The topology of plasminogen binding and activation on the surface of human breast cancer cells.
The urokinase-dependent activation of plasminogen by breast cancer cells plays an important role in metastasis. We have previously shown that the metastatic breast cancer cell line MDA-MB-231 over-expresses urokinase and binds and efficiently activates plasminogen at the cell surface compared to non-metastatic cells. The aim of this study was to further characterise plasminogen binding and determine the topology of cell surface-bound plasminogen in terms of its potential for activation. The lysine-dependent binding of plasminogen at 4 degrees C to MDA-MB-231 cells was stable and resulted in an activation-susceptible conformation of plasminogen. Topologically, a fraction of bound plasminogen was co-localised with urokinase on the surfaces of MDA-MB-231 cells where it could be activated to plasmin. At 37 degrees C plasmin was rapidly lost from the cell surface. Apart from actin, other candidate plasminogen receptors were either not expressed or did not co-localise with plasminogen at the cell surface. Thus, based on co-localisation with urokinase, plasminogen binding is partitioned into two functional pools on the surface of MDA-MB-231 cells. In conclusion, these results shed further light on the functional organisation of the plasminogen activation cascade on the surface of a metastatic cancer cell.
Andronicos
N M
NM
Department of Biological Sciences, University of Wollongong, NSW Australia, 2522.
Ranson
M
M
D000199:Actins / Q000378:metabolism; D017306:Annexin A2 / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D018613:Microscopy, Confocal; D009362:Neoplasm Metastasis; D010958:Plasminogen / Q000302:isolation & purification / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D014407:Tumor Cells, Cultured / Q000502:physiology* / Q000648:ultrastructure; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
D000199:Actins; D017306:Annexin A2; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010958:Plasminogen; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator