Metalloproteinase 9 is the outer executioner of desmoglein 3 in apoptotic keratinocytes

Plasma Exosomal microRNA Profile Reveals miRNA 148a-3p Downregulation in the Mucosal-Dominant Variant of Pemphigus Vulgaris

The mucosal-dominant variant of pemphigus vulgaris (MPV) is an autoimmune disease characterized by oral mucosal blistering and circulating pathogenic IgG antibodies against desmoglein 3 (Dsg3), resulting in life-threatening bullae and erosion formation. Recently, microRNAs (miRNAs) have emerged as promising players in the diagnosis and prognosis of several pathological states. For the first time, we have identified a different expression profile of miRNAs isolated from plasma-derived exosomes (P-EVs) of MPV patients positive for antibodies against Dsg3 (Dsg3-positive) compared to healthy controls. Moreover, a dysregulated miRNA profile was confirmed in MPV tissue biopsies. In particular, a strong downregulation of the miR-148a-3p expression level in P-EVs of MPV patients compared to healthy controls was demonstrated. Bioinformatics prediction analysis identifies metalloproteinase-7 (MMP7) as a potential miR-148a-3p target. An in vitro acantholysis model revealed that the miR-148a-3p expression level was dramatically downregulated after treatment with Dsg3 autoantibodies, with a concomitant increase in MMP7 expression. The increased expression of MMP7 leads to the disruption of intercellular and/or extracellular matrix adhesion in an in vitro cellular model of MPV, with subsequent cell dissociation. Overexpression of miR-148a-3p prevented cell dissociation and regressed MMP7 upregulation. Our findings suggest a pivotal role of P-EV cargo in regulating molecular mechanisms involved in MPV pathogenesis and indicate them as potential MPV therapeutic targets.

A Scoping Review of the Role of Metalloproteinases in the Pathogenesis of Autoimmune Pemphigus and Pemphigoid

Pemphigus and pemphigoid diseases are potentially life-threatening autoimmune blistering disorders that are characterized by intraepithelial and subepithelial blister formation, respectively. In both disease groups, skin and/or mucosal blistering develop as a result of a disruption of intercellular adhesion (pemphigus) and cell-extracellular matrix (ECM) adhesion (pemphigoid). Given that metalloproteinases can target cell adhesion molecules, the purpose of the present study was to investigate the role of these enzymes in the pathogenesis of these bullous dermatoses. Studies examining MMPs (matrix metalloproteinases) and the ADAM (a disintegrin and metalloproteinase) family of proteases in pemphigus and pemphigoid were selected from articles published in the repository of the National Library of Medicine (MEDLINE/PubMed) and bioRxiv. Multiple phases of screening were conducted, and relevant data were extracted and tabulated, with 29 articles included in the final qualitative analysis. The majority of the literature investigated the role of specific components of the MMP family primarily in bullous pemphigoid (BP) whereas studies that focused on pemphigus were rarer. The most commonly studied metalloproteinase was MMP-9 followed by MMP-2; other MMPs included MMP-1, MMP-3, MMP-8, MMP-12 and MMP-13. Molecules related to MMPs were also included, namely, ADAM5, 8, 10, 15, 17, together with TIMP-1 and TIMP-3. The results demonstrated that ADAM10 and MMP-9 activity is necessary for blister formation in experimental models of pemphigus vulgaris (PV) and BP, respectively. The data linking MMPs to the pathogenesis of experimental BP were relatively strong but the evidence for involvement of metalloproteinases in PV was more tentative. These molecules represent potential candidates for the development of mechanism-based treatments of these blistering diseases.

Internalization of Non-Clustered Desmoglein 1 without Depletion of Desmoglein 1 from Adhesion Complexes in An Experimental Model of the Autoimmune Disease Pemphigus Foliaceus

Serum antibodies against desmoglein 1 (Dsg1) are known to induce the clinical and histological manifestations of pemphigus foliaceus (PF), autoimmune bullous disease targeting skin. The basic pathophysiological phenomenon of PF blistering is the disruption of epithelial integrity in the granular layer of the epidermis due to separation of keratinocytes from one another, or acantholysis. In this report we investigate the changes in subcellular distribution of Dsg1 in response to serum of patients with PF by using an in vitro model of PF. Immunofluorescence analysis on HaCaT cells indicates that non-clustered Dsg1 is markedly internalized after exposure to serum. However, binding of PF IgG to Dsg1-rich adhesion complexes (desmosomes) does not cause disruption of such structures nor depletion of clustered Dsg1, as revealed by colocalization of PF IgG and Dsg1 in a punctate staining on cell membrane 24 hours after treatment. Furthermore, morphological studies demonstrate that the dramatic alterations induced by PF sera are not the result of apoptotic programs. Taken together, our data strongly suggest that anti-Dsg1 antibodies from PF serum could cause the internalization of non-clustered Dsg1 and perturb the formation of new desmosomes but not directly disrupt Dsg1-containing junctions when stable contacts are already formed.

150th Anniversary Series: Desmosomes and the Hallmarks of Cancer

Desmosomes represent adhesive, spot-like intercellular junctions that in association with intermediate filaments mechanically link neighboring cells and stabilize tissue architecture. In addition to this structural function, desmosomes also act as signaling platforms involved in the regulation of cell proliferation, differentiation, migration, morphogenesis, and apoptosis. Thus, deregulation of desmosomal proteins has to be considered to contribute to tumorigenesis. Proteolytic fragmentation and downregulation of desmosomal cadherins and plaque proteins by transcriptional or epigenetic mechanisms were observed in different cancer entities suggesting a tumor-suppressive role. However, discrepant data in the literature indicate that context-dependent differences based on alternative intracellular, signal transduction lead to altered outcome. Here, modulation of Wnt/β-catenin signaling by plakoglobin or desmoplakin and of epidermal growth factor receptor signaling appears to be of special relevance. This review summarizes current evidence on how desmosomal proteins participate in carcinogenesis, and depicts the molecular mechanisms involved.

Senescent cancer-associated fibroblasts secrete active MMP-2 that promotes keratinocyte dis-cohesion and invasion

Background:

Previous studies have demonstrated that senescent cancer-associated fibroblasts (CAFs) derived from genetically unstable oral squamous cell carcinomas (GU-OSCC), unlike non-senescent CAFs from genetically stable carcinomas (GS-OSCC), promoted keratinocyte invasion in vitro in a paracrine manner. The mechanism by which this occurs is unclear.

Methods:

Previous work to characterise the senescent-associated secretory phenotype (SASP) has used antibody arrays, technology that is limited by the availability of suitable antibodies. To extend this work in an unbiased manner, we used 2D gel electrophoresis and mass spectroscopy for protein identification. Matrix metalloproteinases (MMPs) were investigated by gelatin zymography and western blotting. Neutralising antibodies were used to block key molecules in the functional assays of keratinocyte adhesion and invasion.

Results:

Among a variety of proteins that were differentially expressed between CAFs from GU-OSCC and GS-OSCC, MMP-2 was a major constituent of senescent CAF-CM derived from GU-OSCC. The presence of active MMP-2 was confirmed by gelatine zymography. MMP-2 derived from senescent CAF-CM induced keratinocyte dis-cohesion and epithelial invasion into collagen gels in a TGF-β-dependent manner.

Conclusions:

Senescent CAFs from GU-OSCC promote a more aggressive oral cancer phenotype by production of active MMP-2, disruption of epithelial adhesion and induction of keratinocyte invasion.

Nerve growth factor promotes corneal epithelial migration by enhancing expression of matrix metalloprotease-9

PURPOSE

Nerve growth factor (NGF) is a neuropeptide essential for the development, survival, growth, and differentiation of corneal cells. Its effects are mediated by both TrkA and p75 receptors. Clinically relevant use of NGF was introduced to treat neurotrophic ulcerations in patients. Herein, we examine the mechanisms by which NGF enhances epithelial wound healing both in vivo and in vitro.

METHODS

An animal model using adult hens was implemented for the in vivo experiments. Laser ablation keratectomy was performed and animals were observed for up to 7 days. Epithelial healing was measured with fluorescein. In addition, proliferation was measured using BrdU incorporation and both TrkA and matrix metalloprotease-9 (MMP-9) expression were measured by immunohistochemistry (IHC) and Western blot (WB). In vitro experiments were carried out with telomerase-immortalized human corneal epithelial cells (HCLE). The rate of proliferation was measured using a colorimetric assay and BrdU incorporation. Real-time migration was evaluated with an inverted microscope. MMP-9 expression was evaluated by immunocytochemistry (ICC), WB, zymography, and RT-PCR. Finally, beta-4 integrin (β4) expression was assessed by ICC and WB.

RESULTS

Faster epithelial healing was observed in NGF-treated corneas compared with controls (P < 0.01). These corneas showed increased proliferation, TrkA upregulation, and enhanced MMP-9 presence (P < 0.01). In vitro, faster spreading and migration were observed in response to NGF (P < 0.01). Enhanced proliferation, as well as enhanced TrkA and MMP-9 expression, and decreased β4 levels were observed after adding NGF (P < 0.01).

CONCLUSIONS

NGF plays a major role during the epithelial healing process by promoting migration, a process that is accelerated by cell spreading. This effect is mediated by both the upregulation of MMP-9 and cleavage of β4 integrin.

Desmosomal adhesion and pemphigus vulgaris: the first half of the story

Pemphigus vulgaris (PV) is a paradigm of autoimmune disease affecting intercellular adhesion. The mechanisms that lead to cell-cell detachment (acantholysis) have crucial therapeutic implications and are currently undergoing major scrutiny. The first part of this review focuses on the classical view of the pathogenesis of PV, which is dominated by the cell adhesion molecules of the desmosome, namely desmogleins (Dsgs). Cloning of the DSG3 gene, generation DSG3 knock-out mice and isolation of monoclonal anti-Dsg3 IgG have aided to clarify the pathogenic mechanisms of PV, which are in part dependent on the fate of desmosomal molecules. These include perturbation of the desmosomal network at the transcriptional, translational, and interaction level, kinase activation, proteinase-mediated degradation, and hyper-adhesion. By the use of PV models, translational research has in turn helped shed light into the basic structure, function, and dynamics of assembly of desmosomal cadherins. The combined efforts of basic and applied research has resulted in tremendous advance into the understanding of epidermal adhesion and helped debunk old myths on the supposedly unique role of desmogleins in the mechanisms of cell-cell detachment in PV.

Modulation of cell-cell junctional complexes by matrix metalloproteinases

The ameloblast cell layer of the enamel organ is in contact with the forming enamel as it develops into the hardest substance in the body. Ameloblasts move in groups that slide by one another as the enamel layer thickens. Each ameloblast is responsible for the formation of one enamel rod, and the rods are the mineralized trail that moving ameloblasts leave behind. Matrix metalloproteinases (MMPs) facilitate cell movement in various tissues during development, and in this review we suggest that the tooth-specific MMP, enamelysin (MMP20), facilitates ameloblast movements during enamel development. Mmp20 null mice have thin brittle enamel with disrupted rod patterns that easily abrades from the underlying dentin. Strikingly, the Mmp20 null mouse enamel organ morphology is noticeably dysplastic during late-stage development, when MMP20 is no longer expressed. We suggest that in addition to its role of cleaving enamel matrix proteins, MMP20 also cleaves junctional complexes present on ameloblasts to foster the cell movement necessary for formation of the decussating enamel rod pattern. Therefore, inactivation of MMP20 would result in tight ameloblast cell-cell attachments that may cause maturation-stage enamel organ dysplasia. The tight ameloblast attachments would also preclude the ameloblast movement necessary to form decussating enamel rod patterns.

Urban legends: pemphigus vulgaris

Pemphigus vulgaris (PV) is the most common type of pemphigus. PV pathogenesis is still debated, and treatment remains challenging. We investigated five controversial topics: (1) What are the target antigens in PV? (2) Do desmogleins adequately address PV pathophysiology? (3) How does acantholysis occur in PV? (4) Is PV still a lethal disease? (5) What is the role of rituximab (RTX) in PV treatment? Results from extensive literature searches suggested the following: (1) Target antigens of PV include a variety of molecules and receptors that are not physically compartmentalized within the epidermis. (2) PV is caused by a variety of autoantibodies to keratinocyte self-antigens, which concur to cause blistering by acting synergistically. (3) The concept of apoptolysis distinguishes the unique mechanism of autoantibody-induced keratinocyte damage in PV from other known forms of cell death. (4) PV remains potentially life-threatening largely because of treatment side effects, but it is uncertain which therapies carry the highest likelihood of lethal risk. (5) RTX is a very promising treatment option in patients with widespread recalcitrant or life-threatening PV. RTX's cost is an issue, its long-term side effects are still unknown, and randomized controlled trials are needed to establish the optimal dosing regimen.

Captopril modulates acetylcholinesterase in human keratinocytes

Human keratinocytes synthesize and secrete non-neuronal acetylcholine, which acts as a local cell signaling molecule, regulating functions like proliferation, cell adhesion, motility, desmosomal cell contact, and glandular activity. The keratinocyte acetylcholine axis is composed of the enzymes mediating acetylcholine synthesis (acetyltransferase) and degradation (acetylcholinesterase), and two classes of acetylcholine receptors. In this study we investigated the effect of captopril, an ACE-inhibitor, on acetylcholinesterase and acetylcholine secretion in human keratinocytes. We analyzed the level of acetylcholinesterase in HaCat and NHEK cells by RT-PCR and Western blotting analysis. In addition, the effect of captopril on AChE activity was evaluated. We found that captopril induces a strong AChE up-regulation leading to ACh degradation and reduced secretion. Our results suggest that acantholysis induced by ACE-inhibitors might be linked to altered level of Ach.

The pathogenesis of photoaging: the role of neutrophils and neutrophil-derived enzymes

The hallmark of photoaged skin is solar elastosis, which is probably an end product of elastic fiber degradation. Exposure of human skin to a certain threshold of UV, infrared radiation (IR), and heat leads to an influx of neutrophils. These neutrophils are packed with potent proteolytic enzymes capable of degrading collagen and, particularly, elastic fibers. Neutrophil-derived proteolytic enzymes are held responsible for the extracellular matrix (ECM) damage observed in several non-dermatological conditions. Furthermore, neutrophil elastase, a major product of neutrophils, is strongly associated with solar elastosis in mice. Taken together with our data that show in vivo proteolytic activity of neutrophil-derived elastase and matrix metalloproteinases (MMPs) in UV-exposed skin, we have hypothesized earlier that neutrophils are major contributors to the photoaging process. Although several groups have shown that MMPs are also induced in skin exposed to relatively low doses of UV, IR, and heat, clinical data indicate that high(er) doses of UV, IR, and heat are necessary to induce photoaging or photoaging-like pathology in the skin. Therefore, we propose that MMPs generated by suberythemogenic doses of UV and low doses of IR/heat are involved in cellular processes other than ECM degradation.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 67-72; doi:10.1038/jidsymp.2009.15.

A novel strategy based on histological protein profiling in-silico for identifying potential biomarkers in urinary bladder cancer

OBJECTIVE

To screen a publicly available immunohistochemistry (IHC) based web-atlas, to identify key proteins in bladder cancer that might serve as potential biomarkers.

MATERIALS AND METHODS

The first version of the Human Protein Atlas (HPA 1.0), with 660 proteins, was visually examined to identify proteins with a variable staining pattern among the 12 tissue samples representing bladder cancer. None or limited previous characterization in bladder cancer, as well as a supportive Western blot, were also required. The selected proteins were then evaluated in an independent set of patient samples (106 tumour samples of differing stage and grade) represented in a tissue microarray (TMAi). The IHC expression of the identified proteins in the TMAi was scored and related to tumour stage and grade.

RESULTS

The expression profiles of the 13 proteins selected from the web-atlas were confirmed in the TMAi. Expression patterns for seven proteins were significantly altered (P < 0.05) with higher stage and/or grade. Three of those (CN130, DSG3, PHF6) lack characterization in bladder cancer, whereas the remaining four proteins have previously been suggested as key proteins/potential biomarkers in cancer, some of them also in bladder cancer.

CONCLUSION

New candidate proteins for urinary bladder cancer were identified through screening of the publicly available HPA 1.0. Although further evaluation is necessary, this strategy is promising in the search for new biomarkers, with potential to improve the management of patients with this disease.

Ets1 induces dysplastic changes when expressed in terminally-differentiating squamous epidermal cells

BACKGROUND

Ets1 is an oncogene that functions as a transcription factor and regulates the activity of many genes potentially important for tumor initiation and progression. Interestingly, the Ets1 oncogene is over-expressed in many human squamous cell cancers and over-expression is highly correlated with invasion and metastasis. Thus, Ets1 is believed to mainly play a role in later stages of the oncogenic process, but not early events.

METHODOLOGY/PRINCIPAL FINDINGS

To better define the role of Ets1 in squamous cell carcinogenesis, we generated a transgenic mouse model in which expression of the Ets1 oncogene could be temporally and spatially regulated. Upon Ets1 induction in differentiating cells of stratified squamous epithelium, these mice exhibited dramatic changes in epithelial organization including increased proliferation and blocked terminal differentiation. The phenotype was completely reversed when Ets1 expression was suppressed. In mice where Ets1 expression was re-induced at a later age, the phenotype was more localized and the lesions that developed were more invasive. Many potential Ets1 targets were upregulated in the skin of these mice with the most dramatic being the metalloprotease MMP13, which we demonstrate to be a direct transcriptional target of Ets1.

CONCLUSIONS/SIGNIFICANCE

Collectively, our data reveal that upregulation of Ets1 can be an early event that promotes pre-neoplastic changes in epidermal tissues via its regulation of key genes driving growth and invasion. Thus, the Ets1 oncogene may be important for oncogenic processes in both early and late stages of tumor development.

The desmosome and pemphigus

Desmosomes are patch-like intercellular adhering junctions ("maculae adherentes"), which, in concert with the related adherens junctions, provide the mechanical strength to intercellular adhesion. Therefore, it is not surprising that desmosomes are abundant in tissues subjected to significant mechanical stress such as stratified epithelia and myocardium. Desmosomal adhesion is based on the Ca(2+)-dependent, homo- and heterophilic transinteraction of cadherin-type adhesion molecules. Desmosomal cadherins are anchored to the intermediate filament cytoskeleton by adaptor proteins of the armadillo and plakin families. Desmosomes are dynamic structures subjected to regulation and are therefore targets of signalling pathways, which control their molecular composition and adhesive properties. Moreover, evidence is emerging that desmosomal components themselves take part in outside-in signalling under physiologic and pathologic conditions. Disturbed desmosomal adhesion contributes to the pathogenesis of a number of diseases such as pemphigus, which is caused by autoantibodies against desmosomal cadherins. Beside pemphigus, desmosome-associated diseases are caused by other mechanisms such as genetic defects or bacterial toxins. Because most of these diseases affect the skin, desmosomes are interesting not only for cell biologists who are inspired by their complex structure and molecular composition, but also for clinical physicians who are confronted with patients suffering from severe blistering skin diseases such as pemphigus. To develop disease-specific therapeutic approaches, more insights into the molecular composition and regulation of desmosomes are required.

At least three phosphorylation events induced by pemphigus vulgaris sera are pathogenically involved in keratinocyte acantholysis

Intercellular adhesion among keratinocytes is guaranteed by desmosomes. Disruption of desmosomal integrity leads to cell-cell detachment or acantholysis, as it classically occurs in pemphigus vulgaris (PV), an autoimmune blistering disease of skin and mucous membranes. While purified PV IgG seems to trigger intracellular signaling that crucially involves p38 MAPK, keratinocyte acantholysis induced by whole PV serum may recruit a number of additional signals. In this study, the Pro-Q Diamond Phosphoprotein Assay was used to investigate the overall changes in protein phosphorylation levels in an in vitro model of PV. We showed that keratinocytes exposed to whole PV sera underwent at least three early and transient phosphorylation events. Two bands with apparent molecular masses of 35 and 45 kDa were found to be phosphorylated within 1 min after incubation with PV sera. A third band of about 80 kDa reached the peak of phosphorylation level after 3 hours. Morphologic evidence of cell shrinkage and acantholysis were late events and did not correlate temporally with kinase activation, suggesting that cytoskeleton reorganization is a downstream phenomenon. Interestingly, pharmacological abrogation of PV-specific protein phosphorylation was able to inhibit the cell-cell detachment, rounding up, and redistribution of Dsg3 in keratinocytes. Thus, at least three phosphorylation events are pathogenically involved in pemphigus acantholysis.

Mucocutaneous pemphigus vulgaris carrying high-titre antidesmoglein 1 antibodies with skin lesions resembling pemphigus erythematosus

Patients with pemphigus vulgaris (PV) who have both antidesmoglein (Dsg)1 and anti-Dsg3 antibodies usually develop flaccid blisters on skin and mucous membranes. We report a case of PV with crusting skin lesions resembling pemphigus erythematosus, the localized variant of pemphigus foliaceus (PF). Notably, the patient had high titres of anti-Dsg1 IgG, as assessed by ELISA. We then established an in vitro model of pemphigus, and found that patient's serum was able to induce suprabasilar acantholysis in mouse skin culture. However, epidermal splitting also occurred within the granular layer, suggesting that the pathogenic potential of such a high-titre anti-Dsg1 serum was intermediate between PV and PF. Thus, the levels of anti-Dsg1 antibodies could play a role in determining the clinical phenotype of pemphigus.

Vesicular and Bullous Disorders: Pemphigus

Pemphigus is a chronic, autoimmune disease involving the skin and Malpighian mucous membranes. Pemphigus leads to progressive blistering and subsequent erosions. This article describes the etiology and treatment of pemphigus.

A novel method to investigate pemphigus-induced keratinocyte dysmorphisms through living cell immunofluorescence microscopy

Pemphigus vulgaris (PV) blistering occurs as a result of the disruption of intercellular contacts among keratinocytes, or acantholysis. The hallmark of PV acantholysis in vitro is considered to be the retraction of keratin intermediate filaments (KIF) onto the nucleus, which parallels with loss of cell-cell adhesion and rounding up of keratinocytes. However, the fine morphological changes of keratinocytes as well as the fate of cell adhesion structures cannot be appreciated on immunofluorescence by the simple cytokeratin staining. In this paper, we show that acantholytic dysmorphisms are sharply investigated by using PV IgG as a primary antibody on metabolically quiescent living cells. Indeed, PV IgG recognise a wide spectrum of molecules and enabled us to monitor the main changes occurring in acantholytic keratinocytes, including cell shrinkage with the appearance of prickle-like processes, detachment of keratinocytes from one another and collapse of cytoskeleton-bound proteins along nuclear periphery. This method has wider applications as it could be useful for staining cell periphery of keratinocytes and changes in cell shape. Furthermore, images displayed clear and sharp contours because living cell microscopy allows to avoid antigen distortion due to cell manipulation, which usually precedes the immunolabelling.

Pemphigus vulgaris immunoglobulin G can recognize a 130 000 MW antigen other than desmoglein 3 on peripheral blood mononuclear cell surface

Pemphigus vulgaris (PV) is considered to be an autoimmune disease affecting skin and mucous membranes. Traditionally, PV autoantibodies are thought to recognize antigens located in the intercellular substance (ICS) of keratinocytes; antigens represented mainly by the desmosomal cadherin desmoglein 3 (Dsg3). Accordingly, titres of anti-ICS and anti-Dsg3 immunoglobulin G (IgG) are considered to be major laboratory criteria when making a diagnosis of PV. In this paper, we demonstrated for the first time that PV IgG bind antigen(s) expressed on the surface of peripheral blood mononuclear cells (PBMC), as revealed by immunofluorescence studies. This novel autoantigen is immunoprecipitated by PV IgG as a 130 000 molecular weight protein. However, Western blot analysis of the immunocomplexes failed to show reactivity with anti-Dsg3 monoclonal and polyclonal antibodies. Taken together, our data provide strong evidence that PV autoimmunity targets a 130 000 antigen other than Dsg3 on PBMC. This shifting from epidermis to blood cells may open new perspectives for a better understanding of pemphigus autoimmunity and more rational approaches to its treatment.

Searching for experimental models of Pemphigus vulgaris

The current knowledge on Pemphigus vulgaris (PV) pathophysiology suggests that blister formation relies on both PV IgG and non-IgG serum factors activity. PV autoimmunity seems to develop against both desmoglein 1/3 and acetylcholine receptors leading to transduction of signals to the cell mediated by phosphorilation events. Serum factors other than IgG also participate to PV acantholysis through apoptotic or cytokine-mediated mechanisms. Apart from the role played by each actor within the acantholysis, however, the current scenario arises important methodological issues. For example, the use of PV IgG or monoclonal anti-Dsg3 antibodies to experimentally reproduce the disease appears inadequate, as it does not take into account the role of non-IgG factors. On the basis of the above observations and those from our laboratories, here we propose that using whole sera from PV patients with active disease represents the most faithful manner to mimic the disease.

Inflammation dampened by gelatinase A cleavage of monocyte chemoattractant protein-3

Tissue degradation by the matrix metalloproteinase gelatinase A is pivotal to inflammation and metastases. Recognizing the catalytic importance of substrate-binding exosites outside the catalytic domain, we screened for extracellular substrates using the gelatinase A hemopexin domain as bait in the yeast two-hybrid system. Monocyte chemoattractant protein-3 (MCP-3) was identified as a physiological substrate of gelatinase A. Cleaved MCP-3 binds to CC-chemokine receptors-1, -2, and -3, but no longer induces calcium fluxes or promotes chemotaxis, and instead acts as a general chemokine antagonist that dampens inflammation. This suggests that matrix metalloproteinases are both effectors and regulators of the inflammatory response.