The magnetic resonance imaging and age-adjusted matrix metalloproteinase-7 assist the diagnosis of biliary atresia.

BACKGROUND: We investigated the utilities of the liver-to-psoas apparent diffusion coefficient ratios (LTPAR) yielded by diffusion-weighted magnetic resonance imaging (DWMRI) and the age-adjusted serum matrix metalloproteinase-7 (MMP-7) for the diagnosis of biliary atresia (BA) in cholestatic infants. METHODS: In total, 170 cholestatic infants were recruited, of whom 50 (29.41%) were diagnosed with BA after cholestatic workups. The LTPAR and MMP7 levels were assessed. RESULTS: The LTPAR was significantly lower in BA infants, and the age-adjusted MMP7 ratio was significantly higher, compared to other cholestatic infants (both p < 0.001). Receiver operating characteristic curve analysis yielded a cutoff > 0.1 ng/mL.day for the age-adjusted MMP-7 ratio, and an LTPAR < 1.01 for the optimal prediction of BA (both p < 0.001). Univariate logistic regression analysis revealed that both an age-adjusted MMP-7 ratio > 0.1 ng/mL.day and an LTPAR < 1.01 were significant predictors of BA among cholestatic infants (odds ratio = 30.98 and 13.28; p < 0.001 and < 0.001, respectively). The significance of the age-adjusted MMP-7 ratio and the LTPAR persisted on multivariate logistic regression analysis after adjusting for sex and the serum gamma-glutamyl transferase level (p < 0.001 and < 0.001, respectively). The negative predictive values (NPVs) for BA were 91.49% and 94.17%, respectively, for the LTPAR and age-adjusted MMP-7 ratio. CONCLUSION: The age-adjusted MMP-7 ratio and the LTPAR are both significant non-invasive predictors of BA. The consideration of both serum and imaging parameters may enhance BA diagnostic performance in cholestatic infants.

The Peptide Functionalized Inorganic Nanoparticles for Cancer-Related Bioanalytical and Biomedical Applications.

In order to improve their bioapplications, inorganic nanoparticles (NPs) are usually functionalized with specific biomolecules. Peptides with short amino acid sequences have attracted great attention in the NP functionalization since they are easy to be synthesized on a large scale by the automatic synthesizer and can integrate various functionalities including specific biorecognition and therapeutic function into one sequence. Conjugation of peptides with NPs can generate novel theranostic/drug delivery nanosystems with active tumor targeting ability and efficient nanosensing platforms for sensitive detection of various analytes, such as heavy metallic ions and biomarkers. Massive studies demonstrate that applications of the peptide-NP bioconjugates can help to achieve the precise diagnosis and therapy of diseases. In particular, the peptide-NP bioconjugates show tremendous potential for development of effective anti-tumor nanomedicines. This review provides an overview of the effects of properties of peptide functionalized NPs on precise diagnostics and therapy of cancers through summarizing the recent publications on the applications of peptide-NP bioconjugates for biomarkers (antigens and enzymes) and carcinogens (e.g., heavy metallic ions) detection, drug delivery, and imaging-guided therapy. The current challenges and future prospects of the subject are also discussed.

Role of Matrix Metalloproteinases 7 in the Pathogenesis of Laryngopharyngeal Reflux: Decreased E-cadherin in Acid exposed Primary Human Pharyngeal Epithelial Cells.

Cleavage of E-cadherin and the resultant weakness in the cell-cell links in the laryngeal epithelium lining is induced by exposure to acidic contents of the refluxate. Herein, we aimed to evaluate the role of matrix metalloproteinases (MMPs) in inducing E-cadherin level changes following acid exposure to the human pharyngeal mucosal cells. E-cadherin levels were inversely correlated with the duration of acid exposure. Treatment with actinonin, a broad MMP inhibitor, inhibited this change. Immunocytochemical staining and transepithelial permeability test revealed that the cell surface staining of E-cadherin decreased and transepithelial permeability increased after acid exposure, which was significantly inhibited by the MMP inhibitor. Among the various MMPs analyzed, the mRNA for MMP-7 in the cellular component was upregulated, and the secretion and enzymatic activity of MMP-7 in the culture media increased with the acid treatment. Consequently, MMP-7 plays a significant role in the degradation of E-cadherin after exposure to a relatively weak acidic condition that would be similar to the physiologic condition that occurs in Laryngopharyngeal reflux disease patients.

Encapsulation of individual living cells with enzyme responsive polymer nanoshell.

Cell delivery in cell therapy is typically challenged by the low cell survival rate and immunological rejection during cells injection and circulation. Encapsulation of cells with semipermeable hydrogels or membranes can improve cell viability by resisting high shear force and inhibit immune response with the physical isolation effect. Herein, the individual HeLa cells and human mesenchymal stem cells (hMSCs) were encapsulated with enzyme responsive polymer nanoshell. The encapsulation shell was prepared via the Layer-by-Layer (LbL) assembly of functionalized gelatin and click chemistry of peptide linker and gelatin. The encapsulated cells showed high cell viability and could resist the physical stress. Moreover, the encapsulation shell had a prolonged encapsulation sustaining period and could effectively prevent the invasion of external entities. In addition, on-site cell release was realized via enzymolysis of the encapsulation shell by human matrix metalloproteinase-7 (MMP-7), an overexpressed enzyme on tumor area. The finding of this study proved a potential approach in cell therapy, especially for cell-based cancer therapy.

Dual-reaction triggered sensitivity amplification for ultrasensitive peptide-cleavage based electrochemical detection of matrix metalloproteinase-7.

In this work, a new strategy of dual-reaction triggered sensitivity amplification for ultrasensitive electrochemical detection of matrix metalloproteinase-7 (MMP-7) was developed. The sensitivity of amperometric biosensor relies on the current signal differences (ΔI) caused by per unit concentration target. Benefited from dual-reaction catalytic activities of Pd nanoparticles, dual catalytic reactions were implemented in the biosensor to amplify the ΔI: (1) Fenton-like reaction was triggered by the probes to degrade redox species methylene blue; (2) catalytic precipitation reaction was followed subsequently to generate insoluble precipitation by 4-chloro-1-naphthol oxidation. Dual-enhancement of ΔI triggered by Pd nanoparticle-based catalytic probes significantly improved the detection performance of the biosensor. The peptide-cleavage based biosensor integrated Pd nanoparticle-based catalytic probes with reduced graphene oxide-Au/methylene blue-sodium alginate hydrogel (Au-rGO/MB-SA) nanocomposites substrate for ultrasensitive detection of MMP-7. Under optimal conditions, the proposed biosensor exhibited a wide linear range from 10 fg mL-1 to 10 ng mL-1 with an ultralow detection limit of 3.1 fg mL-1. This strategy successfully combines the multiple catalytic reactions triggered by nanomaterials with peptide-cleavage pattern in electrochemical biosensor, providing a promising method for detection of other proteases.

Matrix metalloproteinase-7 induces homotypic tumor cell aggregation via proteolytic cleavage of the membrane-bound Kunitz-type inhibitor HAI-1.

Matrix metalloproteinase-7 (MMP-7) plays important roles in tumor progression and metastasis. Our previous studies have demonstrated that MMP-7 binds to colon cancer cells via cell surface-bound cholesterol sulfate and induces significant cell aggregation by cleaving cell-surface protein(s). These aggregated cells exhibit a dramatically enhanced metastatic potential. However, the molecular mechanism inducing this cell-cell adhesion through the proteolytic action of MMP-7 remained to be clarified. Here, we explored MMP-7 substrates on the cell surface; the proteins on the cell surface were first biotinylated, and a labeled protein fragment specifically released from the cells after MMP-7 treatment was analyzed using LC-MS/MS. We found that hepatocyte growth factor activator inhibitor type 1 (HAI-1), a membrane-bound Kunitz-type serine protease inhibitor, is an MMP-7 substrate. We also found that the cell-bound MMP-7 cleaves HAI-1 mainly between Gly451 and Leu452 and thereby releases the extracellular region as soluble HAI-1 (sHAI-1). We further demonstrated that this sHAI-1 can induce cancer cell aggregation and determined that the HAI-1 region corresponding to amino acids 141-249, which does not include the serine protease inhibitor domain, has the cell aggregation-inducing activity. Interestingly, a cell-surface cholesterol sulfate-independent proteolytic action of MMP-7 is critical for the sHAI-1-mediated induction of cell aggregation, whereas cholesterol sulfate is needed for the MMP-7-catalyzed generation of sHAI-1. Considering that MMP-7-induced cancer cell aggregation is an important mechanism in cancer metastasis, we propose that sHAI-1 is an essential component of MMP-7-induced stimulation of cancer metastasis and may therefore represent a suitable target for antimetastatic therapeutic strategies.

MMP-7 cleaves amyloid ß fragment peptides and copper ion inhibits the degradation.

The extracellular deposition of amyloid ß (Aß) is known to be the fundamental cause of Alzheimer's disease (AD). Aß1-42, generated by ß-secretases from the amyloid precursor protein (APP), is the main component of neuritic plaque, and the aggregation of this protein is shown to be dependent to an extent on metal ions such as copper and zinc. However, the mechanism by which Cu2+ affects the physicochemical properties of Aß1-42 or the central nervous system is still under debate. A recent series of studies have demonstrated that both the soluble-type matrix metalloproteinases (MMP-2 and MMP-9) and the membrane-type matrix metalloproteinase (MT1-MMP) are capable of degrading Aß peptides. MMP-7, one of the soluble-type matrix metalloproteinases, is expressed in hippocampal tissue; however, less information is available concerning the pathophysiological roles of this enzyme in the process and/or progress of Alzheimer's disease. In this study, we examined the degradation activity of MMP-7 against various Aß1-42's fragment peptides and the effect of Cu2+. Although Aß22-40 was degraded by MMP-7 regardless of Cu2+, Cu2+ inhibited the degradation of Aß1-19, Aß11-20, and Aß11-29 by MMP-7. These results indicate that MMP-7 is capable of degrading Aß1-42, and that Aß1-42 acquired resistance against MMP-7 cleavage through Cu2+-binding and structure changes. Our results demonstrate that MMP-7 may play an important role in the defensive mechanism against the aggregation of Aß1-42, which gives rise to the pathology of AD.

Peripheral membrane associations of matrix metalloproteinases.

Water soluble matrix metalloproteinases (MMPs) have been regarded as diffusing freely in the extracellular matrix. Yet multiple MMPs are also observed at cell surfaces. Their membrane-proximal activities include sheddase activities, collagenolysis, bacterial killing, and intracellular trafficking reaching as far as the nucleus. The catalytic domains of MMP-7 and MMP-12 bind bilayers peripherally, each in two different orientations, by presenting positive charges and a few hydrophobic groups to the surface. Related peripheral membrane associations are predicted for other soluble MMPs. The peripheral membrane associations may support pericellular proteolysis and endocytosis. The isolated soluble domains of MT1-MMP can also associate with membranes. NMR assays suggest transient association of the hemopexin-like domains of MT1-MMP and MMP-12 with lipid bilayers. Peripheral association of soluble MMP domains with bilayers or heparin sulfate proteoglycans probably concentrates them near the membrane. This could increase the probability of forming complexes with membrane-associated proteins, such as those targeted for proteolysis. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Biochemical characterization and zinc binding group (ZBGs) inhibition studies on the catalytic domain of MMP7 (cdMMP7).

Matrix metalloproteinase 7 (MMP7/matrilysin-1) has been implicated in many pathological conditions, such as in cancer and inflammatory diseases; therefore, MMP7 has been targeted for drugs. Success in developing a clinical inhibitor, which exhibits suitable specificity and selectivity, will likely require structural and/or kinetic evaluation of enzyme/inhibitor interactions. To enable these future studies we herein describe the over-expression, purification, and characterization of the catalytic domain of MMP7 (cdMMP7). cdMMP7 was over-expressed in an E. coli over-expression system, and the resulting enzyme was processed into inclusion bodies, which were subsequently solubilized, enabling the enzyme to be re-folded into a catalytically-active form. cdMMP7 was shown to bind 1.8eq of Zn(II), exhibit steady-state kinetic constants of 0.4s-1 for kcat and 23µM for Km, and yield CD and fluorescence spectra that are consistent with a properly-folded enzyme. Pre-steady state kinetic studies yielded kinetic mechanisms of cdMMP7, and these mechanisms are similar to those of other MMPs. Inhibition studies on cdMMP7 with four zinc binding group (ZBG) inhibitors showed that maltol, thiomaltol, and allothiomaltol are better inhibitors with lower IC50 values and lower Kd values against cdMMP7 and cdMMP16 than the commonly-used ZBG inhibitor acetohydroxamic acid. Docking studies suggest that improved inhibitory character may be due to interactions with the S1' substrate binding pocket. Finally, a ZnCo-heterobimetallic analog of cdMMP7 with Co(II) bound in the catalytic site was prepared and characterized. This study describes a well-characterized analog of MMP7 that is available for future inhibitor design efforts.

RAMA casein zymography: Time-saving and highly sensitive casein zymography for MMP7 and trypsin.

To detect metalloproteinase-7 (MMP7), zymography is conducted using a casein substrate and conventional CBB stain. It has disadvantages because it is time consuming and has low sensitivity. Previously, a sensitive method to detect MMP7 up to 30 pg was reported, however it required special substrates and complicated handlings. RAMA casein zymography described herein is rapid, sensitive, and reproducible. By applying high-sensitivity staining with low substrate conditions, the staining process is completed within 1 h and sensitivity was increased 100-fold. The method can detect 10 pg MMP7 by using commercially available casein without complicated handlings. Moreover, it increases detection sensitivity for trypsin.

Temporally degradable collagen-mimetic hydrogels tuned to chondrogenesis of human mesenchymal stem cells.

Tissue engineering strategies for repairing and regenerating articular cartilage face critical challenges to recapitulate the dynamic and complex biochemical microenvironment of native tissues. One approach to mimic the biochemical complexity of articular cartilage is through the use of recombinant bacterial collagens as they provide a well-defined biological 'blank template' that can be modified to incorporate bioactive and biodegradable peptide sequences within a precisely defined three-dimensional system. We customized the backbone of a Streptococcal collagen-like 2 (Scl2) protein with heparin-binding, integrin-binding, and hyaluronic acid-binding peptide sequences previously shown to modulate chondrogenesis and then cross-linked the recombinant Scl2 protein with a combination of matrix metalloproteinase 7 (MMP7)- and aggrecanase (ADAMTS4)-cleavable peptides at varying ratios to form biodegradable hydrogels with degradation characteristics matching the temporal expression pattern of these enzymes in human mesenchymal stem cells (hMSCs) during chondrogenesis. hMSCs encapsulated within the hydrogels cross-linked with both degradable peptides exhibited enhanced chondrogenic characteristics as demonstrated by gene expression and extracellular matrix deposition compared to the hydrogels cross-linked with a single peptide. Additionally, these combined peptide hydrogels displayed increased MMP7 and ADAMTS4 activities and yet increased compression moduli after 6 weeks, suggesting a positive correlation between the degradation of the hydrogels and the accumulation of matrix by hMSCs undergoing chondrogenesis. Our results suggest that including dual degradation motifs designed to respond to enzymatic activity of hMSCs going through chondrogenic differentiation led to improvements in chondrogenesis. Our hydrogel system demonstrates a bimodal enzymatically degradable biological platform that can mimic native cellular processes in a temporal manner. As such, this novel collagen-mimetic protein, cross-linked via multiple enzymatically degradable peptides, provides a highly adaptable and well defined platform to recapitulate a high degree of biological complexity, which could be applicable to numerous tissue engineering and regenerative medicine applications.

Bio-informatics analysis of renal carcinoma gene matrix metalloproteinase-7.

BACKGROUND: Renal cancer is one of the common malignant tumors of the urinary system, seriously threatening human being's health. The current discoveries, however, are far enough for efficient and secure treatment of renal cancer. AIMS: The aim was to explore the mechanism of matrix metalloproteinase-7 (MMP-7) protein in renal carcinoma cell metastasis by bioinformatics analysis. MATERIALS AND METHODS: Bioinformatics methods were used to analyze the composition of amino acids, as well as transmembrane structure, coiled coils, subcellular localization, signal peptide, functions and structures at all levels. RESULTS AND CONCLUSIONS: It showed that the gene MMP-7 totally had 1131 bp. A peptide chain containing 267 amino acids was encoded in the coding region. Based on random coil, α helix, and further super-helix, it had formed a stable neutral hydrophilic protein. The subcellular location analysis indicated that the protein was located outside the cell. The mature peptide started from the 18th amino acid, and its front-end was the sequence of the signal peptide, belonging to the secreted protein. Analysis of the functional domain showed that this protein had two functional domains, the PG binding domain, and the zinc finger binding domain. Moreover, the protein, which was cross-linked with it, was also one related to cancer cell proliferation and metastasis. To sum up, MMP-7 is a stable neutral hydrophilic secreted protein, and it may play a vital role in the invasion and metastasis of cancer cells.

Charge-Triggered Membrane Insertion of Matrix Metalloproteinase-7, Supporter of Innate Immunity and Tumors.

Matrix metalloproteinase-7 (MMP-7) sheds signaling proteins from cell surfaces to activate bacterial killing, wound healing, and tumorigenesis. The mechanism targeting soluble MMP-7 to membranes has been investigated. Nuclear magnetic resonance structures of the zymogen, free and bound to membrane mimics without and with anionic lipid, reveal peripheral binding to bilayers through paramagnetic relaxation enhancements. Addition of cholesterol sulfate partially embeds the protease in the bilayer, restricts its diffusion, and tips the active site away from the bilayer. Its insertion of hydrophobic residues organizes the lipids, pushing the head groups and sterol sulfate outward toward the enzyme's positive charge on the periphery of the enlarged interface. Fluorescence probing demonstrates a similar mode of binding to plasma membranes and internalized vesicles of colon cancer cells. Binding of bilayered micelles induces allosteric activation and conformational change in the auto-inhibitory peptide and the adjacent scissile site, illustrating a potential intermediate in the activation of the zymogen.

Collagen-mimetic peptide-modifiable hydrogels for articular cartilage regeneration.

Regenerative medicine strategies for restoring articular cartilage face significant challenges to recreate the complex and dynamic biochemical and biomechanical functions of native tissues. As an approach to recapitulate the complexity of the extracellular matrix, collagen-mimetic proteins offer a modular template to incorporate bioactive and biodegradable moieties into a single construct. We modified a Streptococcal collagen-like 2 protein with hyaluronic acid (HA) or chondroitin sulfate (CS)-binding peptides and then cross-linked with a matrix metalloproteinase 7 (MMP7)-sensitive peptide to form biodegradable hydrogels. Human mesenchymal stem cells (hMSCs) encapsulated in these hydrogels exhibited improved viability and significantly enhanced chondrogenic differentiation compared to controls that were not functionalized with glycosaminoglycan-binding peptides. Hydrogels functionalized with CS-binding peptides also led to significantly higher MMP7 gene expression and activity while the HA-binding peptides significantly increased chondrogenic differentiation of the hMSCs. Our results highlight the potential of this novel biomaterial to modulate cell-mediated processes and create functional tissue engineered constructs for regenerative medicine applications.

Inhibition of epidermal growth factor receptor signaling prohibits metastasis of gastric cancer via downregulation of MMP7 and MMP13.

The molecular pathway regulating gastric carcinoma (GC) invasiveness and metastasis remains elusive. Here, we detected significant increase in the phosphorylated epidermal growth factor receptor (pEGFR), MMP7, and MMP13 in the resected GC, compared with the adjacent normal tissue, in patients. Moreover, strong positive correlation was detected between pEGFR and MMP7, and between pEGFR and MMP13 in GC. To examine whether a causal link exists, we used two human GC lines, SNU-5 and AGS, to study the cross talk between EGFR signaling activation, and expression of MMP7 and MMP13. We found that EGF-induced EGFR phosphorylation activated both MMP7 and MMP13, and consequently cancer invasiveness. EGF-induced activation of MMP7 and MMP13 can be both inhibited by use of an inhibitor for EGFR. EGF-induced activation of MMP7 can be also significantly inhibited by use of an inhibitor for Akt, but not an inhibitor for ERK1/2, while EGF-induced activation of MMP13 can be significantly inhibited by use of an inhibitor for ERK1/2, but not by an inhibitor for Akt. These data suggest that EGF-induced activation of MMP7 and MMP13 in GC is through phosphatidylinositol 3-kinase (PI3K) and extracellular-related kinase/mitogen-activated protein kinase (ERK/MAPK) signaling pathway, respectively. Our study thus highlights EGFR signaling regulated MMP7 and MMP13 activation as molecular basis for metastasis of GC, and further demonstrate that different signaling pathway cascades are involved in the downstream signaling transduction.

Inhibition of fibroblast growth factor receptor signaling impairs metastasis of hepatocellular carcinoma.

The molecular mechanism underlying metastasis of hepatocellular carcinoma (HCC) remains elusive. Here, we showed that matrix metalloproteinase (MMP) 7 and MMP26 levels are significantly higher in the resected HCC than in the adjacent healthy hepatic cells from the patients. Moreover, a strong correlation of the levels of MMP7 or MMP26 with the phosphorylated fibroblast growth factor receptor 2 (FGFR2) was detected. To prove a causal link between the activation of FGFR signaling pathway and expression of MMP7 and MMP26, we used two human HCC lines, HepG2 and HuH-7, to study the underlying molecular basis. We found that FGF1-induced FGFR2 phosphorylation in either line resulted in significant activation of MMP7 and MMP26 and consequently an increase in cancer invasiveness. Inhibition of FGFR2 phosphorylation in HCC abolished FGF1-stimulated MMP7 and MMP26 expression, suggesting that activation of the FGFR signaling pathway in HCC may promote cancer metastasis by inducing MMP7 and MMP26 expression. To define the signal transduction cascades downstream of FGFR2 activation for MMP7 and MMP26 activation, we applied specific inhibitors for phosphatidylinositol-3 kinase (PI3K), extracellular signal-related kinase/mitogen-activated protein kinase (ERK/MAPK), and Jun N-terminal kinase (JNK), respectively, to the FGF1-stimulated HCC cells. We found that only inhibition of JNK significantly decreased the activation of MMP26 in response to FGF1 stimulation, and only inhibition of PI3K significantly decreased the activation of MMP7 in response to FGF1 stimulation, suggesting that the activation of the FGFR2 signaling may activate PI3K to activate MMP7 and activate JNK to activate MMP26, in HCC. Our study thus highlights the FGFR2 signaling pathway and MMP7 and MMP26 as novel therapeutic targets for HCC.

Effects of heparin and cholesterol sulfate on the activity and stability of human matrix metalloproteinase 7.

Sulfated glycosaminoglycans and sulfated lipids are involved in the biological functions of human matrix metalloproteinase 7 (MMP-7). In this study, the effects of heparin and cholesterol sulfate (CS) on the activity and stability of MMP-7 in the hydrolysis of a synthetic substrate, (7-methoxycoumarin-4-yl)acetyl-l-Pro-l-Leu-Gly-l-Leu-[N(3)-(2,4-dinitrophenyl)-l-2,3-diaminopropionyl]-l-Ala-l-Arg-NH2, were examined. Heparin increased activity by decreasing Km, and the Km values for 0 and 50 µM heparin were 57 ± 8 and 19 ± 5 µM, respectively. CS decreased activity in a non-competitive inhibitory manner with a Ki value of 11 ± 3 µM. In thermal incubation at 50-70 °C, heparin increased relative activity (the ratio of kcat/Km of MMP-7 with incubation to that without it), while CS decreased relative activity. These results indicate that heparin increases the activity and stability of MMP-7, while CS decreases them.

Pericellular proteolysis by matrix metalloproteinase-7 is differentially modulated by cholesterol sulfate, sulfatide, and cardiolipin.

Matrix metalloproteinase (MMP)-7 binds to cell surface cholesterol sulfate (CS) and acts as a membrane-associated protease. We have previously found that CS modulates the substrate preference of MMP-7, thereby regulating its pericellular proteolytic action. MMP-7 potentially associates with the cell surface via sulfatide (SM4) and cardiolipin (CL) when they are overexpressed on the cell surface. Here, we investigated the molecular interaction between these acidic lipids and MMP-7 or its substrates, and their effects on the activity of MMP-7. Studies using MMP-7 variants with low CS-binding ability suggested that these lipids interact with a similar site on MMP-7. The hydroxamate-based MMP inhibitor TAPI-1 markedly reduced the affinity of MMP-7 for CS and CL, whereas that for SM4 was not affected by TAPI-1. These three acidic lipids also had different effects on the hydrolytic activity of MMP-7 towards a small peptide substrate: SM4, CL and CS reduced the activity to 80%, 92%, and 20%, respectively. Nevertheless, SM4 and CS similarly accelerated the MMP-7-catalyzed degradation of fibronectin and laminin-332, whereas CL did not. The increased proteolysis of substrate was observed only when both substrate and enzyme had affinity for the lipid, suggesting that the lipids probably bring the reactants into closer proximity. Furthermore, MMP-7 bound to cell surface SM4 or CS cleaved specific cell surface proteins and released similar fragments, whereas the cleavage was not stimulated by cell surface CL-bound MMP-7. This study provides a novel mechanism by which acidic lipids differentially regulate pericellular proteolysis by MMP-7 through allosteric alteration of the substrate-binding site and their inherent affinities for MMP-7 substrates.

Survivin promotes the invasion of human colon carcinoma cells by regulating the expression of MMP­7.

Increased expression levels of survivin are crucial for invasion activity in several types of human cancer, including colon carcinoma. However, the molecular mechanisms whereby survivin regulates cancer invasion have not been completely elucidated. To the best of our knowledge, this study is the first to investigate the role of matrix metalloprotease­7 (MMP­7) in cell invasion that is induced by survivin by using in vitro assays, including western blot, immunofluorescence and qPCR analyses. The results demonstrated that the ectopic expression of survivin significantly promoted the invasive activity of colon carcinoma cells (SW620 and HCT­116) and resulted in increased levels of MMP­7 activation. By contrast, the small interfering RNA (siRNA)­based knockdown of survivin markedly reduced cell migration and led to a dose­dependent decrease in MMP­7 expression levels. Compared with the controls, knockdown of MMP­7 by siRNA in colon carcinoma cells led to reduced invasion ability, whereas no obvious changes were observed when MMP­7 expression was silenced in survivin­overexpressing colon carcinoma cells. These findings demonstrate that MMP­7 is crucial for survivin­mediated invasiveness, suggesting that the survivin­mediated MMP­7 signaling pathway is a potential therapeutic target for the treatment of colon carcinoma.

CENCALC: a computational tool for conformational entropy calculations from molecular simulations.

We present the CENCALC software that has been designed to estimate the conformational entropy of single molecules from extended Molecular Dynamics (MD) simulations in the gas-phase or in solution. CENCALC uses both trajectory coordinates and topology information in order to characterize the conformational states of the molecule of interest by discretizing the time evolution of internal rotations. The implemented entropy methods are based on the mutual information expansion, which is built upon the converged probability density functions of the individual torsion angles, pairs of torsions, triads, and so on. Particularly, the correlation-corrected multibody local approximation selects an optimum cutoff in order to retrieve the maximum amount of genuine correlation from a given MD trajectory. We illustrate these capabilities by carrying out conformational entropy calculations for a decapeptide molecule either in its unbound form or in complex with a metalloprotease enzyme. CENCALC is distributed under the GNU public license at http://sourceforge.net/projects/cencalc/.