New active leads for Tuberculosis booster drugs by structure-based drug discovery

The transcriptional regulator EthR from Mycobacterium tuberculosis, a member of the TetR family of prokaryotic homo-dimeric transcriptions factors, controls the expression of the mycobacterial mono-oxygenase EthA. Due to the fact that EthA is responsible for the bio-activation of the second-line tuberculosis pro-drug ethionamide, EthR inhibitors have been shown to boost drug efficacy by increasing EthA levels. Here, we present a comprehensive in-silico structure-based screening protocol that led to the identification of a number of novel scaffolds of EthR inhibitors. We present biophysical characterization of 85 potential leads, 20 of which showed binding by thermal shift assays. The co-crystal structures of EthR with four new ligands at resolution ranging from 2.1 to 1.4 Å confirm the binding and inactivation mode. The crystal structures include ligands with three new chemical scaffolds that will enable future lead development. Five of the lead compounds showed the desired booster effect with the most promising displaying an EC50 value of 0.76 μM

Drug Target Engagement using coupled Cellular Thermal Shift Assay -acoustic Reverse Phase Protein Array

International audienceIn the last 5 years, cellular thermal shift assay (CETSA), a technology based on ligand-induced changes in protein thermal stability, has been increasingly used in drug discovery to address the fundamental question of whether drug candidates engage their intended target in a biologically relevant setting. To analyze lysates from cells submitted to increasing temperature, the detection and quantification of the remaining soluble protein can be achieved using quantitative mass spectrometry, Western blotting, or AlphaScreen techniques. Still, these approaches can be time- and cell-consuming. To cope with limitations of throughput and protein amount requirements, we developed a new coupled assay combining the advantages of a nanoacoustic transfer system and reverse-phase protein array technology within CETSA experiments. We validated the technology to assess engagement of inhibitors of insulin-degrading enzyme (IDE), an enzyme involved in diabetes and Alzheimer’s disease. CETSA—acoustic reverse-phase protein array (CETSA-aRPPA) allows simultaneous analysis of many conditions and drug–target engagement with a small sample size, in a rapid, cost-effective, and biological material-saving manner

Dynamin 2 mutations associated with human diseases impair clathrin-mediated receptor endocytosis

Dynamin 2 (DNM2) is a large GTPase involved in the release of nascent vesicles during endocytosis and intracellular membrane trafficking. Distinct DNM2 mutations, affecting the middle domain (MD) and the Pleckstrin homology domain (PH), have been identified in autosomal dominant centronuclear myopathy (CNM) and in the intermediate and axonal forms of the Charcot-Marie-Tooth peripheral neuropathy (CMT). We report here the first CNM mutation (c.1948G>A, p.E650K) in the DNM2 GTPase effector domain (GED), leading to a slowly progressive moderate myopathy. COS7 cells transfected with DNM2 constructs harboring a disease-associated mutation in MD, PH, or GED show a reduced uptake of transferrin and low-density lipoprotein (LDL) complex, two markers of clathrin-mediated receptor endocytosis. A decrease in clathrin-mediated endocytosis was also identified in skin fibroblasts from one CNM patient. We studied the impact of DNM2 mutant overexpression on epidermal growth factor (EGF)-induced extra

INS-SPECT : Automatisation de la sécrétion d’insuline en réponse à une stimulation au glucose couplée à la spectrométrie de masse MALDI-TOF

International audienceIntroduction : Le diabète est une maladie métabolique caractérisée par une hyperglycémie chronique, conséquence d’un défaut de sécrétion de l’insuline. Afin de déterminer de nouvelles cibles thérapeutiques, il est nécessaire de doser à haut débit cette sécrétion hormonale. Les techniques de dosage actuelles présentent des contraintes économique et temporelle qui rendent difficile le déploiement de stratégies haut débit pour la découverte de nouvelles cibles thérapeutiques pour le traitement du diabète. Dans le but de pallier ces limites, nous avons développé, grâce à un financement START-AIRR, un test de sécrétion d’insuline automatisé couplé à la spectrométrie de masse MALDI-TOF. Matériels et Méthodes :Les cellules béta pancréatique murine Min6 sont mises en culture en plaque 384 puits pendant 48h et soumises au protocole automatisé de sécrétion d’insuline en réponse au glucose (GSIS, Glucose Stimulating Insulin Secretion). Une méthode automatisée de la préparation des surnageant de sécrétion a été mise en place permettant la cristallisation des hormones avant l'analyse par spectrométrie de masse MALDI-TOF/TOF.Résultats : Suite à l’automatisation de l’ensemble du procédé, la sécrétion d’insuline en réponse au glucose des cellules Min6 n’est pas affecté. Cette sécrétion accrue suite à la stimulation est observée sur les différents spectres de masses, normalisée ensuite sur une courbe étalonnage. En parallèle, une automatisation de la transfection des cellules min6 couplée à la sécrétion d’insuline est en cours de validation.Conclusion : Par conséquent, nous avons pu mettre en place une méthode alternative afin de doser l’insuline. L’utilisation de cette nouvelle méthode d’analyse, associée à un screening sur la sécrétion d’insuline à haut débit en utilisant, respectivement, une chimiothèque de 1000 composés et une banque de siRNA ciblant 20000 gènes, nous permettra de valider la robustesse de notre approche

High-Throughput Quantitative Screening of Glucose-Stimulated Insulin Secretion and Insulin Content Using Automated MALDI-TOF Mass Spectrometry

International audienceType 2 diabetes (T2D) is a metabolic disorder characterized by loss of pancreatic β-cell function, decreased insulin secretion and increased insulin resistance, that affects more than 537 million people worldwide. Although several treatments are proposed to patients suffering from T2D, long-term control of glycemia remains a challenge. Therefore, identifying new potential drugs and targets that positively affect β-cell function and insulin secretion remains crucial. Here, we developed an automated approach to allow the identification of new compounds or genes potentially involved in β-cell function in a 384-well plate format, using the murine β-cell model Min6. By using MALDI-TOF mass spectrometry, we implemented a high-throughput screening (HTS) strategy based on the automation of a cellular assay allowing the detection of insulin secretion in response to glucose, i.e., the quantitative detection of insulin, in a miniaturized system. As a proof of concept, we screened siRNA targeting well-know β-cell genes and 1600 chemical compounds and identified several molecules as potential regulators of insulin secretion and/or synthesis, demonstrating that our approach allows HTS of insulin secretion in vitro

Rubrolone production by Dactylosporangium vinaceum: biosynthesis, modulation and possible biological function

International audienceRare actinomycetes are likely treasure troves for bioactive natural products, and it is therefore important that we enrich our understanding of biosynthetic potential of these relatively understudied bacteria. Dactylosporangium are a genus of such rare Actinobacteria that are known to produce a number of important antibacterial compounds, but for which there are still no fully assembled reference genomes, and where the extent of encoded biosynthetic capacity is not defined. Dactylosporangium vinaceum (NRRL B-16297) is known to readily produce a deep wine red-coloured diffusible pigment of unknown origin, and it was decided to define the chemical identity of this natural product pigment, and in parallel use whole genome sequencing and transcriptional analysis to lay a foundation for understanding the biosynthetic capacity of these bacteria. Results show that the produced pigment is made of various rubrolone conjugates, the spontaneous product of the reactive pre-rubrolone, produced by the bacterium. Genome and transcriptome analysis identified the highly expressed biosynthetic gene cluster (BGC) for pre-rubrolone. Further analysis of the fully assembled genome found it to carry 24 additional BGCs, of which the majority were poorly transcribed, confirming the encoded capacity of this bacterium to produce natural products but also illustrating the main bottleneck to exploiting this capacity. Finally, analysis of the potential environmental role of pre-rubrolone found it to react with a number of amine containing antibiotics, antimicrobial peptides and siderophores pointing to its potential role as a “minesweeper” of xenobiotic molecules in the bacterial environment

A fragment-based approach towards the discovery of N-substituted tropinones as inhibitors of Mycobacterium tuberculosis transcriptional regulator EthR2

Tuberculosis (TB) caused by the pathogen Mycobacterium tuberculosis, represents one of the most challenging threat to public health worldwide, and with the increasing resistance to approved TB drugs, it is needed to develop new strategies to address this issue. Ethionamide is one of the most widely used drugs for the treatment of multidrug-resistant TB. It is a prodrug that requires activation by mycobacterial monooxygenases to inhibit the enoyl-ACP reductase InhA, which is involved in mycolic acid biosynthesis. Very recently, we identified that inhibition of a transcriptional repressor, termed EthR2, derepresses a new bioactivation pathway that results in the boosting of ethionamide activation. Herein, we describe the identification of potent EthR2 inhibitors using fragment-based screening and structure-based optimization. A target-based screening of a fragment library using thermal shift assay followed by X-ray crystallography identified 5 hits. Rapid optimization of the tropinone chemical series led to compounds with improved in vitro potency.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Identification of ebselen as a potent inhibitor of insulin degrading enzyme by a drug repurposing screening

International audienceInsulin-degrading enzyme, IDE, is a metalloprotease implicated in the metabolism of key peptides such as insulin, glucagon, β-amyloid peptide. Recent studies have pointed out its broader role in the cell physiology. In order to identify new drug-like inhibitors of IDE with optimal pharmacokinetic properties to probe its multiple roles, we ran a high-throughput drug repurposing screening. Ebselen, cefmetazole and rabeprazole were identified as reversible inhibitors of IDE. Ebselen is the most potent inhibitor (IC50 (insulin) = 14 nM). The molecular mode of action of ebselen was investigated by biophysical methods. We show that ebselen induces the disorder of the IDE catalytic cleft, which significantly differs from the previously reported IDE inhibitors. IDE inhibition by ebselen can explain some of its reported activities in metabolism as well as in neuroprotection

Tricyclic SpiroLactams Kill Mycobacteria In Vitro and In Vivo by Inhibiting Type II NADH Dehydrogenases

International audienceIt is critical that novel classes of antituberculosis drugs are developed to combat the increasing burden of infections by multidrug-resistant strains. To identify such a novel class of antibiotics, a chemical library of unique 3-D bioinspired molecules was explored revealing a promising, mycobacterium specific Tricyclic SpiroLactam (TriSLa) hit. Chemical optimization of the TriSLa scaffold delivered potent analogues with nanomolar activity against replicating and nonreplicating Mycobacterium tuberculosis. Characterization of isolated TriSLa-resistant mutants, and biochemical studies, found TriSLas to act as allosteric inhibitors of type II NADH dehydrogenases (Ndh-2 of the electron transport chain), resulting in an increase in bacterial NADH/NAD+ ratios and decreased ATP levels. TriSLas are chemically distinct from other inhibitors of Ndh-2 but share a dependence for fatty acids for activity. Finally, in vivo proof-of-concept studies showed TriSLas to protect zebrafish larvae from Mycobacterium marinum infection, suggesting a vulnerability of Ndh-2 inhibition in mycobacterial infections

Topical Intestinal Aminoimidazole Agonists of G-Protein-Coupled Bile Acid Receptor 1 Promote Glucagon Like Peptide-1 Secretion and Improve Glucose Tolerance

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