Identification of Small-Molecule Inhibitors of Neutral Ceramidase (nCDase) via Target-Based High-Throughput Screening

There is interest in developing inhibitors of human neutral ceramidase (nCDase) because this enzyme plays a critical role in colon cancer. There are currently no potent or clinically effective inhibitors for nCDase reported to date, so we adapted a fluorescence-based enzyme activity method to a high-throughput screening format. We opted to use an assay whereby nCDase hydrolyzes the substrate RBM 14-16, and the addition of NaIO4 acts as an oxidant that releases umbelliferone, resulting in a fluorescent signal. As designed, test compounds that act as ceramidase inhibitors will prevent the hydrolysis of RBM 14-16, thereby decreasing fluorescence. This assay uses a 1536-well plate format with excitation in the blue spectrum of light energy, which could be a liability, so we incorporated a counterscreen that allows for rapid selection against fluorescence artifacts to minimize false-positive hits. The high-throughput screen of >650,000 small molecules found several lead series of hits. Multiple rounds of chemical optimization ensued with improved potency in terms of IC50 and selectivity over counterscreen assays. This study describes the first large-scale high-throughput optical screening assay for nCDase inhibitors that has resulted in leads that are now being pursued in crystal docking studies and in vitro drug metabolism and pharmacokinetics (DMPK).National Cancer Institute https://doi.org/10.13039/100000054Stony Brook Cancer CenterPeer Reviewe

Rôle physiologique de NOX1 dans la prolifération et la différenciation des cellulles épithéliales coliques

L épithélium colique est en perpétuel renouvellement à partir de cellules souches cryptiques et de progéniteurs qui prolifèrent et se différencient en colonocytes ou mucosécrétantes. Deux voies de signalisation, Notch1 et Wnt coordonnent les processus de prolifération et de différenciation. La NADPH oxydase 1 (NOX1), majoritairement exprimée dans le côlon, pourrait être impliquée dans la prolifération et la différenciation mais son rôle dans le colon reste encore très hypothétique. Dans ce but, nous avons cherché à déterminer le rôle de NOX1 dans l homéostasie colique. Nous démontrons que l épithélium colique des souris déficientes en NOX1 présente une réduction de la prolifération des progéniteurs associée à leur conversion massive en cellules mucosécrétantes (augmentation de 50%). Ces modifications sont corrélées à l inhibition des voies Notch1 et Wnt suggérant que NOX1 puisse être un point central de régulation de ces voies. Nous concluons que NOX1 est essentiel à l homéostasie de l épithélium colique en contrôlant à la fois la prolifération et la différenciation des cellules épithéliales via son interaction avec les voies Notch et Wnt.PARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Mass Spectrometry and Pharmacological Approaches to Measuring Cooption and Reciprocal Activation of Receptor Tyrosine Kinases

Receptor tyrosine kinases (RTKs) can show extensive crosstalk, directly and indirectly. Elucidating RTK crosstalk remains an important goal in the clinical combination of anti-cancer therapies. Here, we present mass spectrometry and pharmacological approaches showing the hepatocyte growth factor receptor (MET)-promoting tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) and other membrane receptors in MET-amplified H1993 NSCLC cells. Conversely, in H292 wt-EGFR NSCLC cells, EGFR promotes the tyrosine phosphorylation of MET. Reciprocal regulation of the EGFR and insulin receptor (IR) was observed in the GEO CRC cells, where inhibition of the EGFR drives tyrosine phosphorylation of the insulin receptor. Similarly, in platelet-derived growth factor receptor (PDGFR)-amplified H1703 NSCLC cells, inhibition of the EGFR promotes the tyrosine phosphorylation of the PDGFR. These RTK interactions are used to illustrate basic principles applicable to other RTK signaling networks. More specifically, we focus on two types of RTK interaction: (1) co-option of one RTK by another and (2) reciprocal activation of one receptor following the inhibition of a distinct receptor

Les Nox/Duox : une nouvelle famille de NADPH oxydases

La production des formes réactives de l’oxygène par la NADPH oxydase phagocytaire a été longtemps considérée comme restreinte aux phagocytes professionnels. Récemment, six homologues de la sous-unité catalytique de la NADPH oxydase phagocytaire (gp91phox ou Nox-2) ont été identifiés et appartiennent à la famille des Nox : Nox-1, Nox-3, Nox-4, Nox-5, Duox-1 et Duox-2. Ces enzymes ont la capacité de transporter des électrons à travers la membrane plasmique et produisent de l’anion superoxyde, luimême précurseur des autres formes réactives de l’oxygène. Cependant, la distribution tissulaire et les mécanismes d’activation des membres de la famille Nox sont très différents, suggérant qu’ils exercent des fonctions physiologiques distinctes dans des mécanismes aussi variés que la défense de l’hôte, la croissance, la différenciation et l’apoptose. La modulation de la fonction des différentes Nox peut être à l’origine d’une grande variété d’événements physiopathologiques

Variation of chromatin loop attachment to nuclear structure around the WAP gene

National audienc

Ceramide synthase 4 and de novo production of ceramides with specific N-acyl chain lengths are involved in gluco-lipotoxicity-induced apoptosis of INS-1 β-cells.

International audiencePancreatic β-cell apoptosis induced by palmitate requires high glucose concentrations. Ceramides have been suggested to be important mediators of gluco-lipotoxicity-induced β-cell apoptosis. In INS-1 β-cells, 0.4 mM palmitate with 5 mM glucose increased the levels of dihydrosphingosine and dihydroceramides, two lipid intermediates in the de novo biosynthesis of ceramides, without inducing apoptosis. Increasing glucose concentrations to 30 mM amplified palmitate-induced accumulation of dihydrosphingosine and the formation of (dihydro)-ceramides. Of note, gluco-lipotoxicity specifically induced the formation of 18:0, 22:0 and 24:1 (dihydro)-ceramide molecular species, which was associated with the up-regulation of ceramide synthase 4 (CerS4) levels. Fumonisin-B1, a ceramide synthase inhibitor, partially blocked apoptosis induced by gluco-lipotoxicity. In contrast, apoptosis was potentiated in the presence of D,L-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol, an inhibitor of glucosyl-ceramide synthase. Moreover, over-expression of CerS4 amplified ceramide production and apoptosis induced by palmitate with 30 mM glucose whereas down-regulation of CerS4 by siRNA reduced apoptosis. CerS4 also potentiates ceramide accumulation and apoptosis induced by another saturated fatty acid, stearate. Collectively, our results suggest that gluco-lipotoxicity induced β-cell apoptosis through a dual mechanism involving the de novo ceramide biosynthesis and the formation of ceramides with specific N-acyl chain lengths rather than an overall increase of ceramide content

Variation of chromatin loop attachment to nuclear structure around the WAP gene

National audienc

Lactogenic hormones affect the attachment of the Whey Acidic Protein gene chromatin loop to nuclear structure

International audienc

Lactogenic hormones affect the attachment of the Whey Acidic Protein gene chromatin loop to nuclear structure

International audienc

Glucolipotoxicity impairs ceramide flow from the endoplasmic reticulum to the Golgi apparatus in INS-1 β-cells.

Accumulating evidence suggests that glucolipotoxicity, arising from the combined actions of elevated glucose and free fatty acid levels, acts as a key pathogenic component in type II diabetes, contributing to β-cell dysfunction and death. Endoplasmic reticulum (ER) stress is among the molecular pathways and regulators involved in these negative effects, and ceramide accumulation due to glucolipotoxicity can be associated with the induction of ER stress. Increased levels of ceramide in ER may be due to enhanced ceramide biosynthesis and/or decreased ceramide utilization. Here, we studied the effect of glucolipotoxic conditions on ceramide traffic in INS-1 cells in order to gain insights into the molecular mechanism(s) of glucolipotoxicity. We showed that glucolipotoxicity inhibited ceramide utilization for complex sphingolipid biosynthesis, thereby reducing the flow of ceramide from the ER to Golgi. Glucolipotoxicity impaired both vesicular- and CERT-mediated ceramide transport through (1) the decreasing of phospho-Akt levels which in turn possibly inhibits vesicular traffic, and (2) the reducing of the amount of active CERT mainly due to a lower protein levels and increased protein phosphorylation to prevent its localization to the Golgi. In conclusion, our findings provide evidence that glucolipotoxicity-induced ceramide overload in the ER, arising from a defect in ceramide trafficking may be a mechanism that contributes to dysfunction and/or death of β-cells exposed to glucolipotoxicity