title: The endothelial cell tissue plasminogen activator receptor. Specific interaction with plasminogen.
abstract: Human endothelial cells (EC) assemble plasmin-generating proteins on their surface. We have previously identified an EC membrane protein (Mr approximately 40,000) which specifically binds tissue plasminogen activator (t-PA) but not urokinase (Hajjar, K.A., and Hamel, N. M. (1990) J. Biol. Chem. 265, 2908-2916). In the present study, t-PA receptor protein (t-PA-R) was purified to apparent homogeneity from a detergent extract of human placental tissue by diisopropyl fluorophosphate-t-PA affinity chromatography and preparative gel electrophoresis. In a solid phase binding assay wells coated with t-PA-R bound both 125I-t-PA and 125I-Lys-plasminogen (PLG), but not 125I-urokinase in a specific, reversible, and noncompetitive fashion. Binding of 125I-Lys-PLG, but not 125I-t-PA, to t-PA-R was 80% inhibited by a 20-100-fold molar excess of the PLG-like lipoprotein(a), or by the lysine analog, epsilon-aminocaproic acid (50 mM). A polyclonal anti-t-PA-R antibody inhibited 66 and 79% of the specific 125I-t-PA and 125I-Lys-PLG binding, respectively, to EC monolayers. Biosynthetically labeled 40-kDa protein coprecipitated with t-PA- or Lys-PLG-Sepharose beads, but not with unconjugated Sepharose. In a functional assay, t-PA associated with immobilized t-PA-R generated 6.4 times more plasmin than an equivalent amount of t-PA in the fluid phase. These results suggest that t-PA-R can bind both t-PA and Lys-PLG in a manner that mimics the EC surface. This protein may play a role in modulating plasmin generation on cell surfaces.
authors.affiliation: National Institutes of Health Specialized Center of Research in Thrombosis, Department of Pediatrics, Cornell University Medical College, New York, New York 10021.
authors.forename: K A
authors.initials: KA
authors.lastname: Hajjar
mesh_terms: D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006801:Humans; D007700:Kinetics; D017270:Lipoprotein(a); D008074:Lipoproteins / Q000494:pharmacology; D008970:Molecular Weight; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000378:metabolism*; D014471:Umbilical Veins
chemical_list: D017270:Lipoprotein(a); D008074:Lipoproteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C067262:PLAT protein, human; D010959:Tissue Plasminogen Activator