title: Human glioma U-251 cells contain type 1 plasminogen activator inhibitor in a rapidly releasable form.
abstract: Because recent information suggests that the localized deposition of protease inhibitors is one mechanism by which cells regulate pericellular proteolysis during tissue invasion, the distribution of type 1 plasminogen activator inhibitor (PA1-1) associated with the invasive human glioma cell line U-251 was investigated. Direct and reverse fibrin zymography indicated the presence of urokinase-like plasminogen activator (u-PA) and PAI-1 in U-251 conditioned media and cell lysates. PA1-1 antigen was detected immunologically in cytoplasmic granules present within cellular processes of U-251 cells and these organelles could be isolated on Percoll density gradients in a high density band. In contrast, u-PA activity and another secreted protein, amyloid beta-protein precursor, were only present in the low density region of the gradients. Functional analysis of PAI-1 in the granules contained within the high density fractions revealed the presence of active PAI-1. Incubation of U-251 cells with the secretagogue, 8-bromoadenosine 3':5'-cyclic monophosphate, resulted in a 3-fold increase in the release of PAI-1 in the media conditioned by these cells. These data suggest that the human glioma cell line U-251 contains PAI-1 in a rapidly releasable form, which may provide another mechanism by which these tumors could regulate proteolytic activity in a localized manner.
authors.affiliation: Department of Vascular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Salonen
authors.forename: L
authors.initials: L
authors.lastname: Gombau
authors.forename: E
authors.initials: E
authors.lastname: Engvall
authors.forename: R R
authors.initials: RR
authors.lastname: Schleef
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D002458:Cell Fractionation; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D005337:Fibrin; D005342:Fibrinolysis; D005910:Glioma; D006801:Humans; D007150:Immunohistochemistry; D009361:Neoplasm Invasiveness; D015388:Organelles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D017395:Plasminogen Activator Inhibitor 1 / Q000302:isolation & purification / Q000378:metabolism*; D011205:Povidone; D012822:Silicon Dioxide; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D017395:Plasminogen Activator Inhibitor 1; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016039:Percoll; D012822:Silicon Dioxide; D005337:Fibrin; D014568:Urokinase-Type Plasminogen Activator; D011205:Povidone