Use of inhibitory (anti-catalytic) antibodies to study extracellular proteolysis

Matrix metalloproteinases

Matrix metalloproteinases are a class of enzymes that play an important role in the remodeling of the extracellular matrix in development and cancer metastasis. This unit describes a set of methods-cell-mediated dissolution of type I collagen fibrils, direct and reverse zymography, enzyme capture based on a-2 macroglubulin and TIMP-1 and -2, and demonstration of crytic thiol groups in metalloproteinase precursors-that are used to characterize the functions of matrix metalloproteinases and their inhibitors.

Interleukin-1 α Alters the Expression of Matrix Metalloproteinases and Collagen Degradation by Pulp Fibroblasts

Matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs) have been suggested to play a role in dental pulp destruction. This study examined the effects of interleukin (IL)-1 alpha on pulp fibroblasts. The ability of these cells to degrade collagen was determined with or without IL-1 alpha utilizing a cell-mediated collagen degradation assay. Reverse transcriptase-polymerase chain reaction was utilized to examine the mRNA expression of multiple MMPs and TIMPs with and without IL-1 alpha, while Western blot analyses and zymography were utilized to examine their protein expression. The collagen degradation mediated by these cells was stimulated by IL-1 alpha and inhibited by MMP inhibitors. IL-1 alpha increased the mRNA expression of MMP-1 and MMP-3, as well as induced MMP-7. Western blot analyses confirmed these results. IL-1 alpha increased the secreted protein level of TIMP-1, while only slightly affected the level of TIMP-2. These results suggest that IL-1 alpha can induce pulp destruction by differentially regulating MMPs and TIMPs.

Induction of collagenase-3 (MMP-13) in rheumatoid arthritis synovial fibroblasts

There is a growing body of evidence that implicates matrix metalloproteinases (MMPs) as major players in numerous diseased conditions. The articular cartilage degradation that is characteristic of rheumatoid arthritis (RA) is believed to be mediated by the collagenase subfamily of matrix metalloproteinases. The preference of collagenase-3 (CL-3) for collagen type II makes it a likely candidate in the turnover of articular cartilage and a potential target for drug development. In this study, RA synovial membrane tissue was shown to express CL-3 mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR) and protein by immunohistochemistry. Fibroblasts isolated and cultured from RA synovial membrane tissue were induced to express CL-3 mRNA. CL-3 mRNA was detected after PMA treatment in 16 of the 18 RA synovial membrane fibroblast cell lines established for this study. These fibroblasts also expressed mRNA for collagenase-1 (CL-1, MMP-1), membrane type-1 matrix metalloproteinase, gelatinase A, gelatinase B, stromelysin-1, stromelysin-2, TIMP-1, and TIMP-2. They were further shown to express CL-1 mRNA constitutively and CL-3 mRNA only after stimulation with PMA, IL-1, TGF-beta1, TNF-alpha, or IL-6 with IL-6sR. These fibroblasts also expressed after induction both CL-1 and CL-3 at the protein level as determined by Western blot analyses and immunofluorescence.

92K-GL (MMP-9) and 72K-GL (MMP-2) are produced in vivo by human oral squamous cell carcinomas and can enhance FIB-CL (MMP-1) activity in vitro

Previous studies have shown a correlation between the production of certain matrix metalloproteinases (MMPs), especially the gelatinases, by malignant tumors and the progression of these cancers as they invade and metastasize through the extracellular matrix and basement membranes. However, very few of these studies examined this relationship in human oral cancer in vivo, and none addressed the issue of how combinations of the MMPs may further enhance tumor progression. To determine which MMPs are produced in vivo by human oral cancers, we used specific anti-human-MMP antibodies and immunocytochemistry (ICC) methods to examine oral cancer tissue specimens from 20 surgery patients. The ICC data indicated that 72-kDa (72K-GL) and 92-kDa gelatinases (92K-GL) were produced in vivo by discreet clusters of tumor cells and by stromal fibroblasts, vascular endothelial cells (72K-GL), and PMNs (92K-GL). Some stromal fibroblasts near the tumors also appeared to produce fibroblast-type collagenase (FIB-CL), a finding confirmed by Western blot analysis of media conditioned by oral tumor explant cultures. ICC results indicated that 5 of the 20 tumors coincidentally produced all three MMPs. To examine how the two gelatinases and FIB-CL may interact in vitro to degrade fibrillar type I collagen, a major structural component of the extracellular matrix, we used a modified FIB-CL activity assay. Combinations of the gelatinases and FIB-CL were incubated with a 3H-collagen substrate, with the results compared with the combination of stromelysin-1 (SL-1, a superactivator of FIB-CL) and FIB-CL. 92K-GL caused a nine-fold increase in collagenase activity, equivalent to SL-1, while 72K-GL produced a four-fold increase. These results indicate that human oral cancers produce 92K-GL, 72K-GL, and FIB-CL in vivo and that the gelatinases and FIB-CL cooperate to enhance collagen degradation greatly in vitro.

Catalytic domain comparisons of human fibroblast-type collagenase, stromelysin-1, and matrilysin

The propeptide plus the catalytic domain of human fibroblast-type collagenase, stromelysin-1, and matrilysin were expressed in Escherichia coli to directly compare the properties of all three catalytic domains utilizing the same assays. Truncated fibroblast-type collagenase (mini-CL), truncated stromelysin-1 (mini-SL-1), and matrilysin, like their native counterparts, could be activated by organomercurials, trypsin, or SDS. The mini-CL and mini-SL-1 displayed catalytic properties similar to their native counterparts, except that the mini-CL could not cleave native type I collagen. The k(cat)/Km for matrilysin (355 microM(-1) h(-1)) on the synthetic Mca-peptide was much higher than that for mini-CL (69 microM(-1) h(-1)) or mini-SL-1 (23.6 microM(-1) h(-1)). Mini-SL-1 and matrilysin, but not mini-CL, were capable of superactivating collagenase thus increasing the rate of collagen cleavage. Mini-CL and mini-SL-1, but not matrilysin, were able to form SDS-stable complexes with TIMP-1 when co-incubated with an organomercurial and TIMP-1. The second-order rate constant (k(on)) for TIMP-1 inhibition of mini-CL and mini-SL-1 were similar, 0.635 x 10(5) M(-1) s(-1) and 1.52 x 10(5) M(-1) s(-1), respectively. The k(on) for TIMP-1 inhibition of matrilysin was lower (0.130 x 10(5) M(-1) s(-1)) supporting the observation that no SDS stable complexes were detected. This study demonstrates that these catalytic domains are distinct and play a major role in the specificity of these enzymes in regard to rate of catalysis, TIMP-1 binding, and superactivation of collagenase.

Matrix metalloproteinases: a review

Matrix metalloproteinases (MMPs) are a family of nine or more highly homologous Zn(++)-endopeptidases that collectively cleave most if not all of the constituents of the extracellular matrix. The present review discusses in detail the primary structures and the overlapping yet distinct substrate specificities of MMPs as well as the mode of activation of the unique MMP precursors. The regulation of MMP activity at the transcriptional level and at the extracellular level (precursor activation, inhibition of activated, mature enzymes) is also discussed. A final segment of the review details the current knowledge of the involvement of MMP in specific developmental or pathological conditions, including human periodontal diseases.

A model for interstitial collagen catabolism by mammalian collagenases

Mammalian collagenases cleave all three alpha chains of native, triple-helical types I, II, and III collagens after the Gly residue of the partial sequence Gly-[Ile or Leu]-[Ala or Leu] at a single locus approximately three-fourths from the amino terminus. There are an additional 31 sites in the triple-helical regions of types I, II, III, and IV collagens that contain the same partial sequence but are not hydrolyzed. A model has been developed to explain this remarkable specificity. The mammalian collagenase cleavage site in interstitial collagens is distinguished by: (a) a low side-chain molal volume-, high imino acid (greater than 33%)-containing region that is tightly triple-helical, consisting of four Gly-X-Y triplets preceding the cleavage site, (b) a low imino acid-containing (less than 17%), loosely triple-helical region consisting of four Gly-X-Y triplets following the cleavage site, and (c) a maximum of one charged residue for the entire 25 residue cleavage site region, which is always an Arg that follows the cleavage site in subsite P'5 or P'8. In addition, the high imino acid-containing region cannot have an imino acid adjacent to the cleaved Gly-[Ile or Leu] bond (i.e. in subsite P2). Careful scrutiny of the 31 non-cleaved sequences reveals that none of those sites shares all of the characteristics of the cleavage site. The criterion of this model thus explain both cleaved and non-cleaved sequences in the triple-helical regions of types I, II, III, and IV collagen, and are supported by all known experimental and theoretical results on collagen catabolism and structure.

Matrix metalloproteinase degradation of elastin, type IV collagen and proteoglycan. A quantitative comparison of the activities of 95 kDa and 72 kDa gelatinases, stromelysins-1 and -2 and punctuated metalloproteinase (PUMP)

The abilities of the matrix metalloproteinases 95 kDa and 72 kDa gelatinases (type IV collagenases), stromelysins-1 and -2 and punctuated metalloproteinase (PUMP) to degrade insoluble elastin, type IV collagen films and proteoglycan have been compared. The gelatinases and PUMP were markedly more active in the degradation of elastin than were the stromelysins. PUMP and the stromelysins were more potent proteoglycan-degrading enzymes. All of the enzymes studied degraded soluble native type IV collagen, but the gelatinases were more effective at higher temperatures. These quantitative data allow an analysis of the potential relative roles of these metalloproteinases in the breakdown of the key components of connective tissue matrices.

92-kD type IV collagenase mediates invasion of human cytotrophoblasts

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