Targeting Extracellular Bacterial Proteases for the Development of Novel Antivirulence Agents

As resistance to clinically available antibiotics persistently increases, applying new strategies to target pathogenic bacteria are paramount to design effective drugs. Bacterial proteases play vital roles in cell viability and stress response, contributing to the pathogenicity of the resistant bacteria. Targeting these extracellular enzymes by antivirulence therapy is a prominent strategy in combating multi-drug resistant bacteria. By preventing the colonization and infiltration of the host, this method can lower selection pressure and reduce resistance development significantly. Here, we review the role of bacterial proteases, the rise of antivirulence therapy and we report on the development of novel antivirulence agents targeting two key virulence factors: elastase B (LasB) from Pseudomonas aeruginosa and collagenase H (ColH) from Clostridium histolyticum

Resolutions of p-stratifolds with isolated singularities

Recently M. Kreck introduced a class of stratified spaces called p-stratifolds [M. Kreck, Stratifolds, Preprint]. He defined and investigated resolutions of p-stratifolds analogously to resolutions of algebraic varieties. In this note we study a very special case of resolutions, so called optimal resolutions, for p-stratifolds with isolated singularities. We give necessary and sufficient conditions for existence and analyze their classification.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol3/agt-3-36.abs.htm

Burden sharing: income, inequality and willingness to fight

What explains citizens’ willingness to fight for their country in times of war? Using six waves of the World Values Survey, this study finds that individual willingness to fight is negatively related with country-level income inequality. When income inequality is high, the rich are less willing to fight than the poor. When inequality is low, the poor and rich differ little in their willingness to fight. This change in the willingness to fight between low and high inequality countries is greater among the rich than among the poor. This article explores several explanations for these findings. The data are consistent with the argument that high inequality makes it more attractive for the rich to buy themselves out of military service

Endoscopic transabdominal cervical cerclage replacement after recurrent late miscarriage

Transabdominal cerclage (TAC) is a recognised treatment for recurrent spontaneous late miscarriage or preterm birth due to cervical weakness. This can be performed via an open procedure before and during pregnancy, or a laparoscopic technique preconception. Complications include cerclage failure and suture migration. We present a case highlighting these complications where laparoscopic removal of an open TAC and replacement led to two successful term deliveries. A woman in her thirties with a fibroid uterus, adenomyosis and a history of three spontaneous mid-trimester losses, had an open TAC at 13 weeks of gestation. Preterm premature rupture of the membranes occurred shortly after and at 18 weeks of gestation she underwent surgical evacuation of the uterus. Subsequent hysteroscopy confirmed migration of the cerclage through the cervical canal. We demonstrate the application of endoscopic gynaecological surgery to remove and replace the TAC with two successful term births by Caesarean section in the ensuing pregnancies

Facile Production of the Pseudomonas aeruginosa Virulence Factor LasB in Escherichia coli for Structure-Based Drug Design

The human pathogen Pseudomonas aeruginosa has a number of virulence factors at its disposal that play crucial roles in the progression of infection. LasB is one of the major virulence factors and exerts its effects through elastolytic and proteolytic activities aimed at dissolving connective tissue and inactivating host defense proteins. LasB is of great interest for the development of novel pathoblockers to temper the virulence, but access has thus far largely been limited to protein isolated from Pseudomonas cultures. Here, we describe a new protocol for high-level production of native LasB in Escherichia coli. We demonstrate that this facile approach is suitable for the production of mutant, thus far inaccessible LasB variants, and characterize the proteins biochemically and structurally. We expect that easy access to LasB will accelerate the development of inhibitors for this important virulence factor

“Clicking“ fragment leads to novel dual-binding cholinesterase inhibitors

Cholinesterase inhibitors are potent therapeutics in the treatment of Alzheimer's disease. Among them, dual binding ligands have recently gained a lot of attention. We discovered novel dual-binding cholinesterase inhibitors, using “clickable” fragments, which bind to either catalytic active site (CAS) or peripheral anionic site (PAS) of the enzyme. Copper(I)-catalyzed azide-alkyne cycloaddition allowed to effectively synthesize a series of final heterodimers, and modeling and kinetic studies confirmed their ability to bind to both CAS and PAS. A potent acetylcholinesterase inhibitor with IC50 = 18 nM (compound 23g) was discovered. A target-guided approach to link fragments by the enzyme itself was tested using butyrylcholinesterase

1-deoxy-D-xylulose-5-phosphate synthase from <i>Pseudomonas aeruginosa</i> and <i>Klebsiella pneumoniae</i> reveals conformational changes upon cofactor binding

The ESKAPE bacteria are the six highly virulent and antibiotic-resistant pathogens that require the most urgent attention for the development of novel antibiotics. Detailed knowledge of target proteins specific to bacteria is essential to develop novel treatment options. The methylerythritol-phosphate (MEP) pathway, which is absent in humans, represents a potentially valuable target for the development of novel antibiotics. Within the MEP pathway, the enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXPS) catalyzes a crucial, rate-limiting first step and a branch point in the biosynthesis of the vitamins B1 and B6. We report the high-resolution crystal structures of DXPS from the important ESKAPE pathogens Pseudomonas aeruginosa and Klebsiella pneumoniae in both the co-factor-bound and the apo forms. We demonstrate that the absence of the cofactor thiamine diphosphate results in conformational changes that lead to disordered loops close to the active site that might be important for the design of potent DXPS inhibitors. Collectively, our results provide important structural details that aid in the assessment of DXPS as a potential target in the ongoing efforts to combat antibiotic resistance.</p

The Non-Mevalonate Pathway to Isoprenoid Biosynthesis:A Potential Source of New Drug Targets

Isoprenoids are an essential class of natural products with a myriad of biological functions. All isoprenoids are assembled using two common five-carbon precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) that are biosynthesized via two completely independent routes: the mevalonate and the non-mevalonate pathway. While the former is used by humans, the latter is employed exclusively by a number of important pathogens such as the malarial Plasmodium falciparum parasite or the tuberculosis-causing Mycobacterium tuberculosis bacterium. Hence, the constituent enzymes are potentially very interesting drug targets in the ongoing fight against diseases, whose treatment has been complicated by the emergence of multi-drug resistance. After a short description of the biosynthetic pathway, an overview will be given on the known inhibitors of the individual enzymes