Cloning and characterization of ADAM28: evidence for autocatalytic pro-domain removal and for cell surface localization of mature ADAM28. Biochem J. 2000;348 Pt 1:21-27. [PMID: 10794709 DOI: 10.1042/bj3480021]

The Biochemistry and Physiology of A Disintegrin and Metalloproteinases (ADAMs and ADAM-TSs) in Human Pathologies

Metalloproteinases are a group of proteinases that plays a substantial role in extracellular matrix remodeling and its molecular signaling. Among these metalloproteinases, ADAMs (a disintegrin and metalloproteinases) and ADAM-TSs (ADAMs with thrombospondin domains) have emerged as highly efficient contributors mediating proteolytic processing of various signaling molecules. ADAMs are transmembrane metalloenzymes that facilitate the extracellular domain shedding of membrane-anchored proteins, cytokines, growth factors, ligands, and their receptors and therefore modulate their biological functions. ADAM-TSs are secretory, and soluble extracellular proteinases that mediate the cleavage of non-fibrillar extracellular matrix proteins. ADAMs and ADAM-TSs possess pro-domain, metalloproteinase, disintegrin, and cysteine-rich domains in common, but ADAM-TSs have characteristic thrombospondin motifs instead of the transmembrane domain. Most ADAMs and ADAM-TSs are activated by cleavage of pro-domain via pro-protein convertases at their N-terminus, hence directing them to various signaling pathways. In this article, we are discussing not only the structure and regulation of ADAMs and ADAM-TSs, but also the importance of these metalloproteinases in various human pathophysiological conditions like cardiovascular diseases, colorectal cancer, autoinflammatory diseases (sepsis/rheumatoid arthritis), Alzheimer's disease, proliferative retinopathies, and infectious diseases. Therefore, based on the emerging role of ADAMs and ADAM-TSs in various human pathologies, as summarized in this review, these metalloproteases can be considered as critical therapeutic targets and diagnostic biomarkers.

Sperm acquire epididymis-derived proteins through epididymosomes

STUDY QUESTION

Are epididymosomes implicated in protein transfer from the epididymis to spermatozoa?

SUMMARY ANSWER

We characterized the contribution of epididymal secretions to the sperm proteome and demonstrated that sperm acquire epididymal proteins through epididymosomes.

WHAT IS KNOWN ALREADY

Testicular sperm are immature cells unable to fertilize an oocyte. After leaving the testis, sperm transit along the epididymis to acquire motility and fertilizing abilities. It is well known that marked changes in the sperm proteome profile occur during epididymal maturation. Since the sperm is a transcriptional and translational inert cell, previous studies have shown that sperm incorporate proteins, RNA and lipids from extracellular vesicles (EVs), released by epithelial cells lining the male reproductive tract.

STUDY DESIGN, SIZE, DURATION

We examined the contribution of the epididymis to the post-testicular maturation of spermatozoa, via the production of EVs named epididymosomes, released by epididymal epithelial cells. An integrative analysis using both human and mouse data was performed to identify sperm proteins with a potential epididymis-derived origin. Testes and epididymides from adult humans (n = 9) and adult mice (n = 3) were used to experimentally validate the tissue localization of four selected proteins using high-resolution confocal microscopy. Mouse epididymal sperm were co-incubated with carboxyfluorescein succinimidyl ester (CFSE)-labeled epididymosomes (n = 4 mice), and visualized using high-resolution confocal microscopy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adult (12-week-old) C57BL/CBAF1 wild-type male mice and adult humans were used for validation purposes. Testes and epididymides from both mice and humans were obtained and processed for immunofluorescence. Mouse epididymal sperm and mouse epididymosomes were obtained from the epididymal cauda segment. Fluorescent epididymosomes were obtained after labeling the epididymal vesicles with CFSE dye followed by epididymosome isolation using a density cushion. Immunofluorescence was performed following co-incubation of sperm with epididymosomes in vitro. High-resolution confocal microscopy and 3D image reconstruction were used to visualize protein localization and sperm-epididymosomes interactions.

MAIN RESULTS AND THE ROLE OF CHANCE

Through in silico analysis, we first identified 25 sperm proteins with a putative epididymal origin that were conserved in both human and mouse spermatozoa. From those, the epididymal origin of four sperm proteins (SLC27A2, EDDM3B, KRT19 and WFDC8) was validated by high-resolution confocal microscopy. SLC27A2, EDDM3B, KRT19 and WFDC8 were all detected in epithelial cells lining the human and mouse epididymis, and absent from human and mouse seminiferous tubules. We found region-specific expression patterns of these proteins throughout the mouse epididymides. In addition, while EDDM3B, KRT19 and WFDC8 were detected in both epididymal principal and clear cells (CCs), SLC27A2 was exclusively expressed in CCs. Finally, we showed that CFSE-fluorescently labeled epididymosomes interact with sperm in vitro and about 12-36% of the epididymosomes contain the targeted sperm proteins with an epididymal origin.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The human and mouse sample size was limited and our results were descriptive. The analyses of epididymal sperm and epididymosomes were solely performed in the mouse model due to the difficulties in obtaining epididymal luminal fluid human samples. Alternatively, human ejaculated sperm and seminal EVs could not be used because ejaculated sperm have already contacted with the fluids secreted by the male accessory sex glands, and seminal EVs contain other EVs in addition to epididymosomes, such as the abundant prostate-derived EVs.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that epididymosomes are capable of providing spermatozoa with a new set of epididymis-derived proteins that could modulate the sperm proteome and, subsequently, participate in the post-testicular maturation of sperm cells. Additionally, our data provide further evidence of the novel role of epididymal CCs in epididymosome production. Identifying mechanisms by which sperm mature to acquire their fertilization potential would, ultimately, lead to a better understanding of male reproductive health and may help to identify potential therapeutic strategies to improve male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competividad; fondos FEDER 'una manera de hacer Europa' PI13/00699 and PI16/00346 to R.O.; and Sara Borrell Postdoctoral Fellowship, Acción Estratégica en Salud, CD17/00109 to J.C.), by National Institutes of Health (grants HD040793 and HD069623 to S.B., grant HD104672-01 to M.A.B.), by the Spanish Ministry of Education, Culture and Sports (Ministerio de Educación, Cultura y Deporte para la Formación de Profesorado Universitario, FPU15/02306 to F.B.), by a Lalor Foundation Fellowship (to F.B. and M.A.B.), by the Government of Catalonia (Generalitat de Catalunya, pla estratègic de recerca i innovació en salut, PERIS 2016-2020, SLT002/16/00337 to M.J.), by Fundació Universitària Agustí Pedro i Pons (to F.B.), and by the American Society for Biochemistry and Molecular Biology (PROLAB Award from ASBMB/IUBMB/PABMB to F.B.). Confocal microscopy and transmission electron microscopy was performed in the Microscopy Core facility of the Massachusetts General Hospital (MGH) Center for Systems Biology/Program in Membrane Biology which receives support from Boston Area Diabetes and Endocrinology Research Center (BADERC) award DK57521 and Center for the Study of Inflammatory Bowel Disease grant DK43351. The Zeiss LSM800 microscope was acquired using an NIH Shared Instrumentation Grant S10-OD-021577-01. The authors have no conflicts of interest to declare.

ADAM28: Another ambivalent protease in cancer

Emergence of novel therapeutic options in a perspective of personalized therapy of cancer relies on the discovery of precise molecular mechanisms involved in the switch from a localized tumor to invasive metastasis spread. Pro-tumor functions have been mostly ascribed to proteolytic enzymes from the metalloproteinase family including A Disintegrin And Metalloproteinases (ADAMs). Particularly, when expressed by cancer cells, ADAM28 protease supports cancer cell proliferation, survival and migration as well as metastatic progression. In sharp contrast, ADAM28 derived from the tumor microenvironment has shown to exert strong protective effects against deleterious metastasis dissemination. Indeed, depletion of host-derived ADAM28 (ADAM28 KO mice) accelerates colonization lung tissues, increases tumor foci implantation, and impairs T cell immune response. In this review, we outline specific ADAM28 functions when specifically expressed by carcinoma cells or by tumor microenvironment. Finally, we discuss about future research strategies that could be pursued to highlight new functions of this protease in cancer.

Protease propeptide structures, mechanisms of activation, and functions

Proteases are a diverse group of hydrolytic enzymes, ranging from single-domain catalytic molecules to sophisticated multi-functional macromolecules. Human proteases are divided into five mechanistic classes: aspartate, cysteine, metallo, serine and threonine proteases, based on the catalytic mechanism of hydrolysis. As a protective mechanism against uncontrolled proteolysis, proteases are often produced and secreted as inactive precursors, called zymogens, containing inhibitory N-terminal propeptides. Protease propeptide structures vary considerably in length, ranging from dipeptides and propeptides of about 10 amino acids to complex multifunctional prodomains with hundreds of residues. Interestingly, sequence analysis of the different protease domains has demonstrated that propeptide sequences present higher heterogeneity compared with their catalytic domains. Therefore, we suggest that protease inhibition targeting propeptides might be more specific and have less off-target effects than classical inhibitors. The roles of propeptides, besides keeping protease latency, include correct folding of proteases, compartmentalization, liganding, and functional modulation. Changes in the propeptide sequence, thus, have a tremendous impact on the cognate enzymes. Small modifications of the propeptide sequences modulate the activity of the enzymes, which may be useful as a therapeutic strategy. This review provides an overview of known human proteases, with a focus on the role of their propeptides. We review propeptide functions, activation mechanisms, and possible therapeutic applications.

Regulation of Fibrotic Processes in the Liver by ADAM Proteases

Fibrosis in the liver is mainly associated with the activation of hepatic stellate cells (HSCs). Both activation and clearance of HSCs can be mediated by ligand–receptor interactions. Members of the a disintegrin and metalloprotease (ADAM) family are involved in the proteolytic release of membrane-bound ligands and receptor ectodomains and the remodelling of the extracellular matrix. ADAM proteases are therefore major regulators of intercellular signalling pathways. In the present review we discuss how ADAM proteases modulate pro- and anti-fibrotic processes and how ADAM proteases might be harnessed therapeutically in the future.

Oncogenic ADAM28 induces gemcitabine resistance and predicts a poor prognosis in pancreatic cancer

BACKGROUND

Pancreatic cancer is a major cause of cancer-related death, with a 5-year overall survival rate being below 5%. The main causes of poor prognosis in pancreatic cancer include easy metastasis, high recurrence rate, and robust drug resistance. Gemcitabine is a first-line drug for patients with unresectable pancreatic cancer. However, due to drug resistance, the clinical effect is not satisfactory. ADAM28 is reported as a tumor promoter in some cancers, but its role in pancreatic cancer and gemcitabine chemoresistance in pancreatic cancer has not been elucidated.

AIM

To identify if ADAM28 can act as an important target to reverse the gemcitabine drug resistance in pancreatic cancer.

METHODS

RNA-sequence analysis was applied to explore the potential targets involved in the gemcitabine of pancreatic cancer. SW1990 pancreatic cancer cells were treated with an increased dose of gemcitabine, and the mRNA levels of ADAM28 were evaluated by RT-PCR. The protein and mRNA levels of ADAM28 were confirmed in the gemcitabine resistant and parallel SW1990 cells. The ADAM28 expression was also assessed in TCGA and GEO databases, and the results were confirmed in the collected tumor and adjacent normal tissues. The overall survival (OS) rate and relapse-free survival (RFS) rate of pancreatic cancer patients with high ADAM28 level and low ADAM28 level in TCGA were evaluated with Kaplan-Meier Plotter. Furthermore, the OS rate was calculated in pancreatic cancer patients with high tumor mutation burden (TMB) and low TMB. CCK-8 assay was used to examine the effect of ADAM28 on the viability of SW1990 cells. The ADAM28 and its co-expressed genes were analyzed in the cBioPortal for cancer genomics and subjected to GSEA pathway analysis. The correlations of ADAM28 with GSTP1, ABCC1, GSTM4, and BCL2 were analyzed based on TCGA data on pancreatic cancer.

RESULTS

RNA-sequence analysis identified that ADAM28 was overexpressed in gemcitabine-resistant cells, and gemcitabine treatment could induce the expression of ADAM28. The mRNA and protein levels of ADAM28 were elevated in gemcitabine-resistant SW1990 cells compared with parallel cells. Also, the expression of ADAM28 was upregulated in pancreatic tumor tissues against normal pancreatic tissues. Notably, ADAM28 was highly expressed in the classical type than in the basal tumor type. Furthermore, the high expression of ADAM28 was associated with low OS and RFS rates. Interestingly, the high levels of ADAM28 was associated with a significantly lower OS rate in the high TMB patients, but not in the low TMB patients. Moreover, overexpression of ADAM28 could reduce the cell viability inhibition by gemcitabine, and knockdown of ADAM28 could enhance the proliferation inhibition by gemcitabine. The GSEA analysis showed that ADAM28 was related to the regulation of drug metabolism, and ADAM28 was significantly positively correlated with GSTP1, ABCC1, GSTM4, and BCL2.

CONCLUSION

This study demonstrates that ADAM28 is overexpressed in pancreatic cancer, and closely involved in the regulation of gemcitabine resistance. Overexpression of ADAM28 is a novel prognostic biomarker in pancreatic cancer.

ADAM Metalloproteinases as Potential Drug Targets

The ADAMs, together with ADAMTSs and snake venom metalloproteases (SVMPs), are members of the Adamalysin family. Differences in structural organization, functions and localization are known and their domains, catalytic or non-catalytic, show key roles in the substrate recognition and protease activity. Some ADAMs, as membrane-bound enzymes, show sheddase activity. Sheddases are key to modulation of functional proteins such as the tumor necrosis factor, growth factors, cytokines and their receptors, adhesion proteins, signaling molecules and stress molecules involved in immunity. These activities take part in the regulation of several physiological and pathological processes including inflammation, tumor growth, metastatic progression and infectious diseases. On these bases, some ADAMs are currently investigated as drug targets to develop new alternative therapies in many fields of medicine. This review will be focused on these aspects.

ADAM9 contributes to vascular invasion in pancreatic ductal adenocarcinoma

A disintegrin and a metalloprotease (ADAM)‐9 is a metzincin cell‐surface protease with strongly elevated expression in solid tumors, including pancreatic ductal adenocarcinoma (PDAC). In this study, we performed immunohistochemistry (IHC) of a tissue microarray (TMA) to examine the expression of ADAM9 in a cohort of >100 clinically annotated PDAC cases. We report that ADAM9 is prominently expressed by PDAC tumor cells, and increased ADAM9 expression levels correlate with poor tumor grading (P = 0.027) and the presence of vasculature invasion (P = 0.017). We employed gene expression silencing to generate a loss‐of‐function system for ADAM9 in two established PDAC cell lines. In vitro analysis showed that loss of ADAM9 does not impede cellular proliferation and invasiveness in basement membrane. However, ADAM9 plays a crucial role in mediating cell migration and adhesion to extracellular matrix substrates such as fibronectin, tenascin, and vitronectin. This effect appears to depend on its catalytic activity. In addition, ADAM9 facilitates anchorage‐independent growth. In AsPC1 cells, but not in MiaPaCa‐2 cells, we noted a pronounced yet heterogeneous impact of ADAM9 on the abundance of various integrins, a process that we characterized as post‐translational regulation. Sprout formation of human umbilical vein endothelial cells (HUVECs) is promoted by ADAM9, as examined by transfer of cancer cell conditioned medium; this finding further supports a pro‐angiogenic role of ADAM9 expressed by PDAC cancer cells. Immunoblotting analysis of cancer cell conditioned medium highlighted that ADAM9 regulates the levels of angiogenic factors, including shed heparin‐binding EGF‐like growth factor (HB‐EGF). Finally, we carried out orthotopic seeding of either wild‐type AsPC‐1 cells or AsPC‐1 cells with silenced ADAM9 expression into murine pancreas. In this in vivo setting, ADAM9 was also found to foster angiogenesis without an impact on tumor cell proliferation. In summary, our results characterize ADAM9 as an important regulator in PDAC tumor biology with a strong pro‐angiogenic impact.

ADAM28 promotes tumor growth and dissemination of acute myeloid leukemia through IGFBP-3 degradation and IGF-I-induced cell proliferation

ADAM28 has been shown to relate with tumor proliferation and prognosis. The expression of ADAM28 is up-regulated in acute myeloid leukemia (AML). However, the mechanism by which ADAM28 regulates the leukemic cell and the prognostic relevance with AML remain unknown. Here, we found that the expression level of ADAM28 was significantly elevated in AML patients suffering a relapse compared with those remaining in complete remission (CR). ADAM28 promoted the proliferation, migration and invasion in leukemic cells in vitro. Additionally, the increased expression of ADAM28 led to more IGFBP-3 degradation and IGF-I-induced cell proliferation. In a xenotransplantation mouse model, knockout of ADAM28 alleviated HL-60 cells growth and dissemination. The cumulative incidence of relapse (CIR) was significantly higher in patients with high ADAM28 expression. When separately considering the impact of ADAM28 on prognosis within the risk stratifications, patients with high ADAM28 expression levels had a significantly higher CIR in the favorable and intermediate-risk group but not in poor-risk group. Taken together, these data suggest a pivotal role for ADAM28 in regulating the proliferation and invasion of leukemic cells and in the prediction of relapse in AML patients.

Selective Inhibition of ADAM28 Suppresses Lung Carcinoma Cell Growth and Metastasis

ADAM28 (a disintegrin and metalloproteinase 28) is overexpressed by carcinoma cells in non-small cell lung carcinomas (NSCLC) and plays an important role in cancer cell proliferation and metastasis by reactivation of insulin-like growth factor-1 (IGF-1) and escaping from von Willebrand factor (VWF)-induced apoptosis through digestion of IGF-binding protein-3 and VWF, respectively. To aim for new target therapy of NSCLC patients, we developed human neutralizing antibodies 211-12 and 211-14 against ADAM28, which showed IC₅₀ values of 62.4 and 37.5 nmol/L, respectively. Antibody 211-14 recognized the junctional region between cysteine-rich domain and secreted-specific domain and showed a K_D value of 94.7 pmol/L for the epitope-containing peptide. This antibody detected monkey and human secreted-form ADAM28s, although it was not reactive with mouse membrane-anchored ADAM28m. Antibody 211-14 effectively inhibited IGF-1-stimulated cell proliferation of lung adenocarcinoma cell lines with ADAM28 expression, including PC-9 cells, and promoted VWF-induced cell death in these cell lines. In lung metastasis models, antibody 211-14 significantly reduced tumor growth and metastases of PC-9 cells and prolonged survivals in the antibody-treated mice compared with the control IgG-treated ones. Combination therapy of the antibody and docetaxel was more effective than that of bevacizumab and docetaxel and showed further elongation of survival time compared with monotherapy. No adverse effects were observed even after administration of 10-fold more than effective dose of anti-ADAM28 antibody to normal mice. Our data demonstrate that antibody 211-14 is a neutralizing antibody specific to ADAM28s and suggest that this antibody may be a useful treatment remedy for NSCLC patients. Mol Cancer Ther; 17(11); 2427-38. ©2018 AACR.

The Many Facets of Metzincins and Their Endogenous Inhibitors: Perspectives on Ovarian Cancer Progression

Approximately sixty per cent of ovarian cancer patients die within the first five years of diagnosis due to recurrence associated with chemoresistance. The metzincin family of metalloproteinases is enzymes involved in matrix remodeling in response to normal physiological changes and diseased states. Recently, there has been a mounting awareness of these proteinases and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), as superb modulators of cellular communication and signaling regulating key biological processes in cancer progression. This review investigates the role of metzincins and their inhibitors in ovarian cancer. We propose that understanding the metzincins and TIMP biology in ovarian cancer may provide valuable insights in combating ovarian cancer progression and chemoresistance-mediated recurrence in patients.

Multiple non-catalytic ADAMs are novel integrin α4 ligands

The ADAM (a disintegrin and metalloprotease) protein family uniquely exhibits both catalytic and adhesive properties. In the well-defined process of ectodomain shedding, ADAMs transform latent, cell-bound substrates into soluble, biologically active derivatives to regulate a spectrum of normal and pathological processes. In contrast, the integrin ligand properties of ADAMs are not fully understood. Emerging models posit that ADAM-integrin interactions regulate shedding activity by localizing or sequestering the ADAM sheddase. Interestingly, 8 of the 21 human ADAMs are predicted to be catalytically inactive. Unlike their catalytically active counterparts, integrin recognition of these "dead" enzymes has not been largely reported. The present study delineates the integrin ligand properties of a group of non-catalytic ADAMs. Here we report that human ADAM11, ADAM23, and ADAM29 selectively support integrin α4-dependent cell adhesion. This is the first demonstration that the disintegrin-like domains of multiple catalytically inactive ADAMs are ligands for a select subset of integrin receptors that also recognize catalytically active ADAMs.

ADAM28 localizes to HLA-G+ trophoblasts and promotes column cell outgrowth

INTRODUCTION

Trophoblast progenitor cell differentiation towards the extravillous trophoblast (EVT) lineage initiates within proximal regions of anchoring columns of first trimester placental villi. While molecular processes controlling the initial stages of progenitor cell differentiation along the EVT pathway have been described, much remains unknown about factors important in distal column cell differentiation into invasive EVTs. ADAMs are proteases that regulate growth factor signaling, cell-matrix adhesion, and matrix proteolysis, and thus impact many processes relevant in placentation. Global gene expression studies identified the ADAM subtype, ADAM28, to be highly expressed in EVT-like trophoblasts, suggesting that it may play a role in EVT function. This study aims to test the functional importance of ADAM28 in column cell outgrowth and maintenance.

METHODS

ADAM28 mRNA levels and protein localization were determined by qPCR and immunofluorescence microscopy analyses in purified placental villi cell populations and tissues. ADAM28 function in trophoblast column outgrowth was examined using ADAM28-targetting siRNAs in Matrigel-imbedded placental explant cultures.

RESULTS

Within placental villi, ADAM28 mRNA levels were highest in HLA-G⁺ column trophoblasts, and consistent with this, ADAM28 was preferentially localized to HLA-G⁺ trophoblasts within distal anchoring columns and decidual tissue. siRNA-directed loss of ADAM28 impaired trophoblast column outgrowth and resulted in increased apoptosis in matrix-invading trophoblasts.

DISCUSSION

Our findings suggest that ADAM28 promotes column outgrowth by providing survival cues within anchoring column cells. This study also provides insight into a possible role for ADAM28 in driving differentiation of column trophoblasts into invasive HLA-G⁺ EVT subsets.

Overexpression and knock-down studies highlight that a disintegrin and metalloproteinase 28 controls proliferation and migration in human prostate cancer

Prostate cancer is one of the most prevalent cancers in men. It is critical to identify and characterize oncogenes that drive the pathogenesis of human prostate cancer. The current study builds upon previous research showing that a disintegrin and metallproteinase (ADAM)28 is involved in the pathogenesis of numerous cancers. Our novel study used overexpression, pharmacological, and molecular approaches to investigate the biological function of ADAM28 in human prostate cancer cells, with a focus on cell proliferation and migration. The results of this study provide important insights into the role of metalloproteinases in human prostate cancer.The expression of ADAM28 protein levels was assessed within human prostate tumors and normal adjacent tissue by immunohistochemistry. Immunocytochemistry and western blotting were used to assess ADAM28 protein expression in human prostate cancer cell lines. Functional assays were conducted to assess proliferation and migration in human prostate cancer cells in which ADAM28 protein expression or activity had been altered by overexpression, pharmacological inhibition, or by siRNA gene knockdown.The membrane bound ADAM28 was increased in human tumor biopsies and prostate cancer cell lines. Pharmacological inhibition of ADAM28 activity and/or knockdown of ADAM28 significantly reduced proliferation and migration of human prostate cancer cells, while overexpression of ADAM28 significantly increased proliferation and migration.ADAM28 is overexpressed in primary human prostate tumor biopsies, and it promotes human prostate cancer cell proliferation and migration. This study supports the notion that inhibition of ADAM28 may be a potential novel therapeutic strategy for human prostate cancer.

Processing of Snake Venom Metalloproteinases: Generation of Toxin Diversity and Enzyme Inactivation

Snake venom metalloproteinases (SVMPs) are abundant in the venoms of vipers and rattlesnakes, playing important roles for the snake adaptation to different environments, and are related to most of the pathological effects of these venoms in human victims. The effectiveness of SVMPs is greatly due to their functional diversity, targeting important physiological proteins or receptors in different tissues and in the coagulation system. Functional diversity is often related to the genetic diversification of the snake venom. In this review, we discuss some published evidence that posit that processing and post-translational modifications are great contributors for the generation of functional diversity and for maintaining latency or inactivation of enzymes belonging to this relevant family of venom toxins.

The ADAMs family of proteases as targets for the treatment of cancer

The ADAMs (a disintegrin and metalloproteases) are transmembrane multidomain proteins implicated in multiple biological processes including proteolysis, cell adhesion, cell fusion, cell proliferation and cell migration. Of these varied activities, the best studied is their role in proteolysis. However, of the 22 ADAMs believed to be functional in humans, only approximately a half possess matrix metalloproteinase (MMP)-like protease activity. In contrast to MMPs which are mostly implicated in the degradation of extracellular matrix proteins, the main ADAM substrates are the ectodomains of type I and type II transmembrane proteins. These include growth factor/cytokine precursors, growth factor/cytokine receptors and adhesion proteins. Recently, several different ADAMs, especially ADAM17, have been shown to play a role in the development and progression of multiple cancer types. Consistent with this role in cancer, targeting ADAM17 with either low molecular weight inhibitors or monoclonal antibodies was shown to have anti-cancer activity in multiple preclinical systems. Although early phase clinical trials have shown no serious side effects with a dual ADAM10/17 low molecular weight inhibitor, the consequences of long-term treatment with these agents is unknown. Furthermore, efficacy in clinical trials remains to be shown.

ADAM28 is expressed by epithelial cells in human normal tissues and protects from C1q-induced cell death

ADAM28 (disintegrin and metalloproteinase 28), which was originally reported to be lymphocyte-specific, is over-expressed by carcinoma cells and plays a key role in cell proliferation and progression in human lung and breast carcinomas. We studied ADAM28 expression in human normal tissues and examined its biological function. By using antibodies specific to ADAM28, ADAM28 was immunolocalized mainly to epithelial cells in several tissues, including epididymis, bronchus and stomach, whereas lymphocytes in lymph nodes and spleen were negligibly immunostained. RT-PCR, immunoblotting and ELISA analyses confirmed the expression in these tissues, and low or negligible expression by lymphocytes was found in the lymph node and spleen. C1q was identified as a candidate ADAM28-binding protein from a human lung cDNA library by yeast two-hybrid system, and specific binding was demonstrated by binding assays, immunoprecipitation and surface plasmon resonance. C1q treatment of normal bronchial epithelial BEAS-2B and NHBE cells, both of which showed low-level expression of ADAM28, caused apoptosis through activation of p38 and caspase-3, and cell death with autophagy through accumulation of LC3-II and autophagosomes, respectively. C1q-induced cell death was attenuated by treatment of the cells with antibodies against the C1q receptor gC1qR/p33 or cC1qR/calreticulin. Treatment of C1q with recombinant ADAM28 prior to addition to culture media reduced C1q-induced cell death, and knockdown of ADAM28 using siRNAs increased cell death. These data demonstrate that ADAM28 is expressed by epithelial cells of several normal organs, and suggest that ADAM28 plays a role in cell survival by suppression of C1q-induced cytotoxicity in bronchial epithelial cells.

ADAMs family and relatives in cardiovascular physiology and pathology

A disintegrin and metalloproteinases (ADAMs) are a family of membrane-bound proteases. ADAM-TSs (ADAMs with thrombospondin domains) are a close relative of ADAMs that are present in soluble form in the extracellular space. Dysregulated production or function of these enzymes has been associated with pathologies such as cancer, asthma, Alzheimer's and cardiovascular diseases. ADAMs contribute to angiogenesis, hypertrophy and apoptosis in a stimulus- and cell type-dependent manner. Among the ADAMs identified so far (34 in mouse, 21 in human), ADAMs 8, 9, 10, 12, 17 and 19 have been shown to be involved in cardiovascular development or cardiomyopathies; and among the 19 ADAM-TSs, ADAM-TS1, 5, 7 and 9 are important in development of the cardiovascular system, while ADAM-TS13 can contribute to vascular disorders. Meanwhile, there remain a number of ADAMs and ADAM-TSs whose function in the cardiovascular system has not been yet explored. The current knowledge about the role of ADAMs and ADAM-TSs in the cardiovascular pathologies is still quite limited. The most detailed studies have been performed in other cell types (e.g. cancer cells) and organs (nervous system) which can provide valuable insight into the potential functions of ADAMs and ADAM-TSs, their mechanism of action and therapeutic potentials in cardiomyopathies. Here, we review what is currently known about the structure and function of ADAMs and ADAM-TSs, and their roles in development, physiology and pathology of the cardiovascular system.

ADAM28 overexpression regulated via the PI3K/Akt pathway is associated with relapse in de novo adult B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) in adults is a very challenging disease. Relapse following remission after induction chemotherapy remains the major barrier to patient survival. ADAM28 is overexpressed in several human tumors and is related to cell proliferation and lymph node metastasis. To date, no information has been available on the prognostic role of ADAM28 in B-ALL. Fifty consecutive patients with de novo B-ALL and 22 healthy donors were enrolled in this study and were followed for 2.8 years. Our data suggested that ADAM28 expression in B-ALL patients was significantly increased (P<0.0001). Patients experiencing disease relapse exhibited significantly increased ADAM28 expression, compared with those with favorable outcomes (P=0.0094). Notably, ADAM28 overexpression was associated with lower probabilities of relapse-free survival (RFS) and event-free survival (EFS) (P<0.001) and was a significant prognostic factor (P<0.001). In vitro, the PI3K/Akt pathway inhibitor, as well as arsenic trioxide (ATO), down-regulated ADAM28 expression. Our results were the first to indicate that ADAM28 overexpression in B-ALL patients is correlated with relapse. ADAM28 overexpression is potentially regulated by the PI3K/Akt pathway. These data demonstrate that ADAM28 might serve as a novel biomarker for evaluating relapse in B-ALL and as a potential therapeutic target in B-ALL patients.

The Functional Maturation of A Disintegrin and Metalloproteinase (ADAM) 9, 10, and 17 Requires Processing at a Newly Identified Proprotein Convertase (PC) Cleavage Site

Proenzyme maturation is a general mechanism to control the activation of enzymes. Catalytically active members of the A Disintegrin And Metalloprotease (ADAM) family of membrane-anchored metalloproteases are synthesized as proenzymes, in which the latency is maintained by their autoinhibitory pro-domains. A proteolytic processing then transforms the proenzyme into a catalytically active form. The removal of the pro-domain of ADAMs is currently thought to depend on processing at a canonical consensus site for the proprotein convertase Furin (RXXR) between the pro- and the catalytic domain. Here, we demonstrate that this previously described canonical site is a secondary cleavage site to a prerequisite cleavage in a newly characterized upstream PC site embedded within the pro-domain sequence. The novel upstream regulatory site is important for the maturation of several ADAM proenzymes. Mutations in the upstream regulatory site of ADAM17, ADAM10, and ADAM9 do not prevent pro-domain processing between the pro- and metalloprotease domain, but nevertheless, cause significantly reduced catalytic activity. Thus, our results have uncovered a novel functionally relevant PC processing site in the N-terminal part of the pro-domain that is important for the activation of these ADAMs. These results suggest that the novel PC site is part of a general mechanism underlying proenzyme maturation of ADAMs that is independent of processing at the previously identified canonical Furin cleavage site.

Differential expression and localization of ADAM10 and ADAM17 during rat spermatogenesis suggest a role in germ cell differentiation

Background

Extracellular metolloproteases have been implied in different process such as cell death, differentiation and migration. Membrane-bound metalloproteases of the ADAM family shed the extracellular domain of many cytokines and receptor controlling auto and para/juxtacrine cell signaling in different tissues. ADAM17 and ADAM10 are two members of this family surface metalloproteases involved in germ cell apoptosis during the first wave of spermatogenesis in the rat, but they have other signaling functions in somatic tissues.

Results

In an attempt to further study these two enzymes, we describe the presence and localization in adult male rats. Results showed that both enzymes are detected in germ and Sertoli cells during all the stages of spermatogenesis. Interestingly their protein levels and cell surface localization in adult rats were stage-specific, suggesting activation of these enzymes at particular events of rat spermatogenesis.

Conclusions

Therefore, these results show that ADAM10 and ADAM17 protein levels and subcellular (cell surface) localization are regulated during rat spermatogenesis.

Alternative mRNA splicing generates two distinct ADAM12 prodomain variants

Human ADAM12, transcript variant 1 (later on referred to as Var-1b), present in publicly available databases contains the sequence 5′-GTAATTCTG-3′ at the nucleotide positions 340–348 of the coding region, at the 3′ end of exon 4. The translation product of this variant, ADAM12-Lb, includes the three amino acid motif ¹¹⁴VIL¹¹⁶ in the prodomain. This motif is not conserved in ADAM12 from different species and is not present in other human ADAMs. Currently, it is not clear whether a shorter variant, Var-1a, encoding the protein version without the ¹¹⁴VIL¹¹⁶ motif, ADAM12-La, is expressed in human. In this work, we have established that human mammary epithelial cells and breast cancer cells express both Var-1a and Var-1b transcripts. Importantly, the proteolytic processing and intracellular trafficking of the corresponding ADAM12-La and ADAM12-Lb proteins are different. While ADAM12-La is cleaved and trafficked to the cell surface in a manner similar to ADAM12 in other species, ADAM12-Lb is retained in the ER and is not proteolytically processed. Furthermore, the relative abundance of ADAM12-La and ADAM12-Lb proteins detected in several breast cancer cell lines varies significantly. We conclude that the canonical form of transmembrane ADAM12 is represented by Var-1a/ADAM12-La, rather than Var-1b/ADAM12-Lb currently featured in major sequence databases.

ADAMDEC1 is a metzincin metalloprotease with dampened proteolytic activity

ADAMDEC1 (Decysin-1) is a putative ADAM (a disintegrin and metalloprotease)-like metalloprotease with an unknown physiological role, selectively expressed in mature dendritic cells and macrophages. When compared with other members of the ADAM family, ADAMDEC1 displays some unusual features. It lacks the auxiliary cysteine-rich, EGF, and transmembrane domains, as well as the cytoplasmic tail. The active site of ADAMDEC1 is unique by being the only mammalian ADAM protease with a non-histidine zinc ligand, having an aspartic acid residue instead. Here we demonstrate that ADAMDEC1, despite these unique features, functions as an active metalloprotease. Thus, ADAMDEC1 is secreted as a mature, glycosylated, and proteolytically active metalloprotease, capable of cleaving macromolecular substrates. In the recombinant form, three of the four potential N-linked glycosylation sites are modified by carbohydrate attachment. Substitution of basic residues at the predicted proprotein convertase cleavage site blocks proprotein processing, revealing both specific ADAMDEC1-dependent and specific ADAMDEC1-independent cleavage of the prodomain. The pro-form of ADAMDEC1 does not have proteolytic activity, demonstrating that the prodomain of ADAMDEC1, like in other members of the ADAM family, confers catalytic latency. Interestingly, the proteolytic activity of mature ADAMDEC1 can be significantly enhanced when a canonical ADAM active site with three zinc-coordinating histidine residues is introduced.

Ectodomain shedding and ADAMs in development

Proteolytic enzymes belonging to the A Disintegin And Metalloproteinase (ADAM) family are able to cleave transmembrane proteins close to the cell surface, in a process referred to as ectodomain shedding. Substrates for ADAMs include growth factors, cytokines, chemokines and adhesion molecules, and, as such, many ADAM proteins play crucial roles in cell-cell adhesion, extracellular and intracellular signaling, cell differentiation and cell proliferation. In this Review, we summarize the fascinating roles of ADAMs in embryonic and adult tissue development in both vertebrates and invertebrates.

Role of ADAM33 gene and associated single nucleotide polymorphisms in asthma

Asthma is a multifactorial disorder, primarily resulting from interactions between genetic and environmental factors. ADAM33 gene (located on chromosome 20p13) has been reported to play an important role in asthma. This review article is intended to include all of the publications, to date, which have assessed the association of ADAM33 gene polymorphisms as well as have shown the role of ADAM33 gene in airway remodeling and their expression with asthma. A PubMed search was performed for studies published between 1990 and 2010. The terms “ADAM33,” “ADAM33 gene and asthma,” and “ADAM33 gene polymorphisms” were used as search criteria. Based on available literature we can only speculate its role in the morphogenesis and functions of the lung. Fourteen studies conducted in different populations were found showing an association of ADAM33 gene polymorphisms with asthma. However, none of the single nucleotide polymorphisms (SNPs) of ADAM33 gene had found association with asthma across all ethnic groups. Because higher expression of ADAM33 is found in the fibroblast and smooth muscle cells of the lung, over- or underexpression of ADAM33 gene may result in alterations in airway remodeling and repair processes. However, no SNP of ADAM33 gene showed significant associations with asthma across all ethnic groups; the causative polymorphism, if any, still has to be identified.

Genome-wide host responses against infectious laryngotracheitis virus vaccine infection in chicken embryo lung cells

Background

Infectious laryngotracheitis virus (ILTV; gallid herpesvirus 1) infection causes high mortality and huge economic losses in the poultry industry. To protect chickens against ILTV infection, chicken-embryo origin (CEO) and tissue-culture origin (TCO) vaccines have been used. However, the transmission of vaccine ILTV from vaccinated- to unvaccinated chickens can cause severe respiratory disease. Previously, host cell responses against virulent ILTV infections were determined by microarray analysis. In this study, a microarray analysis was performed to understand host-vaccine ILTV interactions at the host gene transcription level.

Results

The 44 K chicken oligo microarrays were used, and the results were compared to those found in virulent ILTV infection. Total RNAs extracted from vaccine ILTV infected chicken embryo lung cells at 1, 2, 3 and 4 days post infection (dpi), compared to 0 dpi, were subjected to microarray assay using the two color hybridization method. Data analysis using JMP Genomics 5.0 and the Ingenuity Pathway Analysis (IPA) program showed that 213 differentially expressed genes could be grouped into a number of functional categories including tissue development, cellular growth and proliferation, cellular movement, and inflammatory responses. Moreover, 10 possible gene networks were created by the IPA program to show intermolecular connections. Interestingly, of 213 differentially expressed genes, BMP2, C8orf79, F10, and NPY were expressed distinctly in vaccine ILTV infection when compared to virulent ILTV infection.

Conclusions

Comprehensive knowledge of gene expression and biological functionalities of host factors during vaccine ILTV infection can provide insight into host cellular defense mechanisms compared to those of virulent ILTV.

The role of ADAM-mediated shedding in vascular biology

Within the vasculature the disintegrins and metalloproteinases (ADAMs) 8, 9, 10, 12, 15, 17, 19, 28 and 33 are expressed on endothelial cells, smooth muscle cells and on leukocytes. As surface-expressed proteases they mediate cleavage of vascular surface molecules at an extracellular site close to the membrane. This process is termed shedding and leads to the release of a soluble substrate ectodomain thereby critically modulating the biological function of the substrate. In the vasculature several surface molecules undergo ADAM-mediated shedding including tumour necrosis factor (TNF) α, interleukin (IL) 6 receptor α, L-selectin, vascular endothelial (VE)-cadherin, the transmembrane CX3C-chemokine ligand (CX3CL) 1, Notch, transforming growth factor (TGF) and heparin-binding epidermal growth factor (HB-EGF). These substrates play distinct roles in vascular biology by promoting inflammation, permeability changes, leukocyte recruitment, resolution of inflammation, regeneration and/or neovascularisation. Especially ADAM17 and ADAM10 are capable of cleaving many substrates with diverse function within the vasculature, whereas other ADAMs have a more restricted substrate range. Therefore, targeting ADAM17 or ADAM10 by pharmacologic inhibition or gene knockout not only attenuates the inflammatory response in animal models but also affects tissue regeneration and neovascularisation. Recent discoveries indicate that other ADAMs (e.g. ADAM8 and 9) also play important roles in vascular biology but appear to have more selective effects on vascular responses (e.g. on neovascularisation only). Although, targeting of ADAM17 and ADAM10 in inflammatory diseases is still a promising approach, temporal and spatial as well as substrate-specific inhibition approaches are required to minimise undesired side effects on vascular cells.

Epidermal growth factor (EGF) ligand release by substrate-specific a disintegrin and metalloproteases (ADAMs) involves different protein kinase C (PKC) isoenzymes depending on the stimulus

The dysregulation of EGF family ligand cleavage has severe consequences for the developing as well as the adult organism. Therefore, their production is highly regulated. The limiting step is the ectodomain cleavage of membrane-bound precursors by one of several a disintegrin and metalloprotease (ADAM) metalloproteases, and understanding the regulation of cleavage is an important goal of current research. We have previously reported that in mouse lung epithelial cells, the pro-EGF ligands TGFα, neuregulin 1β (NRG), and heparin-binding EGF are differentially cleaved depending on the cleavage stimulus (Herrlich, A., Klinman, E., Fu, J., Sadegh, C., and Lodish, H. (2008) FASEB J.). In this study in mouse embryonic fibroblasts that lack different ADAMs, we show that induced cleavage of EGF ligands can involve the same substrate-specific metalloprotease but does require different stimulus-dependent signaling pathways. Cleavage was stimulated by phorbol ester (12-O-tetradecanoylphorbol-13-acetate (TPA), a mimic of diacylglycerol and PKC activator), hypertonic stress, lysophosphatidic acid (LPA)-induced G protein-coupled receptor activation, or by ionomycin-induced intracellular calcium release. Although ADAMs showed substrate preference (ADAM17, TGFα and heparin-binding EGF; and ADAM9, NRG), substrate cleavage differed substantially with the stimulus, and cleavage of the same substrate depended on the presence of different, sometimes multiple, PKC isoforms. For instance, classical PKC was required for TPA-induced but not hypertonic stress-induced cleavage of all EGF family ligands. Inhibition of PKCζ enhanced NRG release upon TPA stimulation, but it blocked NRG release in response to hypertonic stress. Our results suggest a model in which substantial regulation of ectodomain cleavage occurs not only on the metalloprotease level but also on the level of the substrate or of a third protein.

Soluble adhesion molecules in human cancers: sources and fates

Adhesion molecules endow tumor cells with the necessary cell-cell contacts and cell-matrix interactions. As such, adhesion molecules are involved in cell signalling, proliferation and tumor growth. Rearrangements in the adhesion repertoire allow tumor cells to migrate, invade and form metastases. Besides these membrane-bound adhesion molecules several soluble adhesion molecules are detected in the supernatant of tumor cell lines and patient body fluids. Truncated soluble adhesion molecules can be generated by several conventional mechanisms, including alternative splicing of mRNA transcripts, chromosomal translocation, and extracellular proteolytic ectodomain shedding. Secretion of vesicles (ectosomes and exosomes) is an alternative mechanism mediating the release of full-length adhesion molecules. Soluble adhesion molecules function as modulators of cell adhesion, induce proteolytic activity and facilitate cell signalling. Additionally, adhesion molecules present on secreted vesicles might be involved in the vesicle-target cell interaction. Based on currently available data, released soluble adhesion molecules contribute to cancer progression and therefore should not be regarded as unrelated and non-functional side products of tumor progression.

Role of ADAM and ADAMTS metalloproteinases in airway diseases

Lungs are exposed to the outside environment and therefore to toxic and infectious agents or allergens. This may lead to permanent activation of innate immune response elements. A Disintegrin And Metalloproteinases (ADAMs) and ADAMs with Thrombospondin motifs (ADAMTS) are proteinases closely related to Matrix Metalloproteinases (MMPs). These multifaceted molecules bear metalloproteinase and disintegrin domains endowing them with features of both proteinases and adhesion molecules. Proteinases of the ADAM family are associated to various physiological and pathological processes and display a wide spectrum of biological effects encompassing cell fusion, cell adhesion, "shedding process", cleavage of various substrates from the extracellular matrix, growth factors or cytokines... This review will focus on the putative roles of ADAM/ADAMTS proteinases in airway diseases such as asthma and COPD.

Autoactivation of human ADAM8: a novel pre-processing step is required for catalytic activity

Members of the ADAM (a disintegrin and metalloproteinase) family of proteins possess a multidomain architecture which permits functionalities as adhesion molecules, signalling intermediates and proteolytic enzymes. ADAM8 is found on immune cells and is induced by multiple pro-inflammatory stimuli suggesting a role in inflammation. Here we describe an activation mechanism for recombinant human ADAM8 that is independent from classical PC (pro-protein convertase)-mediated activation. N-terminal sequencing revealed that, unlike other ADAMs, ADAM8 undergoes pre-processing at Glu(158), which fractures the Pro (pro-segment)-domain before terminal activation takes place to remove the putative cysteine switch (Cys(167)). ADAM8 lacking the DIS (disintegrin) and/or CR (cysteine-rich) and EGF (epidermal growth factor) domains displayed impaired ability to complete this event. Thus pre-processing of the Pro-domain is co-ordinated by DIS and CR/EGF domains. Furthermore, by placing an EK (enterokinase) recognition motif between the Pro- and catalytic domains of multiple constructs, we were able to artificially remove the pro-segment prior to pre-processing. In the absence of pre-processing of the Pro-domain a marked decrease in specific activity was observed with the autoactivated enzyme, suggesting that the Pro-domain continued to associate and inhibit active enzyme. Thus, pre-processing of the Pro-domain of human ADAM8 is important for enzyme maturation by preventing re-association of the pro-segment with the catalytic domain. Given the observed necessity of DIS and CR/EGF for pre-processing, we conclude that these domains are crucial for the proper activation and maturation of human ADAM8.

ADAM8 substrate specificity: influence of pH on pre-processing and proteoglycan degradation

A disintegrin and metalloprotease-8 (ADAM8) is thought to play a role in cancer and inflammatory diseases such as allergy, arthritis, and asthma. Despite the implication of ADAM8 in these diseases, the functional role of ADAM8 catalytic activity remains unclear. In this report, we demonstrate that an early critical autolytic event, we have termed pre-processing, is accelerated at acidic pH (pH 5.5) while autolytic activation is abrogated under the same conditions. Likewise, we found that pre-processing is hindered and autolytic activation is facilitated in neutral pH conditions, and thus demonstrates a pH-dependent shift in substrate selectivity. This finding is further supported by two peptide substrates corresponding to the pre-processing and C-terminal scissile bonds that were preferentially cleaved at acidic and neutral pH, respectively. Lastly, we found fibronectin cleavage to be attenuated at pH 5.5, while two novel substrates, brevican, and vitronectin, were readily cleaved in neutral or acidic conditions.

Stall encodes an ADAMTS metalloprotease and interacts genetically with Delta in Drosophila ovarian follicle formation

Ovarian follicle formation in Drosophila melanogaster requires stall (stl) gene function, both within and outside the ovary, for follicle individualization, stalk cell intercalation, and oocyte localization. We have identified the stl transcript as CG3622 and confirmed the presence of three alternatively spliced isoforms, contrary to current genome annotation. Here we show that the gene is expressed in both ovarian and brain tissues, which is consistent with previous evidence of an ovary nonautonomous function. On the basis of amino acid sequence, stl encodes a metalloprotease similar to the "a disintegrin and metalloprotease with thrombospondin" (ADAMTS) family. Although stl mutant ovaries fail to maintain the branched structure of the fusome and periodically show improperly localized oocytes, stl mutants do not alter oocyte determination. Within the ovary, stl is expressed in pupal basal stalks and in adult somatic cells of the posterior germarium and the follicular poles. Genetically, stl exhibits a strong mutant interaction with Delta (Dl), and Dl mutant ovaries show altered stl expression patterns. Additionally, a previously described genetic interactor, daughterless, also modulates stl expression in the somatic ovary and may do so directly in its capacity as a basic helix-loop-helix (bHLH) transcription factor. We propose a complex model of long-range extraovarian signaling through secretion or extracellular domain shedding, together with local intraovarian protein modification, to explain the dual sites of Stl metalloprotease function in oogenesis.

Influence of ADAM28 on biological characteristics of human dental follicle cells

OBJECTIVES

The aim of this study was to investigate the effects of a disintegrin and metalloproteinase 28 (ADAM28) on the biological characteristics of human dental follicle cells (HDFCs) and possible action mechanism.

METHODS

Eukaryotic expression plasmid containing ADAM28 coding region and ADAM28 antisense oligodeoxynucleotides (AS-ODN) with FITC labelling were constructed and synthesised by gene clone and recombination. Then we respectively transfected them into HDFCs by Lipofectamine 2000 system and detected their effects on proliferation, differentiation and apoptosis of HDFCs by MTT assay, cell cycle detection, ALP activity and Annexin V-FITC/PI analysis. Finally we observed the effects of ADAM28 AS-ODN on HDFCs expressing extracellular matrix (ECM) proteins by immunocytochemical staining.

RESULTS

ADAM28 eukaryotic plasmid was constructed and identified successfully, and could be correctly translated and expressed in HDFCs, furthermore overexpression of ADAM28 promoted the HDFCs proliferation and inhibited specific differentiation of HDFCs, while inhibition of ADAM28 exerted the opposite effects and induced apoptosis. Moreover ADAM28 could significantly inhibit the secretion of OPN and type III collagen of HDFCs.

CONCLUSIONS

ADAM28 might actively participate in the network regulation which associates HDFCs proliferation, differentiation, apoptosis with matrix mineralisation during tooth development by interacting with multiple signal molecules.

Characterization of the catalytic activity of the membrane-anchored metalloproteinase ADAM15 in cell-based assays

ADAM15 (a disintegrin and metalloproteinase 15) is a membrane-anchored metalloproteinase, which is overexpressed in several human cancers and has been implicated in pathological neovascularization and prostate cancer metastasis. Yet, little is known about the catalytic properties of ADAM15. Here, we purified soluble recombinant ADAM15 to test for its ability to cleave a library of peptide substrates. However, we found no processing of any of the peptide substrates tested here, and therefore turned to cell-based assays to characterize the catalytic properties of ADAM15. Overexpression of full-length membrane-anchored ADAM15 or the catalytically inactive ADAM15E-->A together with various membrane proteins resulted in increased release of the extracellular domain of the fibroblast growth factor receptor 2iiib (FGFR2iiib) by ADAM15, but not ADAM15E-->A. This provided a robust assay for a characterization of the catalytic properties of ADAM15 in intact cells. We found that increased expression of ADAM15 resulted in increased FGFR2iiib shedding, but that ADAM15 was not stimulated by phorbol esters or calcium ionophores, two commonly used activators of ectodomain shedding. Moreover, ADAM15-dependent processing of FGFR2iiib was inhibited by the hydroxamate-based metalloproteinase inhibitors marimastat, TAPI-2 and GM6001, and by 50 nM TIMP-3 (tissue inhibitor of metalloproteinases 3), but not by 100 nM TIMP-1, and only weakly by 100 nM TIMP-2. These results define key catalytic properties of ADAM15 in cells and its response to stimulators and inhibitors of ectodomain shedding. A cell-based assay for the catalytic activity of ADAM15 could aid in identifying compounds, which could be used to block the function of ADAM15 in pathological neovascularization and cancer.

Identification of key sequence determinants for the inhibitory function of the prodomain of TACE

The TNFalpha converting enzyme (TACE) is a zinc metalloproteinase that mediates shedding of multiple cell surface proteins. Regulation of TACE enzymatic activity is ultimately mediated via proteolytic removal of its inhibitory prodomain. Sequence determinants for TACE prodomain inhibition of the catalytic domain are yet to be identified. Surprisingly, although TACE and ADAM 10 (closest homologue) share only 23% sequence identity at their prodomains, the latter in isolation inhibits TACE with the same potency as TACE own prodomain. In contrast, the prodomain of ADAM 9 inhibited TACE only weakly. Detailed analysis of ADAM prodomains revealed two short regions for which TACE and ADAM 10 depart dramatically from all other family members. We prepared TACE prodomain variants containing full or partial switches to ADAM 9 residues at those two regions and examined their functional properties. Variants containing ADAM 9 substitutions including amino acid residues 72-82 and 126-137 were fully inactive for TACE inhibition. A third variant comprising residues 114-125 was active but at lower potency relative to wild type. All inactive variants appeared to be correctly folded. Finally, the amino acid residue Phe72 and the motif Asp-Asp-Val-Ile137 were identified within those regions as key determinants for TACE prodomain inhibitory function. We conclude that TACE and ADAM 10 prodomains are functionally equivalent in a way that separates them from the rest of the ADAM family.

Essential role of ADAM28 in regulating the proliferation and differentiation of human dental papilla mesenchymal cells (hDPMCs)

Dental papilla mesenchymal cells (DPMCs) have been supposed to possess the relatively independent and critical role for tooth development and morphogenesis. Here, we characterized the role of ADAM28, a member of a disintegrin and metalloproteinase (ADAM) family, in the regulative mechanisms of odontogenic capability of hDPMCs. Immunofluorescence staining showed the ubiquitous expression of ADAM28 in multiple human dental mesenchymal and epithelial cells. After confirming the effect of eukaryotic expression plasmid containing ADAM28 coding region and ADAM28 antisense oligodeoxynucleotide (AS-ODN), we respectively transfected them into hDPMCs and observed the biological markers for proliferation and differentiation. Overexpression of ADAM28 favored the proliferation and lineage-specific differentiation of hDPMCs, while blockage of ADAM28 exerted the opposite effects and induced apoptosis. These results identified an unrecognized hypothesis that ADAM28 may function as positive regulator of growth and differentiation of hDPMCs and act as an important molecule mediating reciprocal epithelial-mesenchymal signaling during tooth organ development.

Application of structural dynamic approaches provide novel insights into the enzymatic mechanism of the tumor necrosis factor-alpha-converting enzyme

Zinc dependent metalloproteinases comprise a large family of structurally homologous enzymes with a wide variety of biological roles. Originally described as proteinases involved in extracellular matrix (ECM) catabolism, these enzymes were later found to serve major roles as initiators of signaling pathways in many aspects of biology, ranging from cell proliferation, differentiation and communication, to pathological states associated with tumor metastasis, inflammation, tissue degeneration and cell death. From these enzymes, the tumor necrosis factor-α converting enzyme (TACE) stands out as a central shedding activity mediating the regulated release of a host of cytokines, receptors and other cell surface molecules. Selective drugs targeted at blocking TACE for treatment of rheumatoid arthritis and other disease indications are highly sought. Yet, the structural and chemical knowledge underlying its enzymatic activity is very limited. This is in part due to the fact that the catalytic zinc atom of metalloproteinases is usually spectroscopically silent and hence difficult to study using conventional spectroscopic and analytical tools. Most structural and biochemical studies, as well as medicinal chemistry efforts carried out so far were limited to non-dynamic structure/function characterization. Thus, to date, our mechanistic knowledge comes from theoretical calculations derived from static crystal structures from family members that are highly similar in their amino acid sequence and three-dimensional structure.

This review introduces the importance of real-time quantification of biophysical properties and structural kinetic behavior applied to the study of TACE and other zinc metalloproteinases to dissect their molecular mechanisms. The molecular details that link the catalytic chemistry to key kinetic, electronic and structural events have remained elusive because of the difficulties associated with probing time-dependent structure-function aspects of enzymatic reactions. Here we discuss the use of conventional and real-time structural-spectroscopic tools to study the reactive metal site during catalysis, and initial lessons on the enzymatic mechanism that we are learning. Approaches such as the ones presented here may be useful in the design of specific inhibitors as drug candidates.

Novel conserved hydrolase domain in the CLCA family of alleged calcium-activated chloride channels

Advanced protein structure prediction methods combined with structure modeling show that the mammalian proteins, described until now as calcium-activated chloride channels (CLCAs), appear in fact to be membrane anchored metal-dependent hydrolases, possibly proteases. A metallohydrolase structural domain was predicted, unexpectedly, in the CLCA sequences. The well-conserved active site in the modeled structure of this hydrolase domain allows the prediction of catalytic action similar to that of metalloproteases. A number of protein structure prediction methods suggest the overall fold of the N-terminal hydrolase domain to be most similar to that of zinc metalloproteases (zincins), notably matrixins. This is confirmed by analysis of the three-dimensional structure model of the predicted CLCA1 hydrolase domain built using the known structure of the MMP-11 catalytic domain. Fragments of CLCA1 corresponding to the modeled hydrolase domain were expressed in Escherichia coli, and the resulting proteins were readily refolded into monomeric soluble protein, indicating formation of stable independent domains. The homology model was used to predict putative substrate sequences. Homologs of mammalian CLCA genes were detected in the genomes of a vast array of multicellular animals: lower vertebrates, tunicates, insects, crustaceans, echinoderms, and flatworms. The hydrolase prediction is discussed in the context of published experimentally determined effects of CLCA proteins on chloride conductance. Altered proteolytic processing of full-length CLCA1 containing a mutation abolishing the predicted hydrolase activity is shown as initial experimental evidence for a role of the hydrolase domain in processing of mature full-length CLCA1. The hydrolase prediction together with the presented experimental data add to doubts about the function of CLCAs as chloride channels and strengthen the hypothesis of channel-activating and/or channel-accessory roles.

Differential Endocrine Regulation of Genes Enriched in Initial Segment and Distal Caput of the Mouse Epididymis as Revealed by Genome-Wide Expression Profiling1

We have performed genome-wide expression profiling of endocrine regulation of genes expressed in the mouse initial segment (IS) and distal caput of the epididymis by using Affymetrix microarrays. The data revealed that of the 15 020 genes expressed in the epididymis, 35% were enriched in one of the two regions studied, indicating that differential functions can be attributed to the IS and the more distal caput regions. The data, furthermore, showed that 27% of the genes expressed in the IS and/or distal caput epididymidis are under the regulation of testicular factors present in the duct fluid, while bloodborne androgens can regulate for 14% of them. This is in line with the high testis dependency of epididymal physiology. We then focused on genes with moderate or strong expression, showing strict segment enrichment and strong dependency on testicular factors. Analyses of the 59 genes, including upregulated and downregulated genes, fulfilling the criteria indicated that the expression of 18 (17 downregulated genes; 1 upregulated gene) of 19 gonadectomy-responsive genes enriched in the IS was not maintained by the androgen treatment, whereas the expression of all six downregulated genes enriched in the distal caput and the majority of those with no strict segment enrichment of expression (28 of 34; consisting of 23 downregulated and 5 upregulated genes) were maintained by androgens. Hence, it is evident that testicular factors other than androgens are important for the expression of IS-enriched genes, whereas the expression of distal caput-enriched genes is typically regulated by androgens. Identical data were obtained by independent clustering analyses performed for the expression data of 3626 epididymal genes. Several novel genes with putative involvement in epididymal sperm maturation, such as a disintegrin and metallopeptidase domain 28 (Adam28) and a solute carrier organic anion transporter family, member 4C1 (Slco4c1), were identified, indicating that this approach is successful for identifying novel epididymal genes.

ADAM28 participates in the regulation of tooth development

Disintegrin and metalloprotease (ADAM) proteins are a family of membrane-anchored glycoproteins with diverse functions in fertilisation, development, neurogenesis and protein ectodomain shedding. ADAM28 is a newly discovered member of the ADAM family in humans and murine with autocatalytic activity. Recently, the authors screened ADAM28 genes from patients with congenital hypoplasia of tooth root, and studied the relationship between ADAM28 and tooth development. A polyclonal antibody (pAb) against ADAM28 was preparared, and the expression and localisation of ADAM28 were detected in tooth germ and dental mesenchymal cells. The results indicated that the prokaryotic expression vector pGEX-4T-ADAM28 was constructed successfully. Glutathione S-transferase-ADAM28 fusion protein was generated after inducement by isopropylthio-beta-d-galactoside and isolated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The purified fusion protein was used as an antigen for production of antibody. Western blot and enzyme-linked immunosorbent assay analyses verified that the antibody had a high specificity and titre. Immunohistochemistry and reverse transcriptase-polymerase chain reaction showed that ADAM28 was expressed at each stage of tooth germ development at different levels. Moreover, it was expressed in human dental follicle cells, human dental papilla cells, human dental pulp stem cells, human periodontal ligament cells and human dental cervical loop epithelial cells at transcription level. In conclusion, it is reasonable to suggest that ADAM28 may participate in tooth development and the regulation of odontogenic mesenchymal cells through progressive reciprocal inductive interactions between the epithelium and the mesenchyme.

ADAM33 haplotypes are associated with asthma in a large Australian population

The ADAM33 gene has recently been identified as being a potentially important asthma candidate gene, and polymorphisms in this gene have been shown to be associated with asthma and bronchial hyperresponsiveness in Caucasian individuals from several populations. We performed chip-based matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry using the MassARRAY system and multiplexed genotyping assays to investigate the association between 10 single nucleotide polymorphisms (SNPs) in the ADAM33 gene (F_+1, Q_-1, S_1, ST_+4, ST_+7, V_-2, V_-1, V_2, V_4, V_5) and asthma and asthma severity in a large Australian Caucasian population of nonasthmatic controls (n = 473), and patients with mild (n = 292), moderate (n = 238) and severe (n = 82) asthma. No significant association was found between any one of the 10 SNPs and asthma or asthma severity, however, there was a significant global haplotypic association with asthma (P = 0.0002) and disease severity (P = 0.0001), driven by the combination of two key SNPs, V_-1 and ST_+7. A meta-analysis of all the genetic studies conducted to date found significant between-study heterogeneity, likely to reflect population stratification. Our analysis of ADAM33 haplotypes further suggests a likely role for ADAM33 in the asthma phenotype, although it does not exclude an association with another locus in linkage disequilibrium with ADAM33.