TISSUE INHIBITOR OF METALLOPROTEINASES-2 INHIBITS THE ACTIVATION OF 72 KDA PROGELATINASE BY FIBROBLAST MEMBRANES

We report that monolayers of human fibroblasts stimulated with concanavalin A were able to activate 72 kDa progelatinase but not 95 kDa progelatinase. The activating capacity of fibroblasts appeared approx. 6 h after concanavalin A stimulation and was blocked by cycloheximide. The activation of 72 kDa progelatinase was readily inhibited by TIMP-2 but only poorly by TIMP-1. Plasma membranes isolated from the fibroblasts were capable of activating 72 kDa progelatinase. The cleavage products of the plasma membrane-mediated activation of 72 kDa progelatinase corresponded to those of organomercurial-induced self-cleavage. Only inhibitors of metalloproteinase self-cleavage inhibited the activating capacity of plasma membrane preparations, although the activating capacity was destroyed by trypsin and heat. As with the fibroblast monolayers, TIMP-2 was a potent inhibitor of the membrane-mediated activation whereas TIMP-1 was less so.