In the skin, expression of several matrix metalloproteinases (MMPs) occurs in response to tissue injury, tumorigenesis, angiogenesis, apoptosis, and inflammation. The recently cloned MMP-21 has been ...implicated in skin development and various epithelial cancers. In this study, we found that it is also expressed by differentiated keratinocytes (KCs) in various benign skin disorders, in which it was not associated with KC apoptosis or proliferation, and in organotypic cultures. Furthermore, MMP-21 was induced in keratinocytes in association with increased calcium and presence of the differentiation marker filaggrin. In stably transfected A431 and HEK293 cell lines, MMP-21 increased invasion of cells but did not associate with increased apoptosis, proliferation, or epithelial-to-mesenchymal transition. Of various agents tested in HaCaT cell cultures, only retinoic acid (10-6M) and staurosporine (2.5 × 10-8M) upregulated MMP-21 mRNA and protein expression, whereas tumor promoters, hormones, or dexamethasone were without effect. Our results suggest that MMP-21 may be an important protease in the terminal differentiation of keratinocytes.
Epilysin (MMP-28) is a recently identified member of the matrix metalloproteinase (MMP) family. To explore the expression of epilysin in vivo and to gain insight into its biological functions, we ...have cloned the mouse epilysin cDNA and determined its expression. The amino acid sequence of the mouse protein is 85% identical with the human sequence and contains conserved features such as an RKKR furin-activation sequence following the prodomain. Unexpectedly, we found two alternatively spliced forms of the epilysin mRNA lacking 30 and 72 nt at the beginning of the seventh exon coding for part of the haemopexin domain. Expression of recombinant epilysin in HT-1080 fibrosarcoma cells indicated that epilysin was secreted as a major 48 kDa form and a minor 58 kDa form. Expression of the 58 kDa form was increased by a synthetic furin inhibitor at the expense of the 48 kDa form, suggesting that furin cleaves and activates epilysin. Epilysin mRNA was detected in a number of mouse tissues, with the highest expression in the lung, placenta, heart and uterus, and lower levels in the testis and gastrointestinal tract. The wide expression of epilysin in intact, healthy tissues suggests that this MMP functions in physiological tissue homoeostasis and turnover.
We have characterized a novel human matrix metalloproteinase (MMP-21) from human placenta DNA complementary to RNA (cDNA). The 569 amino acid translation of the cDNA includes all the typical features ...of an MMP family member, namely a signal sequence, a prodomain with a PRCGVPD motif, a zinc-binding catalytic domain with an HEIGHVLGL sequence, and a hemopexin-like domain flanked by two cysteine residues. Furthermore, MMP-21 has a furin activation sequence, but no transmembrane sequence nor a cytoplasmic domain. As in Xenopus laevis and Cynops pyrrhogaster there is an additional insertion of approximately 30 amino acids between the prodomain and the catalytic domain, which is poorly conserved between the species and is in human MMP-21 especially proline rich. The MMP-21 gene has seven exons and is located in chromosome 10. This new MMP is the human orthologue for XMMP and CyMMP expressed during gastrulation of X. laevis and C. pyrrhogaster, respectively. A 2.5 kb messenger RNA was observed in fetal liver by Northern analysis. By reverse transcription-polymerase chain reaction, MMP-21 is expressed in various human fetal and adult tissues as well as in cancer cell lines. MMP-21 protein can also be detected in malignancies such as ovarian and colon carcinomas by immunohistochemical staining. Our findings suggest that MMP-21 functions in embryogenesis and tumor progression.
Metastatic renal cell carcinoma (RCC) resulting from the hereditary loss of the von Hippel-Lindau (VHL) tumor suppressor gene is the leading cause of death in VHL patients due to the deleterious ...effects of the metastatic tumor(s). VHL functions in the destruction of the alpha subunits of the heterodimeric transcription factor, hypoxia-inducible factor (HIF-1 alpha and HIF-2 alpha), in normoxic conditions. When VHL function is lost, HIF-alpha protein is stabilized, and target hypoxia-inducible genes are transcribed. The process of tumor invasion and metastasis involves the destruction of the extracellular matrix, which is accomplished primarily by the matrix metalloproteinase (MMP) family of enzymes. Here, we describe a connection between the loss of VHL tumor suppressor function and the upregulation of membrane type-1 MMP (MT1-MMP) gene expression and protein. Specifically, MT1-MMP is upregulated in VHL-/- RCC cells through an increase in gene transcription, which is mediated by the cooperative effects of the transcription factors, HIF-2 and Sp1. Further, we identify a functional HIF-binding site in the proximal promoter of MT1-MMP. To our knowledge, this is the first report to show direct regulation of MT1-MMP by HIF-2 and to provide a direct link between the loss of VHL tumor suppressor function and an increase in MMP gene and protein expression.
Human matrix metalloproteinase-21 (MMP-21), the newest member of the MMP gene family, has been suggested to play an important role in embryogenesis and tumor progression and to be a target of the ...Wnt, Pax, and Notch signaling pathways. Here we report detection of MMP-21 by RT-PCR in mouse embryos aged 10.5, 12.5, 13.5, and 16.5 days, as well as in various adult murine organs. In both humans and mice, MMP-21 protein was detected in the epithelial cells of developing kidney, intestine, neuroectoderm, and skin but not in normal adult skin using immunohistochemistry with two unrelated antibodies. However, it was present in invasive cancer cells of aggressive subtypes of basal and squamous cell carcinomas, although it was not expressed in skin disorders characterized by mere keratinocyte hyperproliferation. Of several cytokines tested, transforming growth factor-β1 induced MMP-21 in vitro in HaCaTs and keratinocytes as judged by real-time quantitative TaqMan PCR. Although suprabasal differentiating keratinocytes expressed MMP-21 in developing skin in vivo, MMP-21–positive keratinocytes were detected by immunohistochemistry in both low and high calcium cultures. MMP-21 expression was not up-regulated by ras transformation in HaCaT cell lines (HaCaT, A5, II-4, and RT3); in skin and colon cancers, its expression did not associate with apoptosis, β-catenin transactivation, or epithelial MMPs-9 and -10. However, MMP-21 protein was found in the same regions as MMP-7 but not in the same cells. Our results suggest that during development, MMP-21 expression is temporally and spatially tightly controlled. Unlike many classical MMPs, it is present in various normal adult tissues. Among epithelial MMPs, MMP-21 has a unique expression pattern in cancer.
Migrating cells degrade pericellular matrices and basement membranes. For these purposes cells produce a number of proteolytic enzymes. Mast cells produce two major proteinases, chymase and tryptase, ...whose physiological functions are poorly known. In the present study we have analyzed the ability of purified human mast cell tryptase to digest pericellular matrices of human fibroblasts. Isolated matrices of human fibroblasts and fibroblast conditioned medium were treated with tryptase, and alterations in the radiolabeled polypeptides were observed in autoradiograms of sodium dodecyl sulphate polyacrylamide gels. It was found that an M(r) 72,000 protein was digested to an M(r) 62,000 form by human mast cell tryptase while the plasminogen activator inhibitor, PAI-1, was not affected. Cleavage of the M(r) 72,000 protein could be partially inhibited by known inhibitors of tryptase but not by aprotinin, soybean trypsin inhibitor, or EDTA. Fibroblastic cells secreted the M(r) 72,000 protein into their medium and it bound to gelatin as shown by analysis of the medium by affinity chromatography over gelatin-Sepharose. The soluble form of the M(r) 72,000 protein was also susceptible to cleavage by tryptase. Analysis using gelatin containing polyacrylamide gels showed that both the intact M(r) 72,000 and the M(r) 62,000 degraded form of the protein possess gelatinolytic activity after activation by sodium dodecyl sulphate. Immunoblotting analysis of the matrices revealed the cleavage of an immunoreactive protein of M(r) 72,000 indicating that the protein is related to type IV collagenase. Further analysis of the pericellular matrices indicated that the protease sensitive extracellular matrix protein fibronectin was removed from the matrix by tryptase in a dose-dependent manner. Fibronectin was also susceptible to proteolytic degradation by tryptase. The data suggest a role for mast cell tryptase in the degradation of pericellular matrices.
The complete structure of the human gene for 92-kDa type IV collagenase was determined. Two overlapping genomic clones spanning
26 kilobases (kb) of genomic DNA were shown to contain the entire ...7.7-kb structural gene together with 15 and 3.5 kb of 5'-end
and 3'-end flanking regions, respectively. The 92-kDa type IV collagenase gene contains 13 exons as does the 72-kDa type IV
collagenase gene. All intron locations of the 92-kDa enzyme gene coincided with intron locations in the 72-kDa enzyme gene.
Exons 5, 6, and 7 which were 174, 174, and 177 base pairs long, respectively, each encoded one complete internal repeat which
resembles the collagen-binding domains of fibronectin. The sequence coding for a unique 48-residue segment in the 92-kDa type
IV collagenase that has no counterpart in other metalloproteinases was not present in a separate exon, but was contained in
exon 9 which also codes for sequences with homology to the other metalloproteinases. The initiation site for transcription
was determined by primer extension analysis. Sequencing analysis of 599 base pairs of the 5'-end flanking region showed that
the promoter does not have a TATA motif, but a TTAAA sequence at position -29 to -25. A CAAT motif was not observed but there
was one GC box. Two putative 12-O-tetradecanoyl-phorbol-13-acetate (TPA) response elements, that might serve as binding sites
for the transcription factor AP-1 and a consensus sequence of a transforming growth factor beta 1 (TGF-beta 1) inhibitory
element were found in the promoter region. Gelatinase assay of enzyme secreted by cultured human fibrosarcoma cells (HT-1080)
revealed only low levels of 92-kDa type IV collagenase activity, whereas considerable activity of the 72-kDa enzyme was present.
Northern hybridization analysis confirmed these findings. Treatment of the HT-1080 cells with TPA resulted in induction of
the secretion of 92-kDa type IV collagenase activity. This induction could not be significantly inhibited by concomitant incubation
with TGF-beta 1. TPA and TGF-beta 1 did not markedly affect the activities of the 72-kDa enzyme. The activities of the secreted
92- and 72-kDa enzymes by HT-1080 cells correlated with the amounts of mRNA as estimated by Northern analyses.
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.
PDF
