Genomic and phylogenetic analysis of choriolysins, and biological activity of hatching liquid in the flatfish Senegalese sole

The hatching enzymes or choriolysins are key proteases in fish life cycle controlling the release of larvae to surrounding environment that have been suggested as target for novel biotechnological uses. Due to the large amounts of eggs released by the flatfish Solea senegalensis, during the spawning season, the hatching liquid properties and choriolysin-encoding genes were investigated in this species. A genomic analysis identified four putative genes referred to as SseHCEa, SseHCEb, SseLCE and SseHE. The phylogenetic analysis classified these paralogs into two clades, the clade I containing SseHCE paralogs and the clade II containing two well-supported subclades named as HE and LCE. The two SseHCE paralogs were intron-less and both genes were tandemly arrayed very close in the genome. The synteny and gene rearrangement identified in the flatfish lineage indicated that the duplication of these two paralogs occurred recently and they are under divergent evolution. The genes SseHE and SseLCE were structured in 8 exons and 7 introns and the synteny was conserved in teleosts. Expression studies confirmed that the four genes were expressed in the hatching gland cells and they migrate co-ordinately from the head to around the yolk sac close to the hatch with specific temporal and intensity expression profiles. Although the mRNA levels of the four genes peaked in the hours previous to larval hatching, the SseHCE and SseLCE paralogs kept a longer expression than SseHE after hatching. These expression patterns were consistent even when larvae were incubated at different temperatures that modified hatching times. The analysis of hatching-liquid using SDS-PAGE and zymography analyses of hatching liquid identified a major band of expected choriolysin size. The optimal pH for protease activity was 8.5 and inhibition assays using EDTA demonstrated that most of the activity in the hatching liquid was due to metalloproteases with Ca²⁺ ions acting as the most effective metal to restore the activity. All these data provide new clues about the choriolysin evolution and function in flatfish with impact in the aquaculture and the blue cosmetic industry.

Trypanosomal mitochondrial intermediate peptidase does not behave as a classical mitochondrial processing peptidase

Upon their translocation into the mitochondrial matrix, the N-terminal pre-sequence of nuclear-encoded proteins undergoes cleavage by mitochondrial processing peptidases. Some proteins require more than a single processing step, which involves several peptidases. Down-regulation of the putative Trypanosoma brucei mitochondrial intermediate peptidase (MIP) homolog by RNAi renders the cells unable to grow after 48 hours of induction. Ablation of MIP results in the accumulation of the precursor of the trypanosomatid-specific trCOIV protein, the largest nuclear-encoded subunit of the cytochrome c oxidase complex in this flagellate. However, the trCOIV precursor of the same size accumulates also in trypanosomes in which either alpha or beta subunits of the mitochondrial processing peptidase (MPP) have been depleted. Using a chimeric protein that consists of the N-terminal sequence of a putative subunit of respiratory complex I fused to a yellow fluorescent protein, we assessed the accumulation of the precursor protein in trypanosomes, in which RNAi was induced against the alpha or beta subunits of MPP or MIP. The observed accumulation of precursors indicates MIP depletion affects the activity of the cannonical MPP, or at least one of its subunits.

P-III hemorrhagic metalloproteinases from Russell's viper venom: cloning, characterization, phylogenetic and functional site analyses

Two homologous P-III hemorrhagic metalloproteinases were purified from Russell's viper venoms from Myanmar and Kolkata (eastern India), and designated as daborhagin-M and daborhagin-K, respectively. They induced severe dermal hemorrhage in mice at a minimum hemorrhagic dose of 0.8-0.9 microg. Daborhagin-M specifically hydrolyzed an Aalpha-chain of fibrinogen, fibronectin, and type IV collagen in vitro. Analyses of its cleavage sites on insulin chain B and kinetic specificities toward oligopeptides suggested that daborhagin-M prefers hydrophobic residues at the P(1), P(1)', and P(2)' positions on the substrates. Of the eight Daboia geographic venom samples analyzed by Western blotting, only those from Myanmar and eastern India showed a strong positive band at 65kDa, which correlated with the high risk of systemic hemorrhagic symptoms elicited by Daboia envenoming in both regions. The full sequence of daborhagin-K was determined by cDNA cloning and sequencing, and then confirmed by peptide mass fingerprinting. Furthermore, molecular phylogenetic analyses based on 27 P-IIIs revealed the co-evolution of two major P-III classes with distinct hemorrhagic potencies, and daborhagin-K belongs to the most hemorrhagic subclass. By comparing the absolute complexity profiles between these two classes, we identified four structural motifs probably responsible for the phylogenetic subtyping and hemorrhagic potencies of P-III SVMPs.

Meprins, membrane-bound and secreted astacin metalloproteinases

The astacins are a subfamily of the metzincin superfamily of metalloproteinases. The first to be characterized was the crayfish enzyme astacin. To date more than 200 members of this family have been identified in species ranging from bacteria to humans. Astacins are involved in developmental morphogenesis, matrix assembly, tissue differentiation and digestion. Family members include the procollagen C-proteinase (BMP1, bone morphogenetic protein 1), tolloid and mammalian tolloid-like, HMP (Hydra vulgaris metalloproteinase), sea urchin BP10 (blastula protein) and SPAN (Strongylocentrotus purpuratus astacin), the 'hatching' subfamily comprising alveolin, ovastacin, LCE, HCE ('low' and 'high' choriolytic enzymes), nephrosin (from carp head kidney), UVS.2 from frog, and the meprins. In the human and mouse genomes, there are six astacin family genes (two meprins, three BMP1/tolloid-like, one ovastacin), but in Caenorhabditis elegans there are 40. Meprins are the only astacin proteinases that function on the membrane and extracellularly by virtue of the fact that they can be membrane-bound or secreted. They are unique in their domain structure and covalent subunit dimerization, oligomerization propensities, and expression patterns. They are normally highly regulated at the transcriptional and post-translational levels, localize to specific membranes or extracellular spaces, and can hydrolyse biologically active peptides, cytokines, extracellular matrix (ECM) proteins and cell-surface proteins. The in vivo substrates of meprins are unknown, but the abundant expression of these proteinases in the epithelial cells of the intestine, kidney and skin provide clues to their functions.

An archaeal orthologue of the universal protein Kae1 is an iron metalloprotein which exhibits atypical DNA-binding properties and apurinic-endonuclease activity in vitro

The Kae1 (Kinase-associated endopeptidase 1) protein is a member of the recently identified transcription complex EKC and telomeres maintenance complex KEOPS in yeast. Kae1 homologues are encoded by all sequenced genomes in the three domains of life. Although annotated as putative endopeptidases, the actual functions of these universal proteins are unknown. Here we show that the purified Kae1 protein (Pa-Kae1) from Pyrococcus abyssi is an iron-protein with a novel type of ATP-binding site. Surprisingly, this protein did not exhibit endopeptidase activity in vitro but binds cooperatively to single and double-stranded DNA and induces unusual DNA conformational change. Furthermore, Pa-Kae1 exhibits a class I apurinic (AP)-endonuclease activity (AP-lyase). Both DNA binding and AP-endonuclease activity are inhibited by ATP. Kae1 is thus a novel and atypical universal DNA interacting protein whose importance could rival those of RecA (RadA/Rad51) in the maintenance of genome integrity in all living cells.

Molecular characterization and phylogenetic analysis of BjussuMP-I: A RGD-P-III class hemorrhagic metalloprotease from Bothrops jararacussu snake venom

Snake venom metalloproteases (SVMPs) embody zinc-dependent multidomain enzymes responsible for a relevant pathophysiology in envenomation, including local and systemic hemorrhage. The molecular features responsible for hemorrhagic potency of SVMPs have been associated with their multidomains structures which can target these proteins them to several receptors of different tissues and cellular types. BjussuMP-I, a SVMP isolated from the Bothrops jararacussu venom, has been characterized as a P-III hemorrhagic metalloprotease. The complete cDNA sequence of BjussuMP-I with 1641bp encodes open reading frames of 547 amino acid residues, which conserve the common domains of P-III high molecular weight hemorrhagic metalloproteases: (i) pre-pro-peptide, (ii) metalloprotease, (iii) disintegrin-like and (iv) rich cysteine domain. BjussuMP-I induced lyses in fibrin clots and inhibited collagen- and ADP-induced platelet aggregation. We are reporting, for the first time, the primary structure of an RGD-P-III class snake venom metalloprotease. A phylogenetic analysis of the BjussuMP-I metalloprotease/catalytic domain was performed to get new insights into the molecular evolution of the metalloproteases. A theoretical molecular model of this domain was built through folding recognition (threading) techniques and refined by molecular dynamics simulation. Then, the final BjussuMP-I catalytic domain model was compared to other SVMPs and Reprolysin family proteins in order to identify eventual structural differences, which could help to understand the biochemical activities of these enzymes. The presence of large hydrophobic areas and some conserved surface charge-positive residues were identified as important features of the SVMPs and other metalloproteases.

A common genetic system for functional studies of pitrilysin and related M16A proteases

Pitrilysin is a bacterial protease that is similar to the mammalian insulin-degrading enzyme, which is hypothesized to protect against the onset of Alzheimer's disease, and the yeast enzymes Axl1p and Ste23p, which are responsible for production of the a-factor mating pheromone in Saccharomyces cerevisiae. The lack of a phenotype associated with pitrilysin deficiency has hindered studies of this enzyme. Herein, we report that pitrilysin can be heterologously expressed in yeast such that it functionally substitutes for the shared roles of Axl1p and Ste23p in pheromone production, resulting in a readily observable phenotype. We have exploited this phenotype to conduct structure-function analyses of pitrilysin and report that residues within four sequence motifs that are highly conserved among M16A enzymes are essential for its activity. These motifs include the extended metalloprotease motif, a second motif that has been hypothesized to be important for the function of M16A enzymes, and two others not previously recognized as being important for pitrilysin function. We have also established that the two self-folding domains of pitrilysin are both required for its proteolytic activity. However, pitrilysin does not possess all the enzymatic properties of the yeast enzymes since it cannot substitute for the role of Axl1p in the repression of haploid invasive growth. These observations further support the utility of the yeast system for structure-function and comparative studies of M16A enzymes.

The distribution of the bft alleles among enterotoxigenic Bacteroides fragilis strains from stool specimens and extraintestinal sites

Enterotoxigenic Bacteroides fragilis (ETBF) has been implicated in diarrhoeal illness in animals and humans. Recent data suggest that ETBF is associated with flares of inflammatory bowel disease. Toxigenicity is attributed to expression of a toxin referred to as fragilysin, which stimulates fluid accumulation in ligated intestinal segments and alter the morphology of human intestinal cells. Three different isoforms or variants of the enterotoxin gene, designated bft-1, bft-2, and bft-3, have been identified. In this study we investigated the distribution of bft alleles among ETBF strains in stool specimens from patients with colon cancer (n: 31), the control patients (n: 8) and extraintestinal sources (n: 15). We used restriction fragment length polymorphism analysis of the PCR-amplified enterotoxin gene and sequencing the PCR-product to detect the isoforms of bft gene. Among the stool strains, bft-1 was found to be more common than bft-2; as it was detected 27 of 31 strains from colon cancer patients and 7 of 8 control strains. The bft-1 isoform was also found in almost all isolates from extraintestinal sites. No bft-3 subtype was detected among all tested strains.

The ADAMTS metalloproteinases

The ADAMTSs (a disintegrin and metalloproteinase with thrombospondin motifs) are a group of proteases that are found both in mammals and invertebrates. Since the prototype ADAMTS-1 was first described in 1997, there has been a rapidly expanding body of literature describing this gene family and the proteins they encode. The complete human family has 19 ADAMTS genes, together with three members of a newly identified subgroup, the ADAMTSL (ADAMTS-like) proteins, which have several domains in common with the ADAMTSs. The ADAMTSs are extracellular, multidomain enzymes whose known functions include: (i) collagen processing as procollagen N-proteinase; (ii) cleavage of the matrix proteoglycans aggrecan, versican and brevican; (iii) inhibition of angiogenesis; and (iv) blood coagulation homoeostasis as the von Willebrand factor cleaving protease. Roles in organogenesis, inflammation and fertility are also apparent. Recently, some ADAMTS genes have been found to show altered expression in arthritis and various cancers. This review highlights progress in understanding the structural organization and functional roles of the ADAMTSs in normal and pathological conditions.

Nardilysin, a basic residues specific metallopeptidase that mediates cell migration and proliferation

Nardilysin (NRDc), a metallopeptidase of the M16 family, presents, in vitro, cleavage specificity for basic residues. Depending on the cell type, it is cytoplasmic, exported or cell surface associated. As a new receptor for heparin-binding EGF-like growth factor (HB-EGF), NRDc was recently shown to be involved in cellular migration and proliferation. Since for those processes its enzymatic activity is not required, it is now evident that nardilysin fulfills at least two distinct functions, i.e. an HB-EGF modulator and a peptidase.

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.

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

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

Hemodynamic Regulation of Metallopeptidases within the Vasculature

Hemodynamic forces associated with blood flow play a vital role in the endothelial regulation of vascular tone, remodeling and the initiation and progression of vascular diseases such as atherosclerosis and hypertension. Crucial elements in endothelium-mediated events within the blood vessel are bioactive peptide signals and their associated hydrolytic enzymes. This review examines the relationship between hemodynamic forces such as shear stress and cyclic strain, and an important group of peptide-degrading enzymes within the endothelium, the thermolysin-like zinc metallopeptidases.

ADAMs family members as amyloid precursor protein alpha-secretases

In the non-amyloidogenic pathway, the Alzheimer's amyloid precursor protein (APP) is cleaved within the amyloid-beta domain by alpha-secretase precluding deposition of intact amyloid-beta peptide. The large ectodomain released from the cell surface by the action of alpha-secretase has several neuroprotective properties. Studies with protease inhibitors have shown that alpha-secretase is a zinc metalloproteinase, and several members of the adamalysin family of proteins, tumour necrosis factor-alpha convertase (TACE, ADAM17), ADAM10, and ADAM9, all fulfil some of the criteria required of alpha-secretase. We review the evidence for each of these ADAMs acting as the alpha-secretase. What seems to be emerging from numerous studies, including those with mice in which each of the ADAMs has been knocked out, is that there is a team of zinc metalloproteinases able to cleave APP at the alpha-secretase site. We also discuss how upregulation of alpha-secretase activity by muscarinic agonists, cholesterol-lowering drugs, steroid hormones, non-steroidal anti-inflammatory drugs, and metal ions may explain some of the therapeutic actions of these agents in Alzheimer's disease.

A defect in a novel ADAMTS family member is the cause of the belted white-spotting mutation

Several features of the pigment defect in belted (bt) mutant mice suggest that it occurs as a result of a defect in melanocyte development that is unique from those described for other classical white-spotting mutations. We report here that bt mice carry mutations in Adamts20, a novel member of the ADAMTS family of secreted metalloproteases. Adamts20 shows a highly dynamic pattern of expression in the developing embryo that generally precedes the appearance of melanoblasts in the same region, and is not expressed in the migrating cells themselves. Adamts20 shows remarkable homology with GON-1, an ADAMTS family protease required for distal tip cell migration in C. elegans. Our results suggest that the role of ADAMTS proteases in the regulation of cell migration has been conserved in mammalian development.

Structural aspects of the metzincin clan of metalloendopeptidases

Metalloendopeptidases are present across all kingdoms of living organisms; they are ubiquitous and widely involved in metabolism regulation through their ability either to extensively degrade proteins or to selectively hydrolyze specific peptide bonds. They must be subjected to exquisite spatial and temporal control to prevent this vast potential from becoming destructive. These enzymes are mostly zinc-dependent and the majority of them, named zincins, possess a short consensus sequence, HEXXH, with the two histidines acting as ligands of the catalytic zinc and the glutamate as the general base. A subclass of the zincins is characterized by a C-terminally elongated motif, HEXXHXXGXXH/D, with an additional strictly conserved glycine and a third zinc-binding histidine or aspartate. Currently, representative three-dimensional structures of six different proteinase families bearing this motif show, despite low sequence similarity, comparable overall topology. This includes a substrate-binding crevice, which subdivides the enzyme moiety into an upper and a lower subdomain. A common five-stranded beta-sheet and two alpha-helices are always found in the upper subdomain. The second of these helices encompasses the first half of the elongated consensus sequence and is therefore termed the active-site helix. Other shared characteristics are an invariant methionine-containing Met-turn beneath the catalytic metal and a further C-terminal helix in the lower subdomain. All these structural features identify the metzincin clan of metalloendopeptidases. This clan is reviewed from a structural point of view, based on the reported structures of representative members of the astacins, adamalysins, serralysins, matrixins, snapalysins, and leishmanolysins, and of inhibited forms, either by specific endogenous protein inhibitors or by zymogenic pro-domains. Moreover, newly available genomic sequences have unveiled novel putative metzincin families and new hypothetical members of existing ones.

Structure, expression, and developmental function of early divergent forms of metalloproteinases in hydra

Metalloproteinases have a critical role in a broad spectrum of cellular processes ranging from the breakdown of extracellular matrix to the processing of signal transduction-related proteins. These hydrolytic functions underlie a variety of mechanisms related to developmental processes as well as disease states. Structural analysis of metalloproteinases from both invertebrate and vertebrate species indicates that these enzymes are highly conserved and arose early during metazoan evolution. In this regard, studies from various laboratories have reported that a number of classes of metalloproteinases are found in hydra, a member of Cnidaria, the second oldest of existing animal phyla. These studies demonstrate that the hydra genome contains at least three classes of metalloproteinases to include members of the 1) astacin class, 2) matrix metalloproteinase class, and 3) neprilysin class. Functional studies indicate that these metalloproteinases play diverse and important roles in hydra morphogenesis and cell differentiation as well as specialized functions in adult polyps. This article will review the structure, expression, and function of these metalloproteinases in hydra.

Characterization of ADAMTS-9 and ADAMTS-20 as a distinct ADAMTS subfamily related to Caenorhabditis elegans GON-1

We demonstrate that in humans, two metalloproteases, ADAMTS-9 (1935 amino acids) and ADAMTS-20 (1911 amino acids) are orthologs of GON-1, an ADAMTS protease required for gonadal morphogenesis in Caenorhabditis elegans. ADAMTS-9 and ADAMTS-20 have an identical modular structure, are distinct in possessing 15 TSRs and a unique C-terminal domain, and have a similar gene structure, suggesting that they comprise a new subfamily of human ADAMTS proteases. ADAMTS20 is very sparingly expressed, although it is detectable in epithelial cells of the breast and lung. However, ADAMTS9 is highly expressed in embryonic and adult tissues, and therefore we characterized the ADAMTS-9 protein further. Although the ADAMTS-9 zymogen has many proprotein convertase processing sites, pulse-chase analysis, site-directed mutagenesis, and amino acid sequencing demonstrated that maturation to the active form occurs by selective proprotein convertase (e.g. furin) cleavage of the Arg(287)-Phe(288) bond. Although lacking a transmembrane sequence, ADAMTS-9 is retained near the cell surface as well as in the ECM of transiently transfected COS-1 and 293 cells. COS-1 cells transfected with ADAMTS9 (but not vector-transfected cells) proteolytically cleaved bovine versican and aggrecan core proteins at the Glu(441)-Ala(442) bond of versican V1 and the Glu(1771)-Ala(1772) bond of aggrecan, respectively. In contrast, the ADAMTS-9 catalytic domain alone was neither localized to the cell surface nor able to confer these proteolytic activities on cells, demonstrating that the ancillary domains of ADAMTS-9, including the TSRs, are required both for specific extracellular localization and for its versicanase and aggrecanase activities.

Molecular cloning and expression of structural domains of bothropasin, a P-III metalloproteinase from the venom of Bothrops jararaca

Mature P-III snake metalloproteinases are soluble venom components which belong to the Reprolysin sub family and are structurally related to the mammalian membrane-bound A Disintegrin And Metalloproteinase (ADAMs). Here we present the molecular cloning of bothropasin, a metalloproteinase with hemorrhagic and myonecrotic activities isolated from the venom of Bothrops jararaca. The full-length cDNA encoding the bothropasin precursor was cloned by immunoscreening and its authenticity was confirmed by the amino acid sequence of internal fragments obtained from an autolyzed sample of native bothropasin. The predicted bothropasin precursor is comprised of the elements of a P-III venom metalloproteinase: signal sequence, pro-, metalloproteinase, disintegrin-like and cysteine-rich domains. In the autolysis process of native bothropasin, the disintegrin-like and cysteine-rich domains remained intact while the metalloproteinase domain was cleaved at different sites. The attempts made to obtain the recombinant precursor form of bothropasin using bacterial, yeast and mammalian cell expression systems failed to produce it in an amount sufficient to analyze the activation of the zymogen. Nevertheless, the study of the expression of the individual domains of bothropasin using a bacterial system resulted in the production of recombinant pro-and disintegrin-like+cysteine-rich domains but not the metalloproteinase domain. These results along with the autolysis pattern of the native protein suggest a role for the metalloproteinase domain in the structural stability of bothropasin.

Positive selection within sperm-egg adhesion domains of fertilin: an ADAM gene with a potential role in fertilization

Genes with a role in fertilization show a common pattern of rapid evolution. The role played by positive selection versus lack of selective constraints has been more difficult to establish. One problem arises from attempts to detect selection in an overall gene sequence analysis. I have analyzed the pattern of molecular evolution of fertilin, a gene coding for a heterodimeric sperm protein belonging to the ADAM (A disintegrin and A metalloprotease) gene family. A nonsynonymous to synonymous rate ratio (d(N)/d(S)) analysis for different protein domains of fertilin alpha and fertilin beta showed d(N)/d(S) < 1, suggesting that purifying selection has shaped fertilin's evolution. However, an analysis of the distribution of single positively selected codon sites using phylogentic analysis by maximum likelihood (PAML) showed sites within adhesion domains (disintegrin and cysteine-rich) of fertilin beta evolving under positive selection. The region 3' to the EGF-like domain of fertilin alpha, where the transmembrane and cytoplasmic tail regions are supposed to be localized, showed higher d(N) and d(S) than any other fertilin alpha region. However, it was not possible to identify positively selected codon sites due to ambiguous alignments of the carboxy-end region (ClustalX vs. DiAlign2). When this region was excluded from the PAML analysis, most single positively selected codon sites were concentrated within adhesion domains (cysteine-rich and EGF-like). The use of an ancestral sequence prior to a recent duplication event of fertilin alpha among non-Hominidae primates (Macaca, Papio, and Saguinus) revealed that the duplication is partially responsible for masking the detection of positively selected sites within the disintegrin domain. Finally, most ADAM genes with a potential role in sperm maturation and/or fertilization showed significantly higher d(N) estimates than other ADAM genes.

Development of an operational synaptobrevin-based fluorescent substrate for tetanus neurotoxin quantification

Tetanus neurotoxin (TTx), produced by Clostridium tetani, is a two-chain polypeptide with a heavy molecular chain (HC; 100 kDa) and a light molecular chain (LC; 50 kDa) linked by a disulphide bridge. The low-molecular-mass chain is classified as a zinc metalloprotease (EC 3.4.24.68) with specific hydrolysis on synaptobrevin. With the known enzymic activity for the LC of TTx, we developed a quantification method using a quenched fluorescence peptide substrate based on the synaptobrevin sequence (fragments 73-82), suitable for direct determination of the whole TTx (HC+LC) even in crude production batches, without the necessity of purification and reduction steps to isolate the LC of TTx. The rate of substrate hydrolysis was 200 nmol/min and it was totally inhibited by EDTA, anti-recombinant fragment C antibody, and the cleavage was in a single bond (Gln-Phe) with purified and crude TTx. Besides, ELISA applied to the anti-TTx serum produced at our Institute showed cross-reaction with every fraction of the crude TTx extract. Another aspect is that TTx activity depends on the storage time, reaching a maximum on day 10. The results obtained suggest that the use of the new fluorescent substrate, Abz-synaptobrevin(73-82)-EDDnp, enables easy and quick determination of TTx. It is a good alternative to some of the existing methods such as flocculation assay, and it can replace, under some conditions, the biological assays (minimal mortal dose).

Molecular determinants of metalloproteinase substrate specificity: matrix metalloproteinase substrate binding domains, modules, and exosites

The function of ancillary domains and modules attatched to the catalytic domain of mutidomain proteases, such as the matrix metalloproteinases (MMPs), are not well understood. The importance of discrete MMP substrate binding sites termed exosites on domains located outside the catalytic domain was first demonstrated for native collagenolysis. The essential role of hemopexin carboxyl-domain exosites in the cleavage of noncollagenous substrates such as chemokines has also been recently revealed. This article updates a previous review of the role of substrate recognition by MMP exosites in both preparing complex substrates, such as collagen, for cleavage and for tethering noncollagenous substrates to MMPs for more efficient proteolysis. Exosite domain interaction and movements--"molecular tectonics"--that are required for native collagen triple helicase activity are discussed. The potential role of collagen binding in regulating MMP-2 (gelatinase A) activation at the cell surface reveals unexpected consequences of substrate interactions that can lead to collagen cleavage and regulation of the activation and activity of downstream proteinases necessary to complete the collagenolytic cascade.

Functional classification of ADAMs based on a conserved motif for binding to integrin alpha 9beta 1: implications for sperm-egg binding and other cell interactions

ADAMs (a disintegrin and metalloproteases) are members of the metzincin superfamily of metalloproteases. Among integrins binding to disintegrin domains of ADAMs are alpha(9)beta(1) and alpha(v)beta(3), and they bind in an RGD-independent and an RGD-dependent manner, respectively. Human ADAM15 is the only ADAM with the RGD motif in the disintegrin domain. Thus, both integrin alpha(9)beta(1) and alpha(v)beta(3) recognize the ADAM15 disintegrin domain. We determined how these integrins recognize the ADAM15 disintegrin domain by mutational analysis. We found that the Arg(481) and the Asp-Leu-Pro-Glu-Phe residues (residues 488-492) were critical for alpha(9)beta(1) binding, but the RGD motif (residues 484-486) was not. In contrast, the RGD motif was critical for alpha(v)beta(3) binding, but the other residues flanking the RGD motif were not. As the RX(6)DLPEF alpha(9)beta(1) recognition motif (residues 481-492) is conserved among ADAMs, except for ADAM10 and 17, we hypothesized that alpha(9)beta(1) may recognize disintegrin domains in all ADAMs except ADAM10 and 17. Indeed we found that alpha(9)beta(1) bound avidly to the disintegrin domains of ADAM1, 2, 3, and 9 but not to the disintegrin domains of ADAM10 and 17. As several ADAMs have been implicated in sperm-oocyte interaction, we tested whether the functional classification of ADAMs, based on specificity for integrin alpha(9)beta(1), applies to sperm-egg binding. We found that the ADAM2 and 15 disintegrin domains bound to oocytes, but the ADAM17 disintegrin domain did not. Furthermore, the ADAM2 and 15 disintegrin domains effectively blocked binding of sperm to oocytes, but the ADAM17 disintegrin domain did not. These results suggest that oocytes and alpha(9)beta(1) have similar binding specificities for ADAMs and that alpha(9)beta(1), or a receptor with similar specificity, may be involved in sperm-egg interaction during fertilization. As alpha(9)beta(1) is a receptor for many ADAM disintegrins and alpha(9)beta(1) and ADAMs are widely expressed, alpha(9)beta(1)-ADAM interaction may be of a broad biological importance.

Identification of quorum-quenching N-acyl homoserine lactonases from Bacillus species

A range of gram-negative bacterial species use N-acyl homoserine lactone (AHL) molecules as quorum-sensing signals to regulate different biological functions, including production of virulence factors. AHL is also known as an autoinducer. An autoinducer inactivation gene, aiiA, coding for an AHL lactonase, was cloned from a bacterial isolate, Bacillus sp. strain 240B1. Here we report identification of more than 20 bacterial isolates capable of enzymatic inactivation of AHLs from different sources. Eight isolates showing strong AHL-inactivating enzyme activity were selected for a preliminary taxonomic analysis. Morphological phenotypes and 16S ribosomal DNA sequence analysis indicated that these isolates probably belong to the species Bacillus thuringiensis. Enzymatic analysis with known Bacillus strains confirmed that all of the strains of B. thuringiensis and the closely related species B. cereus and B. mycoides tested produced AHL-inactivating enzymes but B. fusiformis and B. sphaericus strains did not. Nine genes coding for AHL inactivation were cloned either by functional cloning or by a PCR procedure from selected bacterial isolates and strains. Sequence comparison of the gene products and motif analysis showed that the gene products belong to the same family of AHL lactonases.

Thrombotic thrombocytopenic purpura (TTP)--an enigmatic disease finally resolved?

Thrombocytopenic thrombocytopenic purpura (TTP), characterized by hemolytic anemia, thrombocytopenia and fluctuating neurological abnormalities, was almost universally fatal until in the 1970s, when it was discovered that remissions could usually be achieved by exchanging plasma from patients with that of donors. For the following 25 years, this therapy was routinely used without any real understanding of why it was effective. Three recent papers published almost simultaneously offer insights into the molecular basis of TTP, a rationale for why plasma exchange is helpful, and avenues for development of new and highly specific therapeutic agents.

Crotalin, a vWF and GP Ib cleaving metalloproteinase from venom of Crotalus atrox

Binding of von Willebrand factor (vWF) to a variety of extracellular matrix (ECM) components and to platelet glycoprotein (GP) Ib-IX-V complex is important in mediating platelet adhesion and aggregation in the early stage of hemostasis. We previously purified a potent antithrombotic protein, named crotalin, functionally acting as a GP lb antagonist (1). In this study, we further characterized crotalin as a P-I metalloproteinase with a molecular mass of 25 kDa as determined by gel filtration and two-dimensional SDS-PAGE. Crotalin is a vWF binding and cleaving metalloproteinase. In addition, crotalin cleaved platelet GP lb as judged by flow cytometry and Western blotting. The multiple effects of crotalin on vWF and platelet GP lb antagonized ristocetin-, but not collagen and thrombin-induced platelet aggregation, suggesting that its effect is specific. We also found that crotalin autoproteolytically degraded to approximately 14 and approximately 10 kDa fragments in the presence of SDS. Interestingly, both degradation fragments, intact and reduced crotalin were able to bind vWF, suggesting the binding of crotalin to vWF is conformation-independent. In conclusion, the results presented further explain the potent antithrombotic effect of crotalin in vivo. In addition, the multiple effects of crotalin may be used as a tool to determine the binding motifs that are responsible for the vWF-ECMs or vWF-GP lb interaction.

The role of matrix metalloproteinase genes in glioma invasion: co-dependent and interactive proteolysis

Matrix metalloproteinases (MMPs) are cation-dependent endopeptidases which have been implicated in the malignancy of gliomas. It is thought that the MMPs play a critical role in both metastasis and angiogenesis, and that interference with proteases might therefore deter local tumor dissemination and neovascularization. However, the attempt to control tumor-associated proteolysis will rely on better definition of the normal tissue function of MMPs, an area of study still in its infancy in the central nervous system (CNS). Understanding the role of MMP-mediated proteolysis in the brain relies heavily on advances in other areas of molecular neuroscience, most notably an understanding of extracellular matrix (ECM) composition and the function of cell adhesion molecules such as integrins, which communicate knowledge of ECM composition intracellularly. Recently, protease expression and function has been shown to be strongly influenced by the functional state and signaling properties of integrins. Here we review MMP function and expression in gliomas and present examples of MMP profiling studies in glioma tissues and cell lines by RT-PCR and Western blotting. Co-expression of MMPs and certain integrins substantiates the gathering evidence of a functional intersection between the two, and inhibition studies using recombinant TIMP-1 and integrin antisera demonstrate significant inhibition of glioma invasion in vitro. Use of promising new therapeutic compounds with anti-MMP and anti-invasion effects are discussed. These data underline the importance of functional interaction of MMPs with accessory proteins such as integrins during invasion, and the need for further studies to elucidate the molecular underpinnings of this process.

Type II CAAX prenyl endopeptidases belong to a novel superfamily of putative membrane-bound metalloproteases

In this article, a novel, large and diverse superfamily of putative membrane-bound proteins that includes the type II CAAX prenyl endopeptidases is described. The majority of the members of this superfamily are hypothetical proteins from bacteria and plants. Analysis of the conserved motifs, combined with available experimental data, suggests that these proteins are putative metal-dependent proteases that are potentially involved in protein and/or peptide modification and secretion.

The role of proteolysis in Alzheimer's disease

Alzheimer's disease is characterised by the progressive deposition of the 4 kDa beta-amyloid peptide (A beta) in extracellular senile plaques in the brain. A beta is derived by proteolytic cleavage of the amyloid precursor protein (APP) by various proteinases termed secretases. alpha-Secretase is inhibited by hydroxamate-based zinc metalloproteinase inhibitors such as batimastat with I50 values in the low micromolar range, and displays many properties in common with the secretase that releases angiotensin converting enzyme. A cell impermeant biotinylated derivative of one such inhibitor completely blocked the release of APP from the surface of neuronal cells, indicating that alpha-secretase cleaves APP at the cell-surface. A range of hydroxamate-based compounds have been used to distinguish between alpha-secretase and tumour necrosis factor-alpha convertase, a member of the ADAMs (a disintegrin and metalloproteinase-like) family of zinc metalloproteinases. Recent data suggests that the presenilins may be aspartyl proteinases with the specificity of gamma-secretase. Although APP and the presenilins are present in detergent-insoluble, cholesterol- and glycosphingolipid-rich lipid rafts, they do not behave as typical lipid raft proteins, and thus it is unclear whether these membrane domains are the sites for proteolytic processing of APP.

[Implication of extracellular matrix metalloproteinases in the course of chronic inflammatory airway diseases]

Matrix metalloproteinases (MMPs) are major proteolytic enzymes that are involved in extracellular matrix (ECM) turn over. MMP-2 (gelatinase A) and MMP-9 (gelatinase B) cleave type IV collagen, which is an important constituent of basement membrane. These enzymes play an important role in normal tissue homeostasis, but imbalance between MMPs and their tissue inhibitors (TIMPs) is thought to be a critical factor in regulating tissue remodeling. MMP-2 is produced by fibroblasts, endothelial, and epithelial cells, while MMP-9 is mainly produced by inflammatory cells. The role of MMPs was investigated through biochemical analysis or in situ expression, in the pathogenesis of two chronic inflammatory airway diseases, asthma and nasal polyposis. Both are characterized with the accumulation of active inflammatory cells, matrix remodeling and epithelial changes. Increased levels of MMP-9 and TIMP-1 were found in asthmatic subjects and NP. In NP, MMP-9 expression was detected in epithelial, endothelial and inflammatory cells. In this setting, MMP-9 could play a crucial role in the transmigration of basement membrane components by inflammatory cells leading to inflammatory cell accumulation and maintenance of inflammation in airway. Moreover, MMP-9 may contribute to cell migration, an important mechanism involved in the repair of the respiratory epithelium.

Interactions between tumour cells and stromal cells and proteolytic modification of the extracellular matrix by metalloproteinases in cancer

Over the last few years a growing number of matrix degrading metalloproteinases have been implicated in cancer. These include in particular the matrix metalloproteinases (MMPs) which have been shown to be associated with a large variety of human malignancies, and the metalloproteinases with a disintegrin domain (ADAMs) whose potential role in cancer has begun to be examined. The expression of MMPs in human cancer is the result of a complex interaction between tumour cells and non-malignant stromal cells including fibroblasts, endothelial cells and inflammatory cells which all actively participate in the production of MMPs in tumour tissue. The proteolytic modification of the extracellular matrix by these proteases does more than allow malignant cells to locally invade and form distant metastasis. It significantly alters the tumour micro-environment and modifies the contacts between tumour cells and extracellular matrix proteins. These changes can affect essential cellular functions such as growth, survival, migration and even drug resistance. As our understanding of the nature of the contacts between tumour cells and a proteolytically modified extracellular matrix continues to progress, it is likely that novel therapeutic approaches to modify tumour cell behaviour will be identified.

Mapping of protein surface cavities and prediction of enzyme class by a self-organizing neural network

An automated computer-based method for mapping of protein surface cavities was developed and applied to a set of 176 metalloproteinases containing zinc cations in their active sites. With very few exceptions, the cavity search routine detected the active site among the five largest cavities and produced reasonable active site surfaces. Cavities were described by means of solvent-accessible surface patches. For a given protein, these patches were calculated in three steps: (i) definition of cavity atoms forming surface cavities by a grid-based technique; (ii) generation of solvent accessible surfaces; (iii) assignment of an accessibility value and a generalized atom type to each surface point. Topological correlation vectors were generated from the set of surface points forming the cavities, and projected onto the plane by a self-organizing network. The resulting map of 865 enzyme cavities displays clusters of active sites that are clearly separated from the other cavities. It is demonstrated that both fully automated recognition of active sites, and prediction of enzyme class can be performed for novel protein structures at high accuracy.

Metalloproteinases: role in breast carcinogenesis, invasion and metastasis

The matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases. Their primary function is degradation of proteins in the extracellular matrix. Currently, at least 19 members of this family are known to exist. Based on substrate specificity and domain organization, the MMPs can be loosely divided into four main groups: the interstitial collagenases, gelatinases, stromelysins and membrane-type MMPs. Recent data from model systems suggest that MMPs are involved in breast cancer initiation, invasion and metastasis. Consistent with their role in breast cancer progression, high levels of at least two MMPs (MMP-2 and stromelysin-3) have been found to correlate with poor prognosis in patients with breast cancer. Because MMPs are apparently involved in breast cancer initiation and dissemination, inhibition of these proteinases may be of value both in preventing breast cancer and in blocking metastasis of established tumours

The matrix metalloproteinases and their inhibitors in the treatment of pancreatic cancer

Matrix metalloproteinases (MMPs) are a family of zinc-containing proteolytic enzymes that break down extracellular matrix proteins (ECM) in physiological and pathological conditions. Disruption in the tight control of MMP metabolism occurs in cancer, resulting in excessive destruction of the ECM, neovascularization, tumor spread and metastases. Recent studies have shown that overexpression of MMPs is associated with poor prognosis. Several MMP inhibitors have been developed and preclinical trials have confirmed a reduction in tumor spread and metastases. Marimastat is a broad spectrum inhibitor, and recent published results shows the drug is well tolerated in patients with advanced cancer. Phase II studies which have used marimistat alone or in combination with other cytotoxic agents, have produced encouraging results with improved survival. Phase III trials are now underway for the use of marimastat in advanced pancreatic cancer and as an adjuvant therapy in patients following resection of pancreatic cancer.

Macrocyclic hydroxamate inhibitors of matrix metalloproteinases and TNF-alpha production

Several macrocyclic, hydroxamate derivatives were synthesized and evaluated as inhibitors of matrix metalloproteinases (MMPs) and tumour necrosis factor-alpha (TNF-alpha) production. These macrocycles are anti-succinate based inhibitors linked from P1 to P2'. A variety of functionality was installed at the P1-P2' linkage, which gave inhibitors that displayed excellent MMP inhibition and good TNF-alpha suppression.

A novel clan of zinc metallopeptidases with possible intramembrane cleavage properties

Computer-based database searching and protein multiple sequence alignment has identified a novel clan of zinc metallopeptidases, which, by phylogenetic analysis, has been shown to contain six subfamilies. The family is characterized by four common transmembrane segments and three conserved sequence motifs. The combination of topology analysis and motif identification has detected three potential Zn2+ coordinating residues. Only two of the sequences of this novel zinc metallopeptidase clan possess any functional annotation, one of which is able to cleave its substrate within a cytosol/transmembrane segment junction. A number of observations suggest that the remaining members of this novel clan may also cleave their substrates within transmembrane segments.

Characterization of the hemorrhagic reaction caused by Vibrio vulnificus metalloprotease, a member of the thermolysin family

Vibrio vulnificus is an opportunistic human pathogen causing wound infections and septicemia, characterized by hemorrhagic and edematous damage to the skin. This human pathogen secretes a metalloprotease (V. vulnificus protease [VVP]) as an important virulence determinant. When several bacterial metalloproteases including VVP were injected intradermally into dorsal skin, VVP showed the greatest hemorrhagic activity. The level of the in vivo hemorrhagic activity of the bacterial metalloproteases was significantly correlated with that of the in vitro proteolytic activity for the reconstituted basement membrane gel. Of two major basement membrane components (laminin and type IV collagen), only type IV collagen was easily digested by VVP. Additionally, the immunoglobulin G antibody against type IV collagen, but not against laminin, showed sufficient protection against the hemorrhagic reaction caused by VVP. Capillary vessels are known to be stabilized by binding of the basal surface of vascular endothelial cells to the basement membrane. Therefore, specific degradation of type IV collagen may cause destruction of the basement membrane, breakdown of capillary vessels, and leakage of blood components including erythrocytes.

A superfamily of metalloenzymes unifies phosphopentomutase and cofactor-independent phosphoglycerate mutase with alkaline phosphatases and sulfatases

Sequence analysis of the probable archaeal phosphoglycerate mutase resulted in the identification of a superfamily of metalloenzymes with similar metal-binding sites and predicted conserved structural fold. This superfamily unites alkaline phosphatase, N-acetylgalactosamine-4-sulfatase, and cerebroside sulfatase, enzymes with known three-dimensional structures, with phosphopentomutase, 2,3-bisphosphoglycerate-independent phosphoglycerate mutase, phosphoglycerol transferase, phosphonate monoesterase, streptomycin-6-phosphate phosphatase, alkaline phosphodiesterase/nucleotide pyrophosphatase PC-1, and several closely related sulfatases. In addition to the metal-binding motifs, all these enzymes contain a set of conserved amino acid residues that are likely to be required for the enzymatic activity. Mutational changes in the vicinity of these residues in several sulfatases cause mucopolysaccharidosis (Hunter, Maroteaux-Lamy, Morquio, and Sanfilippo syndromes) and metachromatic leucodystrophy.

Role of tissue inhibitor of metalloproteinases-2 (TIMP-2) in regulation of pro-gelatinase A activation catalyzed by membrane-type matrix metalloproteinase-1 (MT1-MMP) in human cancer cells

To clarify the regulatory mechanism of pro-gelatinase A (proGelA) activation at a cellular level, expression of gelatinase A (GelA), three MT-MMPs, and TIMP-2 was examined with 11 human cancer cell lines cultured in the presence and absence of stimulants. MT1-MMP mRNA was expressed in 8 cell lines, while MT2-MMP and MT3-MMP mRNAs were expressed in fewer cell lines. The cells with high proGelA activation strongly expressed MT1-MMP mRNA but not MT2-MMP and MT3-MMP mRNAs, suggesting that MT1-MMP was responsible for the proGelA activation in the cancer cells. Treatments with concanavalin A (Con A) and a phorbor ester (TPA) enhanced the MT1-MMP expression, but only Con A stimulated the proGelA activation in many cell lines. In HT1080 fibrosarcoma cells, however, TPA also stimulated the activation. The level of TIMP-2 secreted into culture medium inversely correlated with proGelA activation. For example, 2 squamous cell carcinoma lines (HSC-3 and HSC-4) and 3 HT1080 clones, which efficiently activated proGelA, secreted little TIMP-2 into medium, whereas other cell lines and other HT1080 clones, which hardly activated proGelA, secreted TIMP-2 at high levels. When HSC-3 cells were incubated with TIMP-2 protein or transfected with TIMP-2 cDNA, the proGelA activation was strongly inhibited. These results indicated that extracellular TIMP-2 was an important negative regulator of proGelA activation. However, the level of extracellular TIMP-2 was not consistent with that of TIMP-2 mRNA in some cell lines. Other experimental results suggested that TIMP-2 might be rapidly metabolized after binding to MT1-MMP, and Con A treatment might stabilize the complex of TIMP-2 and MT1-MMP on cell membranes.

Role of matrix metalloproteinases and their inhibitors in pancreatic cancer

BACKGROUND/AIMS

The matrix metalloproteinases are a family of proteolytic enzymes which normally have an important physiological role in tissue remodelling and wound healing, but more recently have been implicated in the proteolytic events which occur during tumour invasion.

METHODS

The expanding family of matrix metalloproteinases and the specific tissue inhibitors of the matrix metalloproteinases are reviewed including their classification, structure, function, regulation of activity, and tissue expression with particular reference to pancreatic cancer. The effect of synthetic matrix metalloproteinases inhibitors in preclinical studies is reviewed together with the results of ongoing clinical trials in pancreatic cancer.

RESULTS

Pancreatic cancer is associated with the overexpression of several matrix metalloproteinases with a reduced expression of their specific inhibitors. Orally bioavailable matrix metalloproteinase inhibitors have successfully completed phase I/II clinical trials with promising results. Multicentre randomised controlled phase IIb/III clinical trials aren currently under way in pancreatic cancer.

CONCLUSIONS

Matrix metalloproteinase inhibition may represent a novel approach to the management of pancreatic cancer not only in advanced disease, but in the adjuvant treatment setting following tumour resection either alone or in combination with existing chemotherapeutic agents.

Matrix metalloproteinases and coronary artery disease: a novel therapeutic target

Matrix metalloproteinases (MMP) are a family of enzymes that selectively digest individual components of the extracellular matrix. Their function has been studied in both normal physiologic processes and pathologic states. In the blood vessel, MMPs play an important role in maintaining the vessel's integrity by breaking down extracellular matrix while new matrix is being synthesized. This is necessary to avoid weakening from continuous mechanical stresses. However, in certain environments, these MMPs may contribute to cardiovascular pathologic processes. The purpose of this review is to first discuss the role of MMPs in coronary vascular disease. Evidence suggests that MMPs contribute to the development of de novo atherosclerotic plaques and postangioplasty restenotic plaques by allowing smooth muscle cells to migrate from the vascular media to the intima. Evidence also suggests that MMPs contribute to the rupture of these plaques by degrading the fibrous cap that surrounds them. With this increased molecular information that concerns the pathogenesis of coronary vascular disease, new molecular therapies aimed at altering these processes are being investigated. The rationale, mode of delivery, and prospects for success of these therapies will also be discussed here.

Ostertagia circumcincta: isolation of a partial cDNA encoding an unusual member of the mitochondrial processing peptidase subfamily of M16 metallopeptidases

A reverse-transcriptase polymerase chain reaction (PCR) procedure was used to isolate an Ostertagia circumcincta partial cDNA encoding a protein with general primary sequence features characteristic of members of the mitochondrial processing peptidase (MPP) subfamily of M16 metallopeptidases. The structural relationships of the predicted protein (Oc MPPX) with MPP subfamily proteins from other species (including the model free-living nematode Caenorhabditis elegans) were examined, and Northern analysis confirmed the expression of the Oc mppx gene in adult nematodes.

[Current data on metalloproteinases, obligatory partners of tumor progression]

Metastasis is a complex process that requires sequential interactions between the invasive cell and the extracellular matrix. These interactions are characterized by cell adhesion and migration. Cell adhesion involves specific receptors. Migration requires the induction and secretion of proteolytic enzymes belonging to the matrix metalloproteinases (MMP) family. In most cancers, stromal cells secrete collagenases or gelatinases under the influence of cancer cells. The MMPs are secreted as inactive forms. In order to cross basement membrane and then to reach the extracellular matrix, the MMPs undergo an activation step which involves plasmin, growth factors or membrane-type matrix metalloproteinases (MT-MMPs). The molecular mechanisms involves protein-kinase C activation. MMPs are associated with tissue inhibitors of metalloproteinases (TIMPs) with which they form high affinity non covalent 1:1 complexes. Upregulation of MMPs or down regulation of TIMPs lead to an imbalance of this ratio which favours invasive process. Consequently, the development of matrix metalloproteinase inhibitors such as Batimastat may provide interesting tools for cancer therapy.

Matrix metalloproteinases. Novel targets for directed cancer therapy

Matrix metalloproteinases (MMPs), or matrixins, are a family of zinc endopeptidases that play a key role in both physiological and pathological tissue degradation. Normally, there is a careful balance between cell division, matrix synthesis and matrix degradation, which is under the control of cytokines, growth factors and cell matrix interactions. The MMPs are involved in remodelling during tissue morphogenesis and wound healing. Under pathological conditions, this balance is altered: in arthritis, there is uncontrolled destruction of cartilage; in cancer, increased matrix turnover is thought to promote tumour cell invasion. The demonstration of a functional role of MMPs in arthritis and tumour metastasis raises the possibility of therapeutic intervention using synthetic MMP inhibitors with appropriate selectivity and pharmacokinetics. As the process of drug discovery focuses on structure-based design, efforts to resolve the 3-dimensional structures of the MMP family have intensified. Several novel MMP inhibitors have been identified and are currently being investigated in clinical trials. The structural information that is rapidly accumulating will be useful in refining the available inhibitors to selectively target specific MMP family members. In this review, we focus on the role of MMPs and their inhibitors in tumour invasion, metastasis and angiogenesis, and examine how MMPs may be targeted to prevent cancer progression.

Secretion of different types of gelatinases from cultured human keratinocytes

We investigated gelatinolytic enzymes derived from cultured human keratinocytes. Using a zymograph, we detected 92 kDa and 72 kDa gelatinases as major components and 83 kDa as a minor component from a conditioned cultured medium (BSL-K110, Kyokutoseiyaku Co.) of keratinocytes. After several passages, the 72 kDa band disappeared, and the 83 kDa band became dominant in another conditioned culture medium (K-GM, Kurashikibouseki Co.); these keratinocytes had a relatively differentiated appearance. These results suggest that some mechanism may regulate the secretion of selected types of gelatinase from keratinocytes under different conditions.

[Metalloproteinases in the extracellular matrix: structure and activity]

The matrix metalloproteinases (MMP) are a multigenic family involving 14 enzymes which can cleave most, if not all, the components of the extracellular matrix (interstitium and basement membranes). The present work reports on the main structural characteristics, the substrate preference and the site synthesis of these proteinases and their inhibitors (TIMP). Human MMPs are produced by various cell types and are involved in the remodelling of the extracellular matrix in many physiological and pathophysiological circumstances. Elastolytic MMPs produced by monocytes and/or macrophages (matrilysin, gelatinases, macrophage elastase) are likely to be implicated in the development of acquired pulmonary emphysema.

The Acer gene of Drosophila codes for an angiotensin-converting enzyme homologue

Mammalian angiotensin-converting enzyme (ACE) exists as two forms, somatic (sACE), controlling blood pressure via angiotensin II, and testicular (tACE), whose function is unknown. The former has two highly homologous N- and C-terminal Zn2+ metallopeptidase active sites, whereas the latter only has one, which is identical to the C-terminal domain of sACE. We have sequenced 2452 bases of a 3.1-kb mRNA whose predicted translation product shows 40% identity with mammalian testicular ACE, and 48% identity with an already identified Drosophila homologue of ACE (Ance). We have termed this gene Acer (Angiotensin converting enzyme-related). Acer mRNA is found in the developing dorsal vessel (heart) during embryogenesis. Phylogenetic analysis indicates that duplication of an ancestral ACE gene occurred in the lineage leading to the arthropods, independently of the duplication which gave rise to the two domain somatic ACE of mammals.

Role of matrix metalloproteinases in abdominal aortic aneurysms

Considerable progress has been made toward characterizing the enzymes and proteolytic events that occur in established human abdominal aortic aneurysms (AAA). Through studies involving a number of different laboratories and various experimental approaches, enzymes of the matrix metalloproteinase (MMP) family have consistently emerged as important molecular participants in aneurysm disease. The finding that elastolytic MMPs, particularly MMP-9 and MMP-2, are expressed and produced in increased amounts in human aneurysm tissue, has led to the possibility that these enzymes might serve as rational targets for pharmacotherapy in this disease. Recent studies using MMP-inhibiting tetracycline derivatives in the elastase-induced rodent model of AAA indicate that metalloproteinase suppression is a feasible and successful approach in the experimental setting. The definitive proof-of-principle for the therapeutic efficacy of anti-MMP or other anti-proteinase strategies to limit the growth of small AAA, however, will remain unknown until specifically tested in clinical trials.