The gelatinase MMP-9like is involved in regulation of LPS inflammatory response in Ciona robusta

Matrix metalloproteinases (MMPs) are a family of endopeptidases collectively able to degrade the components of the extracellular matrix (ECM), with important roles in many biological processes, such as embryogenesis, normal tissue remodelling, angiogenesis and wound healing. New views on the function of MMPs reveal that they regulate inflammatory response and therefore might represent an early step in the evolution of the immune system. MMPs can affect the activity of cytokines involved in inflammation including TGF-β and TNF-α. MMPs are widely distributed in all kingdoms of life and have likely evolved from a single-domain protein which underwent successive rounds of duplications. In this study, we focused on the Ciona robusta (formerly known as Ciona intestinalis) MMP gelatinase homologue. Gene organization, phylogenetic analysis and 3D modeling supported the closest correlation of C. robusta gelatinase with the human MMP-9. Real-time PCR analysis and zymographic assay showed a prompt expression induced by LPS inoculation and an upregulation of enzymatic activity. Furthermore, we showed that before of the well-known increase of TGF-β and TNF-α levels, a MMP-9like boost occurred, suggesting a possible involvement of MMP-9like in regulating inflammatory response in C. robusta.

In situ analysis of gelatinolytic activity in human dentin

Matrix metalloproteinases (MMPs) such as gelatinases are differentially expressed in human tissues. These enzymes cleave specific substrates involved in cell signaling, tissue development and remodeling and tissue breakdown. Recent evidences show that gelatinases are crucial for normal dentin development and their activity is maintained throughout the entire tooth function in the oral cavity. Due to the lack of information about the exact location and activity of gelatinases in mature human dentin, the present study was designed to examine gelatinolytic levels in sound dentin. In situ zymography using confocal microscopy was performed on both mineralized and demineralized dentin samples. Sites presenting gelatinase activity were identified throughout the entire biological tissue pursuing different gelatinolytic levels for distinct areas: predentin and dentinal tubule regions presented higher gelatinolytic activity compared to intertubular dentin. Dentin regions with higher gelatinolytic activity immunohistochemically were partially correlated with MMP-2 expression. The maintenance of gelatinolytic activity in mature dentin may have biological implications related to biomineralization of predentin and tubular/peritubular dentinal regions, as well as regulation of defensive mechanisms of the dentin-pulp complex.

Pathological-Condition-Driven Construction of Supramolecular Nanoassemblies for Bacterial Infection Detection

A pyropheophorbide-α-based building block (Ppa-PLGVRG-Van) can be used to construct self-aggregated superstructures in vivo for highly specific and sensitive diagnosis of bacterial infection by noninvasive photoacoustic tomography. This in vivo supramolecular chemistry approach opens a new avenue for efficient, rapid, and early-stage disease diagnosis with high sensitivity and specificity.

Neuropeptide Y is a physiological substrate of fibroblast activation protein: Enzyme kinetics in blood plasma and expression of Y2R and Y5R in human liver cirrhosis and hepatocellular carcinoma

Fibroblast activation protein (FAP) is a dipeptidyl peptidase (DPP) and endopeptidase that is weakly expressed in normal adult human tissues but is greatly up-regulated in activated mesenchymal cells of tumors and chronically injured tissue. The identities and locations of target substrates of FAP are poorly defined, in contrast to the related protease DPP4. This study is the first to characterize the physiological substrate repertoire of the DPP activity of endogenous FAP present in plasma. Four substrates, neuropeptide Y (NPY), peptide YY, B-type natriuretic peptide and substance P, were analyzed by mass spectrometry following proteolysis in human or mouse plasma, and by in vivo localization in human liver tissues with cirrhosis and hepatocellular carcinoma (HCC). NPY was the most efficiently cleaved substrate of both human and mouse FAP, whereas all four peptides were efficiently cleaved by endogenous DPP4, indicating that the in vivo degradomes of FAP and DPP4 differ. All detectable DPP-specific proteolysis and C-terminal processing of these neuropeptides was attributable to FAP and DPP4, and plasma kallikrein, respectively, highlighting their combined physiological significance in the regulation of these neuropeptides. In cirrhotic liver and HCC, NPY and its receptor Y2R, but not Y5R, were increased in hepatocytes near the parenchymal-stromal interface where there is an opportunity to interact with FAP expressed on nearby activated mesenchymal cells in the stroma. These novel findings provide insights into the substrate specificity of FAP, which differs greatly from DPP4, and reveal a potential function for FAP in neuropeptide regulation within liver and cancer biology.

In Situ Formation of Nanofibers from Purpurin18-Peptide Conjugates and the Assembly Induced Retention Effect in Tumor Sites

An assembly-induced retention effect for enhanced tumor photoacoustic (PA) imaging and therapeutics is described. A responsive small-molecule precursor is prepared that simultaneously self-assembles into nanofibers in tumor sites that exhibit an assembly-induced retention effect, which results in an improved PA imaging signal and enhanced therapeutic efficacy. This successful proof-of-concept study paves the way to develop novel supramolecular biomaterials for cancer diagnostics and therapeutics.

A new pepstatin-insensitive thermopsin-like protease overproduced in peptide-rich cultures of Sulfolobus solfataricus

In this study, we gain insight into the extracellular proteolytic system of Sulfolobus solfataricus grown on proteinaceous substrates, providing further evidence that acidic proteases were specifically produced in response to peptide-rich media. The main proteolytic component was the previously isolated SsMTP (Sulfolobus solfataricus multi-domain thermopsin-like protease), while the less abundant (named SsMTP-1) one was purified, characterized and identified as the sso1175 gene-product. The protein revealed a multi-domain organization shared with the cognate SsMTP with a catalytic domain followed by several tandemly-repeated motifs. Moreover, both enzymes were found spread across the Crenarchaeota phylum and belonging to the thermopsin family, although segregated into diverse phylogenetic clusters. SsMTP-1 showed a 75-kDa molecular mass and was stable in the temperature range 50–90 °C, with optimal activity at 70 °C and pH 2.0. Serine, metallo and aspartic protease inhibitors did not affect the enzyme activity, designating SsMTP-1 as a new member of the pepstatin-insensitive aspartic protease family. The peptide-bond-specificity of SsMTP-1 in the cleavage of the oxidized insulin B chain was uncommon amongst thermopsins, suggesting that it could play a distinct, but cooperative role in the protein degradation machinery. Interestingly, predictions of the transmembrane protein topology of SsMTP and SsMTP-1 strongly suggest a possible contribution in signal-transduction pathways.

Increased N-terminal cleavage of alpha-2-antiplasmin in patients with liver cirrhosis

BACKGROUND

The activity of alpha-2-antiplasmin (α2AP), the main fibrinolytic inhibitor, is modified by N- and C-terminal proteolytic cleavages. C-terminal cleavage converts plasminogen-binding α2AP (PB-α2AP) into a non-plasminogen-binding derivative. N-terminal cleavage by antiplasmin-cleaving enzyme (APCE), a soluble, circulating derivative of fibroblast activation protein (FAP), turns native Met-α2AP into Asn-α2AP, which is more quickly crosslinked into fibrin.

OBJECTIVES

We developed two novel enzyme-linked immunosorbent assays (ELISAs) to determine the N-terminal variation of α2AP to test the hypothesis that liver cirrhosis, characterized by increased expression of FAP/APCE, results in increased N-terminal cleavage of α2AP.

PATIENTS/METHODS

α2AP and FAP/APCE antigen levels were measured in the plasma samples of 75 patients with cirrhosis with different severities and 30 healthy control individuals. The percentage of N-terminal cleavage of α2AP was calculated.

RESULTS

Compared with levels (median [interquartile range]) in control individuals, total PB-α2AP levels and Met-PB-α2AP levels were reduced in cirrhosis patients (27.3 [21.4-41.3] μg mL(-1) vs. 56.2 [49.6-62.8] μg mL(-1) , P < 0.001, and 2.7 [1.7-5.5] μg mL(-1) vs. 12.1 [11.0-15.3] μg mL(-1) , P < 0.001, respectively). Interestingly, the percentage of N-terminal cleavage was increased in the patients (87.8 [85.0-91.6]% vs. 77.2 [72.2-79.8]% in controls, P < 0.001), as well as the plasma FAP/APCE levels (166 [60-550] ng mL(-1) in patients vs. 107 [67-157] ng mL(-1) in controls, P < 0.001). Additionally, all variables significantly correlated with the severity of disease.

CONCLUSIONS

Using our novel ELISAs we found increased N-terminal cleavage of α2AP in liver cirrhosis patients, which correlated with the severity of disease and is likely to have reflected the increased FAP/APCE levels in these patients.

Intelligently targeted drug delivery and enhanced antitumor effect by gelatinase-responsive nanoparticles

AIMS

The matrix metalloproteinase (MMP) 2/9, also known as collagenases IV and gelatinases A/B, play a key role in cancer invasion and metastasis. However, the clinical trials of the MMP inhibitors (MMPIs) ended up with disappointing results. In this paper, we synthesized a gelatinase-responsive copolymer (mPEG-PCL) by inserting a gelatinase cleavable peptide (PVGLIG) between mPEG and PCL blocks of mPEG-PCL for anticancer drug delivery to make use of MMP2/9 as an intelligent target for drug delivery.

MATERIALS AND METHODS

mPEG-pep-PCL copolymer was synthesized via ring-opening copolymerization and double-amidation. To evaluate whether Nanoparticles (NPs) prepared from this copolymer are superior to NPs prepared from mPEG-PCL, NPs prepared from mPEG-PCL copolymer were used as positive control. Docetaxel-loading NPs using mPEG-pep-PCL and mPEG-PCL were prepared by nano-precipitation method, mentioned as Gel-NPs and Con-NPs, respectively. The morphologic changes of the NPs after treatment with gelatinases were observed macroscopically by spectrophotometer and microscopically by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The cellular uptake amount and cytotoxicity of Gel-NPs and Con-NPs, respectively, in cell lines with different levels of gelatinase expression were studied. Moreover, the cytotoxicity study on the primary cancer cells isolated from pericardial fluids from a patient with late-stage lung cancer was conducted.

RESULTS

The Gel-NPs aggregated in response to gelatinases, which was confirmed macroscopically and microscopically. The cellular uptake amount of Gel-NPs was correlated with the level of gelatinases. The in vitro antitumor effect of Gel-NPs was also correlated with the level of gelatinases and was superior to Taxotere (commercially available docetaxel) as well as the Con-NPs. The cytotoxicity study on the primary lung cancer cells also confirmed the effectiveness of Gel-NPs.

CONCLUSION

The results in this study preliminarily demonstrated the effectiveness of gelatinase-responsive targeting strategy and the prospect of this intelligent nano-drug delivery system though further studies are needed.

Ubiquitin-like protein from human placental extract exhibits collagenase activity

An aqueous extract of human placenta exhibits strong gelatinase/collagenase activity in zymography. 2-D gel electrophoresis of the extract with gelatin zymography in the second dimension displayed a single spot, identified as ubiquitin-like component upon MALDI/TOF MS/MS analysis. Immunoblot indicated presence of ubiquitin and absence of collagenase in the extract. Collagenase activity of the ubiquitin-like component was confirmed from the change in solubility of collagen in aqueous buffer, degradation of collagen by size-exclusion HPLC and atomic force microscopy. Quantification with DQ-gelatin showed that the extract contains 0.04 U/ml of collagenase activity that was inhibited up to 95% by ubiquitin antibody. Ubiquitin from bovine erythrocytes demonstrated mild collagenase activity. Bioinformatics studies suggest that placental ubiquitin and collagenase follow structurally divergent evolution. This thermostable intrinsic collagenase activity of placental extract might have wide physiological relevance in degrading and remodeling collagen as it is used as a drug for wound healing and pelvic inflammatory diseases.

Immersion mode material pocket dynamic mechanical analysis (IMP-DMA): a novel tool to study gelatinisation of purified starches and starch-containing plant materials

There is a clear need for improved methods for the study of the physical changes that occur in slurries and sol-gel systems that have significant water content. In this paper a novel immersion mode material pocket form of dynamic mechanical analysis (IMP-DMA) has been designed, combining material pocket technology to provide physical support to a powdered sample within an immersion bath. IMP-DMA allows the mechanical response of a powder during heating to be monitored in excess water. IMP-DMA was evaluated using a range of starch samples loaded as a slurry into a solid steel pocket, the mechanical responses of these samples were monitored as a function of temperature, and values for modulus and tanδ peaks were found to correspond well with events occurring at both the onset and peak gelatinisation temperatures as measured by differential scanning calorimetry (DSC) (e.g. wheat starch has an onset and peak DSC temperature of 49.3 °C and 57.2 °C, respectively, and shows a peak in tanδ at 52.8 °C and a modulus peak at 57.7 °C). Some limitations were found in the ability of DMA to detect transitions in starches with low or high amylose contents. IMP-DMA was shown to be an effective tool for monitoring the changes in starch structure that occur during gelatinisation, both in purified starches and in more complex starch-containing food materials. Thus, a new hyphenated form of DMA is now available that permits the thermally induced transitions of particle water dispersions to be characterised.

The gelatinases and their inhibitors: the structure-activity relationships

The interest in gelatinases is increased because of their association in diverse human diseases, though the relationship between MMP expression and disease progression is very complex and varies in cell to cell. Targeting gelatinases in disease treatment is complicated by the fact that gelatinases are indispensable for normal development and physiology due to their multifunctionality, possible functional redundancy, context-dependent expression, and activity. They are secreted as inactive zymogens which are processed to become active by removal of N-terminal propeptide. The folded conformation of zymogen is required to keep the gelatinases in its latency. Acting on a broad spectrum of extracellular substrates, the gelatinases (both MMP-2 and MMP-9) are critical to the biological processes. Three-dimensional structures of gelatinase-inhibitor complexes and inhibition profiles of compounds screened on them provide an invaluable source to gain insight into the structural determinants as well as functional selectivity. The quest for selective MMP inhibitors (MMPIs) still remains a challenge in search of successful clinical candidates. An increased understanding of the structure, regulation, and function of the individual MMPs will likely lead to more effective strategies in the development of highly selective inhibitors for any given MMP that can then be exploited to achieve the desired drugs.

Enhancement of fibrinolysis by inhibiting enzymatic cleavage of precursor α2-antiplasmin

BACKGROUND AND OBJECTIVE

Resistance of thrombi to plasmin digestion depends primarily on the amount of α(2)-antiplasmin (α(2)AP) incorporated within fibrin. Circulating prolyl-specific serine proteinase, antiplasmin-cleaving enzyme (APCE), a homologue of fibroblast activation protein (FAP), cleaves precursor Met-α(2)AP between -Pro12-Asn13- to yield Asn-α(2)AP, which is crosslinked to fibrin approximately 13× more rapidly than Met-α(2)AP and confers resistance to plasmin. We reasoned that an APCE inhibitor might decrease conversion of Met-α(2)AP to Asn-α(2)AP and thereby enhance endogenous fibrinolysis.

METHODS AND RESULTS

We designed and synthesized several APCE inhibitors and assessed each vs. plasma dipeptidyl peptidase IV (DPPIV) and prolyl oligopeptidase (POP), which have amino acid sequence similarity with APCE. Acetyl-Arg-(8-amino-3,6-dioxaoctanoic acid)-D-Ala-L-boroPro selectively inhibited APCE vs. DPPIV, with an apparent K(i) of 5.7 nm vs. 6.1 μm, indicating that an approximately 1000-fold greater inhibitor concentration is required for DPPIV than for APCE. An apparent K(i) of 7.4 nm was found for POP inhibition, which is similar to 5.7 nm for APCE; however, the potential problem of overlapping FAP/APCE and POP inhibition was negated by our finding that normal human plasma lacks POP activity. The inhibitor construct caused a dose-dependent decrease of APCE-mediated Met-α(2)AP cleavage, which ultimately shortened plasminogen activator-induced plasma clot lysis times. Incubation of the inhibitor with human plasma for 22 h did not lessen its APCE inhibitory activity, with its IC(50) value in plasma remaining comparable to that in phosphate buffer.

CONCLUSION

These data establish that inhibition of APCE might represent a therapeutic approach for enhancing thrombolytic activity.

Co-purified gelatinases alter the stability and biological activities of human plasma fibronectin preparations

BACKGROUND AND OBJECTIVE

Fibronectin (FN) is an important cell adhesion molecule that is used widely to characterize cell behavior. Preparations of FN purified from human plasma by gelatin-Sepharose affinity chromatography typically also contain gelatin-binding gelatinases that may cleave FN, reduce its stability and alter its biological activities. Available methods for separating gelatinases from FN are resource demanding. Therefore, our objective was to devise a time- and cost-efficient protocol for purification of gelatinase-free FN.

MATERIAL AND METHODS

Experiments tested the elution profiles for FN and gelatinases from gelatin-Sepharose using a concentration range (1-7%) of dimethyl sulfoxide (DMSO) and 4 m urea as eluants. Subsequently, we explored the sequential application of those eluants for differential elution of gelatinases and FN using a single affinity column. Finally, experiments characterized the stability of purified FN with or without contaminating gelatinases, as well as the effects of FN degradation on cell attachment and migration.

RESULTS

Assay optimization demonstrated that pre-elution with 3% DMSO efficiently eliminated gelatinases but not FN from gelatin-Sepharose, whereas subsequent elution with 4 m urea released FN. Sequential elutions with DMSO and urea produced gelatinase-free FN, which was more stable than FN eluted by urea only. Fibronectin degradation did not affect human gingival fibroblast attachment, but increased cell migration significantly.

CONCLUSION

The present experiments devised a time- and cost-efficient protocol for eliminating gelatinases during purification of human plasma FN. Gelatinase-free FN preparations had greater stability, which may be essential for experiments because FN fragments have altered biological activities compared with intact FN.

[Methods for determining matrix metalloproteinase activity]

The paper describes methods for determining the activity of matrix metalloproteinases (MMP), primarily collagenases and gelatinases, by applying natural protein substrates. Reconstructed fluorescein-labeled type I collagen fibrils were used to determine collagenases as a substrate. The zymographic technique in polyacrylamide gel with copolymerized gelatin was employed for the identification and assay of gellatinases. These methods are rather sensitive, reproducible and may be used for screening. Collagenases specifically trigger the hydrolysis of fibrillar collagens; gelatinases are responsible for the hydrolysis of type IV collagen, the basis of basement membranes. MMP activity characterizes the development of a destructive or invasive process in the connective tissue matrix; this indicator is borne in mind when choosing therapeutic agents, has a prognostic value, determines targets for the development of pharmacological agents, and is required to understand the mechanism responsible for the destruction of matrix and for the development of invasion processes.

Purification and characterization of gelatinase-like proteinases from the dark muscle of common carp (Cyprinus carpio)

Gelatinolytic proteinases from common carp dark muscle were purified by 30-60% ammonium sulfate fractionation and a combination of chromatographic steps including ion exchange on DEAE-Sephacel, gel filtration on Sephacryl S-200, ion exchange on High-Q, and affinity on gelatin-Sepharose. The molecular masses of these proteinases as estimated by SDS-PAGE were 75, 67, and 64 kDa under nonreducing conditions. The enzymes revealed high activity at a slightly alkaline pH range, and their activities were investigated using gelatin as substrate. Metalloproteinase inhibitors, EDTA, EGTA, and 1,10-phenanthroline, almost completely suppressed the gelatinolytic activity, whereas other proteinase inhibitors did not show any inhibitory effect. Divalent metal ion Ca (2+) is essential for the gelatinolytic activity. Furthermore, these gelatinolytic proteinases hydrolyze native type I collagen effectively even at 4 degrees C, strongly suggesting their involvement in the texture softening of fish muscle during the post-mortem stage.

Selective processing of a follicular matrix metalloproteinase-2 isoform by human oviducal fluid

The present study demonstrates that a unique isoform of matrix metalloproteinase (MMP)-2 present in human follicular fluid (FF) can be processed selectively by human oviducal fluid (OF). A gelatin zymogram of untreated FF showed distinct 88-, 84- and 62-kDa gelatinases. Treatment of FF with EDTA resulted in the appearance of 110-kDa gelatinase (GA110). Most gelatinases, except for the 88- and 84-kDa gelatinases, were abolished by pretreatment with EDTA or phenanthroline, but not by pretreatment with a serine/threonine protease inhibitor. When EDTA-pretreated FF was mixed with OF, the GA110 of the FF was specifically reduced. The reduction in GA110 was dependent upon the amount of OF protein and the incubation period after mixing. Treatment of FF with aminophenylmercuric acetate reduced GA110 activity, but this reduction was accompanied by a concomitant increase of 62-kDa gelatinase activity. Anti-human MMP-2 antibody strongly reacted with both GA110 and 62-kDa gelatinases of FF, but only GA110 immunoreactivity was abolished when FF was mixed with OF. The results suggest that the GA110 of FF is an MMP-2 isoform that can be processed selectively by OF.

Biology of metalloproteinases

Matrix metalloproteinases (MMPs) occupy a central role in embryogenesis and in normal physiological conditions, such as proliferation, cell motility, remodeling, wound healing, angiogenesis, and key reproductive events. MMPs form a multigenic family of proteolytic, zinc-dependent enzymes, with 26 members described until present, displaying multidomain structures and substrate specificities. MMPs are involved in both the turnover and degradation of extracellular matrix (ECM) proteins and in the processing, activation, or deactivation of a variety of soluble factors. They are regulated at the level of transcription, activation of the precursor zymogens, and inhibition mainly by tissue inhibitors of metalloproteinases (TIMPs). Any loss in activity control may result in various diseases. This review provides an update of biological functions of MMPs, facilitating the understanding of the complex pathogenic mechanisms of medical conditions characterized by imbalance between MMP and TIMP expression. The design of potent specific inhibitors for MMPs represents a scientific challenge for the development of new therapies.

Dipeptide proline diphenyl phosphonates are potent, irreversible inhibitors of seprase (FAPα)

Dipeptidyl peptidase IV (DPP-IV) and seprase belong to a small group of membrane-bound, proline-specific serine proteases, the serine integral membrane proteases (SIMPs). Whilst DPP-IV is the most exhaustively studied peptidase in this class, relatively less is known about the inhibitor/substrate specificity of its close homolog seprase. Additionally, whereas, DPP-IV expression is largely ubiquitous, seprase expression is restricted to tumour and tissue remodelling sites in vivo. Consequently, the highly restricted expression and distribution of seprase potentially make it an excellent therapeutic target for the modulation of neoplastic invasion and metastasis. Against this background, we now wish to report on the design, synthesis, and kinetic testing of a series of dipeptide proline diphenyl phosphonates, against DPP-IV and seprase. The most potent inhibitor of DPP-IV and seprase was found to be Gly-ProP(OPh)2, which exhibited overall second-order rate constants of inactivation of 5.24 x 105 M-1 min-1 and 1.06 x 104 M-1 min-1 against DPP-IV and seprase, respectively. Both proteases displayed differing profiles of susceptibility towards the other members of the series of inhibitors synthesised. In addition, Gly-ProP(OPh)2 and Tyr-ProP(OPh)2 were found to exert a considerable, dose-dependent anti-invasive effect on the LOX melanoma cell line, in vitro.

Invasive growth and topoisomerase-switch induced by tumorous extracellular matrix in osteosarcoma cell culture

Osteosarcoma cells are capable of extracellular matrix (ECM) synthesis. The ability of ECM to trigger the proliferation of a novel osteosarcoma cell line (OSCORT) was tested in this study in relation to a known tumor ECM, isolated from Engelbreth-Holm-Swarm (EHS) sarcoma (EHS-ECM). OSCORT was grown in monolayer, in EHS-ECM and in ECM deposited by the cells (OSCORT-ECM). Both EHS-ECM and OSCORT-ECM increased the proliferation and migration of OSCORT cells. Among the ECM biopolymers, heparan sulfate proteoglycan (HSPG) and fibronectin enhanced invasive growth, collagen type IV reduced it, while laminin had no effect. Among the ECM components HSPG and collagen IV increased both the synthesis and activation of collagenase type IV, and all the ECM components substantially increased beta1 integrin levels in the cells. The majority of ECM biopolymers decreased the level of topoisomerase I (except laminin) and elevated topoisomerase II (except fibronectin) in OSCORT. The switch in the ratio between the activities of topoisomerases I and II was mainly due to HSPG. The HSPG synthesized by OSCORT cells is described as agrin, which is a novel finding. The present study showed that HSPG (agrin) showed the most remarkable stimulatory action on the growth and migration of OSCORT cells. HSPG-induced topoisomerase II-induction deserves further experimentation, to discover its relevance to tumor progression.

Hydroxamate-based peptide inhibitors of matrix metalloprotease 2

There is major interest in designing inhibitors for matrix metalloproteinase 2 (MMP-2, gelatinase A) since this enzyme is known to be involved in pathological processes such as tumor invasion or rheumatoid arthritis. The majority of MMP-2 inhibitor candidate drugs block the active site of MMP-2 by binding to its catalytic Zn2+ ion through a chelating (hydroxamate, sulphonate etc.) group. Despite the general interest in designing MMP-2 inhibitors, the results with many of the drug candidates were disappointing, their failure was usually explained by cross-reactions with other MMPs. One way to enhance MMP-2 selectivity is to design inhibitors that interact with both the active site and exosites such as the fibronectin type II (FN2) domains of the enzyme. In the present work, we have examined the inhibitory potential and MMP-2 selectivity of hydroxamates of three groups of peptides known to bind to the collagen-binding FN2 domains of MMP-2. The first type of peptides consisted of collagen-like (Pro-Pro-Gly)(n) repeats, peptides of the second group were identified from a random 15-mer phage display library based on their binding to immobilized FN2 domains of MMP-2. A hydroxamate of peptide p33-42, known to bind to the third FN2 domain of MMP-2 has also been tested. Our studies have shown that these compounds inhibited MMP-2 with IC50 values of 10-100 microM. The fact that their inhibitory potential was nearly identical for MMP-2del, a recombinant version of MMP-2 that lacks the FN2 domains, suggests that inhibition is not mediated by their binding to FN2 domains. It seems likely that the failure to exploit interaction with the FN2 domains is due to the fact that the FN2 domains and the catalytic domain of MMP-2 tumble independently, therefore only a tiny fraction of the conformational isomers can bind peptide hydroxamates via both the active site and the FN2 domain(s).

Structural and kinetic analysis of the substrate specificity of human fibroblast activation protein alpha

Fibroblast activation protein alpha (FAPalpha) is highly expressed in epithelial cancers and has been implicated in extracellular matrix remodeling, tumor growth, and metastasis. We present the first high resolution structure for the apoenzyme as well as kinetic data toward small dipeptide substrates. FAPalpha exhibits a dipeptidyl peptidase IV (DPPIV)-like fold, featuring an alpha/beta-hydrolase domain and an eight-bladed beta-propeller domain. Known DPPIV dipeptides are cleaved by FAPalpha with an approximately 100-fold decrease in catalytic efficiency compared with DPPIV. Moreover, FAPalpha, but not DPPIV, possesses endopeptidase activity toward N-terminal benzyloxycarbonyl (Z)-blocked peptides. Comparison of the crystal structures of FAPalpha and DPPIV revealed one major difference in the vicinity of the Glu motif (Glu(203)-Glu(204) for FAPalpha; Glu(205)-Glu(206) for DPPIV) within the active site of the enzyme. Ala(657) in FAPalpha, instead of Asp(663) as in DP-PIV, reduces the acidity in this pocket, and this change could explain the lower affinity for N-terminal amines by FAPalpha. This hypothesis was tested by kinetic analysis of the mutant FAPalpha/A657D, which shows on average an approximately 60-fold increase in the catalytic efficiency, as measured by k(cat)/K(m), for the cleavage of dipeptide substrates. Furthermore, the catalytic efficiency of the mutant is reduced by approximately 350-fold for cleavage of Z-Gly-Pro-7-amino-4-methylcoumarin. Our data provide a clear understanding of the molecular determinants responsible for the substrate specificity and endopeptidase activity of FAPalpha.

Furin Directly Cleaves proMMP-2 in the trans-Golgi Network Resulting in a Nonfunctioning Proteinase

Proprotein convertases play an important role in tumorigenesis and invasiveness. Here, we report that a dibasic amino acid convertase, furin, directly cleaves proMMP-2 within the trans-Golgi network leading to an inactive form of matrix metalloproteinase-2 (MMP-2). Co-transfection of COS-1 cells with both proMMP-2 and furin cDNAs resulted in the cleavage of the N-terminal propeptide of proMMP-2. The molecular mass of cleaved MMP-2 (63 kDa), detected in both cell lysates and conditioned medium, is between the intermediate and fully activated forms of MMP-2 induced by membrane type 1-MMP. Furin-cleaved MMP-2 does not possess proteolytic activity as examined in a cell-free assay. Treatment of transfected cells with a furin inhibitor resulted in a dose-dependent inhibition of proMMP-2 cleavage; recombinant tissue inhibitor of metalloproteinase-2, which binds to the active site of membrane type 1-MMP, had no inhibitory effect. Site-directed mutagenesis of amino acids in the furin consensus recognition motif of proMMP-2(R69KPR72) prevented propeptide cleavage, thereby identifying the scissile bond and characterizing the basic amino acids required for cleavage. Other experimental observations were consistent with intracellular furin cleavage of proMMP-2 in the trans-Golgi network. The furin cleavage site in other proMMPs was examined. MMP-3, which contains the RXXR furin consensus sequence, was cleaved in furin co-transfected cells, whereas MMP-1, which lacks an RXXR consensus sequence, was not cleaved. In conclusion, we report the novel observation that furin can directly cleave the RXXR amino acid sequence in the propeptide domain of proMMP-2 leading to inactivation of the enzyme.

Enzyme production-based approach for determining the functions of microorganisms within a community

The functions of specific microorganisms in a microbial community were investigated during the composting process. Cerasibacillus quisquiliarum strain BLx(T) and Bacillus thermoamylovorans strain BTa were isolated and characterized in our previous studies based on their dominance in the composting system. Strain BLx(T) degrades gelatin, while strain BTa degrades starch. We hypothesized that these strains play roles in gelatinase and amylase production, respectively. The relationship between changes in the abundance ratios of each strain and those of each enzyme activity during the composting process was examined to address this hypothesis. The increase in gelatinase activity in the compost followed a dramatic increase in the abundance ratio of strain BLx(T). Zymograph analysis demonstrated that the pattern of active gelatinase bands from strain BLx(T) was similar to that from the compost. Gelatinases from both BLx(T) and compost were partially purified and compared. Homologous N-terminal amino acid sequences were found in one of the gelatinases from strain BLx(T) and that of compost. These results indicate strain BLx(T) produces gelatinases during the composting process. Meanwhile, the increase in the abundance ratio of strain BTa was not concurrent with that of amylase activity in the compost. Moreover, the amylase activity pattern of strain BTa on the zymogram was different from that of the compost sample. These results imply that strain BTa may not produce amylases during the composting process. To our knowledge, this is the first report demonstrating that the function of a specific microorganism is directly linked to a function in the community, as determined by culture-independent and enzyme-level approaches.

Selective involvement of TIMP-2 in the second activational cleavage of pro-MMP-2: refinement of the pro-MMP-2 activation mechanism

A tissue inhibitor of metalloproteinases-2 (TIMP-2)-independent mechanism for generating the first activational cleavage of pro-matrix metalloproteinase-2 (MMP-2) was identified in membrane type-1 MMP (MT1-MMP)-transfected MCF-7 cells and confirmed in TIMP-2-deficient fibroblasts. In contrast, the second MMP-2-activational step was found to be TIMP-2 dependent in both systems. MMP-2 hemopexin C-terminal domain was found to be critical for the first step processing, confirming a need for membrane tethering. We propose that the intermediate species of MMP-2 forms the well-established trimolecular complex (MT1-MMP/TIMP-2/MMP-2) for further TIMP-2-dependent autocatalytic cleavage to the fully active species. This alternate mechanism may supplement the traditional TIMP-2-mediated first step mechanism.

Seprase, a membrane-bound protease, alleviates the serum growth requirement of human breast cancer cells

Seprase is a cell surface serine protease that is expressed to high levels by infiltrating ductal carcinomas of the breast but its function in malignancy is unknown. MDA-MB-435 (WT435) and MDA-MB-436 (WT436) human breast cancer cells express high levels of seprase as do the carcinoma cells in tumors of human breast cancer patients. To investigate its role in the pathobiology of breast cancer, seprase was specifically reduced in WT436 and WT435 cells by expression of antisense seprase cDNA. Decreased expression of seprase was confirmed in the antisense transfectants by zymography, immunoblotting, and fluorescence-activated cell sorting of cells labeled with antibody to seprase. Control-transfectants continued to express high levels of seprase. Seprase-deficient cells growing on type I collagen gels reveal a markedly different morphology than the parental or control-transfected cells that express high levels of seprase. The seprase-deficient cells grow in islands and aggregates of tightly attached cells while cells with high seprase expression grow as groups of separate individual cells. Interestingly, the aggregated growth of the seprase-deficient cells was not correlated with increased expression of E-cadherin. Seprase-deficient breast cancer cells also exhibit altered growth properties. Seprase-deficient cells and those with high seprase levels proliferate in serum-containing media. However, in serum-free medium seprase-deficient cells proliferate much more slowly than their seprase-expressing counterparts. These findings indicate that seprase promotes the aberrant growth of breast cancer cells by reducing their dependence on exogenous growth factors. Seprase may contribute to the pathogenesis of breast cancer by promoting growth of the primary tumor and by facilitating the growth of breast cancer cells in metastases at other sites of the body.

Identification of a negatively charged peptide motif within the catalytic domain of progelatinases that mediates binding to leukocyte beta 2 integrins

The alpha M beta 2 integrin of leukocytes can bind a variety of ligands. We screened phage display libraries to isolate peptides that bind to the alpha M I domain, the principal ligand binding site of the integrin. Only one peptide motif, (D/E)(D/E)(G/L)W, was obtained with this approach despite the known ligand binding promiscuity of the I domain. Interestingly, such negatively charged sequences are present in many known beta 2 integrin ligands and also in the catalytic domain of matrix metalloproteinases (MMPs). We show that purified beta 2 integrins bind to pro-MMP-2 and pro-MMP-9 gelatinases and that that the negatively charged sequence of the MMP catalytic domain is an active beta 2 integrin-binding site. Furthermore, a synthetic DDGW-containing phage display peptide inhibited the ability of beta 2 integrin to bind progelatinases but did not inhibit the binding of cell adhesion-mediating substrates such as intercellular adhesion molecule-1, fibrinogen, or an LLG-containing peptide. Immunoprecipitation and cell surface labeling demonstrated complexes of pro-MMP-9 with both the alpha M beta 2 and alpha L beta 2 integrins in leukocytes, and pro-MMP-9 colocalized with alpha M beta 2 in cell surface protrusions. The DDGW peptide and the gelatinase-specific inhibitor peptide CTTHWGFTLC blocked beta 2 integrin-dependent leukocyte migration in a transwell assay. These results suggest that leukocytes may move in a progelatinase-beta 2 integrin complex-dependent manner.

Human mast cell beta-tryptase is a gelatinase

Remodeling of extracellular matrix is an important component in a variety of inflammatory disorders as well as in normal physiological processes such as wound healing and angiogenesis. Previous investigations have identified the various matrix metalloproteases, e.g., gelatinases A and B, as key players in the degradation of extracellular matrix under such conditions. Here we show that an additional enzyme, human mast cell beta-tryptase, has potent gelatin-degrading properties, indicating a potential contribution of this protease to matrix degradation. Human beta-tryptase was shown to degrade gelatin both in solution and during gelatin zymographic analysis. Further, beta-tryptase was shown to degrade partially denatured collagen type I. beta-Tryptase bound strongly to gelatin, forming high molecular weight complexes that were stable during SDS-PAGE. Mast cells store large amounts of preformed, active tryptase in their secretory granules. Considering the location of mast cells in connective tissues and the recently recognized role of mast cells in disorders in which connective tissue degradation is a key event, e.g., rheumatoid arthritis, it is thus likely that tryptase may contribute to extracellular matrix-degrading processes in vivo.

Epigallocatechin-3-gallate binding to MMP-2 inhibits gelatinolytic activity without influencing the attachment to extracellular matrix proteins but enhances MMP-2 binding to TIMP-2

Although epigallocatechin-3-gallate (EGCg), a dominant component of green tea catechins, has been demonstrated to have anti-gelatinase properties, the molecular mechanisms by which EGCg blocks gelatinolytic activities remain unknown. We investigated whether EGCg may affect matrix metalloproteinase-2 (MMP-2) binding to native and denatured-type I collagen, and binding to the tissue inhibitor of metalloproteinase-2 (TIMP-2). Here, we report that EGCg forms a reversible complex with MMP-2, resulting in the inhibition of gelatinolytic activity of MMP-2. EGCg had no effect on the MMP-2 binding to immobilized native and denatured-type I collagen, but significantly enhanced pro- and activated MMP-2 binding to TIMP-2, as assessed by immunoprecipitation. These findings provide a new understanding of the molecular mechanisms underlying the inhibitory effect of EGCg on the gelatinolytic activity of MMP-2.

Production of industrially important enzymes by some actinomycetes producing antifungal compounds

Seventeen strains of actinomycetes antagonistic to yeast and moulds have been tested for their ability to produce amylase, lipase, gelatinase and caseinase using solid media containing starch, Tween-20, gelatin and skimmed milk, respectively, Enzyme producing potential of test strains is expressed in ternis of relative enzyme activity (REA). Actinomycetes strain Streptomyces somaliensis GS 1242 and Streptomyces sampsonii GS 1322 showed higher amylase production (REA 6.5) while maximum lipase activity was noted in Streptomyces strain SAP 1089 (REA 7.0). Gelatinase activity was noted higher is S. sampsonii GS 1322 (REA 9.6) and S. somaliensis GS 1242 (REA 8.8). Enzyme producing potential of these strains has been discussed in terms of their industrial significance.

Regulation of fibroblast migration on collagenous matrix by a cell surface peptidase complex

The invasion of migratory cells through connective tissues involves metallo- and serine types of cell surface proteases. We show that formation of a novel protease complex, consisting of the membrane-bound prolyl peptidases seprase and dipeptidyl peptidase IV (DPPIV), at invadopodia of migratory fibroblasts is a prerequisite for cell invasion and migration on a collagenous matrix. Seprase and DPPIV form a complex on the cell surface that elicits both gelatin binding and gelatinase activities localized at invadopodia of cells migrating on collagenous fibers. The protease complex participates in the binding to gelatin and localized gelatin degradation, cellular migration, and monolayer wound closure. Serine protease inhibitors can block the gelatinase activity and the localized gelatin degradation by cells. Antibodies to the gelatin-binding domain of DPPIV reduce the cellular abilities of the proteases to degrade gelatin but do not affect cellular adhesion or spreading on type I collagen. Furthermore, expression of the seprase-DPPIV complex is restricted to migratory cells involved in wound closure in vitro and in connective tissue cells during closure of gingival wounds but not in differentiated tissue cells. Thus, we have identified cell surface proteolytic activities, which are non-metalloproteases, seprase and DPPIV, that are responsible for the tissue-invasive phenotype.

[Gelatinase activity of protein fractions obtained by electrophoresis in polyacrylamide gel]

The modification of a method of determination gelatinolytic activity in protein fractions obtained by one and two-dimensional polyacrylamide gel electrophoresis is presented. The presence of a fraction 115-125 kD among human proteins of cortex matter and glomerulus of kidney and also in myocardium having gelatinolytic activity is demonstrated.

Nitric oxide inhibition increases aortic wall matrix metalloproteinase-9 expression

OBJECTIVE

Nitric oxide (NO) may mediate vessel wall remodeling by regulating expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). This study tested the hypothesis that nitric oxide synthase (NOS) inhibition in whole aortic wall causes increases in cytokine-stimulated MMP and TIMP expression.

METHODS

Cultured infrarenal aortic segments from Sprague-Dawley rats were exposed to increasing concentrations (0, 0.1, 0.5, 1, and 5 mM; n = 6 per concentration) of N(G)-monomethyl-l-arginine (L-NMMA), a known inhibitor of NOS. This was in the presence of 2 ng/ml of interleukin-1beta, a known inducer of NOS, MMP, and TIMP expression. Media nitrate and nitrite (NO(x)) were measured at 72 h using the Saville method. Media MMP activity was measured using gelatin zymography. MMP-2 and -9 protein and mRNA levels were determined by Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR). TIMP activity and mRNA levels were evaluated by reverse zymography and RT-PCR. Data were analyzed using ANOVA.

RESULTS

Increasing concentrations of L-NMMA produced a dose-dependent decrease in NO(x) (2214 +/- 405 to 347 +/- 37 ng/mg, P < 0.001). Zymography demonstrated a dose-dependent increase in 92-kDa MMP (pro-MMP-9) activity (P < 0.001) with corresponding increases in pro-MMP-9 protein (P = 0.03) and mRNA levels (P = 0.004). While there was a dose-dependent increase in 72-kDa MMP (pro-MMP-2) activity (P = 0.001), pro-MMP-2 protein and mRNA levels were unchanged. Reverse zymography demonstrated a dose-dependent increase in 29-kDa TIMP-1 activity (P = 0.01), but there was no change in TIMP-1 mRNA levels.

CONCLUSIONS

NOS inhibition in ex vivo aortic tissue causes a dose-dependent increase in MMP-9 expression and activity. It is speculated that deficiencies of NO in vivo alter MMP and TIMP homeostasis, favoring matrix degradation.

Design, synthesis, and characterization of potent, slow-binding inhibitors that are selective for gelatinases

Gelatinases have been shown to play a key role in angiogenesis and tumor metastasis. Small molecular weight synthetic inhibitors for these enzymes are highly sought for potential use as anti-metastatic agents. Virtually all of the known inhibitors of matrix metalloproteinases (MMPs) are broad spectrum. We report herein the synthesis and kinetic characterization of two compounds, 4-(4-phenoxyphenylsulfonyl)butane-1,2-dithiol (compound 1) and 5-(4-phenoxyphenylsulfonyl)pentane-1,2-dithiol (compound 2), that are potent and selective gelatinase inhibitors. These compounds are slow, tight-binding inhibitors of gelatinases (MMP-2 and MMP-9) with K(i) values in the nanomolar range. In contrast, competitive inhibition of the catalytic domain of membrane-type 1 metalloproteinase (MMP-14(cat)) with comparable K(i) values (K(i) approximately 200 nm) was observed. Binding to stromelysin (MMP-3) was substantially weaker, with K(i) values in the micromolar range (K(i) approximately 10 microm). No binding to matrilysin (MMP-7) and collagenase 1 (MMP-1) was detected at inhibitor concentrations up to 60 microm. We have previously shown that synthetic MMP inhibitors work synergistically with TIMP-2 in the promotion of pro-MMP-2 activation by MT1-MMP in a process that depends on the affinity of the inhibitor toward MT1-MMP. It is shown herein that the dithiols are significantly less efficient (>100-fold) than marimastat, a broad-spectrum MMP inhibitor, in enhancing pro-MMP-2 activation in cells infected to express MT1-MMP, consistent with the lower affinity of the dithiols toward MT1-MMP. Thus, in contrast to broad-spectrum MMP inhibitors, the dithiols are less likely to promote MT1-MMP-dependent pro-MMP-2 activation in the presence of TIMP-2, while maintaining their ability to inhibit active MMP-2 effectively.

Homophilic complex formation of MT1-MMP facilitates proMMP-2 activation on the cell surface and promotes tumor cell invasion

Activation of proMMP-2 by MT1-MMP is considered to be a critical event in cancer cell invasion. In the activation step, TIMP-2 bound to MT1-MMP on the cell surface acts as a receptor for proMMP-2. Subsequently, adjacent TIMP-2-free MT1-MMP activates the proMMP-2 in the ternary complex. In this study, we demonstrate that MT1-MMP forms a homophilic complex through the hemopexin-like (PEX) domain that acts as a mechanism to keep MT1-MMP molecules close together to facilitate proMMP-2 activation. Deletion of the PEX domain in MT1-MMP, or swapping the domain with the one derived from MT4-MMP, abolished the ability to activate proMMP-2 on the cell surface without affecting the proteolytic activities. In addition, expression of the mutant MT1-MMP lacking the catalytic domain (MT1PEX-F) efficiently inhibited complex formation of the full-length enzymes and activation of pro MMP-2. Furthermore, expression of MT1PEX-F inhibited proMMP-2 activation and Matrigel invasion activity of invasive human fibrosarcoma HT1080 cells. These findings elucidate a new function of the PEX domain: regulating MT1-MMP activity on the cell surface, which accelerates cellular invasiveness in the tissue.

Activation of progelatinase A by mammalian legumain, a recently discovered cysteine proteinase

The activation of progelatinase A to gelatinase A requires cleavage of an asparaginyl bond to form the N-terminus of the mature enzyme. We have asked whether the activation can be mediated by legumain, the recently discovered lysosomal cysteine proteinase that is specific for hydrolysis of asparaginyl bonds. Addition of purified legumain to the concentrated conditioned medium from HT1080 cell culture that contained both progelatinases A and B caused the conversion of the 72 kDa progelatinase A to the 62 kDa form. The progelatinase B in the medium was unaffected. Incubation of recombinant progelatinase A with legumain resulted in an almost instantaneous activation as judged by the fluorometric assay with a specific gelatinase A substrate, Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. Legumain also activated progelatinase A when it was in complex with TIMP-2. Zymographic analysis and N-terminal sequencing revealed that legumain cleaved the 72 kDa progelatinase A at the bonds between Asn109-Tyr110 or Asn111-Phe112 to produce the 62 kDa mature enzyme, and that further cleavage at Asn430 also occurred to generate a 36 kDa active form. More 62 kDa gelatinase A was detected in cultures of C13 cells that over-expressed legumain than in those of the control HEK293 cells. We conclude that legumain is clearly capable of processing progelatinase A to the active enzyme in vitro and in cultured cells.

Tissue inhibitors of metalloproteinases: evolution, structure and function

The matrix metalloproteinases (MMPs) play a key role in the normal physiology of connective tissue during development, morphogenesis and wound healing, but their unregulated activity has been implicated in numerous disease processes including arthritis, tumor cell metastasis and atherosclerosis. An important mechanism for the regulation of the activity of MMPs is via binding to a family of homologous proteins referred to as the tissue inhibitors of metalloproteinases (TIMP-1 to TIMP-4). The two-domain TIMPs are of relatively small size, yet have been found to exhibit several biochemical and physiological/biological functions, including inhibition of active MMPs, proMMP activation, cell growth promotion, matrix binding, inhibition of angiogenesis and the induction of apoptosis. Mutations in TIMP-3 are the cause of Sorsby's fundus dystrophy in humans, a disease that results in early onset macular degeneration. This review highlights the evolution of TIMPs, the recently elucidated high-resolution structures of TIMPs and their complexes with metalloproteinases, and the results of mutational and other studies of structure-function relationships that have enhanced our understanding of the mechanism and specificity of the inhibition of MMPs by TIMPs. Several intriguing questions, such as the basis of the multiple biological functions of TIMPs, the kinetics of TIMP-MMP interactions and the differences in binding in some TIMP-metalloproteinase pairs are discussed which, though not fully resolved, serve to illustrate the kind of issues that are important for a full understanding of the interactions between families of molecules.

Function of alpha3beta1-tetraspanin protein complexes in tumor cell invasion. Evidence for the role of the complexes in production of matrix metalloproteinase 2 (MMP-2)

Tumor cell migration through the three- dimensional extracellular matrix (ECM) environment is an important part of the metastatic process. We have analyzed a role played by the integrin-tetraspanin protein complexes in invasive migration by culturing MDA-MB-231 cells within Matrigel. Using time-lapse video recording, we demonstrated that the Matrigel-embedded cells remain round and exhibit only limited ability for migration by extending short, highly dynamic pseudopodia. The alpha3beta1-tetraspanin protein complexes were clustered on the thin microvilli-like protrusions extending from both the main cell body and pseudopodia. Ligation of the alpha3beta1-tetraspanin protein complexes with monoclonal antibodies specifically stimulates production of matrix metalloproteinase 2 (MMP-2) and induces formation of long invasive protrusions within Matrigel. Accordingly, treatment with the monoclonal antibodies to various tetraspanin proteins and to the alpha3 integrin subunit increases invasive potential of the MDA-MB-231 cells in the Matrigel-penetration assay. A specific inhibitor of phosphoinositide 3-kinase (PI3K), LY294002, negated the effect of the monoclonal antibodies on the morphology of the Matrigel-embedded cells and on production of MMP-2. Interestingly, broad-spectrum inhibitors of protein tyrosine kinases (genistein) and protein tyrosine phosphatases (orthovanadate), and actin filament stabilizing compound (jasplakinolide), also block protrusive activity of the Matrigel-embedded cells but have no effect on the production of MMP-2. These results indicate that alpha3beta1-tetraspanin protein complexes may control invasive migration of tumor cells by using at least two PI3K-dependent signaling mechanisms: through rearrangement of the actin cytoskeleton and by modulating the MMP-2 production.

The 105-kDa protein component of Bacillus cereus non-haemolytic enterotoxin (Nhe) is a metalloprotease with gelatinolytic and collagenolytic activity

A sequence of 91 amino acids residues, probably starting from the N-terminal of the mature protein, was determined for the 105-kDa protein of the non-haemolytic enterotoxin of Bacillus cereus. The last part of this sequence was similar to parts of the N-terminal portions of two collagenases of Clostridium histolyticum and Clostridium perfringens. Zymography, with intact collagen fibril and gelatin as substrates, showed that the 105-kDa protein had collagenolytic and gelatinolytic activity. The 105-kDa protein also showed activity against a typical collagenase substrate, azocoll, and was inhibited by EDTA and 1,10-phenanthroline. We conclude that the 105-kDa protein is a collagenase.

Structure of human pro-matrix metalloproteinase-2: activation mechanism revealed

Matrix metalloproteinases (MMPs) catalyze extracellular matrix degradation. Control of their activity is a promising target for therapy of diseases characterized by abnormal connective tissue turnover. MMPs are expressed as latent proenzymes that are activated by proteolytic cleavage that triggers a conformational change in the propeptide (cysteine switch). The structure of proMMP-2 reveals how the propeptide shields the catalytic cleft and that the cysteine switch may operate through cleavage of loops essential for propeptide stability.

Homology modeling of gelatinase catalytic domains and docking simulations of novel sulfonamide inhibitors

Three-dimensional models for the catalytic domain of gelatinases (MMP-9 and -2) have been constructed based on the X-ray crystal structure of MMP-3. Conformations of the loop segment which forms the bottom half of the S1' subsite but shows conformational diversity among the crystal structures of other MMPs have been explored by simulated annealing of each gelatinase model complexed with two highly potent "probe" inhibitors. Representative catalytic domain models have been selected for each gelatinase from the set of generated conformations based on shape complementarity of the loop to the probe inhibitors. The single model selected for MMP-9 was utilized to explain the structure-activity relationship of our novel sulfonamide inhibitors. Molecular dynamics (MD) simulations of the complex models revealed important features of the binding mechanism of our inhibitors: (i) the ligand carboxylate group coordinating to the catalytic zinc ion and hydrogen bonding to the Glu219 side chain, (ii) one of the sulfonyl oxygens forming hydrogen bonds with the main chain NHs (Leu181 and Ala182), (iii) the sulfonyl substituent making extensive hydrophobic contact with the S1' subsite. The gauche conformation exclusively adopted by the sulfonamide C-N-S-C torsion plays an important role in achieving the third binding feature by properly directing the substituent into the S1' subsite. Improvement of the inhibitory activity according to straight elongation of the sulfonyl substituent was attributed to an increase of the hydrophobic contact between the substituent and the S1' subsite. Structural modifications which alter the straight shape of the substituent lead to deterioration of the activity. On the other hand, the two candidate models selected for MMP-2 differ in the bottom shape of the S1' subsite: one with a channel-like subsite and the other with a pocket-like subsite resembling that of the MMP-9 model. The bottom shape was experimentally probed by chemical synthesis of inhibitors having elongated sulfonyl substituents whose terminal alkyl groups were shown by MD simulations to protrude from the S1' subsite bottom into the solvent. Gelatinase assays of these inhibitors showed that elongation of the substituent significantly reduces activity against MMP-9 while retaining activity against MMP-2, consequently increasing the selectivity between MMP-2 and -9. The results confirm that MMP-9 has a pocket-like S1' subsite with a floorboard and MMP-2 has a channel-like S1' subsite.

Human tissue inhibitor of metalloproteinases 3 interacts with both the N- and C-terminal domains of gelatinases A and B. Regulation by polyanions

We compared the association constants of tissue inhibitor of metalloproteinases (TIMP)-3 with various matrix metalloproteinases with those for TIMP-1 and TIMP-2 using a continuous assay. TIMP-3 behaved more like TIMP-2 than TIMP-1, showing rapid association with gelatinases A and B. Experiments with the N-terminal domain of gelatinase A, the isolated C-terminal domain, or an inactive progelatinase A mutant showed that the hemopexin domain of gelatinase A makes an important contribution to the interaction with TIMP-3. The exchange of portions of the gelatinase A hemopexin domain with that of stromelysin revealed that residues 568-631 of gelatinase A were required for rapid association with TIMP-3. The N-terminal domain of gelatinase B alone also showed slower association with TIMP-3, again implying significant C-domain interactions. The isolation of complexes between TIMP-3 and progelatinases A and B on gelatin-agarose demonstrated that TIMP-3 binds to both proenzymes. We analyzed the effect of various polyanions on the inhibitory activity of TIMP-3 in our soluble assay. The association rate was increased by dextran sulfate, heparin, and heparan sulfate, but not by dermatan sulfate or hyaluronic acid. Because TIMP-3 is sequestered in the extracellular matrix, the presence of certain heparan sulfate proteoglycans could enhance its inhibitory capacity.

Gene duplication and multiplicity of collagenases in Clostridium histolyticum

Clostridium histolyticum collagenase contains a number of different active components. Previously we have shown that colH encodes a 116-kDa collagenase (ColH) and a 98-kDa gelatinase. We purified a different 116-kDa collagenase (ColG) from the culture supernatant and sequenced its gene (colG). We also identified four other gelatinases (105, 82, 78, and 67 kDa) and determined their N-terminal amino acid sequences, all of which coincided with that of either ColG or ColH. Hybridization experiments showed that each gene is present in a single copy and each gene is transcribed into a single mRNA. These results suggest that all the gelatinases are produced from the respective full-length collagenase by the proteolytic removal of C-terminal fragments. The substrate specificities of the enzymes suggest that colG and colH encode class I and class II enzymes, respectively. Analysis of their DNA locations by pulsed-field gel electrophoresis and nucleotide sequencing of their surrounding regions revealed that the two genes are located in different sites on the chromosome. C. histolyticum colG is more similar to C. perfringens colA than to colH in terms of domain structure. Both colG and colA have a homologous gene, mscL, at their 3' ends. These results suggest that gene duplication and segment duplication have occurred in an ancestor cell common to C. histolyticum and C. perfringens and that further divergence of the parent gene produced colG and colA.

Calcium-protein interactions in the extracellular environment: calcium binding, activation, and immunolocalization of a collagenase/gelatinase activity expressed in the sea urchin embryo

We have purified and characterized a collagenase/gelatinase activity expressed during sea urchin embryonic development. The native molecular mass was determined to be 160 kDa, while gelatin substrate gel zymography revealed an active species of 41 kDa, suggesting that the native enzyme is a tetramer of active subunits. Incubation in the presence of EGTA resulted in nearly complete loss of activity and this effect could be reversed by calcium. Calcium-induced reactivation appeared to be cooperative and occurred with an apparent kd value of 3.7 mM. Two modes of calcium binding to the 41-kDa subunit were detected; up to 80 moles of calcium bound with a kd value of 0.5 mM, while an additional 120 moles bound with a kd value of 5 mM. Amino acid analysis revealed a carboxy plus carboxyamide content of 24.3 mol/100 mol, indicating the availability of substantial numbers of weak Ca2+-binding sites. Calcium binding did not result in either secondary or quaternary structural changes in the collagenase/gelatinase, suggesting that Ca2+ may facilitate activation through directly mediating the binding of substrate to the enzyme. The collagenase/gelatinase activity was detected in blastocoelic fluid and in the hyalin fraction dissociated from 1-h-old embryos. Immunolocalization studies revealed two storage compartments in the egg; cortical granules and small granules/vesicles dispersed throughout the cytoplasm. After fertilization, the antigen was detected in both the apical and basal extracellular matrices, the hyaline layer, and basal lamina, respectively.

Identification and partial characterization of three calcium- and zinc-independent gelatinases constitutively present in human circulation

Three constitutive gelatinases in human plasma were identified and characterized relative to known matrix metalloproteinase (MMP) gelatinases: MMP-2 (fibroblast 72-kDa) and MMP-9 (neutrophil 92-, 130-, and 225-kDa). Substrate gel electrophoresis (gelatin zymography) revealed an apparent Mw of 78-, 82-, and 89-kDa for these gelatinases. Densitometry revealed that MMP-9 and MMP-2 were highly calcium sensitive requiring 50-150 microM and 500 microM calcium for half-maximal activity, respectively. Of the new gelatinases, only the 89-kDa form demonstrated slight calcium activation. The three gelatinases were unaffected by known MMP inhibitors: EDTA (5 mM), 1,10-phenanthroline (2 mM), and pepstatin (18 microM). Serine and thiol protease inhibitors (leupeptin, aprotinin, PMSF, TLCK, TPCK, antichymostatin, antipain) were also ineffective. Solution-phase IEF revealed that the 78- and 82-kDa forms focused at neutral pI 6.72-7.95 whereas the 89-kDa focused at an acidic pI 4.89-5.18 (similar to neutrophil and fibroblast forms). The data indicate that these gelatinases are not MMPs or partially activated MMPs. Their role in normal and pathological conditions is not known.

Remodeling of collagen matrix by human tumor cells requires activation and cell surface association of matrix metalloproteinase-2

We assessed the functional significance of tumor cell-associated matrix metalloproteinase (MMP)-2 in extracellular matrix remodeling compared with that of the soluble enzyme by evaluating the contraction of three-dimensional collagen lattices by human glioma U251.3 and fibrosarcoma HT-1080 cell lines. In this model, the constitutive synthesis and activation of the MMP-2 proenzyme were modulated by stable transfections of tumor cells with cDNA encoding membrane type 1-MMP (MT1-MMP). The efficiency of transfected cells in contracting collagen lattices was shown to be dependent on the MT1-MMP-mediated activation of MMP-2 accompanied by cell surface association of activated MMP-2, on the cell-matrix interactions controlled by collagen-specific integrins, and on the integrity of actin and microtubule cytoskeletons. Each one of these mechanisms was essential but was not sufficient by itself in accomplishing gel contraction by MT1-MMP-transfected cells. Both MMP-2 activation and gel contraction by transfected glioma cells were inhibited by tissue inhibitor of metalloproteinase (TIMP)-2 and the recombinant COOH-terminal domain of MMP-2. However, the kinetics and mechanisms of their inhibitory effects were different, because TIMP-2 and the COOH-terminal domain of MMP-2 preferentially inhibited the MT1-MMP-dependent and autocatalytic steps of MMP-2 activation, respectively. By contrast, TIMP-1, an efficient inhibitor of soluble MMP-2 activity, failed to affect gel contraction. In addition, soluble MMP-2 activated by either organomercurials or cells was not able to induce the contraction of collagen lattices when added to transfected cells. Therefore, soluble activated MMP-2, sensitive to TIMP-1 inhibition, does not mediate collagen gel contraction by tumor cells, whereas the activity of cell surface-associated MMP-2 plays a critical role in remodeling of the extracellular matrix in vitro. These mechanisms of functional and spatial regulation of MMP-2 may also be applicable to different aspects of tissue reorganization in vivo, including cell migration and invasion, angiogenesis, and wound healing.

The involvement of the fibronectin type II-like modules of human gelatinase A in cell surface localization and activation

Recombinant collagen-binding domain (rCBD) comprising the three fibronectin type II-like modules of human gelatinase A was found to compete the zymogen form of this matrix metalloproteinase from the cell surface of normal human fibroblasts in culture. Upon concanavalin A treatment of cells, the induced cellular activation of gelatinase A was markedly elevated in the presence of the rCBD. Therefore, the mechanistic aspects of gelatinase A binding to cells by this domain were further studied using cell attachment assays. Fibroblasts attached to rCBD-coated microplate wells in a manner that was inhibited by soluble rCBD, blocking antibodies to the beta1-integrin subunit but not the alpha2-integrin subunit, and bacterial collagenase treatment. Addition of soluble collagen rescued the attachment of collagenase-treated cells to the rCBD. As a probe on ligand blots of octyl-beta-D-thioglucopyranoside-solubilized cell membrane extracts, the rCBD bound 140- and 160-kDa protein bands. Their identities were likely procollagen chains being both bacterial collagenase-sensitive and also converted upon pepsin digestion to 112- and 126-kDa bands that co-migrated with collagen alpha1(I) and alpha2(I) chains. A rCBD mutant protein (Lys263 --> Ala) with reduced collagen affinity showed less cell attachment, whereas a heparin-binding deficient mutant (Lys357 --> Ala), heparinase treatment, or heparin addition did not alter attachment. Thus, a cell-binding mechanism for gelatinase A is revealed that does not involve the hemopexin COOH domain. Instead, an attachment complex comprising gelatinase A-native type I collagen-beta1-integrin forms as a result of interactions involving the collagen-binding domain of the enzyme. Moreover, this distinct pool of cell collagen-bound proenzyme appears recalcitrant to cellular activation.

60K gelatinase involved in mammary gland involution is regulated by beta-oestradiol

Cell matrix interactions are critical in the expression and maintenance of differentiated functions in mammary gland. Matrix metalloproteinases (MMPs), by acting on different matrix components, contribute to the remodelling of extracellular matrix. Of the three major gelatinases found in rat mammary gland at different stages of ontogeny, 60K gelatinase, a Ca2+ dependent neutral MMP, seems to be involved in involution, as it appears at the late stage of involution. Further investigations on its regulation by hormones which influence the mammary gland function were carried out. Administration of beta-oestradiol caused the appearance of 60K gelatinase on the 2nd day of involution, while in untreated controls this activity was absent. On treatment of mammary epithelial cells of the 2nd day involuting tissue in culture with beta-oestradiol, the 60K gelatinase activity appeared, while the untreated controls did not show the activity. The effect of beta-oestradiol was studied further by metabolic labelling of the epithelial cells from the 2nd day involuting tissue. A concentration dependent increase in the amount of radiolabelled 60K gelatinase was found on treatment with beta-oestradiol. The upregulation of the 60K gelatinase activity in vivo was also found by immunocytochemical staining of the beta-oestradiol treated tissues. The effect of beta-oestradiol appears to be specific for 60K as the activity of other gelatinases (130K and 68K) in the mammary gland were not affected. Furthermore, a drastic regression of the mammary gland as evidenced by histochemical analysis and a marked decrease in the milk protein production in beta-oestradiol treated tissues indicated the onset of early involution. These results indicate that the 60K gelatinase which is upregulated during involution or on induction of early involution may play a key role in remodelling of extracellular matrix in mammary gland and further that this enzyme is subject to modulation by beta-oestradiol.