Chapter Regulation of the G1/S Transition in Adult Liver: Expression and Activation of the Cyclin Dependent Kinase Cdk1 in Differentiated Hepatocytes is Controlled by Extracellular Signals and is Crucial for Commitment to DNA Replication

Electronics engineerin

Araf51 with improved transglycosylation activities: One engineered biocatalyst for one specific acceptor

International audienceA random mutagenesis of the arabinofuranosyl hydrolase Araf51 has been run in order to access to efficient biocatalysts for the synthesis of alkyl arabinofuranosides. The mutants were selected on their ability to catalyze the transglycosylation reaction of p-nitrophenyl α-L-arabinofuranoside (pNP-Araf) used as a donor and various aliphatic alcohols as acceptors. This screening strategy underlined 5 interesting clones, each one corresponding to one acceptor. They appeared to be much more efficient in the transglycosylation reaction compared to the wild type enzyme whereas no self-condensation or hydrolysis products could be detected. Moreover, the high specificity of the mutants towards the alcohols for which they have been selected validates the screening process. Sequence analysis of the mutated enzymes revealed that, despite their location far from the active site, the mutations affect significantly the kinetics properties as well as the substrate affinity of these mutants towards the alcoholacceptors in the transglycosylation reaction

Exploring the synthetic potency of the first furanothioglycoligase through original remote activation.

International audienceThioglycosidic bonds are of utmost importance in biomolecules as their incorporation led to more stable glycomimetics with potential drug activities. Until now only chemical methods were available for their incorporation into glycofuranosyl conjugates. Herein, we wish to describe the use of the first furanothioglycoligase for the preparation of a great variety of thioaryl derivatives with moderate to excellent yields. Of great interest, a stable 1-thioimidoyl arabinofuranose, classically used in chemical glycosylation, was able to efficiently act as a donor through an original enzymatic remote activation mechanism. Study of the chemical structure as well as the nucleophilicity of the thiol allowed us to optimize this biocatalyzed process. As a consequence, this mutated enzyme constitutes an original, mild and eco-friendly method of thioligation

Regulation of hepatic cardiolipin metabolism by TNFα: Implication in cancer cachexia

International audienceCardiolipin (CL) content accumulation leads to an increase in energy wasting in liver mitochondria in a rat model of cancer cachexia in which tumor necrosis factor alpha (TNFα) is highly expressed. In this study we investigated the mechanisms involved in liver mitochondria CL accumulation in cancer cachexia and examined if TNFα was involved in this process leading to mitochondrial bioenergetics alterations. We studied gene, protein expression and activity of the main enzymes involved in CL metabolism in liver mitochondria from a rat model of cancer cachexia and in HepaRG hepatocyte-like cells exposed to 20 ng/ml of TNFα for 12 h. Phosphatidylglycerolphosphate synthase (PGPS) gene expression was increased 2.3-fold (p < 0.02) and cardiolipin synthase (CLS) activity decreased 44% (p < 0.03) in cachectic rat livers compared to controls. CL remodeling enzymes monolysocardiolipin acyltransferase (MLCL AT-1) activity and tafazzin (TAZ) gene expression were increased 30% (p < 0.01) and 50% (p < 0.02), respectively, in cachectic rat livers compared to controls. Incubation of hepatocytes with TNFα increased CL content 15% (p < 0.05), mitochondrial oxygen consumption 33% (p < 0.05), PGPS gene expression 44% (p < 0.05) and MLCL AT-1 activity 20% (p < 0.05) compared to controls. These above findings strongly suggest that in cancer cachexia, TNFα induces a higher energy wasting in liver mitochondria by increasing CL content via upregulation of PGPS expression

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly

Culture Conditions Promoting Hepatocyte Proliferation and Cell Cycle Synchronization

International audienceThe liver overcomes damages induced by harmful substances or viral infections and allows the use of extended resection in human therapy through its remarkable ability to regenerate. The regeneration process relies on the massive proliferation of differentiated hepatocytes that exit quiescence and undergo a limited number of cell cycles to restore the hepatic mass. Many discoveries on the regulation of hepatocyte proliferation have benefited from the use of in vitro models of cultures of primary hepatocytes as well as hepatoma cells as opposed to data obtained from in vivo models of liver regeneration, such as following partial hepatectomy in rodents. In this chapter, the most pertinent in vitro models used to promote the proliferation of hepatocytes and technical procedures to synchronize their progression throughout the cell cycle are presented with the goal to investigate the regulation of the hepatocyte cell cycle and the molecular pathways regulating liver regeneratio

Interaction fonctionnelle de la protéine RBM15B avec les complexes CDK11p110/cyclines L (rôle de ces protéines à l'interface entre transcription et épissage)

Les complexes CDK11p110/cyclines L sont impliqués dans la régulation de la transcription et de l épissage. Nous avons recherché de nouveaux partenaires de CDK11p110 et identifié la protéine RBM15B. Nous avons démontré que RBM15B inhibait l épissage par compétition fonctionnelle avec le complexe CDK11p110/cycline L2a. De plus, RBM15B interagit avec le co-répresseur de transcription NCoR et l histone déacétylase 3 suggérant un rôle dans la régulation de la transcription. Par une analyse transcriptomique, nous avons identifié plusieurs gènes cibles régulés au niveau transcriptionnel par RBM15B tels que le facteur de transcription ATF3 et la sous-unité xCT du transporteur cystine/glutamate. L évidence d altérations géniques de CDK11 et de la cycline L1a dans divers cancers nous a amené à étudier l expression de ces gènes ainsi que RBM15B, ATF3 et SLC7A11 (xCT) dans des biopsies hépatiques humaines tumorales et non tumorales. Nos résultats préliminaires révèlent une importante induction de l expression de SCL7A11 dans les biopsies tumorales en comparaison du foie normal adjacent.The CDK11p110/cyclin L complexes contribute to the control of transcription and RNA maturation. We searched for new binding partners of CDK11p110 and identified the protein RBM15B. We have demonstrated that RBM15B inhibits preRNA splicing through functional competition with the CDK11p110/cycline L2a complex. RBM15B also interacts with the co-repressor of transcription NCoR and the histone deacetylase (HDAC) 3 suggesting its involvement in the control of transcription. Gene profiling analysis led us to identify several target genes of RBM15B including the transcription factor ATF3 and the gene SLC7A11 encoding the sub-unit xCT of the cystine/glutamate transporter. Reported alterations of CDK11 and cyclin L1a in various tumours led us to initiate the study of their expression levels as well as those of RBM15B, ATF3 and SLC7A11 in human hepatocellular carcinomas (HCCs) and peritumoral hepatic parenchyma. Our preliminary data indicate a strong induction of SLC7A11 in HCCs compared to normal tissues.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF