BINDING OF PLASMINOGEN TO CORNEAL FIBROBLASTS AND THEIR EXTRACELLULAR-MATRIX - EVIDENCE FOR A RECEPTOR IN CELL-MEMBRANES

Several components of the fibrinolytic system play an important role in tissue remodelling after wounding of the cornea, Secretion of tissue-type and urokinase-type plasminogen activators by corneal fibroblasts has been described previously, In this work, we report the existence of a plasminogen binding protein on the surface of cultured corneal fibroblasts and in the extracellular matrix produced by these cells, This receptor was characterized on ligand-blots and localized by fluorescence cytochemistry using biotinylated plasminogen and labelled streptavidin, Plasminogen binding to cells was specific, saturable, dose dependent and inhibited by E-aminocaproic acid, indicating that the lysine binding sites of plasminogen are involved in its interaction with the cells and extracellular matrix, The plasminogen bound to corneal fibroblasts and their matrix was activated by t-PA secreted by the corneal fibroblasts themselves, The receptor was characterized by ligand blotting using biotinylated plasminogen, It was insoluble in water solution, but it could be solubilized in 1% SDS or 0.1% Triton X-100. The receptor was purified by affinity chromatography on biotinylated plasminogen coupled to a streptavidin-agarose gel.