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1 […]
GAITAN, Julien; MILOCHAU, Alexandra; LANG, Jochen;
Loss-of-function mutations in ADCY3 cause monogenic severe obesity
Nat Genet, 2018, 0,
Study of monogenic forms of obesity has demonstrated the pivotal role of the central leptin-melanocortin pathway in controlling energy balance, appetite and body weight (1) . The majority of loss-of-function mutations (mostly recessive or co-dominant) have been identified in genes that are directly involved in leptin-melanocortin signaling. These genes, however, only explain obesity in <5% of cases, predominantly from outbred populations (2) . We previously showed that, in a consanguineous population in Pakistan, recessive mutations in known obesity-related genes explain ~30% of cases with severe obesity(3-5). These data suggested that new monogenic forms of obesity could also be identified in this population. Here we identify and functionally characterize homozygous mutations in the ADCY3 gene encoding adenylate cyclase 3 in children with severe obesity from consanguineous Pakistani families, as well as compound heterozygous mutations in a severely obese child of European-American descent. These findings highlight ADCY3 as an important mediator of energy homeostasis and an attractive pharmacological target in the treatment of obesity.
2 […]
ZHANG, Jiarong; BATHANY, Katell; CHAUDIERE, Jean;
Production of 3,4-cis- and 3,4-trans-Leucocyanidin and Their Distinct MS/MS Fragmentation Patterns
Journal of Agricultural and Food Chemistry, 2018, 66, 351-358
(+)-2,3-trans-3,4-cis-Leucocyanidin was produced by acidic epimerization of (+)-2,3-trans-3,4-trans-leucocyanidin synthesized by reduction of (+)-dihydroquercetin with NaBH4, and structures of the two stereoisomers purified by C18- and phenyl-reverse-phase high-performance liquid chromatography (HPLC) were confirmed by NMR spectroscopy. We confirm that only 3,4-cis-leucocyanidin is used by leucoanthocyanidin reductase as substrate. The two stereoisomers are quite stable in aqueous solution at -20 degrees C. Characterization of the two stereoisomers was also performed using electrospray ionization tandem mass spectrometry (ESI-MS/MS), and we discuss here for the first time the corresponding MS/MS fragmentation pathways, which are clearly distinct. The main difference is that of the mode of dehydration of the 3,4-diol in positive ionization mode, which involves a loss of hydroxyl group at either C-3 or C-4 for the 3,4-cis isomer but only at C-3 for the 3,4-trans isomer. Tandem mass spectrometry therefore proves useful as a complementary methodology to NMR to identify each of the two stereoisomers.
3 […]
GENESTE, Emmanuel; GRELARD, Axelle; DUFOURC, Erick;
Photodegradation of novel oral anticoagulants under sunlight irradiation in aqueous matrices
Chemosphere, 2018, 193, 329-336
Kinetics of photodegradation of novel oral anticoagulants dabigatran, rivaroxaban, and apixaban were studied under simulated solar light irradiation in purified, mineral, and river waters. Dabigatran and rivaroxaban underwent direct photolysis with polychromatic quantum yields of 2.2 x 10(-4) and 4.4 x 10(-2), respectively. The direct photodegradation of apixaban was not observed after 19 h of irradiation. Kinetics of degradation of rivaroxaban was not impacted by the nature of the aqueous matrix while photosensitization from nitrate ions was observed for dabigatran and apixaban dissolved in a mineral water. The photosensitized reactions were limited in the tested river water (Isle River, Perigueux, France) certainly due to the hydroxyl radical scavenging effect of the dissolved organic matter. The study of photoproduct structures allowed to identify two compounds for dabigatran. One of them is the 4-aminobenzamidine while the second one is a cyclization product. In the case of rivaroxaban, as studied by very high field NMR, only one photoproduct was observed i.e. a photoisomer. Finally, seven photoproducts were clearly identified from the degradation of apixaban under simulated solar light. (C) 2017 Elsevier Ltd. All rights reserved.
4 […]
SEHL, Anthony; COUEDELO, Leslie; CANSELL, Maud;
A critical assessment of transmethylation procedures for n-3 long-chain polyunsaturated fatty acid quantification of lipid classes
Food chemistry, 2018, 251, 1-8
Lipid transmethylation methods described in the literature are not always evaluated with care so to insure that the methods are effective, especially on food matrix or biological samples containing polyunsaturated fatty acid (PUFA). The aim of the present study was to select a method suitable for all lipid species rich in long chain n-3 PUFA. Three published methods were adapted and applied on individual lipid classes. Lipid (trans)methylation efficiency was characterized in terms of reaction yield and gas chromatography (GC) analysis. The acid-catalyzed method was unable to convert triglycerides and sterol esters, while the method using an incubation at a moderate temperature was ineffective on phospholipids and sterol esters. On the whole only the method using sodium methoxide and sulfuric acid was effective on lipid classes taken individually or in a complex medium. This study highlighted the use of an appropriate (trans)methylation method for insuring an accurate fatty acid composition. Copyright © 2018 Elsevier Ltd. All rights reserved.
5 […]
SAAD, Ahmad; LIET, Benjamin; JOUCLA, Gilles; SANTARELLI, Xavier; TREZEGUET, Véronique;
Role of Glycanation and Convertase Maturation of Soluble Glypican-3 in Inhibiting Proliferation of Hepatocellular Carcinoma Cells
Biochemistry, 2018, 0,
Glypican 3 (GPC3) is a complex heparan sulfate proteoglycan associated with the outer surface of the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor. It is also N-glycosylated and processed by a furin-like convertase. GPC3 has numerous biological functions. Although GPC3 is undetectable in normal liver tissue, it is abnormally and highly overexpressed in hepatocellular carcinoma (HCC). Interestingly, proliferation of HCC cells such as HepG2 and HuH7 is inhibited when they express a soluble form of GPC3 after lentiviral transduction. To obtain more insight into the role of some of its post-translational modifications, we designed a mutant GPC3, sGPC3m, without its GPI anchor, convertase cleavage site, and glycosaminoglycan chains. The highly pure sGPC3m protein strongly inhibited HuH7 and HepG2 cell proliferation in vitro and induced a significant increase in their cell doubling time. It changed the morphology of HuH7 cells but not that of HepG2. It induced the enlargement of HuH7 cell nuclear area and the restructuration of adherent cell junctions. Unexpectedly, for both cell types, the levels of apoptosis, cell division, and beta-catenin were not altered by sGPC3m, although growth inhibition was very efficient. Overall, our data show that glycanation and convertase maturation are not required for sGPC3m to inhibit HCC cell proliferation.
6 […]
ANTUNES, Stéphanie; PERDRIAU, Camille; KAUFFMANN, Brice; PASCO, Morgane; DOUAT, Céline; GUICHARD, Gilles;
Postelongation Strategy for the Introduction of Guanidinium Units in the Main Chain of Helical Oligourea Foldamers
The Journal of organic chemistry, 2018, 0,
The synthesis of hybrid urea-based foldamers containing isosteric guanidinium linkages at selected positions in the sequence is described. We used a postelongation approach whereby the guanidinium moiety is introduced by direct transformation of a parent oligo(urea/thiourea) foldamer precursor. The method involves activation of the thiourea by treatment with methyl iodide and subsequent reaction with amines. To avoid undesired cyclization with the preceding urea moiety, resulting in heterocyclic guanidinium formation in the main chain, the urea unit preceding the thiourea unit in the sequence was replaced by an isoatomic and isostructural gamma-amino acid. The approach was extended to solid-phase techniques to accelerate the synthesis of longer and more functionalized sequences. Under optimized conditions, an octamer hybrid oligomer incorporating a central guanidinium linkage was obtained in good overall yield and purity. This work also reports data related to the structural consequences of urea by guanidinium replacements in solution and reveals that helical folding is substantially reduced in oligomers containing a guanidinium group.
7 […]
GEAN, Julie; DUFOURC, Erick;
The potent effect of mycolactone on lipid membranes
Plos Pathogens, 2018, 14,
Mycolactone is a lipid-like endotoxin synthesized by an environmental human pathogen, Mycobacterium ulcerans, the causal agent of Buruli ulcer disease. Mycolactone has pleiotropic effects on fundamental cellular processes (cell adhesion, cell death and inflammation). Various cellular targets of mycolactone have been identified and a literature survey revealed that most of these targets are membrane receptors residing in ordered plasma membrane nanodomains, within which their functionalities can be modulated. We investigated the capacity of mycolactone to interact with membranes, to evaluate its effects on membrane lipid organization following its diffusion across the cell membrane. We used Langmuir monolayers as a cell membrane model. Experiments were carried out with a lipid composition chosen to be as similar as possible to that of the plasma membrane. Mycolactone, which has surfactant properties, with an apparent saturation concentration of 1 mu M, interacted with the membrane at very low concentrations (60 nM). The interaction of mycolactone with the membrane was mediated by the presence of cholesterol and, like detergents, mycolactone reshaped the membrane. In its monomeric form, this toxin modifies lipid segregation in the monolayer, strongly affecting the formation of ordered microdomains. These findings suggest that mycolactone disturbs lipid organization in the biological membranes it crosses, with potential effects on cell functions and signaling pathways. Microdomain remodeling may therefore underlie molecular events, accounting for the ability of mycolactone to attack multiple targets and providing new insight into a single unifying mechanism underlying the pleiotropic effects of this molecule. This membrane remodeling may act in synergy with the other known effects of mycolactone on its intracellular targets, potentiating these effects.
8 […]
SCHMITTER, Jean-Marie;
Comprehensive targeted and non-targeted lipidomics analyses in failing and non-failing heart
Analytical and bioanalytical chemistry, 2018, 0,
Myocardial infarction (MI) and subsequent progressive heart failure pathology is the major cause of death worldwide; however, the mechanism of this pathology remains unclear. The present work aimed at testing the hypothesis whether the inflammatory response is superimposed with the formation of bioactive lipid resolving molecules at the site of the injured myocardium in acute heart failure pathology post-MI. In this view, we used a robust permanent coronary ligation model to induce MI, leading to decreased contractility index with marked wall thinning and necrosis of the infarcted left ventricle. Then, we applied mass spectrometry imaging (MSI) in positive and negative ionization modes to characterize the spatial distribution of left ventricle lipids in the infarcted myocardium post-MI. After micro-extraction, liquid chromatography coupled to tandem mass spectrometry was used to confirm the structures of the imaged lipids. Statistical tools such as principal component analysis were used to establish a comprehensive visualization of lipid profile changes in MI and no-MI hearts. Resolving bioactive molecules such as resolvin (Rv) D1, RvD5, RvE3, 17-HDHA, LXA4, and 18-HEPE were detected in negative ion mode MSI, whereas phosphatidyl cholines (PC) and oxidized derivatives thereof were detected in positive ion mode. MSI-based analysis demonstrated a significant increase in resolvin bioactive lipids with comprehensive lipid remodeling at the site of infarction. These results clearly indicate that infarcted myocardium is the primary location of inflammation-resolution pathomechanics which is critical for resolution of inflammation and heart failure pathophysiology. Graphical abstract Applied scheme to determine comprehensive lipidomics in failing and non-failing heart.
9 […]
HARTE, Etienne; ELEZGARAY, Juan; ALVES, Isabel; LECOMTE, Sophie;
, 2018, 0,
La présente invention concerne un dispositif et un procédé pour la mesure par spectroscopie d'un échantillon dans lequel on réalise les étapes suivantes: - envoyer un faisceau lumineux vers une surface (12) d'incidence d'un capteur optique, ledit faisceau lumineux formant un angle d'incidence avec ladite surface d'incidence, ledit faisceau lumineux comportant des ondes électromagnétiques p-polarisées et des ondes électromagnétiques s-polarisées, - ledit capteur optique comprenant un prisme (13) comportant une surface de réflexion, un premier film (15) conducteur ou semi-conducteur et un deuxième film (16) diélectrique pour générer deux modes guidés, un premier desdits modes guidés étant généré pour des ondes électromagnétiques p-polarisées et pour un premier angle d'incidence Qi dudit faisceau lumineux sur ladite surface (12) d'incidence et un second desdits modes guidés étant généré pour les ondes électromagnétiques s-polarisés et pour un second angle d'incidence
10 […]
DE, Soumen; CHI, Bo; GRANIER, Thierry; QI, Ting; MAURIZOT, Victor; HUC, Ivan;
Designing cooperatively folded abiotic uni- and multimolecular helix bundles
Nature Chemistry, 2018, 10, 51-57
Abiotic foldamers, that is foldamers that have backbones chemically remote from peptidic and nucleotidic skeletons, may give access to shapes and functions different to those of peptides and nucleotides. However, design methodologies towards abiotic tertiary and quaternary structures are yet to be developed. Here we report rationally designed interactional patterns to guide the folding and assembly of abiotic helix bundles. Computational design facilitated the introduction of hydrogen-bonding functionalities at defined locations on the aromatic amide backbones that promote cooperative folding into helix-turn-helix motifs in organic solvents. The hydrogen-bond-directed aggregation of helices not linked by a turn unit produced several thermodynamically and kinetically stable homochiral dimeric and trimeric bundles with structures that are distinct from the designed helix-turn-helix. Relative helix orientation within the bundles may be changed from parallel to tilted on subtle solvent variations. Altogether, these results prefigure the richness and uniqueness of abiotic tertiary structure behaviour.
11 […]
LECOMTE, Sophie;
Interfacial activity and emulsifying behaviour of inclusion complexes between helical polysaccharides and flavouring molecules resulting from non-covalent interactions
Food research international (Ottawa, Ont.), 2018, 105, 801-811
This study deals with the fabrication of inclusion complexes starting from a cross coupling of seven helical polysaccharides (host) and six flavouring agents (guest). Neither of the substrates is considered as an emulsifier when studied alone. Due to a complexation mechanism, the presence of intermolecular hydrogen bonds between substrates was highlighted by infra-red spectroscopy and 13C NMR. In addition, depending on the polysaccharide used, the guest molecule could be preferentially located either inside or in the interstitial spaces of the helix. In a comparison between raw substrates, the inclusion complexes obtained presented the unique interfacial activity of decreasing surface tension values (gamma) and, in some cases, their behaviour in water was similar to that of regular emulsifiers due to the presence of a critical aggregation concentration (CAC). Substrate concentrations and the ratios between them were the main parameters investigated in this study, which focused on the two inclusion complexes: vanillin/amylose and vanillin/iota-carrageenan. The first decreased gamma values by as much as 53mN/m with a double transition, whereas the second could cause gamma fall to 36mN/m with a regular break. In addition, these systems were able to stabilize foams for up to 60min, which confirmed their unique emulsifying properties.
12 […]
DALLET, Laurence; TAVEAU, Jean-Christophe; LECOMTE, Sophie; POUSSARD, Sylvie; LAMBERT, Olivier;
Single lipoaminoglycoside promotes efficient intracellular antibody delivery: A comprehensive insight into the mechanism of action
Nanomedicine-Nanotechnology Biology and Medicine, 2018, 14, 141-151
Delivery of biologically active proteins into cells is emerging as important strategy for many applications. Previous experiments have shown that lipoaminoglycosides were capable of delivery of the anti-cytokeratin8 antibody (anti-K8) but only when formulated with lipid helpers potentially leading to toxicity from excess lipids. Here, we optimized anti-K8 delivery with various lipoaminoglycosides in the absence of a lipid helper. Results led to the identification of the aminoglycoside lipid dioleyl phosphoramido ribostamycin (DOPRI) as a potent intracellular delivery system for anti-K8. Electron microscopy revealed that delivered anti-K8 molecules were bound to intermediate filaments in cells. Anti-K8 was bound to the surface of DOPRI vesicles without perturbing lipid organization. Macropinocytosis and caveolin mediated endocytosis contributed to anti-K8 internalization and to filament labeling with a major contribution being made by the caveolin pathway. The results showed that the unique properties of DOPRI were sufficient for efficient intracellular protein delivery without requiring lipid helpers. (C) 2017 Elsevier Inc. All rights reserved.
13 […]
CULLIN, Christophe;
Guidelines and recommendations on yeast cell death nomenclature
Microbial Cell, 2018, 5, 4-31
Elucidating the biology of yeast in its full complexity has major implications for science, medicine and industry. One of the most critical processes determining yeast life and physiology is cellular demise. However, the investigation of yeast cell death is a relatively young field, and a widely accepted set of concepts and terms is still missing. Here, we propose unified criteria for the definition of accidental, regulated, and programmed forms of cell death in yeast based on a series of morphological and biochemical criteria. Specifically, we provide consensus guidelines on the differential definition of terms including apoptosis, regulated necrosis, and autophagic cell death, as we refer to additional cell death routines that are relevant for the biology of (at least some species of) yeast. As this area of investigation advances rapidly, changes and extensions to this set of recommendations will be implemented in the years to come. Nonetheless, we strongly encourage the authors, reviewers and editors of scientific articles to adopt these collective standards in order to establish an accurate framework for yeast cell death research and, ultimately, to accelerate the progress of this vibrant field of research.
14 […]
PLAWINSKI, Laurent; DURRIEU, Marie-Christine;
Opto-acoustic microscopy reveals adhesion mechanics of single cells
The Review of scientific instruments, 2018, 89, 014901-014901
Laser-generated GHz-ultrasonic-based technologies have shown the ability to image single cell adhesion and stiffness simultaneously. Using this new modality, we here demonstrate quantitative indicators to investigate contact mechanics and adhesion processes of the cell. We cultured human cells on a rigid substrate, and we used an inverted pulsed opto-acoustic microscope to generate acoustic pulses containing frequencies up to 100 GHz in the substrate. We map the reflection of the acoustic pulses at the cell-substrate interface to obtain images of the acoustic impedance of the cell, Zc, as well as of the stiffness of the interface, K, with 1 mum lateral resolution. Our results show that the standard deviation DeltaZc reveals differences between different cell types arising from the multiplicity of local conformations within the nucleus. From the distribution of K-values within the nuclear region, we extract a mean interfacial stiffness, Km, that quantifies the average contact force in areas of the cell displaying weak bonding. By analogy with classical contact mechanics, we also define the ratio of the real to nominal contact areas, Sr/St. We show that Km can be interpreted as a quantitative indicator of passive contact at metal-cell interfaces, while Sr/St is sensitive to active adhesive processes in the nuclear region. The ability to separate the contributions of passive and active adhesion processes should allow gaining insight into cell-substrate interactions, with important applications in tissue engineering.
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informations Dernière mise à jour : 20/03/2014

CNRS Université de Bordeaux Institut Polytechnique de Bordeaux