Interaction of fibronectin with cultured human endothelial cells: characterization of the specific receptor

Article Abstract:

Fibronectin (FN) is a normal connective tissue protein (filament) which binds to the cells that line blood vessels, endothelial cells. This study examines these endothelial cells for specific FN binding sites or receptors. FN was labeled with radioactive iodine to detect its reaction to endothelial cells placed in suspension tissue culture. The rate of reaction and binding could be affected by temperature, but the rate of binding was unaffected by the addition of other proteins to the incubation medium. This showed that the binding site on the endothelial cells was specific for the FN molecule, because the addition of other proteins did not compete with FN for the binding site. When an antiserum to FN receptors found in human placenta was introduced into the culture of endothelial cells, the rate of binding was slowed down by 89 per cent. When manganese was added, the rate of binding significantly increased. This demonstrates the presence of specific endothelial binding sites for FN and the apparent identity of these sites with those found in human placenta.

Analysis, Fibronectins, Extracellular matrix, Cell surface antigens

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Interaction of platelet factor four with cultured vascular endothelial cells

Article Abstract:

Platelets, the small cellular fragments which are critically important in the clotting of blood, are able to secrete a small protein, platelet factor four (PF-4). PF-4 is able to bind with the anticoagulant heparin and related molecules (sulfated glycoaminoglycans). An experiment was performed in which PF-4 molecules were labeled with radioactive iodine so that they could be tracked when placed in cultures of epithelial cells from cows. The binding between PF-4 and epithelial cells was affected by temperature and reached a plateau level of binding within 20 minutes of application. After incubation at body temperature, the PF-4 molecule was internalized into the cells through low-affinity absorptive endocytosis. After 18 hours in culture, the amount of PF-4 was reduced by 50 percent, as it was broken down into amino acids and other products. This study implies that such proteins can have an important effect on the regulation of endothelial structure and on the physiologic mechanism of cellular association.

Research, Cytology, Tissue culture

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Biogenesis of the vitronectin receptor in human endothelial cell: evidence that the vitronectin receptor and GPIIb-IIIa are synthesized by a common mechanism

Article Abstract:

The surfaces of human endothelial cells, which line the blood vessels, and human platelets (cell fragments involved in the clotting mechanism) both express a similar type of glycoprotein (a sugar-protein molecule) which acts as a biochemical receptor. Both of these cell surface receptors are able to bind with different proteins in the blood, which can then be converted into fibrils which are associated with the mechanical support of the epithelial cell and with the formation of clots. Both receptors belong to the cytoadhesin family. The glycoprotein receptor of the endothelial cell reacts to associate with vitronectin, and perhaps with both fibrinogen and the von Willebrand blood coagulating factor. The platelet receptor is called the GPIIb-IIIa (GlycoProtein) complex; it acts to bind with fibrinogen, fibronectin and von Willebrand factor. The data suggest that both of these members of the cytoadhesin group are controlled by similar genetic mechanisms even though they are produced in two different cells.

Blood coagulation factors, Cell membranes, Plasma membranes, Blood platelets, Blood clotting, Blood coagulation

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