title: The role of proteases in fibronectin matrix remodeling in thyroid epithelial cell monolayer cultures.
abstract: Fischer rat thyroid (FRT) cells organize a matrix of extracellular fibronectin (FN) fibrils, which undergoes extensive remodeling according to cell culture confluence. In non-confluent cells FN forms a fibrillar array associated with the ventral cell surface. However, basal FN is progressively removed in confluent cultures and substituted by non-fibrillar FN deposits at lateral cell domains in regions of cell-cell contacts. FRT cells secrete and expose on the plasma membrane the tissue-type plasminogen activator and, in serum-free 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 pre-incubated 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 plasmin-dependent (tPA activated) and plasmin-independent proteolytic activities are involved.
authors.affiliation: Centro di Endocrinologia ed Oncologia Sperimentale, CNR, Dpt. Biologia e Patologia Cellulare e Molecolare, Napoli, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Nezi
authors.forename: Dario
authors.initials: D
authors.lastname: Greco
authors.forename: Lucio
authors.initials: L
authors.lastname: Nitsch
authors.forename: Corrado
authors.initials: C
authors.lastname: Garbi
mesh_terms: D000818:Animals; D017306:Annexin A2 / Q000378:metabolism; D002450:Cell Communication; D018929:Cell Culture Techniques; D010450:Endopeptidases / Q000378:metabolism / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology* / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000378:metabolism; D051381:Rats; D013961:Thyroid Gland / Q000166:cytology*; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000378:metabolism
chemical_list: D017306:Annexin A2; D005353:Fibronectins; D019716:Tissue Inhibitor of Metalloproteinase-2; D010450:Endopeptidases; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2