Individual Timp Deficiencies Differentially Impact Pro-MMP-2 Activation

Abstract

Membrane-type matrix metalloproteinases (MT-MMPsTIMP-4 associates with MMP-2 and MT1-MMP in a manner similar to TIMP-3, but its deletion had no effect on pro-MMP-2 processing. Thus, TIMP-3 provides an inherent regulation over the kinetics of pro-MMP-2 processing, serving at a level distinct from that of TIMP-2 and TIMP-4.Matrix metalloproteinases (MMPs) 2 are fundamental to biological processes because of their ability to cleave and remodel the extracellular matrix (ECM). MT1-MMP is one of six cell surface membrane-type MMPs (MT-MMP). Its activity and regulation have been widely studied in the context of cell surface MMP activation, cell migration, and invasion (1-3), independently and in conjunction with other cell adhesion molecules (4 -10). A key function of MT1-MMP is to process pro-MMP-2, whose activity also correlates with an invasive propensity in several cancers and is predictive of poor survival (reviewed in . Understanding the regulation of pro-MMP-2 processing by MT1-MMP and other members of the MT-MMP family is central to defining their role in cancer biology.The classical model for the cell surface activation of MMP-2 is through the formation of a trimolecular complex comprising MT1-MMP, TIMP-2, and pro-MMP-2 (15). The transmembrane MT1-MMP interacts via its N-terminal domain to the N terminus of TIMP-2, forming a "receptor" onto which pro-MMP-2 (72 kDa) binds. Pro-MMP-2 is initially cleaved to its intermediate form (64 kDa) by an adjacent active MT1-MMP. The second stage of MMP-2 processing, resulting in its fully active form (62 kDa), involves an autocatalytic event that requires an MMP-2 molecule in trans (16). It is known that of the six MT-MMPs, MT2-, 3-, 5-, and 6-MMP (17-21) also have the capacity to activate pro-MMP-2. Alternative mechanisms of MMP-2 processing at the plasma membrane, such as the urokinase plasminogen system (22, 23) or TIMP-independent processing involving MT2-MMP, have also been suggested (24). Although the dynamics of the trimolecular complex have been well studied, new insights into its regulation and control are continually being discovered. More recently, cell surface processing of pro-MMP-2 is reported to occur through formation of a trimolecular complex comprised of MT3-MMP, TIMP-3, and pro-MMP-2 (25), although TIMP-3 is known not to form similar complexes with MT1-MMP (26).TIMPs are the naturally occurring inhibitors of metalloproteinase activity. There are four members of the TIMP family, and each has a specific niche with respect to function. Studies have focused on the dual role of TIMP-2 in regulating the processing of pro-MMP-2. A threshold level of TIMP-2 is required in relation to MT1-MMP to construct the trimolecular complex, which still leaves sufficient MT1-MMP uninhibited to cleave pro-MMP-2. At higher concentrations, TIMP-2 prevents MMP-2 processing by inhibiting all free MT1-MMP (27-29). The presence of TIMP-2 was initially considered necessary to achieve any form of MMP-2 processing (30, 31), but recently Timp-2 Ϫ/Ϫ cells were shown capable of some pro...

Tissue Inhibitor of Metalloproteinase-1 Moderates Airway Re-Epithelialization by Regulating Matrilysin Activity

“…44,[73][74][75][76] Accordingly, we found that TIMP-1 deficiency, but not TIMP-2 deficiency, enhanced airway re-epithelialization implying that the regulation of matrilysin-mediated cell spreading and migration is specific to TIMP-1 and is not a generalized process among different members of the TIMP family. Although TIMP-1 can modulate cell apoptosis, survival, and proliferation through MMP-independent mechanisms, 25,77,78 we conclude that the moderating effect TIMP-1 confers on epithelial regeneration is a consequence of its ability to block MMP activity, specifically that of matrilysin.…”

Regulatory Mechanism of Matrix Metalloprotease-2 Enzymatic Activity by Factor Xa and Thrombin

“…Furthermore, trypsin-2-processed MMP-2 was obtained by incubating purified pro-MMP-2 with trypsin-2 under cell-free conditions (40). Therefore, autoproteolytic processing of trypsin-2-cleaved MMP-2 is not likely to occur, since cellular molecules, such as TIMP-2 and integrin ␣v␤3, may be required for the maturation of partially processed MMP-2 to its fully active form (10,12,33,47). This may explain the partial activation of trypsin-2-processed MMP-2 seen under cell-free conditions.…”

“…Despite the importance of TIMP-2 and integrin ␣v␤3 in the autoproteolytic activation of MMP-2 following MT1-MMPcleavage (10,33,47), these molecules are not likely to be involved in the complete activation of factor Xa-processed MMP-2. Full activation of MMP-2 was not affected in MCF-7 cells that express negligible amounts of TIMP-2 and HEK293F cells transfected with integrin ␣v small interfering RNA (data not shown).…”

Enhanced metastatic dissemination to multiple organs by melanoma and lymphoma cells in timp-3−/− mice

“…The MMP-2 activation seen at 48 h, which is the period of B16F10 cell extravasation, may be particularly important in facilitating extravasation of these cells across the basement membrane in timp-3 À/À lung. Notably, we have recently reported that timp-3 plays a significant role in the inhibition of pro-MMP-2 activation by comparing mouse embryo Enhanced metastatic dissemination to multiple organs W Cruz-Munoz et al fibroblasts deficient in each of the four timp genes (English et al, 2006). In contrast to timp-3 À/À , timp-1 À/À mice show no difference in their lung colonization when challenged with tumorigenic cells in experimental metastasis assays (Soloway et al, 1996).…”

“…Our recent studies show that timp-3 À/À mouse embryonic fibroblasts have accelerated MT1-MMP-dependent pro-MMP-2 activation (English et al, 2006). We asked whether increased extravasation of B16F10 cells in timp-3 À/À lungs associated with increased MMP-2 activation.…”