The propeptide domain of membrane type 1 matrix metalloproteinase is required for binding of tissue inhibitor of metalloproteinases and for activation of pro-gelatinase A

Activation of secreted latent matrix metalloproteinases (MMPs) is accompani ed by cleavage of the N-terminal propeptide, thereby liberating the active zinc from binding to the conserved cysteine in the pro-domain. It has been assumed that an analogous mechanism is responsible for the activation of me mbrane type 1 MMP (MT1-MMP). Using recombinant wild-type MT1-MMP cDNA and m utant cDNAs transfected into COS-l cells lacking endogenous MT1-MMP, we hav e examined the function of the propeptide domain of MT1-MMP. MT1-MMP was ch aracterized by immunoblotting, surface biotinylation, gelatin substrate zym ography, and I-125-tissue inhibitor of metalloproteinases 2 (TIMP-2) bindin g. In Contrast to wild-type MT1-MMP-transfected COS-l cells, transfected CO S-l cells containing a deletion of the N-terminal propeptide domain of MT1- MMP or a chimeric construction (substitution of the pro-domain of MT1-MMP w ith that of collagenase 3) were functionally inactive in terms of binding o f I-125-Iabeled TIMP-2 to the cell surface and initiating the activation of progelatinase A These results support the concept that in its native plasm a membrane-inserted form, the pro-domain of MT1-MMP plays an essential role in TIMP-2 binding and subsequent activation of pro-gelatinase A.