Expression of matrix metalloproteinase-26 and tissue inhibitor of matrix metalloproteinase-3 and -4 in endometrium throughout the normal menstrual cycle and alteration in users of levonorgestrel implants who experience irregular uterine bleeding

OBJECTIVE

To determine the expression of matrix metalloproteinase (MMP-26) and tissue inhibitor of MMP (TIMP) in the endometrium of women with normal menstrual cycles compared with users of levonorgestrel implants.

DESIGN

Prospective observational study.

SETTING

Academic research center.

PATIENT(S)

Fifty patients with normal menstrual cycles who requested permanent surgical sterilization (tubal ligation) and 35 users of levonorgestrel implants.

INTERVENTION(S)

Endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Expression of MMP-26, TIMP-3, and TIMP-4 by immunohistochemistry and semiquantitative analysis of staining intensity by using the H score.

RESULT(S)

Endometrium from women with a normal menstrual cycle and users of levonorgestrel implants expresses MMP-26, TIMP-3, and TIMP-4. These substances are present in various types of endometrial cells; expression is strongest in surface and glandular epithelial cells, followed by vascular endothelial and endometrial stromal cells. Inflammatory and immune-related cells also stained strongly for MMP-26 and TIMPs. Semiquantitative analysis of the staining intensity of endometrial epithelial and stromal cells indicated that expression of MMP-26, TIMP-3, and TIMP-4 peaks during the early to mid-luteal phase. Expression of MMP-26 is elevated in users of levonorgestrel implants who experienced irregular uterine bleeding.

CONCLUSION(S)

Endometrial expression of MMP-26 and TIMP-4 is present throughout the menstrual cycle and is elevated during the early to mid-luteal phase in normally cycling women. Further elevations in MMP-26 are seen in users of levonorgestrel implants who experience irregular uterine bleeding. These substances thus seem to play a role in hormonal regulation and endometrial tissue remodeling.

The structure and regulation of the human and mouse matrix metalloproteinase-21 gene and protein

Matrix metalloproteinases (MMPs) play key roles in tissue remodelling under normal development and, especially, in diseases ranging from malignancies to stroke. We cloned and thoroughly characterized the novel human and mouse MMP gene encoding MMP-21. MMP-21 is the last uncharacterized MMP coded by the human genome. Human and mouse MMP-21 is the orthologue of Xenopus laevis X-MMP. The latent proenzyme of MMP-21 (569 amino acid residues) consists of the prodomain, the catalytic domain and the haemopexin-like domain, and is potentially capable of being activated in its secretory pathway to the extracellular milieu by furin-like proprotein convertases. Human MMP-21 is the probable target gene of the Wnt pathway. In addition, the expression of MMP-21 is controlled uniquely by Pax and Notch transcription factors known to be critical for organogenesis. MMP-21 is expressed transiently in mouse embryogenesis and increased in embryonic neuronal tissues. Our observations clearly indicate that there is an important specific function for MMP-21 in embryogenesis, especially in neuronal cells.

Expression of matrix metalloproteinase-26 and tissue inhibitors of metalloproteinases TIMP-3 and -4 in benign endometrium and endometrial cancer

OBJECTIVE

Matrix metalloproteinases (MMPs) and their physiological inhibitors, the tissue inhibitors of MMPs (TIMPs), play a key role in tumor cell invasion, angiogenesis, and growth. The aim of this study was to determine the expression and cellular distribution of MMP-26, TIMP-3, and TIMP-4 in endometrial cancers and benign endometrium throughout the menstrual cycle and the correlation with tumor histological subtype, stage, and grade.

METHODS

Immunohistochemical analysis using polyclonal antibodies generated against pro- and active MMP-26, and mono- and polyclonal antibodies specific to TIMP-3 and TIMP-4, respectively, was performed.

RESULTS

MMP-26, TIMP-3, and TIMP-4 are expressed in endometrial carcinomas (N = 86) and benign endometrium (N = 50) from various stages of the menstrual cycle. Semi-quantitative analysis of staining intensity indicated that endometrial carcinomas expressed more MMP-26, TIMP-3, and TIMP-4 compared to benign endometrium from the postmenopausal period, but not from the secretory phase of the menstrual cycle. The highest staining intensity was associated with endometrial epithelial cells, followed by vascular endothelial cells, myometrial smooth muscle cells, and endometrial stromal cells. Increased staining intensity of MMP-26 and TIMP-3 correlated with grade III tumors and MMP-26 and TIMP-4 with the depth of myometrial invasion in tumors histologically characterized as endometrioid adenocarcinoma, clear-cell, and papillary serous carcinoma staged/graded based on FIGO criteria.

CONCLUSION

MMP-26 and TIMP-4 are expressed in endometrium and endometrial carcinoma and their elevated expression and correlation with myometrial invasion suggests that MMP-26 and TIMP-4 may play a key role in endometrial tumor progression.

Epithelial expression of matrix metalloproteinase-26 is elevated at mid-cycle in the human endometrium

The human endometrium is a dynamic tissue, which undergoes extensive tissue remodelling during the menstrual cycle. Due to their involvement in such processes, several well-characterized matrix metalloproteinases (MMP) have previously been studied in the endometrium. MMP-26 is a newly described matrilysin. We studied MMP-26 mRNA in 39 normal endometrial samples obtained across the menstrual cycle. Tissue distribution and cycle variation was examined using in-situ hybridization, Northern blot analyis and real time PCR. The probes for Northern blot analysis and real time PCR recognized non-overlapping sequences. MMP-26 was localized exclusively in epithelial cells of both glands and the luminal surface. Expression increased during the proliferative phase to a maximum at mid-cycle, then decreased to non-detectable levels in the late secretory and menstrual phases. Expression of MMP-26 mRNA in endometrial tissue explants in vitro required stimulation with both estradiol and progesterone. The tissue content of c-jun mRNA was assayed, since c-jun, as part of the enhancer complex AP-1, may be involved in regulation of MMP-26 gene transcription. The pattern of c-jun expression over the menstrual cycle was similar to that of MMP-26. Epithelial expression in the peri- and post-ovulatory stages of the menstrual cycle suggests the involvement of MMP-26 in reproductive processes.

Activation of pro-gelatinase B by endometase/matrilysin-2 promotes invasion of human prostate cancer cells

This work has explored a putative biochemical mechanism by which endometase/matrilysin-2/matrix metalloproteinase-26 (MMP-26) may promote human prostate cancer cell invasion. Here, we showed that the levels of MMP-26 protein in human prostate carcinomas from multiple patients were significantly higher than those in prostatitis, benign prostate hyperplasia, and normal prostate glandular tissues. The role of MMP-26 in prostate cancer progression is unknown. MMP-26 was capable of activating pro-MMP-9 by cleavage at the Ala(93)-Met(94) site of the prepro-enzyme. This activation proceeded in a time- and dose-dependent manner, facilitating the efficient cleavage of fibronectin by MMP-9. The activated MMP-9 products generated by MMP-26 appeared more stable than those cleaved by MMP-7 under the conditions tested. To investigate the contribution of MMP-26 to cancer cell invasion via the activation of MMP-9, highly invasive and metastatic human prostate carcinoma cells, androgen-repressed prostate cancer (ARCaP) cells were selected as a working model. ARCaP cells express both MMP-26 and MMP-9. Specific anti-MMP-26 and anti-MMP-9 functional blocking antibodies both reduced the invasiveness of ARCaP cells across fibronectin or type IV collagen. Furthermore, the introduction of MMP-26 antisense cDNA into ARCaP cells significantly reduced the MMP-26 protein level in these cells and strongly suppressed the invasiveness of ARCaP cells. Double immunofluorescence staining and confocal laser scanning microscopic images revealed that MMP-26 and MMP-9 were co-localized in parental and MMP-26 sense-transfected ARCaP cells. Moreover, MMP-26 and MMP-9 proteins were both expressed in the same human prostate carcinoma tissue samples examined. These results indicate that MMP-26 may be a physiological and pathological activator of pro-MMP-9.

Matrix metalloproteinases are differentially expressed in adipose tissue during obesity and modulate adipocyte differentiation

Matrix metalloproteinases (MMPs) are essential for proper extracellular matrix remodeling, a process that takes place during obesity-mediated adipose tissue formation. Here, we examine expression profiles and the potential role of MMPs and their tissue inhibitors (TIMPs) in adipose tissue remodeling during obesity. Expression patterns are studied by Northern blot and real-time PCR in two genetic models of obesity (ob/ob and db/db mice) and in a diet-induced model of obesity (AKR mice). Of the MMPs and TIMPs studied, mRNA levels for MMP-2, MMP-3, MMP-12, MMP-14, MMP-19, and TIMP-1 are strongly induced in obese adipose tissues compared with lean tissues. In contrast, MMP-7 and TIMP-3 mRNAs are markedly decreased in obesity. Interestingly, enzymatic activities of MMP-12 and of a new identified adipocyte-derived 30-kDa metalloproteinase are enhanced in obese adipose tissue fractions, demonstrating that MMP/TIMP balance is shifted toward increased matrix degradation in obesity. Finally, we analyze the modulation of MMP-2, MMP-19, and TIMP-1 during 3T3-L1 preadipocyte differentiation, and we explore the effect of inhibition of MMP activity on in vitro adipogenesis. We find that the synthetic MMP inhibitor BB-94 (Batimastat) decreases adipose conversion of 3T3-L1 and primary rat preadipocytes. BB-94 represses differentiation without affecting mitotic clonal expansion but prevents the early expression of CCAAT/enhancer-binding protein beta, a transcription factor that is thought to play a major role in the adipogenic program. Such findings support a role for the MMP/TIMP system in the control of proteolytic events and adipogenesis during obesity-mediated fat mass development.

Matrix metalloproteinase-28 transcript and protein are expressed in rhesus monkey placenta during early pregnancy

The role of matrix metalloproteinases (MMP), especially newly described MMP, in trophoblast invasion during human embryo implantation is poorly understood. In this report, using a model of early pregnancy in the rhesus monkey, we have examined the expression and localization of the most recently identified MMP, MMP-28/epilysin, transcript and protein in macaque uterine samples on days 12, 18 and 26 of pregnancy. MMP-28 mRNA expression was shown by in-situ hybridization after day 12 of pregnancy, and both the syncytial and the cytotrophoblastic cell layers of placental villi, the cytotrophoblast cells of the trophoblastic column, and the extravillous trophoblast cells of trophoblastic shell were primary producers of MMP-28 transcript. Expression of MMP-28 mRNA was undetectable in the endovascular trophoblast cells, decidual cells, luminal and glandular epithelium, arterioles, and myometrium. RT-PCR analysis amplified a fragment of 258 nucleotides from rhesus monkey uterine samples containing implantation sites on days 18 and 26. The cDNA fragment, following sequencing, was confirmed to be part of the haemopexin-like domain of MMP-28. It has 95% identity with the corresponding region of human MMP-28 gene. Immunohistochemical analysis further demonstrated that the localization of MMP-28 protein was similar to that of its mRNA. The restricted distribution pattern of this novel MMP in the villous and extravillous trophoblasts during rhesus monkey early pregnancy suggests a potential role in trophoblast invasion associated with embryo implantation.

Matrix metalloproteinase-19 is expressed by proliferating epithelium but disappears with neoplastic dedifferentiation

MMP-19 (also designated RASI) is a recently discovered member of a large family of zinc-dependent proteolytic enzymes, most of which have been implicated in cancer growth and metastasis. It differs from the others by its chromosomal location and structure and is expressed by endothelial and vascular smooth muscle cells in vivo. Our aim was to study the putative role of MMP-19 in skin cancer. We also examined its regulation in keratinocyte cultures using quantitative TaqMan RT-PCR. Our results show that MMP-19 can also be detected in stimulated keratinocytes by Northern and Western analyses. In wounds, it was found in keratinocytes outside the migrating area, while in BCC and SCC, it was present in the hyperproliferative (p63-positive), E-cadherin-negative epidermis at the tumor surface but downregulated in invasive cancer islands. Expression was also evident in endothelial cells of neoangiogenic regions and in occasional stromal fibroblasts. Of the 12 tested cytokines/growth factors, only TNF-alpha and PMA were able to stimulate the expression of MMP-19 mRNA in primary keratinocytes. No MMP-19 mRNA was detected by Northern analysis in cultured HaCaT or A5 cells or in an SCC cell line established from head-and-neck cancer. Our data suggest that, unlike most MMPs, MMP-19 expression in the epidermis is downregulated during transformation and histologic dedifferentiation.

Matrix metalloproteinase-26 is expressed in human endometrium but not in endometrial carcinoma

BACKGROUND

The human matrix metalloproteinase (MMP)-26, also called matrilysin-2 or endometase, has been isolated as a matrilysin (MMP-7) homolog. Matrix metalloproteinase-26 was expressed in tissue samples from the placenta and endometrial tumors and its expression may be related to the development of endometrial carcinomas.

METHODS

Total RNAs were isolated from 5 endometrial carcinoma cell lines, 36 normal endometrial tissue samples, 4 hyperplasia tissue samples, and from 24 endometrial carcinoma tissue samples. Reverse transcription-polymerase chain reation (RT-PCR) was performed to detect MMP-26 mRNA expression. To identify MMP-26 mRNA localization and protein expression, we performed in situ RT-PCR and immunohistochemistry, respectively.

RESULTS

Reverse transcription-polymerase chain reaction analysis revealed that MMP-26 mRNA was expressed in 24 of 36 normal human endometrial tissue samples. However, MMP-26 mRNA expression was not detected in endometrial carcinoma cell lines nor in endometrial carcinoma tissue samples except for one case. Western blot analysis showed similar results. In situ RT-PCR analysis revealed that MMP-26 expression was localized in the epithelial glandular cells but faint expression was observed in the stromal cells. Subsequently, we separated endometrial tissues into epithelial glandular and stromal cells. Using RT-PCR, the purified epithelial glandular cells exhibited MMP-26 mRNA expression but the purified stromal cells did not. Immunohistochemical analyses revealed that MMP-26 protein expression is also limited to endometrial epithelial glandular cells but not to cancer cells. Therefore, MMP-26 expression is limited to normal epithelial glandular cells.

CONCLUSIONS

We found a significant difference in MMP-26 expression in normal and malignant endometrial tissue samples, although its function is still unknown. These data suggest that MMP-26 may be a candidate for a new tumor marker for endometrial carcinomas.

Matrix metalloproteinase-21, the human orthologue for XMMP, is expressed during fetal development and in cancer

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.

Identification and specific expression of matrix metalloproteinase-26 in rhesus monkey endometrium during early pregnancy

Matrix metalloproteinases (MMPs) and their tissue inhibitors may play important roles in tissue remodelling processes of the uterus. This study identified MMP-26 (endometase/matrilysin-2) in the endometrium of pregnant rhesus monkeys (Macaca mulatta) and monitored the spatial and temporal expression of the transcript and protein in the uteri on days 12, 18 and 26 of pregnancy. The partial monkey MMP-26 gene sequence of 289 nucleotides was 98% identical to that of its human homologue and its protein fragment contained a PHCGVPDGSD sequence in the prodomain identical to that in human MMP-26. RT-PCR analysis demonstrated that the average level of MMP-26 mRNA in the endometrium was high on day 12 of pregnancy, but significantly decreased on days 18 and 26 (P < 0.05). In-situ hybridization confirmed that MMP-26 mRNA is specifically localized in the endometrial compartments, with intense signals in the glandular epithelium on day 12 and in the walls of spiral arterioles adjacent to the implantation site on day 26. The hybridization signal for MMP-26 mRNA in the glandular epithelium decreased dramatically on day 18 and was undetectable on day 26. No MMP-26 mRNA transcripts were detected in the placental villi on days 18 and 26. Immunohistochemistry showed that the expression pattern of MMP-26 protein was similar to that of its mRNA. The restricted expression pattern of MMP-26 in the monkey uterus implies that this new MMP is involved in the highly regulated tissue remodelling processes of the glandular epithelium and spiral arteries during early pregnancy.

Peptide substrate specificities and protein cleavage sites of human endometase/matrilysin-2/matrix metalloproteinase-26

Human endometase/matrilysin-2/matrix metalloproteinase-26 (MMP-26) is a novel epithelial and cancer-specific metalloproteinase. Peptide libraries were used to profile the substrate specificity of MMP-26 from the P4-P4' sites. The optimal cleavage motifs for MMP-26 were Lys-Pro-Ile/Leu-Ser(P1)-Leu/Met(P1')-Ile/Thr-Ser/Ala-Ser. The strongest preference was observed at the P1' and P2 sites where hydrophobic residues were favored. Proline was preferred at P3, and Serine was preferred at P1. The overall specificity was similar to that of other MMPs with the exception that more flexibility was observed at P1, P2', and P3'. Accordingly, synthetic inhibitors of gelatinases and collagenases inhibited MMP-26 with similar efficacy. A pair of stereoisomers had only a 40-fold difference in K(i)(app) values against MMP-26 compared with a 250-fold difference against neutrophil collagenase, indicating that MMP-26 is less stereoselective for its inhibitors. MMP-26 autodigested itself during the folding process. Two of the major autolytic sites were Leu(49)-Thr(50) and Ala(75)-Leu(76), which still left the cysteine switch sequence (PHC(82)GVPD) intact. This suggests that Cys(82) may not play a role in the latency of the zymogen. Interestingly, inhibitor titration studies revealed that only approximately 5% of the total MMP-26 molecules was catalytically active, indicating that the thiol groups of Cys(82) in the active molecules may be dissociated or removed from the active site zinc ions. MMP-26 cleaved Phe(352)-Leu(353) and Pro(357)-Met(358) in the reactive loop of alpha(1)-proteinase inhibitor and His(140)-Val(141) in insulin-like growth factor-binding protein-1, probably rendering these substrates inactive. Among the fluorescent peptide substrates analyzed, Mca-Pro-Leu-Ala-Nva-Dpa-Ala-Arg-NH(2) displayed the highest specificity constant (30,000/molar second) with MMP-26. This report proposes a working model for the future studies of pro-MMP-26 activation, the design of inhibitors, and the identification of optimal physiological and pathological substrates of MMP-26 in vivo.

Epilysin (MMP-28) expression is associated with cell proliferation during epithelial repair

Epilysin (MMP-28) is the newest member of the matrix metalloproteinase enzyme family. Several members of this enzyme family have been associated with various aspects of wound repair and cancer invasion. The aim of this study was to characterize in different types of wounds, skin cancers, and keratinocyte cultures factors that contribute to epilysin expression in vivo, as well as how and where it is induced in relation to other matrix metalloproteinases. Our results indicate that epilysin is produced by the mitotic Ki-67-positive keratinocytes distal from the wound edge in both acute and chronic wounds and that it does not generally colocalize with collagenase-1, stromelysin-2, or 92 kDa gelatinase in migrating keratinocytes. An injury of epidermis was needed for epilysin induction as it was upregulated in ulcerated pyogenic granulomas and in suction blisters but was not detected in intact acanthotic or normal skin. Unlike many other matrix metalloproteinases, epilysin was not detected in the invading cancer cell nests of sclerosing basal or squamous cell cancers of various grades. When primary keratinocytes were stimulated with tumor necrosis factor alpha, upregulation of epilysin mRNA was evident within 24-48 h as measured by quantitative reverse transcription polymerase chain reaction. In primary keratinocyte, HaCaT, and A431 carcinoma cell cultures none of the 10 other growth factors or extracellular matrices studied were able to upregulate epilysin expression. Our results suggest that epilysin expression is tightly spatially and temporally regulated during wound repair. Although the in vivo substrates of epilysin are not known at present, its expression pattern suggests that it may be needed to restructure the basement membrane or to degrade adhesive proteins between keratinocytes to supply new cells for the migrating front.

Expression of matrix metalloproteinase-26 and tissue inhibitor of metalloproteinase-4 in human normal cytotrophoblast cells and a choriocarcinoma cell line, JEG-3

The balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) is critical for embryo implantation. Disturbance of this balance may lead to tumour metastasis. To understand the roles of MMP-26 and TIMP-4 in physiological and pathological invasion, the expression of these proteins in normal human cytotrophoblast cells and in a malignant choriocarcinoma cell line, JEG-3, was investigated. MMP-26 and TIMP-4 proteins were detected in the cytoplasm of these cells. The expression levels of MMP-26 mRNA and protein in JEG-3 cells were significantly higher than those in the cytotrophoblasts; conversely, the expression levels of TIMP-4 mRNA and protein were much lower in JEG-3 cells than those in cytotrophoblasts (P < 0.01). Enzyme inhibition studies demonstrated that TIMP-4 was a potent inhibitor of MMP-26 with an IC50 value of 0.4 nmol/l. This study confirms that MMP-26 is an epithelial enzyme and suggests that MMP-26 and TIMP-4 may play a role in tissue-remodelling processes associated with placentation and tumour progression, and that a higher MMP-26 to TIMP-4 ratio may promote cancer invasion.

Unconventional activation mechanisms of MMP-26, a human matrix metalloproteinase with a unique PHCGXXD cysteine-switch motif

ProMMP-26 has the unique Pro-His(81)-Cys-Gly-Xaa-Xaa-Asp cysteine-switch motif that discriminates this protease from all other matrix metalloproteinases (MMPs) known so far. The conserved, free cysteine residue of the conventional PRCXXPD sequence interacts with the zinc ion of the catalytic domain and provides the fourth coordination site for the catalytic zinc, thereby preventing latent proMMPs from becoming active. MMPs become functionally active when proteolytic cleavage releases the prodomain and the PRCXXPD sequence and exposes the zinc atom. Here, we report that the Pro-His(81)-Cys-Gly-Xaa-Xaa-Asp motif is not functional in proMMP-26 and consequently is not involved in the activation mechanisms. Organomercurial treatment failed to activate proMMP-26. The autolytic Lys-Lys-Gln(59) downward arrow Gln(60)-Phe-His cleavage upstream of the Pro-His(81)-Cys-Gly-Xaa-Xaa-Asp motif induced the proteolytic activity of recombinant proMMP-26 whereas any further cleavage inactivated the enzyme. The His(81) --> Arg(81) mutation restored the conventional cysteine-switch sequence in the prodomain but failed to induce the cysteine-switch activation mechanism. These data and computer modeling studies allowed us to hypothesize that the presence of His(81) significantly modified the fold of proMMP-26, abolished the functionality of the cysteine-switch motif, and stimulated an alternative intramolecular activation pathway of the proenzyme.

Promoter characterization of the novel human matrix metalloproteinase-26 gene: regulation by the T-cell factor-4 implies specific expression of the gene in cancer cells of epithelial origin

A novel matrix metalloproteinase-26 (MMP-26) is known to be specifically expressed in epithelial carcinomas. To facilitate studies of MMP-26 transcriptional regulation, we have cloned and characterized a 1 kb 5'-flanking region of the human MMP-26 gene. Altogether, our findings indicate that the MMP-26 promoter has distinctive structural and functional features among MMP genes. An unusual polyadenylation site proximal to the transcription-factor-binding sites protects transcription of the MMP-26 gene from the upstream promoters and represents a part of the stringent transcriptional regulation of the gene. The MMP-26 gene has a consensus TATA-box and one transcriptional start site located 60 and 35 nucleotides upstream of the translational start site, respectively. The MMP-26 promoter was able to drive luciferase expression in human A549 lung carcinoma, HT1080 fibrosarcoma and HEK293 embryonic kidney cells. The basal transcription efficiency of the MMP-26 promoter is relatively low, thereby explaining the minute expression of the gene in most cells and tissues. When compared with other MMP genes, the MMP-26 promoter contains binding sites for a few transcription factors. Sequential deletion and mutation analysis, and electrophoretic mobility-shift assay have identified the T-cell factor-4 (Tcf-4) motif and the activator protein-1 site as the major regulatory elements of the MMP-26 promoter. Since previous studies have established that the Tcf-4 transcription factor is subjected exclusively to regulation through the beta-catenin/E(epithelial)-cadherin pathway, this implies the specific expression of MMP-26 in cancer cells of epithelial origin.

Matrix metalloproteinase-19 is expressed in myeloid cells in an adhesion-dependent manner and associates with the cell surface

We have previously reported the isolation of the human matrix metalloproteinase (MMP)-19 (also referred to as RASI) from a synovium of a patient suffering from rheumatoid arthritis and its expression at the cell surface of activated PBMC. In this study, we have analyzed the regulation and cell surface expression of human MMP-19 in several human cell lines and blood-derived cells. Among the cell lines analyzed, MMP-19 is largely expressed by lung fibroblasts as well as by myeloid cell lines THP-1 and HL-60. After fractionating PBMC into CD14- and CD14+ populations we found that only the latter one expresses MMP-19. Although the myeloid cell lines as well as CD14+ cells express MMP-19 without stimulation, its production can be up-regulated by phorbol esters (PMA) or by adhesion. The adhesion-dependent expression was down-regulated or even abrogated by blockade of adhesion or interfering with adhesion-controlling signaling using alpha-tocopherol. We have shown that MMP-19 associates with the cell surface of myeloid cells. This cell surface association was not affected by phospholipase C. However, acidic treatment of the THP-1-derived cell membranes abolished the immunoprecipitation of MMP-19 thereof. Moreover, a high salt treatment of THP-1 cells diminished the MMP-19 detection on the cell surface. This implicates a noncovalent attachment of MMP-19 to the cell surface. Because a truncated form of the MMP-19, in which the hemopexin-like domain was deleted (Delta(hp)MMP-19), does not associate with the surface, the hemopexin-like domain appears to be critical for the cell surface attachment of human MMP-19.

Matrix metalloproteinases: a multifunctional group of molecules

The matrix metalloproteinases are a large group of zinc-containing proteases with a central role in the degradation of all types of extracellular matrix. Increased matrix degradation is a characteristic feature of several disease processes, most notably tumour invasion; it is now widely recognized that this group of proteases has a key role in facilitating invasion and metastasis. However, it is also becoming increasingly recognized that the matrix metalloproteinases are a multifunctional group of biologically important molecules with diverse roles in normal cell growth, differentiation, and cell regulation, and with involvement in the early stages of tumourigenesis. Some of these regulatory functions may be distinct from the matrix-degrading capabilities of this group of enzymes.

Promoter characterization of the human and mouse epilysin (MMP-28) genes

Epilysin (MMP-28) is a recently cloned member of the matrix metalloproteinase family (Lohi et al., J. Biol. Chem. 276 (2001) 10134). It is expressed at highest levels in the skin by basal and suprabasal keratinocytes, and in testis by developing germ cells. To characterize the epilysin promoter, we isolated a 3.0 kb fragment of human genomic DNA containing 5'-flanking sequence of the epilysin gene, and a corresponding 660 bp fragment from the mouse. The 5'-flanking sequences contain no typical TATA-boxes or CCAAT sequences close to the translation initiation sites. RNase protection assay revealed that two transcription start sites are utilized in the human epilysin gene, situated 210 and 230 bp upstream from the translation start site. The promoter contains a GT-box, situated 300 bp upstream from the translation start site, with homology to the consensus binding site for transcription factors of the Sp family. This site is perfectly conserved between the human and mouse promoters. For reporter gene assays a series of constructs with fragments of increasing length of the epilysin promoter were coupled to the firefly luciferase gene. Reporter gene assays indicated that deletion or mutation of the GT-box dramatically reduces the transcriptional activity both in keratinocytes and in spermatogonia. Gel mobility shift assays showed that several nuclear proteins bind specifically to this sequence. Supershift assays with antibodies specific for members of the Sp family identified Sp1 and Sp3 as components of these protein/DNA complexes and hence as possible regulators of the epilysin gene. Our results indicate that the epilysin promoter has distinctive structural and functional features, which may control the unique expression and regulation patterns of the epilysin gene.

MMP-19: cellular localization of a novel metalloproteinase within normal breast tissue and mammary gland tumours

Matrix metalloproteinases (MMPs) are instrumental in promoting and facilitating the spread of malignant diseases and in the de novo formation of blood vessels. This study has mapped the immunoreactivity of a novel, angiogenesis-related metalloproteinase--MMP-19--in normal breast tissue and in benign and malignant breast lesions and compared this pattern of expression with that of MMP-2. In the normal resting mammary gland, MMP-19 was strongly expressed in the myoepithelial layer of the ductal system; the alveolar and ductal epithelia displayed considerable, but lobule-specific, variations in labelling intensity. MMP-19 was also present within the smooth muscle and endothelial layers of large and medium-sized blood vessels, as well as within capillary walls. In benign lesions, all tumour cells and their surrounding vasculature were uniformly and strongly immunoreactive for MMP-19. Progression towards an invasive phenotype and neoplastic dedifferentiation led to the disappearance of MMP-19 from tumour cells and blood vessels and a concomitant rise in the levels of MMP-2. In vitro experiments conducted with isolated smooth muscle cells cultivated on a solid substratum, or within the interstices of a collagen matrix, indicated that the expression of MMP-19 is influenced by the architecture of the surrounding extracellular matrix.

Matrix metalloproteinases: a multifunctional group of molecules

The matrix metalloproteinases are a large group of zinc-containing proteases with a central role in the degradation of all types of extracellular matrix. Increased matrix degradation is a characteristic feature of several disease processes, most notably tumour invasion; it is now widely recognized that this group of proteases has a key role in facilitating invasion and metastasis. However, it is also becoming increasingly recognized that the matrix metalloproteinases are a multifunctional group of biologically important molecules with diverse roles in normal cell growth, differentiation, and cell regulation, and with involvement in the early stages of tumourigenesis. Some of these regulatory functions may be distinct from the matrix-degrading capabilities of this group of enzymes.

Characterization of matrix metalloproteinase-26, a novel metalloproteinase widely expressed in cancer cells of epithelial origin

Identification of expanding roles for matrix metalloproteinases (MMPs) in complex regulatory processes of tissue remodelling has stimulated the search for genes encoding proteinases with unique functions, regulation and expression patterns. By using a novel cloning strategy, we identified three previously unknown human MMPs, i.e. MMP-21, MMP-26 and MMP-28, in comprehensive gene libraries. The present study is focused on the gene and the protein of a novel MMP, MMP-26. Our findings show that MMP-26 is specifically expressed in cancer cells of epithelial origin, including carcinomas of lung, prostate and breast. Several unique structural and regulatory features, including an unusual 'cysteine-switch' motif, discriminate broad-spectrum MMP-26 from most other MMPs. MMP-26 efficiently cleaves fibrinogen and extracellular matrix proteins, including fibronectin, vitronectin and denatured collagen. Protein sequence, minimal modular domain structure, exon-intron mapping and computer modelling demonstrate similarity between MMP-26 and MMP-7 (matrilysin). However, substrate specificity and transcriptional regulation, as well as the functional role of MMP-26 and MMP-7 in cancer, are likely to be distinct. Despite these differences, matrilysin-2 may be a suitable trivial name for MMP-26. Our observations suggest an important specific function for MMP-26 in tumour progression and angiogenesis, and confirm and extend the recent findings of other authors [Park, Ni, Gerkema, Liu, Belozerov and Sang (2000) J. Biol. Chem. 275, 20540--20544; Uría and López-Otín (2000) Cancer Res. 60, 4745--4751; de Coignac, Elson, Delneste, Magistrelli, Jeannin, Aubry, Berthier, Schmitt, Bonnefoy and Gauchat (2000) Eur. J. Biochem. 267, 3323--3329].

In vivo gene expression revealed by cDNA arrays: the pattern in relapsing-remitting multiple sclerosis patients compared with normal subjects

OBJECTIVES

To use DNA arrays to identify differences in gene expression associated with relapsing-remitting (RR) MS.

METHODS

Total RNA was isolated from monocyte depleted peripheral blood mononuclear cells of 15 RR MS patients and 15 age- and sex-matched controls. The RNA was reverse transcribed to radiolabeled cDNA and the resultant cDNA was used to probe a DNA array containing over 4000 named human genes. The binding of radiolabeled cDNA to the probes on the array was measured by phosphorimager.

RESULTS

Of more than 4000 genes tested, only 34 were significantly different in RR-MS patients from controls. Of these, 25 were significantly increased and 9 significantly decreased in the RR MS patients. Twelve of these genes have inflammatory and/or immunological functions that could be relevant to the MS disease process. The potentially relevant genes that were elevated (15% to 28%) were P protein, LCK, cAMP responsive element modulator, IL-7 receptor, matrix metalloproteinase-19, M130 antigen, and peptidyl-prolyl isomerase. Those that were significantly decreased (15% to 35%) were SAS transmembrane 4 superfamily protein, STRL22 (C-C chemokine receptor 6), AFX protein, DNA fragmentation factor-45 and immunoglobulin gamma 3 (Gm marker).

CONCLUSIONS

The RR-MS disease effect was relatively restricted and most of the mRNAs tested were not different from the normal controls. However, there were significant differences identified in the expression of a subset of mRNAs, including 13 with inflammatory/immune functions that could be relevant to MS. The systematic use of DNA arrays can provide insight into the dynamic cellular pathways involved in MS pathogenesis and its phenotypic heterogeneity.

Epilysin, a novel human matrix metalloproteinase (MMP-28) expressed in testis and keratinocytes and in response to injury

We have cloned a new human matrix metalloproteinase (MMP-28, epilysin) from human keratinocyte and testis cDNA libraries. Like most MMPs, epilysin contains a signal sequence, a prodomain with a PRCGVTD sequence, a zinc-binding catalytic domain with an HEIGHTLGLTH sequence, and a hemopexin-like domain. In addition, epilysin has a furin activation sequence (RRKKR) but has no transmembrane sequence. The exon-intron organization and splicing pattern of epilysin differ from that of other MMP genes. It has only 8 exons, and 5 exons are spliced at sites not used by other MMPs. Another novel feature of epilysin is that exon 4 is alternatively spliced to a transcript that does not encode the N-terminal half of the catalytic domain. Northern hybridization of tissue RNA indicated that epilysin is expressed at high levels in testis and at lower levels in lungs, heart, colon, intestine, and brain. RNase protection assay with various cell lines indicated that epilysin was selectively expressed in keratinocytes. Recombinant epilysin degraded casein in a zymography assay, and its proteolytic activity was inhibited by EDTA and by batimastat, a selective MMP inhibitor. Immunohistochemical staining showed expression of epilysin protein in the basal and suprabasal epidermis of intact skin. In injured skin, prominent staining for epilysin was seen in basal keratinocytes both at and some distance from the wound edge, a pattern that is quite distinct from that of other MMPs expressed during tissue repair. These findings suggest that this new MMP functions in several tissues both in tissue homeostasis and in repair.

MMP-28, a new human matrix metalloproteinase with an unusual cysteine-switch sequence is widely expressed in tumors

We report the discovery, cloning, and characterization of a novel human matrix metalloproteinase (MMP-28) cDNA gene. The deduced 520-amino-acid sequence of MMP-28 includes a signal peptide, a prodomain with an unusual cysteine-switch PRCGVTD motif followed by the furin cleavage RRKKR site, a catalytic domain, a hinge-region and a hemopexin-like domain. On the basis of their structural characteristics, MMP-28 belongs to the MMP-19 subfamily. The genomic MMP-28 gene uniquely mapped to chromosome 17q11.2 includes eight exons and seven introns. The broad range of expression in carcinomas as well as normal adult and fetal tissues suggests an important functional role for MMP-28.

The murine ortholog of matrix metalloproteinase 19: its cloning, gene organization, and expression

We have isolated a murine cDNA orthologous to the human matrix metalloproteinase 19 (hMMP-19). The murine MMP-19 cDNA was amplified by RT-PCR using specific primers whose DNA sequences were derived from both murine MMP-19 genomic DNA and partial cDNA sequences. The murine MMP-19 (mMMP-19) is 79% identical to the human ortholog and encodes a protein of 527 amino acids with a deduced molecular mass of 59.1kDa. Analyzing the exon/intron junctions we revealed that the murine MMP-19 gene consists of nine exons and eight introns, and thus differs from the gene organization of other matrix metalloproteinases. Furthermore, a 587bp fragment of the mMMP-19 promoter containing a TATA box and an AP-1 binding motif was cloned, and 3.3kb transcripts of the MMP-19 gene were identified in liver, kidney, spleen, and colon. Finally, immunostaining of murine heart cryosections showed that mMMP-19, like its human counterpart, is expressed in the arterial tunica media of large blood vessels. By cloning mMMP-19 and unraveling its genomic structure, we have obtained valuable information for further study of the function of this MMP in vivo.

Matrilysin-2, a new matrix metalloproteinase expressed in human tumors and showing the minimal domain organization required for secretion, latency, and activity

We have identified a human placenta cDNA coding for a new member of the matrix metalloproteinase (MMP) family. The isolated cDNA encodes a polypeptide of 261 amino acids, the smallest MMP identified to date, which contains several structural features of MMPs including the signal sequence, the prodomain involved in enzyme latency, and the catalytic domain with the zinc-binding site. However, it lacks the hinge region and hemopexin-domain present in most MMPs. According to these structural characteristics, the human MMP described herein has been called matrilysin-2 (MMP-26), because it exclusively shares with matrilysin this minimal domain organization required for secretion, latency, and activity. The amino acid sequence of matrilysin-2 also contains a threonine residue adjacent to the Zn-binding site that has been defined as a specific feature of matrilysin. Chromosomal location of the matrilysin-2 gene showed that it maps to the short arm of chromosome 11, a location distinct to that of other MMP genes. Matrilysin-2 was expressed in Escherichia coli, and, after purification and refolding, the recombinant protein was found to degrade synthetic substrates commonly used for assaying MMPs. Furthermore, this protein hydrolyzed type IV collagen, fibronectin, fibrinogen, and gelatin, which indicated that matrilysin-2 is a potent enzyme with a wide substrate specificity. In addition, it was found that matrilysin-2 is able to activate progelatinase B. Proteolytic activity of matrilysin-2 against all of these substrates was abolished by synthetic inhibitors and by tissue inhibitors of metalloproteinases. Expression analysis revealed that matrilysin-2 is detected not only in placenta and uterus but is widely expressed in malignant tumors from different sources as well as in diverse tumor cell lines. These data together with its broad spectrum of proteolytic activity, suggest that matrilysin-2 may play a role in some of the tissue-remodeling events associated with tumor progression.

Matrix metalloproteinases 19 and 20 cleave aggrecan and cartilage oligomeric matrix protein (COMP)

Matrix metalloproteinase (MMP)-19 and MMP-20 (enamelysin) are two recently discovered members of the MMP family. These enzymes are involved in the degradation of the various components of the extracellular matrix (ECM) during development, haemostasis and pathological conditions. Whereas MMP-19 mRNA is found widely expressed in body tissues, including the synovium of normal and rheumatoid arthritic patients, MMP-20 expression is restricted to the enamel organ. In this study we investigated the ability of MMP-19 and MMP-20 to cleave two of the macromolecules characterising the cartilage ECM, namely aggrecan and the cartilage oligomeric matrix protein (COMP). Both MMPs hydrolysed aggrecan efficiently at the well-described MMP cleavage site between residues Asn(341) and Phe(342), as shown by Western blotting using neo-epitope antibodies. Furthermore, the two enzymes cleaved COMP in a distinctive manner, generating a major proteolytic product of 60 kDa. Our results suggest that MMP-19 may participate in the degradation of aggrecan and COMP in arthritic disease, whereas MMP-20, due to its unique expression pattern, may primarily be involved in the turnover of these molecules during tooth development.

Structure of the human MMP-19 gene

The recently identified MMP-19 belongs to the multi-protein family of zinc-binding matrix metalloproteinases (MMP). In order to analyze its genomic organization and to identify transcription factor binding sites that may be involved in the regulation of human MMP-19 expression, the gene coding for MMP-19 has been cloned and sequenced. The MMP-19 gene spans over 7.6kb and is composed of nine exons and eight introns. Furthermore, a 1.9kb fragment of 5'-flanking DNA was isolated and the transcription start point mapped. Nucleotide sequence analysis of its 5'-flanking region revealed several potential transcription factor binding sites typical of MMP promoters. Thus, a TATA-box, a consensus AP-1 binding element, and a putative PEA3 site were identified. The 1.9kb MMP-19 promoter fragment and several deletion constructs thereof were able to drive transcription of the luciferase reporter gene in transiently transfected CHO cells. Finally, it has been shown by an electrophoretic mobility shift assay that the AP-1 consensus sequence is able to bind a HeLa nuclear extract derived AP-1 factor.

Identification and characterization of human endometase (Matrix metalloproteinase-26) from endometrial tumor

We report the discovery, cloning, and characterization of a novel human matrix metalloproteinase 26 (MMP-26) (matrixin) gene, endometase, an endometrial tumor-derived metalloproteinase. Among more than three million expressed sequence tags sequenced, the endometase gene was only obtained from human endometrial tumor cDNA library. Endometase mRNA was expressed specifically in human uterus, not in other tissues/cells tested, e.g. testis, heart, brain, lungs, liver, thymus, and melanoma G361. Endometase protein has a signal peptide, a propeptide domain, and a catalytic domain with a unique "cysteine switch" propeptide sequence, PHCGVPDGSD, and a zinc-binding motif, VATHEIGHSLGLQH. Endometase is 43, 41, 41, and 39% identical to human metalloelastase, stromelysin, collagenase-3, and matrilysin, respectively. The zymogen was expressed and isolated from Escherichia coli as inclusion bodies with a molecular mass of 28 kDa. The identity and homogeneity of the recombinant protein was confirmed by protein N-terminal sequencing, silver stain, and immunoblot analyses. The pro-enzyme was partially activated during the folding process. Endometase selectively cleaved type I gelatin and alpha(1)-proteinase inhibitor; however, it did not digest collagens, laminin, elastin, beta-casein, plasminogen, soybean trypsin inhibitor, or Bowman-Birk inhibitor. It hydrolyzed peptide substrates of matrixins and tumor necrosis factor-alpha converting enzyme. Endometase may selectively cleave extracellular matrix proteins, inactivate serpins, and process cytokines.

Characterization, expression analysis and chromosomal mapping of mouse matrix metalloproteinase-19 (MMP-19)

Using homology-based database screening, we have identified the mouse homologue for the recently described matrix metalloproteinase-19 (MMP-19). Sequencing of mouse MMP-19 resulted in a putative open reading frame (ORF) of 527 amino acids showing 84% identity to the human homologue. In mouse, MMP-19 appears to be most highly expressed in the liver; however, there is a detectable level of expression in all tissues analyzed. The major mouse MMP-19 transcript is almost twice as long as that of human. The COOH-terminal serine and threonine-rich domain is considerably longer in the mouse homologue. The mouse MMP-19 gene maps to very distal end of mouse chromosome 10.

Cloning of MMP-26. A novel matrilysin-like proteinase

A cDNA encoding a novel human matrix metalloproteinase (MMP), named MMP-26, was cloned from fetal cDNA. The deduced 261-amino-acid sequence is homologous to macrophage metalloelastase (51.8% identity). It includes only the minimal characteristic features of the MMP family: a signal peptide, a prodomain and a catalytic domain. As with MMP-7, this new MMP does not comprise the hemopexin domain, which is believed to be involved in substrate recognition. A study of MMP-26 mRNA steady states levels reveals, among the tissue examined, a specific expression in placenta. MMP-26 mRNA could also be detected in several human cell lines such as HEK 293 kidney cells and HFB1 lymphoma cells. Recombinant MMP-26 was produced in mammalian cells and used to demonstrate a proteolytic activity of the enzyme on gelatin and beta-casein.

Biochemical characterization of the catalytic domain of human matrix metalloproteinase 19. Evidence for a role as a potent basement membrane degrading enzyme

We have recently cloned MMP-19, a novel matrix metalloproteinase, which, due to unique structural features, was proposed to represent the first member of a new MMP subfamily (Pendás, A. M., Knäuper, V. , Puente, X. S., Llano, E., Mattei, M. G., Apte, S., Murphy, G., and López-Otin, C. (1997) J. Biol. Chem. 272, 4281-4286). A recombinant COOH-terminal deletion mutant of MMP-19 (proDelta(260-508)MMP-19), comprising the propeptide and the catalytic domain, was expressed in Escherichia coli, refolded, and purified. Interestingly, we found that proDelta(260-508)MMP-19 has the tendency to autoactivate, whereby the Lys(97)-Tyr(98) peptide bond is hydrolyzed, resulting in free catalytic domain. Mutation of two residues (Glu(88) --> Pro and Pro(90) --> Val) within the propeptide latency motif did not prevent autoactivation but the autolysis rate was somewhat reduced. Analysis of the substrate specificity revealed that the catalytic domain of MMP-19 was able to hydrolyze the general MMP substrate Mca-Pro-Leu-Gly-Dpa-Ala-Arg-NH(2) and, with higher efficiency, the stromelysin substrate Mca-Pro-Leu-Ala-Nva-Dpa-Ala-Arg-NH(2). Kinetic analysis of the interactions of the catalytic domain of MMP-19 with the natural MMP inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), showed strong inhibition using TIMP-2, TIMP-3, and TIMP-4, while TIMP-1 was less efficient. We also demonstrated that synthetic hydroxamic acid-based compounds efficiently inhibited the enzyme. The catalytic domain of MMP-19 was able to hydrolyze the basement membrane components type IV collagen, laminin, and nidogen, as well as the large tenascin-C isoform, fibronectin, and type I gelatin in vitro, suggesting that MMP-19 is a potent proteinase capable of hydrolyzing a broad range of extracellular matrix components. Neither the catalytic domain nor the full-length MMP-19 was able to degrade triple-helical collagen. Finally, and in contrast to studies with other MMPs, MMP-19 catalytic domain was not able to activate any of the latent MMPs tested in vitro.

Matrix metalloproteinase-19 in capillary endothelial cells: expression in acutely, but not in chronically, inflamed synovium

Matrix metalloproteinase-19 (MMP-19), originally isolated as an autoantigen from the synovium of a patient suffering from rheumatoid arthritis (RA), is expressed in smooth muscle cells of the tunica media of large blood vessels of an RA patient, but not in the endothelial cell layer. By contrast, in acutely inflamed tissue, synovial capillaries strongly express MMP-19 in the cytoplasm, as shown by immunofluorescence of cryostat sections. In MMP-19-producing capillaries the beta3 integrin chain was found at the endothelial cell surface, as was the vascular endothelial cell growth factor receptor-2 (KDR). The specific tissue inhibitor of metalloproteinases TIMP-1 was absent or faintly stained in MMP-19-expressing capillaries, whereas TIMP-1, but not TIMP-2, was strongly expressed in large vessels and in MMP-19-negative capillaries of RA synovia. In the spontaneously transformed human umbilical vein endothelial cell line ECV304 neither MMP-19 transcripts nor protein could be detected. By contrast, primary cultures of human endothelial cells of either dermal or adipose tissue origin produced MMP-19 mRNA and protein. The results strongly suggest the regulated induction of matrix metalloproteinase-19 in capillary endothelial cells during acute inflammation and hint at a role of MMP-19 in angiogenesis.

Evaluation of some newer matrix metalloproteinases

Recombinant protein expression techniques have been utilized to facilitate the biochemical and cell biological characterization of human matrix metalloproteinases (MMPs). The importance of the membrane type 1 MMP (MMP 14) in the regulation of pericellular proteolysis, either directly or through the activation of MMP-2, MMP-9, and MMP-13 has been identified. Studies on an in vitro chondrocyte-like cell and an in vivo cartilage repair model indicated that such MT1 MMP-regulated activation cascades are physiologically feasible. MMP19 shows a limited sequence identity with other MMPs and may represent a novel subclass. However, analysis of the recombinant protein identified a number of biochemical properties typical of the MMP family.

Overview of expression of matrix metalloproteinases (MMP-17, MMP-18, and MMP-20) in cultured human cells

We recently described the cell type distribution of several matrix metalloproteinases (MMP-1 through MMP-16). In this report we extend this study by analysis of three recently described MMPs. PCR primers for MMP-17, MMP-18, and MMP-20 were optimized for use in RT-PCR. The results demonstrate one or more cell lines or tissue that express mRNA for each of these newly described MMPs.

Structural insight into the binding motifs for the calcium ion and the non-catalytic zinc in matrix metalloproteases

The binding motifs for the structural zinc and calcium ions in matrix metalloproteases (MMPs) were investigated by analyzing the three-dimensional structural models of 23 representative MMPs.

Matrix metalloproteinase MMP-19 (RASI-1) is expressed on the surface of activated peripheral blood mononuclear cells and is detected as an autoantigen in rheumatoid arthritis

In order to characterize the autoimmune response participating in the pathogenesis of rheumatoid arthritis (RA) a cDNA expression library constructed from mRNAs which had been isolated from the inflamed synovium of an RA patients was screened with autologous IgG autoantibodies. This led to the identification of gene rasi-1 which encodes a protein showing sequence identity with the zinc-binding matrix metalloproteinase MMP-19. MMP-19 is detected on the surface of activated PBMCs, TH1 lymphocytes, and Jurkat T lymphoma cells. It exhibits gelatinolytic activity and is recognized by autoantibodies in 26% and, respectively, 33% of sera collected from RA patients and systemic lupus erythematosus (SLE) patients. The novel autoantigen MMP-19 thus could play a role in the pathological processes participating in RA-associated joint tissue destruction.

The matrix metalloproteinase RASI-1 is expressed in synovial blood vessels of a rheumatoid arthritis patient

RASI-1 is a novel matrix metalloproteinase which we isolated from an expression cDNA library representing the mRNA of an inflamed synovium obtained from a patient with rheumatoid arthritis (RA). To investigate the involvement of RASI-1 in the pathology of RA, we examined synovial specimens from RA patients with antibodies directed against an unique RASI-1-derived peptide. In comparison to interstitial collagenase, gelatinase A and B, and stromelysin 1, the RASI-1 expression in the RA-synovium is located mainly in the tunica media of blood vessel walls and its synovial localization is not as ubiquitous as that of other MMPs. The tissue inhibitor of metalloproteinases (TIMP-1), although also widely expressed in the synovium, exhibits strong colocalization with RASI-1 in blood vessel walls. While RASI-1 is expressed in blood vessels of the inflamed synovium of an RA patient, its expression was not found in control synovial specimens from patients with luxation and arthrosis. However, RASI-1 expression can also be found in non-inflamed blood vessels of uterine ligaments and skin. RASI-1, although its function and substrates are unknown, could be involved in processes such as neovascularization and angiogenesis or lymphocyte extravasation and thus may participate in joint tissue destruction during RA.

Identification and characterization of a novel human matrix metalloproteinase with unique structural characteristics, chromosomal location, and tissue distribution

We have cloned a novel member of the matrix metalloproteinase (MMP) family of proteins from a human liver cDNA library. The isolated cDNA contains an open reading frame coding for a polypeptide of 508 amino acids, which has been tentatively called MMP-19. This protein exhibits the domain structure characteristic of previously described MMPs, including a signal sequence, a prodomain with the cysteine residue essential for maintaining the latency of these enzymes, an activation locus with the zinc-binding site, and a COOH-terminal fragment with sequence similarity to hemopexin. However, it lacks a series of structural features distinctive of the diverse MMP subclasses, including the Asp, Tyr, and Gly residues located close to the zinc-binding site in collagenases, the fibronectin-like domain of gelatinases, the transmembrane domain of membrane-type (MT) MMPs, and the furin-activation sequence common to stromelysin-3 and MT-MMPs. In addition, the 9-residue insertion rich in hydrophobic amino acids present at the hinge region in stromelysins is replaced in MMP-19 by a longer insertion very rich in acidic residues. On the basis of these structural characteristics, we propose that MMP-19 does not belong to any of the previously defined MMP-subclasses and may represent the first member of a new MMP subfamily. Chromosomal location of the MMP-19 gene revealed that it maps to chromosome 12q14, which is also a unique location for any MMPs mapped to date. The cDNA encoding a full-length MMP-19 was expressed in Escherichia coli, and after purification and refolding, the recombinant protein was able to degrade synthetic substrates for MMPs. MMP-19 proteolytic activity was abolished by TIMP-2 and EDTA, thus providing additional evidence that the isolated cDNA codes for an authentic MMP. Northern blot analysis of polyadenylated RNAs isolated from a variety of human tissues revealed that MMP-19 is mainly expressed in placenta, lung, pancreas, ovary, spleen, and intestine, suggesting that it may play a specialized role in these tissues.

Identification of MMP-18, a putative novel human matrix metalloproteinase

A partial cDNA encoding the 3' end of a putative novel human matrix metalloproteinase (MMP) was identified by sequence similarity searching of databases containing expressed sequence tags. The remaining 5' end of the MMP cDNA was amplified by PCR from human mammary gland cDNA. The predicted protein product displays all the structural features characteristic of the MMP family and has closest identity with MMP-1, -3, -10, and 11. We have provisionally designated this novel MMP as MMP-18. MMP-18 mRNA is expressed in a wide variety of normal human tissues, including mammary gland, placenta, lung, pancreas, ovary, small intestine, spleen, thymus, prostate, testis, colon, and heart, but is not detected in brain, skeletal muscle, kidney, liver, or peripheral blood leucocytes.