SV40-transformed Human Lung Fibroblasts Secrete a 92-kDa Type IV Collagenase Which Is Identical to That Secreted by Normal Human Macrophages

Characterization of the major matrix degrading metalloproteinase of human corneal stroma. Evidence for an enzyme/inhibitor complex

The human cornea is an avascular, highly organized tissue with the unique property of transparency. While the extracellular matrices of this tissue are composed of a variety of collagen types, proteoglycans and glycoproteins, little is known of the normal degradation and remodeling of these components. We examined the capacity of organ cultured human ocular tissues to produce and secrete metalloproteinases, a family of related enzymes capable of digesting a variety of extracellular matrices. We demonstrated that while enzymatic activities similar to type I collagenase and stromelysin are produced, the predominant activities of the corneal stroma and keratocyte cultures are a 68-kDa gelatinase. In our hands, this enzyme does not appear to be induced significantly by phorbol esters in vitro. In addition, this enzyme appears to be secreted as a complex with a 21-kDa protein that functions as an enzymatic inhibitor. Moreover, the keratocytes also produce a 28-kDa inhibitor which has similar properties to tissue inhibitor of metalloproteinase (TIMP).

Matrix metalloproteinase 2 from human rheumatoid synovial fibroblasts. Purification and activation of the precursor and enzymic properties

Human rheumatoid synovial cells in culture secrete at least three related metalloproteinases that digest extracellular matrix macromolecules. One of them, termed matrix metalloproteinase 2 (MMP-2), has been purified as an inactive zymogen (proMMP-2). The final product is homogeneous on SDS/PAGE with Mr = 72,000 under reducing conditions. The NH2-terminal sequence of proMMP-2 is Ala-Pro-Ser-Pro-Ile-Ile-Lys-Phe-Pro-Gly-Asp-Val-Ala-Pro-Lys-Thr, which is identical to that of the so-called '72-kDa type IV collagenase/gelatinase'. The zymogen can be rapidly activated by 4-aminophenylmercuric acetate to an active form of MMP-2 with Mr = 67,000, and the new NH2-terminal generated is Tyr-Asn-Phe-Phe-Pro-Arg-Lys-Pro-Lys-Trp-Asp-Lys-Asn-Gln-Ile. However, following 4-aminophenylmercuric acetate activation, MMP-2 is gradually inactivated by autolysis. Nine endopeptidases (trypsin, chymotrypsin, plasmin, plasma kallikrein, thrombin, neutrophil elastase, cathepsin G, matrix metalloproteinase 3, and thermolysin) were tested for their abilities to activate proMMP-2, but none had this ability. This contrasts with the proteolytic activation of proMMP-1 (procollagenase) and proMMP-3 (prostromelysin). The optimal activity of MMP-2 against azocoll is around pH 8.5, but about 50% of activity is retained at pH 6.5. Enzymic activity is inhibited by EDTA, 1,10-phenanthroline or tissue inhibitor of metalloproteinases, but not by inhibitors of serine, cysteine or aspartic proteinases. MMP-2 digests gelatin, fibronectin, laminin, and collagen type V, and to a lesser extent type IV collagen, cartilage proteoglycan and elastin. Comparative studies on digestion of collagen types IV and V by MMP-2 and MMP-3 (stromelysin) indicate that MMP-3 degrades type IV collagen more readily than MMP-2, while MMP-2 digests type V collagen effectively. Biosynthetic studies of MMPs using cultured human rheumatoid synovial fibroblasts indicated that the production of both proMMP-1 and proMMP-3 is negligible but it is greatly enhanced by the treatment with rabbit-macrophage-conditioned medium, whereas the synthesis of proMMP-2 is constitutively expressed by these cells and is not significantly affected by the treatment. This suggests that the physiological and/or pathological role of MMP-2 and its site of action may be different from those of MMP-1 and MMP-3.

A novel metalloproteinase gene specifically expressed in stromal cells of breast carcinomas

A gene has been identified that is expressed specifically in stromal cells surrounding invasive breast carcinomas. On the basis of its sequence, the product of this gene, named stromelysin-3, is a new member of the family of metalloproteinase enzymes which degrade the extracellular matrix. The suggestion is that stromelysin-3 is one of the stroma-derived factors that have long been postulated to play an important part in progression of epithelial malignancies.

Type IV collagenases in tumor invasion and metastasis

The invasion and metastasis of cancer cells is a complex multistep process involving destruction of basement membranes as an early event in the metastatic cascade. Recent evidence implicates secreted matrix metalloproteinase enzymes, such as type IV collagenases, as playing a central role in this tumor cell mediated extracellular matrix proteolysis. Two distinct type IV collagenase enzymes are now recognized. Immunohistochemical and biochemical studies of several human tumors show correlations between invasive potential and the 72 kDa type IV collagenase enzyme. Studies in rodent tumor models suggest that the 92 kDa type IV collagenase may play an important role in these models, but data on human tumors and human tumor tissue is lacking. Evidence suggest that the regulation of the 72 kDa type IV collagenase enzyme activity may occur at many levels, including transcriptional mechanisms, extracellular activation of latent enzyme and specific inhibitors of active enzyme. Thus the invasion of human tumor cells through basement membranes may be the result of net type IV collagenolytic activity that is the result of a balance of activated enzyme species and inhibitors.

Characterization of 58-kilodalton human neutrophil collagenase: comparison with human fibroblast collagenase

A series of experiments has been carried out to characterize 58-kDa human neutrophil collagenase (HNC) and compare it with human fibroblast collagenase (HFC). N-Terminal sequencing of latent and spontaneously activated HNC shows that it is a distinct collagenase that is homologous to HFC and other members of the matrix metalloproteinase gene family. Activation occurs autolytically by hydrolysis of an M-L bond at a locus homologous to the Q80-F81-V82-L83 autolytic activation site of HFC. This releases a 16-residue propeptide believed to contain the "cysteine switch" residue required for latency. Polyclonal antibody raised against HNC cross-reacts with HFC but with none of the other major human matrix metalloproteinases examined. Treatment of HNC with endoglycosidase F or N-glycosidase F indicates that it is glycosylated at multiple sites. The deglycosylated latent and spontaneously activated enzymes have molecular weights of approximately 44K and 42K, respectively. Differences in the carbohydrate processing of HFC and HNC may determine why HFC is a secreted protein while HNC is stored in intracellular granules. The kinetic parameters kcat and KM for the hydrolysis of the interstitial collagen types I, II, and III in solution by both collagenases have been determined. The strong preferences of HNC for type I collagen and of HFC for type III collagen found in earlier studies have been confirmed. The preference of HNC for type I over type III collagen is almost abolished when fibrillar collagens are used as substrates, but the preference for HFC for type III over type I collagen is only partially decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

The collagen-binding site of type-II units of bovine seminal fluid protein PDC-109 and fibronectin

A single type-II domain has been isolated by limited proteolysis of the collagen-binding bovine seminal fluid protein, PDC-109. The 45-residue fragment corresponding to the second type-II domain of the parent molecule was found to have retained affinity for immobilized collagen, indicating that this minidomain carries critical regions of the collagen-binding site. Studies on various fragments of fibronectin have also implicated the two type-II units of this molecule in collagen-binding. In the present work we have found that type-II domains of human fibronectin, expressed in Escherichia coli as beta-galactosidase fusion proteins, bind specifically to immobilized collagen.

Immunoassays for the detection of human collagenase, stromelysin, tissue inhibitor of metalloproteinases (TIMP) and enzyme-inhibitor complexes

Immunoassays have been developed for human collagenase, stromelysin, tissue inhibitor of metalloproteinases (TIMP) and TIMP complexed with both of the active enzymes. Selection of antibodies of defined specificity enabled measurement of both the pro and active forms of the metalloproteinase. Free TIMP was quantified by the selection of a monoclonal antibody which did not recognise TIMP when complexed with metalloproteinases. Detection of enzyme-inhibitor complexes was achieved by capturing the TIMP component of the complex and revealing the metalloenzyme using specific antibodies.

Human hepatoma cells produce an 85 kDa gelatinase regulated by phorbol 12-myristate 13-acetate

Several human cell lines were studied for the production of gelatinases. Diploid fibroblasts, the melanoma cell line Bowes, the MG-63 osteosarcoma cell line and the human hepatoma cell line Malavu all constitutively produced a 67 kDa gelatinase. Gelatinolytic enzymes were quantified by a sensitive zymographic substrate conversion assay. Upon induction with phorbol 12-myristate 13-acetate (PMA), the human hepatoma cell line secreted considerable amounts of an 85 kDa gelatinase activity. The induction process was time- and dose-dependent. It represented a true increase in production per individual cell and was associated by a marked change of the cell morphology. The effect of various proteinase inhibitors and the maximal activity of the enzyme near neutral pH demonstrate that it is a neutral metalloproteinase. Characterization studies showed the 85 kDa gelatinase to be transformed to lower molecular weight, active forms by treatment with p-aminophenylmercuric acetate (APMA) or trypsin.

Induction and stimulation of 92-kDa gelatinase/type IV collagenase production in osteosarcoma and fibrosarcoma cell lines by tumor necrosis factor alpha

Production of a 92-kDa gelatinase/type IV collagenase and tissue inhibitor of metalloproteinases (TIMP) was investigated with human sarcoma cell lines. Among the cytokines and growth factors examined, only human recombinant tumor necrosis factor alpha (TNF alpha) induced and stimulated the proteinase with concomitant increase in TIMP expression, but matrix metalloproteinase 2 (72-kDa gelatinase/type IV collagenase) expression was unchanged. These data suggest that gene expression of the two metalloproteinases is regulated in a different fashion and TNF alpha may be important to allow cancer cells to be more invasive and metastatic.

Modulation of type-IV collagenase activity and invasive behavior of metastatic human melanoma (A2058) cells in vitro by monoclonal antibodies to type-IV collagenase

Monoclonal antibodies (MAbs) against human type-IV collagenase were developed and used for studies on enzyme activity and tumor-cell invasion in vitro. Fifteen MAb clones were generated against the enzyme purified form serum-free culture medium of human melanoma cells (A2058). Five clones affecting the activity of type-IV collagenase were selected for further characterization. All the selected clones could be used for a single-step purification of type-IV collagenase using IgG-Sepharose affinity columns. One of the antibodies activated the enzyme when 3H-proline-labelled type-IV collagen was used as substrate. The activation was dependent on the enzyme antibody ratio. Four clones caused more than 30% inhibition of the activity, maximal inhibition being 50%. Interestingly, the same antibody which activated the enzyme also increased the invasion of A2058 cells through a reconstituted basement membrane in an in vitro invasion assay. The 4 inhibitory antibodies decreased the penetration of A2058 cells through the reconstituted basement membrane. The results strongly support previous findings about the importance of type-IV collagenase in tumor-cell invasion.

Tissue inhibitor of metalloproteinases from human bone marrow stromal cell line KM 102 has erythroid-potentiating activity, suggesting its possibly bifunctional role in the hematopoietic microenvironment

In this study, we demonstrated that tissue inhibitor of metalloproteinases (TIMP) produced by human bone marrow stromal cell line KM-102 had erythroid-potentiating activity (EPA) which stimulates the proliferation of erythroid progenitor cells. We, then, propose a scheme for the bifunctional role of TIMP/EPA in hematopoietic microenvironment, that is, the maintenance of the integrity of bone marrow matrix and the proliferation of erythroid progenitor cells proceeding on the matrix.

Extraction of type-IV collagenase/gelatinase from plasma membranes of human cancer cells

Tumor proteinases are considered to be important in the process of cancer invasion and metastasis. We have proposed that the surface membrane localization of these proteinases places them in an optimal site to facilitate the invasion of surrounding extracellular matrix. In this study, we have used the organic solvent, n-butanol, and the detergent, n-octyl-glucoside, to sequentially extract metalloproteinases from crude plasma membranes of human RWP-I pancreatic cancer cells. Anion exchange chromatography and gel permeation chromatography were employed to further purify enzymes with the capacity to degrade gelatin, type-IV collagen, and carboxymethylated transferrin. Gelatin zymography was used to demonstrate proteinase bands of 92, 70 and 62-kDa. Immunoblotting of solubilized, partially purified pancreatic cancer plasma membrane proteins using polyclonal rabbit antibodies, which have specificity for type-IV collagenase/gelatinase, resulted in the recognition of a 70-kDa protein, but not the 92-kDa gelatinase. A type-IV collagenase/gelatinase of 68-kDa was similarly identified in A2058 human melanoma cancer cell plasma membranes.

Secretion and glycosylation of rabbit macrophage type V collagenase

Cultures of freshly isolated rabbit alveolar macrophages were used to study the synthesis, secretion, and glycosylation of type V collagenase. Cells were pulse-labeled with [35S-]methionine for 15 minutes followed by a chase with cold methionine for various time periods. Type V collagenase was identified in the culture supernatants and cell lysates by immunoprecipitation with a specific antiserum. Within 10 minutes of chase, an 82-kDa protein was found in the cell lysates. This protein was subsequently processed to a 92-kDa protein without identifiable intermediate forms. By 60 minutes of chase, intracellular radioactivity was no longer detectable. The larger protein could be detected within 20 minutes in the culture supernatants and accumulated in the medium for 60 minutes of chase time. Only the 92-kDa form was seen in the supernatants and the proteinase was secreted without intracellular storage or membrane association. Treatment of the 92-kDa proteinase with an enzyme which specifically removes N-linked carbohydrates resulted in an apparent reduction in molecular mass of approximately 10 kDa. Deglycosylation of the proteinase did not result in an apparent loss of activity. Thus, it was concluded that macrophage type V collagenase is synthesized as an 82-kDa polypeptide which is glycosylated by N-linkage and secreted.

Metalloproteinases and their inhibitors in matrix remodeling

The matrix metalloproteinases are a tightly regulated family of enzymes that degrade extracellular matrix and basement membrane components. Recent evidence suggests that these proteases and their specific inhibitors play important roles in normal developmental processes and in pathological conditions. Interestingly, experiments designed to improve our understanding of metalloproteinase regulation have also resulted in new insights into mechanisms by which growth factors and proto-oncogenes may regulate biological processes.

Regulation of gene expression by tumor promoters

Tumor promoters change the program of genes expressed in cells in culture and in the multicellular organism. The growing list of genes that are induced or repressed includes protooncogenes, transcription factors, secreted proteases and viruses. Most of the regulation is at the level of transcription. Several of the cis-acting promoter elements mediating regulation, the transcription factors binding to these elements and their post-translational activation, as well as some of the initial steps of the interaction of cells with tumor promoters have been characterized. The components of the signal transduction chain to the nucleus are, however, still unknown. Mutant and inhibitor studies suggest that the activation or inactivation of certain genes constitute the basis for the development of the tumor promotion phenotype.