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  • Author: Dagmar Orgel x
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Abstract

Membrane binding of urokinase type plasminogen activator (u-PA) is thought to play a pivotal role in connective tissue remodeling and invasive processes. We compare the ability of different matrix-metalloproteinases involved in connective tissue turnover to cleave pro-urokinase type plasminogen activator between the catalytic domain and the receptor binding part to investigate a potential role for matrix-metalloproteinases in the regulation of membrane-associated proteolytic activity. We employed several forms of human stromelysin-1 (full length, C-truncated, and recombinant catalytic domain), rabbit C-truncated stromelysin-1, the human gelatinases A and B and the human catalytic domain of neutrophil collagenase. The gelatinases and the collagenase did not separate the receptor binding domain of pro-urokinase type plasminogen activator from the catalytic domain, whereas all stromelysin-1 forms cleaved the glutamic acid 143-leucine 144 bond of pro-urokinase type plasminogen activator. This reaction could be inhibited by specific inhibitors of matrix metalloproteinases and was not affected by inhibitors of serine proteinases. The M r 31000 cleavage product with leucine 144 as N-terminus displayed no proteolytic activity towards the prourokinase type plasminogen activator substrate pyro-Glu-Gly-Arg-pNA-HCl (S2444), but it could be activated by an additional treatment with plasmin. Comparison between full length stromelysin-1 and its C-truncated forms, showed that both exhibited the same cleavage properties towards pro-urokinase type plasminogen activator. Thus, the cleavage of pro-urokinase type plasminogen activator by stromelysin-1 is not influenced by the presence or absence of the C-terminal domain. The recombinant catalytic domain of MMP-3 generated pro-urokinase type plasminogen activator, whereas incubation of pro-urokinase type plasminogen activator with the native forms of human or rabbit stromelysin-1 led to a moderate activation of pro-uPA due to an additional cleavage that is catalyzed by a serine proteinase.