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PubMed1999

Localization of ADAM10 and Notch receptors in bone.

In Drosophila melanogaster, the role of the metallodisintegrin, Kuzbanian (kuz), is thought to involve activation of the Drosophila Notch receptor that plays a role in cell-fate determination during neurogenesis and myoblast differentiation. To understand the possible function(s) of a-disintegrin and metalloproteinase (ADAM10), the mammalian ortholog of kuz, in the skeleton, we studied its expression as well as the messenger RNA (mRNA) encoding one candidate substrate, the mammalian Notch2 receptor in bone, bone cells, and cartilage. In sections of neonatal rat tibiae, ADAM10 is expressed in specific regions of articular cartilage and metaphyseal bone. Expression of ADAM10 in articular cartilage occurs predominantly in superficial chondrocytes and becomes more sporadic with increasing distance from the articular surface. In bone, ADAM10 is expressed by periosteal cells, osteoblasts, and osteocytes at locations of active bone formation. Osteoclasts did not express ADAM10. Notch2 mRNA expression was not detectable in superficial chondrocytes. However it colocalized at all sites of ADAM10 expression in bone cells. In vitro, both primary human osteoblasts and osteoblast cell lines expressed a single 4.5 kb and 7.5 kb transcript of ADAM10 and the Notch2 receptor homolog, respectively. Subcellular localization of the ADAM10 protein in MG-63 cells was determined using immunofluorescent techniques. These observations showed clearly that the ADAM10 protein was expressed in the trans-Golgi network and on the plasma membrane. Western blot analysis of fractionated cells showed that, in the plasma membrane fraction, the previously characterized 58 kDa and 56 kDa isoforms were present, whereas, in the trans-Golgi network, the ADAM10 protein was present in several additional bands, possibly indicative of further interdomain processing of the ADAM10 protein. The metallodisintegrins (ADAMs) have several putative functions, including modulation of cell adhesion, membrane-associated proteolysis, and cell-cell signaling. These observations suggest that, in bone but not cartilage, ADAM10 has catalytic activity within the transGolgi network and may play a role in the activation of Notch receptor homologs. This implicates ADAM10 in cell-fate determination of osteoblast progenitor cells, possibly during skeletal development and normal bone remodeling. Plasma-membrane-associated ADAM10 may confer alternative functions.

Amino Acid Sequence↗

PubMed1997

SUP-17, a Caenorhabditis elegans ADAM protein related to Drosophila KUZBANIAN, and its role in LIN-12/NOTCH signalling.

LIN-12/NOTCH proteins mediate cell-cell interactions that specify cell fates. Previous work suggested that sup-17 facilitates lin-12 signalling in Caenorhabditis elegans. Here, we show that sup-17 encodes a member of the ADAM family of metalloproteases. SUP-17 is highly similar to Drosophila KUZBANIAN, which functions in Drosophila neurogenesis, and the vertebrate ADAM10 protein. Furthermore, we show by genetic analysis that the extracellular domain of LIN-12 appears to be necessary for sup-17 to facilitate lin-12 signalling and that sup-17 does not act downstream of lin-12. Finally, we show by cell ablation experiments that sup-17 can act cell autonomously to facilitate lin-12 activity. We discuss the implications of our observations for LIN-12/NOTCH signalling and how our results complement and extend results obtained from genetic analysis of kuz in Drosophila.

ADAM Proteins↗

PubMed2003

Variation at the ADAM10 gene locus is not associated with Creutzfeldt-Jakob disease.

Prion diseases are characterized by the accumulation in the brain of a misfolded and protease-resistant form of the prion protein (PrP(c)). PrP(c) contains an amyloidogenic, neurotoxic sequence that is essential for conversion into PrP(Sc), the pathological isoform. During normal processing, PrP(c) is cleaved at a site within this sequence, and this cleavage is thought to destroy the amyloidogenic potential of the protein. ADAM10, a disintegrin and metalloprotease that plays a key role in the pathogenesis of Alzheimer's disease, was recently shown to use PrP(c) as a substrate. We investigated whether variability in the ADAM10 gene could contribute to the pathogenesis of Creutzfeldt-Jakob disease (CJD), by analyzing a single nucleotide polymorphism (SNP) within ADAM10, as a genetic marker potentially in linkage disequilibrium with a functional polymorphism, in patients with sporadic or variant CJD. We observed no significant differences in ADAM10 genotype or allele frequencies between CJD patients and healthy individuals. Moreover, the distribution of ADAM10 SNP genotypes and alleles did not differ between groups of patients based on genotype at the polymorphic codon 129 of the prion protein gene--the sole major genetic risk factor for CJD identified to date. Our data indicate that ADAM10 is unlikely to confer genetic susceptibility to CJD.

ADAM Proteins↗

PubMed2005

Elevated CXCL16 expression by synovial macrophages recruits memory T cells into rheumatoid joints.

OBJECTIVE: Directional migration of leukocytes is orchestrated by the regulated expression of chemokine receptors and their ligands. The receptor CXCR6 is abundantly expressed by Th1-polarized effector/memory lymphocytes accumulating at inflammatory sites. This study was undertaken to examine the presence of CXCR6+ T cells and of CXCL16, the only ligand for CXCR6, in the joints of patients with rheumatoid arthritis (RA). METHODS: Flow cytometry analysis of the expression of CXCR6 by peripheral blood and synovial fluid (SF) T cells. In addition, by performing conventional and real-time reverse transcriptase-polymerase chain reaction, immunohistochemistry, and enzyme-linked immunosorbent assay, we determined the expression of CXCL16 and its protease ADAM-10 within synovium and by cultured macrophages. SF T cell migration was studied with the Transwell system. RESULTS: Accumulation of CXCR6+ T cells within RA SF coincided with highly elevated levels of CXCL16+ macrophages. In vitro studies revealed that monocytes started to express CXCL16 upon differentiation into macrophages, and that RA SF and tumor necrosis factor (TNF) enhanced CXCL16 expression. Moreover, RA patients responding to anti-TNF therapy showed a strongly decreased CXCL16 expression, whereas nonresponding patients did not. Interestingly, ADAM-10, a recently identified protease of CXCL16, was abundantly expressed by CXCL16+ macrophages in vitro and in RA in vivo, which resulted in increased levels of cleaved CXCL16 in RA SF relative to controls. Finally, CXCR6+ T cells from RA SF were attracted by CXCL16. CONCLUSION: These data provide evidence that enhanced production of CXCL16 in RA synovia leads to recruitment of CXCR6+ memory T cells, thereby contributing to the inflammatory cascade associated with RA pathology.

ADAM Proteins↗

PubMed2003

ADAM-10 and ADAM-17 in the inflamed human CNS.

Inflammatory demyelinating disorders of the CNS, such as multiple sclerosis (MS), are mediated, at least in part, by various cytokines and proteases. In the present study, we investigated the expression of A disintegrin and metalloproteinase (ADAM)-17, an important sheddase for various proteins, including tumor necrosis factor-alpha (TNF-alpha), and the p75- and p55-TNF receptors, as well as ADAM-10, a protease implicated in myelin degradation, in post mortem CNS tissue samples from patients with MS, and normal brain tissue (as control) by immunohistochemistry. ADAM-10 was found to be expressed by astrocytes in all MS and control sections studied; however, in some MS sections, perivascular macrophages were determined as an additional cellular source as well. ADAM-17 could be observed exclusively in acute and chronic active MS plaques and localized to invading T lymphocytes. The staining pattern of ADAM-17 in MS plaques was mirrored in distribution and extent by the pattern obtained with an antibody against the p75-TNF-receptor (TNFR-2), whereas TNF-alpha was found to be expressed primarily by perivascular macrophages. In studying cerebrospinal fluid (CSF) samples from MS patients, we were able to detect increased protein levels of ADAM-17 as compared with noninflammatory controls. In addition, increased levels of soluble TNFR-2 could be measured, suggestive of an active shedding process mediated by ADAM-17. The stimulation of peripheral blood mononuclear cells (PBMC) obtained from MS patients and healthy individuals corroborated these findings by revealing expression of ADAM-17 by T lymphocytes and ADAM-10 by macrophages in vitro. Our results indicate that ADAM-10 is expressed constitutively by astrocytes in the normal and inflamed human CNS. In contrast, under inflammatory conditions, ADAM-10, expressed by perivascular macrophages, and ADAM-17, expressed by invading T cells, may actively contribute to the pathogenesis of inflammatory disorders of the CNS.

ADAM Proteins↗

PubMed2006

Interleukin-1alpha stimulates non-amyloidogenic pathway by alpha-secretase (ADAM-10 and ADAM-17) cleavage of APP in human astrocytic cells involving p38 MAP kinase.

Interleukin-1alpha (IL-1alpha) stimulates a disintegrin and metalloproteinase, ADAM-17 synthesis, consistent with activation of the soluble fragment of Amyloid Precursor Protein, APP, (sAPPalpha) in human primary astrocytes. To characterize the mechanism by which IL-1alpha promotes the non-amyloidogenic pathway of APP metabolism, we used U373 MG astrocytoma cells. IL-1alpha significantly increased levels of ADAM-10 and ADAM-17 mRNA in 16 hr. Upregulation of ADAM-17 mRNA by IL-1alpha was more pronounced despite higher basal levels of ADAM-10 mRNA. This pattern was also observed at the protein level with the upregulation of alpha-secretase. RNA interference (RNAi) of ADAM-10 and ADAM-17 inhibited IL-1alpha-stimulated sAPPalpha release and the effect was more pronounced with ADAM-17 RNAi. Concomitantly, the level of sAPPalpha was significantly increased by IL-1alpha in 48 hr; however, IL-1alpha stimulated cell-associated APP levels maximally at 6 h but the induction declined at 48 hr. IL-1alpha treatment of cells for 48 h reduced both intracellular and secreted levels of amyloid-beta, Abeta-40, and Abeta-42 peptides. Multiple MAP kinases (MAPK), including MEK/ERK, p38 kinase, PI3 kinase (PI3K) but not JNK were involved in the regulation of IL-1alpha-stimulated alpha-secretase activity and sAPPalpha release. p38 MAPK seems to be the most proximal of these MAPKs, as it was the earliest to be activated by IL-1alpha and blocking this pathway attenuated activation of IL-1alpha-induced MEK and PI3K pathways. Our data show a complex mechanism of sAPPalpha regulation by IL-1alpha that involves ADAM-10, ADAM-17 and p38 MAPK upstream of MEK and PI3K.

ADAM Proteins↗

PubMed2006

Metalloprotease-induced ectodomain shedding of neural cell adhesion molecule (NCAM).

Transmembrane forms of neural cell adhesion molecule (NCAM140, NCAM180(1)) are key regulators of neuronal development. The extracellular domain of NCAM can occur as a soluble protein in normal brain, and its levels are elevated in neuropsychiatric disorders, such as schizophrenia; however the mechanism of ectodomain release is obscure. Ectodomain shedding of NCAM140, releasing a fragment of 115 kD, was found to be induced in NCAM-transfected L-fibroblasts by the tyrosine phosphatase inhibitor pervanadate, but not phorbol esters. Pervanadate-induced shedding was mediated by a disintegrin metalloprotease (ADAM), regulated by ERK1/2 MAP kinase. In primary cortical neurons, NCAM was shed at high levels, and the metalloprotease inhibitor GM6001 significantly increased NCAM-dependent neurite branching and outgrowth. Moreover, NCAM-dependent neurite outgrowth and branching were inhibited in neurons isolated from a transgenic mouse model of NCAM shedding. These results suggest that regulated metalloprotease-induced ectodomain shedding of NCAM down-regulates neurite branching and neurite outgrowth. Thus, increased levels of soluble NCAM in schizophrenic brain have the potential to impair neuronal connectivity.

ADAM Proteins↗

PubMed1997

Expression of members of a novel membrane linked metalloproteinase family (ADAM) in human articular chondrocytes.

Using resting chondrocytes derived from human articular femoral head and a conditionally immortalised human articular chondrocyte cell line we have studied the expression of members of the novel metalloproteinase/disintegrin family termed ADAM. Using RT-PCR we can detect the expression of ADAM-12 a novel family member isolated from myeloma cells [1]. We also find expression of ADAM 10 a functional metalloproteinase/disintegrin first isolated from bovine brain and ADAM-15 a metallodisintegrin isolated from mammary derived epithelial cells. Northern blotting was used to confirm expression. One main transcript is visible for ADAM-12 whereas both ADAM-10 and ADAM-15 have multiple transcripts indicating possible RNA variants potentially derived from alternative splicing or alternative use of polyadenylation sites. Since chondrocytes are proposed as an important source of metalloproteinase enzymes involved in joint pathology the potential relevance of the expression of these molecules to connective tissue disorders is discussed.

ADAM Proteins↗

PubMed2004

Increased expression of ADAM family members in human breast cancer and breast cancer cell lines.

PURPOSE: ADAMs (A Disintegrin and Metalloprotease) are multifunctional, membrane-bound cell surface glycoproteins, which have numerous functions in cell growth, differentiation, and motility. We wished to investigate the expression of ADAM 9, 10, 12, 15, and in human breast cancer. METHODS: Expression of ADAMs was determined in breast cancer specimens and the corresponding non-neoplastic breast tissue from 24 patients, and in the MCF-7 and MDA-MB 453 breast cancer cell lines via quantitative RT-PCR and immunohistochemistry. The effects of anti-ADAM antibodies on cell proliferation were assessed by measuring DNA-synthesis. RESULTS: Breast cancer tissue samples showed increased mRNA expression of ADAM 9, 12, and 17, whereas ADAM 10 and 15 were not differently expressed. Protein expression was studied by immunohistochemistry. All ADAMs were expressed in MCF-7 and MDA-MB453 cell lines, with the highest expression levels being observed for ADAM 9, 12, and 17. Application of anti-ADAM 15 and anti-ADAM 17 antibodies significantly inhibited the proliferation of both MCF-7 and MDA-MB453 breast cancer cell lines. In contrast, the growth of MCF-7 cells appeared to be stimulated by the administration of anti-ADAM 12 antibody. CONCLUSION: The results of this study suggest that ADAMs are differentially expressed in human breast cancer and are capable of modulating tumour cell growth.

ADAM Proteins↗

PubMed2006

Capsaicin-induced inactivation of sensory neurons promotes a more aggressive gene expression phenotype in breast cancer cells.

Capsaicin-induced inactivation of sensory neurons has been reported to enhance metastasis of a murine breast cancer cell line, specifically enhancing myocardial metastases. Here we characterized changes in gene expression patterns in primary tumors which developed in capsaicin-treated vs. control mice. We identified a small cohort of genes (17) which all showed significant decreases in expression levels. All of the identified genes have been linked to cell growth, differentiation, and/or cancer progression. Three representative genes, Caspase-7 (an executor of apoptosis), ADAM-10 (A Disintegrin and Metalloprotease), and Elk-3 (a transcriptional repressor of the ternary factor subfamily of the Ets factors) were further investigated. All three showed dramatic downregulation at the protein level in primary tumors from capsaicin-treated animals compared with control (vehicle-treated) animals, and their expression was also lost in cell culture. Elk-3 and Caspase-7 were not expressed in vitro in cultured cell lines, suggesting that their expression was induced by the tumor microenvironment. Loss of Caspase-7 expression can be expected to result in loss of function of apoptotic pathways. At first glance, loss of ADAM-10 expression would be expected to result in decreased invasive capability, due to loss of matrix metalloprotease activity. However, just the opposite appears to be true. We found that ADAM-10 actually hydrolyzes Substance P. Specifically ADAM-10 produces the same growth-inhibitory products from Substance P (i.e., SP (1-7)) that Neprilysin does, so that loss of ADAM-10 expression actually results in loss of production of growth inhibitory peptides from Substance P. Similarly, ADAM-10 also efficiently hydrolyzes Calcitonin Gene-Related Peptide, which may act in concert with Substance P. Finally, overactivity of Ets transcriptional suppressor functions has been linked to inhibition of tumorigenesis (e.g., Erf and Mef), and in addition loss of Elk-3 expression might also be be linked to tumorigenesis via loss of its putative anti-inflammatory activities. There is anecdotal evidence in the literature to indicate that the rest of the down-regulated genes may also contribute to development of a more aggressive phenotype in this breast cancer model.

ADAM Proteins↗

PubMed2003

ADAMs: modulators of cell-cell and cell-matrix interactions.

ADAMs contain adhesive and metalloprotease domains. As major ectodomain sheddases, they release a variety of cell-surface proteins, including growth factors, cytokines, cell adhesion molecules and receptors. ADAMs can also cleave and remodel components of the extracellular matrix. Hence, ADAMs are emerging as key modulators of cell-cell and cell-matrix interactions. Important questions, including if and how ADAM adhesive domains promote ADAM protease function, are currently being addressed.

ADAM Proteins↗

PubMed2005

ADAM and Eph: how Ephrin-signaling cells become detached.

Ephrin ligands presented on one cell surface associate with their receptors on the surface of a juxtaposed cell, often resulting in cell-cell repulsion. In this issue of Cell, Janes et al. (2005) show that the ephrin ligand can be proteolytically released from its membrane tether by a complex on the opposing cell composed of the ephrin receptor and an ADAM metalloprotease.

ADAM Proteins↗

PubMed2006

Chemoattractants, extracellular proteases, and the integrated host defense response.

The host response to tissue injury and/or infection is dependent on the action of numerous extracellular proteases. Proteolytic cascades trigger blood clotting, fibrinolysis, and complement activation, while proteases released upon leukocyte degranulation are integral to the processes of inflammation and immunity. Modulation of effector protein activity by proteases provides a critical layer of posttranslational control that enables rapid enzymatic regulation of target proteins. This report reviews the emerging literature describing a novel class of proteolytic targets, leukocyte chemoattractants, and, in particular, chemerin, a dendritic cell and macrophage chemoattractant activated by serine proteases of the coagulation, fibrinolytic, and inflammatory cascades. As chemoattractants are critical for both systemic leukocyte positioning by triggering integrin activation and subsequent recruitment from circulation, and local intratissue leukocyte positioning via chemotaxis, modulation of attractant activities by proteases may have profound effects on the immune response.

ADAM Proteins↗

PubMed2005

The N-terminal cleavage of cellular prion protein in the human brain.

Human brain cellular prion protein (PrP(c)) is cleaved within its highly conserved domain at amino acid 110/111/112. This cleavage generates a highly stable C-terminal fragment (C1). We examined the relative abundance of holo- and truncated PrP(c) in human cerebral cortex and we found important inter-individual variations in the proportion of C1. Neither age nor postmortem interval explain the large variability observed in C1 amount. Interestingly, our results show that high levels of C1 are associated with the presence of the active ADAM 10 suggesting this zinc metalloprotease as a candidate for the cleavage of PrP(c) in the human brain.

ADAM Proteins↗

PubMed2004

Altered processing of the amyloid precursor protein and decreased expression of ADAM 10 by chronic hypoxia in SH-SY5Y: no role for the stress-activated JNK and p38 signalling pathways.

Clinical studies suggest that the incidence of Alzheimer's disease (AD) is increased following an ischaemic or hypoxic episode, such as stroke. Furthermore, levels of the AD-associated amyloid beta-peptides (Abeta) and the amyloid precursor protein (APP) are enhanced in experimental ischaemia. In our previous study [Webster, N.J., Green, K.N., Peers, C., Vaughan, P.F., Altered processing of amyloid precursor protein in the human neuroblastoma SH-SY5Y by chronic hypoxia, J. Neurochem., 83 (2002) 1262-1271] we reported that exposing cells of neuronal origin to a period of chronic hypoxia (CH; 2.5% O(2), 24 h) led to a decrease in processing of the amyloid precursor protein (APP) by the alternative and neuroprotective alpha-secretase pathway. In SH-SY5Y cells, the most likely mechanism was that CH inhibits the protein level of ADAM 10, a disintegrin metalloprotease widely believed to be the alpha-secretase. One effect of CH is to alter the activity of the stress-activated protein kinases (SAPKs) c-Jun amino terminal kinase (JNK) and p38. Thus, the main aims of this study were to investigate the effect of CH on (1) the activity of these SAPKs in SH-SY5Y and (2) whether changes in the activity of these kinases may account for the CH-induced decreases in ADAM 10 expression and sAPPalpha secretion. We demonstrated that the phosphorylation (activity) of JNK was decreased approximately 50% following a period of CH. An inhibitor of JNK did not mimic the effects of CH on either ADAM 10 expression or sAPPalpha secretion under conditions in which the phosphorylation of c-Jun was inhibited by approximately 80%. Thus the loss of JNK activity does not appear to be linked to the decrease in expression of ADAM 10 and secretion of sAPPalpha. In contrast, phosphorylation (activity) of p38 was enhanced approximately 300% following a period of CH. However, inhibitors of p38 were unable to reverse the loss of sAPPalpha in CH cells, indicating that this increase in activity was not linked to the altered processing of APP.

ADAM Proteins↗

PubMed2006

ADAM-10 over-expression increases cortical synaptogenesis.

Cortical cholinergic, glutamatergic and GABAergic terminals become upregulated during early stages of the transgenic amyloid pathology. Abundant evidence suggests that sAPP alpha, the product of the non-amyloidogenic alpha-secretase pathway, is neurotrophic both in vitro and when exogenously applied in vivo. The disintegrin metalloprotease ADAM-10 has been shown to have alpha-secretase activity in vivo. To determine whether sAPP alpha has an endogenous biological influence on cortical presynaptic boutons in vivo, we quantified cortical cholinergic, glutamatergic and GABAergic presynaptic bouton densities in either ADAM-10 moderate expressing (ADAM-10 mo) transgenic mice, which moderately overexpress ADAM-10, or age-matched non-transgenic controls. Both early and late ontogenic time points were investigated. ADAM-10 mo transgenic mice display significantly elevated cortical cholinergic, glutamatergic and GABAergic presynaptic bouton densities at the early time point (8 months). Only the cholinergic presynaptic bouton density remains significantly elevated in late-staged ADAM-10 mo transgenic animals (18 months). To confirm that the observed elevations were due to increased levels of endogenous murine sAPP alpha, exogenous human sAPP alpha was infused into the cortex of non-transgenic control animals for 1 week. Exogenous infusion of sAPP alpha led to significant elevations in the cholinergic, glutamatergic and GABAergic cortical presynaptic bouton populations. These results are the first to demonstrate an in vivo influence of ADAM-10 on neurotransmitter-specific cortical synaptic plasticity and further confirm the neurotrophic influence of sAPP alpha on cortical synaptogenesis.

ADAM Proteins↗

PubMed2002

BACE1 interacts with nicastrin.

Beta-amyloid peptide (Abeta) is generated through the proteolytic cleavage of beta-amyloid precursor protein (APP) by beta- and gamma-secretases. The beta-secretase, BACE1, initiates Abeta formation followed by gamma-cleavage within the APP transmembrane domain. Although BACE1 localizes in the transGolgi network (TGN), its physiological substrates and modulators are not known. In addition, the relationship to other secretase(s) also remains unidentified. Here, we demonstrate that BACE1 binds to nicastrin, a component of gamma-secretase complexes, in vitro, and that nicastrin activates beta-secretase activity in COS-7 cells.

ADAM Proteins↗

PubMed2000

The in vitro activity of ADAM-10 is inhibited by TIMP-1 and TIMP-3.

A recombinant soluble form of the catalytic domain of human ADAM-10 was expressed as an Fc fusion protein from myeloma cells. The ADAM-10 was catalytically active, cleaving myelin basic protein and peptides based on the previously described 'metallosheddase' cleavage sites of tumour necrosis factor alpha, CD40 ligand and amyloid precursor protein. The myelin basic protein degradation assay was used to demonstrate that hydroxamate inhibitors of matrix metalloproteinases (MMPs) were also inhibitors of ADAM-10. The natural MMP inhibitors, TIMP-2 and TIMP-4 were unable to inhibit ADAM-10, but TIMP-1 and TIMP-3 were inhibitory. Using a quenched fluorescent substrate assay and ADAM-10 we obtained approximate apparent inhibition constants of 0.1 nM (TIMP-1) and 0.9 nM (TIMP-3). The TIMP-1 inhibition of ADAM-10 could therefore prove useful in distinguishing its activity from that of TACE, which is only inhibited by TIMP-3, in cell based assays.

ADAM Proteins↗