The activation of human skin fibroblast procollagenase. Sequence identification of the major conversion products

Hydroxytyrosol from olive fruits prevents blue-light-induced damage in human keratinocytes and fibroblasts

Skin aging is a complex biological process influenced by a combination of endogenous or intrinsic and exogenous or extrinsic factors due to environmental damage. The primary environmental factor that causes human skin aging is the ultraviolet irradiation from the sun. Recently, it was established that the long-term exposure to light-emitting-diode-generated blue light (LED-BL) from electronic devices seems to have a relevant implication in the molecular mechanisms of premature photoaging. BL irradiation induces changes in the synthesis of various skin structures through DNA damage and overproduction of reactive oxygen species (ROS), matrix metalloproteinase-1 and -12, which are responsible for the loss of the main components of the extracellular matrix of skin like collagen type I and elastin. In the current study, using human keratinocytes and fibroblasts exposed to specific LED-BL radiation doses (45 and 15 J/cm ² ), we produced an in vitro model of skin photoaging. We verified that, compared with untreated controls, the treatment with LED-BL irradiation results in the alteration of metalloprotease-1 (collagenase), metalloprotease-12 (elastase), 8-dihydroxy-2'-deoxyguanosine, proliferating cell nuclear antigen, and collagen type I. Moreover, we showed that the photoaging prevention is possible via the use of hydroxytyrosol extracted from olive fruits, well known for antioxidant properties. Our results demonstrated that hydroxytyrosol protects keratinocytes and fibroblasts from LED-BL-induced damage. Thus, hydroxytyrosol might be proposed as an encouraging candidate for the prevention of BL-induced premature photoaging.

Dermal fibroblasts can activate matrix metalloproteinase-1 independent of keratinocytes via plasmin in a 3D collagen model

Photoaging of the skin is marked by obvious wrinkles and mainly depends on degradation of the extracellular matrix (ECM) in the dermis. Matrix metalloproteinase (MMP)-1 is one of the most important factors involved in degradation of the ECM; however, its mechanism of activation is not fully understood. It has been thought that MMP-1 is expressed by dermal fibroblasts as an inactive precursor protein that is activated by proteinases produced by keratinocytes in the epidermis. In this study, we constructed a 3D model of the dermis using collagen-embedded fibroblasts with or without ultraviolet (UV)-A exposure to mimic photoaging in the dermis. Collagen lattices embedded with UV-A-irradiated fibroblasts miniaturized and collagen was degraded to a greater extent than collagen lattices embedded with non-irradiated fibroblasts. The results demonstrate that fibroblasts in this 3D model express activated MMP-1 in the absence of keratinocytes. Moreover, the results confirm that activation of MMP-1 depends on increased plasmin activity in this model and lattice miniaturization was inhibited by the plasmin inhibitor tranexamic acid. Our results suggest that plasmin acts as an activator of MMP-1 and the inhibition of plasmin prevents collagen degradation.

JMJD3 and NF-κB-dependent activation of Notch1 gene is required for keratinocyte migration during skin wound healing

It has been shown that epigenetic regulation plays an important role in skin wound healing. We previously found that histone H3K27me3 demethylase JMJD3 regulates inflammation and cell migration in keratinocyte wound healing. In this study, we identified Notch1 as a direct target of JMJD3 and NF-κB in wounded keratinocytes using in vitro cell and in vivo animal models. We found that Notch1 is up-regulated in the wound edge and its expression is dependent on JMJD3 and NF-κB in wounded keratinocytes. We also found that Notch1 activates the expression of RhoU and PLAU gene, which are critical regulators of cell migration. Consistently, depletion or inactivation of Notch1 resulted in decreased filopodia formation, increased focal adhesion and actin stress fiber, leading to reduced keratinocyte migration and skin wound healing. Thus, our findings provide the molecular mechanism involving JMJD3/NF-κB-Notch pathway in keratinocyte wound healing.

Matrix-metalloproteinases as targets for controlled delivery in cancer: An analysis of upregulation and expression

While commonly known for degradation of the extracellular matrix, matrix metalloproteinases (MMPs) exhibit broad potential for use in targeting of bioactive and imaging agents in cancer treatment. MMPs are upregulated at all stages of expression in cancers. A comprehensive analysis of published literature on expression of all MMP subtypes at the genetic, protein, and activity levels in normal and diseased tissues indicate targeting applicability in a variety of cancers. This expression significantly increases at advanced cancer stages, providing an improved opportunity for controlled release in higher-stage patients. Since MMPs are integral at every stage of metastasis, MMP roles in cancer are discussed with a focus on MMP distribution and mobility within cells and tumors for cancer targeting applications. Several strategies for MMP utilization in targeting - such as matrix degradation, MMP cleavage, MMP binding, and MMP-induced environmental changes - are addressed.

Cloning, Purification and Characterization of the Collagenase ColA Expressed by Bacillus cereus ATCC 14579

Bacterial collagenases differ considerably in their structure and functions. The collagenases ColH and ColG from Clostridium histolyticum and ColA expressed by Clostridium perfringens are well-characterized collagenases that cleave triple-helical collagen, which were therefore termed as ´true´ collagenases. ColA from Bacillus cereus (B. cereus) has been added to the collection of true collagenases. However, the molecular characteristics of B. cereus ColA are less understood. In this study, we identified ColA as a secreted true collagenase from B. cereus ATCC 14579, which is transcriptionally controlled by the regulon phospholipase C regulator (PlcR). B. cereus ATCC 14579 ColA was cloned to express recombinant wildtype ColA (ColA^wt) and mutated to a proteolytically inactive (ColA^E501A) version. Recombinant ColA^wt was tested for gelatinolytic and collagenolytic activities and ColA^E501A was used for the production of a polyclonal anti-ColA antibody. Comparison of ColA^wt activity with homologous proteases in additional strains of B. cereus sensu lato (B. cereus s.l.) and related clostridial collagenases revealed that B. cereus ATCC 14579 ColA is a highly active peptidolytic and collagenolytic protease. These findings could lead to a deeper insight into the function and mechanism of bacterial collagenases which are used in medical and biotechnological applications.

Intracellular matrix metalloproteinase-2 (MMP-2) regulates human platelet activation via hydrolysis of talin

Matrix metalloproteinase (MMP) activity is generally associated with normal or pathological extracellular processes such as tissue remodelling in growth and development or in tumor metastasis and angiogenesis. Platelets contain at least three MMPs, 1, 2 and 9 that have been reported to stimulate or inhibit agonist-induced platelet aggregation via extracellular signals. The non-selective Zn+2 chelating MMP inhibitor, 1,10-phenanthroline, and the serine protease inhibitor, AEBSF, were found to inhibit all tested agonist-induced platelet aggregation reactions. In vitro analysis demonstrated that 1,10-phenanthroline completely inhibited MMP-1,2,and 9 but had little to no effect on calpain activity while the converse was true with AEBSF. We now demonstrate that MMP-2 functions intracellularly to regulate agonist-induced platelet aggregations via the hydrolytic activation of talin, the presumed final activating factor of glycoprotein (GP)IIb/IIIa integrin (the inside-out signal). Once activated GPIIb/IIIa binds the dimeric fibrinogen molecule required for platelet aggregation. The active intracellular MMP-2 molecule is complexed with JAK 2/STAT 3, as demonstrated by the fact that all three proteins are co-immunoprecipitated with either anti-JAK 2, or anti-STAT 3 antibodies and by immunofluorescence studies. The MMP-2 platelet activation pathway can be synergistically inhibited with the non-selective MMP inhibitor, 1,10-phenanthroline, plus a JAK 2 inhibitor. This activation pathway is distinct from the previously reported calpain-talin activating pathway. The identification of a new central pathway for platelet aggregation presents new potential targets for drug regulation and furthers our understanding of the complexity of platelet activation mechanisms.

Cell surface remodeling by plasmin: a new function for an old enzyme

Plasmin, one of the most potent and reactive serine proteases, is involved in various physiological processes, including embryo development, thrombolysis, wound healing and cancer progression. The proteolytic activity of plasmin is tightly regulated through activation of its precursor, plasminogen, only at specific times and in defined locales as well as through inhibition of active plasmin by its abundant natural inhibitors. By exploiting the plasminogen activating system and overexpressing distinct components of the plasminogen activation cascade, such as pro-uPA, uPAR and plasminogen receptors, malignant cells can enhance the generation of plasmin which in turn, modifies the tumor microenvironment to sustain cancer progression. While plasmin-mediated degradation and modification of extracellular matrix proteins, release of growth factors and cytokines from the stroma as well as activation of several matrix metalloproteinase zymogens, all have been a focus of cancer research studies for decades, the ability of plasmin to cleave transmembrane molecules and thereby to generate functionally important cleaved products which induce outside-in signal transduction, has just begun to receive sufficient attention. Herein, we highlight this relatively understudied, but important function of the plasmin enzyme as it is generated de novo at the interface between cross-talking cancer and host cells.

Up-regulated expression of extracellular matrix remodeling genes in phagocytically challenged trabecular meshwork cells

Background

Cells in the trabecular meshwork (TM), the tissue responsible for draining aqueous humor out of the eye, are known to be highly phagocytic. Phagocytic function in TM cells is thought to play an important role in the normal functioning of the outflow pathway. Dysfunction of phagocytosis could lead to abnormalities of outflow resistance and increased intraocular pressure (IOP). However, the molecular mechanisms triggered by phagocytosis in TM cells are completely unknown.

Methodology/Principal Findings

Gene expression profile analysis of human TM cells phagocytically challenged to E. coli or pigment under physiological and oxidative stress environment were performed using Affymetrix U133 plus 2.0 array and analyzed with Genespring GX. Despite the differential biological response elicited by E. coli and pigment particles, a number of genes, including MMP1, MMP3, TNFSF11, DIO2, KYNU, and KCCN2 showed differential expression with both phagocytic ligands in all conditions. Data was confirmed by qPCR in both human and porcine TM cells. Metacore pathway analysis and the usage of recombinant adenovirus encoding the dominant negative mutant of IkB identified NF-κB as a transcription factor mediating the up-regulation of at least MMP1 and MMP3 in TM cells with phagocytosis. In-gel zymography demonstrated increased collagenolytic and caseinolytic activities in the culture media of TM cells challenge to E. coli. In addition, collagenolytic I activity was further confirmed using the self-quenched fluorescent substrate DQ-Collagen I.

Conclusions/Significance

Here we report for the first time the differential gene expression profile of TM cells phagocytically challenged with either E. coli or pigment. Our data indicate a potential role of phagocytosis in outflow pathway tissue homeostasis through the up-regulation and/or proteolytic activation of extracellular matrix remodeling genes.

Matrix Metalloproteinase-1 Activation via Plasmin Generated on Alveolar Epithelial Cell Surfaces

Plasmin is a potent protease related to tissue repair/remodeling not by fibrinolysis alone but also by activation of cytokines such as transforming growth factor and hepatocyte growth factor and by activation of matrix metalloproteases. We examined whether matrix matalloproteinase-1 was activated via plasminogen activation on surfaces of cultured alveolar epithelial cells (A-549). Cells were cultured overnight with plasminogen, pro-matrix metalloproteinase-1, and type I collagen as a substrate. Sodium dodecil sulfate-polyacrylamide gel electrophoresis was used to detect type I collagen degradation in culture supernatant. Collagen degradation corresponded to cell surface plasmin generation. No such finding was seen in the absence of cells or plasminogen. Alveolar epithelial plasminogen activation is important in matrix metalloproteinase-1 activation and thus presumably in tissue remodeling in pulmonary fibrosing pulmonary diseases such as idiopathic pulmonary fibrosis.

Extracellular matrix remodeling and metalloproteinase involvement during intestine regeneration in the sea cucumber Holothuria glaberrima

The sea cucumber, Holothuria glaberrima, has the capacity to regenerate its internal organs. Intestinal regeneration is accomplished by the thickening of the mesenteric border and the invasion of this thickening by mucosal epithelium from the esophagus and the cloaca. Extracellular matrix (ECM) remodeling has been associated with morphogenetic events during embryonic development and regeneration. We have used immunohistochemical techniques against ECM components to show that differential changes occur in the ECM during early regeneration. Labeling of fibrous collagenous components and muscle-related laminin disappear from the regenerating intestine and mesentery, while fibronectin labeling and 4G7 (an echinoderm ECM component) are continuously present. Western blots confirm a decrease in fibrous collagen content during the first 2 weeks of regeneration. We have also identified five 1,10-phenanthroline-sensitive bands in collagen gelatin zymographs. The gelatinolytic activities of these bands are enhanced during early stages of regeneration, suggesting that the metalloprotease activity is associated with ECM remodeling. Inhibition of MMPs in vivo with 1,10-phenanthroline, p-aminobenzoyl-Gly-Pro-D-Leu-D-Ala hydroxamate or N-CBZ-Pro-Leu-Gly hydroxamate produces a reversible inhibition of intestinal regeneration and ECM remodeling. Our results show that significant changes in ECM content occur during intestine regeneration in the sea cucumber and that the onset of these changes is correlated to the proteolytic activities of MMPs.

Substrate binding of gelatinase B induces its enzymatic activity in the presence of intact propeptide

Expression of gelatinase B (matrix metalloprotease 9) in human placenta is developmentally regulated, presumably to fulfill a proteolytic function. Here we demonstrate that gelatinolytic activity in situ, in tissue sections of term placenta, is co-localized with gelatinase B. Judging by molecular mass, however, all the enzyme extracted from this tissue was found in a proform. To address this apparent incongruity, we examined the activity of gelatinase B bound to either gelatin- or type IV collagen-coated surfaces. Surprisingly, we found that upon binding, the purified proenzyme acquired activity against both the fluorogenic peptide (7-methoxycoumarin-4-yl)-acetic acid (MCA)-Pro-Leu-Gly-Leu-3-(2,4-dinitrophenyl)-l-2,3-diaminopropionyl-Ala-Arg-NH(2) and gelatin substrates, whereas its propeptide remained intact. These results suggest that although activation of all known matrix metalloproteases in vitro is accomplished by proteolytic processing of the propeptide, other mechanisms, such as binding to a ligand or to a substrate, may lead to a disengagement of the propeptide from the active center of the enzyme, causing its activation.

The modulation of corneal keratocyte and epithelial cell responses to poly(2-hydroxyethyl methacrylate) hydrogel surfaces: phosphorylation decreases collagenase production in vitro

We examined the regulation of collagenase production by rabbit keratocyte, epithelial and mixed keratocyte/epithelial cell cultures which were exposed to poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel surfaces with different chemistries and morphologies (sponge and homogeneous gels). Tissue culture modified polystyrene (TCP), used as a control surface, induced the maximum collagenase response with all cell culture types. Copolymer homogeneous gels containing 2-ethoxyethyl methacrylate (EEMA) or methyl methacrylate (MMA) induced a high response in keratocyte cultures, whilst PHEMA hydrogels induced a moderate response and the phosphorylated PHEMA (phos-PHEMA) hydrogel induced no response. Epithelial cells cultured on PHEMA, copolymer and phos-PHEMA hydrogels produced less collagenase activity than the keratocyte cells. The profile of collagenases produced by epithelial cells in response to phos-PHEMA was different to that for the other hydrogels. Co-cultured cells produced higher levels of collagenase (relative to the TCP) in response to hydrogels than did either the keratocytes or epithelial cells alone, but the response of phos-PHEMA was still the lowest. The overall enzyme response to the sponge hydrogels was lower than that to the homogeneous hydrogels, although this effect was less prominent in the keratocyte cultures. The markedly reduced and alternative collagenase responses to phosphorylated surfaces was not a consequence of cell death, and may be a phenomenon related to changes in cell surface charge and morphology.

Ca(2+) and Zn(2+) binding properties of peptide substrates of vertebrate collagenase, MMP-1

To understand the role of Ca(2+) in vertebrate in the structure and action of collagenase, we have examined peptides that interact with recombinant human fibroblast collagenase for their affinities towards Ca(2+) and Zn(2+) in a non-polar solvent. Two of the peptides, GPQGIAGQ and GNVGLAGA, had sequences in collagen which are, respectively, cleaved and not cleaved by collagenase. A third peptide, PSYFLNAG, had a collagenase-cleaved sequence in ovostatin, a globular protein substrate. Peptides TVGCEECTV and CLPREPGL were derived from TIMP-1; the former competitively inhibits collagenase while the latter does not. The relative rates of hydrolysis of the peptides by collagenase had the order GPQGIAGQ>PSYFLNAG>GNVGLAGA. Circular dichroism spectral data in trifluoroethanol showed that while the TIMP control peptide, CLPREPGL, bound only Zn(2+), the other four peptides bound both Ca(2+) and Zn(2+) with definite stoichiometries. Ca(2+) could displace Zn(2+) in the substrate peptides while Zn(2+) displaced Ca(2+) in the TIMP peptide. GPQGIAGQ, PSYFLNAG and TVGCEECTV formed peptide:Ca(2+):Zn(2+) ternary complexes. Our results suggest that both collagen and globular protein substrates of collagenase may bind Ca(2+) and Zn(2+) in the enzyme's active site. This, in turn, may account for the known importance of the non-catalytic Ca(2+) and Zn(2+) in collagenase activity.

Detection and characterization of metalloproteinases with gelatinolytic, fibronectinolytic and fibrinogenolytic activities in brown spider (Loxosceles intermedia) venom

By studying Loxosceles intermedia (Brown spider) venom we were able to detect a proteolytic action on fibronectin and fibrinogen but an inability to degrade full length laminin, type I and type IV collagens. By studying enzyme inhibitors we observed that divalent metal chelators as EDTA and 1,10-phenanthroline completely blocked this cleaving action whereas serine-protease inhibitors, thiol-protease inhibitor and acid-protease inhibitor showed little or no effect on the proteolytic activity of the venom indicating involvement of a metalloproteinase. Zymogram analysis of venom detected a 35 kDa molecule with gelatinolytic activity. The metalloproteinase nature was further supported by its sensitivity to 4-aminophenyl mercuric acetate (APMA) treatment which decreased its molecular weight to 32 kDa, inhibition of its gelatinolytic effect by 1,10-phenanthroline and its elution from gelatin-sepharose affinity beads. In addition, zymogram experiments using fibronectin and fibrinogen as substrates detected a fibronectinolytic and fibrinogenolytic band at 28 kDa which changed its electrophoretic mobility to 20 kDa band after organomercurial treatment. The inhibitory effect of 1,10 phenanthroline and APMA sensitivity on this proteolytic effect confirmed the presence of a second metalloproteinase in the venom. The data presented herein describe two invertebrate metalloproteinases in L. intermedia venom with different specificities one gelatinolytic and another, fibronectinolytic and fibrinogenolytic, probably involved in the harmful effects of the venom.

Production of trypsins by human gastric cancer cells correlates with their malignant phenotype

Proteolytic degradation of extracellular matrix is a critical step in tumour invasion and metastasis. To examine the role of trypsin in tumour dissemination, we cloned two variants (S4 and R3 cells) from STKM-1, a trypsinogen 1-producing diffuse gastric cancer cell line. Western blot analysis with antitrypsin antibody showed that 26 and 24 kDa proteins were highly detected in S4 conditioned medium (CM) in comparison to R3 CM. In addition to the 26 and 24 kDa proteins, 25 and 23 kDa bands, which correspond to enterokinase-activated trypsin, were found only in S4 CM. When the CMs of the two clones were treated with enterokinase, the 25 and 23 kDa trypsin activities in S4 CM were effectively increased as compared with R3 CM. When the two clones were inoculated intraperitoneally (i.p.) into nude mice, S4 cells strongly invaded the liver, pancreas and peritoneum and killed the hosts more rapidly than R3 cells: the 50% survival time was 50 days for S4 and 82 days for R3 cells. These results suggest that trypsin production is associated with the invasive growth of STKM-1 gastric cancer cells.

Isolation and Characterization of the cDNA for Mouse Neutrophil Collagenase: Demonstration of Shared Negative Regulatory Pathways for Neutrophil Secondary Granule Protein Gene Expression

A characteristic of normal neutrophil maturation is the induction of secondary granule protein (SGP) mRNA expression. Several leukemic human cell lines mimic normal morphologic neutrophil differentiation but fail to express SGPs, such as lactoferrin (LF) and neutrophil gelatinase (NG). In contrast, two murine cell lines (32D C13 and MPRO) are able to differentiate into neutrophils and induce expression of LF and NG. Therefore, to study the normal regulation and function of these genes, the corresponding murine homologs must be isolated. Using cDNA representational difference analysis (RDA) to compare a committed myeloid progenitor cell line (EPRO) with the multipotent stem cell line from which it was derived (EML), we isolated a fragment bearing homology to human neutrophil collagenase (hNC). Here, we describe the cloning and characterization of a full-length (∼2 kb) clone that exhibits nearly 65% nucleotide and 73% amino acid identity to hNC. Ribonuclease protection analysis (RPA) of the tissues and cell lines shows that mouse NC (mNC) is expressed only in cell lines exhibiting neutrophilic characteristics, further confirming its identity as the mouse homolog of hNC. Furthermore, we have demonstrated a shared negative regulatory pathway for this and other SGP genes. We have previously shown that CCAAT displacement protein (CDP/cut) binds to a specific region of the LF promoter, and overexpression of CDP blocks G-CSF–induced upregulation of LF gene expression in 32D C13 cells. We show here that in these cells, upregulation of both NC and NG is also blocked. CDP is thus the first identified transcription factor that is a candidate for mediating the shared regulation of neutrophil SGP protein genes.

Isolation and Characterization of the cDNA for Mouse Neutrophil Collagenase: Demonstration of Shared Negative Regulatory Pathways for Neutrophil Secondary Granule Protein Gene Expression

A characteristic of normal neutrophil maturation is the induction of secondary granule protein (SGP) mRNA expression. Several leukemic human cell lines mimic normal morphologic neutrophil differentiation but fail to express SGPs, such as lactoferrin (LF) and neutrophil gelatinase (NG). In contrast, two murine cell lines (32D C13 and MPRO) are able to differentiate into neutrophils and induce expression of LF and NG. Therefore, to study the normal regulation and function of these genes, the corresponding murine homologs must be isolated. Using cDNA representational difference analysis (RDA) to compare a committed myeloid progenitor cell line (EPRO) with the multipotent stem cell line from which it was derived (EML), we isolated a fragment bearing homology to human neutrophil collagenase (hNC). Here, we describe the cloning and characterization of a full-length (∼2 kb) clone that exhibits nearly 65% nucleotide and 73% amino acid identity to hNC. Ribonuclease protection analysis (RPA) of the tissues and cell lines shows that mouse NC (mNC) is expressed only in cell lines exhibiting neutrophilic characteristics, further confirming its identity as the mouse homolog of hNC. Furthermore, we have demonstrated a shared negative regulatory pathway for this and other SGP genes. We have previously shown that CCAAT displacement protein (CDP/cut) binds to a specific region of the LF promoter, and overexpression of CDP blocks G-CSF–induced upregulation of LF gene expression in 32D C13 cells. We show here that in these cells, upregulation of both NC and NG is also blocked. CDP is thus the first identified transcription factor that is a candidate for mediating the shared regulation of neutrophil SGP protein genes.

Small mechanical strains selectively suppress matrix metalloproteinase-1 expression by human vascular smooth muscle cells

Mechanical forces and biochemical stimuli may interact to regulate cellular responses. In this study, we tested the hypothesis that very small mechanical strains interact with growth factors in the regulation of matrix metalloproteinase (MMP)-1. Human vascular smooth muscle cells (VSMCs) were cultured on a precoated silicone membrane in a device that imposes a highly uniform biaxial strain. VSMCs cultured on fibronectin were treated with cyclic 1-Hz strains of 0, 1, or 4%, and MMPs were assayed by Western analysis or gelatin zymography. Small strains did not induce MMP-1 in VSMCs, but strain was a potent inhibitor of platelet-derived growth factor (PDGF)- or tumor necrosis factor-alpha-induced synthesis of MMP-1. In contrast, MMP-2 and TIMP-2 levels were not changed by PDGF and/or mechanical strain. VSMCs strained on the 120-kDa chymotryptic fragment of fibronectin or RGD peptides suppressed PDGF-induced expression of MMP-1, indicating that this effect is not mediated by the heparin-binding domain or connecting segment-1 of fibronectin. Northern analysis of ets-1, a transcriptional activator of MMP-1 expression, showed that strain down-regulated ets-1 expression, whereas c-fos expression was augmented. Thus, small deformations can selectively suppress MMP-1 synthesis by VSMCs, demonstrating the exquisite sensitivity of the cell to mechanical stimuli.

Overexpression of the matrix metalloproteinase matrilysin results in premature mammary gland differentiation and male infertility

To examine the role of matrilysin (MAT), an epithelial cell-specific matrix metalloproteinase, in the normal development and function of reproductive tissues, we generated transgenic animals that overexpress MAT in several reproductive organs. Three distinct forms of human MAT (wild-type, active, and inactive) were placed under the control of the murine mammary tumor virus promoter/enhancer. Although wild-type, active, and inactive forms of the human MAT protein could be produced in an in vitro culture system, mutations of the MAT cDNA significantly decreased the efficiency with which the MAT protein was produced in vivo. Therefore, animals carrying the wild-type MAT transgene that expressed high levels of human MAT in vivo were further examined. Mammary glands from female transgenic animals were morphologically normal throughout mammary development, but displayed an increased ability to produce beta-casein protein in virgin animals. In addition, beginning at approximately 8 mo of age, the testes of male transgenic animals became disorganized with apparent disintegration of interstitial tissue that normally surrounds the seminiferous tubules. The disruption of testis morphology was concurrent with the onset of infertility. These results suggest that overexpression of the matrix-degrading enzyme MAT alters the integrity of the extracellular matrix and thereby induces cellular differentiation and cellular destruction in a tissue-specific manner.

Activation mechanism of meprins, members of the astacin metalloendopeptidase family

Meprins are mammalian zinc metalloendopeptidases with protease domains structurally related to astacin, the prototype of the "astacin family" of metalloproteases. Mature, active astacins are produced by proteolytic removal of an activation peptide to generate a new NH2-terminal residue. Structural studies indicate that the NH2-terminal ammonium group inserts into a water-filled cavity adjacent to the active site to form a salt bridge with a Glu residue that is conserved in all astacins. A similar interaction is known to play a crucial role in the activation of trypsin, resulting in the hypothesis that this salt bridge is required for the activation of astacin-like proteases. In this study, we have used the mouse meprin alpha subunit as a model to test this hypothesis of zymogen activation of the astacins. Mutants were generated to vary the NH2-terminal residue of the mature meprin alpha subunit (Asn78) and its putative salt bridge partner (Glu178). In addition, mutants creating NH2-terminal extensions and truncations were expressed in human embryonic kidney 293 cells. The recombinant proteins were activated by limited protease digestion and assayed for enzymatic activity and thermal stability. Point mutations of Asn78 resulted in enzymes with activity comparable to the wild-type enzyme, indicating that the structure of this side chain is not essential for activity. NH2-terminal extension mutants of meprin alpha retained partial activity, with greater decreases against peptide relative to protein substrates. A mutant with a deletion of Asn78 to disrupt salt bridge formation with Glu178 had full activity, indicating that the putative salt bridge with Glu178 is not essential for enzyme activity. However, all changes in meprin alpha subunit NH2-terminal structure were found to decrease the thermal stability of the enzyme. These observations and additional data indicate that the zymogen activation mechanism of meprin and other astacins differs from that of the trypsin family of enzymes, and has some features in common with matrixins. It is proposed that prosequence removal of astacins allows the formation of hydrogen bonds involving the two NH2-terminal residues that are critical for enzyme structure.

Dog mast cell alpha-chymase activates progelatinase B by cleaving the Phe88-Gln89 and Phe91-Glu92 bonds of the catalytic domain

In prior work we showed that a metallogelatinase is secreted from dog mastocytoma cells and directly activated by exocytosed mast cell alpha-chymase. The current work identifies the protease as a canine homologue of progelatinase B (92-kDa gelatinase, MMP-9), determines the sites cleaved by alpha-chymase, and explores the regulation of gelatinase expression in mastocytoma cells. To obtain a cDNA encoding the complete sequence of mastocytoma gelatinase B, a 2. 3-kilobase clone encoding progelatinase was isolated from a BR mastocytoma library. The sequenced cDNA predicts a 704-amino acid protein 80% identical to human progelatinase B. Regions thought to be critical for active site latency, such as the Cys-containing propeptide sequence, PRCGVPD, and the catalytic domain sequence, HEFGHALGLDHSS, are entirely conserved. Cleavage of progelatinase B by purified dog alpha-chymase yielded an approximately 84-kDa product that contained two NH2-terminal amino acid sequences, QTFEGDLKXH and EGDLKXHHND, which correspond to residues 89-98 and 92-101 of the cDNA predicted sequence, respectively. Thus, alpha-chymase cleaves the catalytic domain of gelatinase B at the Phe88-Gln89 and Phe91-Glu92 bonds. Like BR cells, the C2 line of dog mastocytoma cells constitutively secrete progelatinase B which is activated by alpha-chymase. By contrast, non-chymase-producing C1 cells secrete a gelatinase B (which remains in its proform) only in response to 12-O-tetradecanoylphorbol-13-acetate. Whereas 12-O-tetradecanoylphorbol-13-acetate stimulation of BR cells produced a approximately 15-fold increase in gelatinase B mRNA expression, dexamethasone down-regulated its expression by approximately 5-fold. Thus, extracellular stimuli may regulate the amount of mast cell progelatinase B expressed by mast cells. These data further support a role for mast cell alpha-chymase in tissue remodeling involving gelatinase B-mediated degradation of matrix proteins.

Expression of trypsin in vascular endothelial cells

Proteinases produced by vascular endothelial cells are expected to play important roles in many biological processes. Here we report that human vascular endothelial cells express trypsinogen-2 mRNA and its protein product in culture. The trypsinogen production was stimulated by a tumor promoter and associated with cell growth. In situ hybridization analysis showed that the trypsinogen gene was significantly expressed in vascular endothelial cells around gastric tumors and in patients with disseminated intravascular coagulation (DIC). These results suggest the possible roles of endothelial cell-derived trypsin in tumor angiogenesis and abnormal blood coagulation.

Activation and novel processing of matrix metalloproteinases by a thiol-proteinase from the oral anaerobe Porphyromonas gingivalis

A critical outcome of periodontal disease is degradation of the collagenous periodontal ligament that connects teeth to bone in the dental arch. Periodontal diseases occur in response to bacterial colonization of the teeth, but their molecular pathogenesis is still speculative. One family of enzymes, known as the matrix metalloproteinases (MMPs), has been implicated in the degradation of the periodontal ligament. MMPs, which are also suspected to play a role in many other physiologic and pathologic remodeling processes, can be secreted by epithelial cells surrounding the teeth and are found in relative abundance in tissues and fluids near periodontally diseased sites. Since most MMPs are secreted as inactive zymogens which may be activated by limited proteolysis, it has been suggested that proteinases expressed by the infecting periodontal pathogens might activate latent host MMPs to initiate or accelerate degradation of the collegenous periodontal ligament. The aim of this work was to examine interactions between purified host MMPs and bacterial proteinase. In this article, we demonstrate that a proteinase isolated from the periodontopathogen Porphyromonas gingivalis can activate MMP-1, MMP-3, and MMP-9 and can catalyze the superactivation of MMP-1 by MMP-3. Activation of these MMPs is demonstrated to result from initial hydrolysis within their propeptide. Also, for MMP-1 and MMP-9, the P. gingivalis proteinase cleaves the MMP propeptide following a lysine residue at a previously unreported site which, for both MMPs, is one residue NH2-terminal to the known autocatalytic cleavage site. These data describe a mode of virulence for the periodontopathogen Porphyromonas gingivalis that involves activation of host-degradative enzymes.

Effect of transforming growth factor-beta on the plasminogen activator system in cultured first trimester human cytotrophoblasts

Plasminogen activators (PAs) play an important role in facilitating trophoblast invasion of the uterus and in the maintenance of blood fluidity within the placental intervillous spaces. We previously found that transforming growth factor-beta (TGF-beta), produced mainly by the decidua, inhibits first trimester trophoblast invasiveness at least partly via induction of tissue inhibitor of metalloproteinases-1 production and secretion by the trophoblasts. The present study examined whether TGF-beta 1 affects PA and plasminogen activator inhibitor-1 (PAI-1) production by cultured human cytotrophoblasts. Immortalized first trimester human cytotrophoblasts (HTR-8/SVneo) were cultured in the absence or presence of TGF-beta 1 (0-10 ng/ml) for 24 h, after which the levels of urokinase-type PA (uPA), PAI-1 and uPA activity in the serum-free conditioned media were determined by enzyme-linked immunosorbent assay (ELISA), protein zymography, and a chromogenic uPA activity assay. Cellular PAI-1 mRNA levels were also determined in cultures following a 24-h incubation with a single dose (5 ng/ml) of TGF-beta 1. Presence of TGF-beta 1 at 1 ng/ml resulted in a greater than 12-fold reduction in the levels of total uPA as determined by ELISA. Furthermore, released uPA activity levels in similar cultures incubated with 5 ng/ml of TGF-beta 1 were reduced to 35 per cent of control values. In contrast, cultures incubated with as little as 0.1 ng/ml TGF-beta exhibited a 63 per cent increase in the levels of secreted PAI-1 protein. Similarly, both the 2.2- and 3.0-kb PAI-1 cellular mRNA species were elevated in trophoblast cells incubated with 5 ng/ml TGF-beta 1 when compared with control cells. Thus, it appears that the reduced uPA activity observed in the cultures incubated with TGF-beta 1 is due to reduced secretion of uPA and increased PAI-1 production and secretion. These results suggest that TGF-beta may also exert its anti-invasive effect by down-regulating trophoblast-derived PA activity. Through its effects on the PA system, TGF-beta may also play an indirect role in the regulation of uteroplacental blood flow.

The catalytic domain of activated collagenase I (MMP-1) is absolutely required for interaction with its specific inhibitor, tissue inhibitor of metalloproteinases-1 (TIMP-1)

Here, we describe the production of recombinant human tissue inhibitor of metalloproteinases-1 (rTIMP-1) and wild-type and mutant human collagenase type I (rMMP-1) proteins in SF9 cells by the baculovirus expression system. Wild-type MMP-1, as well as the MMP-1 mutant lacking the C-terminal hemopexin-like domain [des-(248-450)-MMP-1], exhibit enzymatic activity upon cleavage of the prodomain by treatment with trypsin or 4-aminophenylmercuric acetate. Enzyme activity of both proteins can be inhibited by addition of rTIMP. Deletion of the complete active-site [des-(161-228)-MMP-1] within the catalytic domain, or mutation of a single His residue of the Zn2+ binding domain (His199), generates stable forms of MMP-1 proteins which are unable to digest collagen type I or beta-casein. In addition to co-immunoprecipitation analysis, we have established a rapid and sensitive ELISA assay using immobilized rTIMP to determine the structural requirements of MMP-1 to form complexes with its inhibitor. Only the activated and not the latent forms of wild-type and C-terminal mutant des-(248-450)-MMP-1 proteins are able to form complexes with TIMP. Neither mutation of His199, nor deletion mutants des-(161-228)-MMP-1 and des-(161-228/248-450)-MMP-1, interact with TIMP. This demonstrates that the C-terminal hemopexin domain of MMP-1, in contrast to the corresponding regions of gelatinase A and gelatinase B, does not interact with TIMP-1. In summary, we have shown that the integrity of the catalytic domain of MMP-1 and its ability to bind Zn2+ is absolutely required for complex formation with TIMP-1, which further underlines the importance of this region for proper regulation of enzymatic activity of MMP-1.

Cooperative binding of Ca2+ to human interstitial collagenase assessed by circular dichroism, fluorescence, and catalytic activity

Dissociation of Ca2+ from human interstitial collagenase induced either by chelation with EGTA or by dilution resulted in loss of enzyme activity, a red shifted emission maximum from 334 to 340 nm and quenching of protein fluorescence by 10% at 340 nm. Circular dichroism indicated that secondary structure was unaffected by EGTA. Ca2+ binding to the EGTA-treated enzyme as assessed by fluorescence was cooperative (Hill coefficient, 2.9; 50% saturation at 0.4 mM Ca2+). The dependence of catalytic activity on [Ca2+] was also cooperative (Hill coefficient, 1.7-2.0; midpoint [Ca2+], 0.2 mM). The Ca2+-reconstituted protein was indistinguishable from the untreated enzyme by activity and fluorescence measurements. These results demonstrate that removal of Ca2+ from full-length collagenase generates a catalytically incompetent, partially unfolded state with native secondary structure but altered tertiary structure characterized by exposure of at least one tryptophyl residue to a more polar environment.

Regulation of membrane-type matrix metalloproteinase-1 expression by growth factors and phorbol 12-myristate 13-acetate

Overexpression of membrane-type matrix metalloproteinase (MT-MMP-1) results in the activation of both endogenous and exogenous 72-kDa gelatinase. To understand the effects of MT-MMP-1 on 72-kDa gelatinase activation, we analyzed its expression in human fibroblasts and HT-1080 fibrosarcoma cells. Both cell types expressed the MT-MMP-1 mRNA constitutively at a considerable level and treatment of cells with PMA enhanced the expression about 2-3-fold. Concanavalin A treatment increased MT-MMP-1 mRNA levels in fibroblasts about 4-fold. Induction of MT-MMP-1 by phorbol 12-myristate 13-acetate (PMA) required protein synthesis as shown by cycloheximide inhibition. The induction was also inhibited by dexamethasone. Analysis of MT-MMP-1 mRNA stability using actinomycin D indicated that the half-life was rather long and not affected by PMA, suggesting transcriptional regulation. Only HT-1080 cells had significant 72-kDa gelatinase processing activity after treatment with PMA or concanavalin A, while fibroblasts were virtually negative. Immunoblotting analysis of fibroblast lysates indicated that MT-MMP-1 was present mainly in a 60-kDa form. PMA and concanavalin A caused 2-4-fold increases in its protein levels, while in HT-1080 cells PMA, concanavalin A, or overexpression of MT-MMP-1 did not significantly enhance the level of the 60-kDa protein. Instead, an immunoreactive, proteolytically processed 43-kDa form was observed, and its appearance correlated to 72-kDa gelatinase processing activity. Thus 72-kDa gelatinase activation, while enhanced by MT-MMP-1 expression, needs additional co-operating factors.

Divergent patterns of matrix metalloproteinase activity during wound healing in ileum and colon of rats

BACKGROUND

Uncontrolled and increased extracellular matrix degradation during early anastomotic repair in the intestine may reduce wound strength increasing the risk of anastomotic dehiscence.

AIMS

To characterise the metalloproteinases present in intact and anastomosed ileum and colon to study their role in matrix degradation after surgery.

SUBJECTS

Tissue extracts of uninjured, and of anastomosed rat ileum and colon at postoperative days 1, 2, 3, 7, and 90, were used.

METHODS

Metalloproteinases were identified by gelatin and casein zymography. Aminophenylmercuric acetate (APMA) treatment was used to activate latent metalloproteinases.

RESULTS

Both uninjured ileum and colon contained a 60 and 67 kDa activity, but a 54 and 72 kDa gelatinase was present in ileum only, and a 51 kDa activity in colon only. APMA treatment converted the 60 kDa protease to 54 and 51 kDa forms and the 72 kDa protease to the 67 kDa form. These gelatinases may correspond to latent and active forms of MMP 1 and MMP 2, respectively. Additional metalloproteinases were observed after anastomotic construction. Both ileum and colon contained 95 and 230 kDa gelatinases, which were converted to 83 and 76 kDa forms by APMA. They may be the latent and active forms of MMP 9, respectively. Gelatinolytic activities of 25 and 28 kDa were only found in anastomosed ileum. Caseinolytic activities were only found in ileum extracts and those were most prominent at day 1, 2, and 3 after surgery.

CONCLUSIONS

The metalloproteinase pattern in ileum and colon differ considerably suggesting that matrix degradation after anastomotic construction may also vary.

Activation of human progelatinase A by collagenase and matrilysin: activation of procollagenase by matrilysin

Proteolytic and nonproteolytic methods were used to investigate the mechanism(s) by which human fibroblast progelatinase A and fibroblast-type procollagenase can be activated. Both collagenase and matrilysin were able to activate progelatinase A, resulting in an amino terminus in gelatinase A of Tyr81. The cleavage occurred distal to Cys73 within the sequence of PRCGNPDVAN80-Y81NFFPRKP. While several nonproteolytic reagents were tested, only the heavy metal Hg(II) and p-chloromercuribenzoate (PCMB) were able to induce activation of progelatinase A and resulted in the conversion of the latent 72-kDa gelatinase A to an active form of about 64.5 kDa. Matrilysin was also able to activate procollagenase and resulted in an amino terminus in collagenase of Phe81. These results suggest that fibroblast-type collagenase and matrilysin may be physiologically relevant activators of progelatinase A; the maintenance of latency and the process of activation for progelatinase A may occur through the cysteine-switch mechanism, and the proteolytic activation of procollagenase by matrilysin resulted in the same amino terminus as produced by stromelysin-1.

Activation of human neutrophil procollagenase by stromelysin 2

Neutrophil procollagenase (MMP-8) was efficiently activated by incubation with active stromelysin 2 (MMP-10). A single-step activation mechanism involving the cleavage of the Gly78-Phe79 peptide bond at the end of the propeptide domain was observed. Determination of the collagenolytic activity revealed the generation of active neutrophil collagenase displaying high specific activity. When compared with the specific activity following mercurial activation, which generates active collagenase by autoproteolytic cleavage of either Phe79-Met8O or Met8O-Leu81 peptide bonds [Bläser, J., Knäuper, V., Osthues, A., Reinke, H. & Tschesche, H. (1991) Eur J. Biochem. 202, 1223-1230], the specific activity of the stromelysin-2-activated enzyme was considerably higher. Thus, human neutrophil procollagenase was 'superactivated' by stromelysin 2, as was recently shown for the stromelysin-1-activated enzyme [Knäuper, V., Wilhelm, S. M., Seperack, P. K., De Clerck, Y. A., Langley, K. E., Osthues, A. & Tschesche, H. 1993 a) Biochem. J. 295, 581-586].

Analysis of the active site and activation mechanism of the Leishmania surface metalloproteinase GP63

The major surface glycoprotein of Leishmania promastigotes, referred to as GP63, is a zinc metalloproteinase of 63,000 M(r) containing a glycosylphosphatidylinositol (GPI) membrane anchor. Recent studies demonstrated that recombinant GP63 (rGP63) expressed by the baculovirus insect cell system was secreted as a glycosylated latent proteinase that required activation for full proteinase activity (Button et al. (1993) Gene 134, 75-81). To extend these studies, the active site of L. major GP63 was characterized by site-directed mutagenesis and the activation mechanism of latent rGP63 was studied using both secreted and cell surface expression systems. To determine whether the proposed active site of L. major GP63 conforms to other well characterized zinc metalloproteinases, the proposed GP63 catalytic Glu-265, corresponding to catalytic Glu-147 of thermolysin, was changed to Asp-265. Using a transient expression system in COS-7 cells, expression of the Asp-265 mutant GP63 gene resulted in rGP63 with no detectable proteinase activity, whereas expression of the wild-type GP63 gene resulted in rGP63 with a level of proteinase activity similar to native GP63. Thus, the mechanism of GP63 proteinase activity is predicted to be homologous to that of other well characterized zinc metalloproteinases. NH2-Terminal sequence analysis revealed that activation with HgCl2 resulted in removal of the pro region, ultimately generating the mature NH2-terminus. This processing included the removal of a conserved Cys residue (Cys-48) and occurred by a cis mechanism, since the addition of previously activated rGP63 did not lead to an enhancement of latent rGP63 proteinase activation. The mechanism of activation of GP63 is consistent with the cysteine switch mechanism proposed for matrix metalloproteinases and thus has been conserved from protozoa to mammals.

Characterization of the Phe-81 and Val-82 human fibroblast collagenase catalytic domain purified from Escherichia coli

Soluble recombinant human fibroblast collagenase catalytic domain was highly expressed and purified from Escherichia coli. The expression construct utilized the T7 gene 10 promoter for transcription of a two-cistron messenger RNA which encoded the ubiquitin-collagenase catalytic domain fusion protein as the second cistron. The ubiquitin domain was attached to the collagenase catalytic domain with the linker sequences Gly-Gly-Thr-Gly-Asp-Val-Ala-Gln (wild type) or Gly-Gly-Thr-Gly-Asp-Val-Gly-His (mutant) which served as cleavage sites for in vitro activation. The last four residues of the linker were included based on the crystal structure of human prostromelysin-1 catalytic domain. Soluble fusion proteins purified from E. coli retained the proteolytic activity of the collagenase catalytic domain. The collagenase catalytic domain was released by either autoproteolytic or stromelysin-1-catalyzed cleavage, purified to homogeneity, and separately possess Phe-81, Val-82, or Leu-83 as the amino-terminal residue. Very similar kcat/Km values were determined for the Phe-81 and Val-82 forms using continuous fluorogenic and chromogenic peptide cleavage assays.

Interstitial collagenase (MMP-1) expression in human carotid atherosclerosis

BACKGROUND

In human atherosclerosis, most clinical events occur when plaque integrity is compromised and hemorrhage and thrombosis result. One mechanism for this might be the release by plaque cells of matrix-degrading proteases, such as interstitial collagenase (matrix metalloproteinase-1, MMP-1), which degrades two major plaque structural proteins, types I and III collagen. This study was undertaken to determine whether MMP-1 is expressed in human atherosclerotic plaques.

METHODS AND RESULTS

To determine the cellular source and location of MMP-1 in human carotid atherosclerotic lesions, in situ hybridization and immunohistochemistry were performed on 20 endarterectomy specimens. Six nonatherosclerotic carotid arteries also were studied. Intense MMP-1 expression (mRNA and protein) was detected in a subset of plaque macrophages located at the borders of the lipid cores adjacent to fibrous caps and shoulder regions. Subsets of plaque smooth muscle cells and endothelial cells also expressed MMP-1. There was a strong correlation between the percentage of the lipid core occupied by hemorrhage and the percentage of the lipid core perimeter positive for MMP-1 (r = .823, P = .0001). MMP-1 was not detected in any cell type in nonatherosclerotic carotid arteries.

CONCLUSIONS

This study demonstrates that MMP-1 is expressed by several cell types in human carotid atherosclerosis and that there is a correlation between the expression of the protease and histopathological evidence of plaque instability. Since MMP-1 may degrade the major structural collagens of the plaque, expression of the protease by macrophages in regions critical to plaque integrity could contribute to plaque expansion, rupture, and hemorrhage.

Mechanism of activation of human neutrophil gelatinase B. Discriminating between the role of Ca2+ in activation and catalysis

Gelatinase B is a Zn(2+)- and Ca(2+)-dependent endopeptidase that is secreted from cells as an inactive proenzyme. The enzyme can be activated in vitro by organomercurial compounds and by trypsin. The role of Ca2+ in autoproteolytic processing initiated by 4-aminophenylmercuric acetate and trypsin and in catalytic activity of the activated enzyme was investigated by zymography and by kinetic analysis. Treatment of unglycosylated 57.5-kDa pro-gelatinase B with 4-aminophenylmercuric acetate (1 mM) in the absence of Ca2+ generated a 49-kDa inactive intermediate (E'), whereas a 41.5-kDa active species (E") was generated in the presence of Ca2+ (5 mM). Upon addition of Ca2+ to the reaction mixture of Ca(2+)-depleted E' or E" at 37 degrees C, E' showed a lag period in generation of the product as a function of time, but E" presented an immediate activity. The appearance of enzymatic activity of E' correlated with the generation of the E" species. NH2-terminal sequence analyses showed that E' and E" had the same NH2 termini, i.e. Met-75, suggesting that Ca(2+)-dependent removal of COOH terminus of E' is required for activation of the enzyme. Treatment of pro-gelatinase B with trypsin in the absence of Ca2+, led to degradation of the enzyme. In the presence of Ca2+, trypsin processed the pro-enzyme to a 40-kDa active species. In contrast to E", this active species did not require Ca2+ for activity. The Ca2+ dependence of E" activity was also abolished by treatment of the enzyme with trypsin. NH2-terminal sequence analysis indicated that amino acid residues 75-87 had been removed from the NH2 terminus of E" by trypsin, suggesting that these residues are responsible for the Ca(2+)-dependent activity of the enzyme. Removal of Ca2+ and catalytic Zn2+ inhibited the activities of both E" and trypsin-treated E". In the absence of Ca2+, either Zn2+, Co2+, Mn2+, or Cd2+ was able to restore the activity of trypsin-treated E". None of the divalent cations tested however, was able to stimulate the activity of E" in the absence of Ca2+. These experiments further suggest that binding of Ca2+ to E" or removal of the NH2-terminal residues of the enzyme by trypsin induces a conformational change in the protein and makes the active site of the enzyme accessible to various metal ions rendering the enzyme active.

Monoclonal antibodies against human collagenase and stromelysin

Mouse monoclonal antibodies against recombinant human fibroblast procollagenase and prostromelysin have been generated and characterized. The epitope-containing domains for the antibodies have been assigned based on their immunoreactivities against recombinant proenzymes, mature enzymes, truncated collagenases, proteolytic fragments of stromelysin, and chimeric molecules constructed from different domains of the two enzymes. These antibodies can be divided into four groups: (1) antibodies that recognize the truncated 19-kDa NH2-terminal collagenase, (2) antibodies that recognize the C-terminal domain of collagenase and stromelysin, (3) antibodies that recognize a 31-kDa NH2-terminal collagenase fragment, and (4) antibodies that recognize the 19-kDa NH2-fragment of stromelysin. The prostromelysin-specific antibody 11N13 is of particular interest; it neutralizes stromelysin activity in a stromelysin peptide substrate assay, with an IC50 value of 75 nM. MAb 11N13 may be useful for in vivo and in vitro studies to validate the roles of stromelysin in tumor cell invasion, metastasis, and connective tissue disorders.

Calcium ionophores decrease pericellular gelatinolytic activity via inhibition of 92-kDa gelatinase expression and decrease of 72-kDa gelatinase activation

To understand the roles of intracellular calcium levels on gelatinase/type IV collagenase expression, we analyzed the effects of calcium ionophores on the expression of 92- and 72-kDa gelatinases (MMP-9 and MMP-2) in human fibrosarcoma cells (HT-1080). Calcium ionophores ionomycin and A23187 reduced the levels of pericellular gelatinolytic activity in both untreated and phorbol 12-myristate 13-acetate (PMA) or tumor necrosis factor-alpha (TNF alpha)-stimulated cells as determined by degradation of radiolabeled gelatin. Gelatin zymography and immunoblotting revealed a dose-dependent decrease in the levels of secreted 92-kDa gelatinase, which was paralleled by a decrease of its mRNA. Treatment of cells with thapsigargin caused similar decreases of 92-kDa gelatinase mRNA and protein. The decrease of 92-kDa gelatinase expression was due to lower transcription rate as determined by transfection assays with 92-kDa gelatinase/luciferase construct. The expression of 72-kDa gelatinase was only slightly decreased by ionophores. Treatment of HT-1080 cells with PMA, TNF alpha, or concanavalin A resulted in the conversion of 72-kDa gelatinase proenzyme to its presumed 64- and 62-kDa active forms as determined by gelatin zymography and immunoblotting. Simultaneous treatment with the ionophores or thapsigargin resulted in inhibition of PMA-induced gelatinase activation. The expression of membrane-type matrix metalloproteinase, a potential activator of 72-kDa gelatinase, was not affected by ionophores. The results indicate that calcium ionophores decrease gelatinolysis by repressing both the expression of 92-kDa gelatinase and the activation of the 72-kDa gelatinase.

The metzincins--topological and sequential relations between the astacins, adamalysins, serralysins, and matrixins (collagenases) define a superfamily of zinc-peptidases

The three-dimensional structures of the zinc endopeptidases human neutrophil collagenase, adamalysin II from rattle snake venom, alkaline proteinase from Pseudomonas aeruginosa, and astacin from crayfish are topologically similar, with respect to a five-stranded beta-sheet and three alpha-helices arranged in typical sequential order. The four proteins exhibit the characteristic consensus motif HEXXHXXGXXH, whose three histidine residues are involved in binding of the catalytically essential zinc ion. Moreover, they all share a conserved methionine residue beneath the active site metal as part of a superimposable "Met-turn." This structural relationship is supported by a sequence alignment performed on the basis of topological equivalence showing faint but distinct sequential similarity. The alkaline proteinase is about equally distant (26% sequence identity) to both human neutrophil collagenase and astacin and a little further away from adamalysin II (17% identity). The pairs astacin/adamalysin II, astacin/human neutrophil collagenase, and adamalysin II/human neutrophil collagenase exhibit sequence identities of 16%, 14%, and 13%, respectively. Therefore, the corresponding four distinct families of zinc peptidases, the astacins, the matrix metalloproteinases (matrixins, collagenases), the adamalysins/reprolysins (snake venom proteinases/reproductive tract proteins), and the serralysins (large bacterial proteases from Serratia, Erwinia, and Pseudomonas) appear to have originated by divergent evolution from a common ancestor and form a superfamily of proteolytic enzymes for which the designation "metzincins" has been proposed. There is also a faint but significant structural relationship of the metzincins to the thermolysin-like enzymes, which share the truncated zinc-binding motif HEXXH and, moreover, similar topologies in their N-terminal domains.

Mechanism of cell surface activation of 72-kDa type IV collagenase. Isolation of the activated form of the membrane metalloprotease

Matrix metalloproteases are secreted by mammalian cells as zymogens and, upon activation, initiate tissue remodeling by proteolytic degradation of collagens and proteoglycans. Activation of the secreted proenzymes and interaction with their specific inhibitors determine the net enzymatic activity in the extracellular space. We have previously demonstrated that 72T4Cl can be activated by a plasma membrane-dependent mechanism specific for this enzyme. Here, we report purification of the membrane activator of 72T4Cl, which is a new metalloprotease identical to a recently cloned membrane-type matrix metalloprotease (MT-MMP). We demonstrate that activated MT-MMP acts as a cell surface tissue inhibitor of metalloprotease 2 (TIMP-2) receptor with Kd = 2.54 x 10(-9) M. The activator.TIMP-2 complex in turn acts as a receptor for 72T4Cl (Kd = 0.56 x 10(-9) M, binding to the carboxyl-end domain of the enzyme. Activation of 72T4Cl on the cell membrane provides a basic mechanism for spatially regulated extracellular proteolysis and presents a new target for prognosis and treatment of metastatic disease. The activation, purified as a tri-molecular complex of MT-MMP.TIMP2.carboxyl-end domain of 72T4Cl, is itself an activated form of MT-MMP, posing the following question: what is the mechanism of the activator's activation?

Role of phospholipase D in laminin-induced production of gelatinase A (MMP-2) in metastatic cells

Metastatic spread depends critically upon the invasiveness of tumor cells, i.e. their ability to breach basement membranes by elaborating and secreting specific proteolytic enzymes such as gelatinase A (MMP-2). Laminin is a major constituent of the extracellular matrix that can trigger production of MMP-2 in metastatic cells, but not in non-metastatic cells. The present study was designed to examine the role of phospholipase D (PLD) and its product, phosphatidic acid, in the intracellular signal transduction mechanisms that mediate induction of MMP-2 by laminin. Here we show that stimulation of tumor cells with laminin results in a time- and dose-dependent activation of PLD. Laminin-induced production of MMP-2 is attenuated by 1-butanol, a competitive substrate of PLD that reduces PLD-catalyzed production of PA. Moreover, phosphatidic acid itself can induce production of MMP-2 in metastatic tumor cells. MMP-2 can also be induced by exposing the cells to exogenous bacterial PLD. Elevated cellular phosphatidic acid induces MMP-2 in metastatic ras-transformed 3T3 fibroblasts but, like laminin, fails to do so in normal cells. These data indicate that laminin-induced activation of PLD and consequent generation of phosphatidic acid are involved in a signal propagation pathway leading to induction of MMP-2 and enhanced invasiveness of metastatic tumor cells.

Evidence of a direct relationship between neutrophil collagenase activity and periodontal tissue destruction in vivo: role of active enzyme in human periodontitis

To assess the temporal relationship between periodontal tissue destruction and the activity of collagenase, exudate from inflamed periodontal tissues was collected and latent and active collagenase activities were measured by a functional assay in a longitudinal cohort study. Comparisons were made between human subjects with either: 1) inflammation with a previous history of progressive loss of connective tissue and bone support (n = 14); 2) inflammation and previous history of bone loss but now clinically stable (n = 27); or 3) inflammation and no loss of bone support (n = 17). Experiments using specific enzyme inhibitors, blocking antibodies and SDS-PAGE fluorograph to identify the pattern of collagen substrate degradation demonstrated that the collagenase activity was derived from neutrophils and not from bacteria or other host cells. Active collagenase activity pooled from 6 sites per subject was respectively 5 and 6-fold higher in the group with progressive loss of connective tissue compared to the groups with either inflamed tissues alone or with inflammation and previous bone loss. In contrast, latent collagenase was increased up to 2 fold higher in the group with inflammation but no bone loss compared to the group with progressive lesions. Moreover, the ratio of active to total collagenase activity was 50% higher in the group with progressive lesions. Although in all subjects successive measurements of site-specific active collagenase 1 month apart demonstrated wide variation (r < 0.50), only in sites with progressive periodontal destruction was there significant increase of active collagenase with time (1.28 x 10(-4) collagenase units per day). There were also sharp elevations in active enzyme level at the time of detection of loss of connective tissue attachment in specific sites of 8 subjects. At the time of detection of connective tissue attachment loss, there was an overall 40% increase of pooled active collagenase activity in all subjects with progressive loss of connective tissue compared to pre-breakdown sampling times. These data provide strong in vivo evidence for a direct role of active neutrophil collagenase in the pathological destruction of periodontal connective tissue.

Reciprocated matrix metalloproteinase activation: a process performed by interstitial collagenase and progelatinase A

Gelatinase A, a member of the matrix metalloproteinase (MMP) family, is secreted possessing an 80 amino acid N-terminal propeptide that must be removed in order to generate the active enzyme. Purified progelatinase A was activated to 38% of maximum by a 6 h incubation at 37 degrees C with equimolar concentrations of trypsin-activated interstitial collagenase (another MMP). The increase in activity was accompanied by cleavage of the M(r) 72,000 progelatinase A to the M(r) 66,000 active enzyme that has Y81 as its N-terminus. At low concentrations, progelatinase A was processed via an inactive intermediate, suggesting that its activation is a biphasic process. This was confirmed by the action of collagenase on proE375-->A (a mutant of progelatinase A that cannot become active) because, in this instance, only an M(r) 68,000 species with L38 as the N-terminus was produced. The remaining propeptide amino acids to Y81 could be readily removed by added active gelatinase A, indicating that collagenase works by generating an intermediate that is susceptible to autolytic activation. Although relatively slow, the rate of activation could be increased approximately 10-fold by the addition of 100 micrograms/mL heparin. This binds to the C-terminal domain of collagenase and progelatinase A and presumably acts as a template that positions the reactants close to one another. Collagenase activated by trypsin retains 8 or 14 amino acids of its propeptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Host enzymes in gingival crevicular fluid as diagnostic indicators of periodontitis

Host responses to periodontal infections include the production of several families of enzymes that are released by stromal, epithelial or inflammatory cells. Study of these enzymes in gingival crevicular fluid may lead to insights into pathogenesis and may provide a rational basis for the development of novel diagnostic tests. However, analogous to other diagnostic interventions in dentistry and medicine, validation of host enzymes as diagnostic indicators is dependent on clear-cut demonstrations of the identity of the enzyme, reproducibility, diagnostic accuracy and clinical utility. The enzyme of interest should be readily measured over a broad range of disease severity and in varied clinical settings. Ideally, the enzyme should also be an essential component of proposed pathogenic mechanisms. In this context, the connective tissue matrix degrading enzymes elastase, collagenase and gelatinase are promising because of their apparently central role in periodontal attachment loss and disease progression. Sensitive and specific assays are also available to quantify these enzymes. Other work on enzymes associated with cell death (aspartate aminotransferase, lactate dehydrogenase) and several neutrophil lysosomal enzymes (beta glucuronidase, arylsulphatase, cathepsins) has demonstrated positive associations between enzyme levels and attachment loss and inflammation. While numerous cross-sectional studies have indicated that the levels of hydrolytic enzymes in gingival crevicular fluid parallel the severity of periodontal lesions, there are much less data on reproducibility, diagnostic accuracy and clinical utility in longitudinal studies. As appropriate study design is an essential prerequisite for establishing the efficacy of host enzymes as diagnostic tests, future clinical investigations should include: (1) individuals who would most likely benefit by early diagnosis, i.e., rapidly progressive and recurrent periodontitis cases; (2) longitudinal, cohort study designs to show that attachment loss is temporally linked with large increases in enzyme activity; (3) the use of a battery of tests to overcome intrinsic problems of low predictive values when prevalence of active disease is low. In the final analysis, the utility of host enzymes as diagnostic indicators will need to be examined in randomized controlled trials in which the question is asked: are patients better off as a result of testing?