title: TIMP independence of matrix metalloproteinase (MMP)-2 activation by membrane type 2 (MT2)-MMP is determined by contributions of both the MT2-MMP catalytic and hemopexin C domains.
abstract: The important and distinct contribution that membrane type 2 (MT2)-matrix metalloproteinase (MMP) makes to physiological and pathological processes is now being recognized. This contribution may be mediated in part through MMP-2 activation by MT2-MMP. Using Timp2-/- cells, we previously demonstrated that MT2-MMP activates MMP-2 to the fully active form in a pathway that is TIMP-2-independent but MMP-2 hemopexin carboxyl (C) domain-dependent. In this study cells expressing MT2-MMP as well as chimera proteins in which the C-terminal half of MT2-MMP and MT1-MMP were exchanged showed that the MT2-MMP catalytic domain has a higher propensity than that of MT1-MMP to initiate cleavage of the MMP-2 prodomain in the absence of TIMP-2. Although we demonstrate that MT2-MMP is a weak collagenase, this first activation cleavage was enhanced by growing the cells in type I collagen gels. The second activation cleavage to generate fully active MMP-2 was specifically enhanced by a soluble factor expressed by Timp2-/- cells and was MT2-MMP hemopexin C domain-dependent; however, the RGD sequence within this domain was not involved. Interestingly, in the presence of TIMP-2, a MT2-MMP.MMP-2 trimolecular complex formed, but activation was not enhanced. Similarly, TIMP-3 did not promote MT2-MMP-mediated MMP-2 activation but inhibited activation at higher concentrations. This study demonstrates the influence that both the catalytic and hemopexin C domains of MT2-MMP exert in determining TIMP independence in MMP-2 activation. In tissues or pathologies characterized by low TIMP-2 expression, this pathway may represent an alternative means of rapidly generating low levels of active MMP-2.
authors.affiliation: Centre for Blood Research and Department of Oral Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: Morrison
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Overall
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D020134:Catalytic Domain; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D006224:Cricetinae; D017077:Culture Media, Conditioned; D004789:Enzyme Activation; D006466:Hemopexin / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000737:chemistry / Q000378:metabolism; D053511:Matrix Metalloproteinase 14 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053517:Matrix Metalloproteinase 15 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D024042:Collagen Type I; D017077:Culture Media, Conditioned; D016023:Integrins; D011993:Recombinant Fusion Proteins; D019716:Tissue Inhibitor of Metalloproteinase-2; D006466:Hemopexin; D053517:Matrix Metalloproteinase 15; D020778:Matrix Metalloproteinase 2; D053511:Matrix Metalloproteinase 14