title: Surface-retained tPA is essential for effective fibrinolysis on vascular endothelial cells.
abstract: In a previous study, we demonstrated unique secretory dynamics of tissue plasminogen activator (tPA) in which tPA was retained on the cell surface in a heavy chain-dependent manner after exocytosis from secretory granules in vascular endothelial cells. Here, we examined how retained tPA expresses its enzymatic activity. Retained tPA effectively increased the lysine binding site-dependent binding of plasminogen on the cell surface and pericellular area; this was abolished by inhibition of enzymatic activity of either tPA or plasmin, which suggests that de novo generation of carboxyl-terminal lysine as a consequence of degradation of surface/pericellular proteins by plasmin is essential. Retained tPA initiated zonal clot lysis of a fibrin network that had been formed on vascular endothelial cells, which was preceded by the binding of plasminogen to the lysis front. Our results provide evidence that secreted and retained tPA is essential for maintaining both high fibrinolytic activity and effective clot lysis on the vascular endothelial cell surface.
authors.affiliation: Department of Physiology, Hamamatsu University School of Medicine, Hamamatsu, Japan. seigan@hamamed.ac.jp
authors.forename: Yuko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Hideki
authors.initials: H
authors.lastname: Yasui
authors.forename: Tomasz
authors.initials: T
authors.lastname: Brzoska
authors.forename: Hideo
authors.initials: H
authors.lastname: Mogami
authors.forename: Tetsumei
authors.initials: T
authors.lastname: Urano
mesh_terms: D000954:Antigens, Surface / Q000378:metabolism; D002478:Cells, Cultured; D004526:Efficiency; D042783:Endothelial Cells / Q000378:metabolism* / Q000502:physiology; D005342:Fibrinolysis / Q000235:genetics / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D021381:Protein Transport / Q000502:physiology; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D014162:Transfection
chemical_list: D000954:Antigens, Surface; D049452:Green Fluorescent Proteins; D010959:Tissue Plasminogen Activator