Endothelial cells (EC) form a dynamic interface between blood and the rest of the body. EC surface properties promoting adhesion of reactive plasma proteins and/or circulating cells might be of pivotal importance for the homeostasis of blood and tissues. EC express multiple integrin receptors that promote their attachment to the subendothelial matrix proteins. Among these receptors, αvβ3 is of particular relevance on EC, since it is abundantly expressed and can bind many different matrix and plasma proteins. It is still unknown whether integrin receptors are selectively located to the basal side of EC membrane or may also be exposed on the cell surface in contact with blood. This issue was addressed using different experimental approaches. First, selective surface radioiodination using lactoperoxidase (LPO)-latex beads and immunoprecipitation analysis were performed. We found that cultured EC, similarly to human skin fibroblasts (HSF), expose αvβ3 on both their apical (free) and basal (substaratum-attached) surfaces. This held also for other integrins such as α2β1, α3β1, α5β1, and α6β1. Immunoprecipitation data were verified by morphological techniques. Immunofluorescence and immunogold-staining of EC with αvβ3, as well as with β1 subfamily antibodies, showed a diffuse and granular distrubution of these integrins on EC surface. αvβ3 and β1 integrins were also detected on the apical membrane of EC at higher magnification by scanning electron mictoscopy (SEM). Finally, data obtained on cultured EC were confirmed in vivo on immunogold-labeled utrathin cryosections of human vessels by transmission electron microscopy (TEM). Data indicate, that in addition to their role in promoting EC attachment to extracellular matrix proteins, integrin receptors of EC can be exposed to blood-stream and eventually be available for binding of plasma proteins and circulating cells.
|Number of pages||10|
|Publication status||Published - Jul 15 1992|
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