Diphenyl Urea Derivatives as Inhibitors of Transketolase: A Structure-Based Virtual Screening

Transketolase is an enzyme involved in a critical step of the non-oxidative branch of the pentose phosphate pathway whose inhibition could lead to new anticancer drugs. Here, we report new human transketolase inhibitors, based on the phenyl urea scaffold, found by applying structure-based virtual screening. These inhibitors are designed to cover a hot spot in the dimerization interface of the homodimer of the enzyme, providing for the first time compounds with a suggested novel binding mode not based on mimicking the thiamine pyrophosphate cofactor

Metabolic Effects of Acute Thiamine Depletion Are Reversed by Rapamycin in Breast and Leukemia Cells

Thiamine-dependent enzymes (TDEs) control metabolic pathways that are frequently altered in cancer and therefore present cancer-relevant targets. We have previously shown that the recombinant enzyme thiaminase cleaves and depletes intracellular thiamine, has growth inhibitory activity against leukemia and breast cancer cell lines, and that its growth inhibitory effects were reversed in leukemia cell lines by rapamycin. Now, we first show further evidence of thiaminase therapeutic potential by demonstrating its activity against breast and leukemia xenografts, and against a primary leukemia xenograft. We therefore further explored the metabolic effects of thiaminase in combination with rapamycin in leukemia and breast cell lines. Thiaminase decreased oxygen consumption rate and increased extracellular acidification rate, consistent with the inhibitory effect of acute thiamine depletion on the activity of the TDEs pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes; these effects were reversed by rapamycin. Metabolomic studies demonstrated intracellular thiamine depletion and the presence of the thiazole cleavage product in thiaminase-treated cells, providing validation of the experimental procedures. Accumulation of ribose and ribulose in both cell lines support the thiaminase-mediated suppression of the TDE transketolase. Interestingly, thiaminase suppression of another TDE, branched chain amino ketoacid dehydrogenase (BCKDH), showed very different patterns in the two cell lines: in RS4 leukemia cells it led to an increase in BCKDH substrates, and in MCF-7 breast cancer cells it led to a decrease in BCKDH products. Immunoblot analyses showed corresponding differences in expression of BCKDH pathway enzymes, and partial protection of thiaminase growth inhibition by gabapentin indicated that BCKDH inhibition may be a mechanism of thiaminase-mediated toxicity. Surprisingly, most of thiaminase-mediated metabolomic effects were also reversed by rapamycin. Thus, these studies demonstrate that acute intracellular thiamine depletion by recombinant thiaminase results in metabolic changes in thiamine-dependent metabolism, and demonstrate a previously unrecognized role of mTOR signaling in the regulation of thiamine-dependent metabolism

Validation of the short time correlation analysis

International audienc

In-Situ Survey System of Resistive and Thermoelectric Properties of Either Pure or Mixed Materials in Thin Films Evaporated Under Ultra High Vacuum

The study of thermoelectric and resistive in situ behaviours depending on temperature for thin films of either pure or composite materials obtained under ultra-high vacuum, is very interesting, since they can be used as strain gauges or superficial resistances. However, studies become particularly difficult when the measurements generate very low-level electrical signals. Indeed, these turn out to be hardly detectable because of the perturbations brought by the experimental environment. The apparatus described below allows for the measurement of resistance with a relative uncertainty of $2\times10^{-4}$, resistance variation with an absolute uncertainty of 2 m$\Omega$ and thermoelectric e.m.f. of about 2 $\mu$V. Films studied in the laboratory generally exhibit resistances lower than 100 $\Omega$ and resistance variations due to temperature variations of about a few ohms. So this device has sufficient technical characteristics for our studies. It can be connected to a PC, which allows for easy data collection and treatment.L'étude des comportements résistif et thermoélectrique in situ en fonction de la température de couches minces de matériaux simples ou composites obtenus en milieu raréfié s'avére intéressante en vue d'applications comme jauge de contrainte ou résistance superficielle mais particulièrement délicate lorsque les mesures donnent naissance à des signaux électriques de très faible amplitude. Ces derniers deviennent en effet difficilement décelables en raison des perturbations apportées par l'environnement expérimental. Le système qui est décrit ici permet de mesurer des résistances avec une certitude relative de $2\times10^{-4}$ et d'apprécier des variations de résistance de 2 m$\Omega$ et des f.e.m. thermoélectriques de l'ordre de 2 $\mu$V. Les couches étudiées au laboratoire présentent généralement des résistances inférieures à 100 $\Omega$ et des variations de résistance dues aux variations de température de l'ordre de quelques $\Omega$. Le dispositif de mesure présente donc des caractéristiques techniques suffisantes pour nos études. Connecté à un PC il permet l'acquisition des données et un traitement rapide

One-Shot Synthesis of a Poly( N -isopropylacrylamide)/Silica Hybrid Gel

International audienc

Synthesis Of New Polymer Matrices Including Amino Acids

International audienceCurrently the application of biomolecules such as amino acids, carbohydrates and nucleic acids in the diagnostic and treatment (drug delivery) of wide number of diseases turned on the effort of many scientific groups on their encapsulation[ ]. The matrices based on different organic or/and inorganic materials were used. Significant problems arise due to multifunctionality of these molecules. The choice of polymer matrix as well as suitable approach for first amino acid bonding plays a crucial role of biomolecule incorporation process. The sol-gel technology is a modern technique to obtain hybrid polymer matrices. It is based on the hydrolysis of starting materials and further polycondensation process. The strictly control of these processes plays key role for the properties of final materials as well as the protection against precipitates formation. Herein we report for several strategies for amino acid incorporation in organic and/or inorganic polymers. Different type of amino acids (either with different pKa or spatial obstructed group) is linked in order to study the structure of the final material. The rheological properties (elasticity and viscosity) of these matrices are studied by means of an ultrasonic technique developed in our laboratory. The experimental results of the G' and G" moduli for different condition of elaboration is used to access to the microstructure evolution [ ]. Some advantages and defaults due to type of amino acid protection as well as solvent systems used for polymerization process will be discussed. The obtained matrices will be further used for biosensors and bioreactors design

Lamb mode reflections at the end of a plate loaded by a viscoelastic material

International audienc

Ultrasonic monitoring of yoghurt formation by using AT-cut quartz: Lighting of casein micelles interactions process during the acidification

International audienc