A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) cleaves Reelin in an isoform-dependent manner

Reelin is a glycoprotein essential for brain development and functions. Reelin is subject to specific proteolysis at two distinct (N-t and C-t) sites, and these cleavages significantly diminish Reelin activity. The decrease of Reelin activity is detrimental for brain function, but the protease that catalyzes specific cleavage of Reelin remains elusive. Here we found that a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) cleaves Reelin in an isoform-specific manner. Among ADAMTS-4 isoforms, p50 cleaves the N-t site only, while p75 cleaves both sites. This is the first report identifying a protease that can specifically cleave Reelin.     

A disintegrin and metalloproteinase with thrombospondin motif 1 (ADAMTS1) expression increases in acute aortic dissection

Acute aortic dissection (AAD) is a life-threatening cardiovascular disease caused by progressive medial degeneration of the aortic wall. A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) is a recently identified extracellular metalloproteinase participating in the development of vascular disease, such as atherosclerosis. In the present study, we found that ADAMTS1 was significantly elevated in blood samples from AAD patients compared with patients with acute myocardial infarction and healthy volunteers. Based on these findings, we established an AAD model by infusing angiotensin II in older mice. AAD was successfully developed in aorta tissues, with an incidence of 42% after 14 days in the angiotensin II group. Macrophage and neutrophil infiltration was observed in the media of the aorta, and ADAMTS1 overexpression was found in the aorta by Western blot and immunohistochemistry. Double immunofluorescence staining showed the expression of ADAMTS1 in macrophages and neutrophils. Consistent with the upregulation of ADAMTS1 in aortic dissection tissues, versican (a proteoglycan substrate of ADAMTS1) was degraded significantly more in these tissues than in control aortic tissues. These data suggest that the increased expression of ADAMTS1 protein in macrophages and neutrophils that infiltrated aortic tissues may promote the progression of AAD by degrading versican.     

Cleavage of cartilage oligomeric matrix protein (thrombospondin-5) by matrix metalloproteinases and a disintegrin and metalloproteinase with thrombospondin motifs.

Cartilage oligomeric matrix protein (COMP) is a pentameric glycoprotein present in cartilage, tendon and ligament. Fragments of the molecule are present in the diseased cartilage, synovial fluid and serum of patients with knee injuries, osteoarthritis and rheumatoid arthritis. Although COMP is a substrate for several matrix metalloproteinases (MMPs), the enzymes responsible for COMP degradation in vivo have yet to be identified. In this study we utilised well-established bovine cartilage culture models to examine IL-1alpha-stimulated COMP proteolysis in the presence and absence of MMP inhibitors. COMP was released from bovine nasal cartilage, in response to IL-1alpha, at an intermediate time between proteoglycans and type II collagen, when soluble MMP levels in the culture medium were undetectable. The major fragment of COMP released following IL-1alpha-stimulation migrated with an apparent molecular mass of approximately 110 kDa (Fragment-110) and co-migrated with both the major fragment present in human arthritic synovial fluid samples and the product of COMP cleavage by purified MMP-9. However, the broad-spectrum MMP and ADAM inhibitor BB94 only partially inhibited the formation of Fragment-110 and failed to inhibit COMP release significantly. Therefore the results of these studies indicate a role for proteinases other than MMPs in the degradation of COMP in bovine cartilage. It was further demonstrated that purified COMP was cleaved by ADAMTS-4, but not ADAMTS-1 or -5, to yield a fragment which co-migrated with Fragment-110. Therefore this is the first demonstration of COMP as a substrate for ADAMTS-4, although it remains to be determined whether this enzyme plays a role in COMP degradation in vivo.     

Identified a disintegrin and metalloproteinase with thrombospondin motifs 6 serve as a novel gastric cancer prognostic biomarker by bioinformatics analysis

Objective: We aimed to explore the prognostic value of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) genes in gastric cancer (GC). Methods: The RNA-sequencing (RNA-seq) expression data for 351 GC patients and other relevant clinical data were acquired from The Cancer Genome Atlas (TCGA). Survival analysis and a genome-wide gene set enrichment analysis (GSEA) were performed to define the underlying molecular value of the ADAMTS genes in GC development. Besides, qRT-PCR and immunohistochemistry were all employed to validate the relationship between the expression of these genes and GC patient prognosis. Results: The Log rank test with both Cox regression and Kaplan–Meier survival analyses showed that ADAMTS6 expression profile correlated with the GC patients clinical outcome. Patients with a high expression of ADAMTS6 were associated with poor overall survival (OS). Comprehensive survival analysis of the ADAMTS genes suggests that ADAMTS6 might be an independent predictive factor for the OS in patients with GC. Besides, GSEA demonstrated that ADAMTS6 might be involved in multiple biological processes and pathways, such as the vascular endothelial growth factor A (VEGFA), kirsten rat sarcoma viral oncogene (KRAS), tumor protein P53, c-Jun N-terminal kinase (JNK), cadherin (CDH1) or tumor necrosis factor (TNF) pathways. It was also confirmed by immunohistochemistry and qRT-PCR that ADAMTS6 is highly expressed in GC, which may be related to the prognosis of GC patients. Conclusion: In summary, our study demonstrated that ADAMTS6 gene could be used as a potential molecular marker for GC prognosis.     

A disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motifs: the ADAMTS family

ADAMTS proteases are complex secreted enzymes containing a prometalloprotease domain of the reprolysin type attached to an ancillary domain with a highly conserved structure that includes at least one thrombospondin type 1 repeat. Known functions of ADAMTS proteases include processing of procollagens and von Willebrand factor as well as catabolism of aggrecan, versican and brevican. They have been demonstrated to have important roles in connective tissue organization, coagulation, inflammation, arthritis, angiogenesis and cell migration. ADAMTS can be grouped into distinct clades within which there is conservation of modular organization, protein sequence, gene structure and possibly, of substrate preference. ADAMTS proteases are synthesized as zymogens, with constitutive proprotein convertase removal of the propeptide occurring prior to secretion. Their enzymatic specificity is heavily influenced by their ancillary domain, which plays a critical role in directing these enzymes to their substrates, the cell surface and the extracellular matrix.     

Screening of potential a disintegrin and metalloproteinase with thrombospondin motifs-4 inhibitors using a collagen model fluorescence resonance energy transfer substrate

The major components of the cartilage extracellular matrix are type II collagen and aggrecan. Type II collagen provides cartilage with its tensile strength, whereas the water-binding capacity of aggrecan provides compressibility and elasticity. Aggrecan breakdown leads to an increase in proteolytic susceptibility of articular collagen; hence, aggrecan may also have a protective effect on type II collagen. Given their role in aggrecan degradation and differing substrate specificity profiles, the pursuit of inhibitors for both aggrecanase 1 (a disintegrin and metalloproteinase with thrombospondin motifs-4 [ADAMTS-4]) and aggrecanase 2 (ADAMTS-5) is desirable. We previously described collagen model fluorescence resonance energy transfer (FRET) substrates for aggrecan-degrading members of the ADAMTS family. These FRET substrate assays are also fully compatible with multiwell formats. In the current study, a collagen model FRET substrate was examined for inhibitor screening of ADAMTS-4. ADAMTS-4 was screened against a small compound library (n=960) with known pharmacological activity. Five compounds that inhibited ADAMTS-4>60% at a concentration of 1muM were identified. A secondary screen using reversed-phase high-performance liquid chromatography (RP-HPLC) was developed and performed for verification of the five potential inhibitors. Ultimately, piceatannol was confirmed as a novel inhibitor of ADAMTS-4, with an IC(50) value of 1muM. Because the collagen model FRET substrates have distinct conformational features that may interact with protease secondary substrate sites (exosites), nonactive site-binding inhibitors can be identified via this approach. Selective inhibitors for ADAMTS-4 would allow a more definitive evaluation of this protease in osteoarthritis and also represent a potential next generation in metalloproteinase therapeutics.     

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) family

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that have diverse roles in tissue morphogenesis and patho-physiological remodeling, in inflammation and in vascular biology. The human family includes 19 members that can be sub-grouped on the basis of their known substrates, namely the aggrecanases or proteoglycanases (ADAMTS1, 4, 5, 8, 9, 15 and 20), the procollagen N-propeptidases (ADAMTS2, 3 and 14), the cartilage oligomeric matrix protein-cleaving enzymes (ADAMTS7 and 12), the von-Willebrand Factor proteinase (ADAMTS13) and a group of orphan enzymes (ADAMTS6, 10, 16, 17, 18 and 19). Control of the structure and function of the extracellular matrix (ECM) is a central theme of the biology of the ADAMTS, as exemplified by the actions of the procollagen-N-propeptidases in collagen fibril assembly and of the aggrecanases in the cleavage or modification of ECM proteoglycans. Defects in certain family members give rise to inherited genetic disorders, while the aberrant expression or function of others is associated with arthritis, cancer and cardiovascular disease. In particular, ADAMTS4 and 5 have emerged as therapeutic targets in arthritis. Multiple ADAMTSs from different sub-groupings exert either positive or negative effects on tumorigenesis and metastasis, with both metalloproteinase-dependent and -independent actions known to occur. The basic ADAMTS structure comprises a metalloproteinase catalytic domain and a carboxy-terminal ancillary domain, the latter determining substrate specificity and the localization of the protease and its interaction partners; ancillary domains probably also have independent biological functions. Focusing primarily on the aggrecanases and proteoglycanases, this review provides a perspective on the evolution of the ADAMTS family, their links with developmental and disease mechanisms, and key questions for the future.     

A disintegrin and metalloproteinase (ADAM)-mediated ectodomain shedding of ADAM10

A disintegrin and metalloproteinase (ADAM) 10 is a type I transmembrane glycoprotein responsible for the ectodomain shedding of a range of proteins including the amyloid precursor protein implicated in Alzheimer's disease. In this study we demonstrate that ADAM10 itself is subject to shedding by one or more ADAMs. Expression of epitope-tagged wild-type ADAM10 in SH-SY5Y cells enabled the detection of a soluble ectodomain in conditioned medium. Shedding of the ADAM10 ectodomain was inhibited by a known ADAM inhibitor with a reciprocal accumulation of the full-length mature protein in both cell lysates and extracellular membrane vesicles. Shedding was also stimulated by phorbol ester treatment of cells. A glycosylphosphatidylinositol-anchored form of ADAM10 lacking the cytosolic, transmembrane and α-helical juxtamembrane regions of the wild-type protein was shed in a similar manner. Furthermore, a truncated soluble ADAM10 construct, although correctly post-translationally processed and catalytically active against a synthetic peptide substrate, was incapable of shedding cell-associated amyloid precursor protein. Finally, we show that ADAM9 is, at least in part, responsible for the ectodomain shedding of ADAM10. In conclusion, this is a new mechanism by which levels of ADAM10 are regulated and may have implications in a range of human diseases including Alzheimer's disease.     

ADAMTS4 (aggrecanase-1) activation on the cell surface involves C-terminal cleavage by glycosylphosphatidyl inositol-anchored membrane type 4-matrix metalloproteinase and binding of the activated proteinase to chondroitin sulfate and heparan sulfate on syndecan-1

C-terminal truncation of ADAMTS-4 from the p68 form to the p53 form is required for activation of its capacity to cleave the Glu(373)-Ala(374) interglobular domain bond of aggrecan. In transfected human chondrosarcoma cells, this process is not autoproteolytic because the same products form with an inactive mutant of ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin-like motif 4) and truncation is completely blocked by tissue inhibitor of metalloproteinase-1. Instead, activation can be mediated by glycosylphosphatidyl inositol-anchored membrane type 4-matrix metalloproteinase (MT4-MMP, MMP-17) because co-transfection with the active form of MT4-MMP markedly enhanced activation, whereas an inactive mutant of MT4-MMP was ineffective. Treatment of co-transfected cells with phosphatidylinositol-specific phospholipase C liberated the complex of MT4-MMP and p68 ADAMTS4 from the cell membrane, but the p53 ADAMTS4 remained associated. Specific glycosaminoglycan lyase digestions, followed by product analyses using fluorescence-assisted carbohydrate electrophoresis and immunoprecipitation experiments, showed that the p53 form is associated with syndecan-1 through both chondroitin sulfate and heparan sulfate. We conclude that ADAMTS-4 activation in this cell system involves the coordinated activity of both glycosylphosphatidyl inositol-anchored MT4-MMP and the proteoglycan form of syndecan-1 on the cell surface.     

microRNA-1274a, a modulator of sorafenib induced a disintegrin and metalloproteinase 9 (ADAM9) down-regulation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a complex and heterogeneous tumor with poor prognosis. Sorafenib, a multikinase inhibitor, has been widely used to treat patients with advanced HCC in clinic. We postulated that microRNAs (miRNA) might be involved in HCC target-chemotherapy with sorafenib. MiRNA profile of HepG2 was evaluated after cells were treated with vehicle or sorafenib and alterations in miRNA expression occurred with 14 miRNAs. MiR-1274a, which is up-regulated by sorafenib, could significantly repress expression of ADAM9, a protease that is involved in sorafenib target-therapy of HCC, in HCC cells. Taken together, our data emphasizes a new miRNA-based mechanism of sorafenib antitumor therapy.     

Requirement for sialic acid on neutrophils in a GMP-140 (PADGEM) mediated adhesive interaction with activated platelets.

Platelet GMP-140, along with ELAM-1 and gp90MEL, comprise the LEC-CAM family of cell-cell adhesion proteins. The three proteins demonstrate a highly related domain organization, which includes an extracellular calcium-type lectin motif. gp90MEL, a lymphocyte homing receptor, mediates lymphocyte attachment to high endothelial venules of lymph nodes through recognition of a sialylated ligand on the endothelial cells. The rosetting of neutrophils or promyelocytic HL60 cells by activated platelets is mediated by GMP-140 on the platelets. We show here that treatment of neutrophils or HL60 cells with 3 broad spectrum sialidases completely prevents rosetting. However, the Newcastle disease virus sialidase, an enzyme specific for alpha 2,3 and alpha 2,8 linkages of sialic acid does not affect rosetting of HL60 cells. These results indicate that the ligand for GMP-140 requires sialic acid and suggest that an alpha 2,6 linkage may be critical.     

Structural Requirement for Clusters to be Reconstituted with the FeMoCo-Deficient Molybdenum-Iron Protein

By incubating the reduced MoFe protein from Azotobacter vinelandii with O-phenanthroline under air and chromatographying the incubated solution on Sephadex G-25 column, inactive MoFe protein could be obtained. Its acetylene-reduction activity was remarkably recovered not only by incubation with the reconstituent solution composed of KMnO4, ferric homoeitrate, Na2S and dithiothreitol, but also with a mixture of 4Fe : 4S clusters and another cluster which had two structure units of 1Mo : 3Fe : 4S-bridged by three -OCH3 at the Mo atoms. Neither the reconstituent solution nor the mixture could reactivate apo-MoFe proteins from the mutants deleting nile and nifH genes and from the mutant UW45, which could be reactivated by the FeMoeo extracted from the MoFe protein. The results indicated that the FeMoeo-defieient MoFe proteins from these mutants seemed to be reconstituted only by the clusters which were probably structures only similar to FeMoeo. The partially metalloeluster-deficient MoFe protein could be reconstituted by the clusters with a certain kind of structure and composition; and was changed into different nitrogenase proteins with the ability to fix nitrogen.     

Formation of a stable complex of thrombin and the secreted platelet protein glycoprotein G (thrombin-sensitive protein, thrombospondin) by thiol-disulfide exchange

When 125I-labeled thrombin was incubated with washed human platelets or with the supernatant solution of activated platelets, it formed a NaDodSO4-stable complex of apparent mass greater than 450 000 daltons. Formation of the complex was temperature dependent; with 20 nM thrombin incubated with the supernatant solution of ionophore-activated platelets, the initial rate of formation of the stable complex was 1 nM thrombin/min at 37 degrees C, 50 times the rate at 22 degrees C. Thrombin with all free amino groups methylated was still reactive. Active-site-blocked thrombin formed the complex only slowly. The complex that formed with active thrombin was not dissociated by hydroxylamine in urea. Reduction with 2-mercaptoethanol dissociated the complex, and its formation was blocked by the sulfhydryl-blocking agents iodoacetamide and 4,4'-dithiodipyridine. The complex was thus unlike those of thrombin and alpha 2-macroglobulin or antithrombin III, but it had characteristics of a disulfide-linked complex. Of the secreted proteins, albumin and glycoprotein G adhered to an activated thiol-Sepharose column, indicating that they contained free thiol groups. Purified glycoprotein G and thrombin formed a complex similar to the complex formed when thrombin was incubated with the supernatant solution of activated platelets. The purified glycoprotein bound 2.6 mol of radioactive N-ethylmaleimide/mol of protein, indicating three sulfhydryl groups per mole. After reacting with purified glycoprotein G, thrombin developed a new sulfhydryl group. It is concluded that glycoprotein G (thrombin-sensitive protein, thrombospondin) and thrombin form a dissociable complex that leads to a covalent complex by thiol-disulfide exchange of a thiol group on glycoprotein G and a disulfide on thrombin.     

Autolysis at the disintegrin domain of patagonfibrase,a metalloproteinase from Philodryas patagoniensis (Patagonia Green Racer; Dipsadidae) venom

Patagonfibrase is a 57.5-kDa hemorrhagic metalloproteinase isolated from the venom of Philodryas patagoniensis (Patagonia Green Racer), a South American rear-fanged snake. Herein we demonstrate that patagonfibrase undergoes autolysis at its pH optimum (7.5) and at 37 °C, primarily producing a ∼ 32.6 kDa fragment composed of disintegrin-like and cysteine-rich domains, as identified by mass spectrometry and N-terminal sequencing. The autolysis site for production of this fragment is similar to that observed for metalloproteinases from front-fanged Viperidae snake venoms. In the presence of Ca²⁺, patagonfibrase was only partially autolysed, giving rise mainly to one fragment of ∼ 52.2 kDa. In addition, calcium markedly enhanced the azocaseinolytic activity of patagonfibrase. Our findings contribute to the understanding of the structural and mechanistic bases of this family of metalloenzymes that are widely distributed among snake venoms, demonstrating that important post-translational modifications such as proteolysis can also contribute to the diversity and complexity of proteins found in rear-fanged snake venoms.     

Unsaturated fatty acids drive disintegrin and metalloproteinase (ADAM)-dependent cell adhesion, proliferation, and migration by modulating membrane fluidity

The disintegrin-metalloproteinases ADAM10 and ADAM17 mediate the release of several cell signaling molecules and cell adhesion molecules such as vascular endothelial cadherin or L-selectin affecting endothelial permeability and leukocyte transmigration. Dysregulation of ADAM activity may contribute to the pathogenesis of vascular diseases, but the mechanisms underlying the control of ADAM functions are still incompletely understood. Atherosclerosis is characterized by lipid plaque formation and local accumulation of unsaturated free fatty acids (FFA). Here, we show that unsaturated FFA increase ADAM-mediated substrate cleavage. We demonstrate that these alterations are not due to genuine changes in enzyme activity, but correlate with changes in membrane fluidity as revealed by measurement of 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and fluorescence recovery after photobleaching analyses. ELISA and immunoblot experiments conducted with granulocytes, endothelial cells, and keratinocytes revealed rapid increase of ectodomain shedding of ADAM10 and ADAM17 substrates upon membrane fluidization. Large amounts of unsaturated FFA may be liberated from cholesteryl esters in LDL that is entrapped in atherosclerotic lesions. Incubation of cells with thus modified LDL resulted in rapid cleavage of ADAM substrates with corresponding functional consequences on cell proliferation, cell migration, and endothelial permeability, events of high significance in atherogenesis. We propose that FFA represent critical regulators of ADAM function that may assume relevance in many biological settings through their influence on mobility of enzyme and substrate in lipid bilayers.