Ultrastructural localization of plasma membrane-associated urokinase-type plasminogen activator at focal contacts.
J Cell Biol
; 106(1): 87-95, 1988 Jan.
Article
em En
| MEDLINE
| ID: mdl-3123496
ABSTRACT
We have recently shown that urokinase-type plasminogen activator (u-PA) and plasminogen activator inhibitor type 1 are both found extracellularly beneath cultured human skin fibroblasts and HT-1080 sarcoma cells, but in distinct localizations. Here, the ultrastructural distribution of u-PA was studied using immunoferritin electron microscopy. In HT-1080 cells, u-PA on the extracellular aspect of the plasma membrane was detected at sites of direct contact of the cell with the growth substratum beneath all parts of the ventral cell surface. The ferritin-labeled adhesion plaques, which were enriched in submembraneous microfilaments, were frequently seen at the leading lamellae of the cells as well as in lamellipodia and microspikes. Besides the cell-substratum adhesion plaques, ferritin label was detected at cell-cell contact sites. Double-label immunofluorescence showed a striking colocalization of u-PA and vinculin in both HT-1080 cells and WI-38 lung fibroblasts, which is consistent with u-PA being a focal contact component. The u-PA-containing focal contacts of WI-38 cells had no direct codistribution with fibronectin fibrils. In WI-38 cells made stationary by cultivation in a medium containing 0.5% FCS, vinculin plaques became highly elongated and more centrally located, whereas u-PA immunolabel disappeared from such focal adhesions. These findings show that plasma membrane-associated u-PA is an intrinsic component of focal contacts, where, we propose, it enables directional proteolysis for cell migration and invasion.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Ativador de Plasminogênio Tipo Uroquinase
/
Adesão Celular
/
Membrana Celular
/
Espaço Extracelular
Tipo de estudo:
Risk_factors_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
1988
Tipo de documento:
Article