92-kD type IV collagenase mediates invasion of human cytotrophoblasts

The specialized interaction between embryonic and maternal tissues is unique to mammalian development. This interaction begins with invasion of the uterus by the first differentiated embryonic cells, the trophoblasts, and culminates in formation of the placenta. The transient tumor-like behavior of cytotrophoblasts, which peaks early in pregnancy, is developmentally regulated. Likewise, in culture only early-gestation human cytotrophoblasts invade a basement membrane-like substrate. These invasive cells synthesize both metalloproteinases and urokinase-type plasminogen activator. Metalloproteinase inhibitors and a function-perturbing antibody specific for the 92-kD type IV collagen-degrading metalloproteinase completely inhibited cytotrophoblast invasion, whereas inhibitors of the plasminogen activator system had only a partial (20-40%) inhibitory effect. We conclude that the 92-kD type IV collagenase is critical for cytotrophoblast invasion.     

Cleavage of type VII collagen by interstitial collagenase and type IV collagenase (gelatinase) derived from human skin

Type VII collagen is the major structural protein of anchoring fibrils, which are believed to be critical for epidermal-dermal adhesion in the basement membrane zone of the skin. To elucidate possible mechanisms for the turnover of this protein, we examined the capacities of two proteases, human skin collagenase, which degrades interstitial collagens, and a protease with gelatinolytic and type IV collagenase activities, to cleave type VII collagen. At temperatures below the denaturation temperature, pepsin cleaves type VII collagen into products of approximately 95 and approximately 75 kDa. Human skin collagenase cleaved type VII collagen into two stable fragments of approximately 83 and approximately 80 kDa, and the type IV collagenase (gelatinase) produced a broad band of approximately 80 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cleavage of type VII collagen was linear with time and enzyme concentration for both enzymes. Although the Km values were similar for both enzymes, the catalytic rate of cleavage by type IV collagenase is much faster than by interstitial collagenase, and shows a greater rate of increase with increasing temperature. Sequence analysis of the cleavage products from both enzymes showed typical collagenous sequences, indicating a relaxation in the helical part of the type VII collagen molecule at physiological temperature which makes it susceptible to gelatinolytic degradation. Interstitial collagenase from both normal skin cells and cells from patients with recessive dystrophic epidermolysis bullosa, a severe hereditary blistering disease in which both an anchoring fibril defect and excessive production of collagenase can be observed, produced identical cleavage products from type VII collagen. These data suggest a pathophysiological link between increased enzyme levels and the observed decrease or absence of anchoring fibrils.     

Transforming growth factor-beta 1 up-regulates type IV collagenase expression in cultured human keratinocytes.

During the wound healing process lysis of basement membranes precedes keratinocyte migration into the wound bed. We studied, in vitro, whether this degradation of basement membranes could be regulated by transforming growth factor-beta 1 (TGF-beta 1), which is known to accelerate wound healing in vivo. Transforming growth factor-beta 1 was found to increase the expression of both 92- and 72-kDa type IV collagenases (gelatinases) in cultured human mucosal and dermal keratinocytes. The 92-kDa enzyme predominated in both unstimulated and stimulated cultures. The 92-kDa form was stimulated over 5-fold, and the other form by a factor of 2-3. This increase in the synthesis of type IV collagenases was associated with a marked increase in the mRNA levels of these enzymes as well. The induction of the 92-kDa enzyme was similar in culture medium containing either 0.15 or 1.2 mM calcium chloride. Rat mucosal keratinocytes secreted only 92-kDa type IV collagenase, the secretion of which was not regulated by TGF-beta 1. Also, TGF-beta 1 did not cause any significant induction (maximum about 1.2-fold) of either type IV collagenase in human gingival fibroblasts. The induction levels of both collagenases in human keratinocytes were independent of the type of the extracellular matrix the cells were grown on. However, the basement membrane matrix (Matrigel) activated about half of the 92-kDa type to its 84-kDa active form. The data suggest that TGF-beta 1 has a specific function in up-regulating the expression of type IV collagenases in human keratinocytes, offering a possible explanation of how keratinocytes detach from basement membranes prior to the migration over the wound bed.     

Activation of the 92 kDa type IV collagenase by tissue kallikrein

Type IV collagenases are secreted as latent 92 and 72 kDa proenzymes which are then activated extracellularly. The mechanisms by which they are activated in vivo are not clear. We have studied the activation of porcine endothelial cell type IV collagenases by tissue and plasma kallikrein, and found that tissue kallikrein was a very efficient activator of the 92 kDa type IV collagenase. Enzyme cleavage was observed at concentrations of tissue kallikrein as low as 0.1 μg/ml. Plasma kallikrein had no effect. By comparison, plasmin, which has been proposed to be the physiological activator of interstitial collagenase and stromelysin, and elastase were much less effective, and high concentrations (plasmin at 100–200 μg/ml and elastase at 20 μg/ml) were required to cause only a limited cleavage which was not associated with an increase in activity, as observed by the gelatin-gel lysis assay. In addition tissue kallikrein was found by immunohistochemistry to be present in the extracellular matrix of the intima of porcine aortic vessel wall. These findings suggest that tissue kallikrein can be a potential activator of the 92 kDa type IV collagenase in vivo. © 1993 Wiley-Liss, Inc.     

Laminin increases the release of type IV collagenase from malignant cells

We have studied the effect of laminin on type IV collagenolytic activity elaborated by malignant cells in culture. Laminin (at concentrations of 4-8 micrograms/ml) added to serum-free culture supernatants of subconfluent A2058 human melanoma cells significantly increased the release of the type IV collagenolytic activity (200-300%). The induction of type IV collagenase was more pronounced (580%) using a fragment of laminin which binds to the cell surface laminin receptor. A monoclonal antibody against the human laminin receptor blocked the effect of laminin on type IV collagenase, suggesting that occupation of the laminin receptor may be necessary for the effect. Increase in the type IV collagenolytic activity mediated by laminin was also demonstrated in two other malignant cell lines, HT fibrosarcoma (168%) and mouse melanoma (B16-F10) (271%). The increase in type IV collagenase was found to be specific for laminin because another cell-binding matrix protein, fibronectin, did not have any effect, and epidermal growth factor and transferrin actually decreased the type IV collagenase in human melanoma culture medium (epidermal growth factor, 50% at 20 ng/ml; and transferrin, 20% at 10 micrograms/ml). These studies suggest that tumor cell binding to laminin, which comprises the first step of basement membrane invasion, will induce the second step, namely the collagenolytic dissolution of the basement membrane.     

Anti-integrin antibodies induce type IV collagenase expression in keratinocytes

During wound healing, pericellular proteolysis is thought to be essential for the detachment of keratinocytes from basement membrane and in their migration into the wound bed. We have characterized integrin-type cell adhesion/migration receptors in human mucosal keratinocytes and examined their function in the regulation of type IV collagenase gene expression. Two major integrins of the β1 class, α2β1 and αβ1, were found to function as collagen and fibronectin receptors, respectively. Antibodies against β1 and α3 integrin subunits were found to stimulate the expression of the 92 kDa type IV collagenase severalfold in a dosedependent manner. Keratinocytes expressed also the 72 kDa type IV collagenase, the synthesis of which remained, however, unchanged in keratinocytes treated with anti-integrin antibodies. Stimulation of 92 kDa enzyme was found to be caused directly by antibody binding to integrins, since Fab-fragments of anti-β1 antibodies alone were able to induce collagenase expression in the absence of secondary, clustering antibodies. Antibodies against α2β1 integrin caused no stimulation. Keratinocytes seeded on different substrata (plastic, collagen, fibronectin, laminin, or vitronectin) showed equal induction of type IV collagenase expression. Expression of 92 kDa type IV collagenase could not be induced by peptides (GRGDS, GRGES), proteins (fibronectin, laminin, fibrinogen., albumin), or antibodies to fibronectin. We suggest that proteolytic processes around keratinocytes can be regulated by extracellular factors signalling through integrin-type receptors. © 1993 Wiley-Liss, Inc.     

The proteolytic activity of the recombinant cryptic human fibronectin type IV collagenase from E. coli expression

Human plasma fibronectin (pFN) contains a cryptic metalloprotease present in the collagen-binding domain. The enzyme could be generated and activated in the presence of Ca²⁺ from the purified 70-kDa pFN fragment produced by cathepsin D digestion. In this work we cloned and expressed the metalloprotease, designated FN type IV collagenase (FnColA), and a truncated variant (FnColB) in E. coli. The recombinant pFN protein fragment was isolated from inclusion bodies, and subjected to folding and autocatalytic degradation in the presence of Ca²⁺, and yielded an active enzyme capable of digesting gelatin, helical type II and type IV collagen, - and -casein, insulin b-chain, and a synthetic Mca-peptide. In contrast, isolated plasma fibronectin, type I collagen, and the DNP-peptide were no substrates. Both catalytically active recombinant pFN fragments were efficiently inhibited by EDTA, and batimastat, and, in contrast to the glycosylated enzyme isolated from plasma fibronectin, were also inhibited by TIMP-2.     

Structure of the human type I DNA topoisomerase gene

We describe the molecular organization of the human gene coding for type I DNA topoisomerase. The coding sequence is split into 21 exons distributed over at least 85 kilobase pairs (kb) of human genomic DNA. The sizes of the 20 introns vary widely between 0.2 and at least 30 kb and all contain the sequence elements known to be required for pre-mRNA splicing. Several of the intron sequences separate exons encoding parts of the enzyme that are highly conserved between human and yeast suggesting that at least some of the exons may code for individual, structurally, or functionally important domains of the enzyme. We also describe the promoter sequence of the human topoisomerase I gene and show that it is composed of distinct functional elements.     

On the structure and chromosome location of the 72- and 92-kDa human type IV collagenase genes.

The 72- and 92-kDa type IV collagenases are members of a group of secreted zinc metalloproteases. Two members of this family, collagenase and stromelysin, have previously been localized to the long arm of chromosome 11. Here we assign both of the two type IV collagenase genes to human chromosome 16. By sequencing, the 72-kDa gene is shown to consist of 13 exons, 3 more than have been reported for the other members of this gene family. The extra exons encode the amino acids of the fibronectin-like domain which has so far been found in only the 72- and 92-kDa type IV collagenase. The evolutionary relationship among the members of this gene family is discussed.     

Alanine scanning mutagenesis and functional analysis of the fibronectin-like collagen-binding domain from human 92-kDa type IV collagenase.

The human 72-kDa (CLG4A) and 92-kDa (CLG4B) type IV collagenases contain a domain consisting of three contiguous copies of the fibronectin (FN)-derived type II homology unit (T2HU), T2HU-1, T2HU-2, and T2HU-3. To investigate the functional role of this domain, we have constructed plasmids expressing beta-galactosidase fusion proteins with one or more of the CLG4B-derived T2HU. The gelatin binding assays demonstrate that a single copy of T2HU-2 renders beta-galactosidase capable of binding gelatin. The three repeats, however, differ dramatically in their capacity to bind gelatin, with T2HU-1 and T2HU-3 having significantly less binding activity than T2HU-2. Using alanine scanning mutagenesis we have defined the amino acid residues (Arg307, Asp309, Asn319, Tyr320, Asp323) that are critical for gelatin binding of T2HU-2. The low gelatin binding of T2HU-1 compared to T2HU-2 was traced to the non-conserved residues Ala228-Ala and Leu253-Pro. The results suggest that the gelatin binding of the type IV collagenase proenzyme is mediated by the FN-like domain, although the presence of another gelatin-binding site cannot be excluded. The FN domain-mediated binding, however, is not a rate-limiting step in the hydrolysis of gelatin by the enzyme.     

Interleukin 4 inhibition of prostaglandin E2 synthesis blocks interstitial collagenase and 92-kDa type IV collagenase/gelatinase production by human monocytes.

Activation of human monocytes results in the production of interstitial collagenase through a prostaglandin E2 (PGE2)-cAMP-dependent pathway. Inasmuch as interleukin 4 (IL-4) has been shown to inhibit PGE2 synthesis by monocytes, we examined the effect of IL-4 on the production of human monocyte interstitial collagenase. Additionally, we also assessed the effect of IL-4 on the production of 92-kDa type IV collagenase/gelatinase and tissue inhibitor of metalloproteinase-1 (TIMP-1) by monocytes. The inhibition of PGE2 synthesis by IL-4 resulted in decreased interstitial collagenase protein and activity that could be restored by exogenous PGE2 or dibutyryl cyclic AMP (Bt2cAMP). IL-4 also suppressed ConA-stimulated 92-kDa type IV collagenase/gelatinase protein and zymogram enzyme activity that could be reversed by exogenous PGE2 or Bt2cAMP. Moreover, indomethacin suppressed the ConA-induced production of 92-kDa type IV collagenase/gelatinase. These data demonstrate that, like monocyte interstitial collagenase, the conA-inducible monocyte 92-kDa type IV collagenase/gelatinase is regulated through a PGE2-mediated cAMP-dependent pathway. In contrast to ConA stimulation, unstimulated monocytes released low levels of 92-kDa type IV collagenase/gelatinase that were not affected by IL-4, PGE2, or Bt2cAMP, indicating that basal production of this enzyme is PGE2-cAMP independent. IL-4 inhibition of both collagenases was not a result of increased TIMP expression since Western analysis of 28.5-kDa TIMP-1 revealed that IL-4 did not alter the increased TIMP-1 protein in response to ConA. These data indicate that IL-4 may function in natural host regulation of connective tissue damage by monocytes.     

Isolation and characterisation of a chicken gelatinase (type IV collagenase).

The proform of chick gelatinase (type IV collagenase) was isolated and purified to a high specific activity of 12,071 U/mg from cultured embryonic skin fibroblasts stimulated with cytochalasin-B. The enzyme was activated in the presence of 4-aminophenylmercuric acetate with a fall in molecular weight from 66,000-58,000 on non-reducing polyacrylamide gel electrophoresis and was active over the pH range of 6.0-8.9 against a number of substrates. Further biochemical characterisation showed that the organomercurial activated form of the enzyme behaved like a typical mammalian gelatinase, actively degrading gelatin, soluble type I collagen, collagenase generated type I fragments, type IV collagen (producing 3/4 and 1/4 fragments) and type V collagen, whilst having little effect on laminin. The enzyme was inhibited by metal chelators such as EDTA and 1,10-phenanthroline, but not by inhibitors is suggested that this may be TIMP-2. An antiserum was raised to the proenzyme and was found to localise intra- and extra-cellularly in both tissue sections and cell cultures.     

Proteolytic processing of the 72,000-Da type IV collagenase by urokinase plasminogen activator.

Regulation of the activity of proteolytic enzymes is of major importance in the turnover of connective tissues. The search for physiologically relevant activation mechanisms of principal tissue-degrading enzymes, e.g., metalloproteinases, has therefore been of wide interest. We have now studied whether the initiating factor of the fibrinolytic system, urokinase plasminogen activator (u-PA), may also function in the early steps of activation of one of the metalloproteinases, the M(r) 72,000 gelatinase/type IV collagenase produced by cultured fibroblasts. Treatment of the secreted M(r) 72,000 proteinase by u-PA yielded a cleavage product of M(r) 62,000 as revealed by fluorography of radioactively labeled proteins as well as by gelatin zymography SDS-PAGE gels. The u-PA-catalyzed cleavage of the M(r) 72,000 proteinase was blocked by anti-u-PA antibodies, but was unaffected by the plasmin inhibitor aprotinin, thus indicating a specific action for the activator. On the contrary, the tissue activator of plasminogen, t-PA, did not cleave the type IV collagenase in similar assays. u-PA-catalyzed cleavage of recombinant type IV collagenase, produced in a baculovirus expression system, yielded a similar M(r) 62,000 activity in gelatinolysis assay. Zymograms of the isolated pericellular matrices of cultured fibroblasts also revealed M(r) 72,000 gelatinolytic polypeptide that was converted to an M(r) 62,000 form by u-PA. Both polypeptides were recognized in immunoblotting by antibodies against the gelatinase/type IV collagenase, suggesting immunological identity with the secreted enzyme. Thus the M(r) 72,000 gelatinase/type IV collagenase is not only secreted, but also deposited into the pericellular fibroblast matrix, and both forms are substrates for u-PA. The results suggest a new potential role for u-PA as a direct regulator of metalloproteinase-mediated extracellular proteolysis via the cleavage of the M(r) 72,000 gelatinase/type IV collagenase to an M(r) 62,000 form.     

Production and characterization of a human single-chain Fv to collagenase IV

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Monoclonal antibodies to type IV collagenase recognize a protein with limited sequence homology to interstitial collagenase and stromelysin

Type IV collagenase is a metalloproteinase associated with metastatic tumor cells. It specifically cleaves the triple helical basement membrane (type IV) collagen molecule at a single site. Monoclonal antibodies which block the activity of the human type IV collagenase were developed and used to purify this antigen. The purified type IV collagenase was partially sequenced following cyanogen bromide and trypsin cleavage. The amino acid sequence of the human type IV collagenase fragments revealed a region homologous to the human interstitial collagenase and stromelysin. However, several sequences in type IV collagenase were identified which are distinct from the latter. Polyclonal antibodies were raised against a synthetic peptide derived from such a sequence. Following affinity purification, the antibodies recognized the denatured human type IV collagenase in Western immunoblotting. These data indicate that type IV collagenase is a distinct member of a general family of metalloproteinases.