as fodrin, gelsolin, girdin, protein 4.1, fi lamin, vinculin, talin, vimentin and many others (Lee Tsu-Yee and Gotlieb 2003). The cytoskeleton in endothelial cells is a highly dynamic structure, and its role in establishing the protein composition of membrane microdomains to activate or inhibit various membrane functions in response to both internal and external stimulations has come under intensive investigations (Chichili and Rodgers 2009, Manneville et al. 2003, Waschke et al. 2005).
