The urokinase receptor is a major vitronectin-binding protein on endothelial cells.
We have previously demonstrated that vitronectin (VN), a morphoregulatory protein in the vessel wall, is internalized and translocated to the subendothelial matrix by an integrin-independent mechanism (J. Histochem. Cytochem. 41, 1823-1832, 1993). The cell surface component which mediates the initial contact of VN with endothelial cells is defined here. The specific binding of VN to endothelial cells demonstrated the following properties: a threefold increase after phorbol ester treatment; 85% inhibition by pretreatment of cells with phosphatidylinositol-phospholipase C to release glycolipid-anchored surface proteins; a 90% inhibition by urokinase (u-PA) receptor blocking antibody. u-PA increased VN binding to cells due to an eightfold increase in the affinity of VN for the u-PA receptor. Structure-function studies showed that the amino-terminal fragment of u-PA, devoid of any proteolytic activity, mediated this effect. Active plasminogen activator inhibitor-1 (PAI-1), but not inactivated PAI-1, inhibited VN binding to cells and displaced VN that was prebound to endothelial cell monolayers. Similarly, VN binding to purified (immobilized) u-PA receptor, but not to integrin, was enhanced by u-PA and inhibited by PAI-1. Hence, the binding of soluble VN to endothelial cell surfaces is mediated by the u-PA receptor, and the relative concentrations of u-PA and PAI-1 are able to regulate the strength of this interaction. Endothelial cell adhesion to immobilized VN was found to be integrin-mediated without any involvement of the VN-uPA-receptor system. Hence, the interaction of VN with the u-PA receptor may be involved in the regulation of cellular processes necessary for endothelial cell invasion and migration at VN-rich extracellular matrix sites.
Kanse
S M
SM
Haemostasis Research Unit, Kerckhoff-Klinik, Bad Nauheim, Germany.
Kost
C
C
Wilhelm
O G
OG
Andreasen
P A
PA
Preissner
K T
KT
D000918:Antibody Specificity; D001667:Binding, Competitive / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D004730:Endothelium, Vascular / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D006801:Humans; D007457:Iodine Radioisotopes; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D015398:Signal Transduction / Q000502:physiology; D013696:Temperature; D014471:Umbilical Veins / Q000166:cytology; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology; D019096:Vitronectin / Q000276:immunology / Q000378:metabolism*
D007457:Iodine Radioisotopes; C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D019096:Vitronectin; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator