Plasmin on adherent cells: from microvesiculation to apoptosis.
Cell activation by stressors is characterized by a sequence of detectable phenotypic cell changes. A given stimulus, depending on its strength, induces modifications in the activity of membrane phospholipid transporters and calpains, which lead to phosphatidylserine exposure, membrane blebbing and the release of microparticles (nanoscale membrane vesicles). This vesiculation could be considered as a warning signal that may be followed, if the stimulus is maintained, by cell detachment-induced apoptosis. In the present study, plasminogen incubated with adherent cells is converted into plasmin by constitutively expressed tPA (tissue-type plasminogen activator) or uPA (urokinase-type plasminogen activator). Plasmin formed on the cell membrane then induces a unique response characterized by membrane blebbing and vesiculation. Hitherto unknown for plasmin, these membrane changes are similar to those induced by thrombin on platelets. If plasmin formation persists, matrix proteins are then degraded, cells lose their attachments and enter the apoptotic process, characterized by DNA fragmentation and specific ultrastructural features. Since other proteolytic or inflammatory stimuli may evoke similar responses in different types of adherent cells, the proposed experimental procedure can be used to distinguish activated adherent cells from cells entering the apoptotic process. Such a distinction is crucial for evaluating the effects of mediators, inhibitors and potential therapeutic agents.
Doeuvre
Loïc
L
Inserm U919, GiP Cyceron, Bd Henri Becquerel, 14074 Caen, France.
Plawinski
Laurent
L
Goux
Didier
D
Vivien
Denis
D
Anglés-Cano
Eduardo
E
D000818:Animals; D017209:Apoptosis; D001792:Blood Platelets / Q000166:cytology / Q000502:physiology*; D015153:Blotting, Western; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D005341:Fibrinolysin / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D007700:Kinetics; D008854:Microscopy, Electron; D010958:Plasminogen / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D010959:Tissue Plasminogen Activator / Q000502:physiology
D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin