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ADAMTS: a novel family of extracellular matrix proteases.

ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) is a novel family of extracellular proteases found in both mammals and invertebrates. Members of the family may be distinguished from the ADAM (a disintegrin and metalloprotease) family members based on the multiple copies of thrombospondin 1-like repeats they carry. With at least nine members in mammals alone, the ADAMTS family members are predicted by their structural domains to be extracellular matrix (ECM) proteins with a wide range of activities and functions distinct from members of the ADAM family that are largely anchored on the cell surface. ADAMTS2 is a procollagen N-proteinase, and the mutations of its gene are responsible for Human Ehlers-Danlos syndrome type VII C and bovine dermatosparaxis. ADAMTS4 and ADAMTS5 are aggrecanases implicated in the degradation of cartilage aggrecan in arthritic diseases. Other members of the ADAMTS family have also been implicated in roles during embryonic development and angiogenesis. Current and future studies on this emerging group of ECM proteases may provide important insights into developmental or pathological processes involving ECM remodeling.

ADAM Proteins↗

Brain-enriched hyaluronan binding (BEHAB)/brevican cleavage in a glioma cell line is mediated by a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family member.

Brain-enriched hyaluronan binding (BEHAB)/brevican is a brain-specific extracellular matrix protein containing a cleavage site between Glu(395)-Ser(396), which bears remarkable homology to the "aggrecanase" site in the cartilage proteoglycan aggrecan. Expression of BEHAB/brevican is dramatically increased in human gliomas, notoriously invasive tumors. Recently, we showed that the rat 9L gliosarcoma cell line, which does not express BEHAB/brevican and forms non-invasive tumors when grown as intracranial grafts, can form invasive tumors when transfected with a 5' cDNA fragment of BEHAB/brevican, but not when transfected with the full-length cDNA. In marked contrast, the highly invasive CNS-1 glioma cell line expresses and cleaves BEHAB/brevican protein when grown as an intracranial graft. These results suggest that both synthesis and cleavage of BEHAB/brevican protein may play a role in the invasiveness of gliomas. We report here, using an antibody developed to the neoepitope created by BEHAB/brevican cleavage at the Glu(395)-Ser(396) site, that the CNS-1 cells are able to cleave the protein in vitro. We characterized the CNS-1-derived cleavage activity by assaying its ability to cleave BEHAB/brevican proteoglycan, and determined that the enzyme is a constitutively expressed, secreted activity. Using a variety of protease inhibitors, reverse transcriptase-polymerase chain reaction, and specific antibodies, we determined that this activity is likely to be a member of the ADAMTS family of metalloproteinases, specifically ADAMTS4. These results suggest a novel function for ADAMTS family members in BEHAB/brevican cleavage and glioma and indicate that inhibition of ADAMTS in glioma may provide a novel therapeutic strategy.

ADAM Proteins↗

Analysis of fracture healing by large-scale transcriptional profile identified temporal relationships between metalloproteinase and ADAMTS mRNA expression.

The aim of this study was to validate the use of transcriptional profiling as a means of characterizing the complex interactions of the thousands of genes that are expressed during fracture healing. Standard mid-diaphyseal tibia fractures were generated in C57/B6 murine tibiae and the transcriptional expression of approximately 13,000 genes was assessed. Three time points after fracture were assessed: day 3, representative of the inflammatory phase; day 10, representative of the peak of cartilage formation; and day 21, representative of the period of primary bone formation and coupled remodeling. A self-organizing mapping approach of the data revealed the temporal relationships between the expression of mRNAs for extracellular matrix proteins and the proteases that degrade the proteoglycan and collagenous matrices. A broad group of extracellular matrix protein mRNAs representative of basement membranes, blood vessels and cartilage all showed elevated expression over the first 21 days of fracture healing. The sorting of the data identified an orderly temporal expression of the metalloproteinases and ADAMTS during the progression of fracture healing with (MMP2/MMP14/TIMP2) and ADAMTS4 and 15 preceding the expression of (MMP9/MMP13). Based on their patterns of expression, relative to the known activities of the encoded proteolytic enzymes, our results suggest that the dissolution of cartilage protoeglycans proceeds before the underlying collagenous components of the matrix are removed. The exclusion of several mRNAs that are normally expressed by osteoclasts in the profiles of mRNAs from days 3 and 10 suggests that osteoclastic activity was largely absent during the early periods of cartilage tissue formation and that proteoglycan and specific collagenase activities, precedes or is prerequisite to later osteoclast infiltration into the remodeling tissues.

ADAM Proteins↗

Proteases in brain tumour progression.

Local invasion of tumour cells is characteristic of brain tumour progression. It is associated with increased motility and a potential to hydrolyse macromolecular components of the extracellular matrix. The peptidases that have been most investigated, and are induced during this process, are reviewed: the plasminogen activators (PAs), matrix metalloproteinases (MMPs) and lysosomal cysteine peptidases called cathepsins (Cats). Increased levels of urokinase-type PA (uPA) are observed mainly at the invasive margins of a tumour, whereas the data on the expression of tissue-type PA (tPA) are still controversial. It has been shown that the endogenous inhibitor of PAs, PAI-1, is localised in both tumour and tumour-associated endothelial cells. Among MMPs, the expression of the gelatinases, MMP2 and MMP9, strongly correlates with glioma progression. Membrane bound MT-MMPs, in particular MT1- and MT2-MMP, seem to play a major role in activating MMP-2. Several members of the ADAMTS family have also been detected in brain tumours, the most relevant being ADAMTS4, due to its cleavage of CNS specific proteins. Lysosomal cathepsin B is highly expressed in malignant glial cells and in endothelial cells of vascularised glioblastomas and is a predictor of a shorter survival. In addition to invasion, cathepsin L may play a role in decreased susceptibility of anaplastic glioma cells to apoptosis. Finally, cathepsin B was proposed as a marker for malignancy in the more aggressive type of meningiomas. Each of these peptidases may act alone, or in concert with the others, to support malignant behaviour of brain tumour cells; the development of new inhibitors of invasion, therefore, should contribute to the control of local spread of a tumour.

Brain Neoplasms↗

Histone deacetylase inhibitors modulate metalloproteinase gene expression in chondrocytes and block cartilage resorption.

Cartilage destruction in the arthritides is thought to be mediated by two main enzyme families: the matrix metalloproteinases (MMPs) are responsible for cartilage collagen breakdown, and enzymes from the ADAMTS (a disintegrin and metalloproteinase domain with thrombospondin motifs) family mediate cartilage aggrecan loss. Many genes subject to transcriptional control are regulated, at least in part, by modifications to chromatin, including acetylation of histones. The aim of this study was to examine the impact of histone deacetylase (HDAC) inhibitors on the expression of metalloproteinase genes in chondrocytes and to explore the potential of these inhibitors as chondroprotective agents. The effects of HDAC inhibitors on cartilage degradation were assessed using a bovine nasal cartilage explant assay. The expression and activity of metalloproteinases was measured using real-time RT-PCR, western blot, gelatin zymography, and collagenase activity assays using both SW1353 chondrosarcoma cells and primary human chondrocytes. The HDAC inhibitors trichostatin A and sodium butyrate potently inhibit cartilage degradation in an explant assay. These compounds decrease the level of collagenolytic enzymes in explant-conditioned culture medium and also the activation of these enzymes. In cell culture, these effects are explained by the ability of HDAC inhibitors to block the induction of key MMPs (e.g. MMP-1 and MMP-13) by proinflammatory cytokines at both the mRNA and protein levels. The induction of aggrecan-degrading enzymes (e.g. ADAMTS4, ADAMTS5, and ADAMTS9) is also inhibited at the mRNA level. HDAC inhibitors may therefore be novel chondroprotective therapeutic agents in arthritis by virtue of their ability to inhibit the expression of destructive metalloproteinases by chondrocytes.

Animals↗

ADAMTS-9 is synergistically induced by interleukin-1beta and tumor necrosis factor alpha in OUMS-27 chondrosarcoma cells and in human chondrocytes.

OBJECTIVE: To compare induction of the aggrecanases (ADAMTS-1, ADAMTS-4, ADAMTS-5, ADAMTS-8, ADAMTS-9, and ADAMTS-15) by interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) in chondrocyte-like OUMS-27 cells and human chondrocytes, and to determine the mechanism of induction of the most responsive aggrecanase gene. METHODS: OUMS-27 cells were stimulated for different periods of time and with various concentrations of IL-1beta and/or TNFalpha. Human chondrocytes obtained from osteoarthritic joints and human skin fibroblasts were also stimulated with IL-1beta and/or TNFalpha. Total RNA was extracted, reverse transcribed, and analyzed by quantitative real-time polymerase chain reaction and Northern blotting. ADAMTS-9 protein was examined by Western blotting, and the role of the MAPK signaling pathway for ADAMTS9 induction in IL-1beta-stimulated OUMS-27 cells was investigated. RESULTS: IL-1beta increased messenger RNA (mRNA) levels of ADAMTS4, ADAMTS5, and ADAMTS9 but not ADAMTS1 and ADAMTS8. The fold increase for ADAMTS9 mRNA was greater than that for mRNA of the other aggrecanase genes. The increase of ADAMTS9 mRNA by IL-1beta stimulation was greater in chondrocytes than in fibroblasts. The combination of IL-1beta and TNFalpha had a synergistic effect, resulting in a considerable elevation in the level of ADAMTS9 mRNA. ADAMTS-9 protein was also induced in IL-1beta-stimulated OUMS-27 cells. The MAPK inhibitors SB203580 and PD98059 decreased ADAMTS9 up-regulation in OUMS-27 cells. CONCLUSION: ADAMTS9 is an IL-1beta- and TNFalpha-inducible gene that appears to be more responsive to these proinflammatory cytokines than are other aggrecanase genes. Furthermore, these cytokines had a synergistic effect on ADAMTS9. Together with the known ability of ADAMTS-9 to proteolytically degrade aggrecan and its potential to cleave other cartilage molecules, the data suggest that ADAMTS-9 may have a pathologic role in arthritis.

ADAM Proteins↗

Expression of versican and ADAMTS during rat tooth eruption.

A disintegrin and metalloprotease with thrombospondin type 1 motifs (ADAMTS) is a family of extracellular proteases and implicated in cleaving proteoglycans, such as aggrecan, versican and brevican. No information is available about expression or localization of these ADAMTSs in teeth. Versican is a large chondroitin sulfate proteoglycan that is present in a variety of connective tissue including dental pulp, dentin, cementum and periodontal ligaments. The present study was designed to investigate expression of ADAMTSs and versican during rat tooth eruption. Rat maxillary first molars in weeks 1, 2, 3, 4 and 6 were examined. The mRNA expression of ADAMTS1, ADAMTS4, ADAMTS5 and versican was localized using in situ hybridization. ADAMTS1, ADAMTS4, ADAMTS5 and versican were expressed in dental pulp cells, odontoblasts, cementoblasts, cementocytes, periodontal ligament cells, osteoblasts and osteocytes. The temporal and spatial expression pattern in these cellular phenotypes was comparable among ADAMTSs and versican. The present study suggests that dental pulp cells, odontoblasts, cementoblasts, cementocytes, periodontal ligament cells, osteoblasts and osteocytes may be involved in both production and degradation of versican with secreting ADAMTS1, ADAMTS4 and ADAMTS5.

ADAM Proteins↗

Immortalized cell lines from mouse xiphisternum preserve chondrocyte phenotype.

Chondrocytes are unique to cartilage and the study of these cells in vitro is important for advancing our understanding of the role of these cells in normal homeostasis and disease including osteoarthritis (OA). As there are limitations to the culture of primary chondrocytes, cell lines have been developed to overcome some of these obstacles. In this study, we developed a procedure to immortalize and characterize chondrocyte cell lines from mouse xiphisternum. The cells displayed a polygonal to fibroblastic morphology in monolayer culture. Gene expression studies using quantitative PCR showed that the cell lines responded to bone morphogenetic protein 2 (BMP-2) by increased expression of matrix molecules, aggrecan, and type II collagen together with transcriptional factor, Sox9. Stimulation by IL-1 results in the increased expression of catabolic effectors including MMP-13, nitric oxide synthase, ADAMTS4, and ADAMTS5. Cells cultured in alginate responded to BMP-2 by increased synthesis of proteoglycan (PG), a major matrix molecule of cartilage. IL-1 treatment of cells in alginate results in increased release of PG into the conditioned media. Further analysis of the media showed the presence of Aggrecanase-cleaved aggrecan fragments, a signature of matrix degradation. These results show that the xiphisternum chondrocyte cell lines preserve their chondrocyte phenotype cultured in either monolayer or 3-dimensional alginate bead culture systems. In summary, this study describes the establishment of chondrocyte cell lines from the mouse xiphisternum that may be useful as a surrogate model system to understand chondrocyte biology and to shed light on the underlying mechanism of pathogenesis in OA.

Aggrecans↗

Cloning and characterization of ADAMTS11, an aggrecanase from the ADAMTS family.

Aggrecan is responsible for the mechanical properties of cartilage. One of the earliest changes observed in arthritis is the depletion of cartilage aggrecan due to increased proteolytic cleavage within the interglobular domain. Two major sites of cleavage have been identified in this region at Asn(341)-Phe(342) and Glu(373)-Ala(374). While several matrix metalloproteinases have been shown to cleave at Asn(341)-Phe(342), an as yet unidentified protein termed "aggrecanase" is responsible for cleavage at Glu(373)-Ala(374) and is hypothesized to play a pivotal role in cartilage damage. We have identified and cloned a novel disintegrin metalloproteinase with thrombospondin motifs that possesses aggrecanase activity, ADAMTS11 (aggrecanase-2), which has extensive homology to ADAMTS4 (aggrecanase-1) and the inflammation-associated gene ADAMTS1. ADAMTS11 possesses a number of conserved domains that have been shown to play a role in integrin binding, cell-cell interactions, and extracellular matrix binding. We have expressed recombinant human ADAMTS11 in insect cells and shown that it cleaves aggrecan at the Glu(373)-Ala(374) site, with the cleavage pattern and inhibitor profile being indistinguishable from that observed with native aggrecanase. A comparison of the structure and expression patterns of ADAMTS11, ADAMTS4, and ADAMTS1 is also described. Our findings will facilitate the study of the mechanisms of cartilage degradation and provide targets to search for effective inhibitors of cartilage depletion in arthritic disease.

ADAM Proteins↗

The role of synovial macrophages and macrophage-produced cytokines in driving aggrecanases, matrix metalloproteinases, and other destructive and inflammatory responses in osteoarthritis.

There is an increasing body of evidence that synovitis plays a role in the progression of osteoarthritis and that overproduction of cytokines and growth factors from the inflamed synovium can influence the production of degradative enzymes and the destruction of cartilage. In this study, we investigate the role of synovial macrophages and their main proinflammatory cytokines, interleukin (IL)-1 and tumour necrosis factor-alpha (TNF-alpha), in driving osteoarthritis synovitis and influencing the production of other pro- and anti-inflammatory cytokines, production of matrix metalloproteinases, and expression of aggrecanases in the osteoarthritis synovium. We established a model of cultures of synovial cells from digested osteoarthritis synovium derived from patients undergoing knee or hip arthroplasties. By means of anti-CD14-conjugated magnetic beads, specific depletion of osteoarthritis synovial macrophages from these cultures could be achieved. The CD14+-depleted cultures no longer produced significant amounts of macrophage-derived cytokines like IL-1 and TNF-alpha. Interestingly, there was also significant downregulation of several cytokines, such as IL-6 and IL-8 (p < 0.001) and matrix metalloproteinases 1 and 3 (p < 0.01), produced chiefly by synovial fibroblasts. To investigate the mechanisms involved, we went on to use specific downregulation of IL-1 and/or TNF-alpha in these osteoarthritis cultures of synovial cells. The results indicated that neutralisation of both IL-1 and TNF-alpha was needed to achieve a degree of cytokine (IL-6, IL-8, and monocyte chemoattractant protein-1) and matrix metalloproteinase (1, 3, 9, and 13) inhibition, as assessed by enzyme-linked immunosorbent assay and by reverse transcription-polymerase chain reaction (RT-PCR), similar to that observed in CD14+-depleted cultures. Another interesting observation was that in these osteoarthritis cultures of synovial cells, IL-1beta production was independent of TNF-alpha, in contrast to the situation in rheumatoid arthritis. Using RT-PCR, we also demonstrated that whereas the ADAMTS4 (a disintegrin and metalloprotease with thrombospondin motifs 4) aggrecanase was driven mainly by TNF-alpha, ADAMTS5 was not affected by neutralisation of IL-1 and/or TNF-alpha. These results suggest that, in the osteoarthritis synovium, both inflammatory and destructive responses are dependent largely on macrophages and that these effects are cytokine-driven through a combination of IL-1 and TNF-alpha.

Aged↗

A quantitative assay for aggrecanase activity.

Aggrecanase activities of ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) proteinases were measured with a recombinant aggrecan fragment and two monoclonal antibodies. Recombinant human aggrecan interglobular domain was first incubated in the presence of ADAMTS enzymes. The aggrecan peptide with the N-terminal sequence ARGSVIL released upon hydrolysis was then quantified in an enzyme-linked immunosorbent assay (ELISA) with an anti-neoepitope antibody specific for the N-terminal ARGSVIL sequence and a second anti-aggrecan peptide antibody. For higher sensitivity of the assay, P1-P5 residues of the aggrecanase site within the aggrecan substrate were changed by in vitro mutagenesis. Specific activities of recombinant truncated ADAMTS1 and ADAMTS4 estimated with authentic aggrecan interglobular domain amounted to 2.4 +/- 0.4 and 21.7 +/- 9.5 nmoles hydrolyzed substrate/min.mg, respectively. The values were 10.3 +/- 5.1 and 151.5 +/- 93.5 nmoles/min.mg for hydrolysis of the modified substrate. The aggrecanase activity assay can be used for (1) kinetic characterization of aggrecanase activities of human and animal ADAMTS, (2) screening of inhibitors for aggrecan hydrolyzing ADAMTS, and (3) estimation of aggrecanase activities in biological samples.

ADAM Proteins↗

Expression profiling of metalloproteinases and their inhibitors in synovium and cartilage.

Cartilage destruction in osteoarthritis (OA) is thought to be mediated by two main enzyme families; the matrix metalloproteinases (MMPs) are responsible for cartilage collagen breakdown, whereas enzymes from the 'a disintegrin and metalloproteinase domain with thrombospondin motifs' (ADAMTS) family mediate cartilage aggrecan loss. Tissue inhibitors of metalloproteinases (TIMPs) regulate the activity of these enzymes. Although cartilage destruction in OA might be driven by the chondrocyte, low-grade synovitis is reported in patients with all grades of this disease. Our earlier work profiling these gene families in cartilage identified a number of genes that are regulated in OA, which are hence implicated in the disease process. Because the synovium might contribute to cartilage-matrix destruction in OA, we have extended the screening in the current study. We have profiled MMP, ADAMTS and TIMP genes in both cartilage and synovium from patients with either OA of the hip or a fracture to the neck of femur (NOF), giving a more complete picture of proteolysis in this disease. The four most significantly upregulated genes (P < 0.0001) in OA synovium compared to the fractured NOF are MMP28, ADAMTS16, ADAMTS17 and TIMP2. For MMP9, MMP10, MMP12, MMP17, MMP23, MMP28, ADAMTS4, and ADAMTS9, there is a significant correlation between expression levels in the synovium and cartilage, suggesting similar mechanisms of regulation. Additionally, we have shown that in cartilage the median level of steady-state mRNA for MMP13 is approximately 20-fold higher than MMP28 and approximately 1,500-fold higher than ADAMTS16, with expression of this latter gene approximately 150-fold higher in synovium than cartilage. This study is the most comprehensive analysis of the metzincin family of proteinases in the joint to date and has identified several proteinase genes not previously reported to be expressed or regulated in synovium.

ADAM Proteins↗

Matrix metalloproteinases cleave connective tissue growth factor and reactivate angiogenic activity of vascular endothelial growth factor 165.

Vascular endothelial growth factor (VEGF), a potent angiogenic mitogen, plays a crucial role in angiogenesis under various pathophysiological conditions. We have recently demonstrated that VEGF(165), one of the VEGF isoforms, binds connective tissue growth factor (CTGF) and that its angiogenic activity is inhibited in the VEGF(165).CTGF complex form (Inoki, I., Shiomi, T., Hashimoto, G., Enomoto, H., Nakamura, H., Makino, K., Ikeda, E., Takata, S., Kobayashi, K. and Okada, Y. (2002) FASEB J. 16, 219-221). In the present study, we further examined the susceptibility of the VEGF(165).CTGF complex to matrix metalloproteinases (MMP-1, -2, -3, -7, -9, and -13), ADAMTS4 (aggrecanase-1), and serine proteinases, and evaluated the recovery of the angiogenic activity of VEGF(165) after the treatment. Among the MMPs, MMP-1, -3, -7, and -13 processed CTGF of the complex into the major NH(2)- and COOH-terminal fragments, whereas VEGF(165) was completely resistant to the MMPs. On the other hand, elastase and plasmin cleaved both CTGF and VEGF(165) of the complex, but they were completely resistant to ADAMTS4. By digestion of the immobilized VEGF(165).CTGF complex with MMP-3 or MMP-7, both NH(2)- and COOH-terminal fragments of CTGF were dissociated and released from the complex into the liquid phase. The in vitro angiogenic activity of VEGF(165) blocked in the VEGF(165).CTGF complex was reactivated to original levels after CTGF digestion of the complex with MMP-1, -3, and -13. Recovery of angiogenic activity was further confirmed by in vivo angiogenesis assay using a Matrigel injection model in mice. These results demonstrate for the first time that CTGF is a substrate of MMPs and that the angiogenic activity of VEGF(165) suppressed by the complex formation with CTGF is recovered through the selective degradation of CTGF by MMPs. MMPs may play a novel role through CTGF degradation in VEGF-induced angiogenesis during embryonic development, tissue maintenance, and/or pathological processes of various diseases.

Animals↗