Proteomic discovery of substrates of the cardiovascular protease ADAMTS7

The protease ADAMTS7 functions in the extracellular matrix (ECM) of the cardiovascular system. However, its physiological substrate specificity and mechanism of regulation remain to be explored. To address this, we conducted an unbiased substrate analysis using terminal amine isotopic labeling of substrates (TAILS). The analysis identified candidate substrates of ADAMTS7 in the human fibroblast secretome, including proteins with a wide range of functions, such as collagenous and noncollagenous extracellular matrix proteins, growth factors, proteases, and cell-surface receptors. It also suggested that autolysis occurs at Glu-729-Val-730 and Glu-732-Ala-733 in the ADAMTS7 Spacer domain, which was corroborated by N-terminal sequencing and Western blotting. Importantly, TAILS also identified proteolysis of the latent TGF-β-binding proteins 3 and 4 (LTBP3/4) at a Glu-Val and Glu-Ala site, respectively. Using purified enzyme and substrate, we confirmed ADAMTS7-catalyzed proteolysis of recombinant LTBP4. Moreover, we identified multiple additional scissile bonds in an N-terminal linker region of LTBP4 that connects fibulin-5/tropoelastin and fibrillin-1-binding regions, which have an important role in elastogenesis. ADAMTS7-mediated cleavage of LTBP4 was efficiently inhibited by the metalloprotease inhibitor TIMP-4, but not by TIMP-1 and less efficiently by TIMP-2 and TIMP-3. As TIMP-4 expression is prevalent in cardiovascular tissues, we propose that TIMP-4 represents the primary endogenous ADAMTS7 inhibitor. In summary, our findings reveal LTBP4 as an ADAMTS7 substrate, whose cleavage may potentially impact elastogenesis in the cardiovascular system. We also identify TIMP-4 as a likely physiological ADAMTS7 inhibitor.

Targeting a Designer TIMP-1 to the Cell Surface for Effective MT1-MMP Inhibition: A Potential Role for the Prion Protein in Renal Carcinoma Therapy

Renal carcinoma cells express Membrane Type 1-Matrix Metalloproteinase (MT1-MMP, MMP-14) to degrade extracellular matrix components and a range of bioactive molecules to allow metastasis and cell proliferation. The activity of MT1-MMP is modulated by the endogenous inhibitors, Tissue Inhibitor of Metalloproteinases (TIMPs). In this study, we describe a novel strategy that would enable a "designer" TIMP-1 tailored specifically for MT1-MMP inhibition (V4A/P6V/T98L; K_i^app 1.66 nM) to be targeted to the plasma membrane for more effective MT1-MMP inhibition. To achieve this, we fuse the designer TIMP-1 to the glycosyl-phosphatidyl inositol (GPI) anchor of the prion protein to create a membrane-tethered, high-affinity TIMP variant named "T1^{Pr αMT1}" that is predominantly located on the cell surface and co-localised with MT1-MMP. Confocal microscopy shows that T1^{Pr αMT1} is found throughout the cell surface in particular the membrane ruffles where MT1-MMP is most abundant. Expression of T1^{Pr αMT1} brings about a complete abrogation of the gelatinolytic activity of cellular MT1-MMP in HT1080 fibrosarcoma cells whilst in renal carcinoma cells CaKi-1, the GPI-TIMP causes a disruption in MMP-mediated proteolysis of ECM components such as fibronectin, collagen I and laminin that consequently triggers a downstream senescence response. Moreover, the transduced cells also suffer from an impairment in proliferation and survival in vitro as well as in NOD/SCID mouse xenograft. Taken together, our findings demonstrate that the GPI anchor of prion could be exploited as a targeting device in TIMP engineering for MT1-MMP inhibition with a potential in renal carcinoma therapy.

TIMP-1 Promotes Oligodendrocyte Differentiation Through Receptor-Mediated Signaling

The extracellular protein tissue inhibitor of metalloproteinase (TIMP)-1 is both a matrix metalloproteinase (MMP) inhibitor and a trophic factor. Mice lacking TIMP-1 exhibit delayed central nervous system myelination during postnatal development and impaired remyelination following immune-mediated injury in adulthood. We have previously determined that the trophic action of TIMP-1 on oligodendrocyte progenitor cells (OPCs) to mature into oligodendrocytes is independent of its MMP inhibitory function. However, the mechanism by which TIMP-1 promotes OPC differentiation is not known. To address this gap in our understanding, herein, we report that TIMP-1 signals via a CD63/β1-integrin receptor complex to activate Akt (protein kinase B) to promote β-catenin signaling in OPCs. The regulation of β-catenin by TIMP-1 to promote OPC differentiation was counteracted, but not abrogated, by canonical signaling evoked by Wnt7a. These data provide a previously uncharacterized trophic action of TIMP-1 to regulate oligodendrocyte maturation via a CD63/β1-integrin/Akt pathway mechanism. These findings contribute to our emerging understanding on the role of TIMP-1 as a growth factor expressed to promote CNS myelination during development and induced in the adult to promote myelin repair.

Molecular characterization and hormonal regulation of tissue inhibitor of metalloproteinase 1 in goat ovarian granulosa cells

Tissue inhibitor of metalloproteinase 1 (TIMP1) belongs to a group of endogenous inhibitors that control the activity of matrix metalloproteinases and other metalloproteinases. TIMP1 is ubiquitously expressed and implicated in many physiological and pathologic processes. In this study, the full-length complementary DNA of goat (Capra hircus) Timp1 was cloned from adult goat ovary for the first time to better understand the regulatory role of TIMP1. The putative TIMP1 protein shared a high amino acid sequence identity with other species. Real-time polymerase chain reaction results showed that Timp1 was widely expressed in adult goat tissues, and messenger RNA expression was higher in the ovary than in other tissues; meanwhile, increasing expression of Timp1 was also discovered during the process of follicle growth and corpus luteum. We then investigated Timp1 expression patterns in different types of ovarian follicular cells from goats. In small or large antral follicles, Timp1 expression was higher (P < 0.05) in theca cells than in granulosa cells, cumulus cells, and oocytes. Increasing expression of Timp1 in theca and granulosa cells was observed as the variation of the follicle size. Immunohistochemical analyses further revealed the presence of the TIMP1 proteins in follicles at all antral stages of development. The most intense staining for TIMP1 was observed in the theca cells and granulosa cells of large antral follicles and corpus luteum. Timp1 was highly (P < 0.05) induced in granulosa cells in vitro after treatment with the luteinizing hormone agonist, human chorionic gonadotropin. Treatments with forskolin, phorbol 12-myristate 13-acetate, or phorbol 12-myristate 13-acetate + forskolin could also stimulate Timp1 messenger RNA expression. The effects of human chorionic gonadotropin were reduced (P < 0.05) by the inhibitors of protein kinase A, protein kinase C, MAPK kinase, or p38 kinase, indicating that Timp1 expression could be adjusted by luteinizing hormone-initiated activation of these signaling mediators. Our results suggested that TIMP1 may be involved in regulating ovarian follicle development and ovulation.

[Airway remodeling assessed by high-resolution computed tomography in patients with asthma: relationship to biological markers in induced sputum]

OBJECTIVE

To explore the significance of assessing asthma control by high-resolution computed tomography (HRCT) and biological markers in induced sputum.

METHODS

Forty-eight patients with asthma (asthma group) and 10 healthy subjects (control group) were retrospectively analyzed. The asthma patients were divided into 4 groups based on severity: 6 with near-fatal attacks, 12 with severe, 14 with moderate and 16 with mild asthma. These patients received step therapy for 6 months based on the guidelines for the prevention and treatment of asthma. After achieving asthma control or partial control, HRCT, lung function and cytokine levels in induced sputum were measured. The ratio of wall area to total airway area (WA%), the ratio of 2 airway wall thickness to outer diameter (2T/D) and lung densities in both the inspiratory and expiratory phases were measured. Matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinases-1 (TIMP-1), and transformation growth factor-β(1) (TGF-β(1)) levels in the sputum were assessed by enzyme-linked immunosorbent assay.

RESULTS

There were significant differences in forced vital capacity and forced expiratory volume in 1 second as the percentage of predicted value (FVC% and FEV(1)%, respectively), the ratio of FEV(1)/FVC, and diffusing capacity of the lung for carbon monoxide (D(LCO)) among groups (F = 5.526, 15.064, 16.326, 2.945, respectively, P < 0.05). Sputum levels of MMP-9, TIMP-1 and TGF-β(1) were significantly increased in the near-fatal asthma, severe asthma, moderate asthma and mild asthma groups [MMP-9: (80 ± 16), (70 ± 9), (59 ± 6), and (52 ± 7) µg/L, respectively; TIMP-1: (212 ± 95), (258 ± 167), (28 ± 51), and 98 ± 60 µg/L, respectively; TGF-β(1): (586 ± 81), (513 ± 54), (401 ± 45) and (351 ± 57) µg/L, respectively]compared with the control group [MMP9: (46 ± 5) µg/L; TIMP: (19 ± 13) µg/L; and TGF-β(1): (258 ± 29) µg/L]. These parameters were progressively increased in the asthma groups with the severity of disease (F = 11.179, 49.914, 9.286, respectively, P < 0.05). The ratio of MMP-9/TIMP-1 in sputum was decreased in the near-fatal attack, severe, moderate and mild asthma groups (0.50 ± 0.28, 0.34 ± 0.13, 0.53 ± 0.22, and 0.87 ± 0.75, respectively) compared with the control group (2.93 ± 1.13). The MMP-9/TIMP-1 ratio in the severe asthma group was lowest among the asthma groups (F = 43.335, P < 0.05). 2T/D and WA% were higher in both the near-fatal asthma group (0.51 ± 0.01 and 0.75 ± 0.01, respectively) and the severe asthma group (0.53 ± 0.03 and 0.77 ± 0.03, respectively) as compared to the moderate asthma group (0.43 ± 0.04 and 0.67 ± 0.04, respectively) or the mild group (0.42 ± 0.04 and 0.66 ± 0.04, respectively). 2T/D and WA% were higher in the asthma groups than in the control group (0.35 ± 0.03 and 0.57 ± 0.04, respectively), (F = 40.224, 41.294, respectively, P < 0.05). Lung densities in both the inspiratory and expiratory phases were lower in the near-fatal attack group as compared to those in the other asthma groups or the control group; and the lung density differences between the two phases in the near-fatal attack group were smaller than those in the other asthma groups or the control group (F = 5.048, 13.247, 11.541, respectively, P < 0.05). 2T/D and WA% were correlated positively with MMP-9, TIMP-1 and TGF-β(1) levels, but negatively with the MMP-9/TIMP-1 ratio, respectively.

CONCLUSIONS

HRCT and biological markers in induced sputum could be used to accurately evaluate asthma control. These findings suggest that the severity of asthma, especially, near-fatal attack of asthma, is correlated not only with the degree of airway remodeling, but also with the degree of air trapping.

PEGylation extends circulation half-life while preserving in vitro and in vivo activity of tissue inhibitor of metalloproteinases-1 (TIMP-1)

Excess proteolytic activity of matrix metalloproteinases (MMPs) contributes to the development of arthritis, cardiovascular diseases and cancer progression, implicating these enzymes as therapeutic targets. While many small molecule inhibitors of MMPs have been developed, clinical uses have been limited, in part by toxicity and off-target effects. Development of the endogenous tissue inhibitors of metalloproteinases (TIMPs) as recombinant biopharmaceuticals represents an alternative therapeutic approach; however, the short plasma half-life of recombinant TIMPs has restricted their potential in this arena. To overcome this limitation, we have modified recombinant human TIMP-1 (rhTIMP-1) by PEGylation on lysine residues. We analyzed a mixture of mono- and di-PEGylated rhTIMP-1 species modified by attachment of 20 kDa mPEG chains (PEG(20K)-TIMP-1), as confirmed by SELDI-TOF mass spectrometry. This preparation retained complete inhibitory activity toward the MMP-3 catalytic domain and partial inhibitory activity toward full length MMP-9. Pharmacokinetic evaluation showed that PEGylation extended the plasma half-life of rhTIMP-1 in mice from 1.1 h to 28 h. In biological assays, PEG(20K)-TIMP-1 inhibited both MMP-dependent cancer cell invasion and tumor cell associated gelatinase activity. Overall these results suggest that PEGylated TIMP-1 exhibits improved potential for development as an anti-cancer recombinant protein therapeutic, and additionally may offer potential for clinical applications in the treatment of other diseases.

An integrin-binding N-terminal peptide region of TIMP-2 retains potent angio-inhibitory and anti-tumorigenic activity in vivo

Tissue inhibitor of metalloproteinases-2 (TIMP-2) inhibits angiogenesis by several mechanisms involving either MMP inhibition or direct endothelial cell binding. The primary aim of this study was to identify the TIMP-2 region involved in binding to the previously identified receptor integrin α3β1, and to determine whether synthetic peptides derived from this region retained angio-inhibitory and tumor suppressor activity. We demonstrated that the N-terminal domain of TIMP-2 (N-TIMP-2) binds to α3β1 and inhibits vascular endothelial growth factor-stimulated endothelial cell growth in vitro, suggesting that both the α3β1-binding domain and the growth suppressor activity of TIMP-2 localize to the N-terminal domain. Using a peptide array approach we identify a 24 amino acid region of TIMP-2 primary sequence, consisting of residues Ile43-Ala66, which shows α3β1-binding activity. Subsequently we demonstrate that synthetic peptides from this region compete for TIMP-2 binding to α3β1 and suppress endothelial growth in vitro. We define a minimal peptide sequence (peptide 8-9) that possesses both angio-inhibitory and, using a murine xenograft model of Kaposi's sarcoma, anti-tumorigenic activity in vivo. Thus, both the α3β1-binding and the angio-inhibitory activities co-localize to a solvent exposed, flexible region in the TIMP-2 primary sequence that is unique in amino acid sequence compared with other members of the TIMP family. Furthermore, comparison of the TIMP-2 and TIMP-1 protein 3-D structures in this region also identified unique structural differences. Our findings demonstrate that the integrin binding, tumor growth suppressor and in vivo angio-inhibitory activities of TIMP-2 are intimately associated within a unique sequence/structural loop (B-C loop).

Comparison of metalloproteinase protein and activity profiling

Proteolytic enzymes play fundamental roles in many biological processes. Members of the matrix metalloproteinase (MMP) family have been shown to take part in processes crucial in disease progression. The current study used the ExcelArray Human MMP/TIMP Array to quantify MMP and tissue inhibitor of metalloproteinase (TIMP) production in the lysates and media of 14 cancer cell lines and 1 normal cell line. The overall patterns were very similar in terms of which MMPs and TIMPs were secreted in the media versus associated with the cells in the individual samples. However, more MMP was found in the media (in both amount and variety). TIMP-1 was produced in all cell lines. MMP activity assays with three different fluorescence resonance energy transfer (FRET) substrates were then used to determine whether protein production correlated with function for the WM-266-4 and BJ cell lines. Metalloproteinase activity was observed for both cell lines with a general MMP substrate (Knight SSP), consistent with protein production data. However, although both cell lines promoted the hydrolysis of a more selective MMP substrate (NFF-3), metalloproteinase activity was confirmed only in the BJ cell line. The use of inhibitors to confirm metalloproteinase activities pointed to the strengths and weaknesses of in situ FRET substrate assays.

A biochemical model of matrix metalloproteinase 9 activation and inhibition

Matrix metalloproteinases (MMPs) are a class of extracellular and membrane-bound proteases involved in an array of physiological processes, including angiogenesis. We present a detailed computational model of MMP9 activation and inhibition. Our model is validated to existing biochemical experimental data. We determine kinetic rate constants for the processes of MMP9 activation by MMP3, MMP10, MMP13, and trypsin; inhibition by the tissue inhibitors of metalloproteinases (TIMPs) 1 and 2; and MMP9 deactivation. This computational approach allows us to investigate discrepancies in our understanding of the interaction of MMP9 with TIMP1. Specifically, we find that inhibition due to a single binding event cannot describe MMP9 inhibition by TIMP1. Temporally accurate biphasic inhibition requires either an additional isomerization step or a second lower affinity isoform of MMP9. We also theoretically characterize the MMP3/TIMP2/pro-MMP9 and MMP3/TIMP1/pro-MMP9 systems. We speculate that these systems differ significantly in their time scales of activation and inhibition such that MMP9 is able to temporarily overshoot its final equilibrium value in the latter. Our numerical simulations suggest that the ability of pro-MMP9 to complex TIMP1 increases this overshoot. In all, our analysis serves as a summary of existing kinetic data for MMP9 and a foundation for future models utilizing MMP9 or other MMPs under physiologically well defined microenvironments.

Myeloperoxidase inactivates TIMP-1 by oxidizing its N-terminal cysteine residue: an oxidative mechanism for regulating proteolysis during inflammation

An imbalance between the proteolytic activity of matrix metalloproteinases (MMPs) and the activity of tissue inhibitors of metalloproteinases (TIMPs) is implicated in tissue injury during inflammation. The N-terminal cysteine of TIMP-1 plays a key role in the inhibitory activity of the protein because it coordinates the essential catalytic Zn2+ of the MMP, preventing the metal ion from functioning. An important mechanism for controlling the interaction of TIMPs with MMPs might involve hypochlorous acid (HOCl), a potent oxidant produced by the myeloperoxidase (MPO) system of phagocytes. Here, we show that HOCl generated by the MPO-H2O2-chloride system inactivates TIMP-1 by oxidizing its N-terminal cysteine. The product is a novel 2-oxo acid. Liquid chromatography-mass spectrometry and tandem mass spectrometry analyses demonstrated that methionine and N-terminal cysteine residues were rapidly oxidized by MPO-derived HOCl but only oxidation of the N-terminal cysteine of TIMP-1 correlated well with loss of inhibitory activity. Importantly, we detected the signature 2-oxo-acid N-terminal peptide in tryptic digests of bronchoalveolar lavage fluid from patients with acute respiratory distress syndrome, demonstrating that TIMP-1 oxidation occurs in vivo. Loss of the N-terminal amino group and disulfide structure are crucial for preventing TIMP-1 from inhibiting MMPs. Our findings suggest that pericellular production of HOCl by phagocytes is a pathogenic mechanism for impairing TIMP-1 activity during inflammation.

Constraining specificity in the N-domain of tissue inhibitor of metalloproteinases-1; gelatinase-selective inhibitors

The tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of the matrix metalloproteinases (MMPs). Since unregulated MMP activities are linked to arthritis, cancer, and atherosclerosis, TIMP variants that are selective inhibitors of disease-related MMPs have potential therapeutic value. The structures of TIMP/MMP complexes reveal that most interactions with the MMP involve the N-terminal pentapeptide of TIMP and the C-D beta-strand connector which occupy the primed and unprimed regions of the active site. The loop between beta-strands A and B forms a secondary interaction site for some MMPs, ranging from multiple contacts in the TIMP-2/membrane type-1 (MT1)-MMP complex to none in the TIMP-1/MMP-1 complex. TIMP-1 and its inhibitory domain, N-TIMP-1, are weak inhibitors of MT1-MMP; inhibition is not improved by grafting the longer AB loop from TIMP-2 into N-TIMP-1, but this change impairs binding to MMP-3 and MMP-7. Mutational studies with N-TIMP-1 suggest that its weak inhibition of MT1-MMP, as compared to other N-TIMPs, arises from multiple (>3) sequence differences in the interaction site. Substitutions for Thr2 of N-TIMP-1 strongly influence MMP selectivity; Arg and Gly, that generally reduce MMP affinity, have less effect on binding to MMP-9. When the Arg mutation is added to the N-TIMP-1(AB2) mutant, it produces a gelatinase-specific inhibitor with Ki values of 2.8 and 0.4 nM for MMP-2 and -9, respectively. Interestingly, the Gly mutant has a Ki of 2.1 nM for MMP-9 and >40 muM for MMP-2, indicating that engineered TIMPs can discriminate between MMPs in the same subfamily.

Identification of the Extracellular Matrix (ECM) Binding Motifs of Tissue Inhibitor of Metalloproteinases (TIMP)-3 and Effective Transfer to TIMP-1

Tissue inhibitor of metalloproteinases (TIMPs) are the endogenous inhibitors of the zinc-dependent endopeptidases of the matrix metalloproteinase families. There are four mammalian TIMPs (TIMP-1 to -4) but only TIMP-3 is sequestered to the extracellular matrix (ECM). The molecular basis for the TIMP-3:ECM association has never been fully investigated until now. In this report, we identify the unique amino acid configuration that constitutes the basis of the ECM binding motif in TIMP-3. By systematically exchanging the subdomains of the TIMPs and exhaustive mutation of TIMP-3, we have identified the surface residues directly responsible for ECM association. Contrary to the accepted view, we have found that TIMP-3 interacts with the ECM via both its N- and C-terminal domains. The amino acids involved in ECM binding are all basic in nature: Lys-26, Lys-27, Lys-30, Lys-76 of the N-terminal domain and Arg-163, Lys-165 of the C-terminal domain. Replacement of these residues with glutamate (E) and glutamine (Q) (K26/27/30/76E + R163/K165Q) resulted in a soluble TIMP-3 devoid of ECM-adhering ability. Using the ECM binding motif derived from TIMP-3, we have also created a TIMP-1 mutant (K26/27/30 + K76 transplant) capable of ECM association. This is the first instance of TIMPs being intentionally rendered soluble or ECM-bound. The ability to prepare TIMPs in soluble or ECM-bound forms also opens new avenues for future TIMP research.

Rapid and individual-specific glycoprofiling of the low abundance N-glycosylated protein tissue inhibitor of metalloproteinases-1

A gel-based method for a mass spectrometric site-specific glycoanalysis was developed using a recombinant glycoprotein expressed in two different cell lines. Hydrophilic interaction liquid chromatography at nanoscale level was used to enrich for glycopeptides prior to MS. The glycoprofiling was performed using matrix-assisted laser desorption/ionization MS and MS/MS. The method proved to be fast and sensitive and furthermore yielded a comprehensive site-specific glycan analysis, allowing a differentiation of the glycoprofiles of the two sources of recombinant protein, both comprising N-glycans of a highly heterogeneous nature. To test the potential of the method, tissue inhibitor of metalloproteinases-1 (TIMP-1), a secreted low abundance N-glycosylated protein and a cancer marker, was purified in an individual-specific manner from plasma of five healthy individuals using IgG depletion and immunoaffinity chromatography. The corresponding TIMP-1 glycoprofiles were determined to be highly similar, comprising mainly bi- and triantennary complex oligosaccharides. Additionally it was shown that platelet-derived TIMP-1 displayed a similar glycoprofile. This is the first study to investigate the glycosylation of naturally occurring human TIMP-1, and the high similarity of the glycoprofiles showed that individual-specific glycosylation variations of TIMP-1 are minimal. In addition, the results showed that TIMP-1 derived from platelets and plasma is similarly glycosylated. This comprehensive and rapid glycoprofiling of a low abundance glycoprotein performed in an individual-specific manner allows for future studies of glycosylated biomarkers for person-specific detection of altered glycosylation and may thus allow early detection and monitoring of diseases.

Crystal structure of the catalytic domain of matrix metalloproteinase-1 in complex with the inhibitory domain of tissue inhibitor of metalloproteinase-1

The mammalian collagenases are a subgroup of the matrix metalloproteinases (MMPs) that are uniquely able to cleave triple helical fibrillar collagens. Collagen breakdown is an essential part of extracellular matrix turnover in key physiological processes including morphogenesis and wound healing; however, unregulated collagenolysis is linked to important diseases such as arthritis and cancer. The tissue inhibitors of metalloproteinases (TIMPs) function in controlling the activity of MMPs, including collagenases. We report here the structure of a complex of the catalytic domain of fibroblast collagenase (MMP-1) with the N-terminal inhibitory domain of human TIMP-1 (N-TIMP-1) at 2.54 A resolution. Comparison with the previously reported structure of the TIMP-1/stromelysin-1 (MMP-3) complex shows that the mechanisms of inhibition of both MMPs are generally similar, yet there are significant differences in the protein-protein interfaces in the two complexes. Specifically, the loop between beta-strands A and B of TIMP-1 makes contact with MMP-3 but not with MMP-1, and there are marked differences in the roles of individual residues in the C-D connector of TIMP-1 in binding to the two MMPs. Structural rearrangements in the bound MMPs are also strikingly different. This is the first crystallographic structure that contains the truncated N-terminal domain of a TIMP, which shows only minor differences from the corresponding region of the full-length protein. Differences in the interactions in the two TIMP-1 complexes provide a structural explanation for the results of previous mutational studies and a basis for designing new N-TIMP-1 variants with restricted specificity.

Inhibition of hepatic fibrogenesis by matrix metalloproteinase‐9 mutants in mice

Tissue inhibitor of metalloproteinases-1 (TIMP-1) plays a crucial role in the pathogenesis of hepatic fibrosis and thus may represent an important therapeutic target in the design of anti-fibrotic strategies for chronic liver disease. We present an innovative therapy based on the assignment of inactivated enzymes acting as scavengers for TIMP-1. Hepatic fibrosis was induced in BALB/c mice by repetitive intraperitoneal CCl4 injection. The animals were treated with proteolytic inactive matrix metalloproteinase-9 mutants (E402Q, H401A, E402H/H411E) using adenovirus-mediated gene transfer. Application of these MMP-9 mutants inhibited fibrogenesis, which was indicated by decreasing portal and periportal accumulation of collagen. Total hydroxyproline of liver tissue, the morphometric stage of fibrosis as well as mRNA expression of marker proteins for hepatic fibrosis in livers of E402Q- and H401A-treated mice were significantly reduced. MMP-9 mutants suppressed transdifferentiation of hepatic stellate cells to the myofibroblast like phenotype in vitro and in vivo. Moreover, adenoviral application of the mutants MMP-9-H401A and -E402Q led to increased apoptosis of activated hepatic stellate cells, thought to be the main promoters of hepatic fibrosis. Application of MMP-9 mutants as TIMP-1 scavengers may provide a new therapeutic strategy for hepatic fibrosis.

Plasma storage at -80 degrees C does not protect matrix metalloproteinase-9 from degradation

Recently, matrix metalloproteinase-9 (MMP-9) has been identified as a cardiovascular risk marker and is increasingly being determined in clinical studies. Among other matrix metalloproteinases, MMP-9 is known to be self-activable, as the cleavage of the propeptide leads to the formation of an active enzyme. In such a case the issue of storage of biological samples such as plasmas is of outstanding importance, as an enzymatic activity, although minimal, may remain at common storage temperature, i.e., -80 degrees C. Since 2000 our institute has created a plasma library from patients presenting with acute myocardial infarction. Recently, the evaluation of the MMP-9 led to the surprise of finding a dramatically low level of detectable enzyme in the oldest plasma samples. By using zymography, enzyme-linked immunosorbent assay and Western blots, we evaluated new and old samples and found that MMP-9 degrades over time. After 2 years, the detectable total MMP-9 dropped by 65%, and the asymptotic profile of the curve reached a residual 1% level after 43 months. These results were confirmed by zymography and western blotting. TIMP-1, the natural inhibitor of MMP-9 and MMP-2, remained rather stable over time. The results suggest that human plasma MMP-9 levels should be determined as soon as possible after sampling.

Photoaptamer arrays applied to multiplexed proteomic analysis

Multiplexed photoaptamer-based arrays that allow for the simultaneous measurement of multiple proteins of interest in serum samples are described. Since photoaptamers covalently bind to their target analytes before fluorescent signal detection, the arrays can be vigorously washed to remove background proteins, providing the potential for superior signal-to-noise ratios and lower limits of quantification in biological matrices. Data are presented here for a 17-plex photoaptamer array exhibiting limits of detection below 10 fM for several analytes including interleukin-16, vascular endothelial growth factor, and endostatin and able to measure proteins in 10% serum samples. The assays are simple, scalable, and reproducible. Affinity of the capture reagent is shown to be directly correlated to the limit of detection for the analyte on the array.

Serum levels of matrix metalloproteinases MMP-2 and MMP-9 and their tissue natural inhibitors in breast tumors

In this study, the levels of matrix metalloproteinases MMP-2 and MMP-9 were simultaneously analyzed with the levels of their tissue natural inhibitors TIMP-1 and TIMP-2 in sera of patients with breast tumors. At the same time, the activity of these two matrix metalloproteinases was evaluated. The decrease of TIMP-2 level in sera from patients with breast cancer as well as an imbalance between MMP-2 and TIMP-2 in neoplasic processes were found. The serum levels of MMP-2, MMP-9 and TIMP-1 were comparable between the patients with breast cancer and benign tumors. These experimental studied parameters were found to correlate with some of clinicopathological disease variables (TNM or pTNM staging system, tumor size and node invasion) suggesting their potential value for diagnosis and prognosis of breast cancer. Matrix metalloproteinases or their natural inhibitors and tumor markers (CA15.3 and CEA) not correlated between but, each of them correlated with another clinicopathological disease variable, suggesting their usefulness in the evaluation.

Threonine 98, the pivotal residue of tissue inhibitor of metalloproteinases (TIMP)-1 in metalloproteinase recognition

Tissue inhibitors of metalloproteinases (TIMPs) are the endogenous modulators of the zinc-dependent mammalian matrix metalloproteinases (MMPs) and their close associates, proteinases of the ADAM (a disintegrin and metalloproteinase) and ADAM with thrombospondin repeats families. There are four variants of TIMPs, and each has its defined set of metalloproteinase (MP) targets. TIMP-1, in particular, is inactive against several of the membrane-type MMPs (MT-MMPs), MMP-19, and the ADAM proteinase TACE (tumor necrosis factor-alpha-converting enzyme, ADAM-17). The molecular basis for such inactivity is unknown. Previously, we showed that TIMP-1 could be transformed into an active inhibitor against MT1-MMP by the replacement of threonine 98 residue with leucine (T98L). Here, we reveal that the T98L mutation has in fact transformed TIMP-1 into a versatile inhibitor against an array of MPs otherwise insensitive to wild-type TIMP-1; examples include TACE, MMP-19, and MT5-MMP. Using T98L as the scaffold, we created a TIMP-1 variant that is fully active against TACE. The binding affinity of the mutant (V4S/TIMP-3-AB-loop/V69L/T98L) (K (app)(i) 0.14 nm) surpassed that of TIMP-3 (K (app)(i) 0.22 nm), the only natural TIMP inhibitor of the enzyme. The requirement for leucine is absolute for the transformation in inhibitory pattern. On the other hand, the mutation has minimal impact on the MPs already well inhibited by wild-type TIMP-1, such as gelatinase-A and stromelysin-1. Not only have we unlocked the molecular basis for the inactivity of TIMP-1 against several of the MPs, but also our findings fundamentally modify the current beliefs on the molecular mechanism of TIMP-MP recognition and selectivity.

Identification, purification and partial characterization of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in bovine pulmonary artery smooth muscle

Bovine pulmonary artery smooth muscle tissue possesses the tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) as revealed by immunoblot studies of the cytosolic fraction with polyclonal TIMP-1 antibody. In this report, we described the purification and partial characterization of the inhibitor from the cytosolic fraction of the smooth muscle. This inhibitor was purified by a series of anion-exchange, gel filtration and affinity chromatographic procedure. The purified inhibitor showed an apparent molecular mass of 30 kDa in SDS-PAGE. Amino terminal sequence analysis for the first 22 amino acids of the purified inhibitor was also found to be identical to bovine TIMP-1. This glycosylated inhibitor was found to be active against matrix metalloproteinase-9 (MMP-9, gelatinase B), the ambient matrix metalloproteinase in the pulmonary smooth muscle. The purified TIMP-1 was also found to be sensitive to pure rabbit and human fibroblast collagenase and type IV collagenase. In contrast, it had minimum inhibitory activity against bacterial collagenase. It was also found to be inactive against the serine proteases trypsin and plasmin. The inhibitor was heat and acid resistant and it had the sensitivity to trypsin degradation and reduction-alkylation.

Unveiling the surface epitopes that render tissue inhibitor of metalloproteinase-1 inactive against membrane type 1-matrix metalloproteinase

Membrane type 1-matrix metalloproteinase (MT1-MMP) is a zinc-dependent, membrane-associated endoproteinase of the metzincin family. The enzyme regulates extracellular matrix remodeling and is capable of cleaving a wide variety of transmembrane proteins. The enzymatic activity of MT1-MMP is regulated by endogenous inhibitors, the tissue inhibitor of metalloproteinases (TIMP). To date, four variants of mammalian TIMP have been identified. Whereas TIMP-2-4 are potent inhibitors against MT1-MMP, TIMP-1 displays negligible inhibitory activity against the enzyme. The rationale for such selectivity is hitherto unknown. Here we identify the surface epitopes that render TIMP-1 inactive against MT1-MMP. We show that TIMP-1 can be transformed into an active inhibitor against MT1-MMP by the mutation of a single residue, namely threonine 98 to leucine (T98L). The resultant mutant displayed inhibitory characteristics of a typical slow, tight binding inhibitor. The potency of the mutant could be further enhanced by the introduction of valine 4 to alanine (V4A) and proline 6 to valine (P6V) mutations. Indeed, the inhibitory profile of the triple mutant (V4A/P6V/T98L) is indistinguishable from those of other TIMPs. Our findings suggest that threonine 98 is critical in initiating MMP binding and complex stabilization. Our findings also provide a potential mechanistic explanation for MMP-TIMP selectivity.

Global orientation of bound MMP-3 and N-TIMP-1 in solution via residual dipolar couplings

Crystal structures of catalytic domains of MMP-3 and MT1-MMP bound to TIMP-1 or TIMP-2, respectively, differ in the orientation of the TIMP in the MMP active site. The orientation in solution of N-TIMP-1 in the MMP-3 active site has been investigated using residual dipolar couplings (RDCs). Fitting of the RDCs to the X-ray structures of the complexes suggests general agreement with the orientation of crystalline MMP-3(DeltaC) and TIMP-1 and a large disparity from the orientation of crystalline MT1-MMP(DeltaC) and TIMP-2. Rigid body docking of MMP-3 and N-TIMP-1 X-ray coordinates using RDCs and intermolecular NOEs provided a time-averaged orientation in solution differing from the crystal structure by a 5 degrees rotation toward the MT1-MMP(DeltaC)/TIMP-2 orientation. The slight discrepancy in orientations in solution and crystal lies within the experimental uncertainties. Intermolecular NOEs used in the docking corroborated the accuracy of mapping the interface by a paramagnetic NMR footprinting assay, a potential alternative source of contacts for docking. Some uncertainty in the N-TIMP-1 orientation in the MMP-3 active site, coupled with microsecond to millisecond fluctuations of the MMP-binding ridge of N-TIMP-1 in the complex and flexibility in MMP-3(DeltaC) S(1)' to S(3)' subsites, leaves open the possibility that N-TIMP-1 might dynamically pivot a few degrees or more in the arc toward the MT1-MMP(DeltaC)/TIMP-2 orientation. Differing TIMP orientations in MMP active sites are more likely to result from structural differences in TIMP AB hairpin loops than from crystal packing artifacts.

Synthesis of the C-terminal domain of the tissue inhibitor of metalloproteinases-1 (TIMP-1)

According to recent investigations, the C-terminal domain of the tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) is responsible for some biological effects that are independent of the enzyme-inhibiting effect of the N-terminal domain of the molecule. The C-terminal domain has been prepared for structure-biological activity investigations. After the chemical synthesis and the folding of the linear peptide. LC-MS and MALDI-MS analysis revealed that two isomers with different disulphide bond arrangements were formed. Since more than 30 folding experiments resulted in products with a very similar HPLC-profile, it was concluded that in the absence of the TIMP-1 N-terminal domain no entirely correct folding of the C-terminal domain occurred. Furthermore, it was observed that, in spite of several purification steps, mercury(II) ions were bound to the 6SH-linear peptide; it was demonstrated--using disulphide bonded TIMP-1(Cys145-Cys166) as a model--that mercury(II) ions can cause peptide degradation at pH 7.8 as well as in 0.1% trifluoroacetic acid.

Increased backbone mobility in beta-barrel enhances entropy gain driving binding of N-TIMP-1 to MMP-3

The high-affinity inhibition of stromelysin 1 (MMP-3) by tissue inhibitor of metalloproteinases 1 (TIMP-1) helps control tissue remodeling and tumor development. The interaction of N-TIMP-1 with the catalytic domain of MMP-3 has been investigated by titration calorimetry and 15N NMR. Their unfavorable enthalpy of binding of +6.5 kcal mol(-1) is unusual among protein-protein associations, deviates from structure-based prediction, and is compensated by a net entropy increase providing at least 18 kcal mol(-1) of favorable free energy of binding at a 1M reference state. The small heat capacity of binding agrees well with the heat capacity predicted from 65% of the surface buried on binding being polar, and suggests that the hydrophobic effect can account for only part of the entropy of binding. Using NMR, binding-induced changes in the backbone of N-TIMP-1 were checked as one possible source of conformational entropy changes. MMP binding slightly increases rigidity in some contact sites in TIMP-1 but increases mobility remotely in the otherwise rigid beta-barrel core of N-TIMP-1, increasing 15N relaxation evidence of pico- to nanosecond and micro- to millisecond fluctuations of beta-strands A-F. Residual dipolar couplings suggest dynamic deviations from X-ray coordinates of the complex. These suggest that the beta-barrel has small backbone conformational fluctuations, while segments of strands betaB, betaE and betaF might experience fluctuations only in their backbone environment. This is a distinctive example of affinity between two well-structured proteins being enhanced by increased conformational entropy in the reservoir of a folding core.

Protein engineering of the tissue inhibitor of metalloproteinase 1 (TIMP-1) inhibitory domain. In search of selective matrix metalloproteinase inhibitors

Studies of the structural basis of the interactions of tissue inhibitors of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs) may provide clues for designing MMP-specific inhibitors. In this paper we report combinations of mutations in the major MMP-binding region that enhance the specificity of N-TIMP-1. Mutants with substitutions for residues 4 and 68 were characterized and combined with previously studied Thr(2) mutations to generate mutants with improved selectivity or binding affinity to specific MMPs. Some combinations of mutations had non-additive effects on DeltaG of binding to MMPs, suggesting interactions between subsites in the reactive site. The T2L/V4S mutation generates an inhibitor that binds to MMP-2 20-fold more tightly than to MMP-3(DeltaC) and over 400-fold more tightly than to MMP-1. The T2S/V4A/S68Y mutant is the strongest inhibitor for stromelysin-1 among all mutants characterized to date, with an apparent K(i) for MMP-3(DeltaC) in the picomolar range. A third mutant, T2R/V4I, has no detectable inhibitory activity for MMP-1 but is an effective inhibitor of MMP-2 and -3. These selective TIMP variants may provide useful tools for investigation of biological roles of specific MMPs and for possible therapy of MMP-related diseases.

Structural basis of the adaptive molecular recognition by MMP9

Matrix metalloproteinase (MMPs) are critical for the degradation of extracellular matrix components and, therefore, need to be regulated tightly. Almost all MMPs share a homologous C-terminal haemopexin-like domain (PEX). Besides its role in macromolecular substrate processing, the PEX domains appear to play a major role in regulating MMP activation, localisation and inhibition. One intriguing property of MMP9 is its competence to bind different proteins, involved in these regulatory processes, with high affinity at an overlapping recognition site on its PEX domain. With the crystal structure of the PEX9 dimer, we present the first example of how PEX domains accomplish these diverse roles. Blade IV of PEX9 mediates the non-covalent and predominantly hydrophobic dimerisation contact. Large shifts of blade III and, in particular, blade IV, accompany the dimerisation, resulting in a remarkably asymmetric homodimeric structure. The asymmetry provides a novel mechanism of adaptive protein recognition, where different proteins (PEX9, PEX1, and TIMP1) can bind with high affinity to PEX9 at an overlapping site. Finally, the structure illustrates how the dimerisation generates new properties on both a physico-chemical and functional level.

Expression of matrix metalloproteinase (MMP-1) and tissue inhibitor of MMP in serosal tissue of intraperitoneal organs and adhesions

OBJECTIVE

To compare expression of matrix metalloproteinase (MMP-1) and tissue inhibitor of MMP (TIMP-1) in serosal tissue of intraperitoneal organs and adhesions.

DESIGN

Prospective and cross-sectional study.

SETTING

Academic research centers.

PATIENT(S)

Patients undergoing abdominal or pelvic surgery.

INTERVENTION(S)

MMP-1 and TIMP-1 expression.

MAIN OUTCOME MEASURE(S)

Expression of messenger ribonucleic acid (mRNA) and protein was measured by using quantitative reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay.

RESULT(S)

Serosal tissue of intraperitoneal organs and adhesions express MMP-1 and TIMP-1 mRNA and protein at levels that are consistently varied with 10- to 10,000-fold and 2- to 10-fold higher TIMP, mRNA and protein, respectively. Parietal peritoneum, fallopian tubes and ovaries express higher MMP-1 mRNA levels compared with uterus and adhesions; the lowest expression is found in small and large bowels, subcutaneous tissue. and omentum. Expression of TIMP-1 mRNA was less variable; the highest level was found in the uterus and the lowest in subcutaneous tissue and small bowels. There was less variability in MMP-1 and TIMP-1 protein content than mRNA expression; ovaries and adhesions contained the highest MMP-1 and TIMP-1 levels, respectively, and peritoneum contained the lowest. The MMP-1 and TIMP-1 content and ratios further indicate limited MMP-1 proteolytic activity. Although tissues from premenopausal women express more MMP-1 and TIMP-1, expression did not differ by sex or age.

CONCLUSION(S)

Because MMP-1 and TIMP-1 expression varies consistently among the serosal tissues of peritoneal organs and adhesions, and because tissue injury alters their expression, site-specific variations in expression of these substances may predispose a particular organ to develop more adhesions.

The laminin-binding domain of agrin is structurally related to N-TIMP-1

Agrin is the key organizer of postsynaptic differentiation at the neuromuscular junction. This organization activity requires the binding of agrin to the synaptic basal lamina. Binding is conferred by the N-terminal agrin (NtA) domain, which mediates a high-affinity interaction with the coiled coil domain of laminins. Here, we report the crystal structure of chicken NtA at 1.6 A resolution. The structure reveals that NtA harbors an oligosaccharide/oligonucleotide-binding fold with several possible sites for the interaction with different ligands. A high structural similarity of NtA with the protease inhibition domain in tissue inhibitor of metalloproteinases-1 (TIMP-1) supports the idea of additional functions of agrin besides synaptogenic activity.

Metabolic control of recombinant protein N-glycan processing in NS0 and CHO cells

Chinese hamster ovary and murine myeloma NS0 cells are currently favored host cell types for the production of therapeutic recombinant proteins. In this study, we compared N-glycan processing in GS-NS0 and GS-CHO cells producing the same model recombinant glycoprotein, tissue inhibitor of metalloproteinases 1. By manipulation of intracellular nucleotide-sugar content, we examined the feasibility of implementing metabolic control strategies aimed at reducing the occurrence of murine-specific glycan motifs on NS0-derived recombinant proteins, such as Galalpha1,3Galbeta1,4GlcNAc. Although both CHO and NS0-derived oligosaccharides were predominantly of the standard complex type with variable sialylation, 30% of N-glycan antennae associated with NS0-derived TIMP-1 terminated in alpha1,3-linked galactose residues. Furthermore, NS0 cells conferred a greater proportion of terminal N-glycolylneuraminic (sialic) acid residues as compared with the N-acetylneuraminic acid variant. Inclusion of the nucleotide-sugar precursors, glucosamine (10 mM, plus 2 mM uridine) and N-acetylmannosamine (20 mM), in culture media were shown to significantly increase the intracellular pools of UDP-N-acetylhexosamine and CMP-sialic acid, respectively, in both NS0 and CHO cells. The elevated UDP-N-acetylhexosamine content induced by the glucosamine/uridine treatment was associated with an increase in the antennarity of N-glycans associated with TIMP-1 produced in CHO cells but not N-glycans associated with TIMP-1 from NS0 cells. In addition, elevated UDP-N-acetylhexosamine content was associated with a slight decrease in sialylation in both cell lines. The elevated CMP-sialic acid content induced by N-acetylmannosamine had no effect on the overall level of sialylation of TIMP-1 produced by both CHO and NS0 cells, although the ratio of N-glycolylneuraminic acid:N-acetylneuraminic acid associated with NS0-derived TIMP-1 changed from 1:1 to 1:2. These data suggest that manipulation of nucleotide-sugar metabolism can promote changes in N-glycan processing that are either conserved between NS0 and CHO cells or specific to either NS0 cells or CHO cells.

TIMP-3 is a potent inhibitor of aggrecanase 1 (ADAM-TS4) and aggrecanase 2 (ADAM-TS5)

The proteoglycan aggrecan is an important major component of cartilage matrix that gives articular cartilage the ability to withstand compression. Increased breakdown of aggrecan is associated with the development of arthritis and is considered to be catalyzed by aggrecanases, members of the ADAM-TS family of metalloproteinases. Four endogenous tissue inhibitors of metalloproteinases (TIMPs) regulate the activities of functional matrix metalloproteinases (MMPs), enzymes that degrade most components of connective tissue, but no endogenous factors responsible for the regulation of aggrecanases have been found. We show here that the N-terminal inhibitory domain of TIMP-3, a member of the TIMP family that has functional properties distinct from other TIMPs, is a strong inhibitor of human aggrecanases 1 and 2, with K(i) values in the subnanomolar range. This truncated inhibitor, which lacks the C-terminal domain that is responsible for interactions with molecules other than active metalloproteinases, is produced at high yield by bacterial expression and folding from inclusion bodies. This provides a starting point for developing a biologically available aggrecanase inhibitor suitable for the treatment of arthritis.

Tissue inhibitor of metalloproteinases-1 undergoes microsecond to millisecond motions at sites of matrix metalloproteinase-induced fit

The N-terminal, matrix metalloproteinase (MMP)-inhibitory fragment of recombinant, human tissue inhibitor of metalloproteinases (TIMP-1) exhibits varied backbone dynamics and rigidity. Most striking is the presence of chemical exchange in the MMP-binding ridge reported to undergo conformational change upon MMP binding. Conformational exchange fluctuations in microseconds to milliseconds map to the sites of MMP-induced fit at residues Val29 through Leu34 of the AB loop and to the Ala65 and Cys70 "hinges" of the CD loop of TIMP-1. Slow chemical exchange is also present at the type I turn of the EF loop at the base of the MMP-binding ridge. These functional slow motions and other fast internal motions are evident from backbone (15)N spin relaxation at 500 and 750 MHz, whether interpreted by the model-free formalism with axial diffusion anisotropy or by the reduced spectral density approach. The conformational exchange is confirmed by its deviation from the trend between R(2) and the cross-correlation rate eta. The magnetic field-dependence indicates that the chemical exchange broadening in the AB and CD loops is fast on the time-scale of chemical shift differences. The conformational exchange rates for most of these exchanging residues, which can closely approach MMP, appear to be a few thousand to several thousand per second. The slow dynamics of the TIMP-1 AB loop contrast the picosecond to nanosecond dynamics reported in the longer TIMP-2 AB loop.

Expression, characterization and structure determination of an active site mutant (Glu202-Gln) of mini-stromelysin-1

Human stromelysin-1 is a member of the matrix metalloproteinase (MMP) family of enzymes. The active site glutamic acid of the MMPs is conserved throughout the family and plays a pivotal role in the catalytic mechanism. The structural and functional consequences of a glutamate to glutamine substitution in the active site of stromelysin-1 were investigated in this study. In contrast to the wild-type enzyme, the glutamine-substituted mutant was not active in a zymogram assay where gelatin was the substrate, was not activated by organomercurials and showed no activity against a peptide substrate. The glutamine-substituted mutant did, however, bind to TIMP-1, the tissue inhibitor of metalloproteinases, after cleavage of the propeptide with trypsin. A second construct containing the glutamine substitution but lacking the propeptide was also inactive in the proteolysis assays and capable of TIMP-1 binding. X-ray structures of the wild-type and mutant proteins complexed with the propeptide-based inhibitor Ro-26-2812 were solved and in both structures the inhibitor binds in an orientation the reverse of that of the propeptide in the pro-form of the enzyme. The inhibitor makes no specific interactions with the active site glutamate and a comparison of the wild-type and mutant structures revealed no major structural changes resulting from the glutamate to glutamine substitution.

NMR structure of tissue inhibitor of metalloproteinases-1 implicates localized induced fit in recognition of matrix metalloproteinases

A high quality solution structure of the matrix metalloproteinase inhibitory N-terminal domain of recombinant human tissue inhibitor of metalloproteinases-1 (N-TIMP-1) has been determined. For the rigidly packed residues, the average RMSD to the mean structure is 0. 57 A for the backbone atoms and 1.00 A for all heavy atoms. Comparison of the solution structure of free N-TIMP-1 with the crystal structure of TIMP-1 bound to the catalytic domain of MMP-3 ( Gomis-R]uth et al., 1997 ) shows that the structural core of the beta barrel flanked by helices is nearly unchanged by the association with MMP-3, evident from a backbone RMSD of 1.15 A. However, clear differences in the conformation of the MMP-binding ridge of free and MMP-bound TIMP-1 suggest induced fit throughout the ridge. The MMP-dependent conformational changes in the ridge include a dramatic bending of AB loop residues Glu28 through Leu34, moderate hinge bending of the CD-loop about residues Ala65 and Cys70, and modest bending of the Cys1 through Pro6 segment. A large number of interresidue Nuclear Overhauser enhancements (NOEs) augmented by stereospecific assignments, torsion restraints, and dipolar couplings (an average of 18 non-trivial restraints per residue) engender confidence in these structural inferences. A tight cluster of three lysine residues and one arginine residue atop beta-strands A and B, and identical among TIMP sequences, form the heart of a highly conserved electropositive patch that may interact with anionic components of the extracellular matrix.

Ca(2+) and Zn(2+) binding properties of peptide substrates of vertebrate collagenase, MMP-1

To understand the role of Ca(2+) in vertebrate in the structure and action of collagenase, we have examined peptides that interact with recombinant human fibroblast collagenase for their affinities towards Ca(2+) and Zn(2+) in a non-polar solvent. Two of the peptides, GPQGIAGQ and GNVGLAGA, had sequences in collagen which are, respectively, cleaved and not cleaved by collagenase. A third peptide, PSYFLNAG, had a collagenase-cleaved sequence in ovostatin, a globular protein substrate. Peptides TVGCEECTV and CLPREPGL were derived from TIMP-1; the former competitively inhibits collagenase while the latter does not. The relative rates of hydrolysis of the peptides by collagenase had the order GPQGIAGQ>PSYFLNAG>GNVGLAGA. Circular dichroism spectral data in trifluoroethanol showed that while the TIMP control peptide, CLPREPGL, bound only Zn(2+), the other four peptides bound both Ca(2+) and Zn(2+) with definite stoichiometries. Ca(2+) could displace Zn(2+) in the substrate peptides while Zn(2+) displaced Ca(2+) in the TIMP peptide. GPQGIAGQ, PSYFLNAG and TVGCEECTV formed peptide:Ca(2+):Zn(2+) ternary complexes. Our results suggest that both collagen and globular protein substrates of collagenase may bind Ca(2+) and Zn(2+) in the enzyme's active site. This, in turn, may account for the known importance of the non-catalytic Ca(2+) and Zn(2+) in collagenase activity.

Engineering of selective TIMPs

Differences in proteinase susceptibility between free TIMP-1 and the TIMP-1-MMP-3 complex and mutagenesis studies suggested that the residues around the disulfide bond between Cys1 and Cys70 in TIMP-1 may interact with MMPs. The crystal structure of the complex between TIMP-1 and the catalytic domain of MMP-3 has revealed that the alpha-amino group of Cys1 bidentately chelates the catalytic zinc of MMP-3 and the Thr2 side chain occupies the S1' pocket. Generation of the N-terminal domain of TIMP-1 (N-TIMP-1) variants with 15 different amino acid substitutions for Thr2 has indicated that the nature of the side chain of residue 2 has a major effect on the affinity of N-TIMP-1 for three different MMPs (MMPs-1, -2 and -3). The results also demonstrate that the mode of binding of N-TIMP-1 residue 2 differs from the binding of the P1' residue of a peptide substrate.

Insights into MMP-TIMP interactions

The proteolytic activity of the matrix metalloproteinases (MMPs) involved in extracellular matrix degradation must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance can result in serious diseases such as arthritis and tumor growth and metastasis. Knowledge of the tertiary structures of the proteins involved in such processes is crucial for understanding their functional properties and to interfere with associated dysfunctions. Within the last few years, several three-dimensional structures have been determined showing the domain organization, the polypeptide fold, and the main specificity determinants of the MMPs. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure-based design and improvement of high-affinity ligands, which might be elaborated into drugs. Very recently, structural information also became available for some TIMP structures and MMP-TIMP complexes, and these new data elucidated important structural features that govern the enzyme-inhibitor interaction.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) binds to the cell surface and translocates to the nucleus of human MCF-7 breast carcinoma cells

To study cellular and subcellular localization of TIMP-1, we constructed a cDNA which would express a chimeric protein, TIMP-1-EGFP, having the enhanced green fluorescent protein of the jelly fish Aequorea victoria fused to the carboxyl-terminus of TIMP-1. Chinese Hamster Ovary (CHO) cells were stably transfected with the TIMP-1-EGFP expressing plasmid. The secreted chimera was processed through the endoplasmic reticulum and Golgi, as was shown by fluorescent confocal microscopy after incubations at temperatures which block processing at the intermediate compartment and the trans-Golgi network. In a co-culture system, secreted TIMP-1-EGFP could be visualized binding to the surface of MCF-7 breast carcinoma cells but not non-neoplastic HBL-100 breast epithelial cells. TIMP-1-EGFP localized to the nucleus of MCF-7 cells after 72 hrs in co-culture. These findings suggest that TIMP-1 may preferentially bind to and be taken up by malignant breast epithelial cells and that TIMP-1 may play a yet unidentified role in nuclear functions.

Residue 2 of TIMP-1 is a major determinant of affinity and specificity for matrix metalloproteinases but effects of substitutions do not correlate with those of the corresponding P1' residue of substrate

The unregulated activities of matrix metalloproteinases (MMPs) are implicated in disease processes including arthritis and tumor cell invasion and metastasis. MMP activities are controlled by four homologous endogenous protein inhibitors, tissue inhibitors of metalloproteinases (TIMPs), yet different TIMPs show little specificity for individual MMPs. The large interaction interface in the TIMP-1.MMP-3 complex includes a contiguous region of TIMP-1 around the disulfide bond between Cys1 and Cys70 that inserts into the active site of MMP-3. The effects of fifteen different substitutions for threonine 2 of this region reveal that this residue makes a large contribution to the stability of complexes with MMPs and has a dominant influence on the specificity for different MMPs. The size, charge, and hydrophobicity of residue 2 are key factors in the specificity of TIMP. Threonine 2 of TIMP-1 interacts with the S1' specificity pocket of MMP-3, which is a key to substrate specificity, but the structural requirements in TIMP-1 residue 2 for MMP binding differ greatly from those for the corresponding residue of a peptide substrate. These results demonstrate that TIMP variants with substitutions for Thr2 represent suitable starting points for generating more targeted TIMPs for investigation and for intervention in MMP-related diseases.

Endoproteinase-protein inhibitor interactions

Nature uses protein inhibitors as important tools to regulate the proteolytic activity of their target proteinases. Most of these inhibitors for which 3D structures are available are directed towards serine proteinases, interacting with their active-sites in a substrate-like "canonical" manner via an exposed reactive-site loop of conserved conformation. More recently, some non-canonically binding serine proteinase inhibitors, two cysteine proteinase inhibitors, and three zinc endopeptidase inhibitors have been characterized in the free and complexed state, displaying novel mechanisms of inhibition with their target proteinases. These different interaction modes are briefly discussed, with particular emphasis on the interaction between matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors of metalloproteinases (TIMPs).

Molecular characteristics of equine stromelysin and the tissue inhibitor of metalloproteinase 1

OBJECTIVE

To clone the entire coding sequence of equine matrix metalloproteinase-3 (MMP-3, stromelysin) and tissue inhibitor of metalloproteinase-1 (TIMP-1) and compare their nucleotide and amino acid sequences with those of MMP-3 and TIMP-1 from other species.

SAMPLES

Articular cartilage harvested from the joints of 4 foals, 2 yearlings, and 3 adult horses.

PROCEDURE

A cDNA library was constructed from mRNA extracted from equine chondrocytes. The library was screened and clones selected that contained the cDNA for MMP-3 and TIMP-1. The cDNA was sequenced and the nucleotide and deduced amino acid sequences compared with known sequences in other species. Northern blot analysis was performed, using the resulting cDNA clones.

RESULTS

An 1803-bp cDNA for MMP-3 including the entire coding sequence of 1434 bases was cloned and sequenced. A 744-bp cDNA for TIMP-1 including the entire coding sequence of 624 bases was cloned and sequenced. Northern analysis revealed MMP-3 to hybridize to a single mRNA species at approximately 2.1 kb. TIMP-1 hybridized to a single mRNA species at approximately 0.8 kb.

CONCLUSIONS

MMP-3 and TIMP-1 were highly homologous to that of other species at the nucleotide and amino acid level although each had unique residues in part of the peptide that is generally conserved.

CLINICAL RELEVANCE

Understanding the molecular structure of MMP-3 and TIMP-1 and the availability of their cDNA should allow a more detailed understanding of their balance in cartilage and the degradative processes in joint disease.

Preparation of recombinant tissue inhibitor of metalloproteinases-1 (TIMP-1) in high yield and identification of a hydrophobic surface feature

The work presented here describes an effective method for refolding recombinant tissue inhibitor of metalloproteinases-1 (TIMP-1), a 21-kDa protein with six disulphide bonds. A yield of 30 mg TIMP-1/l culture medium was obtained from a high level bacterial expression system, using a slow removal of denaturant in the presence of 0.5 M guanidine and a suitable redox buffer. This protein is identical to the wild-type species when specific activity and secondary structure (by CD) are compared. The fluorescent, hydrophobic compound 8-anilino 1-naphthalene sulphonate (ANS) was used to quantify hydrophobic binding sites on the surface of both wild-type and recombinant TIMP-1. The wild-type protein has 1 binding site with a mean Kd of 1.3 mM and the recombinant protein has 1.5 binding sites with a mean Kd of 0.39 mM. The presence of surface hydrophobic residues is confirmed by selective broadening of ethyl and aromatic signals in the 1H-NMR spectrum on the addition of the paramagnetic probe 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxy, OH-TEMPO, to wild-type TIMP-1. When wild-type TIMP-1 is incubated with the N-terminal fragment of human fibroblast collagenase prior to the addition of ANS, the number of binding sites in the system decreases to 0.5 with a Kd of 0.15 mM.

Equine TIMP-1 and TIMP-2: identification, activity and cellular sources

Matrix metalloproteinases (MMPs) are the main enzymes involved in connective tissue turnover. Regulation of MMPs is achieved by controlling production, activation of the pro-enzymes together with the presence of inhibitors, such as, tissue inhibitors of metalloproteinases (TIMPS). The presence of TIMPs in equine synovial fluid was assessed by the ability of the fluid to inhibit equine MMP-9 activity using a gelatin degradation ELISA. The cellular source of the TIMPs was determined using culture supernatants of resident articular cells (chondrocytes and synovial fibroblasts) and invading inflammatory cells (polymorph neutrophils [PMN] and peripheral blood monocytes [PBM]). The TIMPs were characterised further using reverse zymography, affinity chromatography and N-terminal amino acid sequencing. Synovial fluid was recovered from horses with articular sepsis and aseptic joint disease (AJD) and compared with that from normal horses (n = 4). TIMP activity was minimal in articular sepsis but significantly increased, albeit a small increase, in AJD when compared to normal (P<0.05). Cell culture supernatants from synovial fibroblasts, chondrocytes and PBMs contained TIMP activity, although supernatants from PMN cell culture did not. Reverse zymography of synovial fluid recovered from normal and AJD horses showed two protein bands, 22 and 28 kDa in size, exhibiting inhibitory activity against MMP-9. Reverse zymography of culture supernatants of synovial fibroblasts and chondrocytes gave similar results whereas the culture supernatants from PMNs and PBMs showed the presence of only the 28 kDa protein. The N-terminal amino acid sequence was obtained for the 22 kDa protein and revealed a 66% homology with human TIMP-2. The identification of TIMPs in equine synovial fluids and cell culture supernatants suggest that they may have a fundamental role in the homeostasis of the normal joint and in the excess proteolysis which occurs in articular disease in the horse.

TIMP-1 contact sites and perturbations of stromelysin 1 mapped by NMR and a paramagnetic surface probe

Surfaces of the 173 residue catalytic domain of human matrix metalloproteinase 3 (MMP-3(DeltaC)) affected by binding of the N-terminal, 126 residue inhibitory domain of human TIMP-1 (N-TIMP-1) have been investigated using an amide-directed, NMR-based approach. The interface was mapped by a novel method that compares amide proton line broadening by paramagnetic Gd-EDTA in the presence and absence of the binding partner. The results are consistent with the X-ray model of the complex of MMP-3(DeltaC) with TIMP-1 (Gomis-Rüth et al. (1997) Nature 389, 77-81). Residues Tyr155, Asn162, Val163, Leu164, His166, Ala167, Ala169, and Phe210 of MMP-3(DeltaC) are protected from broadening by the Gd-EDTA probe by binding to N-TIMP-1. N-TIMP-1-induced exposure of backbone amides of Asp238, Asn240, Gly241, and Ser244 of helix C of MMP-3(DeltaC) to Gd-EDTA confirms that the displacement of the N-terminus of MMP-3(DeltaC) occurs not only in the crystal but also in solution. These results validate comparative paramagnetic surface probing as a means of mapping protein-protein interfaces. Novel N-TIMP-1-dependent changes in hydrogen bonding near the active site of MMP-3(DeltaC) are reported. N-TIMP-1 binding causes the amide of Tyr223 of MMP-3(DeltaC) bound by N-TIMP-1 to exchange with water rapidly, implying a lack of the hydrogen bond observed in the crystal structure. The backbone amide proton of Asn162 becomes protected from rapid exchange upon forming a complex with N-TIMP-1 and could form a hydrogen bond to N-TIMP-1. N-TIMP-1 binding dramatically increases the rate of amide hydrogen exchange of Asp177 of the fifth beta strand of MMP-3(DeltaC), disrupting its otherwise stable hydrogen bond.

Presence of an N-terminal polyhistidine tag facilitates stable expression of an otherwise unstable N-terminal domain of mouse tissue inhibitor of metalloproteinase-1 in Escherichia coli

The active N-terminal domain of the mouse tissue inhibitor of metalloproteinases-1 is a 14.1-kDa polypeptide with three disulfide bonds. When expressed using a T7 system in Escherichia coli, this truncated protein, in contrast to the WT protein, was found only in trace amounts in the cell. However, when the coding sequence was placed downstream of a 60-bp sequence that encoded an in-frame histidine-rich "tag," the fusion product (NF.TIMP*His) was expressed in considerably increased abundance. WT.TIMP-1 was expressed in abundance with or without the tag. The mRNAs encoding the various forms of TIMP were present in similar amounts in all four cases. NF.TIMP*His, renatured and purified on a nickel affinity column, was found to be about 10-fold less effective than native human TIMP-2 at inhibiting cleavage of collagen type I by human fibroblast collagenase. A thrombin cleavage site in the tag was susceptible to cleavage by low levels of a contaminating proteinase.

The oxidative inactivation of tissue inhibitor of metalloproteinase-1 (TIMP-1) by hypochlorous acid (HOCI) is suppressed by anti-rheumatic drugs

Tissue inhibitors of metalloproteinases (TIMPs) prevent uncontrolled connective tissue destruction by limiting the activity of matrix metalloproteinases (MMPs). That TIMPs should be susceptible to oxidative inactivation is suggested by their complex tertiary structure which is dependent upon 6 disulphide bonds. We examined the oxidative inactivation of human recombinant TIMP-1 (hr TIMP-1) by HOCl and the inhibition of this process by anti-rheumatic agents. TIMP-1 was exposed to HOCl in the presence of a variety of disease modifying anti-rheumatic drugs. TIMP-1 activity was measured by its ability to inhibit BC1 collagenase activity as measured by a fluorimetric assay using the synthetic peptide substrate (DNP-Pro-Leu-Ala-Leu-Trp-Ala-Arg), best cleaved by MMP-1. The neutrophil derived oxidant HOCl, but not the derived oxidant N-chlorotaurine, can inactivate TIMP-1 at concentrations achieved at sites of inflammation. Anti-rheumatic drugs have the ability to protect hrTIMP-1 from inactivation by HOCl. For D-penicillamine, this effect occurs at plasma levels achieved with patients taking the drug but for other anti-rheumatic drugs tested this occurs at relatively high concentrations that are unlikely to be achieved in vivo, except possibly in a microenvironment. These results are in keeping with the concept that biologically derived oxidants can potentiate tissue damage by inactivating key but susceptible protein inhibitors such as TIMP-1 which form the major local defence against MMP induced tissue breakdown.

Analysis of the conformational stability of the active domain of recombinant mouse TIMP-1 by intrinsic fluorescence

Intrinsic fluorescence was used to examine the stability of an active, N-terminal domain of mouse tissue inhibitor of metalloproteinase (TIMP-1) fused with an N-terminal polyhistidine tag. Emission and quenching studies suggested that the single tryptophan is on the protein surface partially exposed to solvent. The TIMP-1 recombinant unfolded reversibly in the presence of guanidinium chloride with the transition midpoint at 2.35M; extrapolation gave a stabilization free energy of 5.1 kcal mol-1 at 25 degrees C. Analysis of the temperature dependence of the fluorescence intensity gave a melting transition with midpoint at 51 degrees C and an enthalpy and heat capacity change on unfolding of 32 kcal mol-1 and 0.45 kcal K-1 mol-1, respectively, values comparable to other single domain proteins. Comparison with literature data indicated that the stability of mouse recombinant TIMP-1 more closely resembled that of human metalloproteinase inhibitor TIMP-2 than TIMP-1 despite closer homology to the human TIMP-1 protein.