Characterization of a truncated recombinant form of human membrane type 3 matrix metalloproteinase

Matrix Metalloproteinases Shape the Tumor Microenvironment in Cancer Progression

Cancer progression with uncontrolled tumor growth, local invasion, and metastasis depends largely on the proteolytic activity of numerous matrix metalloproteinases (MMPs), which affect tissue integrity, immune cell recruitment, and tissue turnover by degrading extracellular matrix (ECM) components and by releasing matrikines, cell surface-bound cytokines, growth factors, or their receptors. Among the MMPs, MMP-14 is the driving force behind extracellular matrix and tissue destruction during cancer invasion and metastasis. MMP-14 also influences both intercellular as well as cell-matrix communication by regulating the activity of many plasma membrane-anchored and extracellular proteins. Cancer cells and other cells of the tumor stroma, embedded in a common extracellular matrix, interact with their matrix by means of various adhesive structures, of which particularly invadopodia are capable to remodel the matrix through spatially and temporally finely tuned proteolysis. As a deeper understanding of the underlying functional mechanisms is beneficial for the development of new prognostic and predictive markers and for targeted therapies, this review examined the current knowledge of the interplay of the various MMPs in the cancer context on the protein, subcellular, and cellular level with a focus on MMP14.

The impact of collagen protein ingestion on musculoskeletal connective tissue remodeling: a narrative review

Collagen is the central structural component of extracellular connective tissue, which provides elastic qualities to tissues. For skeletal muscle, extracellular connective tissue transmits contractile force to the tendons and bones. Connective tissue proteins are in a constant state of remodeling and have been shown to express a high level of plasticity. Dietary-protein ingestion increases muscle protein synthesis rates. High-quality, rapidly digestible proteins are generally considered the preferred protein source to maximally stimulate myofibrillar (contractile) protein synthesis rates. In contrast, recent evidence demonstrates that protein ingestion does not increase muscle connective tissue protein synthesis. The absence of an increase in muscle connective tissue protein synthesis after protein ingestion may be explained by insufficient provision of glycine and/or proline. Dietary collagen contains large amounts of glycine and proline and, therefore, has been proposed to provide the precursors required to facilitate connective tissue protein synthesis. This literature review provides a comprehensive evaluation of the current knowledge on the proposed benefits of dietary collagen consumption to stimulate connective tissue remodeling to improve health and functional performance.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

Matrix metalloproteinase collagenolysis in health and disease

The proteolytic processing of collagen (collagenolysis) is critical in development and homeostasis, but also contributes to numerous pathologies. Mammalian interstitial collagenolytic enzymes include members of the matrix metalloproteinase (MMP) family and cathepsin K. While MMPs have long been recognized for their ability to catalyze the hydrolysis of collagen, the roles of individual MMPs in physiological and pathological collagenolysis are less defined. The use of knockout and mutant animal models, which reflect human diseases, has revealed distinct collagenolytic roles for MT1-MMP and MMP-13. A better understanding of temporal and spatial collagen processing, along with the knowledge of the specific MMP involved, will ultimately lead to more effective treatments for cancer, arthritis, cardiovascular conditions, and infectious diseases. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Matrix metalloproteinases in the brain and blood-brain barrier: Versatile breakers and makers

Matrix metalloproteinases are versatile endopeptidases with many different functions in the body in health and disease. In the brain, matrix metalloproteinases are critical for tissue formation, neuronal network remodeling, and blood-brain barrier integrity. Many reviews have been published on matrix metalloproteinases before, most of which focus on the two best studied matrix metalloproteinases, the gelatinases MMP-2 and MMP-9, and their role in one or two diseases. In this review, we provide a broad overview of the role various matrix metalloproteinases play in brain disorders. We summarize and review current knowledge and understanding of matrix metalloproteinases in the brain and at the blood-brain barrier in neuroinflammation, multiple sclerosis, cerebral aneurysms, stroke, epilepsy, Alzheimer's disease, Parkinson's disease, and brain cancer. We discuss the detrimental effects matrix metalloproteinases can have in these conditions, contributing to blood-brain barrier leakage, neuroinflammation, neurotoxicity, demyelination, tumor angiogenesis, and cancer metastasis. We also discuss the beneficial role matrix metalloproteinases can play in neuroprotection and anti-inflammation. Finally, we address matrix metalloproteinases as potential therapeutic targets. Together, in this comprehensive review, we summarize current understanding and knowledge of matrix metalloproteinases in the brain and at the blood-brain barrier in brain disorders.

Mechanisms of the epithelial-to-mesenchymal transition in sea urchin embryos

Sea urchin mesenchyme is composed of the large micromere-derived spiculogenetic primary mesenchyme cells (PMC), veg2-tier macromere-derived non-spiculogenetic mesenchyme cells, the small micromere-derived germ cells, and the macro- and mesomere-derived neuronal mesenchyme cells. They are formed through the epithelial-to-mesenchymal transition (EMT) and possess multipotency, except PMCs that solely differentiate larval spicules. The process of EMT is associated with modification of epithelial cell surface property that includes loss of affinity to the apical and basal extracellular matrices, inter-epithelial cell adherens junctions and epithelial cell surface-specific proteins. These cell surface structures and molecules are endocytosed during EMT and utilized as initiators of cytoplasmic signaling pathways that often initiate protein phosphorylation to activate the gene regulatory networks. Acquisition of cell motility after EMT in these mesenchyme cells is associated with the expression of proteins such as Lefty, Snail and Seawi. Structural simplicity and genomic database of this model will further promote detailed EMT research.

CCN1 (Cyr61) Is Overexpressed in Human Osteoarthritic Cartilage and Inhibits ADAMTS-4 (Aggrecanase 1) Activity

OBJECTIVE

ADAMTS-4, also called aggrecanase 1, is considered to play a key role in aggrecan degradation in human osteoarthritic (OA) cartilage, but information about regulators of ADAMTS-4 aggrecanase activity remains limited. We undertook this study to search for molecules that modulate ADAMTS-4 activity.

METHODS

Molecules copurified with ADAMTS-4 from ADAMTS-4-transfected chondrocytic cells were sequenced by nanoscale liquid chromatography tandem mass spectrometry. Binding activity was determined by immunoprecipitation and solid-phase binding assay. Effects on ADAMTS-4 activity were examined by aggrecan digestion assay. Expression of the binding molecule in OA cartilage and chondrocytes was examined by immunohistochemistry and reverse transcription-polymerase chain reaction.

RESULTS

We identified CCN1 (Cyr61) as an ADAMTS-4-binding protein and showed specific binding to the ADAMTS-4 cysteine-rich domain. Aggrecanase activity of ADAMTS-4 was inhibited by interaction with CCN1. Expression of messenger RNA for CCN1 was significantly higher in human OA cartilage than in normal cartilage. CCN1 was immunolocalized to chondrocytes in OA cartilage, showing direct correlations of immunoreactivity with the Mankin score of cartilage lesions and chondrocyte cloning. CCN1 and ADAMTS-4 were commonly coexpressed in clustered chondrocytes. CCN1 expression in OA chondrocytes was down-regulated by interleukin-1α (IL-1α) and up-regulated by transforming growth factor β (TGFβ). ADAMTS-4 expression was induced by treatment with IL-1α or TGFβ, but aggrecanase activity was detected only under stimulation with IL-1α. TGFβ-treated chondrocytes exhibited aggrecanase activity when CCN1 expression was knocked down.

CONCLUSION

Our findings provide the first evidence that CCN1 suppresses ADAMTS-4 activity and that CCN1 overexpression is directly correlated with chondrocyte cloning in OA cartilage. Our results suggest that the TGFβ/CCN1 axis plays a role in chondrocyte cluster formation through inhibition of ADAMTS-4.

MMP16 Mediates a Proteolytic Switch to Promote Cell-Cell Adhesion, Collagen Alignment, and Lymphatic Invasion in Melanoma

Lymphatic invasion and accumulation of continuous collagen bundles around tumor cells are associated with poor melanoma prognosis, but the underlying mechanisms and molecular determinants have remained unclear. We show here that a copy-number gain or overexpression of the membrane-type matrix metalloproteinase MMP16 (MT3-MMP) is associated with poor clinical outcome, collagen bundle assembly around tumor cell nests, and lymphatic invasion. In cultured WM852 melanoma cells derived from human melanoma metastasis, silencing of MMP16 resulted in cell-surface accumulation of the MMP16 substrate MMP14 (MT1-MMP) as well as L1CAM cell adhesion molecule, identified here as a novel MMP16 substrate. When limiting the activities of these trans-membrane protein substrates toward pericellular collagen degradation, cell junction disassembly, and blood endothelial transmigration, MMP16 supported nodular-type growth of adhesive collagen-surrounded melanoma cell nests, coincidentally steering cell collectives into lymphatic vessels. These results uncover a novel mechanism in melanoma pathogenesis, whereby restricted collagen infiltration and limited mesenchymal invasion are unexpectedly associated with the properties of the most aggressive tumors, revealing MMP16 as a putative indicator of adverse melanoma prognosis.

Membrane-type matrix metalloproteinases: Their functions and regulations

Membrane-type matrix metalloproteinases (MT-MMPs) form a subgroup of the matrix metalloproteinase (MMP) family, and there are 6 MT-MMPs in humans. MT-MMPs are further sub-classified into type I transmembrane-type (MT1, -MT2-, MT3- and MT5-MMPs) and glycosylphosphatidylinositol (GPI)-anchored type (MT4- and MT6-MMPs). In either case MT-MMPs are tethered to the plasma membrane, and this cell surface expression provides those enzymes with unique functionalities affecting various cellular behaviours. Among the 6 MT-MMPs, MT1-MMP is the most investigated enzyme and many of its roles and regulations have been revealed to date, but the potential roles and regulatory mechanisms of other MT-MMPs are gradually getting clearer as well. Further investigations of MT-MMPs are likely to reveal novel pathophysiological mechanisms and potential therapeutic strategies for different diseases in the future.

Matrix metalloproteinases in inflammation

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of ubiquitously expressed zinc-dependent endopeptidases with broad substrate specificity and strictly regulated tissue specific expression. They are expressed in physiological situations and pathological conditions involving inflammation. MMPs regulate several functions related to inflammation including bioavailability and activity of inflammatory cytokines and chemokines. There is also evidence that MMPs regulate inflammation in tumor microenvironment, which plays an important role in cancer progression.

SCOPE OF REVIEW

Here, we discuss the current view on the role of MMPs in the regulation of inflammation.

MAJOR CONCLUSIONS

MMPs modulate inflammation by regulating bioavailability and activity of cytokines, chemokines, and growth factors, as well as integrity of physical tissue barriers. MMPs are also involved in immune evasion of tumor cells and in regulation of inflammation in tumor microenvironment.

GENERAL SIGNIFICANCE

There is increasing evidence for non-matrix substrates of MMPs that are related to regulation of inflammatory processes. New methods have been employed for identification of the substrates of MMPs in inflammatory processes in vivo. Detailed information on the substrates of MMPs may offer more specific and effective ways of inhibiting MMP function by blocking the cleavage site in substrate or by inhibition of the bioactivity of the substrate. It is expected, that more precise information on the MMP-substrate interaction may offer novel strategies for therapeutic intervention in inflammatory diseases and cancer without blocking beneficial actions of MMPs. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Membrane-type-3 matrix metalloproteinase (MT3-MMP) functions as a matrix composition-dependent effector of melanoma cell invasion

In primary human melanoma, the membrane-type matrix metalloproteinase, MT3-MMP, is overexpressed in the most aggressive nodular-type tumors. Unlike MT1-MMP and MT2-MMP, which promote cell invasion through basement membranes and collagen type I-rich tissues, the function of MT3-MMP in tumor progression remains unclear. Here, we demonstrate that MT3-MMP inhibits MT1-MMP-driven melanoma cell invasion in three-dimensional collagen, while yielding an altered, yet MT1-MMP-dependent, form of expansive growth behavior that phenocopies the formation of nodular cell colonies. In melanoma cell lines originating from advanced primary or metastatic lesions, endogenous MT3-MMP expression was associated with limited collagen-invasive potential. In the cell lines with highest MT3-MMP expression relative to MT1-MMP, collagen-invasive activity was increased following stable MT3-MMP gene silencing. Consistently, MT3-MMP overexpression in cells derived from less advanced superficially spreading melanoma lesions, or in the MT3-MMP knockdown cells, reduced MT1-MMP-dependent collagen invasion. Rather than altering MT1-MMP transcription, MT3-MMP interacted with MT1-MMP in membrane complexes and reduced its cell surface expression. By contrast, as a potent fibrinolytic enzyme, MT3-MMP induced efficient invasion of the cells in fibrin, a provisional matrix component frequently found at tumor-host tissue interfaces and perivascular spaces of melanoma. Since MT3-MMP was significantly upregulated in biopsies of human melanoma metastases, these results identify MT3-MMP as a matrix-dependent modifier of the invasive tumor cell functions during melanoma progression.

Membrane-type matrix metalloproteinase-3 regulates neuronal responsiveness to myelin through Nogo-66 receptor 1 cleavage

Nogo-66 receptor 1 (NgR1) is a glycosylphosphatidylinositol-anchored receptor for myelin-associated inhibitors that restricts plasticity and axonal regrowth in the CNS. NgR1 is cleaved from the cell surface of SH-SY5Y neuroblastoma cells in a metalloproteinase-dependent manner; however, the mechanism and physiological consequence of NgR1 shedding have not been explored. We now demonstrate that NgR1 is shed from multiple populations of primary neurons. Through a loss-of-function approach, we found that membrane-type matrix metalloproteinase-3 (MT3-MMP) regulates endogenous NgR1 shedding in primary neurons. Neuronal knockdown of MT3-MMP resulted in the accumulation of NgR1 at the cell surface and reduced the accumulation of the NgR1 cleavage fragment in medium conditioned by cortical neurons. Recombinant MT1-, MT2-, MT3-, and MT5-MMPs promoted NgR1 shedding from the surface of primary neurons, and this treatment rendered neurons resistant to myelin-associated inhibitors. Introduction of a cleavage-resistant form of NgR1 reconstitutes the neuronal response to these inhibitors, demonstrating that specific metalloproteinases attenuate neuronal responses to myelin in an NgR1-dependent manner.

New Strategies for the Next Generation of Matrix-Metalloproteinase Inhibitors: Selectively Targeting Membrane-Anchored MMPs with Therapeutic Antibodies

MMP intervention strategies have met with limited clinical success due to severe toxicities. In particular, treatment with broad-spectrum MMP-inhibitors (MMPIs) caused musculoskeletal pain and inflammation. Selectivity may be essential for realizing the clinical potential of MMPIs. Here we review discoveries pinpointing membrane-bound MMPs as mediators of mechanisms underlying cancer and inflammation and as possible therapeutic targets for prevention/treatment of these diseases. We discuss strategies to target these therapeutic proteases using highly selective inhibitory agents (i.e., human blocking antibodies) against individual membrane-bound MMPs.

Differential gene expression profiling of metalloproteinases and their inhibitors: a comparison between bovine intervertebral disc nucleus pulposus cells and articular chondrocytes

STUDY DESIGN

A comparative in vitro metalloproteinases and their inhibitors gene expression profile.

OBJECTIVE

To obtain a complete expression profile of matrix metalloproteinases (MMPs), family of proteases with a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS), and tissue inhibitors of metalloproteinases (TIMPs) in bovine adult nucleus pulposus (NP) cells and to compare this profile with the expression profile obtained from bovine adult articular chondrocytes cultured under identical conditions.

SUMMARY OF BACKGROUND DATA

The cells of the NP resemble articular chondrocytes morphologically but produce a matrix which, though consisting of similar components, has very different biomechanical properties. No specific markers for NP cells have yet been identified; they can be distinguished from chondrocytes only by differences in gene expression. Here we compare profiles of gene expression of metalloproteinases and their inhibitors between NP cells and chondrocytes to improve understanding of the differences between these cell types.

METHODS

NP cells and articular chondrocytes were harvested respectively from bovine caudal discs and the articular cartilage of metacarpal-phalangeal joints of 18- to 24-month-old steers. These cells were cultured under identical conditions for 96 hours in alginate beads. Expression levels of MMPs, ADAMTSs, and TIMPs were detected by real-time RT-PCR.

RESULTS

Gene profiling demonstrated distinct differences between levels of MMPs, ADAMTSs, and TIMPs produced by chondrocytes and NP cells. In particular, NP cells expressed considerably more MMP-2 and MMP-14 than chondrocytes, and expression of ADAMTS-1,-2,-17 and TIMP-1 was also higher. However, expression of MMP-1,-3,-7,-8,-10,-11,-13,-16,-19,-20,-21,-23,-24,-28, ADAMTS-4,-5,-6,-14,-18,-19, and TIMP-3 was lower in NP cells than in chondrocytes. Chondrocytes but not NP cells expressed MMP12 and MMP27; this difference is a potential marker for distinguishing between NP cells and chondrocytes.

CONCLUSION

Because culture conditions and animal age were identical, differences in metalloproteinase and inhibitor expression between NP cells and chondrocytes were intrinsic to cell phenotype and not induced by differences in the in situ extracellular environment.

Secreted versus membrane-anchored collagenases: relative roles in fibroblast-dependent collagenolysis and invasion

Fibroblasts degrade type I collagen, the major extracellular protein found in mammals, during events ranging from bulk tissue resorption to invasion through the three-dimensional extracellular matrix. Current evidence suggests that type I collagenolysis is mediated by secreted as well as membrane-anchored members of the matrix metalloproteinase (MMP) gene family. However, the roles played by these multiple and possibly redundant, degradative systems during fibroblast-mediated matrix remodeling is undefined. Herein, we use fibroblasts isolated from Mmp13(-/-), Mmp8(-/-), Mmp2(-/-), Mmp9(-/-), Mmp14(-/-) and Mmp16(-/-) mice to define the functional roles for secreted and membrane-anchored collagenases during collagen-resorptive versus collagen-invasive events. In the presence of a functional plasminogen activator-plasminogen axis, secreted collagenases arm cells with a redundant collagenolytic potential that allows fibroblasts harboring single deficiencies for either MMP-13, MMP-8, MMP-2, or MMP-9 to continue to degrade collagen comparably to wild-type fibroblasts. Likewise, Mmp14(-/-) or Mmp16(-/-) fibroblasts retain near-normal collagenolytic activity in the presence of plasminogen via the mobilization of secreted collagenases, but only Mmp14 (MT1-MMP) plays a required role in the collagenolytic processes that support fibroblast invasive activity. Furthermore, by artificially tethering a secreted collagenase to the surface of Mmp14(-/-) fibroblasts, we demonstrate that localized pericellular collagenolytic activity differentiates the collagen-invasive phenotype from bulk collagen degradation. Hence, whereas secreted collagenases arm fibroblasts with potent matrix-resorptive activity, only MT1-MMP confers the focal collagenolytic activity necessary for supporting the tissue-invasive phenotype.

Collagen fibril growth during chicken tendon development: matrix metalloproteinase-2 and its activation

The role of matrix metalloproteinases (MMPs) in collagen fibrillogenesis during development has been studied in the well-characterized chicken metatarsal tendon. Collagen fibrils are initially assembled as intermediates, and the mature fibrils assemble by linear and lateral growth from these intermediates. We hypothesize that this involves the turnover of fibril-associated molecules mediated by the expression and activation of matrix metalloproteinase-2 (MMP-2). We demonstrate changes in the ratio of full-length to truncated MMP-2 during tendon development, consistent with enzyme activation. The level of full-length proMMP-2 remains relatively unchanged, although the truncated form of MMP-2 is highest prior to and during fibril growth. Membrane-type matrix metalloproteinase-3 (MT3-MMP, MMP-16) is fibroblast-associated and involved in the regulation of MMP-2 and in direct matrix turnover. The ratio of full-length proMT3-MMP/truncated (active) MT3-MMP has a pattern similar to that of full-length proMMP-2/truncated (active) MMP-2 during tendon development. Regulation of proMMP-2 activation involves complex formation with active MT3-MMP and TIMP-2. The constantly low TIMP-2 expression seen in tendon development is consistent with this role. Isolation of collagen fibrils from pre-fibril growth tendons (14 day) in the presence of activated MMP-2 is associated with premature fibril growth observed as increased fibril diameters compared with controls. These data implicate MMP-2/MT3-MMP in the initiation and progression of fibril growth, matrix assembly, and tendon development. This may involve the turnover of fibril-associated molecules involved in regulating linear and lateral growth, such as small leucine-rich proteoglycans and fibril-associated collagens. Activation of proMMP-2 dependent on MT3-MMP would allow the focal control of turnover.

Purification of matrix metalloproteinases by column chromatography

Matrix metalloproteinases (MMPs) are zinc endopeptidases composed of 23 members in humans, which belong to a subfamily of the metzincin superfamily. They play important roles in many pathophysiological events including development, organogenesis, angiogenesis, tissue remodeling and destruction, and cancer cell proliferation and progression by degradation of extracellular matrix (ECM) and non-ECM proteins and interaction with various molecules. Here, we present standard protocols for purification of native proMMPs (proMMP-1, -2, -3, -7, -9 and -10) and recombinant MT1-MMP (MMP-14) using conventional column chromatography. Purification steps comprise the initial common step [diethylaminoethyl (DEAE)-cellulose, Green A Dyematrex gel and gelatin-Sepharose columns], the second step for removal of nontarget proMMPs by immunoaffinity columns (anti-MMP-1 and/or anti-MMP-3 IgG-Sepharose columns) and the final step for further purification (IgG-Sepharose, DEAE-cellulose, Zn2+-chelate-Sepharose and/or gel filtration columns). Purified proMMPs and MMP are functionally active and suitable for biochemical analyses. The basic protocol for the purification from culture media takes approximately 7-10 d.

MT3-MMP (MMP-16) is downregulated by in vitro cytokine stimulation of cartilage, but unaltered in naturally occurring equine osteoarthritis and osteochondrosis

Matrix degradation by metalloproteinases is considered a key feature in the loss of articular cartilage seen in many joint diseases. Membrane-type matrix metalloproteinase-3 (MT3-MMP) expression is elevated in human cartilage in end-stage osteoarthritis. We investigated whether MT3-MMP is similarly regulated in cartilage in two naturally occurring arthropathies in vivo and whether proinflammatory cytokines regulate its expression in vitro. MT3-MMP expression was evaluated in cartilage from horses with osteoarthritis and osteochondrosis and compared with age- and site-matched normal cartilage. MT3-MMP also was measured in normal cartilage stimulated with proinflammatory cytokines. MT3-MMP expression was not significantly altered in either osteoarthritis or osteochondrosis cartilage. However, gene expression was significantly downregulated by the addition of recombinant human interleukin-1beta, oncostatin M, or tumor necrosis factor-alpha to normal cartilage explants. The results suggest that MT3-MMP may not have a role in matrix destruction in equine cartilage diseases. Further work is required to characterize its regulation and function.

Membrane-type MMPs enable extracellular matrix permissiveness and mesenchymal cell proliferation during embryogenesis

Peri-cellular remodeling of mesenchymal extracellular matrices is considered a prerequisite for cell proliferation, motility and development. Here we demonstrate that membrane-type 3 MMP, MT3-MMP, is expressed in mesenchymal tissues of the skeleton and in peri-skeletal soft connective tissue. Consistent with this localization, MT3-MMP-deficient mice display growth inhibition tied to a decreased viability of mesenchymal cells in skeletal tissues. We document that MT3-MMP works as a major collagenolytic enzyme, enabling cartilage and bone cells to cleave high-density fibrillar collagen and modulate their resident matrix to make it permissive for proliferation and migration. Collectively, these data uncover a novel extracellular matrix remodeling mechanism required for proper function of mesenchymal cells. The physiological significance of MT3-MMP is highlighted in mice double deficient for MT1-MMP and MT3-MMP. Double deficiency transcends the combined effects of the individual single deficiencies and leads to severe embryonic defects in palatogenesis and bone formation incompatible with life. These defects are directly tied to loss of indispensable collagenolytic activities required in collagen-rich mesenchymal tissues for extracellular matrix remodeling and cell proliferation during embryogenesis.

Constraining specificity in the N-domain of tissue inhibitor of metalloproteinases-1; gelatinase-selective inhibitors

The tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of the matrix metalloproteinases (MMPs). Since unregulated MMP activities are linked to arthritis, cancer, and atherosclerosis, TIMP variants that are selective inhibitors of disease-related MMPs have potential therapeutic value. The structures of TIMP/MMP complexes reveal that most interactions with the MMP involve the N-terminal pentapeptide of TIMP and the C-D beta-strand connector which occupy the primed and unprimed regions of the active site. The loop between beta-strands A and B forms a secondary interaction site for some MMPs, ranging from multiple contacts in the TIMP-2/membrane type-1 (MT1)-MMP complex to none in the TIMP-1/MMP-1 complex. TIMP-1 and its inhibitory domain, N-TIMP-1, are weak inhibitors of MT1-MMP; inhibition is not improved by grafting the longer AB loop from TIMP-2 into N-TIMP-1, but this change impairs binding to MMP-3 and MMP-7. Mutational studies with N-TIMP-1 suggest that its weak inhibition of MT1-MMP, as compared to other N-TIMPs, arises from multiple (>3) sequence differences in the interaction site. Substitutions for Thr2 of N-TIMP-1 strongly influence MMP selectivity; Arg and Gly, that generally reduce MMP affinity, have less effect on binding to MMP-9. When the Arg mutation is added to the N-TIMP-1(AB2) mutant, it produces a gelatinase-specific inhibitor with Ki values of 2.8 and 0.4 nM for MMP-2 and -9, respectively. Interestingly, the Gly mutant has a Ki of 2.1 nM for MMP-9 and >40 muM for MMP-2, indicating that engineered TIMPs can discriminate between MMPs in the same subfamily.

Cell surface chondroitin sulfate glycosaminoglycan in melanoma: role in the activation of pro-MMP-2 (pro-gelatinase A)

We previously reported that CS (chondroitin sulfate) GAG (glycosaminoglycan), expressed on MCSP (melanoma-specific CS proteoglycan), is important for regulating MT3-MMP [membrane-type 3 MMP (matrix metalloproteinase)]-mediated human melanoma invasion and gelatinolytic activity in vitro. In the present study, we sought to determine if CS can directly enhance MT3-MMP-mediated activation of pro-MMP-2. Co-immunoprecipitation studies suggest that MCSP forms a complex with MT3-MMP and MMP-2 on melanoma cell surface. When melanoma cells were treated with betaDX (p-nitro-beta-D-xylopyranoside) to inhibit coupling of CS on the core protein, both active form and proform of MMP-2 were no longer co-immunoprecipitated with either MCSP or MT3-MMP, suggesting a model in which CS directly binds to MMP-2 and presents the gelatinase to MT3-MMP to be activated. By using recombinant proteins, we determined that MT3-MMP directly activates pro-MMP-2 and that this activation requires the interaction of the C-terminal domain of pro-MMP-2 with MT3-MMP. Activation of pro-MMP-2 by suboptimal concentrations of MT3-MMP is also significantly enhanced in the presence of excess C4S (chondroitin 4-sulfate), whereas C6S (chondroitin 6-sulfate) or low-molecular-mass hyaluronan was ineffective. Affinity chromatography studies using CS isolated from aggrecan indicate that the catalytic domain of MT3-MMP and the C-terminal domain of MMP-2 directly bind to the GAG. Thus the direct binding of pro-MMP-2 with CS through the C-domain would present the catalytic domain of pro-MMP-2 to MT3-MMP, which facilitates the generation of the active form of MMP-2. These results suggest that C4S, which is expressed on tumour cell surface, can function to bind to pro-MMP-2 and facilitate its activation by MT3-MMP-expressing tumour cells to enhance invasion and metastasis.

Osteoprotegerin Reduces the Serum Level of Receptor Activator of NF-κB Ligand Derived from Osteoblasts

Osteoprotegerin (OPG) is a decoy receptor for receptor activator of NF-kappaB ligand (RANKL). We previously reported that OPG deficiency elevated the circulating level of RANKL in mice. Using OPG(-/-) mice, we investigated whether OPG is involved in the shedding of RANKL by cells expressing RANKL. Osteoblasts and activated T cells in culture released a large amount of RANKL in the absence of OPG. OPG or a soluble form of receptor activator of NF-kappaB (the receptor of RANKL) suppressed the release of RANKL from those cells. OPG- and T cell-double-deficient mice showed an elevated serum RANKL level equivalent to that of OPG(-/-) mice, indicating that circulating RANKL is mainly derived from bone. The serum level of RANKL in OPG(-/-) mice was increased by ovariectomy or administration of 1alpha,25-dihydroxyvitamin D(3). Expression of RANKL mRNA in bone, but not thymus or spleen, was increased in wild-type and OPG(-/-) mice by 1alpha,25-dihydroxyvitamin D(3). These results suggest that OPG suppresses the shedding of RANKL from osteoblasts and that the serum RANKL in OPG(-/-) mice exactly reflects the state of bone resorption.

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

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.

Cleavage of Amyloid-β Precursor Protein (APP) by Membrane-Type Matrix Metalloproteinases

Amyloid-beta precursor protein (APP) was identified on expression cloning from a human placenta cDNA library as a gene product that modulates the activity of membrane-type matrix metalloproteinase-1 (MT1-MMP). Co-expression of MT1-MMP with APP in HEK293T cells induced cleavage and shedding of the APP ectodomain when co-expressed with APP adaptor protein Fe65. Among the MT-MMPs tested, MT3-MMP and MT5-MMP also caused efficient APP shedding. The recombinant APP protein was cleaved by MT3-MMP in vitro at the A463-M464, N579-M580, H622-S623, and H685-Q686 peptide bonds, which included a cleavage site within the amyloid beta peptide region known to produce a C-terminal fragment. The Swedish-type mutant of APP, which produces a high level of amyloid beta peptide, was more effectively cleaved by MT3-MMP than wild-type APP in both the presence and absence of Fe65; however, amyloid beta peptide production was not affected by MT3-MMP expression. Expression of MT3-MMP enhanced Fe65-dependent transactivation by APP fused to the Gal4 DNA-binding and transactivation domains. These results suggest that MT1-MMP, MT3-MMP and MT5-MMP should play an important role in the regulation of APP functions in tissues including the central nervous system.

MT1-matrix metalloproteinase directs arterial wall invasion and neointima formation by vascular smooth muscle cells

During pathologic vessel remodeling, vascular smooth muscle cells (VSMCs) embedded within the collagen-rich matrix of the artery wall mobilize uncharacterized proteolytic systems to infiltrate the subendothelial space and generate neointimal lesions. Although the VSMC-derived serine proteinases, plasminogen activator and plasminogen, the cysteine proteinases, cathepsins L, S, and K, and the matrix metalloproteinases MMP-2 and MMP-9 have each been linked to pathologic matrix-remodeling states in vitro and in vivo, the role that these or other proteinases play in allowing VSMCs to negotiate the three-dimensional (3-D) cross-linked extracellular matrix of the arterial wall remains undefined. Herein, we demonstrate that VSMCs proteolytically remodel and invade collagenous barriers independently of plasmin, cathepsins L, S, or K, MMP-2, or MMP-9. Instead, we identify the membrane-anchored matrix metalloproteinase, MT1-MMP, as the key pericellular collagenolysin that controls the ability of VSMCs to degrade and infiltrate 3-D barriers of interstitial collagen, including the arterial wall. Furthermore, genetic deletion of the proteinase affords mice with a protected status against neointimal hyperplasia and lumen narrowing in vivo. These studies suggest that therapeutic interventions designed to target MT1-MMP could prove beneficial in a range of human vascular disease states associated with the destructive remodeling of the vessel wall extracellular matrix.

Metalloendoprotease cleavage triggers gelsolin amyloidogenesis

Amyloid diseases like Alzheimer's disease and familial amyloidosis of Finnish type (FAF) stem from endoproteolytic cleavage of a precursor protein to generate amyloidogenic peptides that accumulate as amyloid deposits in a tissue-specific manner. FAF patients deposit both 8 and 5 kDa peptides derived from mutant (D187Y/N) plasma gelsolin in the extracellular matrix (ECM). The first of two aberrant sequential proteolytic events is executed by furin to yield a 68 kDa (C68) secreted fragment. We now identify the metalloprotease MT1-matrix metalloprotease (MMP), an integral membrane protein active in the ECM, as a protease that processes C68 to the amyloidogenic peptides. We further demonstrate that ECM components are capable of accelerating gelsolin amyloidogenesis. Proteolysis by MT1-MMP-like proteases proximal to the unique chemical environment of the ECM offers an explanation for the tissue-specific deposition observed in FAF and provides critical insight into new therapeutic strategies.

Temporospatial expression of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in mouse antigen-induced arthritis

Several lines of evidence speak for an important role of matrix metalloproteinases (MMPs) in the development of progressive joint destruction. To better understand the role of MMPs and their tissue inhibitors (TIMPs) in this process, we have used the antigen-induced arthritis model to study the temporospatial expression of several MMPs and TIMPs during the progression of arthritis. Arthritis was induced by a single intra-articular injection of methylated bovine serum albumin (mBSA) into one or both knee joints of adult mice previously immunised against mBSA. Samples were collected at 3, 7, 21 and 42 days after induction of arthritis for histology and RNA extraction, and analysed by Northern hybridisation, histochemistry and immunohistochemistry for production of several MMPs and TIMPs -1, -2 and -3. A systematic analysis of MMP and TIMP mRNA levels in mouse knee joints demonstrated a general upregulation of both MMPs and TIMPs during progression of arthritis. Upregulation of MMP-9, -13 and -14 coincided with the advancement of cartilage degeneration, but the expression patterns of MMP-9 and -13 also followed the course of synovial inflammation. TIMPs were steadily upregulated throughout the examination period. Immunohistochemical localisation of MMPs and TIMPs suggested the synovium to be the major source of MMP and TIMP production in arthritis, although articular cartilage chondrocytes also showed an increased production of both MMPs and TIMPs.

Membrane type-matrix metalloproteinases and tumor progression

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that process growth factors, growth factor binding proteins, cell surface proteins, degrade extracellular matrix (ECM) components and thereby play a central role in tissue remodeling and tumor progression. Membrane-type matrix metalloproteinases (MT-MMPs) are a recently discovered subgroup of intrinsic plasma membrane proteins. Their functions have been extended from pericellular proteolysis and control of cell migration to cell signaling, control of cell proliferation and regulation of multiple stages of tumor progression including growth and angiogenesis. This review sheds light on the new functions of MT-MMPs and their inhibitors in tumor development and angiogenesis, and presents recent investigations that document their influence on various cell functions.

Lack of Telopeptides in Fibrillar Collagen I Promotes the Invasion of a Metastatic Breast Tumor Cell Line

Defective fibrillar collagen polymerization in primary tumors has been correlated with increased metastasis. However, it is unclear how collagen organization influences tumor invasion. In this study, we show that collagen I polymerized without telopeptides (the flanking regions of collagen molecules) can differentially affect the three-dimensional migration of mammary carcinoma cells. MDA-MB-231 cells capable of proteolytic degradation and mesenchymal motion, invaded telopeptide-intact and telopeptide-free collagen gels to the same extent. In contrast, MDA-MB-435S cells, with typical features of amoeboid cells (poor collagenolytic activity, rounded cell morphology), were 5-fold more invasive in telopeptide-free than telopeptide-intact collagen. A fraction of the MDA-MB-435S cells that invaded telopeptide-intact or telopeptide-free collagen had a rounded morphology; however, in telopeptide-free collagen, a significant fraction of the cells switched from a rounded to elongated morphology (protrusion formation). The dynamic changes in cellular shape facilitated MDA-MB-435S locomotion through the narrow interfiber gaps, which were smaller than cell diameters. Based on the spherical morphology of MDA-MB-435S cells, we tested if the changes in cell shape and invasion were related to RhoA-ROCK activity; GTP-bound RhoA was measured in pull-down assays. RhoA activity was 1.8-fold higher for MDA-MB-435S cells seeded on telopeptide-free than telopeptide-intact collagen. Y27632 inhibition of ROCK, a Rho effector, significantly reduced the changes in cellular morphodynamics and the invasion of MDA-MB-435S cells but did not alter the invasion of MDA-MB-231 cells. Thus, the higher RhoA activity of MDA-MB-435S cells in telopeptide-free collagen enhances the changes in cellular morphodynamics associated with motility and invasion.

Development of In Situ Zymography to Localize Active Matrix Metalloproteinase-7 (Matrilysin-1)

Matrix metalloproteinase-7 (MMP-7) is upregulated during carcinogenesis and its expression correlates with metastasis of human endometrial and gastrointestinal carcinomas. In the present study, we have developed a new method to localize the activity of MMP-7 within tissues. Polyethylene terephthalate films were uniformly coated with crosslinked carboxymethylated transferrin (CCm-Tf) as a substrate and incubated with frozen tissue sections mounted on the films. CCm-Tf on the films was degraded selectively by MMP-7, but showed little or no susceptibility to MMP-1, -2, -3, -9, or -13; MT1-MMP; MT3-MMP; or ADAMTS4. Although some serine proteinases such as elastase also digested CCm-Tf, CCm-Tf films impregnated with serine proteinase inhibitors prevented the digestion. When frozen sections of human endometrial carcinoma and lung carcinoma tissues were incubated on CCm-Tf films or those treated with proteinase inhibitors, the activity was detected in the carcinoma cell nests, where MMP-7 was immunolocalized. The present in situ zymography using CCm-Tf may be a useful method to analyze the functions of MMP-7 in pathophysiological conditions.

Dual role of matrix metalloproteinases (matrixins) in intimal thickening and atherosclerotic plaque rupture

Intimal thickening, the accumulation of cells and extracellular matrix within the inner vessel wall, is a physiological response to mechanical injury, increased wall stress, or chemical insult (e.g., atherosclerosis). If excessive, it can lead to the obstruction of blood flow and tissue ischemia. Together with expansive or constrictive remodeling, the extent of intimal expansion determines final lumen size and vessel wall thickness. Plaque rupture represents a failure of intimal remodeling, where the fibrous cap overlying an atheromatous core of lipid undergoes catastrophic mechanical breakdown. Plaque rupture promotes coronary thrombosis and myocardial infarction, the most prevalent cause of premature death in advanced societies. The matrix metalloproteinases (MMPs) can act together to degrade the major components of the vascular extracellular matrix. All cells present in the normal and diseased blood vessel wall upregulate and activate MMPs in a multistep fashion driven in part by soluble cytokines and cell-cell interactions. Activation of MMP proforms requires other MMPs or other classes of protease. MMP activation contributes to intimal growth and vessel wall remodeling in response to injury, most notably by promoting migration of vascular smooth muscle cells. A broader spectrum and/or higher level of MMP activation, especially associated with inflammation, could contribute to pathological matrix destruction and plaque rupture. Inhibiting the activity of specific MMPs or preventing their upregulation could ameliorate intimal thickening and prevent myocardial infarction.

The Hemopexin Domain of Membrane-type Matrix Metalloproteinase-1 (MT1-MMP) Is Not Required for Its Activation of proMMP2 on Cell Surface but Is Essential for MT1-MMP-mediated Invasion in Three-dimensional Type I Collagen

Membrane-type matrix metalloproteinase-1 (MT1-MMP) plays a key role in tumor invasion and metastasis by degrading the extracellular matrix and activating proMMP2. Here we show that the conserved hemopexin domain is required for MT1-MMP-mediated invasion and growth in three-dimensional type I collagen matrix but not proMMP2 activation. Deletion of the hemopexin domains in MT1-, MT2-, MT3-, MT5-, and MT6-MMP does not impair their abilities to activate proMMP2. In fact, hemopexin-less MT5- and MT6-MMP activate proMMP2 better than their wild type counterparts. On the other hand, hemopexin-less MT1-MMP fails to promote cell invasion into type I collagen but retains the capacity to enhance the growth of Madin-Darby canine kidney cells as cysts in three-dimensional collagen matrix. Moreover, the hemopexin domain is also required for MT1-MMP-mediated invasion/scattering of MCF-7 cells in three-dimensional collagen matrix. Because growth and invasion in a three-dimensional model may correlate with tumor invasiveness in vivo, our data suggest that the hemopexin domains of MT-MMPs should be targeted for the development of anti-cancer therapies by employing screening assays developed for three-dimensional models rather than their enzymatic activity toward proMMP2.

Differences between scirrhous and non-scirrhous human gastric carcinomas from the aspect of proMMP-2 activation regulated by TIMP-3

Gastric carcinomas can be classified into scirrhous carcinomas (SC), i.e. 'linitis plastica' or Borrmann 4 gastric cancer, and non-scirrhous carcinomas (NSC). SC are characterized by diffuse invasive growth patterns with marked fibrosis, frequent peritoneal dissemination and lymph-node metastases and poor prognosis, while NSC show medullary growth patterns and common hematogenous metastases. To study the differences in local expression levels of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) between SC and NSC, we examined the expression of MMPs and TIMPs in human gastric carcinoma tissues by several methods including sandwich-enzyme immunoassay systems, gelatin zymography, reverse transcriptase-polymerase chain reaction (RT-PCR), real-time quantitative PCR, immunoblotting, immunohistochemistry and in situ zymography. Of the seven MMPs and two TIMPs tested, only proMMP-2 levels were remarkably higher in SC than in NSC (P < 0.01), and proMMP-2 activation ratio was significantly lower in SC than in NSC (P < 0.05). TIMP-3 mRNA levels were remarkably about 2-fold higher in SC than in NSC tissues (P < 0.01). TIMP-3 production in SC was confirmed by immunoblotting and TIMP-3 was immunolocalized to stromal fibroblasts in SC. TIMP-3 mRNA levels inversely correlated with proMMP-2 activation ratios, although the expression levels of MT1-MMP and MT2-MMP were not different in SC and NSC. By in situ zymography, gelatinolytic activity appeared to be weaker in SC than in NSC. All these data suggest that proMMP-2 activation is down-regulated by TIMP-3 expressed in scirrhous gastric carcinomas. Our findings may explain the differences in clinical behaviors of SC and NSC.

Cleavage of lumican by membrane-type matrix metalloproteinase-1 abrogates this proteoglycan-mediated suppression of tumor cell colony formation in soft agar

The small leucine-rich proteoglycan lumican was identified from a human placenta cDNA library by the expression cloning method as a gene product that interacts with membrane-type matrix metalloproteinase-1 (MT1-MMP). Coexpression of MT1-MMP with lumican in HEK293T cells reduced the concentration of lumican secreted into culture medium, and this reduction was abolished by addition of the MMP inhibitor BB94. Lumican protein from bovine cornea and recombinant lumican core protein fused to glutathione S-transferase was shown to be cleaved at multiple sites by recombinant MT1-MMP. Transient expression of lumican in HEK293 cells induced expression of tumor suppressor gene product p21/Waf-1, which was abrogated by the coexpression of MT1-MMP concomitant with a reduction in lumican concentration in culture medium. Stable expression of lumican in HeLa cells induced expression of p21 and reduction of colony formation in soft agar, which were both abolished by the expression of MT1-MMP. HT1080 fibrosarcoma cells stably transfected with the lumican cDNA (HT1080/Lum), which express endogenous MT1-MMP, secreted moderate levels of lumican; however, treatment of HT1080/Lum cells with BB94 resulted in accumulation of lumican in culture medium. The expression levels of p21 in HT1080/Lum were proportional to the concentration of secreted lumican and showed reverse corelation with colony formation in soft agar. These results suggest that MT1-MMP abrogates lumican-mediated suppression of tumor cell colony formation in soft agar by degrading this proteoglycan, which down-regulates it through the induction of p21.

Interstitial collagenase is a Brownian ratchet driven by proteolysis of collagen

We show that activated collagenase (MMP-1) moves processively on the collagen fibril. The mechanism of movement is a biased diffusion with the bias component dependent on the proteolysis of its substrate, not adenosine triphosphate (ATP) hydrolysis. Inactivation of the enzyme by a single amino acid residue substitution in the active center eliminates the bias without noticeable effect on rate of diffusion. Monte Carlo simulations using a model similar to a "burnt bridge" Brownian ratchet accurately describe our experimental results and previous observations on kinetics of collagen digestion. The biological implications of MMP-1 acting as a molecular ratchet tethered to the cell surface suggest new mechanisms for its role in tissue remodeling and cell-matrix interaction.

Myocardial remodeling in viral heart disease: possible interactions between inflammatory mediators and MMP-TIMP system

Matrix metalloproteinases (MMP), a family of proteases, are involved in the degradation of extracellular matrix proteins and hence in the determination of interstitial architecture. In the heart, MMPs have been found to play a significant role in the development of myocardial remodeling and congestive heart failure. Tissue inhibitors of matrix metalloproteinases (TIMPs) represent a family of proteins which are known to regulate the expression and activity of MMPs. TIMPs are endogenous physiological inhibitors of MMPs and their concomitant downregulation in heart failure suggests the existence of a critical balance between MMPs and TIMPs in the normal maintenance of myocardial interstitial homeostasis. In addition, cytokines regulate expression of both MMPs and TIMPs besides eliciting a direct effect on myocardial cell function. Therefore, myocardial inflammation may also contribute to the development of cardiac remodeling along with other stimuli like mechanical stress and humoral factors. Viral myocarditis, a predisposing factor for dilated cardiomyopathy, is a condition in which extent of intramyocardial inflammation is thought to determine the progression of disease. Inflammatory events in the heart following viral infection are speculated to be responsible for the transition of myocarditis to dilated cardiomyopathy. In viral myocarditis and other inflammatory heart diseases, the inflammatory cells and their battery of cytokines may also alter the myocardial MMP-TIMP system and eventually lead to dilation of the heart and ventricular dysfunction. The objective of this review is to present an overall picture of the inflammatory phase in viral myocarditis and discuss the possible interactions between inflammation and myocardial MMP profiles which may lead to the evolution of dilated cardiomyopathy.

Expression of matrix metalloproteinases in feline vaccine site-associated sarcomas

OBJECTIVES

To screen for expression of 9 predominant members of the matrix metalloproteinase (MMP) family, including membrane-type matrix metalloproteinases (MT-MMPs) and tissue inhibitors of metalloproteinases (TIMPs), in primary tumor tissue biopsy specimens of vaccine site-associated sarcomas (VSS) in cats and compare expression profiles of VSS with expression profiles of non-VSS and carcinomas.

SAMPLE POPULATION

31 primary tumor tissue biopsy specimens and 6 nontumor (normal) tissue biopsy specimens.

PROCEDURES

Tissue specimens were obtained from primary tumor biopsy specimens of cats. Primers for reverse transcriptase-polymerase chain reaction assay were designed on the basis of known sequences. Data were analyzed for patterns of expression of MMPs, MT-MMPs, and TIMPs. Differences in expression patterns were evaluated among cats of differing genders, ages, metastasis status, and overall survival durations, and between cats with VSS and cats with non-VSS tumor types.

RESULTS

A total of 31 primary tumor tissue biopsy specimens and 6 nontumor (normal) tissue biopsy specimens were screened for the presence of 6 MMPs and 3 TIMPs. Matrix metalloproteinase and TIMP expression was found in non-VSS, carcinomas, and VSS. No significant differences were found in patterns of expression among tumor types. Metastasis was found to be the only predictive factor for overall survival duration. A significant correlation was found between MMP2 and MT-MMP16 expression and overall duration of survival.

CONCLUSIONS AND CLINICAL RELEVANCE

The identification of MMPs in feline VSS supports an underlying inflammatory pathogenesis for this tumor. Expression of MMP2 and MT-MMP16 were correlated with survival time in our study.

Crystal structure of the catalytic domain of MMP-16/MT3-MMP: characterization of MT-MMP specific features

Membrane-type matrix metalloproteinases (MT-MMPs) have attracted strong attention, because four of them can activate a key player in the tumor scenario, proMMP-2/progelatinase A. In addition to this indirect effect on the cellular environment, these MT-MMPs degrade extracellular matrix proteins, and their overproduction is associated with tumor growth. We have solved the structure of the catalytic domain (cd) of MT3-MMP/MMP-16 in complex with the hydroxamic acid inhibitor batimastat. CdMT3-MMP exhibits a classical MMP-fold with similarity to MT1-MMP. Nevertheless, it also shows unique properties such as a modified MT-specific loop and a closed S1' specificity pocket, which might help to design specific inhibitors. Some MT-MMP-specific features, derived from the crystal structures of MT-1-MMP determined previously and MT3-MMP, and revealed in recent mutagenesis experiments, explain the impaired interaction of the MT-MMPs with TIMP-1. Docking experiments with proMMP-2 show some exposed loops including the MT-loop of cdMT3-MMP involved in the interaction with the proMMP-2 prodomain in the activation encounter complex. This model might help to understand the experimentally proven importance of the MT-loop for the activation of proMMP-2.

Tetrahydroisoquinoline based sulfonamide hydroxamates as potent matrix metalloproteinase inhibitors

The synthesis and MMP inhibitory activity of a series of tetrahydroisoquinoline based sulfonamide hydroxamates are described. In nine MMPs tested, most of the compounds display potent inhibition activity except for MMP-7. Some subtle isozyme selectivity is observed by varying the substituents at the 6- and 7-positions and aromatic ring of arylsulfonyl groups.

Matrix metalloproteinase-13 (MMP-13, collagenase-3) is highly expressed in human tooth pulp

Matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs) participate into extracellular matrix degradation in physiological and pathological conditions. We hypothesized that MMP expression in pulp tissue changes in response to caries attack and investigated the gene expression profiles of MMPs and TIMPs in pulp tissue of sound and carious teeth with cDNA microarray. cDNA microarray demonstrated an extremely high MMP-13 (collagenase-3) mRNA expression in pooled pulp samples of sound and carious teeth, with less pronounced expression of MMP-16 (MT3-MMP) and TIMP-1. Real-time quantitative polymerase chain reaction of individual pulp samples revealed a wide range of the MMP-13 expression level between pulp samples with possible downregulation of MMP-13 expression during caries progression. Western blot and immunohistochemical staining confirmed the presence of MMP-13 with no observable differences between sound and carious teeth pulp tissues. The results reveal that MMP-13 is expressed and synthesized in pulp tissue, an interesting feature considering the very limited expression of MMP-13 in normal adult tissues. Further studies with a larger sample size are needed to clarify the changes in MMP-13 expression during caries progression.

Differential inhibition of membrane type 3 (MT3)-matrix metalloproteinase (MMP) and MT1-MMP by tissue inhibitor of metalloproteinase (TIMP)-2 and TIMP-3 rgulates pro-MMP-2 activation

The membrane type (MT)-matrix metalloproteinases (MMPs) constitute a subgroup of membrane-anchored MMPs that are major mediators of pericellular proteolysis and physiological activators of pro-MMP-2. The MT-MMPs also exhibit differential inhibition by members of the tissue inhibitor of metalloproteinase (TIMP) family. Here we investigated the processing, catalytic activity, and TIMP inhibition of MT3-MMP (MMP-16). Inhibitor profile and mutant enzyme studies indicated that MT3-MMP is regulated on the cell surface by autocatalytic processing and ectodomain shedding. Inhibition kinetic studies showed that TIMP-3 is a high affinity inhibitor of MT3-MMP when compared with MT1-MMP (K(i) = 0.008 nm for MT3-MMP versus K(i) = 0.16 nm for MT1-MMP). In contrast, TIMP-2 is a better inhibitor of MT1-MMP. MT3-MMP requires TIMP-2 to accomplish full pro-MMP-2 activation and this process is enhanced in marimastatpretreated cells, consistent with regulation of active enzyme turnover by synthetic MMP inhibitors. TIMP-3 also enhances the activation of pro-MMP-2 by MT3-MMP but not by MT1-MMP. TIMP-4, in contrast, cannot support pro-MMP-2 activation with either enzyme. Affinity chromatography experiments demonstrated that pro-MMP-2 can assemble trimolecular complexes with a catalytic domain of MT3-MMP and TIMP-2 or TIMP-3 suggesting that pro-MMP-2 activation by MT3-MMP involves ternary complex formation on the cell surface. These results demonstrate that TIMP-3 is a major regulator of MT3-MMP activity and further underscores the unique interactions of TIMPs with MT-MMPs in the control of pericellular proteolysis.

Drosophila TIMP is a potent inhibitor of MMPs and TACE: similarities in structure and function to TIMP-3

The four tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that regulate the activity of matrix metalloproteinases (MMPs) and certain disintegrin and metalloproteinase (ADAM) family proteases in mammals. The protease inhibitory activity is present in the N-terminal domains of TIMPs (N-TIMPs). In this work, the N-terminal inhibitory domain of the only TIMP produced by Drosophila (dN-TIMP) was expressed in Escherichia coli and folded in vitro. The purified recombinant protein is a potent inhibitor of human MMPs, including membrane-type 1-MMP, although it lacks a disulfide bond that is conserved in all other known N-TIMPs. Titration with the catalytic domain of human MMP-3 [MMP-3(DeltaC)] showed that dN-TIMP prepared by this method is correctly folded and fully active. dN-TIMP also inhibits, in vitro, the activity of the only two MMPs of Drosophila, dm1- and dm2-MMPs, indicating that the Drosophila TIMP is an endogenous inhibitor of the Drosophila MMPs. dN-TIMP resembles mammalian N-TIMP-3 in strongly inhibiting human tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17) but is a weak inhibitor of human ADAM10. Models of the structures of dN-TIMP and N-TIMP-3 are strikingly similar in surface charge distribution, which may explain their functional similarity. Although the gene duplication events that led to the evolutionary development of the four mammalian TIMPs might be expected to be associated with functional specialization, Timp-3 appears to have conserved most of the functions of the ancestral TIMP gene.

Cleavage of syndecan-1 by membrane type matrix metalloproteinase-1 stimulates cell migration

The transmembrane heparan sulfate proteoglycan syndecan-1 was identified from a human placenta cDNA library by the expression cloning method as a gene product that interacts with membrane type matrix metalloproteinase-1 (MT1-MMP). Co-expression of MT1-MMP with syndecan-1 in HEK293T cells promoted syndecan-1 shedding, and concentration of cell-associated syndecan-1 was reduced. Treatment of cells with MMP inhibitor BB-94 or tissue inhibitor of MMP (TIMP)-2 but not TIMP-1 interfered with the syndecan-1 shedding promoted by MT1-MMP expression. In contrast, syndecan-1 shedding induced by 12-O-tetradecanoylphorbol-13-acetate treatment was inhibited by BB-94 but not by either TIMP-1 or TIMP-2. Shedding of syndecan-1 was also induced by MT3-MMP but not by other MT-MMPs. Recombinant syndecan-1 core protein was shown to be cleaved by recombinant MT1-MMP or MT3-MMP preferentially at the Gly245-Leu246 peptide bond. HT1080 fibrosarcoma cells stably transfected with the syndecan-1 cDNA (HT1080/SDC), which express endogenous MT1-MMP, spontaneously shed syndecan-1. Migration of HT1080/SDC cells on collagen-coated dishes was significantly slower than that of control HT1080 cells. Treatment of HT1080/SDC cells with BB-94 or TIMP-2 induced accumulation of syndecan-1 on the cell surface, concomitant with further retardation of cell migration. Substitution of Gly245 of syndecan-1 with Leu significantly reduced shedding from HT1080/SDC cells and cell migration. These results suggest that the shedding of syndecan-1 promoted by MT1-MMP through the preferential cleavage of Gly245-Leu246 peptide bond stimulates cell migration.

Cleavage of metastasis suppressor gene product KiSS-1 protein/metastin by matrix metalloproteinases

A human placenta cDNA library was screened by the expression cloning method for gene products that interact with matrix metalloproteinases (MMPs), and we isolated a cDNA whose product formed a stable complex with pro-MMP-2 and pro-MMP-9. The cDNA encoded the metastasis suppressor gene KiSS-1. KiSS-1 protein was shown to form a complex with pro-MMP. KiSS-1 protein is known to be processed to peptide ligand of a G-protein-coupled receptor (hOT7T175) named metastin, and suppresses metastasis of tumors expressing the receptor. Active MMP-2, MMP-9, MT1-MMP, MT3-MMP and MT5-MMP cleaved the Gly118-Leu119 peptide bond of not only full-length KiSS-1 protein but also metastin decapeptide. Metastin decapeptide induced formation of focal adhesion and actin stress fibers in cells expressing the receptor, and digestion of metastin decapeptide by MMP abolished its ligand activity. Migration of HT1080 cells expressing hOT7T175 that harbor a high-level MMP activity was only slightly suppressed by either metastin decapeptide or MMP inhibitor BB-94 alone, but the combination of metastin decapeptide and BB-94 showed a synergistic effect in blocking cell migration. We propose that metastin could be used as an antimetastatic agent in combination with MMP inhibitor, or MMP-resistant forms of metastin could be developed and may also be efficacious.