ADAM family proteins in the immune system

Simultaneous assessment of antigen-stimulated cytokine production and memory subset composition of memory CD8 T cells

The functional identification of antigen-specific CD8 T cell populations is critical to understanding host responses to infection by intracellular pathogens. Furthermore, assessing the properties of protective memory CD8 T cell populations generated by immunization is necessary in the rational design of vaccines. Recently, a classification scheme was proposed in which memory CD8 T cells were divided into one of two distinct subsets, based on CD62L expression, that have different functional properties and protective capacities. Intracellular cytokine staining functionally identifies antigen-specific CD8 T cell populations after short in vitro stimulation with cognate peptide. This short stimulation, however, results in the cleavage of CD62L from the cell surface of antigen-specific CD8 T cells and precludes distinguishing CD62L(hi)- and CD62L(lo)-expressing memory cell subsets within this population. Here, we describe a method of preserving CD62L expression by the antigen-specific CD8 T cell population during coculture with antigen. This methodology allows for the identification and functional assessment of antigen-specific memory CD8 T cell populations, while simultaneously characterizing the memory subset composition of that population. Using this method, we directly identify differences in IL-2 production capacity by CD62L(hi)- and CD62L(lo)-expressing antigen-specific memory CD8 T cell populations.

p44 Mitogen-Activated Protein Kinase (Extracellular Signal-Regulated Kinase 1)–Dependent Signaling Contributes to Epithelial Skin Carcinogenesis

Extracellular signal-regulated kinases (ERK) regulate cellular functions in response to a variety of external signals. However, the specific functions of individual ERK isoforms are largely unknown. Hence, we have investigated the specific function of ERK1 in skin homeostasis and tumorigenesis in ERK1 knockout mice. They spontaneously develop cutaneous lesions and hyperkeratosis with epidermis thickness. Skin hyperproliferation and inflammation induced by application of 12-O-tetradecanoylphorbol-13-acetate (TPA) is strongly reduced in mutant mice. ERK1(-/-) mice are resistant to development of skin papillomas induced by 7,12-dimethylbenz(a)anthracene (DMBA) and promoted by TPA. Tumor appearance was delayed, their formation was less frequent, and their number and size were reduced. Keratinocytes obtained from knockout mice showed reduced growth and resistance to apoptotic signals, accompanied by an impaired expression of genes implicated in growth control and invasiveness. These results highlight the importance of ERK1 in skin homeostasis and in the process of skin tumor development.

ADAM8 as a novel serological and histochemical marker for lung cancer

PURPOSE AND EXPERIMENTAL DESIGN

We have been investigating genes involved in pulmonary carcinogenesis by examining gene expression profiles of non-small-cell lung cancers to identify molecules that might serve as diagnostic markers or targets for development of new molecular therapies. A gene encoding ADAM8, a disintegrin and metalloproteinase domain-8, was selected as a candidate for such molecule. Tumor tissue microarray was applied to examine expression of ADAM8 protein in archival lung cancer samples from 363 patients. Serum ADAM8 levels of 105 lung cancer patients and 72 controls were also measured by ELISA. A role of ADAM8 in cellular motility was examined by Matrigel assays.

RESULTS

ADAM8 was abundantly expressed in the great majority of lung cancers examined. A high level of ADAM8 expression was significantly more common in advanced-stage IIIB/IV adenocarcinomas than in adenocarcinomas at stages I-IIIA. Serum levels of ADAM8 were significantly higher in lung cancer patients than in healthy controls. The proportion of the serum ADAM8-positive cases defined by our criteria was 63% and that for carcinoembryonic antigen was 57%, indicating equivalent diagnostic power of these two markers. A combined assay using both ADAM8 and carcinoembryonic antigen increased sensitivity because 80% of the lung cancer patients were then diagnosed as positive, whereas only 11% of 72 healthy volunteers were falsely diagnosed as positive. In addition, exogenous expression of ADAM8 increased the migratory activity of mammalian cells, an indication that ADAM8 may play a significant role in progression of lung cancer.

CONCLUSIONS

Our data suggest that ADAM8 should be useful as a diagnostic marker and probably as a therapeutic target.

Cell migration: mechanisms of rear detachment and the formation of migration tracks

Cell migration is central to many biological and pathological processes, including embryogenesis, tissue repair and regeneration as well as cancer and the inflammatory response. In general, cell migration can be usefully conceptualized as a cyclic process. The initial response of a cell to a migration-promoting agent is to polarize and extend protrusions in the direction of migration. These protrusions can be large, broad lamellipodia or spike-like filopodia, are usually driven by actin polymerization, and are stabilized by adhering to the extracellular matrix (ECM) via transmembrane receptors of the integrin family linked to the actin cytoskeleton. These adhesions serve as traction sites for migration as the cell moves forward over them, and they must be disassembled at the cell rear, allowing it to detach. The mechanisms of rear detachment and the regulatory processes involved are not well understood. The disassembly of adhesions that is required for detachment depends on a coordinated interaction of actin and actin-binding proteins, signaling molecules and effector enzymes including proteases, kinases and phosphatases. Originally, the biochemically regulated processes leading to rear detachment of migrating cells were thought not to be necessarily accompanied by any loss of cell material. However, it has been shown that during rear detachment long tubular extensions, the retracting fibers, are formed and that "membrane ripping" occurs at the cell rear. By this process, a major fraction of integrin-containing cellular material is left behind forming characteristic migration tracks that exactly mark the way a cell has taken.

Protease domain of human ADAM33 produced by Drosophila S2 cells

Human ADAM33 is a multiple-domain, type-I transmembrane zinc metalloprotease recently implicated in asthma susceptibility [Nature 418 (2002) 426]. To provide an active protease for functional studies, expression of a recombinant ADAM33 zymogen (pro-catalytic domains, pro-CAT) was attempted in several insect cells. The pro-CAT was cloned into baculovirus under the regulation of the polyhedron promoter and using either the honeybee mellitin or ADAM33 signal sequence. Sf9 or Hi5 cells infected with these recombinant viruses expressed the majority of the protein unprocessed and as inclusion bodies ( approximately 10 mg/L). On the other hand, similar constructs could be expressed, processed, and secreted by Drosophila S2 cells using a variety of constitutive (actin, pAc5.1) or inducible (metallothionein, PMT) promoters and leader sequences (e.g., native and BiP). Higher expression level of 10-fold was observed for the inducible system resulting in an average yield of 20 mg/L after purification. The majority of the catalytic domain purified from the Drosophila conditioned media remained associated with the pro-domain after several chromatography steps. An induction cocktail containing cadmium chloride and zinc chloride was subsequently developed for the PMT system as an alternative to using cupric sulfate or cadmium chloride as single inducers. The novel induction cocktail resulted in an increased ratio of secreted catalytic to pro-domain, and yielded milligram amounts of highly purified protease. The availability of this modified expression system facilitated purification of the wild type and several glycosylation mutants, one of which (N231Q) crystallized recently for X-ray structure determination [J. Mol. Biol. 335 (2003) 129].

Expression of splice variants of the human ADAM15 gene and strong interaction between the cytoplasmic domain of one variant and Src family proteins Lck and Hck

OBJECTIVE

The aim of the present study was to show variant species of ADAM15 and unique Src homology 3 (SH3)-binding motifs, which strongly bound Src family proteins compared with ADAM15.

METHODS AND RESULTS

RT-PCR using primers for the cytoplasmic domain revealed the presence of different species, designated ADAM15v1 and ADAM15v2, which had characteristic SH3-binding class I and class II motifs. The mRNA of ADAM15v1 and ADAM15v2 was mainly found in peripheral blood mononuclear cells, T lymphocytes and monocytic cell lines. ADAM15v2 protein interacted more strongly with the Src family proteins Lck and Hck than did ADAM15 protein, as examined by pull-down analysis and immunoprecipitation followed by immunoblot analysis. The binding with Lck and Hck was enhanced by the phosphorylation of ADAM15v2 protein.

CONCLUSIONS

These results suggest that the cytoplasmic domain of ADAM15v2 strongly interacts with Lck and Hck and regulates leukocyte function.

Chronic and recurrent otitis media: a genome scan for susceptibility loci

Otitis media (OM) is the most common childhood disease. Almost all children experience at least one episode, but morbidity is greatest in children who experience chronic/recurrent OM (COME/ROM). There is mounting evidence that COME/ROM clusters in families and exhibits substantial heritability. Subjects who had tympanostomy tube surgery for COME/ROM (probands) and their families were recruited for the present study, and an ear examination was performed, without knowledge of the subject's history, to determine presence of OM sequelae. In addition, tympanometric testing was performed at three frequencies (226, 630 or 710, and 1,400 Hz) to detect abnormal middle-ear mechanics, and hearing was screened at 20 dB for the speech frequencies. Of these families, 121 had at least two individuals who had received the diagnosis of COME/ROM (364 affected and genotyped individuals), of whom 238 affected and informative relative pairs were used for analyses. Single-point nonparametric linkage analysis provided evidence of linkage of COME/ROM to chromosome 10q at marker D10S212 (LOD 3.78; P=3.0 x 10(-5)) and to chromosome 19q at marker D19S254 (LOD 2.61; P=5.3 x 10(-4)). Analyses conditional on support for linkage at chromosomes 10q and 19q resulted in a significant increase in LOD score support on chromosome 3p (between markers D3S4545 and D3S1259). These results suggest that risk of COME/ROM is determined by interactions between genes that reside in several candidate regions of the genome and are probably modulated by other environmental risk factors.

Eosinophils adhere to vascular cell adhesion molecule-1 via podosomes

Vascular cell adhesion molecule (VCAM)-1 supports specific eosinophil adhesion via alpha4beta1 integrin. We tested the hypothesis that adhesive contacts formed by eosinophils on VCAM-1 are different from focal adhesions formed by adherent fibroblasts. Eosinophils adherent on VCAM-1 formed punctate adhesions that fit the criteria for podosomes, highly dynamic structures found in adherent transformed fibroblasts, osteoclasts, and macrophages. The structures contained beta1 integrin subunit, phosphotyrosine-containing proteins, punctate filamentous actin, and gelsolin, a podosome marker. In contrast, nontransformed fibroblasts on VCAM-1 formed peripheral focal adhesions that were positive for alpha4, beta1, phosphotyrosine, vinculin, talin, and paxillin; negative for gelsolin; and associated with microfilaments. Phorbol myristate acetate or tumor necrosis factor-alpha and interleukin-5 stimulated podosome formation in adherent eosinophils. Because podosomes in tumor cells are associated with extracellular matrix degradation, we analyzed the VCAM-1 layer. VCAM-1 was lost under adherent eosinophils but not under adherent fibroblasts. This loss was inhibited by the metalloproteinase inhibitor ortho-phenanthroline and correlated with expression and podosome localization of a membrane-tethered metalloproteinase, a disintegrin and metalloproteinase domain 8. Podosome-mediated VCAM-1 clearance may be a mechanism to regulate eosinophil arrest and extravasation in allergic conditions such as asthma.

Interaction of human immunoglobulin G with CD16 on natural killer cells: ligand clearance, FcgammaRIIIA turnover and effects of metalloproteinases on FcgammaRIIIA-mediated binding, signal transduction and killing

Human natural killer (NK) cells express low-affinity Fc immunoglobulin G (IgG) receptor (FcgammaRIIIA/CD16). The binding of monomeric IgG (mIgG) and F(ab')(2) fragments of 3G8 anti-CD16 monoclonal antibody (mAb) to FcgammaRIIIA was investigated by flow cytometry. Over 90% of NK cells bound endogenous IgG, and during incubation at 37 degrees C, the FcgammaRIIIA occupancy decreased slowly. Approximately 90% of NK cells bind mIgG or F(ab')(2) fragments of 3G8 anti-CD16 mAb. The calculated half-time (T(1/2)) of in vitro mIgG dissociation from FcgammaRIIIA was 130 min. By cross-linking the mIgG ligand with F(ab')(2) fragments of anti-human IgG antibody, the T(1/2) decreases to 85 min. In kinetics study, it has been shown that (125)I-mIgG bound to FcgammaRIIIA is slowly released in the culture supernatant, maybe eluted at acid pH, or partially internalized and degraded. The binding of IgG to FcgammaRIIIA was increased by 53.8% on cells cultured in the presence of RU36156, a matrix metalloproteinase (MMP) inhibitor. Furthermore, an increase in phosphorylation of Lyn tyrosine kinase, after cross-linking of mIgG-FcgammaRIIIA complex, was observed on NK cells treated with RU36156. When the FcgammaRIIIA was occupied by mIgG, the capacity of NK cells to kill K562 target cells was decreased by RU36156, because the MMP inhibitor protects CD16 from proteolysis. Our data demonstrate that binding of mIgG to human NK cells is followed by ligand dissociation and/or internalization, enzymatic degradation and exocytosis. The RU36156 MMP inhibitor protects FcgammaRIIIA from cleavage, augments NK-cell activation and may interfere in their killing capacity.

Expression and regulation of a disintegrin and metalloproteinase (ADAM) 8 in experimental asthma

Asthma, a complex chronic inflammatory pulmonary disorder, is on the rise despite intense ongoing research. To elucidate novel pathways involved in asthma pathogenesis, we used transcript expression profiling in a murine model of asthma. Employing asthma models induced by different allergens (ovalbumin and Aspergillus fumigatus) we uncovered the involvement of ADAM8, a member of a disintegrin and metalloproteinase (ADAM) family. In situ hybridization of mouse lungs revealed strong ADAM8 induction in peribronchial and perivascular inflammatory cells as well as in bronchiolar epithelial cells following allergen challenge. Sequence analysis of lung ADAM8 cDNA identified a novel splice variant of ADAM8 that contained an additional exon in juxtaposition to the transmembrane domain. Allergen-induced ADAM8 mRNA accumulation in the lung was dose- and time-dependent. Transgenic or pharmacologic delivery of interleukin (IL)-4 or IL-13 to the lungs resulted in a marked increase of ADAM8 expression. Gene-targeted mice studies revealed that ovalbumin-induced ADAM8 was largely dependent upon signal transducer and activator of transcription (STAT) 6 and the IL-4 receptor alpha-chain. Thus, ADAM8 is an allergen-, IL-4-, and IL-13-induced gene in the experimental asthmatic lung. Taken together with the role of ADAM33 in asthma, these results suggest that allergic lung responses involve the interplay of diverse members of the ADAM family.

Nonchannel drug targets in atrial fibrillation

Atrial fibrillation (AF) is the most common clinical arrhythmia and one of the most important factors for ischemic stroke. In general, AF is treated with "channel-blocking drugs" to restore sinus rhythm and warfarin is recommended in the majority of patients to prevent atrial thrombus formation and thromboembolic events. In the recent years, a tremendous amount has been learned about the pathophysiology and molecular biology of AF. Thus, pharmacologic interference with specific signal transduction pathways with "non-channel-blocking drugs" appears promising as a novel antiarrhythmic approach to maintain sinus rhythm and to prevent atrial clot formation. Therefore, this review will highlight some novel "nonchannel drug targets" for AF therapy.

Tumour necrosis factor-alpha converting enzyme (TACE) activity in human colonic epithelial cells

Tumour necrosis factor (TNF)-alpha converting enzyme (TACE) releases biologically active, soluble TNF-alpha from transmembrane pro-TNF-alpha and has attracted interest as a specific therapeutic target in inflammatory bowel disease (IBD). Strong immunoreactivity for TACE protein was demonstrated recently in human colonic epithelium, but the function is unknown. We investigated if human colonic epithelial cells express functional TACE activity and how TACE expression is regulated in response to cytokine stimulation. TACE and TNF-alpha mRNA and protein expression were measured in HT-29 and DLD-1 colonic epithelial cells by reverse-transcription polymerase chain reaction, western blotting or enzyme-linked immunosorbent assay. Monocytic THP-1 cells served as positive control. Functional TACE activity was identified and quantified in detergent extracts of cell lines and freshly isolated colonocytes from 14 IBD patients and five controls by a hydrolysis assay using an oligopeptide spanning the cleavage site in pro-TNF-alpha. HT-29 and DLD-1 cells spontaneously expressed TACE mRNA and the active form of TACE protein at levels similar to those of monocytic cells. Functional TACE activity was demonstrated in all cell lines and in cells of controls or IBD patients irrespective of disease activity. TACE mRNA expression and functional activity remained unchanged in cell lines after stimulation with TNF-alpha despite clear induction of TNF-alpha mRNA expression and release of soluble TNF-alpha protein. The release of soluble TNF-alpha protein was almost completely abolished by CH4474, a synthetic TACE inhibitor. We conclude that functional TACE activity is constitutively expressed in human colonic epithelial cells and responsible for processing of the mature, soluble form of TNF-alpha in response to cytokine stimulation.

Transmembrane proteases in cell growth and invasion: new contributors to angiogenesis?

Transmembrane proteases (TPs) are proteins anchored in the plasma membrane with their catalytic site exposed to the external surface of the membrane. TPs are widely expressed, and their dysregulated expression is associated with cancer, infection, inflammation, autoimmune and cardiovascular diseases, all diseases where angiogenesis is part of the pathology. TPs participate in extracellular proteolysis (degradation of extracellular matrix components, regulation of chemokine activity, release of membrane-anchored cytokines, cytokine receptors and adhesion molecules) and influence cell functions (growth, secretion of angiogenic molecules, motility). Recent attention has been focused on the ADAM-17 (a disintegrin and metalloprotease)/TACE/CD156q, the MT1-MMP (membrane-type-1 matrix metallo proteinase)/MMP-14, and the ectopeptidases aminopeptidase N (APN/CD13), dipeptidyl peptidase IV (DPPIV/CD26) and angiotensin-converting enzyme (ACE/CD143), that appear to have a critical role in angiogenesis. This article summarizes current knowledge on these TPs, and reviews recent investigations that document their participation during angiogenic-related events. Through their multiple roles, TPs may thereby provide critical links in angiogenesis.

Inverse regulation of the ADAM-family members, decysin and MADDAM/ADAM19 during monocyte differentiation

Two members of the ADAM (a disintegrin and metalloprotease)-family, MADDAM and decysin, were described as dendritic cell (DC) maturation markers. We are interested in monocyte differentiation and investigated in particular the expression pattern of both genes during the differentiation of human monocytes into DC and macrophages (MAC). Both genes are weakly expressed in freshly isolated monocytes. In immature DC decysin mRNA was absent, even after induction of the terminal differentiation of DC by CD40L or tumour necrosis factor-alpha (TNF-alpha). Only in DC maturated by lipopolysaccharide (LPS) strong signals of decysin mRNA were detected. However, MADDAM mRNA was expressed in immature DC and the expression was markedly increased after induction of the terminal DC differentiation by various stimuli. In contrast, MAC showed a high constitutive decysin mRNA expression, but expressed no MADDAM mRNA. On protein level similar results of MADDAM expression were obtained. Stimulation of MAC by LPS did not induce MADDAM mRNA expression, while decysin mRNA expression was strongly increased. Further investigations revealed that the well-known inducer of MAC differentiation, 1alpha,25-dihydroxyvitamin D3 up-regulated decysin mRNA expression during the differentiation of primary monocytes and myelomonocytic THP-1 cells into MAC. In vivo decysin mRNA expression was only detected in human colon, but not in other tissues we examined. Accordingly, isolated intestinal MAC expressed decysin mRNA. In conclusion, decysin and MADDAM mRNA expression were regulated in an opposite way during monocyte differentiation: MADDAM mRNA and protein was mainly detected in DC, whereas decysin mRNA expression was mainly found in MAC. Therefore only MADDAM, but not decysin is a suitable marker for human monocyte-derived DC.

Inverse regulation of the ADAM-family members, decysin and MADDAM/ADAM19 during monocyte differentiation

Two members of the ADAM (a disintegrin and metalloprotease)-family, MADDAM and decysin, were described as dendritic cell (DC) maturation markers. We are interested in monocyte differentiation and investigated in particular the expression pattern of both genes during the differentiation of human monocytes into DC and macrophages (MAC). Both genes are weakly expressed in freshly isolated monocytes. In immature DC decysin mRNA was absent, even after induction of the terminal differentiation of DC by CD40L or tumour necrosis factor-alpha (TNF-alpha). Only in DC maturated by lipopolysaccharide (LPS) strong signals of decysin mRNA were detected. However, MADDAM mRNA was expressed in immature DC and the expression was markedly increased after induction of the terminal DC differentiation by various stimuli. In contrast, MAC showed a high constitutive decysin mRNA expression, but expressed no MADDAM mRNA. On protein level similar results of MADDAM expression were obtained. Stimulation of MAC by LPS did not induce MADDAM mRNA expression, while decysin mRNA expression was strongly increased. Further investigations revealed that the well-known inducer of MAC differentiation, 1alpha,25-dihydroxyvitamin D3 up-regulated decysin mRNA expression during the differentiation of primary monocytes and myelomonocytic THP-1 cells into MAC. In vivo decysin mRNA expression was only detected in human colon, but not in other tissues we examined. Accordingly, isolated intestinal MAC expressed decysin mRNA. In conclusion, decysin and MADDAM mRNA expression were regulated in an opposite way during monocyte differentiation: MADDAM mRNA and protein was mainly detected in DC, whereas decysin mRNA expression was mainly found in MAC. Therefore only MADDAM, but not decysin is a suitable marker for human monocyte-derived DC.

NK cells and the tumour microenvironment: implications for NK-cell function and anti-tumour activity

Although it is clear that natural killer (NK) cells have the ability to recognize and kill tumour cells in vitro, their potential as a highly effective treatment for tumours has not yet been realized in the clinical setting. Following activation, endogenous and adoptively transferred NK cells can be found in tumours. However, not all tumours are equally well-infiltrated, and many of the infiltrating cells do not make target-cell contact but rather reside in the tumour stroma. New insights into the migration of NK cells, their activation status and production of matrix-degrading proteases might help to overcome this localization defect, with implications for the treatment of human cancer.

Structure and expression of the murine ADAM 15 gene and its splice variants, and difference of interaction between their cytoplasmic domains and Src family proteins

The murine cell surface antigen ADAM 15 is a transmembrane glycoprotein that is expressed in a variety of cells including monocytic and T cell lines and consists of a metalloprotease domain, a disintegrin domain, a cysteine-rich domain, and an epidermal growth factor (EGF)-like domain in the extracellular region. The cytoplasmic domain comprises 103 amino acids containing proline-rich endophilin I, Src homology 3 (SH3), and phox homology domain-containing protein (SH3PX1) binding motifs. The ADAM15 gene is composed of 21 exons and 20 introns and spans approximately 10 kb. The transcription initiation site of the ADAM15 gene was defined by an oligonucleotide-capping method. Reverse transcription (RT)-PCR using primers of the cytoplasmic domain of ADAM15 revealed the presence of different ADAM15 species designated ADAM15v1 and ADAM15v2, respectively, that had characteristic SH3-binding class I and/or class II motifs. The ADAM15v1 and ADAM15v2 genes consist of an extra one exon and two exons, respectively, which exist in intron 19 of the ADAM15 gene. The expression of ADAM15v1 and ADAM15v2 mRNA was found in T lymphocyte and monocyte lines. ADAM15v2 protein interacted more strongly with the Src family proteins Lck and Src than ADAM15 protein, when examined by pull-down and immunoprecipitation followed by immunoblot analysis using a T lymphocyte line. Phosphorylation of ADAM15v2 protein markedly enhanced the binding with Lck. These results suggest that the cytoplasmic domain of ADAM15v2 strongly interacts with Lck and plays an important role in T lymphocytes.

The secreted protein discovery initiative (SPDI), a large-scale effort to identify novel human secreted and transmembrane proteins: a bioinformatics assessment

A large-scale effort, termed the Secreted Protein Discovery Initiative (SPDI), was undertaken to identify novel secreted and transmembrane proteins. In the first of several approaches, a biological signal sequence trap in yeast cells was utilized to identify cDNA clones encoding putative secreted proteins. A second strategy utilized various algorithms that recognize features such as the hydrophobic properties of signal sequences to identify putative proteins encoded by expressed sequence tags (ESTs) from human cDNA libraries. A third approach surveyed ESTs for protein sequence similarity to a set of known receptors and their ligands with the BLAST algorithm. Finally, both signal-sequence prediction algorithms and BLAST were used to identify single exons of potential genes from within human genomic sequence. The isolation of full-length cDNA clones for each of these candidate genes resulted in the identification of >1000 novel proteins. A total of 256 of these cDNAs are still novel, including variants and novel genes, per the most recent GenBank release version. The success of this large-scale effort was assessed by a bioinformatics analysis of the proteins through predictions of protein domains, subcellular localizations, and possible functional roles. The SPDI collection should facilitate efforts to better understand intercellular communication, may lead to new understandings of human diseases, and provides potential opportunities for the development of therapeutics.

Membrane-anchored CD40 is processed by the tumor necrosis factor-alpha-converting enzyme. Implications for CD40 signaling

The soluble form of CD40 (sCD40), which co-exists with the membrane-anchored form (mCD40), is a natural antagonist of mCD40/CD154 interaction. However, the mechanism leading to the production of sCD40 has never been investigated. Here, we show that the engagement of mCD40 on the surface of B lymphocytes by anti-CD40 antibody led to enhanced sCD40 release associated with decreased amounts of mCD40. This sCD40 production was not affected by vesicular traffic inhibitors but was completely blocked by a broad-spectrum synthetic metalloproteinase (MP) inhibitor (GM6001) or a membrane-anchored MP-specific inhibitor (dec-RVKR-cmk). Recombinant MP disintegrin tumor necrosis factor-alpha converting enzyme (TACE) cleaved the purified CD40 ectodomain/Fc chimeric protein in vitro, giving rise to an sCD40 form similar to that shed from B cell cultures. Moreover, spontaneous production of sCD40 by mCD40-transfected human embryonic kidney cells (constitutively expressing TACE) was enhanced by the overexpression of TACE and abrogated by co-transfection with a dominant-negative TACE mutant. These results provide strong evidence that sCD40 production is an active process regulated by the engagement of mCD40 and its proteolytic cleavage by TACE or a related MP disintegrin. Given the antagonistic activity of sCD40 on the CD40/CD154 interaction, this shedding mechanism might represent an important negative feedback control of CD40 functions.

Identification of novel polymorphisms in the Adam33 gene

Adam33 is a member of a family of genes that encode membrane-anchored proteins with a disintegrin and a metalloprotease domain and that are primarily expressed in lung fibroblasts and bronchial smooth muscle. The human Adam33 gene is located on chromosome 20p13, a region that has been linked to asthma and bronchial hyperresponsiveness. Recently, the polymorphisms in Adam33 have been found to be associated with asthma. In this study, we performed polymorphism scanning of the entire genomic region, including the promoter region of Adam33, by direct sequencing. We identified 16 novel polymorphisms in the Adam33 gene. Among these novel polymorphisms, three polymorphisms (-2154G-->A, -753T-->A, and -330C-->T) were found to be in the promoter region and one polymorphism (13491 G-->A) was located in 3' untranslated region of the Adam33 gene.

Categorically distinct acute stressors elicit dissimilar transcriptional profiles in the paraventricular nucleus of the hypothalamus

The paraventricular hypothalamic nucleus (PVH) is a key site for integrating neuroendocrine, autonomic, and behavioral adjustments to diverse homeostatic challenges, including "physiological" (e.g., infection or hemorrhage) and "emotional" [e.g., restraint (RST) or footshock] stresses. Both types of challenges ultimately converge to activate common response systems represented in PVH, including the hypothalamo-pituitary-adrenal axis and the sympathoadrenal system. Oligonucleotide microarrays (U74A; Affymetrix, Santa Clara, CA) were used to compare and contrast gene expression profiles in the PVH elicited at 1 and 3 hr after acute exposure to representative physiological [intraperitoneal injection of 10 microg lipopolysaccharide (LPS)] and emotional (30 min RST) stressors. In general, the two challenges recruited relatively few genes in common, with the degree of overlap varying across functional classes of genes. The greatest degree of commonality was seen among signaling molecules and neuropeptides, whereas transcription factors upregulated by RST and LPS were largely distinct. Unexpectedly, RST induced a number of immune-related molecules, which were not regulated by LPS. Hybridization histochemical analyses localized a subset of responsive transcripts to the PVH and/or immediately adjoining regions. Immunerelated molecules in particular distributed broadly to vascular and other barrier-associated cell types. These global transcriptional profiles inform the search for early (transcription factors) and late (target genes) mechanisms in the modulation of PVH, and generalized CNS, responses to categorically distinct stressors.

Identification of genes promoting angiogenesis in mouse lung by transcriptional profiling

A better understanding of the regulation of factors that promote angiogenesis may ultimately enable improved therapeutic control of this important process. In our previous studies, obstruction of the left pulmonary artery in the mouse consistently induced the formation of a new vasculature, which developed from the visceral pleura and entered the upper left lung directly within 5-6 days after ligation. No new vessels developed to the lower left lung, despite the initial ischemic stimulus being identical to that in the upper lung. Using this unique model of angiogenesis, we have determined the temporal pattern of differential gene expression from two independent regions of the same lung: one where angiogenesis is induced, and the other where angiogenesis does not occur. Microarray analysis and quantitative real-time RT-PCR were used to compare the signals from these two lung regions in the first 3 d following ischemia. The findings reveal the important roles of ELR+ CXC chemokines as proangiogenic signals. Genes involved in tissue remodeling, inflammation, and injury were also upregulated in the proangiogenic upper lung. Results also confirm that lung ischemia, rather than hypoxia, is the essential trigger for angiogenesis. These altered profiles of expression in the early stage of lung ischemia show potential roles and interactions of the most important genes involved in promoting new blood vessel formation.

Identification of SAP97 as an intracellular binding partner of TACE

Tumor necrosis factor alpha converting enzyme (TACE) is the metalloprotease-disintegrin responsible for the ectodomain shedding of several proteins, including tumor necrosis factor alpha. Using the yeast two-hybrid system, we identified the scaffolding protein synapse associated protein 97 (SAP97) as a binding partner of the cytoplasmic domain of TACE. By deletions and site-directed mutagenesis, we demonstrated that this interaction involved the PDZ3 domain of SAP97 and the extreme C-terminal amino-acid sequence of TACE. This interaction as well as the identification of the specific domains involved was confirmed in vitro by affinity purification and in mammalian cells by co-immunoprecipitation and alteration of localization analyzed by immunofluorescence microscopy. In addition, confocal microscopy showed that endogenous TACE and SAP97 colocalized in some intracellular areas of COS-7 cells and CACO-2 cells. Furthermore, overexpression of SAP97, unlike that of a mutant form of SAP97 deleted for its PDZ3 domain, altered the ability of TACE to release its substrates. Altogether, these results demonstrate an interaction between TACE and SAP97, which may have a functional implication for the regulation of TACE shedding activity.

Intracellular maturation and transport of tumor necrosis factor alpha converting enzyme

The tumor necrosis factor alpha converting enzyme (TACE) activity is required for the shedding of a variety of biologically active membrane bound precursors. The activation of TACE necessitates the proteolytic cleavage of its prodomain, a process that was suggested to be catalyzed by the proprotein convertase furin. However, the involvement of furin in this activation process has never been experimentally demonstrated. We have shown that the furinlike cleavage site (R-V-K-R(214)) localized between the prodomain and the metalloprotease domain of TACE is the sole site that can be in vitro cleaved by furin. In Cos7 cells, the release of TACE-processed substrates was reduced by the overexpression of the furin-specific proprotein convertase inhibitor Portland alpha1-antitrypsin inhibitor, but the release of TACE-processed substrates was increased by overexpression of furin in LoVo cells (deficient in furin activity) in which a mature form of TACE was identified. The immature form of TACE was detected at the surface of LoVo cells and at the surface of Cos7 and HT29 cells upon proprotein convertase inhibition. These results suggest that furin is the major proprotein convertase involved in the maturation/activation of TACE which is not a prerequisite for its cell-surface expression.

CD156 transgenic mice. Different responses between inflammatory types

CD156 (ADAM8) is part of the ADAM family of proteins with the catalytic site consensus sequence of metalloprotease and disintegrins. To examine the role of CD156 in vivo, we generated mutant CD156 (eCD156) transgenic mice expressing the ectodomain of CD156 under the control of the alpha1-antitrypsin (AT) promoter. One of the transgenic mice designated ATMS2-TG18 expressed a 1.84 kb mRNA which was predicted to be a truncated CD156. The expression of the transgenic CD156 mRNA in ATMS2-TG18 mice was abundant in the liver and slight in kidney. Turpentine oil (TO) and lipopolysaccharide (LPS) markedly upregulated the expression. Soluble CD156 (sCD156) was produced constitutively, and increased after the treatment with TO. Casein-induced peritoneal leukocyte infiltration was significantly less extensive in ATMS2-TG18 than non-transgenic mice. The expression of L-selectin in neutrophils (PMN) from peripheral blood leukocytes (PBL) was more strongly downregulated in ATMS2-TG18 than non-transgenic mice, suggesting that L-selectin in PMN from ATMS2-TG18 mice was shed by sCD156. In contrast, oxazolone (Ox)-induced contact hypersensitivity reactions (CHR) were more marked in ATMS2-TG18 than non-transgenic mice. The expression of E-selectin mRNA was detected in inflammatory skin sites from ATMS2-TG18, but not non-transgenic mice, suggesting that sCD156 may activate the endothelial cells and lead to the upregulation of E-selectin. These results suggest that CD156 regulates leukocyte infiltration directly or indirectly.

Towards determining the differentiation program of antigen-presenting dendritic cells by transcriptional profiling

Dendritic cells (DC) represent professional antigen-presenting cells that develop from hematopoietic progenitors through successive steps of differentiation. Employing DNA microarray technology, we analysed the specific changes in gene expression that occur when human progenitor cells differentiate into DC. CD34 progenitor cells were first amplified in vitro with stem cell factor (SCF), Flt3 ligand (FL), thrombopoietin and IL-6/soluble IL-6 receptor fusion protein, and cells were then induced to differentiate into DC with IL-4 and GM-CSF. DC maturation was induced by TNFalpha. Progenitor cells and DC were subjected to transcriptional profiling by DNA microarrays that represent 13000 human genes. Our analysis revealed specific changes in the expression of a large number of cell surface antigens including molecules involved in antigen uptake and processing, cell migration and antigen presentation. Genes encoding such molecules were upregulated during DC differentiation as were genes encoding cytokines, cytokine receptors, chemokines and chemokine receptors. Stem cell genes and genes related to the multilineage differentiation potential and proliferative state of progenitor cells were downregulated. Our analysis also provides information on the expression profiles of transcriptional regulators such as the NF-kappaB/rel and STAT transcription factors. Interestingly, NF-kappaB/rel factors were found to be expressed in both progenitor cells and DC at similar levels and were induced by TNFalpha. In contrast, expression of STAT factors increased during DC differentiation and their expression was virtually unaffected by TNFalpha.

Decreased expression of membrane IL-5 receptor alpha on human eosinophils: II. IL-5 down-modulates its receptor via a proteinase-mediated process

In the accompanying study, we demonstrated that following Ag challenge, membrane (m)IL-5Ralpha expression is attenuated on bronchoalveolar lavage eosinophils, soluble (s)IL-5Ralpha is detectable in BAL fluid in the absence of increased steady state levels of sIL-5Ralpha mRNA, and BAL eosinophils become refractory to IL-5 for ex vivo degranulation. We hypothesized that IL-5 regulates its receptor through proteolytic release of mIL-5Ralpha, which in turn contributes to the presence of sIL-5Ralpha. Purified human peripheral blood eosinophils were incubated with IL-5 under various conditions and in the presence of different pharmacological agents. A dose-dependent decrease in mIL-5Ralpha was accompanied by an increase in sIL-5Ralpha in the supernatant. IL-5 had no ligand-specific effect on mIL-5Ralpha or sIL-5Ralpha mRNA levels. The matrix metalloproteinase-specific inhibitors BB-94 and GM6001 and tissue inhibitor of metalloproteinase-3 partially inhibited IL-5-mediated loss of mIL-5Ralpha, suggesting that sIL-5Ralpha may be produced by proteolytic cleavage of mIL-5Ralpha. IL-5 transiently reduced surface expression of beta-chain, but had no effect on the expression of GM-CSFRalpha. Pretreatment of eosinophils with a dose of IL-5 that down-modulated mIL-5Ralpha rendered these cells unable to degranulate in response to further IL-5 stimulation, but they were fully responsive to GM-CSF. These findings suggest that IL-5-activated eosinophils may lose mIL-5Ralpha and release sIL-5Ralpha in vivo, which may limit IL-5-dependent inflammatory events in diseases such as asthma.

Loxosceles spider venom induces metalloproteinase mediated cleavage of MCP/CD46 and MHCI and induces protection against C-mediated lysis

We have recently shown that sphingomyelinase D toxins from the spider Loxosceles intermedia induce Complement (C) -dependent haemolysis of autologous erythrocytes by the induction of cleavage of cell-surface glycophorins through activation of a membrane-bound metalloproteinase. The aim of this study was to investigate the effects of these toxins on C-regulator expression and the C-resistance of nucleated cells. Cells were incubated with Loxosceles venom/toxins and the expression of C-regulators was assessed by flow cytometry. A reduced expression of membrane co-factor protein (MCP) was observed, while expression of decay-accelerating factor (DAF) and CD59 was not affected. Analysis of other cell-surface molecules showed a reduced expression of major histocompatibility complex I (MHCI). Western blotting showed that a truncated form of MCP was released into the supernatant. Release could be prevented by inhibitors of metalloproteinases of the adamalysin family but not by inhibitors specific for matrix metalloproteinases. Cleavage of MCP was induced close to or within the membrane as demonstrated by the cleavage of transmembrane chimeras of CD59 and MCP. Although the venom/toxins induced a release of MCP, the C-susceptibility was decreased. The mechanism of this induction of resistance may involve a change in membrane fluidity induced by the sphingomyelinase activity of the toxin/venom and/or involvement of membrane-bound proteases. The soluble forms of MCP found in tissues and body under pathological conditions like cancer and autoimmune diseases may be released by a similar mechanism. The identity of the metalloproteinase(s) activated by the spider venom and the role in pathology of Loxoscelism remains to be established.

A new method for detecting TNF-alpha-secreting cells using direct-immunofluorescence surface membrane stainings

In the present study, a new flow cytometric method for the identification of TNF-alpha-secreting cells based on the use of a TNF-alpha converting enzyme (TACE) inhibitor compound (BB3103) is described. TNF-alpha secreting cells were measured in parallel in stimulated peripheral blood samples (n=4), using the BB3103 TACE inhibitor or brefeldin A as secretion blocking agents. To induce TNF-alpha production by PB T-cells and monocytes, whole blood samples were stimulated either for 4 h with PMA plus ionomycin or for 6 h with LPS plus IFNgamma, respectively. Interestingly, slightly higher percentages of TNF-alpha(+) CD4(+) (65+/-11% versus 49+/-11.4%, p=0.06) and TNF-alpha(+) CD8(+) (60+/-9.9% versus 47+/-27.7% p=0.46) T-cells together with a greater amounts of TNF-alpha/cell-mean fluorescence intensity (MFI) of 1050+/-230 versus 258+/-112 for CD4(+), p=0.06 and 424+/-169 versus 266+/-201 for CD8(+), p=0.27-were found for activated T-lymphocytes cultured with BB3103 as compared to those treated with brefeldin A. Kinetic analysis of surface TNF-alpha expression under these stimulatory conditions showed detectable surface TNF-alpha levels on both T-cells and monocytes after 30 min. Thereafter, surface TNF-alpha expression on both T-cells and monocytes progressively increased for up to 3 and 4 h, respectively. From this time on, a decrease in the membrane levels of TNF-alpha was observed in the monocytes, presumably due to the occurrence of cell death. In order to show that the BB3103 inhibitor was also active on other TACE-associated molecules, CD62L expression on PMA-stimulated PB lymphocytes, monocytes and neutrophils was analyzed by flow cytometry in the presence and absence of BB3103. The TACE inhibitor proved to be active in stabilizing CD62L expression on PMA-stimulated PB leukocytes. In summary, our results show that stimulation of PB T-cells and monocytes in the presence of the TACE inhibitor BB3103 followed by surface staining for TNF-alpha provides a new, simple and rapid method for the identification of intact TNF-alpha producting cells present in a sample without the need for prior cell fixation and permeabilization. In addition, this approach could also be applied in order to stabilize the expression of other metalloprotease-sensitive molecules such as CD62L on the surface of PB leukocytes.

The Caenorhabditis elegans ADAMTS family gene adt-1 is necessary for morphogenesis of the male copulatory organs

Remodeling of the extracellular matrix (ECM) is pivotal for various biological processes, including organ morphology and development. The Caenorhabditis elegans male tail has male-specific copulatory organs, the rays and the fan. Ray morphogenesis, which involves a rapid remodeling of the ECM, is an important model of morphogenesis, although its mechanism is poorly understood. ADAMTS (a disintegrin-like and metalloproteinase with thrombospondin type I motifs) is a novel metalloproteinase family that is thought to be an important regulator for ECM remodeling during development and pathological states. We report here that a new C. elegans ADAMTS family gene, adt-1, plays an important regulatory role in ray morphogenesis. Inactivation of the adt-1 gene resulted in morphological changes in the rays as well as the appearance of abnormal protuberances around the rays. In addition, mating ability was remarkably impaired in adt-1 deletion mutant males. Furthermore, we found that the green fluorescent protein reporter driven by the adt-1 promoter was specifically expressed throughout the rays in the male tail. We hypothesize that ADT-1 controls the ray extension process via remodeling of the ECM in the cuticle.

Identification and preliminary characterization of mouse Adam33

BACKGROUND

The metalloprotease-disintegrin family, or ADAM, proteins, are implicated in cell-cell interactions, cell fusion, and cell signaling, and are widely distributed among metazoan phyla. Orthologous relationships have been defined for a few ADAM proteins including ADAM10 (Kuzbanian), and ADAM17 (TACE), but evolutionary relationships are not clear for the majority of family members. Human ADAM33 refers to a testis cDNA clone that does not contain a complete open reading frame, but portions of the predicted protein are similar to Xenopus laevis ADAM13.

RESULTS

In a 48 kb region of mouse DNA adjacent to the Attractin gene on mouse chromosome 2, we identified sequences very similar to human ADAM33. A full-length mouse cDNA was identified by a combination of gene prediction programs and RT-PCR, and the probable full-length human cDNA was identified by comparison to human genomic sequence in the homologous region on chromosome 20p13. Mouse ADAM33 is 44% identical to Xenopus laevis ADAM13, however a phylogenetic alignment and consideration of functional domains suggests that the two genes are not orthologous. Mouse Adam33 is widely expressed, most highly in the adult brain, heart, kidney, lung and testis.

CONCLUSIONS

While mouse ADAM33 is similar to Xenopus ADAM13 in sequence, further examination of its embryonic expression pattern, catalytic activity and protein interactions will be required to assess the functional relationship between these two proteins. Adam33 is expressed in the mouse adult brain and could play a role in complex processes that require cell-cell communication.

The lymphocyte metalloprotease MDC-L (ADAM 28) is a ligand for the integrin alpha4beta1

The interaction of lymphocytes with other cells is critical for normal immune surveillance and response. MDC-L (ADAM 28), a member of the ADAM (a disintegrin and metalloprotease) protein family, is expressed on the surface of human lymphocytes. ADAMs possess a disintegrin-like domain similar in sequence to small non-enzymatic snake venom peptides that act as integrin antagonists. We report here that the disintegrin domain of MDC-L is recognized by the leukocyte integrin alpha(4)beta(1). Recombinant Fc fusion proteins possessing the disintegrin domain of MDC-L supported adhesion of the T-lymphoma cell line, Jurkat, in a concentration- and divalent cation-dependent manner. Adhesion of Jurkat cells to the disintegrin domain of MDC-L was inhibited by an anti-MDC-L monoclonal antibody (mAb), Dis1-1. The epitope for mAb Dis1-1 was localized within 59 residues of the disintegrin domain. Recombinant expression of this 59-residue fragment of the disintegrin domain also supported cell adhesion. Adhesion of Jurkat cells to the MDC-L disintegrin domain was specifically inhibited by anti-alpha(4) and anti-beta(1) function-blocking mAbs. Furthermore, adhesion of various cell lines to MDC-L correlated with expression of the integrin alpha(4)-subunit. Transfected K562 cells expressing alpha(4)beta(1) adhered to the disintegrin domain in contrast to non-transfected K562 cells. We further investigated the binding of recombinant MDC-L disintegrin domain (rDis-Fc) in solution. The rDis-Fc was found to bind to Jurkat cells in solution in a concentration-dependent and saturable manner. Both adhesion and solution binding of rDis-Fc was inhibited by the alpha(4)beta(1) ligand mimetic CS-1 peptide. Additionally, recognition of the MDC-L disintegrin domain required "activation" of lymphocyte beta(1) integrins. The interaction of MDC-L with alpha(4)beta(1) may potentially regulate metalloprotease function by targeting or sequestering the active protease on the cell surface. These results suggest a potential role for the lymphocyte ADAM, MDC-L, in the interaction of lymphocytes with alpha(4)beta(1)-expressing leukocytes.

Expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases define the migratory characteristics of human monocyte-derived dendritic cells

Dendritic cells (DCs) have an essential role in the initiation of immune responses as they deliver antigen/epitope and the appropriate signals to activate naïve T cells and thus start an immune response. In order to fulfil their function, DCs have to patrol different part of the body, thus migrating through the extracellular matrix to sample the local 'antigenic' environment. In the present study, we have investigated which enzymes might be involved in this process using the Matrigel trans-well migration assay, an in vitro model of extracellular matrix migration. In this assay we analysed the migratory ability of interleukin-4 (IL-4)/granulocyte macrophage-colony-stimulating factor (GM-CSF)-derived immature DCs as well as mature DCs, induced by tumour necrosis factor-alpha (TNF-alpha) and modified vaccinia virus Ankara (MVA). The 'mature' DCs showed an increased migration through Matrigel, which was significantly inhibited by inhibitors of matrix metalloproteinases (MMP). We also observed that the dominant MMP involved in this process was MMP-9, and a concomitant decrease of the endogenous tissue inhibitors of metalloproteinases (TIMP)-1 and TIMP-2 was also observed. Collectively these data suggest that the balance between MMP/TIMP determines the net migratory capacity of human DCs. Surprisingly, TIMP-3 was significantly increased in mature DC. Our data thus indicate that MMP and TIMP play a role in the migratory ability of human DCs. Our results also suggest that TIMP-3 expression might represent a new marker of maturation of human DCs.

cDNA array analysis of cag pathogenicity island-associated Helicobacter pylori epithelial cell response genes

Helicobacter pylori strains containing the cag pathogenicity island (PAI) induce NF-kappaB activation and interleukin-8 secretion in gastric epithelial cells. The aim of this study was to investigate changes in epithelial gene expression induced by cag PAI-positive and -negative strains of H. pylori using high-density cDNA array hybridization technology. Radio-labeled cDNA prepared from H. pylori-infected Kato 3 gastric epithelial cells was hybridized to high-density cDNA arrays to identify changes in epithelial gene expression compared to noninfected controls. In vivo expression of selected, differentially expressed genes was examined by reverse transcription-PCR analysis of H. pylori-positive and -negative gastric mucosa. Screening of ca. 57,800 cDNAs identified 208 known genes and 48 novel genes and/or expressed sequence tags of unknown function to be differentially expressed in Kato 3 cells following H. pylori infection. Marked differences in gene expression profiles were observed following cag PAI-positive and cag PAI-negative infection with 15 novel cDNAs and 92 known genes being differentially expressed. H. pylori was found to change the expression of genes encoding growth factors and cytokine/chemokines and their receptors, apoptosis proteins, transcription factors and metalloprotease-disintegrin proteins (ADAMs), and tissue inhibitors of metalloproteinases. Gastric differential expression of selected known genes (amphiregulin and ADAM 10) and a novel gene (HPYR1) was confirmed in vivo in patients with H. pylori infection. Confirmation of the in vivo expression of selected genes demonstrates the usefulness of this approach for investigating pathogen-induced changes in host gene expression.

Matrix metalloproteinases: multifunctional effectors of inflammation in multiple sclerosis and bacterial meningitis

Matrix metalloproteinases (MMPs) are a family of Zn2+-dependent endopeptidases targeting extracellular matrix (ECM) compounds as well as a number of other proteins. Their proteolytic activity acts as an effector mechanism of tissue remodeling in physiologic and pathologic conditions, and as modulator of inflammation. In the context of neuro-inflammatory diseases, MMPs have been implicated in processes such as (a) blood-brain barrier (BBB) and blood-nerve barrier opening, (b) invasion of neural tissue by blood-derived immune cells, (c) shedding of cytokines and cytokine receptors, and (d) direct cellular damage in diseases of the peripheral and central nervous system. This review focuses on the role of MMPs in multiple sclerosis (MS) and bacterial meningitis (BM), two neuro-inflammatory diseases where current therapeutic approaches are insufficient to prevent severe disability in the majority of patients. Inhibition of enzymatic activity may prevent MMP-mediated neuronal damage due to an overactive or deviated immune response in both diseases. Downregulation of MMP release may be the molecular basis for the beneficial effect of IFN-beta and steroids in MS. Instead, synthetic MMP inhibitors offer the possibility to shut off enzymatic activity of already activated MMPs. In animal models of MS and BM, they efficiently attenuated clinical disease symptoms and prevented brain damage due to excessive metalloproteinase activity. However, the required target profile for the therapeutic use of this novel group of compounds in human disease is not yet sufficiently defined and may be different depending on the type and stage of disease. Currently available MMP inhibitors show little target-specificity within the MMP family and may lead to side-effects due to interference with physiological functions of MMPs. Results from human MS and BM indicate that only a restricted number of MMPs specific for each disease is up-regulated. MMP inhibitors with selective target profiles offer the possibility of a more efficient therapy of MS and BM and may enter clinical trials in the near future.

Regulation of Membrane Metalloproteolytic Cleavage of L-selectin (CD62L) by the Epidermal Growth Factor Domain

The adhesion molecule L-selectin is cleaved rapidly from the surface of activated leukocytes by tumor necrosis factor-alpha converting enzyme, a cell surface metalloprotease, and also undergoes slower constitutive shedding in unactivated cells. The structural features that render it susceptible to shedding are poorly understood. We therefore analyzed the shedding of a series of mutant and chimeric L-selectin molecules. Although murine L-selectin is cleaved at a specific location in the juxtamembrane region 11 amino acids distal to the cell membrane, this cleavage has little sequence specificity. However, proline substitution at the P2' or P3' position or deletion of the epidermal growth factor (EGF) domain completely blocks the rapid phorbol ester-induced cleavage, but does not affect the slower basal proteolytic shedding. Insertion of the 15-residue membrane-proximal region (MPR) of L-selectin into the heterologous protein B7.2 results in a molecule that undergoes constitutive proteolytic turnover. In contrast, insertion of both the EGF domain and the MPR confers susceptibility to both slow constitutive shedding and the rapid proteolytic cleavage induced by phorbol 12-myristate 13-acetate. These results demonstrate that constitutive and induced L-selectin cleavage are separable processes and that the rapid phorbol ester-induced shedding requires the presence of the EGF domain, a sequence that is remote from the cleavage site.

Astrocyte and endothelial cell expression of ADAM 17 (TACE) in adult human CNS

ADAM 17, also known as TACE, is an important sheddase for a number of proteins, including tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha), L-selectin, p75, and p55 TNF receptors, and interleukin-1 receptor II (IL-1RII). The presence of ADAM 17 mRNA in adult mouse and rat CNS was recently reported (Karkkainen et al. Mol Cell Neurosci 15:547-560, 2000). However, the cellular origin of ADAM 17 remains unknown. In this study, we have used an anti-ADAM 17 antibody in an immunohistochemical study of its distribution in human adult CNS tissue. Cells with astrocytic and endothelial morphology were ADAM 17-positive. This finding was further confirmed using double immunofluorescence with antibodies against GFAP and von Willebrand factor, which label astrocytes and endothelial cells, respectively. This study demonstrates that ADAM 17 is expressed by astrocytes and endothelial cells in normal brain tissue and may have a role in normal brain function.

Antibody-induced shedding of CD44 from adherent cells is linked to the assembly of the cytoskeleton

CD44 is a widely expressed integral membrane glycoprotein that serves as a specific adhesion receptor for the extracellular matrix glycosaminoglycan hyaluronan. CD44 participates in a variety of physiological and pathological processes through its role in cell adhesion. Under appropriate conditions, the ectodomain of CD44 is proteolytically removed from the cell surface. In this study we show that excessive CD44 shedding can be induced in mouse fibroblasts and monocytes upon exposure of these cells to a CD44-specific Ab immobilized on plastic, whereas treatment with phorbol ester induces significantly enhanced CD44 release from the monocytes only. CD44 shedding proceeds normally in fibroblasts and monocytes deficient in TNF-alpha converting enzyme (TACE), a sheddase involved in the processing of several substrates. Conversely, activation of the CD44 protease has no effect on the release of TNF-alpha from TACE-expressing cells, although the same metalloprotease inhibitor effectively blocks both TACE and the CD44 sheddase. Concomitant with anti-CD44 Ab- or phorbol ester-induced CD44 shedding, dramatic changes are observed in cell morphology and the structure of the actin cytoskeleton. Disruption of actin assembly with cytochalasin reduces CD44 shedding, but not the release of TNF-alpha. Moreover, pharmacological activation of Rho family GTPases Rac1 and Cdc42, which regulate actin filament assembly into distinct cytoskeletal structures, has a profound effect on CD44 release. We conclude that the CD44 sheddase and TACE are distinct enzymes, and that Ab- and phorbol ester-enhanced cleavage of CD44 is controlled in a cell type-dependent fashion by Rho GTPases through the cytoskeleton.

Metalloproteinases in biology and pathology of the nervous system

Matrix metalloproteinases (MMPs) and ADAMs (a disintegrin and metalloproteinase) are part of a larger family of structurally related zinc-dependent metalloproteinases called metzincins. Structurally, MMPs are divided in three domains: an amino-terminal propeptide region, an amino-terminal catalytic domain, and a carboxy-terminal domain that is involved in substrate binding. ADAMs have a prodomain, a metalloprotease region, a disintegrin domain for adhesion, a cysteine-rich region, epidermal-growth-factor repeats, a transmembrane module and a cytoplasmic tail. The activity of MMPs is tightly regulated in several ways: at the level of transcription, by post-translational modifications such as proteolysis, and through the action of endogenous tissue inhibitors of metalloproteinases. The regulation of ADAMs is less well understood, although there is some evidence that the same three levels of regulation might control ADAM activity. MMPs and ADAMs have been implicated in neuroinflammation and multiple sclerosis (MS), in the pathogenesis of malignant gliomas, and in other neurological conditions such as stroke, viral infections and Alzheimer's disease. In the case of ADAMs, their role in these pathological states has begun to be explored, but the available literature is still in its infancy. Although the detrimental roles of metalloproteinases are well documented, some of their functions in the central nervous system (CNS) might be beneficial. For example, some metalloproteinases are expressed in the CNS during development, pointing to a possible role in brain maturation. Similarly, metalloproteinases have been implicated in myelinogenesis and axon growth. Furthermore, metalloproteinases are upregulated after injury to the CNS, indicating a possible relevance to tissue repair. Several challenges remain in the study of metalloproteinases and their role in brain function. It will be necessary to understand the balance between the beneficial and detrimental roles of MMPs to determine whether they can be used as targets for therapeutic intervention. It will also be important to identify the physiological substrates of the different metalloproteinases, and to develop selective antagonists against the various members of the metalloproteinase families; the lack of such tools constitutes one of the main limitations to the growth of the field at present.

Matrix metalloproteinases (MMPs) have been implicated in several diseases of the nervous system. Here we review the evidence that supports this idea and discuss the possible mechanisms of MMP action. We then consider some of the beneficial functions of MMPs during neural development and speculate on their roles in repair after brain injury. We also introduce a family of proteins known as ADAMs (a disintegrin and metalloproteinase), as some of the properties previously ascribed to MMPs are possibly the result of ADAM activity.

Tetracyclines inhibit activated B cell function

Tetracyclines have recently been shown to exert a number of pleiotropic anti-inflammatory and immunomodulatory activities, independent of their antibiotic properties. These include the ability to inhibit metalloproteinases (MP), a class of enzymes involved in crucial cellular functions such as the shedding of soluble mediators and their receptors from the cell surface, as well as interaction with, and remodeling of, the extracellular matrix. Here we report that doxycycline at therapeutic concentrations (1--5 microg/ml) significantly suppresses Ig secretion and class switching by in vitro activated murine B cells. Suppression of Ig secretion correlates with a decrease in levels of mRNA for the terminal B cell differentiation-associated genes Blimp-1 and mad-4, as well as to a reduction in expression of the plasma cell markers Syndecan-1 and J chain. Inhibition of class switching occurs at the recombination stage and is also induced by other MP inhibitors, including tetracycline analogs lacking antibiotic activity and the chemically unrelated hydroxamate KB8301. These novel, direct effects of MP inhibitors on B lymphocytes suggest an intrinsic role for MP in B cell activation and likely explain some of the observed in vivo immunomodulatory properties of tetracyclines. Moreover, these findings have significant implications for tetracycline therapy in Ig-mediated autoimmune or allergic diseases and raise questions about the use of doxycycline-inducible transgenic systems for the study of B cell function.

BJ46a, a snake venom metalloproteinase inhibitor. Isolation, characterization, cloning and insights into its mechanism of action

Fractionation of the serum of the venomous snake Bothrops jararaca with (NH4)2SO4, followed by phenyl-Sepharose and C4-reversed phase chromatographies, resulted in the isolation of the anti-hemorrhagic factor BJ46a. BJ46a is a potent inhibitor of the SVMPs atrolysin C (class P-I) and jararhagin (P-III) proteolytic activities and B. jararaca venom hemorrhagic activity. The single-chain, acidic (pI 4.55) glycoprotein has a molecular mass of 46 101 atomic mass units determined by MALDI-TOF MS and 79 kDa by gel filtration and dynamic laser light scattering, suggesting a homodimeric structure. mRNA was isolated from the liver of one specimen and transcribed into cDNA. The cDNA pool was amplified by PCR, cloned into a specific vector and used to transform competent cells. Clones containing the complete coding sequence for BJ46a were isolated. The deduced protein sequence was in complete agreement with peptide sequences obtained by Edman degradation. BJ46a is a 322-amino-acid protein containing four putative N-glycosylation sites. It is homologous to the proteinase inhibitor HSF (member of the fetuin family, cystatin superfamily) isolated from the serum of the snake Trimeresurus flavoviridis, having 85% sequence identity. This is the first report of a complete cDNA sequence for an endogenous inhibitor of snake venom metalloproteinases (SVMPs). The sequence reveals that the only proteolytic processing required to obtain the mature protein is the cleavage of the signal peptide. Gel filtration analyses of the inhibitory complexes indicate that inhibition occurs by formation of a noncovalent complex between BJ46a and the proteinases at their metalloproteinase domains. Furthermore, the data shows that the stoichiometry involved in this interaction is of one inhibitor monomer to two enzyme molecules, suggesting an interesting mechanism of metalloproteinase inhibition.

ADAM17 but not ADAM10 mediates tumor necrosis factor-alpha and L-selectin shedding from leukocyte membranes

The release of tumor necrosis factor-alpha (TNF-alpha) from cellular membranes has been shown by different laboratories to be controlled by a disintegrin and metalloprotease, ADAM10 or ADAM17. In contrast, only ADAM17 has shown to be involved in L-selectin shedding. To determine the specific roles of ADAM10 and ADAM17 in the processing of TNF-alpha and L-selectin shedding, antisense oligonucleotides (ASO) targeting both ADAM10 and ADAM17 were identified. We show that ISIS 16337 reduces ADAM17 mRNA and ISIS 100750 reduces ADAM10 mRNA in a sequence-specific and dose-dependent manner in both Jurkat and THP-1 cells. The ADAM17 ASO (ISIS 16337) inhibited both TNF-alpha secretion in THP-1 cells and L-selectin shedding in Jurkat cells, whereas the ADAM10 ASO (ISIS 100750) did not significantly inhibit release of either protein. These results suggest that ADAM17 is one of the major metalloproteases involved in L-selectin shedding as well as TNF-alpha processing. The biologic substrates for ADAM10 in Jurkat and THP-1 cells remain to be elucidated.

Antigraft antibody-mediated expression of metalloproteinases on endothelial cells. Differential expression of TIMP-1 and ADAM-10 depends on antibody specificity and isotype

Endothelial cell (EC) interaction with antigraft antibodies (Abs) mediates EC injury and activation involved in vascular graft rejection. The aim of this study was to identify EC genes regulated in response to antigraft Ab binding that contribute to the endothelium alterations implicated in graft rejection or survival. By means of RNA differential display, 13 cDNA fragments corresponding to genes differentially expressed in ECs incubated with antigraft Abs were identified. Among these cDNAs were found the tissue inhibitor of metalloproteinase-1 (TIMP-1) and a desintegrin and metalloproteinase (ADAM-10). We demonstrated that TIMP-1 and ADAM-10 mRNA and protein expression was rapidly upregulated in ECs in response to antigraft Ab binding. Our data showed that TIMP-1 was upregulated in response to human IgG but not IgM and anti-galactosyl (Gal) alpha1-3Gal human xenogeneic Abs. In contrast, upregulation of ADAM-10 in ECs was shown to be mostly mediated by anti-Galalpha1-3Gal IgM Abs. Specific effects of human IgG and IgM xenogeneic Abs on endothelial transcripts indicate that different isotypes and specificities of Abs may mediate different EC changes. Our results suggest that interaction of ECs with antigraft Abs, according to their specificity, selectively induces synthesis and release of metalloproteinases and inhibitors, controlling proteolytic processes and immunological events that respectively contribute to graft rejection or survival.

Ectopeptidases in pathophysiology

Ectopeptidases are transmembrane proteins present in a wide variety of tissues and cell types. Dysregulated expression of certain ectopeptidases in human malignancies suggests their value as clinical markers. Ectopeptidase interaction with agonistic antibodies or their inhibitors has revealed that these ectoenzymes are able to modulate bioactive peptide responses and to influence growth, apoptosis and differentiation, as well as adhesion and motility, all functions involved in normal and tumoral processes. There is evidence that ectopeptidase-mediated signal transduction frequently involves tyrosine phosphorylation. Combined analyses of gene organization and regulation of ectopeptidases by various physiological factors have provided insights into their structure-function relationships. Understanding the roles of ectopeptidases in pathophysiology may have implications in considering them as therapeutic targets.

Tumor necrosis factor alpha induces a metalloprotease-disintegrin, ADAM8 (CD 156): implications for neuron-glia interactions during neurodegeneration

ADAM proteases, defined by extracellular disintegrin and metalloprotease domains, are involved in protein processing and cell-cell interactions. Using wobbler (WR) mutant mice, we investigated the role of ADAMs in neurodegeneration and reactive glia activation in the CNS. We found that ADAM8 (CD 156), a suspected leukocyte adhesion molecule, is expressed in the CNS and highly induced in affected CNS areas of WR mice, in brainstem and spinal cord. ADAM8 mRNA and protein are found at low levels throughout the normal mouse CNS, in neurons and oligodendrocytes. In the WR CNS regions in which neurodegeneration occurs, ADAM8 is induced in neurons, reactive astrocytes, and activated microglia. Similarly, the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) is upregulated and shows the same cellular distribution. In primary astrocytes from wild-type and WR mice, in primary cerebellar neurons, and in mouse motoneuron-like NSC19 cells, ADAM8 expression was induced up to 15-fold by mouse TNF-alpha, in a dose-dependent manner. In both cell types, ADAM8 was also induced by human TNF-alpha, indicating that TNF receptor type I (p55) is involved. Induction of ADAM8 mRNA was suppressed by treatment with an interferon-regulating factor 1 (IRF-1) antisense oligonucleotide. We conclude that IRF-1-mediated induction of ADAM8 by TNF-alpha is a signaling pathway relevant for neurodegenerative disorders with glia activation, proposing a role for ADAM8 in cell adhesion during neurodegeneration.

ADAMTS-1: A cellular disintegrin and metalloprotease with thrombospondin motifs is a target for parathyroid hormone in bone

PTH stimulates bone formation in animals and humans, and the expressions of a number of genes have been implicated in the mediation of this effect. To discover new bone factors that initiate and support this phenomenon we used differential display RT-PCR and screened for genes that are selectively expressed in osteoblast-enriched femoral metaphyseal primary spongiosa of young male rats after a single s.c. injection of human PTH-(1-38) (8 microg/100 g). We show that one of the messenger RNAs that is up-regulated in bone is ADAMTS-1, a new member of the ADAM (A disintegrin and metalloprotease) gene family containing thrombospondin type I motifs. ADAMTS-1 consists of multiple domains common to ADAM family of proteins, including pro-, metalloprotease-like, and disintegrin-like domains. However, unlike other ADAMs, ADAMTS-1 does not possess a transmembrane or cytoplasmic domain and is a secreted protein. Northern blot analysis confirmed that ADAMTS-1 was up-regulated in both metaphyseal (14- to 35-fold) and diaphyseal (4.2-fold) bone 1 h after PTH-(1-38) injection and returned to control levels by 24 h. We also analyzed the regulation of ADAMTS-1 in response to various PTH/PTH-related peptide (PTHrP) analogs and found that PTH-(1-31) and PTHrP-(1-34), which activate the protein kinase A (PKA) pathway, induce ADAMTS-1 expression 1 h after injection, whereas PTH-(3-34) and PTH-(7-34), which do not activate the PKA pathway, did not regulate expression. To investigate the effect of other osteotropic agents, we analyzed ADAMTS-1 expression after a single dose of PGE2 (6 mg/kg) and found that it was up-regulated 1 h after injection and returned to control levels by 6 h. In vitro ADAMTS-1 is expressed in primary osteoblasts and osteoblastic cell lines, but was not detectable in osteoclasts generated from macrophage colony-stimulating factor/receptor activator of NF-kappaB ligand/transforming growth factor-beta1-treated bone marrow cells. Treatment of UMR 106 osteosarcoma cells with PTH, PGE2, forskolin, or (Bu)2cAMP increased ADAMTS-1 expression 7-, 4-, 5-, and 5-fold, respectively. Also, in vitro treatment with 1alpha,25-dihydroxyvitamin D3 increased ADAMTS-1 expression 3-fold. Tissue distribution analysis showed that ADAMTS-1 is expressed at high levels in many tissues, including the heart, lung, liver, skeletal muscle, and kidney. Taken together, these results demonstrate that ADAMTS-1 is specifically up-regulated in bone and osteoblasts by the osteotropic agents PTH, PTHrP, and PGE2 possibly via the cAMP/PKA pathway. We speculate that the rapid and transient increase in ADAMTS-1 expression may contribute to some of the effects of PTH on bone turnover.

ADAMTS-1 cleaves a cartilage proteoglycan, aggrecan

A disintegrin-like and metalloproteinase with thrombospondin type I motifs-1 (ADAMTS-1) is an extracellular matrix-anchored metalloproteinase. In this study we have demonstrated that ADAMTS-1 is able to cleave a major cartilage proteoglycan, aggrecan. N-terminal sequencing analysis of the cleavage product revealed that ADAMTS-1 cleaves the Glu(1871)-Leu(1872) bond within the chondroitin sulfate attachment domain of aggrecan. In addition, deletional analysis demonstrated that the C-terminal spacer region of ADAMTS-1 is necessary to degrade aggrecan. These results suggest that ADAMTS-1 may be involved in the turnover of aggrecan in vivo.

Molecular cloning and characterization of a human metalloprotease disintegrin— a novel marker for dendritic cell differentiation

The 1,25-dihydroxyvitamin D3(1,25- [OH]2VD3) modulates the differentiation of monocytic cell lines and monocytes (MOs) in vitro. Up to now several target genes of 1,25(OH)2VD3have been described in monocytic cell lines; however, little is known about target genes in primary MOs. With the Differential Display technique, we found a transcript up-regulated by 1,25(OH)2VD3 in short-term cultured human blood MOs, which we called MADDAM (metalloprotease and disintegrin dendritic antigen marker; EMBL/GenBank/DDBJ accession no. Y13786). Northern blot analysis confirmed this result and revealed a signal of MADDAM messenger RNA (mRNA) at about 7.5 kilobases (kb). Long-term culture (more than 20 hours) of MOs during macrophage (MAC) differentiation led to a rapid and complete down-regulation of MADDAM expression. In contrast, MADDAM expression was maintained in MOs differentiated along the dendritic cell (DC) pathway and induced in CD34+-derived DCs. In addition, in situ hybridization revealed signals of MADDAM mRNA in follicles of human lymph nodes and MADDAM mRNA was detected in freshly isolated human blood-DCs by reverse transcription-polymerase chain reaction (RT-PCR). By means of a database search, we found that MADDAM is a member of the ADAM (a metalloprotease and disintegrin) family, the human homologue to murine meltrin-β (ADAM 19). From these data, we conclude that MADDAM is an important marker for the differentiation and characterization of DCs and the distinction between MACs and DCs.