Electrochemical detection of bacterial endotoxin lipopolysaccharide (LPS) on gold electrode modified with DAL-PEG-DK5-PEG-OH - Antimicrobial peptide conjugate

This work describes fabrication of gold electrodes modified with peptide conjugate DAL-PEG-DK5-PEG-OH that enables ultra-sensitive detection of lipopolysaccharide (LPS) isolated from the reference strain of Escherichia coli O26:B6. The initial step of the established procedure implies immobilization of the fully protected DAL-PEG-DK5-PEG-OH peptide on the surface of the gold electrode previously modified by cysteamine. Then side chain- and Fmoc-deprotection was performed in situ on the electrode surface, followed by its incubation in 1 % of BSA solution to block non-specific bindings sites before LPS detection. The efficiency of the modification was confirmed by X-ray Photoelectron Spectroscopy (XPS) measurements. Additionally, the cyclic voltammetry (CV) and electrochemical impendance spectroscopy (EIS) were employed to monitor the effectiveness of each step of the modification. The obtained results confirmed that the presence of the surface-attached covalently bound peptide DAL-PEG-DK5-PEG-OH enables LPS detection by means of CV technique within the range from 5 × 10-13 to 5 × 10-4 g/mL in PBS solution. The established limit of detection (LOD) for EIS measurements was 4.93 × 10-21 g/mL with wide linear detection range from 5 × 10-21 to 5 × 10-14 g/mL in PBS solution. Furthermore, we confirmed the ability of the electrode to detect LPS in a complex biological samples, like mouse urine and human serum. The effectiveness of the electrodes in identifying LPS in both urine and serum matrices was confirmed for samples containing LPS at both 2.5 × 10-15 g/mL and 2.5 × 10-9 g/mL.

Caspase-like activity is associated with bacterial infection of the urine in urinary tract diseases

Urinary tract infections (UTIs) are a serious public health problem. They can be caused by a number of pathogens, but the most common are Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis and Staphylococcus saprophyticus. Bacterial infection is diagnosed by examining a urine sample. The presence of bacteria or white blood cells is determined under a microscope or a urine culture is performed. In this study, we used a panel of chromogenic substrates for the qualitative determination of specific enzyme activity in the urine of patients with confirmed bacterial infection and/or urinary tract disease. Healthy patients were used as a control group. It turned out that in the case of Escherichia coli infection, we observed the activity of the caspase subunit of the human 20S proteasome. We did not observe similar correlations for infections with other types of bacteria.

Optimization of fluorescent substrates for ADAM17 and their utility in the detection of diabetes

ADAM17 (a disintegrin and metalloproteinase 17) is a sheddase that releases various types of membrane-associated proteins, including adhesive molecules, cytokines and their receptors, and inflammatory mediators. Evidence suggests that the enzyme is involved in the proteolytic cleavage of antiaging transmembrane protein Klotho (KL). What is more, reduced serum and urinary KL levels are observed in the early stages of chronic kidney disease. This study aimed to optimise the ADAM17 specific and selective fluorescent substrates. Then, the obtained substrate was used to detect the enzyme in urine samples of patients diagnosed with diabetes. It turned out that in all cases we were able to detect proteolytic activity, which was the opposite of the healthy samples.

Initial study of the detection of ADAM 10 in the urine of type-2 diabetic patients

Diabetes mellitus (DM) is a disease of civilization. If left untreated, it can cause serious complications and significantly shortens the life time. DM is one of the leading causes of end-stage renal disease (uremia) worldwide. Early diagnosis is a prerequisite for successful treatment, preferably before the first symptoms appear. In this paper, we describe the optimization and synthesis of the internally quenched fluorescent substrate disintegrin and metalloproteinase 10 (ADAM10). Using combinatorial chemistry methods with iterative deconvolution, the substrate specificity of the enzyme in non-primed and primed positions was determined. We used the ABZ-Lys-Ile-Ile-Asn-Leu-Lys-Arg-Tyr(3-NO2)-NH2 peptide to study ADAM10 activity in urine samples collected from patients diagnosed with type 2 diabetes, compared to urine samples from healthy volunteers. The proteolytically active enzyme was present in diabetes samples, while in the case of healthy people we did not observe any activity. In conclusion, our study provides a possible basis for further research into the potential role of ADAM10 in the diagnosis of type 2 diabetes.

Role of lysosomes in insulin signaling and glucose uptake in cultured rat podocytes

Podocytes are sensitive to insulin, which governs the functional and structural integrity of podocytes that are essential for proper function of the glomerular filtration barrier. Lysosomes are acidic organelles that are implicated in regulation of the insulin signaling pathway. Cathepsin D (CTPD) and lysosome-associated membrane protein 1 (LAMP1) are major lysosomal proteins that reflect the functional state of lysosomes. However, the effect of insulin on lysosome activity and role of lysosomes in the regulation of insulin-dependent glucose uptake in podocytes are unknown. Our studies showed that the short-term incubation of podocytes with insulin decreased LAMP1 and CTPD mRNA levels. Insulin and bafilomycin A1 reduced both the amounts of LAMP1 and CTPD proteins and activity of CTPD, which were associated with a decrease in the fluorescence intensity of lysosomes that were labeled with LysoTracker. Bafilomycin A1 inhibited insulin-dependent endocytosis of the insulin receptor and increased the amounts of the insulin receptor and glucose transporter 4 on the cell surface of podocytes. Bafilomycin A1 also inhibited insulin-dependent glucose uptake despite an increase in the amount of glucose transporter 4 in the plasma membrane of podocytes. These results suggest that lysosomes are signaling hubs that may be involved in the coupling of insulin signaling with the regulation of glucose uptake in podocytes. The dysregulation of this mechanism can lead to the dysfunction of podocytes and development of insulin resistance.

Serine proteases and metalloproteases are highly increased in irritable bowel syndrome Tunisian patients

Serine proteases are involved in many biological processes and are associated with irritable bowel syndrome (IBS) pathology. An increase in serine protease activity has been widely reported in IBS patients. While most of the studies focused on host proteases, the contribution of microbial proteases are poorly studied. In the present study, we report the analysis of proteolytic activities in fecal samples from the first Tunisian cohort of IBS-M patients and healthy individuals. We demonstrated, for the first time, that metalloproteases activities were fourfold higher in fecal samples of IBS patients compared to controls. Of interest, the functional characterization of serine protease activities revealed a 50-fold increase in trypsin-like activities and a threefold in both elastase- and cathepsin G-like activities. Remarkably, we also showed a fourfold increase in proteinase 3-like activity in the case of IBS. This study also provides insight into the alteration of gut microbiota and its potential role in proteolytic modulation in IBS. Our results stressed the impact of the disequilibrium of serine proteases, metalloproteases and gut microbiota in IBS and the need of the further characterization of these targets to set out new therapeutic approaches.

Novel tools to study West Nile virus NS3 protease activity

West Nile Virus (WNV) belongs to a group of pathogenic viruses called flaviviruses. West Nile virus infection can be mild, causing so-called West Nile Fever (WNF) or severe neuroinvasive form of the disease (WNND), and ultimately even death. There are currently no known medications to prevent West Nile virus infection. Only symptomatic treatment is used. To date, there are no unequivocal tests enabling a quick and unambiguous assessment of WN virus infection. The aim of the research was to obtain specific and selective tools for determining the activity of the West Nile virus serine proteinase. Using the methods of combinatorial chemistry with iterative deconvolution, the substrate specificity of the enzyme in non-primed and primed positions was determined. The FRET ABZ-Ala-Lys-Gln-Arg-Gly-Gly-Thr-Tyr(3-NO₂)-NH₂ substrate was obtained, characterized by kinetic parameters (KM = 4.20 ± 0.32 × 10^-5 M) as for the majority of proteolytic enzymes. The obtained sequence was used to develop and synthesize highly sensitive functionalized quantum dot-based protease probes (QD). A QD WNV NS3 protease probe was obtained to detect an increase in fluorescence of 0.05 nmol enzyme in the assay system. This value was at least 20 times lower than that observed with the optimized substrate. The obtained result may be the basis for further research on the potential use of the WNV NS3 protease in the diagnosis of West Nile virus infection.

Detection of ADAM15 in urine from patients with bladder cancer

Cancer is one of the leading causes of death in the United States and Europe. Of the cancers, bladder cancer is the 10th most frequently diagnosed cancer and the 13th most frequently diagnosed cancer in men. There are many studies showing that proteolytic enzymes, e.g. A Disintegrin and Metalloproteinases (ADAMs), play a key role in the development and progression of neoplasms. In this paper, we present the use of chromogenic substrate of ADAM15 for the qualitative determination of specific activity of enzyme in urine of patients with confirmed bladder cancer. In the first step, we optimized the substrate molecule in non-primed positions using combinatorial chemistry. By means of the obtained ABZ-His-Ala-Arg-Gly-ANB-NH₂ peptide, we detected ADAM15 activity in urine samples collected from patients diagnosed with bladder cancer. In contrast, we did not observe such activity in urine obtained from healthy volunteers.

Chemical tools to monitor bladder cancer progression

BackgroundBladder cancer (BCa) is the most common cancer of the urinary system. Due to its high incidence and recurrence, as well as limited progress in the effective treatment, BCa is a challenge for today's medicine.Materials and MethodsWe used a set of chromogenic substrates to differentiate between the stages of bladder cancer progression (G1 (n = 10), G2 (n = 10), G3 (n = 10)). The proteolytic activity in individual the urine samples was determined by absorbance measurements. Then inhibitors of particular classes of enzymes were used to determine which enzymes dominate at a given stage of the neoplastic disease.ResultsThe specific activity of enzymes in the urine of patients with confirmed bladder cancer was determined separately for three (G1, G2, G3) stages of the disease development. What is more, no activity was observed in urine of healthy people (n = 10).DiscussionResearch shows that specific enzymes are associated with the development of specific stages of cancer. We suspect that the differences in the proteolytic activity of urine samples are due to the presence of a different set of enzymes, that are directly related to the particular stage of the disease.ConclusionWe obtained three substrates for monitoring individual stages of bladder cancer development.

Bile Acids: Key Players in Inflammatory Bowel Diseases?

Inflammatory bowel diseases (IBDs) have emerged as a public health problem worldwide with a limited number of efficient therapeutic options despite advances in medical therapy. Although changes in the gut microbiota composition are recognized as key drivers of dysregulated intestinal immunity, alterations in bile acids (BAs) have been shown to influence gut homeostasis and contribute to the pathogenesis of the disease. In this review, we explore the interactions involving BAs and gut microbiota in IBDs, and discuss how the gut microbiota–BA–host axis may influence digestive inflammation.

Simplified Theta-defensin [Ser3,7,12,16] RTD-2 Analog Is Involved in Proteasomal Degradation Pathway in Breast Cancer

BACKGROUND/AIM

Antimicrobial peptides are part of the innate immune response, regulate inflammation and initiate acquired immunity. This study focused on theta-defensins that have been shown to have anticancer properties.

MATERIALS AND METHODS

RTD-2 analogs were synthesized on a peptide synthesizer. Cell viability was estimated using the MTT test. Immunoprecipitation assay was conducted to determine the molecular partner of the [Ser3,7,12,16]-RTD-2 analog.

RESULTS

Here, we present the biologically active [Ser3,7,12,16]-RTD-2 analog that selectively targets various types of breast cancer cells. Immunoprecipitation protein-protein interaction studies showed eleven proteins common to MDA-MB-231 and T47D cell lines. Taking into account their cellular location, it can be concluded that the synthesized peptide interacts mainly with nuclear proteins, which correlates with the obtained microscopic image.

CONCLUSION

Proteins that interact strongly with the [Ser3,7,12,16]-RTD-2 analog are closely related to the proteasomal protein degradation pathway. As the activity of the ubiquitin-proteasome system is markedly increased in patients with breast cancer, it is likely that selective modulation of this system may be a useful method for breast cancer treatment.

Analysis of urinary kallikrein-related peptidase 13 for monitoring bladder cancer

BACKGROUND

Bladder cancer (BC) is one of the 10 most common types of cancer worldwide, with approximately 550,000 new cases each year. Early detection and appropriate diagnosis are important factors in successful treatment of the disease.

MATERIAL AND METHODS

We used specific fluorogenic substrate for the quantitative determination of urine kallikrein 13 (KLK13) activity in healthy (n = 15) and BC (n = 54) patients. The proteolytic activity in individual urine samples was determined by fluorescence measurements. Then, immunoenzymatic analyses (ELISA, Western blot) were performed to confirm the presence of KLK13 in the tested samples.

RESULTS

Urine samples from patients with G2 and G3 grade BC contained proteolytically active KLK13, as confirmed by kinetic analysis and immunochemical detection. KLK13 was not detected in the urine of patients with G1 grade BC.

DISCUSSION

Previous clinical study reveals the KLK13 significance for BC prognosis as increased KLK13 expression was highlighted in bladder tumours compared to normal adjacent tissues. Our findings correlate to the report. KLK13 activity was confirmed in BC patients with G2 and G3 stage of disease development.

CONCLUSIONS

Using specific chromogenic/fluorogenic peptides could be useful for the non-invasive disease monitoring of BC progress.

SP-1, a Serine Protease from the Gut Microbiota, Influences Colitis and Drives Intestinal Dysbiosis in Mice

Increased protease activity has been linked to the pathogenesis of IBD. While most studies have been focusing on host proteases in gut inflammation, it remains unclear how to address the potential contribution of their bacterial counterparts. In the present study, we report a functional characterization of a newly identified serine protease, SP-1, from the human gut microbiota. The serine protease repertoire of gut Clostridium was first explored, and the specificity of SP-1 was analyzed using a combinatorial chemistry method. Combining in vitro analyses and a mouse model of colitis, we show that oral administration of recombinant bacteria secreting SP-1 (i) compromises the epithelial barrier, (ii) alters the microbial community, and (ii) exacerbates colitis. These findings suggest that gut microbial protease activity may constitute a valuable contributor to IBD and could, therefore, represent a promising target for the treatment of the disease.

Elastolytic activity is associated with inflammation in bladder cancer

Cancer development and progression is often associated with inflammation. Late diagnosis of inflammation that directly leads to the development of neoplasm - cancer is associated with a reduction in the chance of successful treatment or is associated with therapeutic difficulties. A panel of chromogenic substrates was used for the qualitative determination of specific activity of enzymes in urine of patients with confirmed inflammatory reaction and/or epithelial neoplasms in particular tumors at various stages of development. Urine of people with excluded inflammation was used as a control group. Proteolytic activity was determined in urine samples collected from patients with epithelial neoplasms and/or inflammation. What is more, we determine human neutrophil elastase (HNE) activity related inflammation based on the examination of urine samples. We suspect that the proteolytical activity of urine samples is due to neutrophil response to inflammation, which is directly related to cancer. This is the first study to determine elastolytic activity in bladder cancer urine samples. It supports wider use of urine for inflammation screening.

Lipidation of Temporin-1CEb Derivatives as a Tool for Activity Improvement, Pros and Cons of the Approach

The alarming raise of multi-drug resistance among human microbial pathogens makes the development of novel therapeutics a priority task. In contrast to conventional antibiotics, antimicrobial peptides (AMPs), besides evoking a broad spectrum of activity against microorganisms, could offer additional benefits, such as the ability to neutralize toxins, modulate inflammatory response, eradicate bacterial and fungal biofilms or prevent their development. The latter properties are of special interest, as most antibiotics available on the market have limited ability to diffuse through rigid structures of biofilms. Lipidation of AMPs is considered as an effective approach for enhancement of their antimicrobial potential and in vivo stability; however, it could also have undesired impact on selectivity, solubility or the aggregation state of the modified peptides. In the present work, we describe the results of structural modifications of compounds designed based on cationic antimicrobial peptides DK5 and CAR-PEG-DK5, derivatized at their N-terminal part with fatty acids with different lengths of carbon chain. The proposed modifications substantially improved antimicrobial properties of the final compounds and their effectiveness in inhibition of biofilm development as well as eradication of pre-formed 24 h old biofilms of Candida albicans and Staphylococcus aureus. The most active compounds (C5-DK5, C12-DK5 and C12-CAR-PEG-DK5) were also potent against multi-drug resistant Staphylococcus aureus USA300 strain and clinical isolates of Pseudomonas aeruginosa. Both experimental and in silico methods revealed strong correlation between the length of fatty acid attached to the peptides and their final membranolytic properties, tendency to self-assemble and cytotoxicity.

Gut Serpinome: Emerging Evidence in IBD

Inflammatory bowel diseases (IBD) are incurable disorders whose prevalence and global socioeconomic impact are increasing. While the role of host genetics and immunity is well documented, that of gut microbiota dysbiosis is increasingly being studied. However, the molecular basis of the dialogue between the gut microbiota and the host remains poorly understood. Increased activity of serine proteases is demonstrated in IBD patients and may contribute to the onset and the maintenance of the disease. The intestinal proteolytic balance is the result of an equilibrium between the proteases and their corresponding inhibitors. Interestingly, the serine protease inhibitors (serpins) encoded by the host are well reported; in contrast, those from the gut microbiota remain poorly studied. In this review, we provide a concise analysis of the roles of serine protease in IBD physiopathology and we focus on the serpins from the gut microbiota (gut serpinome) and their relevance as a promising therapeutic approach.

Proteinase release from activated neutrophils in mechanically ventilated patients with non-COVID-19 and COVID-19 pneumonia

Severe cases of pneumonia are frequently associated with acute respiratory distress syndrome (ARDS), which carries a mortality rate of about 40% [1]. Uncontrolled host inflammatory response in the lung is a key factor in the transition from pneumonia to ARDS, with alveolocapillary membrane disruption leading to interstitial and alveolar oedema [2]. Neutrophils are part of the innate immune system and are the first responders to local tissue damage and infection. Recruited neutrophils are considered important actors in lung tissue injury [3]. Indeed, their broad arsenal of antimicrobial weaponry can cause direct and indirect collateral damage. Neutrophil serine proteinases (NSPs), including elastase (NE), proteinase 3 (PR3) and cathepsin G (CatG), are released from activated cells and play a part in ARDS pathophysiology, as illustrated in both preclinical and clinical studies [4]. Thus, NSPs emerge as an untapped point for therapeutic interventions in pneumonia-induced ARDS [4]. These NSPs are readily synthesised in neutrophil precursors within the bone marrow and are converted into their active form by cathepsin C (CatC) [5]. They are stored together in cytoplasmic granules and secreted into the extracellular compartment upon stimulation [6].

COVID-19 ARDS is associated with release of biologically active neutrophil elastase-related proteinases to the airways and blood at a comparable level to non-COVID ARDShttps://bit.ly/3nihveh

Digestive Inflammation: Role of Proteolytic Dysregulation

Dysregulation of the proteolytic balance is often associated with diseases. Serine proteases and matrix metalloproteases are involved in a multitude of biological processes and notably in the inflammatory response. Within the framework of digestive inflammation, several studies have stressed the role of serine proteases and matrix metalloproteases (MMPs) as key actors in its pathogenesis and pointed to the unbalance between these proteases and their respective inhibitors. Substantial efforts have been made in developing new inhibitors, some of which have reached clinical trial phases, notwithstanding that unwanted side effects remain a major issue. However, studies on the proteolytic imbalance and inhibitors conception are directed toward host serine/MMPs proteases revealing a hitherto overlooked factor, the potential contribution of their bacterial counterpart. In this review, we highlight the role of proteolytic imbalance in human digestive inflammation focusing on serine proteases and MMPs and their respective inhibitors considering both host and bacterial origin.

Lung Protection by Cathepsin C Inhibition: A New Hope for COVID-19 and ARDS?

Cathepsin C (CatC) is a cysteine dipeptidyl aminopeptidase that activates most of tissue-degrading elastase-related serine proteases. Thus, CatC appears as a potential therapeutic target to impair protease-driven tissue degradation in chronic inflammatory and autoimmune diseases. A depletion of proinflammatory elastase-related proteases in neutrophils is observed in patients with CatC deficiency (Papillon-Lefèvre syndrome). To address and counterbalance unwanted effects of elastase-related proteases, chemical inhibitors of CatC are being evaluated in preclinical and clinical trials. Neutrophils may contribute to the diffuse alveolar inflammation seen in acute respiratory distress syndrome (ARDS) which is currently a growing challenge for intensive care units due to the outbreak of the COVID-19 pandemic. Elimination of elastase-related neutrophil proteases may reduce the progression of lung injury in these patients. Pharmacological CatC inhibition could be a potential therapeutic strategy to prevent the irreversible pulmonary failure threatening the life of COVID-19 patients.

Kallikrein 13 serves as a priming protease during infection by the human coronavirus HKU1

Unlike SARS-CoV-2, the human coronavirus HKU1 normally causes relatively mild respiratory tract infections; however, it shares with SARS-CoV-2 the mechanism of using its surface spike (S) protein to enter target cells. Because the host receptor for HCoV-HKU1 is unknown, efforts to study the virus in cell culture systems have proved difficult. Milewska et al. found that knockout of the protease kallikrein 13 (KLK13) in human airway epithelial cells blocked their infection by HCoV-HKU1, that overexpression of KLK13 in nonpermissive cells enabled their infection by the virus, and that KLK13 cleaved the viral S protein. Together, these findings suggest that KLK13 is a priming enzyme for viral entry and may help to establish cell lines that can facilitate further investigation of the mechanism of viral pathogenesis.

Human coronavirus HKU1 (HCoV-HKU1) is associated with respiratory disease and is prevalent worldwide, but an in vitro model for viral replication is lacking. An interaction between the coronaviral spike (S) protein and its receptor is the primary determinant of tissue and host specificity; however, viral entry is a complex process requiring the concerted action of multiple cellular elements. Here, we found that the protease kallikrein 13 (KLK13) was required for the infection of human respiratory epithelial cells and was sufficient to mediate the entry of HCoV-HKU1 into nonpermissive RD cells. We also demonstrated the cleavage of the HCoV-HKU1 S protein by KLK13 in the S1/S2 region, suggesting that KLK13 is the priming enzyme for this virus. Together, these data suggest that protease distribution and specificity determine the tissue and cell specificity of the virus and may also regulate interspecies transmission.

Myeloperoxidase Modulates Inflammation in Generalized Pustular Psoriasis and Additional Rare Pustular Skin Diseases

Generalized pustular psoriasis (GPP) is a severe multi-systemic inflammatory disease characterized by neutrophilic pustulosis and triggered by pro-inflammatory IL-36 cytokines in skin. While 19%–41% of affected individuals harbor bi-allelic mutations in IL36RN, the genetic cause is not known in most cases. To identify and characterize new pathways involved in the pathogenesis of GPP, we performed whole-exome sequencing in 31 individuals with GPP and demonstrated effects of mutations in MPO encoding the neutrophilic enzyme myeloperoxidase (MPO). We discovered eight MPO mutations resulting in MPO -deficiency in neutrophils and monocytes. MPO mutations, primarily those resulting in complete MPO deficiency, cumulatively associated with GPP (p = 1.85E−08; OR = 6.47). The number of mutant MPO alleles significantly differed between 82 affected individuals and >4,900 control subjects (p = 1.04E−09); this effect was stronger when including IL36RN mutations (1.48E−13) and correlated with a younger age of onset (p = 0.0018). The activity of four proteases, previously implicated as activating enzymes of IL-36 precursors, correlated with MPO deficiency. Phorbol-myristate-acetate-induced formation of neutrophil extracellular traps (NETs) was reduced in affected cells (p = 0.015), and phagocytosis assays in MPO-deficient mice and human cells revealed altered neutrophil function and impaired clearance of neutrophils by monocytes (efferocytosis) allowing prolonged neutrophil persistence in inflammatory skin. MPO mutations contribute significantly to GPP’s pathogenesis. We implicate MPO as an inflammatory modulator in humans that regulates protease activity and NET formation and modifies efferocytosis. Our findings indicate possible implications for the application of MPO inhibitors in cardiovascular diseases. MPO and affected pathways represent attractive targets for inducing resolution of inflammation in neutrophil-mediated skin diseases.

Activity-based protein profiling guided identification of urine proteinase 3 activity in subclinical rejection after renal transplantation

Background

The pathophysiology of subclinical versus clinical rejection remains incompletely understood given their equivalent histological severity but discordant graft function. The goal was to evaluate serine hydrolase enzyme activities to explore if there were any underlying differences in activities during subclinical versus clinical rejection.

Methods

Serine hydrolase activity-based protein profiling (ABPP) was performed on the urines of a case control cohort of patients with biopsy confirmed subclinical or clinical transplant rejection. In-gel analysis and affinity purification with mass spectrometry were used to demonstrate and identify active serine hydrolase activity. An assay for proteinase 3 (PR3/PRTN3) was adapted for the quantitation of activity in urine.

Results

In-gel ABPP profiles suggested increased intensity and diversity of serine hydrolase activities in urine from patients undergoing subclinical versus clinical rejection. Serine hydrolases (n = 30) were identified by mass spectrometry in subclinical and clinical rejection patients with 4 non-overlapping candidates between the two groups (i.e. ABHD14B, LTF, PR3/PRTN3 and PRSS12). Western blot and the use of a specific inhibitor confirmed the presence of active PR3/PRTN3 in samples from patients undergoing subclinical rejection. Analysis of samples from normal donors or from several serial post-transplant urines indicated that although PR3/PRTN3 activity may be highly associated with low-grade subclinical inflammation, the enzyme activity was not restricted to this patient group.

Conclusions

There appear to be limited qualitative and quantitative differences in serine hydrolase activity in patients with subclinical versus clinical renal transplant rejection. The majority of enzymes identified were present in samples from both groups implying that in-gel quantitative differences may largely relate to the activity status of shared enzymes. However qualitative compositional differences were also observed indicating differential activities. The PR3/PRTN3 analyses indicate that the activity status of urine in transplant patients is dynamic possibly reflecting changes in the underlying processes in the transplant. These data suggest that differential serine hydrolase pathways may be active in subclinical versus clinical rejection which requires further exploration in larger patient cohorts. Although this study focused on PR3/PRTN3, this does not preclude the possibility that other enzymes may play critical roles in the rejection process.

Cathepsin C is a novel mediator of podocyte and renal injury induced by hyperglycemia

A growing body of evidence suggests a role of proteolytic enzymes in the development of diabetic nephropathy. Cathepsin C (CatC) is a well-known regulator of inflammatory responses, but its involvement in podocyte and renal injury remains obscure. We used Zucker rats, a genetic model of metabolic syndrome and insulin resistance, to determine the presence, quantity, and activity of CatC in the urine. In addition to the animal study, we used two cellular models, immortalized human podocytes and primary rat podocytes, to determine mRNA and protein expression levels via RT-PCR, Western blot, and confocal microscopy, and to evaluate CatC activity. The role of CatC was analyzed in CatC-depleted podocytes using siRNA and glycolytic flux parameters were obtained from extracellular acidification rate (ECAR) measurements. In functional analyses, podocyte and glomerular permeability to albumin was determined. We found that podocytes express and secrete CatC, and a hyperglycemic environment increases CatC levels and activity. Both high glucose and non-specific activator of CatC phorbol 12-myristate 13-acetate (PMA) diminished nephrin, cofilin, and GLUT4 levels and induced cytoskeletal rearrangements, increasing albumin permeability in podocytes. These negative effects were completely reversed in CatC-depleted podocytes. Moreover, PMA, but not high glucose, increased glycolytic flux in podocytes. Finally, we demonstrated that CatC expression and activity are increased in the urine of diabetic Zucker rats. We propose a novel mechanism of podocyte injury in diabetes, providing deeper insight into the role of CatC in podocyte biology.

A Peptidomimetic Fluorescent Probe to Detect the Trypsin β2 Subunit of the Human 20S Proteasome

This work describes the chemical synthesis, combinatorial selection, and enzymatic evaluation of peptidomimetic fluorescent substrates specific for the trypsin-like (β2) subunit of the 20S human proteasome. After deconvolution of a library comprising nearly 6000 compounds composed of peg substituted diaminopropionic acid DAPEG building blocks, the sequence ABZ–Dap(O2(Cbz))–Dap(GO1)–Dap(O2(Cbz))–Arg–ANB–NH₂, where ABZ is 2-aminobenzoic acid, and ANB- 5 amino 2- nitro benzoic acid was selected. Its cleavage followed sigmoidal kinetics, characteristic for allosteric enzymes, with K_m = 3.22 ± 0.02 μM, k_cat = 245 s⁻¹, and k_cat/K_m = 7.61 × 10⁷ M⁻¹ s⁻¹. This process was practically halted when a selective inhibitor of the β2 subunit of the 20S human proteasome was supplemented to the reaction system. Titration of the substrate resulting in decreased amounts of proteasome 20S produced a linear signal up to 10⁻¹¹ M. Using this substrate, we detected human proteasome 20S in human urine samples taken from the bladders of cancer patients. This observation could be useful for the noninvasive diagnosis of this severe disease.

Human proteinase 3 resistance to inhibition extends to alpha-2 macroglobulin

Polymorphonuclear neutrophils contain at least four serine endopeptidases, namely neutrophil elastase (NE), proteinase 3 (PR3), cathepsin G (CatG), and NSP4, which contribute to the regulation of infection and of inflammatory processes. In physiological conditions, endogenous inhibitors including α2-macroglobulin (α2-M), serpins [α1-proteinase inhibitor (α1-PI)], monocyte neutrophil elastase inhibitor (MNEI), α1-antichymotrypsin, and locally produced chelonianins (elafin, SLPI) control excessive proteolytic activity of neutrophilic serine proteinases. In contrast to human NE (hNE), hPR3 is weakly inhibited by α1-PI and MNEI but not by SLPI. α2-M is a large spectrum inhibitor that traps a variety of proteinases in response to cleavage(s) in its bait region. We report here that α2-M was more rapidly processed by hNE than hPR3 or hCatG. This was confirmed by the observation that the association between α2-M and hPR3 is governed by a k_ass in the ≤ 10⁵  m^-1 ·s^-1 range. Since α2-M-trapped proteinases retain peptidase activity, we first predicted the putative cleavage sites within the α2-M bait region (residues 690-728) using kinetic and molecular modeling approaches. We then identified by mass spectrum analysis the cleavage sites of hPR3 in a synthetic peptide spanning the 39-residue bait region of α2-M (39pep-α2-M). Since the 39pep-α2-M peptide and the corresponding bait area in the whole protein do not contain sequences with a high probability of specific cleavage by hPR3 and were indeed only slowly cleaved by hPR3, it can be concluded that α2-M is a poor inhibitor of hPR3. The resistance of hPR3 to inhibition by endogenous inhibitors explains at least in part its role in tissue injury during chronic inflammatory diseases and its well-recognized function of major target autoantigen in granulomatosis with polyangiitis.

Fecal Serine Protease Profiling in Inflammatory Bowel Diseases

Serine proteases are extensively known to play key roles in many physiological processes. However, their dysregulation is often associated to several diseases including inflammatory bowel diseases (IBD). Here, we used specific substrates to monitor fecal protease activities in a large cohort of healthy and IBD patients. Of interest, serine protease activity was 10-fold higher in IBD fecal samples compared to healthy controls. Moreover, functional analysis of these fecal proteolytic activities revealed that the most increased activities are trypsin-like, elastase-like and cathepsin G-like. We also show for the first time, an increase of proteinase 3-like activity in these samples compared to controls. Results presented here will guide further investigations to better understand the relevance of these peptidases in IBD.

The molecular function of kallikrein-related peptidase 14 demonstrates a key modulatory role in advanced prostate cancer

Kallikrein-related peptidase 14 (KLK14) is one of the several secreted KLK serine proteases involved in prostate cancer (PCa) pathogenesis. While relatively understudied, recent reports have identified KLK14 as overexpressed during PCa development. However, the modulation of KLK14 expression during PCa progression and the molecular and biological functions of this protease in the prostate tumor microenvironment remain unknown. To determine the modulation of KLK14 expression during PCa progression, we analyzed the expression levels of KLK14 in patient samples using publicly available databases and immunohistochemistry. In order to delineate the molecular mechanisms involving KLK14 in PCa progression, we integrated proteomic, transcriptomic, and in vitro assays with the goal to identify substrates, related-signaling pathways, and functional roles of this protease. We showed that KLK14 expression is elevated in advanced PCa, and particularly in metastasis. Additionally, KLK14 levels were found to be decreased in PCa tissues from patients responsive to neoadjuvant therapy compared to untreated patients. Furthermore, we also identified that KLK14 expression reoccurred in patients who developed castrate-resistant PCa. The combination of proteomic and transcriptomic analysis as well as functional assays revealed several new KLK14 substrates (agrin, desmoglein 2, vitronectin, laminins) and KLK14-regulated genes (Interleukin 32, midkine, SRY-Box 9), particularly an involvement of the mitogen-activated protein kinase 1 and interleukin 1 receptor pathways, and an involvement of KLK14 in the regulation of cellular migration, supporting its involvement in aggressive features of PCa progression. In conclusion, our work showed that KLK14 expression is associated with the development of aggressive PCa suggesting that targeting this protease could offer a novel route to limit the progression of prostate tumors. Additional work is necessary to determine the benefits and implications of targeting/cotargeting KLK14 in PCa as well as to determine the potential use of KLK14 expression as a predictor of PCa aggressiveness or response to treatment.

The Bactericidal Activity of Temporin Analogues Against Methicillin Resistant Staphylococcus aureus

Staphylococcus aureus is a major infectious agent responsible for a plethora of superficial skin infections and systemic diseases, including endocarditis and septic arthritis. Recent epidemiological data revealed the emergence of resistance to commonly used antibiotics, including increased numbers of both hospital- and community-acquired methicillin-resistant S. aureus (MRSA). Due to their potent antimicrobial functions, low potential to develop resistance, and immunogenicity, antimicrobial peptides (AMPs) are a promising alternative treatment for multidrug-resistant strains. Here, we examined the activity of a lysine-rich derivative of amphibian temporin-1CEb (DK5) conjugated to peptides that exert pro-proliferative and/or cytoprotective activity. Analysis of a library of synthetic peptides to identify those with antibacterial potential revealed that the most potent agent against multidrug-resistant S. aureus was a conjugate of a temporin analogue with the synthetic Leu-enkephalin analogue dalargin (DAL). DAL-PEG-DK5 exerted direct bactericidal effects via bacterial membrane disruption, leading to eradication of both planktonic and biofilm-associated staphylococci. Finally, we showed that accumulation of the peptide in the cytoplasm of human keratinocytes led to a marked clearance of intracellular MRSA, resulting in cytoprotection against invading bacteria. Collectively, the data showed that DAL-PEG-DK5 might be a potent antimicrobial agent for treatment of staphylococcal skin infections.

Properties of the HtrA Protease From Bacterium Helicobacter pylori Whose Activity Is Indispensable for Growth Under Stress Conditions

The protease high temperature requirement A from the gastric pathogen Helicobacter pylori (HtrA_Hp) belongs to the well conserved family of serine proteases. HtrA_Hp is an important secreted virulence factor involved in the disruption of tight and adherens junctions during infection. Very little is known about the function of HtrA_Hp in the H. pylori cell physiology due to the lack of htrA knockout strains. Here, using a newly constructed ΔhtrA mutant strain, we found that bacteria deprived of HtrA_Hp showed increased sensitivity to certain types of stress, including elevated temperature, pH and osmotic shock, as well as treatment with puromycin. These data indicate that HtrA_Hp plays a protective role in the H. pylori cell, presumably associated with maintenance of important periplasmic and outer membrane proteins. Purified HtrA_Hp was shown to be very tolerant to a wide range of temperature and pH values. Remarkably, the protein exhibited a very high thermal stability with the melting point (T_m) values of above 85°C. Moreover, HtrA_Hp showed the capability to regain its active structure following treatment under denaturing conditions. Taken together, our work demonstrates that HtrA_Hp is well adapted to operate under harsh conditions as an exported virulence factor, but also inside the bacterial cell as an important component of the protein quality control system in the stressed cellular envelope.

Structure-based design and in vivo anti-arthritic activity evaluation of a potent dipeptidyl cyclopropyl nitrile inhibitor of cathepsin C

Cathepsin C (CatC) is a dipeptidyl-exopeptidase which activates neutrophil serine protease precursors (elastase, proteinase 3, cathepsin G and NSP4) by removing their N-terminal propeptide in bone marrow cells at the promyelocytic stage of neutrophil differentiation. The resulting active proteases are implicated in chronic inflammatory and autoimmune diseases. Hence, inhibition of CatC represents a therapeutic strategy to suppress excessive protease activities in various neutrophil mediated diseases. We designed and synthesized a series of dipeptidyl cyclopropyl nitrile compounds as putative CatC inhibitors. One compound, IcatC_XPZ-01 ((S)-2-amino-N-((1R,2R)-1-cyano-2-(4'-(4-methylpiperazin-1-ylsulfonyl)biphenyl-4-yl)cyclopropyl)butanamide)) was identified as a potent inhibitor of both human and rodent CatC. In mice, pharmacokinetic studies revealed that IcatC_XPZ-01 accumulated in the bone marrow reaching levels suitable for CatC inhibition. Subcutaneous administration of IcatC_XPZ-01 in a monoclonal anti-collagen antibody induced mouse model of rheumatoid arthritis resulted in statistically significant anti-arthritic activity with persistent decrease in arthritis scores and paw thickness.

Conjugate of Enkephalin and Temporin Peptides as a Novel Therapeutic Agent for Sepsis

Antimicrobial peptides (AMPs) exhibit a wide spectrum of actions, ranging from a direct bactericidal effect to multifunctional activities as immune effector molecules. The aim of this study was to examine the anti-inflammatory properties of a DAL-PEG-DK5 conjugate composed of a lysine-rich derivative of amphibian temporin-1CEb (DK5) and dalargin (DAL), the synthetic Leu-enkephalin analogue. Detailed study of the endotoxin-neutralizing activity of the peptide revealed that DAL-PEG-DK5 interacts with LPS and the LPS binding protein (LBP). Moreover, DAL-PEG-DK5 prevented dimerization of TLR4 at the macrophage surface upon LPS stimulation. This inhibited activation of the NF-κB signaling pathway and markedly reduced pro-inflammatory cytokine production. Finally, we showed that aggregation of DAL-PEG-DK5 into amyloid-like structures induced by LPS neutralized the endotoxin proinflammatory activity. Consequently, DAL-PEG-DK5 reduced morbidity and mortality in vivo, in a mouse model of endotoxin-induced septic shock. Collectively, the data suggest that DAL-PEG-DK5 is a promising therapeutic compound for sepsis.

One Step Beyond: Design of Substrates Spanning Primed Positions of Zika Virus NS2B-NS3 Protease

Although the mosquito-borne Zika virus was discovered in the late 1940s of the 20th century, for years it was neglected, as the disease in humans was rare and relatively mild. Viral NS2B-NS3 protease is essential for virus replication, and except for maturation of viral proteins, it also modulates the infection microenvironment to facilitate virus invasion. Here, we report the combinatorial chemistry approach for the synthesis of internally quenched substrates of the Zika virus NS2B-NS3 protease that were optimized in prime positions of the peptide chain. Final substrate ABZ-Val-Lys-Lys-Arg-Ala-Ala-Trp-Tyr(3-NO₂)-NH₂ displays an excellent kinetic parameter (k _cat/K _M reaching nearly 1.26 × 10⁸ M^-1 × s^-1), which is over 10 times greater than previously reported (7.7 × 10⁶ M^-1 × s^-1) substrate. Moreover, it was found to be selective over West Nile virus protease.

Aggregated neutrophil extracellular traps resolve inflammation by proteolysis of cytokines and chemokines and protection from antiproteases

Papillon-Lefèvre syndrome (PLS) is characterized by nonfunctional neutrophil serine proteases (NSPs) and fulminant periodontal inflammation of unknown cause. Here we investigated neutrophil extracellular trap (NET)-associated aggregation and cytokine/chemokine-release/degradation by normal and NSP-deficient human and mouse granulocytes. Stimulated with solid or soluble NET inducers, normal neutrophils formed aggregates and both released and degraded cytokines/chemokines. With increasing cell density, proteolytic degradation outweighed release. Maximum output of cytokines/chemokines occurred mostly at densities between 2 × 10⁷ and 4 × 10⁷ neutrophils/cm³. Assessment of neutrophil density in vivo showed that these concentrations are surpassed during inflammation. Association with aggregated NETs conferred protection of neutrophil elastase against α1-antitrypsin. In contrast, eosinophils did not influence cytokine/chemokine concentrations. The proteolytic degradation of inflammatory mediators seen in NETs was abrogated in Papillon-Lefèvre syndrome (PLS) neutrophils. In summary, neutrophil-driven proteolysis of inflammatory mediators works as a built-in safeguard for inflammation. The absence of this negative feedback mechanism might be responsible for the nonresolving periodontitis seen in PLS.-Hahn, J., Schauer, C., Czegley, C., Kling, L., Petru, L., Schmid, B., Weidner, D., Reinwald, C., Biermann, M. H. C., Blunder, S., Ernst, J., Lesner, A., Bäuerle, T., Palmisano, R., Christiansen, S., Herrmann, M., Bozec, A., Gruber, R., Schett, G., Hoffmann, M. H. Aggregated neutrophil extracellular traps resolve inflammation by proteolysis of cytokines and chemokines and protection from antiproteases.

Consequences of cathepsin C inactivation for membrane exposure of proteinase 3, the target antigen in autoimmune vasculitis

Membrane-bound proteinase 3 (PR3^m) is the main target antigen of anti-neutrophil cytoplasmic autoantibodies (ANCA) in granulomatosis with polyangiitis, a systemic small-vessel vasculitis. Binding of ANCA to PR3^m triggers neutrophil activation with the secretion of enzymatically active PR3 and related neutrophil serine proteases, thereby contributing to vascular damage. PR3 and related proteases are activated from pro-forms by the lysosomal cysteine protease cathepsin C (CatC) during neutrophil maturation. We hypothesized that pharmacological inhibition of CatC provides an effective measure to reduce PR3^m and therefore has implications as a novel therapeutic approach in granulomatosis with polyangiitis. We first studied neutrophilic PR3 from 24 patients with Papillon-Lefèvre syndrome (PLS), a genetic form of CatC deficiency. PLS neutrophil lysates showed a largely reduced but still detectable (0.5-4%) PR3 activity when compared with healthy control cells. Despite extremely low levels of cellular PR3, the amount of constitutive PR3^m expressed on the surface of quiescent neutrophils and the typical bimodal membrane distribution pattern were similar to what was observed in healthy neutrophils. However, following cell activation, there was no significant increase in the total amount of PR3^m on PLS neutrophils, whereas the total amount of PR3^m on healthy neutrophils was significantly increased. We then explored the effect of pharmacological CatC inhibition on PR3 stability in normal neutrophils using a potent cell-permeable CatC inhibitor and a CD34⁺ hematopoietic stem cell model. Human CD34⁺ hematopoietic stem cells were treated with the inhibitor during neutrophil differentiation over 10 days. We observed strong reductions in PR3^m, cellular PR3 protein, and proteolytic PR3 activity, whereas neutrophil differentiation was not compromised.

Exploiting the S4-S5 Specificity of Human Neutrophil Proteinase 3 to Improve the Potency of Peptidyl Di(chlorophenyl)-phosphonate Ester Inhibitors: A Kinetic and Molecular Modeling Analysis

The neutrophilic serine protease proteinase 3 (PR3) is involved in inflammation and immune response and thus appears as a therapeutic target for a variety of infectious and inflammatory diseases. Here we combined kinetic and molecular docking studies to increase the potency of peptidyl-diphenyl phosphonate PR3 inhibitors. Occupancy of the S1 subsite of PR3 by a nVal residue and of the S4-S5 subsites by a biotinylated Val residue as obtained in biotin-VYDnV^P(O-C₆H₄-4-Cl)₂ enhanced the second-order inhibition constant k_obs/[I] toward PR3 by more than 10 times ( k_obs/[I] = 73000 ± 5000 M^-1 s^-1) as compared to the best phosphonate PR3 inhibitor previously reported. This inhibitor shows no significant inhibitory activity toward human neutrophil elastase and resists proteolytic degradation in sputa from cystic fibrosis patients. It also inhibits macaque PR3 but not the PR3 from rodents and can thus be used for in vivo assays in a primate model of inflammation.

A Novel Biological Role for Peptidyl-Arginine Deiminases: Citrullination of Cathelicidin LL-37 Controls the Immunostimulatory Potential of Cell-Free DNA

LL-37, the only human cathelicidin that is released during inflammation, is a potent regulator of immune responses by facilitating delivery of oligonucleotides to intracellular TLR-9, thereby enhancing the response of human plasmacytoid dendritic cells (pDCs) to extracellular DNA. Although important for pathogen recognition, this mechanism may facilitate development of autoimmune diseases. In this article, we show that citrullination of LL-37 by peptidyl-arginine deiminases (PADs) hindered peptide-dependent DNA uptake and sensing by pDCs. In contrast, carbamylation of the peptide (homocitrullination of Lys residues) had no effect. The efficiency of LL-37 binding to oligonucleotides and activation of pDCs was found to be inversely proportional to the number of citrullinated residues in the peptide. Similarly, preincubation of carbamylated LL-37 with PAD2 abrogated the peptide's ability to bind DNA. Conversely, LL-37 with Arg residues substituted by homoarginine, which cannot be deiminated, elicited full activity of native LL-37 regardless of PAD2 treatment. Taken together, the data showed that citrullination abolished LL-37 ability to bind DNA and altered the immunomodulatory function of the peptide. Both activities were dependent on the proper distribution of guanidinium side chains in the native peptide sequence. Moreover, our data suggest that cathelicidin/LL-37 is citrullinated by PADs during NET formation, thus affecting the inflammatory potential of NETs. Together this may represent a novel mechanism for preventing the breakdown of immunotolerance, which is dependent on the response of APCs to self-molecules (including cell-free DNA); overactivation may facilitate development of autoimmunity.

Biochemical properties of the HtrA homolog from bacterium Stenotrophomonas maltophilia

The HtrA proteins due to their proteolytic, and in many cases chaperone activity, efficiently counteract consequences of stressful conditions. In the environmental bacterium and nosocomial pathogen Stenotrophomonas maltophilia HtrA (HtrA_Sm) is induced as a part of adaptive response to host temperature (37°C). We examined the biochemical properties of HtrA_Sm and compared them with those of model HtrA_Ec from Escherichia coli. We found that HtrA_Sm is a protease and chaperone that operates over a wide range of pH and is highly active at temperatures between 35 and 37°C. The temperature-sensitive activity corresponded well with the lower thermal stability of the protein and weaker stability of the oligomer. Interestingly, the enzyme shows slightly different substrate cleavage specificity when compared to other bacterial HtrAs. A computational model of the three-dimensional structure of HtrA_Sm indicates differences in the S1 substrate specificity pocket and suggests weaker inter-trimer interactions when compared to HtrA_Ec. The observed features of HtrA_Sm suggest that this protein may play a protective role under stressful conditions acting both as a protease and a chaperone. The optimal temperatures for the protein activity may reflect the evolutionary adaptation of S. maltophilia to life in soil or aqueous environments, where the temperatures are usually much below 37°C.

Selection of Effective HTRA3 Activators Using Combinatorial Chemistry

Herein, we report selection, synthesis, and enzymatic evaluation of a peptidomimetic library able to increase proteolytic activity of HtrA3 (high temperature requirement A) protease. Iterative deconvolution in solution of synthesized modified pentapeptides yielded two potent HtrA3 activators acting in the micromolar range (HCOO-CH₂O-C₆H₄-OCH₂-CO-Tyr-Asn-Phe-His-Asn-OH and HCOO-CH₂O-C₆H₄-OCH₂-CO-Tyr-Asn-Phe-His-Glu-OH). Both compounds increased proteolysis of an artificial HtrA3 substrate over 40-fold in a selective manner. On the basis of molecular modeling, the selected compounds bind strongly to the PDZ domain.

Inhibitors and Antibody Fragments as Potential Anti-Inflammatory Therapeutics Targeting Neutrophil Proteinase 3 in Human Disease

Proteinase 3 (PR3) has received great scientific attention after its identification as the essential antigenic target of antineutrophil cytoplasm antibodies in Wegener's granulomatosis (now called granulomatosis with polyangiitis). Despite many structural and functional similarities between neutrophil elastase (NE) and PR3 during biosynthesis, storage, and extracellular release, unique properties and pathobiological functions have emerged from detailed studies in recent years. The development of highly sensitive substrates and inhibitors of human PR3 and the creation of PR3-selective single knockout mice led to the identification of nonredundant roles of PR3 in cell death induction via procaspase-3 activation in cell cultures and in mouse models. According to a study in knockout mice, PR3 shortens the lifespan of infiltrating neutrophils in tissues and accelerates the clearance of aged neutrophils in mice. Membrane exposure of active human PR3 on apoptotic neutrophils reprograms the response of macrophages to phagocytosed neutrophils, triggers secretion of proinflammatory cytokines, and undermines immune silencing and tissue regeneration. PR3-induced disruption of the anti-inflammatory effect of efferocytosis may be relevant for not only granulomatosis with polyangiitis but also for other autoimmune diseases with high neutrophil turnover. Inhibition of membrane-bound PR3 by endogenous inhibitors such as the α-1-protease inhibitor is comparatively weaker than that of NE, suggesting that the adverse effects of unopposed PR3 activity resurface earlier than those of NE in individuals with α-1-protease inhibitor deficiency. Effective coverage of PR3 by anti-inflammatory tools and simultaneous inhibition of both PR3 and NE should be most promising in the future.

Prolonged pharmacological inhibition of cathepsin C results in elimination of neutrophil serine proteases

Cathepsin C (CatC) is a tetrameric cysteine dipeptidyl aminopeptidase that plays a key role in activation of pro-inflammatory serine protease zymogens by removal of a N-terminal pro-dipeptide sequence. Loss of function mutations in the CatC gene is associated with lack of immune cell serine protease activities and cause Papillon-Lefèvre syndrome (PLS). Also, only very low levels of elastase-like protease zymogens are detected by proteome analysis of neutrophils from PLS patients. Thus, CatC inhibitors represent new alternatives for the treatment of neutrophil protease-driven inflammatory or autoimmune diseases. We aimed to experimentally inactivate and lower neutrophil elastase-like proteases by pharmacological blocking of CatC-dependent maturation in cell-based assays and in vivo. Isolated, immature bone marrow cells from healthy donors pulse-chased in the presence of a new cell permeable cyclopropyl nitrile CatC inhibitor almost totally lack elastase. We confirmed the elimination of neutrophil elastase-like proteases by prolonged inhibition of CatC in a non-human primate. We also showed that neutrophils lacking elastase-like protease activities were still recruited to inflammatory sites. These preclinical results demonstrate that the disappearance of neutrophil elastase-like proteases as observed in PLS patients can be achieved by pharmacological inhibition of bone marrow CatC. Such a transitory inhibition of CatC might thus help to rebalance the protease load during chronic inflammatory diseases, which opens new perspectives for therapeutic applications in humans.

Simplified, serine-rich theta-defensin analogues as antitumour peptides

θ-defensins belong to the family of host defence peptides. They are the only known example of cyclic polypeptides in animal proteomes. This study presents the synthesis of simplified θ-defensin analogues with pairs of cysteine replaced either by alanine, leucine or serine residues. Cytotoxicity tests were performed on human mammary epithelial (HB2) and breast cancer (SKBR3, MDA-MB-231) cell lines to determine whether peptides are selectively targeting cancer cells. The effect of these peptides was also evaluated in 3D Matrigel cultures, which are based on extracellular matrix components and therefore closely represent in vivo conditions. Finally, to determine whether analogues are able to sensitize MDA-MB-231 triple-negative breast cancer cells to chemotherapeutics, we co-administrated peptides with cisplatin or doxorubicin hydrochloride also in 3D Matrigel cultures. Additionally, cytotoxicity towards peripheral blood mononuclear cells and haemolytic effect were examined for a chosen representative of synthesized compounds. The results showed that positively charged serine-containing θ-defensin derivatives were more cytotoxic towards breast cancer cells (SKBR3, MDA-MB-231) than towards mammary epithelial cells (HB2). Analogues enhanced the effect of cisplatin and doxorubicin hydrochloride on triple-negative breast cancer cell line (MDA-MB-231).

Substrate profiling of Zika virus NS2B-NS3 protease

Zika virus (ZIKV), isolated from macaques in Uganda in 1947, was not considered to be a dangerous human pathogen. However, this view has recently changed as ZIKV infections are now associated with serious pathological disorders including microcephaly and Guillain-Barré syndrome. Similar to other viruses in the Flaviviridae family, ZIKV expresses the serine protease NS3 which is responsible for viral protein processing and replication. Herein, we report the expression of an active NS3^pro domain fused with the NS2B cofactor (NS2B_LN NS3^pro ) in a prokaryotic expression system and profile its specificity for synthesized FRET-type substrate libraries. Our findings pave way for screening potential intracellular substrates of NS3 and for developing specific inhibitors of this ZIKV protease.

The LD loop as an important structural element required for transmission of the allosteric signal in the HtrA (DegP) protease from Escherichia coli

High-temperature requirement A (HtrA; DegP) from Escherichia coli, an important element of the extracytoplasmic protein quality-control system, is a member of the evolutionarily conserved family of serine proteases. The characteristic feature of this protein is its allosteric mode of activation. The regulatory loops, L3, L2, L1 and LD, play a crucial role in the transmission of the allosteric signal. Yet, the role of LD has not been fully elucidated. Therefore, we undertook a study to explain the role of the individual LD residues in inducing and maintaining the proteolytic activity of HtrA. We investigated the influence of amino acid substitutions located within the LD loop on the kinetics of a model substrate cleavage as well as on the dynamics of the oligomeric structure of HtrA. We found that the mutations that were expected to disturb the loop's structure and/or interactions with the remaining regulatory loops severely diminished the proteolytic activity of HtrA. The opposite effect, that is, increased activity, was observed for G174S substitution, which was predicted to strengthen the interactions mediated by LD. HtrAG174S protein had an equilibrium shifted toward the active enzyme and formed preferentially high-order oligomeric forms.

Bladder cancer detection using a peptide substrate of the 20S proteasome

The 20S catalytic core of the human 26S proteasome can be secreted from cells, and high levels of extracellular 20S proteasome have been linked to many types of cancers and autoimmune diseases. Several diagnostic approaches have been developed that detect 20S proteasome activity in plasma, but these suffer from problems with efficiency and sensitivity. In this report, we describe the optimization and synthesis of an internally quenched fluorescent substrate of the 20S proteasome, and investigate its use as a potential diagnostic test in bladder cancer. This peptide, 2-aminobenzoic acid (ABZ)-Val-Val-Ser-Tyr-Ala-Met-Gly-Tyr(3-NO2 )-NH2 , is cleaved by the chymotrypsin 20S proteasome subunit and displays an excellent specificity constant value (9.7 × 10(5)  m(-1) ·s(-1) ) and a high kcat (8 s(-1) ). Using this peptide, we identified chymotrypsin-like proteasome activity in the majority of urine samples obtained from patients with bladder cancer, whereas the proteasome activity in urine samples from healthy volunteers was below the detection limit (0.5 pm). These findings were confirmed by an inhibitory study and immunochemistry methods.