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 i n 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 fi broblasts and in the extracellular matrix produced by these cells, Thi s receptor was characterized on ligand-blots and localized by fluoresc ence cytochemistry using biotinylated plasminogen and labelled strepta vidin, Plasminogen binding to cells was specific, saturable, dose depe ndent 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 fibr oblasts and their matrix was activated by t-PA secreted by the corneal fibroblasts themselves, The receptor was characterized by ligand blot ting using biotinylated plasminogen, It was insoluble in water solutio n, but it could be solubilized in 1% SDS or 0.1% Triton X-100. The rec eptor was purified by affinity chromatography on biotinylated plasmino gen coupled to a streptavidin-agarose gel.