title: Localization of urokinase-type plasminogen activator receptor on U937 cells: phorbol ester PMA induces heterogeneity.
abstract: The binding of human urokinase-type plasminogen activator (u-PA) to the surface of the human monocytic cell line U937 was studied by immunological detection of bound u-PA or binding of biotinylated diisopropyl fluorophosphate-inactivated human u-PA visualized by light or electron microscopy. Untreated U937 cells showed a characteristic binding pattern, with the majority of the u-PA bound to the microvillar-containing protruding pole of the cells. After treatment with the phorbol ester PMA, the resulting adherent cell population was very heterogeneous with respect to both cellular morphology and u-PA binding. The bound u-PA was distributed on both the dorsal and the substrate side of the cells, and the patches of bound u-PA could not be correlated to any typical membrane conformations or cell-cell or cell-substratum contacts. When a monoclonal antibody directed against the amino-terminal fragment (ATF) of u-PA was used, the results were identical regardless of whether intact u-PA or ATF was used for binding to the cells. In contrast, when a monoclonal antibody recognizing the non-receptor-binding protease domain of u-PA was used, bound ATF showed no staining, while bound intact u-PA was stained as efficiently as above. The alteration of u-PA receptor distribution following treatment with PMA could be related to the changes in glycosylation and ligand affinity of the purified u-PA receptor previously described following PMA treatment of U937 cells.
authors.affiliation: Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.
authors.forename: S H
authors.initials: SH
authors.lastname: Hansen
authors.forename: N
authors.initials: N
authors.lastname: Behrendt
authors.forename: K
authors.initials: K
authors.lastname: Danø
authors.forename: P
authors.initials: P
authors.lastname: Kristensen
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003907:Dexamethasone / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D016403:Lymphoma, Large B-Cell, Diffuse; D008854:Microscopy, Electron; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000187:drug effects / Q000648:ultrastructure; D055293:Receptors, Urokinase Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D003907:Dexamethasone; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate