The ADAMTS metalloproteinases

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Role of Sp1 transcription factor in Interleukin-1-induced ADAMTS-4 (aggrecanase-1) gene expression in human articular chondrocytes

Proinflammatory cytokines such as interleukin-1 beta (IL-1β) stimulate cartilage extracellular matrix aggrecan degradation by aggrecanases or ADAMTS (a disintegrin and metalloproteinase with thrombospondin motif) during the pathogenesis of arthritis. Human aggrecanase-1 (ADAMTS-4) gene promoter contains at least one specificity protein-1 (Sp1)-transcription factor-binding site. We investigated the previously unknown role of Sp1 in the regulation of ADAMTS-4 gene expression in human articular chondrocytes. Mithramycin and WP631, the specific inhibitors of guanine cytosine (GC)-rich Sp1 DNA binding, partially suppressed IL-1-induced ADAMTS-4 expression and activity. Genetic inhibition of Sp1 by antisense oligonucleotide or by small interfering RNA (siRNA)-mediated Sp1 knockdown partially inhibited ADAMTS-4 induction by IL-1. Sense oligonucleotide and negative control siRNA had no effect. In contrast, cytomegalovirus promoter-driven Sp1 overexpression further enhanced IL-1-induced ADAMTS-4 expression and activity. Constitutively expressed glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was not affected by any of the agents. These results provide pharmacological and genetic evidence for the importance of Sp1 in ADAMTS-4 gene regulation by IL-1. Thus, Sp1 could be potentially targeted to reduce arthritis-associated cartilage aggrecan loss.

Expression of ADAMTS12 in colorectal cancer-associated stroma prevents cancer development and is a good prognostic indicator of colorectal cancer

AIM

The aim of this study was to investigate the role of ADAMTS12 in colorectal cancer progression and to examine whether ADAMTS-12 can be considered as a prognostic indicator for colorectal cancer.

METHODS

This study was performed on formalin-fixed paraffin-embedded resected specimens obtained from 112 patients with colorectal cancer. The expression level of ADAMTS12 was investigated by immunohistochemical staining to assess the relationship between ADAMTS12 expression and the clinicopathologic factors and to study the prognostic significance of ADAMTS12 in colorectal cancer patients.

RESULTS

ADAMTS12 expression was mainly localized in the fibroblasts adjacent to the tumor cells or in macrophages in front of the invasive cancer margins. The ADAMTS12 expression was significantly correlated with the tumor histological grade, depth of tumor invasion, lymph node metastasis, and Dukes' stage. Patients with low or no ADAMTS12 expression in the tumor stroma had a significantly poor overall survival or disease-free survival.

CONCLUSION

The expression of ADAMTS12 in colorectal cancer stroma plays an important role in inhibiting tumor development. Patients with ADAMTS12 expression showed better prognosis than those without ADAMTS12 expression. Thus, ADAMTS12 expression may be a good prognostic marker for colorectal cancer.

Gene expression profiling reveals new potential players of gonad differentiation in the chicken embryo

BACKGROUND

In birds as in mammals, a genetic switch determines whether the undifferentiated gonad develops into an ovary or a testis. However, understanding of the molecular pathway(s) involved in gonad differentiation is still incomplete.

METHODOLOGY/PRINCIPAL FINDINGS

With the aim of improving characterization of the molecular pathway(s) involved in gonad differentiation in the chicken embryo, we developed a large scale real time reverse transcription polymerase chain reaction approach on 110 selected genes for evaluation of their expression profiles during chicken gonad differentiation between days 5.5 and 19 of incubation. Hierarchical clustering analysis of the resulting datasets discriminated gene clusters expressed preferentially in the ovary or the testis, and/or at early or later periods of embryonic gonad development. Fitting a linear model and testing the comparisons of interest allowed the identification of new potential actors of gonad differentiation, such as Z-linked ADAMTS12, LOC427192 (corresponding to NIM1 protein) and CFC1, that are upregulated in the developing testis, and BMP3 and Z-linked ADAMTSL1, that are preferentially expressed in the developing ovary. Interestingly, the expression patterns of several members of the transforming growth factor β family were sexually dimorphic, with inhibin subunits upregulated in the testis, and bone morphogenetic protein subfamily members including BMP2, BMP3, BMP4 and BMP7, upregulated in the ovary. This study also highlighted several genes displaying asymmetric expression profiles such as GREM1 and BMP3 that are potentially involved in different aspects of gonad left-right asymmetry.

CONCLUSION/SIGNIFICANCE

This study supports the overall conservation of vertebrate sex differentiation pathways but also reveals some particular feature of gene expression patterns during gonad development in the chicken. In particular, our study revealed new candidate genes which may be potential actors of chicken gonad differentiation and provides evidence of the preferential expression of BMPs in the developing ovary and Inhibin/Activin subunits in the developing testis.

Proteoglycan degradation by the ADAMTS family of proteinases

Proteoglycans are key components of extracellular matrices, providing structural support as well as influencing cellular behaviour in physiological and pathological processes. The diversity of proteoglycan function reported in the literature is equally matched by diversity in proteoglycan structure. Members of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin motifs) family of enzymes degrade proteoglycans and thereby have the potential to alter tissue architecture and regulate cellular function. In this review, we focus on ADAMTS enzymes that degrade the lectican and small leucine-rich repeat families of proteoglycans. We discuss the known ADAMTS cleavage sites and the consequences of cleavage at these sites. We illustrate our discussion with examples from the literature in which ADAMTS proteolysis of proteoglycans makes profound changes to tissue function.

Calcium modulates force sensing by the von Willebrand factor A2 domain

von Willebrand factor (VWF) multimers mediate primary adhesion and aggregation of platelets. VWF potency critically depends on multimer size, which is regulated by a feedback mechanism involving shear-induced unfolding of the VWF-A2 domain and cleavage by the metalloprotease ADAMTS-13. Here we report crystallographic and single-molecule optical tweezers data on VWF-A2 providing mechanistic insight into calcium-mediated stabilization of the native conformation that protects A2 from cleavage by ADAMTS-13. Unfolding of A2 requires higher forces when calcium is present and primarily proceeds through a mechanically stable intermediate with non-native calcium coordination. Calcium further accelerates refolding markedly, in particular, under applied load. We propose that calcium improves force sensing by allowing reversible force switching under physiologically relevant hydrodynamic conditions. Our data show for the first time the relevance of metal coordination for mechanical properties of a protein involved in mechanosensing.

Enzymatic toxins from snake venom: structural characterization and mechanism of catalysis

Snake venoms are cocktails of enzymes and non-enzymatic proteins used for both the immobilization and digestion of prey. The most common snake venom enzymes include acetylcholinesterases, l-amino acid oxidases, serine proteinases, metalloproteinases and phospholipases A(2) . Higher catalytic efficiency, thermal stability and resistance to proteolysis make these enzymes attractive models for biochemists, enzymologists and structural biologists. Here, we review the structures of these enzymes and describe their structure-based mechanisms of catalysis and inhibition. Some of the enzymes exist as protein complexes in the venom. Thus we also discuss the functional role of non-enzymatic subunits and the pharmacological effects of such protein complexes. The structures of inhibitor-enzyme complexes provide ideal platforms for the design of potent inhibitors which are useful in the development of prototypes and lead compounds with potential therapeutic applications.

Partially redundant functions of Adamts1 and Adamts4 in the perinatal development of the renal medulla

Adamts4 encodes a widely-expressed proteinase thought to be involved in processes ranging from cartilage metabolism to ovarian follicle development. To study its physiological roles, Adamts4-null mice were created by gene targeting. Unexpectedly, these were found to be phenotypically normal, suggesting that other gene(s) may compensate for its loss. Adamts4(-/-) mice were, therefore, crossed with a strain lacking Adamts1, whose pattern of expression and substrate specificity overlap that of Adamts4. Most (>95%) Adamts1(-/-) ;Adamts4(-/-) mice died within 72 hr after birth with a marked thinning of the renal medulla. The renal defect was not observed in embryonic Adamts1(-/-) ;Adamts4(-/-) kidneys, but became apparent around birth. The few (<5%) Adamts1(-/-) ;Adamts4(-/-) animals to reach adulthood had the same renal phenotype seen in newborns. This study is thus the first to report Adamts4 expression and function in the mammalian kidney, and to demonstrate that Adamts1 and Adamts4 play redundant and essential roles in perinatal kidney development.

A 3D cartilage - inflammatory cell culture system for the modeling of human osteoarthritis

Inflammation plays a major role in the destruction of cartilage in osteoarthritis (OA), with the interaction of multiple mediators, immune cells, fibroblasts and chondrocytes. Current 2D studies in vitro with cell lines, as well as animal models, are limited in terms of providing insight into pathogenic mechanisms related to the human system. Hence, an in vitro human 3D cartilage tissue system was established to study the impact of inflammatory mediators on chondrocytes and matrices as an initial approach to emulating early stages of OA. An in vitro 3D human cartilage tissue system was established by culturing primary chondrocytes in silk protein porous scaffolds up to 21 days in static culture, with and without cytokine (IL-1β and TNF-α) exposure or with the use of macrophage conditioned medium (MCM). To assess chondrocyte responses, transcript levels, histology and immunohistochemistry were used to assess changes in cell viability and in cartilage matrix composition, including collagen type II and aggrecan. Chondrocyte hypertrophy and apoptosis were assessed via collagen type X and caspase-3. RT-PCR revealed that the cytokines and the MCM regulated matrix-related gene expression of chondrocytes, but with different outcomes. For anabolic-encoding genes, MCM suppressed collagen type II and upregulated aggrecan. In contrast, the cytokines suppressed aggrecan formation and had no effect on collagen type II. For catabolic-encoded genes, both cytokines and MCM upregulated MMP1, MMP3, MMP13 and ADAMTS4, with cytokines preferentially upregulating MMP13 and MCM upregulating ADMTS4. MCM down-regulated ADAMTS5. In addition, MCM stimulation led to hypertrophy and apoptosis of chondrocytes, outcomes not found with the cytokine treatment group. A decrease in aggrecan content with cytokines and MCM stimulation was found, while MCM resulted in greater reduction than the cytokine treatment. The results demonstrated that OA-like features, such as changes in matrix synthesis gene expression, increase of collagense gene expression and loss of aggrecan, were initiated within this 3D chrondrocyte human tissue system upon stimulation of the cultures with cytokines and MCM. MCM was a better inducer of immune-related features of OA, because besides the features found with cytokine stimulation, the MCM treatment also initiated collagen X expression and deposition and apoptosis of chondrocytes, important features of human OA. The results obtained with this new in vitro tissue model provide an initial step towards the development of an early stage OA system to allow for more systematic study and insight into the origins and outcomes with this disease.

New opportunities in drug design of metalloproteinase inhibitors: combination between structure-function experimental approaches and systems biology

INTRODUCTION

MMPs (matrix metalloproteinases) and ADAMs (a disintegrin and metalloproteinases) are endopeptidases central to the degradation and remodeling of the extracellular matrix. These proteases also exhibit regulatory activity in cell signaling pathways and thus tissue homeostasis under normal conditions and in many diseases. Consequently, individual members of the MMP and ADAM protein families were identified as important therapeutic targets. However, designing effective inhibitors in vivo for this class of enzymes appears to be extremely challenging. This is attributed to the broad structural similarity of their active sites and to the dynamic functional interconnectivity of MMPs with other proteases, their inhibitors, and substrates (the so-called degradome) in healthy and disease tissues.

AREAS COVERED

The article covers the progress in designing metalloproteinase inhibitors, based on recent advancements in our understanding of enzyme structures and their function as master regulators. It also discusses the potential of utilizing structure-based drug design strategies in conjunction with systems biology experimental approaches for designing potent and therapeutically effective metalloproteinase inhibitors.

EXPERT OPINION

We highlight the use of protein-based drug design strategies, for example, antibodies and protein scaffolds, targeting extracatalytic domains, which are central to proteolytic and non-proteolytic enzyme functions. Such rationally designed function-blocking inhibitors may create new opportunities in disease management and in emerging therapies that require control of dysregulated MMP activity without causing severe side effects. Importantly, the lessons learned from studying these protein-based inhibitors can be implemented to design new and effective small or medium sized synthetic antagonists.

Chromatin remodeling in cardiovascular development and physiology

Chromatin regulation provides an important means for controlling cardiac gene expression under different physiological and pathological conditions. Processes that direct the development of normal embryonic hearts and pathology of stressed adult hearts may share general mechanisms that govern cardiac gene expression by chromatin-regulating factors. These common mechanisms may provide a framework for us to investigate the interactions among diverse chromatin remodelers/modifiers and various transcription factors in the fine regulation of gene expression, essential for all aspects of cardiovascular biology. Aberrant cardiac gene expression, triggered by a variety of pathological insults, can cause heart diseases in both animals and humans. The severity of cardiomyopathy and heart failure correlates strongly with abnormal cardiac gene expression. Therefore, controlling cardiac gene expression presents a promising approach to the treatment of human cardiomyopathy. This review focuses on the roles of ATP-dependent chromatin-remodeling factors and chromatin-modifying enzymes in the control of gene expression during cardiovascular development and disease.

Regulated expression of ADAMTS-12 in human trophoblastic cells: a role for ADAMTS-12 in epithelial cell invasion?

Metastatic carcinoma cells exploit the same molecular machinery that allows human placental cytotrophoblasts to develop an invasive phenotype. As altered expression levels of ADAMTS (ADisintegrin And Metalloproteinase with ThromboSpondin repeats) subtypes have been associated with cancer progression, we have examined the function and regulation of members of this gene family in epithelial cell invasion using cultures of highly invasive extravillous cytotrophoblasts and the poorly invasive JEG-3 cytotrophoblast cell line as model systems. Of the multiple ADAMTS subtypes identified in first trimester human placenta and these two trophoblastic cell types, only ADAMTS-12 was preferentially expressed by extravillous cytotrophoblasts. Transforming growth factor-β1 and interleukin-1β, two cytokines that promote and restrain cytotrophoblast invasion in vitro, were also found to differentially regulate trophoblastic ADAMTS-12 mRNA levels. Loss- or gain-of-function studies confirmed that ADAMTS-12, independent of its proteolytic activity, plays a specific, non-redundant role in trophoblast invasion. Furthermore, we demonstrated that ADAMTS-12 regulated cell-extracellular matrix adhesion and invasion through a mechanism involving the αvβ3 integrin heterodimer. This study identifies a novel biological role for ADAMTS-12, and highlights the importance and complexity of its non-proteolytic domain(s) pertaining to its function.

ADAMTSL3 as a candidate gene for schizophrenia: gene sequencing and ultra-high density association analysis by imputation

We previously reported an association with a putative functional variant in the ADAMTSL3 gene, just below genome-wide significance in a genome-wide association study of schizophrenia. As variants impacting the function of ADAMTSL3 (a disintegrin-like and metalloprotease domain with thrombospondin type I motifs-like-3) could illuminate a novel disease mechanism and a potentially specific target, we have used complementary approaches to further evaluate the association. We imputed genotypes and performed high density association analysis using data from the HapMap and 1000 genomes projects. To review all variants that could potentially cause the association, and to identify additional possible pathogenic rare variants, we sequenced ADAMTSL3 in 92 schizophrenics. A total of 71 ADAMTSL3 variants were identified by sequencing, many were also seen in the 1000 genomes data, but 26 were novel. None of the variants identified by re-sequencing was in strong linkage disequilibrium (LD) with the associated markers. Imputation analysis refined association between ADAMTSL3 and schizophrenia, and highlighted additional common variants with similar levels of association. We evaluated the functional consequences of all variants identified by sequencing, or showing direct or imputed association. The strongest evidence for function remained with the originally associated variant, rs950169, suggesting that this variant may be causal of the association. Rare variants were also identified with possible functional impact. Our study confirms ADAMTSL3 as a candidate for further investigation in schizophrenia, using the variants identified here. The utility of imputation analysis is demonstrated, and we recommend wider use of this method to re-evaluate the existing canon of suggestive schizophrenia associations.

The expression of a disintegrin and metalloproteinase with thrombospondin motifs 4 in human macrophages is inhibited by the anti-atherogenic cytokine transforming growth factor-β and requires Smads, p38 mitogen-activated protein kinase and c-Jun

Atherosclerosis is an inflammatory disorder of the vasculature that is orchestrated by the action of cytokines. Macrophages play a prominent role in all stages of this disease, including foam cell formation, production of reactive oxygen species, modulation of the inflammatory response and the regulation of the stability of atherosclerotic plaques. The role of the matrix metalloproteinase family in the control of plaque stability is well established. A disintegrin and metalloproteinase with thrombospondin motif (ADAMTS) family has been implicated in several diseases and the expression of ADAMTS-4 in macrophages of atherosclerotic lesions has suggested a potential role for this protease in atherosclerosis. However, the action of cytokines on the expression of ADAMTS-4 in macrophages is poorly understood. We have investigated here the effect of transforming growth factor-β (TGF-β) on ADAMTS-4 expression in macrophages along with the regulatory mechanisms underlying its actions. Consistent with the anti-atherogenic role of TGF-β, this cytokine decreased the expression of ADAMTS-4 mRNA and protein in human macrophages. Transient transfection assays showed that the −100 to +10 promoter region contained the minimal TGF-β response elements. Small-interfering RNA-mediated knockdown revealed a critical role for Smads, p38 mitogen-activated protein kinase and c-Jun in the action of TGF-β on ADAMTS-4 mRNA expression. These studies show for the first time that TGF-β inhibits the expression of ADAMTS-4 in human macrophages and identifies the signalling pathways underlying this response. The inhibition of macrophage ADAMTS-4 expression is likely to contribute to the anti-atherogenic, plaque stabilisation action of TGF-β.

Mapping of the disease locus and identification of ADAMTS10 as a candidate gene in a canine model of primary open angle glaucoma

Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide, with elevated intraocular pressure as an important risk factor. Increased resistance to outflow of aqueous humor through the trabecular meshwork causes elevated intraocular pressure, but the specific mechanisms are unknown. In this study, we used genome-wide SNP arrays to map the disease gene in a colony of Beagle dogs with inherited POAG to within a single 4 Mb locus on canine chromosome 20. The Beagle POAG locus is syntenic to a previously mapped human quantitative trait locus for intraocular pressure on human chromosome 19. Sequence capture and next-generation sequencing of the entire canine POAG locus revealed a total of 2,692 SNPs segregating with disease. Of the disease-segregating SNPs, 54 were within exons, 8 of which result in amino acid substitutions. The strongest candidate variant causes a glycine to arginine substitution in a highly conserved region of the metalloproteinase ADAMTS10. Western blotting revealed ADAMTS10 protein is preferentially expressed in the trabecular meshwork, supporting an effect of the variant specific to aqueous humor outflow. The Gly661Arg variant in ADAMTS10 found in the POAG Beagles suggests that altered processing of extracellular matrix and/or defects in microfibril structure or function may be involved in raising intraocular pressure, offering specific biochemical targets for future research and treatment strategies.

Primary open angle glaucoma (POAG) is a leading cause of vision loss and blindness affecting tens of millions of people. Ocular hypertension is a strong risk factor for the disease and the only effective target of treatment. Ocular hypertension results from increased resistance to outflow of aqueous humor through the trabecular meshwork, a specialized filtration tissue consisting of alternating layers of cells and connective tissue, but the specific reasons for the increased resistance are not known. The animal model for human POAG used in this study was a colony of Beagle dogs that carry an inherited form of the disease in which ocular hypertension is the primary manifestation. We have found a variant in ADAMTS10 that belongs to a family of genes that contribute to formation of extracellular matrix and may itself be involved in formation of elastic microfiber structures. We found that the ADAMTS10 protein is expressed at particularly high levels in the trabecular meshwork. The candidate variant in ADAMTS10 found in the POAG–affected Beagles suggests that altered processing of connective tissue and/or elastic microfiber defects may be involved in raising eye pressure, offering specific biochemical targets for future research and treatment strategies.

A bioresponsive hydrogel tuned to chondrogenesis of human mesenchymal stem cells

Cartilage tissue engineering aims to replace damaged or diseased tissue with a functional regenerate that restores joint function. Scaffolds are used to deliver cells and facilitate tissue development, but they can also interfere with the structural assembly of the cartilage matrix. Biodegradable scaffolds have been proposed as a means to improve matrix deposition and the biomechanical properties of neocartilage. The challenge is designing scaffolds with appropriate degradation rates, ideally such that scaffold degradation is proportional to matrix deposition. In this study, we developed a bioresponsive hydrogel with cell-mediated degradation aligned to the chondrogenic differentiation of human mesenchymal stem cells (hMSCs). We identified matrix metalloproteinase 7 (MMP7) as an enzyme with a temporal expression pattern that corresponded with cartilage development. By embedding MMP7 peptide substrates within a poly(ethylene glycol) diacrylate backbone, we built MMP7-sensitive hydrogels with distinct degradation rates. When MMP7-sensitive scaffolds were compared with nondegradable scaffolds in vitro, photoencapsulated hMSCs produced neocartilage constructs with more extensive collagenous matrices, as demonstrated through immunohistochemistry and biochemical quantification of matrix molecules. Furthermore, these changes translated into an increased dynamic compressive modulus. This work presents a practical strategy for designing biomaterials uniquely tuned to individual biological processes.

C. elegans ADAMTS ADT-2 regulates body size by modulating TGFβ signaling and cuticle collagen organization

Organismal growth and body size are influenced by both genetic and environmental factors. We have utilized the strong molecular genetic techniques available in the nematode Caenorhabditis elegans to identify genetic determinants of body size. In C. elegans, DBL-1, a member of the conserved family of secreted growth factors known as the Transforming Growth Factor β superfamily, is known to play a major role in growth control. The mechanisms by which other determinants of body size function, however, is less well understood. To identify additional genes involved in body size regulation, a genetic screen for small mutants was previously performed. One of the genes identified in that screen was sma-21. We now demonstrate that sma-21 encodes ADT-2, a member of the ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) family of secreted metalloproteases. ADAMTS proteins are believed to remodel the extracellular matrix and may modulate the activity of extracellular signals. Genetic interactions suggest that ADT-2 acts in parallel with or in multiple size regulatory pathways. We demonstrate that ADT-2 is required for normal levels of expression of a DBL-1-responsive transcriptional reporter. We further demonstrate that adt-2 regulatory sequences drive expression in glial-like and vulval cells, and that ADT-2 activity is required for normal cuticle collagen fibril organization. We therefore propose that ADT-2 regulates body size both by modulating TGFβ signaling activity and by maintaining normal cuticle structure.

Angiogenesis and Proteinases: Influence on Vascular Morphogenesis, Stabilization and Regression

Proteinases play a key role during angiogenesis and have been implicated in vascular morphogenesis, stabilization and regression. Major advances have identified specific proteinases and their inhibitors that separately control these processes. Relevant proteinases include cell surface or soluble metalloproteinases, serine proteinases and cathepsins that affect these events and a critical issue concerns how these proteinases are balanced by their inhibitors to affect tissue vascularization. Importantly, heterotypic communication of endothelial cells with vessel supporting cells such as pericytes controls proteinase and inhibitor expression to regulate these processes.

The quantification of ADAMTS4 and 8 expression and selection of reference genes for quantitative real-time PCR analysis in myocardial infarction

INTRODUCTION

ADAMTS4 and ADAMTS8 are proteases involved in ECM proteolysis and antiangiogenesis, but little is known about their expression and function in myocardial infarction (MI). We examined ADAMTS4 and ADAMTS8 expression in a rat MI model by quantitative real-time polymerase chain reaction (qPCR) and enzyme linked immunosorbent assay (ELISA). The expressions of glyseraldehyde-3-phosphate dehydrogenase (GAPDH), beta-actin (ACTB), acidic ribosomal phosphoprotein P0 (ARBP), and ribosomal protein L13A (RPL13A) were examined in order to validate the appropriate housekeeping genes after MI.

METHODS

Male Wistar rats were subjected to MI, and infarcted myocardial tissue was collected at 3, 6, 12, 24h, 3, 7, 14 and 21days after MI. ADAMTS4, ADAMTS8, and the four housekeeping genes were quantified using qPCR and the expression stability of the four housekeeping genes was investigated using GeNorm software. The protein levels of ADAMTS4 were detected using ELISA kits.

RESULTS

The M values of GAPDH, ACTB, ARBP and RPL13A were 0.721, 1.2, 0.812 and 0.812 respectively. GAPDH and ARBP were ranked the most stable genes. ADAMTS4 mRNA increased at 3h after MI, peaked at 6h, then decreased rapidly. ADAMTS8 mRNA increased at 6h, peaked at 24h, remained high at 3d, then decreased gradually. The protein levels of ADAMTS4 were significantly increased at 6h, 12h, 24h and 3d after MI.

CONCLUSION

The results suggest that GAPDH and ARBP are two appropriate housekeeping genes for the rat MI model. Both ADAMTS4 and ADAMTS8 mRNA levels and ADAMTS4 protein level increased, but they exhibited different expression profiles.

Metzincin proteases and their inhibitors: foes or friends in nervous system physiology?

Members of the metzincin family of metalloproteinases have long been considered merely degradative enzymes for extracellular matrix molecules. Recently, however, there has been growing appreciation for these proteinases and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs), as fine modulators of nervous system physiology and pathology. Present all along the phylogenetic tree, in all neural cell types, from the nucleus to the synapse and in the extracellular space, metalloproteinases exhibit a complex spatiotemporal profile of expression in the nervous parenchyma and at the neurovascular interface. The irreversibility of their proteolytic activity on numerous biofactors (e.g., growth factors, cytokines, receptors, DNA repair enzymes, matrix proteins) is ideally suited to sustain structural changes that are involved in physiological or postlesion remodeling of neural networks, learning consolidation or impairment, neurodegenerative and neuroinflammatory processes, or progression of malignant gliomas. The present review provides a state of the art overview of the involvement of the metzincin/TIMP system in these processes and the prospects of new therapeutic strategies based on the control of metalloproteinase activity.

ADAM and ADAMTS gene expression in native and wound healing human lens epithelial cells

PURPOSE

The ADAMs (a disintegrin and metalloproteinase) and the ADAMTSs (a disintegrin and metalloproteinase with thrombospondin-like motifs) are extracellular proteases that mediate cellular interactions and cell signaling via the modulation of adhesion and the cleavage of cell surface protein ectodomains and extracellular matrix molecules. Gene expression profiling was undertaken to better understand the role of the ADAM and ADAMTS families in the clear native human lenses and following surgical injury with particular relevance to posterior capsule opacification.

METHODS

To carry out profile analysis, the lens (t=0d) was dissected into three regions; anterior epithelia, equatorial region, and fiber cells. Capsular bag culture was undertaken as a means of assessing short-term changes (t=6d) and post-cataractous lens capsular bags (ex vivo) were used to predict long-term changes in ADAM/ADAMTS gene expression. RNA was isolated and quantitative real-time (TaqMan) reverse transcription-PCR (RT-PCR) performed. Data were analyzed in terms of cycle threshold number (C(T)) and also normalized relative to endogenous 18S rRNA.

RESULTS

High expression of ADAM-9, -10, -15, and -17 was detected in all native lens regions. ADAM-15 expression was a characteristic of the native lens epithelia more than the fibers. Post-surgical injury, lens capsular bags showed a positive shift in ADAM/ADAMTS expression that was significant for ADAM-9, -15, and ADAMTS-3. Ex vivo capsular bags, with a long-term post surgical injury period, maintained high expression of ADAM-9 and -10 genes.

CONCLUSIONS

The native human lens expresses ADAM and ADAMTS genes that are differentially regulated following surgical injury. Roles in maintaining cellular adhesion may be of particular importance to native lens tissue integrity and may be lost in the lens wound healing response following cataract surgery.

Mechanical loading, cartilage degradation, and arthritis

Joint tissues are exquisitely sensitive to their mechanical environment, and mechanical loading may be the most important external factor regulating the development and long-term maintenance of joint tissues. Moderate mechanical loading maintains the integrity of articular cartilage; however, both disuse and overuse can result in cartilage degradation. The irreversible destruction of cartilage is the hallmark of osteoarthritis and rheumatoid arthritis. In these instances of cartilage breakdown, inflammatory cytokines such as interleukin-1 beta and tumor necrosis factor-alpha stimulate the production of matrix metalloproteinases (MMPs) and aggrecanases (ADAMTSs), enzymes that can degrade components of the cartilage extracellular matrix. In order to prevent cartilage destruction, tremendous effort has been expended to design inhibitors of MMP/ADAMTS activity and/or synthesis. To date, however, no effective clinical inhibitors exist. Accumulating evidence suggests that physiologic joint loading helps maintain cartilage integrity; however, the mechanisms by which these mechanical stimuli regulate joint homeostasis are still being elucidated. Identifying mechanosensitive chondroprotective pathways may reveal novel targets or therapeutic strategies in preventing cartilage destruction in joint disease.

Proteoglycans: key regulators of pulmonary inflammation and the innate immune response to lung infection

Exposure to viruses and bacteria results in lung infections and places a significant burden on public health. The innate immune system is an early warning system that recognizes viruses and bacteria, which results in the rapid production of inflammatory mediators such as cytokines and chemokines and the pulmonary recruitment of leukocytes. When leukocytes emigrate from the systemic circulation through the extracellular matrix (ECM) in response to lung infection they encounter proteoglycans, which consist of a core protein and their associated glycosaminoglycans. In this review, we discuss how proteoglycans serve to modify the pulmonary inflammatory response and leukocyte migration through a number of different mechanisms including: (1) The ability of soluble proteoglycans or fragments of glycosaminoglycans to activate Toll-like receptor (TLRs) signaling pathways; (2) The binding and sequestration of cytokines, chemokines, and growth factors by proteoglycans; (3) the ability of proteoglycans and hyaluronan to facilitate leukocyte adhesion and sequestration; and (4) The interactions between proteoglycans and matrix metalloproteinases (MMP) that alter the function of these proteases. In conclusion, proteoglycans fine-tune tissue inflammation through a number of different mechanisms. Clarification of the mechanisms whereby proteoglycans modulate the pulmonary inflammatory response will most likely lead to new therapeutic approaches to inflammatory lung disease and lung infection.

Variability in melanoma metalloproteinase expression profiling

The proteolytic activities of a disintegrin and metalloproteinase (ADAM); a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), and matrix metalloproteinase (MMP) families play important roles in normal and multiple pathological conditions. These metalloproteases have potential roles in the degradation of the ECM and in the processing of bioactive molecules. In the present study, RNA was isolated from multiple normal fibroblast and metastatic melanoma cell lines, as well as the isogenic normal tissue and tumor samples, and the gene expression levels of six ADAMs, eight MMPs, and four ADAMTSs were analyzed by real-time PCR. This approach allowed for detected changes in mRNA expression of the individual metalloproteinase genes to be compared between normal and metastatic states and also between tissue and cultured cells. Increased gene expression of several ADAM and MMP family members (MMP1, MMP8, MMP15, and ADAM15) occurred in melanoma tissue and was replicated in tissue cultures. In general, the level of ADAM and MMP mRNA expression was several-fold higher in cultured cells compared with the isogenic tissue from which they were derived. Passage-dependent expression patterns were observed for MMP8 and MMP9 in in-house-derived metastatic melanoma cell lines. This reiterates earlier suggestions that experiments using cells that have been maintained in culture should be interpreted with great care.

Lentiviral shRNA knock-down of ADAMTS-5 and -9 restores matrix deposition in 3D chondrocyte culture

Aggrecan is one of the two major constituents of articular cartilage, and during diseases such as osteoarthritis (OA) it is subject to degradation by proteolytic enzymes. The primary proteases responsible for aggrecan cleavage are the aggrecanases, identified as members of the ADAMTS family of proteases, which are upregulated in response to inflammatory stimuli. It is uncertain which of the six aggrecanases (ADAMTS-1, -4, -5, -8, -9 and -15) are primarily responsible for the degradation of aggrecan in human cartilage. Here we show that four of the six aggrecanases are expressed in immortalized chondrocyte cell-lines and can be upregulated in response to inflammatory cytokines. Using RNA interference, we demonstrate robust knock-down of ADAMTS-5 and -9 expression in these cells and, by culturing them on three-dimensional (3D) scaffolds, show that reduction in expression of ADAMTS-5 enzyme results in an increase in matrix deposition. These data suggest that the quality of tissue-engineered cartilage matrix might be improved by targeted depletion of aggrecanase expression. Moreover, this work also provides further evidence that ADAMTS-5 may be a therapeutic target in the treatment of arthritic disease.

Advances in the development of novel aggrecanase inhibitors

IMPORTANCE OF THE FIELD

Aggrecanases are members of a disintegrin and metalloprotease with thrombospondin motif family of zinc metalloproteases involved in the cleavage of aggrecan fragments in cartilage. Inhibition of aggrecanase activity in osteoarthritis (OA) patients should both provide symptomatic relief of OA pain as well as OA disease modification.

AREAS COVERED IN THIS REVIEW

This article reviews patent applications containing compounds claimed to have aggrecanase inhibitory activity which were published from 2005 through August 2010.

WHAT THE READER WILL GAIN

Readers will be informed of the different classes of disclosed aggrecanase inhibitors and gain an understanding of how these series interact with the various components of the catalytic sites of these enzymes.

TAKE HOME MESSAGE

Patenting in the area of aggrecanase inhibitors has been modest. Most of the patented chemical matter are lipophilic, acidic compounds with molecular mass (MM) > 400: properties that usually do not imbue good systemic compound exposure. Possibly due to these properties and poor exposure, there are no late state aggrecanase compounds in the clinic to our knowledge. The future development of lower MM, less acidic aggrecanase inhibitors with good pharmacokinetic profiles could increase activity in this field as aggrecanases are well-validated targets for diseases such as OA.

Mutational and functional analysis reveals ADAMTS18 metalloproteinase as a novel driver in melanoma

The disintegrin-metalloproteinases with thrombospondin domains (ADAMTS) genes have been suggested to function as tumor suppressors as several have been found to be epigenetically silenced in various cancers. We performed a mutational analysis of the ADAMTS gene family in human melanoma and identified a large fraction of melanomas to harbor somatic mutations. To evaluate the functional consequences of the most commonly mutated gene, ADAMTS18, six of its mutations were biologically examined. ADAMTS18 mutations had little effect on melanoma cell growth under standard conditions, but reduced cell dependence on growth factors. ADAMTS18 mutations also reduced adhesion to laminin and increased migration in vitro and metastasis in vivo. Melanoma cells expressing mutant ADAMTS18 had reduced cell migration after short hairpin RNA-mediated knockdown of ADAMTS18, suggesting that ADAMTS18 mutations promote growth, migration, and metastasis in melanoma.

Profile of macrophages in human abdominal aortic aneurysms: a transcriptomic, proteomic, and antibody protein array study

Abdominal aortic aneurysms (AAA) are defined by an increased aortic diameter and characterized by impairment of the extracellular matrix, macrophages infiltration and decreased density of smooth muscle cells. Our aim is to identify the key molecules involved in the pathogenesis of AAAs. This study investigated transcriptomic and proteomic profiles of macrophages from AAA patients (>50 mm aortic diameter) (n = 24) and peripheral arterial occlusion (PAO) patients without AAA detected (n = 18), who both needed a surgery. An antibody protein microarray, generated by printing antibodies onto membranes against proteins selected from the transcriptomic and proteomic analysis, was performed to validate the proteins differentially expressed specifically in macrophages and plasma from the same patients. We found a restricted number of proteins differentially expressed between AAA and PAO patients: TIMP-3, ADAMTS5, and ADAMTS8 that differ significantly in plasma of AAA patients compared to PAO patients, as found in the macrophages. In contrast to plasma MMP-9, soluble glycoprotein V (sGPV) and plasmin-antiplasmin complex levels, plasma TIMP-3 levels were not correlated to AAA size but interestingly correlated to sGPV, a platelet activation marker. Combining transcriptomic and proteomic is a valid approach to identify diseases causing proteins and potential biomarkers.

Transcript levels of major MMPs and ADAMTS-4 in relation to the clinicopathological profile of patients with lumbar disc herniation

The involvement of matrix metalloproteinases (MMPs) in both the pathogenesis of intervertebral disc (ID) herniation and the spontaneous regression of herniated ID fragments remains only partially elucidated. The purpose of the present study was to simultaneously examine the transcript levels of a large number of MMPs (-1, -3, -8, -9, -13 and -14) and ADAMTS-4 (a disintegrin and metalloproteinase with thrombospondin motifs) and to investigate their correlation with the clinicopathologic profile of patients suffering from symptomatic lumbar ID herniation. mRNA expression levels were determined by means of the real-time polymerase chain reaction in 63 herniated and 10 control ID specimens. Our results showed multiple positive correlations among all MMPs and ADAMTS-4 mRNA in herniated samples, indicating their possible synergistic effect in ID herniation. MMP-9 and -13 mRNA levels were significantly elevated in patients with chronic pain, presumably as a consequence of neovascularization and chronic inflammation. Smoking habits were found to have a negative dose-dependent effect on the transcript levels of MMP-3 and MMP-13 and a positive correlation with pain intensity, suggesting an unfavorable role for smoking in the regression process of herniated disc fragments. Our findings provide evidence of the molecular portrait of MMPs and ADAMTS-4 in lumbar ID herniation, as well as of its association with the clinicopathological profile of the patients included in this study, reinforcing the hypothesis of MMPs involvement in the natural history of ID herniation. However, further studies are necessary to elucidate the exact role of MMPs in the resorption process of herniated lumbar discs.

Hereditary disorders of connective tissue: a guide to the emerging differential diagnosis

PURPOSE

To create a practical desk reference for clinicians focused on the differential diagnosis of individuals presenting with features that suggest an inherited disorder of connective tissue.

METHODS

We searched the medical literature for distinct clinical entities that shared clinical features with Marfan syndrome and other classical inherited disorders of connective tissue.

RESULTS

Thirty-six distinct heritable disorders of connective tissue were identified that have overlapping features. These disorders were organized into two matrices according to clinical characteristics and according to causative genes.

CONCLUSIONS

A broad differential diagnosis is emerging for individuals presenting with features suggestive of altered connective tissue. Recent advances in molecular genetics have aided in the delineation of these disorders.

Endoplasmic reticulum stress inhibits collagen synthesis independent of collagen-modifying enzymes in different chondrocyte populations and dermal fibroblasts

Chondrocytes respond to glucose deprivation with a decreased collagen synthesis due to disruption of a proper functioning of the endoplasmic reticulum (ER): ER stress. Since the mechanisms involved in the decreased synthesis are unknown, we have investigated whether chaperones and collagen-modifying enzymes are affected by glucose deprivation. Chondrocytes obtained from nucleus pulposus, annulus fibrosus, articular cartilage, and meniscus and dermal fibroblasts were cultured under control conditions or exposed to the ER stress-inducing treatments of tunicamycin addition or glucose withdrawal. Both treatments resulted in an up-regulation of the gene expression of the ER stress markers in all cell types, but dermal fibroblasts showed a delayed response to glucose deprivation. Collagen gene expression was down-regulated, and less collagen protein was present in the cells under both ER stress-inducing conditions. The expression levels of the prolyl 4-hydroxylases were either not affected (P4ha3) or increased (P4ha1 and P4ha2), the levels of the lysyl hydroxylases decreased, and the N-propeptidase Adamts2 decreased. Both treatments induced apoptosis. Chondrocytes respond more quickly to glucose deprivation, but it appears that chondrocytes can cope better with tunicamycin-induced ER stress than fibroblasts. Although collagen synthesis was inhibited by the treatments, some collagen-modifying enzymes and chaperones were up-regulated, suggesting that there is no causal relation between them.

Fell-Muir Lecture: Metalloproteinases: from demolition squad to master regulators

Two families of the Metzincin clan of metalloproteinases, the matrix metalloproteinases and the disintegrin metalloproteinases have attracted much attention as important effectors of cellular interactions with their environment. They appear to play significant roles in the modulation of components of the extracellular matrix, matrix and cell receptors, as well as the cytokines and growth factors and their receptors. Such functions at the 'cutting edge' of cell biology puts these enzymes in pivotal roles in the orchestration of the rapid response of cells to their environment, acting as key switches between different signalling pathways. Inevitably such enzymes should be regarded as suitable targets for therapeutic approaches to many diseases where such pathways become dysregulated. A major challenge to the development of direct inhibitors of catalysis has been the broad structural similarity of the Metzincin catalytic site. More detailed knowledge of active site structures has helped to some extent to resolve the development of more specific chemical inhibitors and selected enzymes are now being targeted. An alternative strategy is the consideration of the role of the extracatalytic domains that are determinants of specificity at a variety of levels. Dissecting the relationships between structure and function of these interaction sites is allowing the development of new approaches to inhibition of enzyme function. Antibodies are proving useful tools in this respect and may pave the way to a novel biologics approach to disease therapy.

Ectopia lentis in a consanguineous pakistani family and a novel locus on chromosome 8q

OBJECTIVE

To investigate the genetic basis and molecular characteristics of the isolated form of ectopia lentis.

METHODS

We ascertained a consanguineous Pakistani family with multiple individuals with ectopia lentis. All affected as well as unaffected members with isolated ectopia lentis underwent detailed ophthalmologic and medical examination. Blood samples were collected and DNA was extracted. A genome-wide scan was completed with 382 polymorphic microsatellite markers, and logarithm of odds (LOD) scores were calculated.

RESULTS

Maximum 2-point LOD scores of 5.68 and 2.88 at theta = 0 were obtained for markers D8S285 and D8S260, respectively, during the genome-wide scan. Additional microsatellite markers refined the disease locus to a 16.96-cM (14.07-Mb) interval flanked by D8S1737 proximally and D8S1117 distally.

CONCLUSIONS

We report on a new locus for nonsyndromic autosomal recessive ectopia lentis on chromosome 8q11.23-q13.2 in a consanguineous Pakistani family. Clinical Relevance Identification of genetic loci and genes involved in ectopia lentis will enhance our understanding of the disease at a molecular level, leading to better genetic counseling and family screening and possible future development of better treatment.

Granulin-epithelin precursor binds directly to ADAMTS-7 and ADAMTS-12 and inhibits their degradation of cartilage oligomeric matrix protein

OBJECTIVE

To determine 1) whether a protein interaction network exists between granulin-epithelin precursor (GEP), ADAMTS-7/ADAMTS-12, and cartilage oligomeric matrix protein (COMP); 2) whether GEP interferes with the interactions between ADAMTS-7/ADAMTS-12 metalloproteinases and COMP substrate, including the cleavage of COMP; 3) whether GEP affects tumor necrosis factor alpha (TNFalpha)-mediated induction of ADAMTS-7/ADAMTS-12 expression and COMP degradation; and 4) whether GEP levels are altered during the progression of arthritis.

METHODS

Yeast two-hybrid, in vitro glutathione S-transferase pull-down, and coimmunoprecipitation assays were used to 1) examine the interactions between GEP, ADAMTS-7/ADAMTS-12, and COMP, and 2) map the binding sites required for the interactions between GEP and ADAMTS-7/ADAMTS-12. Immunofluorescence cell staining was performed to visualize the subcellular localization of GEP and ADAMTS-7/ADAMTS-12. An in vitro digestion assay was employed to determine whether GEP inhibits ADAMTS-7/ADAMTS-12-mediated digestion of COMP. The role of GEP in inhibiting TNFalpha-induced ADAMTS-7/ADAMTS-12 expression and COMP degradation in cartilage explants was also analyzed.

RESULTS

GEP bound directly to ADAMTS-7 and ADAMTS-12 in vitro and in chondrocytes, and the 4 C-terminal thrombospondin motifs of ADAMTS-7/ADAMTS-12 and each granulin unit of GEP mediated their interactions. Additionally, GEP colocalized with ADAMTS-7 and ADAMTS-12 on the cell surface of chondrocytes. More importantly, GEP inhibited COMP degradation by ADAMTS-7/ADAMTS-12 in a dose-dependent manner through 1) competitive inhibition through direct protein-protein interactions with ADAMTS-7/ADAMTS-12 and COMP, and 2) inhibition of TNFalpha-induced ADAMTS-7/ADAMTS-12 expression. Furthermore, GEP levels were significantly elevated in patients with either osteoarthritis or rheumatoid arthritis.

CONCLUSION

Our observations demonstrate a novel protein-protein interaction network between GEP, ADAMTS-7/ADAMTS-12, and COMP. Furthermore, GEP is a novel specific inhibitor of ADAMTS-7/ADAMTS-12-mediated COMP degradation and may play a significant role in preventing the destruction of joint cartilage in arthritis.

[Angiogenesis in cartilage tumors]

In contrast to normal cartilage, which is avascular, angiogenesis is characteristic of cartilage tumors. In this review, we outline the basic principles of angiogenesis with regard to recent findings on differential morphological and molecular aspects of angiogenesis in cartilage tumors, including enchondromas, conventional chondrosarcomas and dedifferentiated chondrosarcomas. Furthermore, we describe the effects of hypoxia and interleukin-1β on angiogenic signaling in chondrosarcoma cells.

Androgen regulates ADAMTS15 gene expression in prostate cancer cells

Prostate cancer is a major cause of mortality, largely as a consequence of metastases and transformation to androgen-independent growth. Metalloproteinases are implicated in cancer progression. A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) are expressed in prostate cancer cells, with ADAMTS-1 and ADAMTS-15 being the most abundant. ADAMTS-15 but not ADAMTS-1 expression was downregulated by androgen in LNCaP prostate cancer cells, possibly through androgen response elements associated with the gene. ADAMTS-15 expression is predictive for survival in breast cancer, and the situation may be similar in prostate cancer, as androgen independence is usually due to aberrant signaling through its receptor.

ADAMTS proteases: key roles in atherosclerosis?

The ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) proteases are secreted enzymes that regulate extracellular matrix turnover by degrading specific matrix components. Roles for the proteases in inflammation and atherosclerosis have been suggested by a number of recent studies, and the role of ADAMTS-4 and -5 in the breakdown of aggrecan and subsequent degradation of cartilage during osteoarthritis has also been established. The ability of the ADAMTS proteases to degrade versican, the primary proteoglycan in the vasculature, is thought to be central to any hypothesized role for the proteases in atherosclerosis. In this review, we introduce the structure and function of the ADAMTS family of proteases and review the literature that links them with inflammation and atherosclerosis.

O-fucosylation of thrombospondin type 1 repeats restricts epithelial to mesenchymal transition (EMT) and maintains epiblast pluripotency during mouse gastrulation

Thrombospondin type 1 repeat (TSR) superfamily members regulate diverse biological activities ranging from cell motility to inhibition of angiogenesis. In this study, we verified that mouse protein O-fucosyltransferase-2 (POFUT2) specifically adds O-fucose to TSRs. Using two Pofut2 gene-trap lines, we demonstrated that O-fucosylation of TSRs was essential for restricting epithelial to mesenchymal transition in the primitive streak, correct patterning of mesoderm, and localization of the definitive endoderm. Although Pofut2 mutant embryos established anterior/posterior polarity, they underwent extensive mesoderm differentiation at the expense of maintaining epiblast pluripotency. Moreover, mesoderm differentiation was biased towards the vascular endothelial cell lineage. Localization of Foxa2 and Cer1 expressing cells within the interior of Pofut2 mutant embryos suggested that POFUT2 activity was also required for the displacement of the primitive endoderm by definitive endoderm. Notably, Nodal, BMP4, Fgf8, and Wnt3 expression were markedly elevated and expanded in Pofut2 mutants, providing evidence that O-fucose modification of TSRs was essential for modulation of growth factor signaling during gastrulation. The ability of Pofut2 mutant embryos to form teratomas comprised of tissues from all three germ layer origins suggested that defects in Pofut2 mutant embryos resulted from abnormalities in the extracellular environment. This prediction is consistent with the observation that POFUT2 targets are constitutive components of the extracellular matrix (ECM) or associate with the ECM. For this reason, the Pofut2 mutants represent a valuable tool for studying the role of O-fucosylation in ECM synthesis and remodeling, and will be a valuable model to study how post-translational modification of ECM components regulates the formation of tissue boundaries, cell movements, and signaling.