The Inactive 44-kDa Processed Form of Membrane Type 1 Matrix Metalloproteinase (MT1-MMP) Enhances Proteolytic Activity via Regulation of Endocytosis of Active MT1-MMP

Abstract

Membrane type 1 (MT1) matrix metalloproteinase (MMP-14)is a membrane-tethered MMP considered to be a major mediator of pericellular proteolysis. MT1-MMP is regulated by a complex array of mechanisms, including processing and endocytosis that determine the pool of active proteases on the plasma membrane. Autocatalytic processing of active MT1-MMP generates an inactive membrane-tethered 44-kDa product (44-MT1) lacking the catalytic domain. This form preserves all other enzyme domains and is retained at the cell surface. Paradoxically, accumulation of the 44-kDa form has been associated with increased enzymatic activity. Here we report that expression of a recom- Membrane type 1 matrix metalloproteinase (MT1-MMP, 2 MMP-14) is a type I-transmembrane protease and a major mediator of pericellular proteolysis. MT1-MMP is responsible for the proteolytic cleavage of multiple pericellular and membrane-associated substrates, including collagens and other extracellular matrix proteins, growth factors, growth factor receptors, cell adhesion proteins and their receptors, cytokines, protease inhibitors, and proteases, just to mention a few (1-5). MT1-MMP is also the major physiological activator of pro-MMP-2 (pro-gelatinase A) on the cell surface (6, 7), a process that further contributes to pericellular proteolysis. As a multifunctional protease, MT1-MMP elicits profound effects on cell behavior and has been implicated in the pathogenesis of various human diseases, including cancer (8 -10), diabetes (11, 12), vascular (13, 14), and connective tissue diseases (2).The importance of MT1-MMP for pericellular proteolysis demands a tight control of its catalytic activity at the cell surface. This is partly achieved by the action of endogenous protease inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), which bind to the active site inhibiting catalysis (15). In addition, by virtue of being a membrane-anchored protease, MT1-MMP developed a unique set of regulatory mechanisms that control enzymatic activity independently of TIMPs. These processes include the targeting of active enzyme to specific plasma membrane locations, endocytosis, and autocatalytic processing (1, 16 -19). Together, these distinct processes determine the level of active enzyme on the cell surface. However, how these processes are integrated to control the pool of active MT1-MMP is not understood.The processing of MT1-MMP is a cell surface event in which the active enzyme is usually autocatalytically cleaved in trans to generate a major membrane-anchored product of ϳ44 kDa (also referred to as the 43-or 45-kDa species in some studies) and a soluble ϳ18-kDa inactive fragment of the catalytic domain (6, 20 -25). The 44-kDa product of MT1-MMP is detected in cultured cells expressing natural MT1-MMP (20, 26 -32) and has been found in platelets (33), human tumors extracts (34 -36), and extracts of arthritic synovial tissues (37). MT1-MMP processing is stimulated by a variety of factors known to stimulate MT1-MMP expression, trafficking, and/or endocytosi...

CD97 inhibits cell migration in human fibrosarcoma cells by modulating TIMP‐2/MT1‐ MMP/MMP‐2 activity – role of GPS autoproteolysis and functional cooperation between the N‐ and C‐terminal fragments

“…In all cases, the degree of MMP-2 activation was concomitant with the level of the truncated MT1-MMP form [28]. As it has been demonstrated that the~4 5-kDa truncated MT1-MMP form is derived from proteolytic degradation of the~60-kDa active form by self-cleavage or by active MMP-2 [29], these results further confirm that CD97 expression in HT1080 cells inhibits the activation of MT1-MMP and MMP-2.…”

ADAM12 redistributes and activates MMP-14, resulting in gelatin degradation, reduced apoptosis, and increased tumor growth

“…It should be noted that the increase in MMP-14 activity was not due to an increased amount of MMP-14 at the mRNA or protein level, but relies on its appropriate localization at the plasma membrane in accordance with earlier findings (Seiki 2003). Processing of MMP-14 at the cell surface is an event in which the active MMP-14 proteinases is autocatalytically cleaved to generate a membrane-anchored fragment of 43 kDa and a soluble 18 kDa inactive fragment of the catalytic domain (Cho et al, 2008;Ellerbroek et al, 2001;Itoh, 2006). Here, we detected the 43 kDa MMP-14 fragment in both tumor cell and tumor tissue extracts, further demonstrating that MMP-14 was present in an active form.…”

“…7D). To evaluate the influence of ADAM12 on MMP-14 activation, we analyzed the level of the partially autodigested 43 kDa fragment of MMP-14, which is indicative of active MMP-14 (Cho et al, 2008;Ellerbroek et al, 2001;Itoh, 2006), by western blotting (Fig. 7E).…”

Membrane-Type I Matrix Metalloproteinase-Dependent Regulation of Rheumatoid Arthritis Synoviocyte Function

“…Although the specific roles of secreted collagenases and MT-MMPs were not evaluated directly in their work, RA synoviocyte invasion was inhibited when cells were infected with an adenoviral vector encoding a MT1-MMP dominant-negative fragment previously reported to interfere with the catalytic activity of the wild-type enzyme (53). At this juncture, however, the utility of this indirect approach for implicating MT1-MMP can only be embraced cautiously because given that others have reported that the MT1-MMP fragment enhances, rather than inhibits, MT1-MMP proteolytic activity (54). Further, the possibility that the MT1-MMP dominant-negative construct exerts more complex effects on cell function by sequestering signaling molecules that normally bind to the MT1-MMP cytosolic tail has not yet been evaluated (55).…”