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Luigi Nezi, Dario Greco, Lucio Nitsch, Corrado Garbi
The Role of Proteases in Fibronectin Matrix Remodeling in Thyroid Epithelial Cell Monolayer Cultures
Fischer rat thyroid (FRT) cells organize a matrix of extracellular fibronectin (FN) fibrils, which undergoes extensive remodeling according to cell culture confluence. In nonconfluent cells FN forms a fibrillar array associated with the ventral cell surface. However, basal FN is progressively removed in confluent cultures and substituted by nonfibrillar FN deposits at lateral cell domains in regions of cellcell contacts. FRT cells secrete and expose on the plasma membrane the tissuetype plasminogen activator and, in serumfree cultures, plasminogen induces a rapid loss of FN fibrils. Incubation with plasmin inhibitors greatly reduces this effect. FRT cells also express annexin II, a plasminogen receptor, suggesting that plasmin activity is associated with the pericellular enviroment. This is in agreement with the observation that a great reduction in FN degradation is observed if the cells are preincubated with carboxypeptidase B, which prevents plasminogen binding to the cells. A gelatinolytic activity with a molecular weigth equivalent to MMP-2 has been demonstrated by zymography of culture media, and the presence of MMP-2 and MT1-MMP on the cell plasma membrane has been detected by immunofluorescence. These results indicate that in the FN remodeling process, occurring during FRT epithelium maturation, both plasmindependent (tPA activated) and plasminindependent proteolytic activities are involved.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 383, 01/2002
Pages: 167 - 176