ALBERT

Description: 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, alpha v beta 3 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 alpha v beta 3 on both their apical (free) and basal (substratum-attached) surfaces. This held also for other integrins such as alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, and alpha 6 beta 1. Immunoprecipitation data were verified by morphological techniques. Immunofluorescence and immunogold-staining of EC with alpha v beta 3, as well as with beta 1 subfamily antibodies, showed a diffuse and granular distribution of these integrins on EC surface. alpha v beta 3 and beta 1 integrins were also detected on the apical membrane of EC at higher magnification by scanning electron microscopy (SEM). Finally, data obtained on cultured EC were confirmed in vivo on immunogold-labeled ultrathin 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.

Description: The microanatomy of the dot-shaped, close-contact sites called podosomes and the mechanism of their formation have been investigated in vitro in the malignant lymphocytes of B chronic lymphocytic leukemia (B-CLL). In this paper the authors demonstrate that in B-CLL podosomes: (1) vinculin, talin, and beta 2 integrin (CD18) rings surround an F- actin core; (2) the beta 1 integrin is localized within the F-actin core; (3) the beta 3 integrin is not present. This distribution and organization of adhesion-related molecules appears to be unique to B- CLL lymphocytes, since it has not been observed in normal B cells. B- CLL adhesion and podosome formation are inhibited by the synthetic peptide GRGDSP that contains the Arg-Gly-Asp (RGD) sequence.

Description: The microanatomy of the dot-shaped, close-contact sites called podosomes and the mechanism of their formation have been investigated in vitro in the malignant lymphocytes of B chronic lymphocytic leukemia (B-CLL). In this paper the authors demonstrate that in B-CLL podosomes: (1) vinculin, talin, and beta 2 integrin (CD18) rings surround an F- actin core; (2) the beta 1 integrin is localized within the F-actin core; (3) the beta 3 integrin is not present. This distribution and organization of adhesion-related molecules appears to be unique to B- CLL lymphocytes, since it has not been observed in normal B cells. B- CLL adhesion and podosome formation are inhibited by the synthetic peptide GRGDSP that contains the Arg-Gly-Asp (RGD) sequence.

Description: 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, alpha v beta 3 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 alpha v beta 3 on both their apical (free) and basal (substratum-attached) surfaces. This held also for other integrins such as alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, and alpha 6 beta 1. Immunoprecipitation data were verified by morphological techniques. Immunofluorescence and immunogold-staining of EC with alpha v beta 3, as well as with beta 1 subfamily antibodies, showed a diffuse and granular distribution of these integrins on EC surface. alpha v beta 3 and beta 1 integrins were also detected on the apical membrane of EC at higher magnification by scanning electron microscopy (SEM). Finally, data obtained on cultured EC were confirmed in vivo on immunogold-labeled ultrathin 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.