| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Tumor Biology |
in Colorectal Cancer Generates an Increased Proteolytic Potential in the Stroma1
Institute of Biochemistry and Molecular Biology [D. L., D. H., E. E. S.], and Department of Visceral and Transplantation Surgery [C. A. M., M. W. B.], Inselspital, University of Bern, 3000 Bern, Switzerland
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
(E. C. 3.4.24.18, N-benzoyl-L-tyrosyl-p-aminobenzoic acid hydrolase), into the intestinal lumen. We found that Caco-2 cells, a colon carcinoma cell line, expressed endogenous meprin , which was secreted at both the basolateral and apical plasma membrane. The expression of meprin in colorectal cancer was confirmed using Northern blot analysis. On tissue sections, a diversity of carcinoma cells with varying immunoreactivity for meprin was observed. Western blots of a series of 11 paired samples of carcinomas and normal control colon tissue revealed that meprin protein accumulated at significant levels in 6 carcinomas at Union International Contre le Cancer tumor stages I–IV. In contrast, the protease was never detected in normal control tissue samples. Meprin zymogen was activated in the tumor tissue, as shown by a 3-fold increase in enzymatic activity. In conclusion, we describe a cancer-specific sorting of meprin , leading to a redistribution with consecutively increased proteolytic activity in the tumor stroma. Because the protease is known to cleave extracellular matrix components in vitro, meprin may contribute to tumor progression by facilitating migration, intravasation, and metastasis of carcinoma cells. |
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
and meprin ß (20
, 21)
, which are encoded at two independent gene loci (22)
.
The posttranslational processing of meprin and ß is different. Both are synthesized as type I transmembrane proteins in the endoplasmic reticulum, but whereas meprin ß is transported to the plasma membrane as a transmembrane protein, meprin is specifically retained in the endoplasmic reticulum to allow the removal of its membrane anchor, leading to its secretion into the extracellular medium (23
, 24)
. However, meprin also may be retained at the plasma membrane via dimerization with transmembrane meprin ß (21)
.
It has been shown for the mouse (25)
, as well as for the human enzyme (26)
, that meprin and ß are differentially expressed in the small and large intestines. Biosynthetic studies using organ-cultured human intestinal explants have shown that this leads to different proportions of cell surface-bound and secreted meprin . In the small intestine, both meprin and ß are expressed by intestinal epithelial cells, and meprin /ß oligomers accumulate at the brush border membrane of enterocytes. In contrast, epithelial cells of the colonic mucosa only express meprin , which, thus, is secreted into the intestinal lumen.
Meprin and meprin ß are typically sorted to the apical plasma membrane, as shown by the accumulation at the brush border membrane of enterocytes and the secretion into the intestinal lumen of the colon. Biosynthetic studies with transfected MDCK cells confirm an apical sorting of meprin and ß in polarized epithelial cells (21)
.
Here we show that meprin is endogenously expressed by Caco-2 cells, a human polarized colon carcinoma cell line (27)
, and that the protease is secreted both from the apical as well as from the basolateral plasma membrane. We hypothesized that in colorectal tumors in vivo, the basolateral secretion of meprin by colon carcinoma cells will expose extracellular matrix components and other stromal elements to an increased proteolytic potential in the vicinity of tumor cells. We, therefore, assessed the expression and proteolytic activity of this protease in colorectal tumors as compared with normal colon tissue.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
RT-PCR.
Total RNA was extracted from fresh mucosal scrapings of the small and large intestines of organ donors and from Caco-2 cells using the guanidine-isothiocyanate method (28)
. Reverse transcription was performed on 100 ng of total RNA, as previously described (29)
. Human meprin - and ß-specific sequences (corresponding to nucleotides 1808–2037 and 1449–1883, respectively) were amplified using the following primers at 1 µM (Microsynth, Windisch, Switzerland): human meprin -5': 5'-CGGGATCCAGACTGAAGTTCCCTCTAAAG-3'; human meprin -3': 5'-GGAATTCGGGTCACATGGGTCTCTGAAGTAC-3'; human meprin ß-5': 5'-CG-GGATCCATTTCCACTTGATCTCTGGAGCC-3'; human meprin ß-3': 5'-GGAATTCAGTGCAGACACCGTCATTTTTAC-3'.
BamHI and EcoRI restriction sites were included at 5' ends of these primers to facilitate the subcloning of PCR products.
Cell Culture, Biosynthetic Labeling, and Immunoprecipitation.
Caco-2 cells were cultured in the presence of 20% fetal bovine serum (Sigma Chemical Co., St. Louis, MO) in HEPES-buffered (25 mM) MEM containing 4.5 g/liter D-glucose, supplemented with nonessential amino acids (100 µM each), 2 mM glutamine, and 100 IE/ml penicillin/100 µg/ml streptomycin (culture medium and all supplements from Life Technologies, Inc., Paisley, United Kingdom). Caco-2 cells were labeled with 50 µCi [35S]methionine/[35S]cysteine (protein labeling mix; NEN, Boston, MA) at preconfluent and postconfluent time points. To analyze polarized transport of meprin , 5 x 105 cells were seeded onto 25-mm permeable filter supports (0.4 µm pore size; Falcon Becton Dickinson Europe, Meylan Cedex, France) and grown to 10 days after confluency. Establishment of a tight monolayer was followed by measuring the transepithelial resistance compared with a filter blank (filter support with culture medium only; Ref. 30
). Cells were pulse-labeled for 1 h with 50 µCi [35S]methionine/[35S]cysteine (protein labeling mix, NEN) in methionine-free culture medium and subsequently chased for 24 h with medium containing 10 mM cold methionine. Meprin was immunoprecipitated under denaturing conditions from cell lysates and from sterile filtered culture media using a rabbit antiserum directed against a 300 amino acid NH2-terminal region of human meprin . The antiserum recognizes both human meprin and ß (31)
. Radiolabeled meprin from cell lysates and culture media was analyzed by 7.5% SDS-PAGE under reducing conditions and fluorography.
Northern Blot Analysis.
32P-labeled RNA-probes were synthesized from 600 ng of linearized plasmids (pBluescript KS-; Stratagene, La Jolla, CA) containing human meprin and ß 5' coding sequences with low similarity (nucleotides 1808–2037 and 1449–1883, respectively), using T3 and T7 RNA polymerases (Boehringer Mannheim, Rotkreuz, Switzerland) in the presence of 50 µCi [32P]CTP (NEN). Total RNA (12 µg) from normal ileum, normal colon, and colorectal carcinoma tissue specimens was separated on a denaturing 1.2% agarose gel containing 1.8 M formaldehyde, blotted onto a nylon membrane (Genescreen; NEN), and hybridized sequentially with 32P-labeled human meprin - and ß-specific single-stranded RNA probes (32)
. Samples from pre- and postconfluent Caco-2 cells were probed sequentially with randomly labeled full-length cDNAs of meprin and of ß-actin.
Meprin - and ß-specific Immunohistochemistry.
Meprin - and ß-specific rabbit antisera directed against COOH-terminal regions with low similarity between human meprin and ß (encompassing amino acids 457–574 and amino acids 468–612, respectively) were generated using recombinant glutathione-S-transferase fusion proteins, as described elsewhere (26)
. The specificity of rabbit antisera was confirmed on Western blots, by immunoprecipitation, and by immunocytochemistry using MDCK wild type and meprin - or meprin ß-transfected cells (21
, 23)
.
Dewaxed and rehydrated 2-µm paraffin sections (on poly L-lysine-coated slides) were pretreated by boiling for 5 min in a microwave oven in 10 mM sodium citrate (pH 6.0) to denature and retrieve antigens and to suppress endogenous peroxidase activity. Sections were incubated with rabbit antisera or monoclonal antisucrase-isomaltase antibody HBB 3/705/60 (33) , biotinylated antirabbit or antimouse second antibodies, and an avidin-biotin-peroxidase complex (Vectastain ABC-Immunostaining Kit, Vector Laboratories, Burlingame, CA) in 25 mM Tris-HCl, and 140 mM sodium chloride (pH 7.5). Diaminobenzidine (Immuno Pure Metal Enhanced DAB; Pierce Chemical Co., Rockford, IL) was applied as a chromogenic substrate. Normal rabbit serum and a negative control monoclonal antibody (DAKO Diagnostics, Zug, Switzerland) were used as negative controls.
Western Blot Analysis of Tissue Homogenates of Colorectal Carcinomas and Normal Colonic Mucosa.
Paired samples of colorectal carcinomas and normal control mucosa were taken from 11 patients during elective tumor surgery. Using a teflon homogenizer, frozen tissue pieces (weight, 60–200 mg) were disrupted in 5 ml of ice-cold 1.5 mM KH2PO4, 8 mM Na2HPO4, and 138 mM NaCl (pH 7.3), containing protease inhibitors (1 µg/ml pepstatin, 1 µg/ml aprotinin, 5 µg/ml leupeptin, 17.4 µg/ml benzamidine, and 1.7 mM phenylmethylsulfonyl fluoride, all inhibitors from Sigma Chemical Co.). Homogenates were lysed for 1 h in the presence of 1% deoxycholic acid and 1% NP40 and adjusted to 1.2 mg of protein/ml (DC Protein assay kit; Bio-Rad Laboratories, Hercules, CA). Solubilized protein/sample (40 µg) were separated by 7.5% SDS-PAGE under reducing conditions and blotted for 1 h onto a polyvinylidene difluoride-membrane (Millipore, Bedford, MA) using the Mini-blot system from Bio-Rad. Further incubations were done using 20 mM Tris-HCl and 500 mM NaCl (pH 7.5). Membranes were probed with a combination of two antisera against COOH-terminal (see immunohistochemistry) and NH2-terminal regions of meprin (Ref. (31)
; 1:500 and 1:1000, respectively, in 1% dry milk). Meprin-specific bands were visualized using enhanced chemiluminescence (ECL-Kit; Amersham Life Sciences, Buckinghamshire, Great Britain) using a peroxidase-coupled antirabbit second antibody (1:10,000 in 1% dry milk). X-ray films were exposed for 15 min.
Meprin Proteolytic Activity: Paba-peptide Assay.
To avoid interference with the paba-peptide assay, endogenous nonmetalloprotease activity in the intestinal tissue was suppressed by the addition of protease inhibitors before homogenization (1 µg/ml pepstatin, 1 µg/ml aprotinin, 5 µg/ml leupeptin, 17.4 µg/ml benzamidine, and 1.7 mM phenylmethylsulfonyl fluoride, all inhibitors from Sigma Chemical Co.). Tissue homogenate (100 µl, containing 120 µg of solubilized protein) was mixed with 100 µl of 40 mM paba-peptide (Bachem AG, Bubendorf, Switzerland) in 50 mM Tris-HCl, and 1 mM MgCl2 (pH 7.5), supplemented with 0.5 mM phenylmethylsulfonyl fluoride (Sigma Chemical Co.), and incubated for 6 h at 37°C. Released benzoic acid was determined using the colorimetric assay according to Bratton-Marshall. After subtraction of absorptions in the presence of 10 mM EDTA, paba-peptide hydrolytic activity of homogenates were expressed in IU/g protein. Paba-peptide hydrolysis was inhibited with 10 mM EDTA, but was not affected by 1 µM phosphoramidon (Sigma Chemical Co.), which is in accordance with the inhibitory profile of meprin (18)
. Background values of normal colon mucosa varied from one patient to another. Paba-peptide hydrolytic activities of colorectal carcinomas were, therefore, related to the normal colon mucosa samples of each patient by calculating the ratio between enzyme activity in carcinoma tissue and normal colonic tissue. An enriched small intestinal brush border membrane preparation was used as a positive control. The statistical significance of the increase in proteolytic activity in meprin -positive as compared with meprin -negative tumors was confirmed by the two-tailed Wilcoxon rank sum test.
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
in Differentiated Caco-2 Cells. (Fig. 1A)
. Reverse transcription and PCRs with meprin -specific primers on total RNA from human small and large intestines and from Caco-2 cells yielded identical amplimers in all three cases, whereas using meprin ß-specific primers, only the reaction with RNA from the small intestine generated the expected DNA species. Expression of meprin in Caco-2 cells was further confirmed on the protein level by a Western blot analysis (data not shown).
|
depends on the differentation status, we analyzed Caco-2 cells during the growth phase and at postconfluency (Fig. 1, B and C)
. Transcription (Fig. 1B)
and protein synthesis (Fig. 1C)
of meprin were up-regulated in postconfluent cell cultures, but were not detectable in proliferating cells. The 100,000-Da and 85,000-Da proteins in cells correspond to the endoplasmic reticulum-resident precursor and proteolytically processed forms of meprin (23)
.
The Caco-2 cell line was used as an in vitro model to investigate biosynthesis and secretion of meprin in colon carcinoma cells (Fig. 2)
. Pulse-chase experiments were performed in 10-day postconfluent cells grown in a transwell culture system with separate basolateral and apical compartments. Meprin was immunoprecipitated from cell lysates, as well as from apical and basolateral media compartments, and analyzed by SDS-PAGE and fluorography. After a 24-h chase, the secreted 95,000-Da form of meprin was detected in the apical and at significant higher amounts in the basolateral compartment. The 85,000-Da polypeptide in cells corresponds to the COOH-terminally trimmed form of meprin in the endoplasmic reticulum (23)
.
|
, but not Meprin ß, Is Expressed in the Normal Colon and in Colorectal Carcinomas.-specific and meprin ß-specific RNA probes (Fig. 3)
. Meprin , but not meprin ß, was expressed in the normal colon (Fig. 3
, Lanes 2–6), whereas both were detected in the ileum (Fig. 3
, Lane 1), thus confirming the differential expression of meprin in the intestine. A single 3.5-kb transcript for meprin was detected weakly in one tumor sample (Fig. 3A
, Lane 7) and at significant levels in four tumor samples (Fig. 3A
, Lanes 8–11), indicating that meprin is frequently expressed in colorectal cancer. No aberrant meprin transcripts were evident in tumors. As in the normal colon, meprin ß mRNA was not detected in the tumor samples (Fig. 3B
, Lanes 7–11). Signals for meprin were much stronger in the ileum as compared with carcinoma and normal colon tissue samples, probably reflecting a higher epithelial cell content and/or higher expression level in the ileum.
|
- and meprin ß-specific immunohistochemistry on tissue sections of colorectal tumors, meprin -positive carcinoma cells were readily identified (Fig. 4A)
, whereas on consecutive tissue sections, meprin ß was not detected in the same tumor (Fig. 4B)
. A single carcinoma cell typically displayed a uniform staining of the cell body. In a given tumor region, however, a mosaic staining pattern for meprin was observed, as carcinoma cells with strong immunoreactivity neighbored cells with weak or undetectable signals for meprin . Stromal cells did not exhibit immunoreactivity for meprin.
|
in Colorectal Carcinomas, but not in Normal Colon. from both basolateral and apical plasma membranes in vitro; (b) colorectal carcinomas frequently express meprin mRNA; and (c) carcinoma cells are production sites for meprin in the tumors. We, therefore, hypothesized that the expression and nonpolarized secretion of meprin by colon carcinoma cells leads to the accumulation of the protease in the tumor.
To test this hypothesis, we performed a Western blot analysis of a series of 11 samples of UICC tumor stages I-IV in comparison with normal control colon tissue from the same patients (Fig. 5)
. Multiple forms of meprin , ranging from 75,000–95,000 Da, were detected in 6 of 11 tumor homogenates. In marked contrast, meprin levels in normal colon tissue were always below detection limit. Isolated 70,000-Da bands seen in some samples were not characterized further, but were clearly smaller than known intracellular or secreted forms of meprin and were not associated with a proteolytic activity in these tissue samples. We refer to those colorectal carcinomas, which accumulate meprin protease, as "meprin -positive." An association of meprin protein accumulation with tumor stages (Table 1)
was not observed.
|
|
Is Active in Colorectal Cancer. protease activity. We, therefore, measured meprin activity in tissue homogenates using paba-peptide as substrate (Ref. 18
; Fig. 6
). In meprin -positive carcinomas, the paba-peptide hydrolyzing activity was 2.9-fold higher than in the corresponding normal colon mucosa, whereas in meprin -negative carcinomas, this activity was equal to the corresponding normal colon mucosa. Hence, accumulation of meprin was accompanied by an increased enzyme activity in meprin -positive carcinomas (Table 1)
.
|
in Colorectal Cancer Is Independent of Sucrase-isomaltase. is not linked to the induction of sucrase-isomaltase (Table 1)
. |
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
. Using this cell line as an in vitro model to study the sorting of meprin , we demonstrate that an important portion of secreted meprin is targeted basolaterally. This observation, in conjunction with an investigation of the accumulation and enzymatic activity of meprin in colorectal cancers in vivo, is the basis for the description of a tumor-specific mechanism, which leads to a redistribution of the proteolytic potential of meprin from the intestinal lumen to the tumor stroma in colorectal cancer.
Intestinal epithelial cells transport meprin apically. This is supported by the accumulation of meprin together with membrane-bound meprin ß at the apical cell membrane of enterocytes in the small intestine and by its secretion from the mucosal surface into the intestinal lumen in the colon (26)
. In transfected MDCK cells, a polarized kidney epithelial cell line, meprin is also secreted apically (21)
. In contrast, differentiated Caco-2 cells target meprin to the apical as well as the basolateral medium compartment (Fig. 2)
, distinguishing the colon carcinoma cells from nontransformed epithelial cells. A similar discrepancy has been observed with a recombinant secretory mutant of aminopeptidase N, which is secreted exclusively from the apical plasma membrane in MDCK cells (36)
, but from both basolateral and apical plasma membranes in Caco-2 cells (37)
.
Like MDCK cells, Caco-2 cells are polarized epithelial cells. Yet, the sorting mechanisms for polarized protein transport are different in these two cell types (30
, 38)
. Sorting of apical proteins occurs directly from the trans-Golgi in MDCK cells and seems to depend on sorting signals in the ectodomain (36)
. Meprin is secreted via this direct apical transport route in these cells. In contrast, Caco-2 cells display an additional indirect apical transport route via transcytosis from the basolateral plasma membrane (39, 40, 41)
. Efficient transcytosis of proteins in Caco-2 cells depends on the anchorage to the plasma membrane, as shown by the basolateral secretion of an important portion of a secretory mutant of aminopeptidase N (37)
. In analogy, secreted meprin , following both the apical and indirect basolateral route in Caco-2 cells, cannot be scavenged for transcytosis to the apical domain after the release at the basolateral plasma membrane. Therefore, the altered sorting mechanism in Caco-2 cells explains the nonpolarized secretion of meprin .
We present evidence that similarly to Caco-2 cells, carcinoma cells in colon tumors also secrete meprin at the basolateral side. First, meprin was evenly distributed at the apical and basolateral domains of carcinoma cells on immunostainings of tumor tissue sections. Second, the analysis of a series of colorectal tumor samples on Western blots revealed a high prevalence of an accumulation of meprin protein in tumors. In contrast, meprin was below detection limit in normal control colon tissue from the same patients, confirming its rapid secretion from the normal mucosal surface. Similarly, in a study on the expression of meprin in mouse intestine, meprin has not been detected on Western blots of normal mouse colon, despite positive mRNA signals on Northern blots (25)
. In vivo, the basolateral plasma membrane of colon carcinoma cells faces the tumor stroma. Therefore, meprin , which normally is secreted at the apical plasma membrane and targeted to the intestinal lumen, aberrantly accumulates in the stroma in colorectal tumors (Fig. 7)
.
|
-positive tumors harbored multiple molecular forms of meprin ranging from 75,000–95,000 Da, yet secreted meprin in Caco-2 cells is a 95,000-Da protein. This discrepancy most probably arises from heterogenous glycosylation and/or NH2- or COOH-terminal trimming of the protein in colorectal tumors.
The mosaic expression pattern in a given meprin -positive tumor may result from the polyclonal origin of colorectal carcinomas (42)
and/or deregulated and variable expression in carcinoma cells, as opposed to the restricted expression by terminally differentiated intestinal epithelial cells in the normal mucosa (43)
. However, as meprin is up-regulated in differentiated Caco-2 cells, we assume that differentiated carcinoma cells in a colon tumor generate the proteolytic activity in the stroma. Whether meprin -positive or -negative carcinoma cell populations differ in their invasive and/or metastatic capacity remains to be investigated.
Using the paba-peptide assay, we demonstrate that, in meprin -positive tumors, the accumulated protease is at least partially active in situ, which further supports a function in colorectal cancer (Fig. 6)
. Yet meprin is synthesized as a zymogen, and only proteolytic removal of the propeptide will yield active protease. Trypsin is a potent activator of meprin in vitro (23)
, and it is thought that luminal trypsin activates brush border-associated and secreted meprin in the intestine in vivo. As luminal trypsin has no access to the tumor stroma, an alternate activation mechanism must exist in colorectal tumors. We suggest that colon carcinoma cells by themselves may contribute to the activation of meprin . Candidate-activating proteases are tumor-associated trypsinogen-1 and -2, which have been reported to be expressed by several cancer cell lines including colon carcinoma cells (44, 45, 46)
. The activation of meprin by such carcinoma cell-derived proteases in situ will build up a high proteolytic activity in the immediate vicinity of the carcinoma cells. Proteases from other cells may also activate meprin . Indeed, there is a recent study of endothelial cells expressing trypsin (47)
, which may link the activation of secreted zymogens like meprin to tumor angiogenesis (Fig. 7)
.
An important carcinoma cell-associated function is to facilitate invasion and metastasis. This process ultimately depends on the degradation of the extracellular matrix. A role of meprin during this process is suggested by the previously reported capacity of meprin to degrade extracellular matrix components like collagen type IV, fibronectin, and laminin in vitro (19) . There is a very recent study in support of our model, that describes meprin as an extracellular matrix degrading activity in ischemic renal injury (48) . It is proposed that this is the consequence of tubular epithelial cells redistributing the protease to the basolateral domain.
In conclusion, we have presented evidence for a role of meprin in colorectal cancer. We have shown an altered sorting of meprin in colorectal carcinoma cells leading to an aberrant accumulation of meprin in the tumor stroma, thus resulting in a proteolytic potential, which can be activated by proteases from carcinoma cells or from cells in the tumor stroma. Thus far, meprin has been thought to have a luminal function in the intestine. For the first time, we present direct evidence for a possible tissue-related function of meprin.
A correlation of meprin expression with tumor stages was not attempted on the small number of samples investigated However, we find meprin expressed in tumors of all stages, suggesting a potential role of this protease during early, as well as during late, phases in tumor progression. To further explore the role of meprin in the progression of colorectal cancer in vivo, additional studies will focus on differences in the prognosis of meprin -positive versus meprin -negative colon tumors and on the role of meprin during metastasis.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
1 Supported by Swiss National Science Foundation Grant 32-40571.94 (to E. E. S.) and by a fellowship from the "Sonderprogramm akademische Nachwuchsförderung" by the Swiss Government (to D. L.). 
2 To whom requests for reprints should be addressed, at Institute of Biochemistry and Molecular Biology, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland. E-mail: erwin.sterchi{at}mci.unibe.ch
3 The abbreviations used are: paba-peptide, N-benzoyl-L-tyrosyl-p-aminobenzoic acid; MDCK, Madin Darby canine kidney; RT-PCR, reverse transcription-PCR; UICC, Union International Contre le Cancer.
Received 7/ 1/98. Accepted 12/31/98.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
and ß subunits in Madin-Darby canine kidney cells. Eur. J. Biochem., 247: 920-932, 1997.[Medline]
and ß subunits of the metalloendopeptidase meprin map to human chromosomes 6p and 18q, respectively. Genomics, 25: 300-303, 1995.[Medline]
subunit of PABA peptide hydrolase (EC 3.4.24.18) in MDCK cells. Synthesis and secretion of an enzymatically inactive homodimer. FEBS Lett., 335: 376-379, 1993.[Medline]
subunit (human meprin ) are essential for its retention in the endoplasmic reticulum and C-terminal processing. Eur. J. Biochem., 247: 933-941, 1997.[Medline]
and ß subunits. Eur. J. Biochem., 259: 496-504, 1999.[Medline]
subunit (PPH ) from human small intestine and its expression in COS-1 cells. FEBS Lett., 335: 367-375, 1993.[Medline]
This article has been cited by other articles:
|
|
 |
|
  V. A Heinzelmann-Schwarz, R. A Scolyer, J. P Scurry, A. N Smith, M. Gardiner-Garden, A. V Biankin, S. Baron-Hay, C. Scott, R. L Ward, D. Fink, et al. Low meprin {alpha} expression differentiates primary ovarian mucinous carcinoma from gastrointestinal cancers that commonly metastasise to the ovaries J. Clin. Pathol., June 1, 2007; 60(6): 622 - 626. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. S. Ishmael, F. T. Ishmael, A. D. Jones, and J. S. Bond Protease Domain Glycans Affect Oligomerization, Disulfide Bond Formation, and Stability of the Meprin A Metalloprotease Homo-oligomer J. Biol. Chem., December 8, 2006; 281(49): 37404 - 37415. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Hirano, B. Y. Ma, N. Kawasaki, K. Okimura, M. Baba, T. Nakagawa, K. Miwa, N. Kawasaki, S. Oka, and T. Kawasaki Mannan-Binding Protein Blocks the Activation of Metalloproteases Meprin {alpha} and {beta} J. Immunol., September 1, 2005; 175(5): 3177 - 3185. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Quesada, L. M. Sanchez, J. Alvarez, and C. Lopez-Otin Identification and Characterization of Human and Mouse Ovastacin: A NOVEL METALLOPROTEINASE SIMILAR TO HATCHING ENZYMES FROM ARTHROPODS, BIRDS, AMPHIBIANS, AND FISH J. Biol. Chem., June 18, 2004; 279(25): 26627 - 26634. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hahn, A. Pischitzis, S. Roesmann, M. K. Hansen, B. Leuenberger, U. Luginbuehl, and E. E. Sterchi Phorbol 12-Myristate 13-Acetate-induced Ectodomain Shedding and Phosphorylation of the Human Meprin{beta} Metalloprotease J. Biol. Chem., October 31, 2003; 278(44): 42829 - 42839. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. P. Norman, W. Jiang, X. Han, T. L. Saunders, and J. S. Bond Targeted Disruption of the Meprin {beta} Gene in Mice Leads to Underrepresentation of Knockout Mice and Changes in Renal Gene Expression Profiles Mol. Cell. Biol., February 15, 2003; 23(4): 1221 - 1230. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. P. Bertenshaw, M. T. Norcum, and J. S. Bond Structure of Homo- and Hetero-oligomeric Meprin Metalloproteases. DIMERS, TETRAMERS, AND HIGH MOLECULAR MASS MULTIMERS J. Biol. Chem., January 17, 2003; 278(4): 2522 - 2532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Rosmann, D. Hahn, D. Lottaz, M.-N. Kruse, W. Stocker, and E. E. Sterchi Activation of Human Meprin-alpha in a Cell Culture Model of Colorectal Cancer Is Triggered by the Plasminogen-activating System J. Biol. Chem., October 18, 2002; 277(43): 40650 - 40658. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Kadowaki, T. Tsukuba, G. P. Bertenshaw, and J. S. Bond N-Linked Oligosaccharides on the Meprin A Metalloprotease Are Important for Secretion and Enzymatic Activity, but Not for Apical Targeting J. Biol. Chem., August 11, 2000; 275(33): 25577 - 25584. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||
