title: Urokinase binding and receptor identification in cultured endothelial cells.
abstract: Recombinant human single-chain urokinase (rscu-PA), two-chain urokinase (tcu-PA), and diisopropyl-fluorophosphate-treated tcu-PA (DFP-tcu-PA) bound to cultured human and porcine endothelial cells in a rapid, saturable, dose-dependent and reversible manner. Analysis of specific binding results in cultured human umbilical vein endothelial cells (HUVECs) gave the following estimated values for Kd and Bmax: 0.57 +/- 0.08 nM (mean +/- S.E.) and 188,000 +/- 18,000 sites/cell for 125I-labeled rscu-PA; 0.54 +/- 0.10 nM and 132,000 +/- 23,900 sites/cells for 125I-labeled tcu-PA; 0.89 +/- 0.14 nM and 143,000 +/- 30,300 sites/cell for 125I-labeled DFP-tcu-PA, respectively. Values for Kd were similar for primary and subcultured (six passages) HUVECs, but Bmax values were lower in subcultured HUVECs. Similar Kd values were found in cultured porcine endothelial cells; however, Bmax values varied depending on the endothelial cell type. All 125I-labeled urokinase forms yielded similar cross-linked approximately 110-kDa ligand-receptor complexes with cultured HUVECs, and 125I-labeled DFP-tcu-PA bound to a single major approximately 55-kDa protein in whole-cell lysates (ligand blotting/autoradiography), suggesting the presence of a single major approximately 55-kDa urokinase receptor in cultured HUVECs. The approximately 55-kDa urokinase receptor, isolated from several separate batches of cultured HUVECs (3-5 micrograms of protein, approximately 1 x 10(9) cells), by ligand affinity chromatography, exhibited the following properties: retained biologic activity as evidenced by its ability to bind 125I-labeled rscu-PA by ligand blotting/autoradiography and formation of a cross-linked 125I-labeled approximately 110-kDa rscu-PA-receptor complex; single-chain approximately 55-kDa protein, following reduction; complete conversion to and formation of a single major deglycosylated approximately 35-kDa protein, following treatment with N-glycanase.
authors.affiliation: Department of Medicine, University of Alabama, Birmingham 35294.
authors.forename: R C
authors.initials: RC
authors.lastname: Haddock
authors.forename: M L
authors.initials: ML
authors.lastname: Spell
authors.forename: C D
authors.initials: CD
authors.lastname: Baker
authors.forename: J R
authors.initials: JR
authors.lastname: Grammer
authors.forename: J M
authors.initials: JM
authors.lastname: Parks
authors.forename: M
authors.initials: M
authors.lastname: Speidel
authors.forename: F M
authors.initials: FM
authors.lastname: Booyse
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D007531:Isoflurophate / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular; D011651:Pulmonary Artery; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000378:metabolism; D013552:Swine; D014471:Umbilical Veins; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; D007531:Isoflurophate; D014568:Urokinase-Type Plasminogen Activator