Identification of a basic surface area of the FADD death effector domain critical for apoptotic signaling

Death effector domains (DEDs) are protein-protein interaction domains found in the death inducing signaling complex (DISC). Performing a structure-based alignment of all DED sequences we identified a region of high diversity in alpha-helix 3 and propose a classification of DEDs into class I DEDs typically containing a stretch of basic residues in the alpha-helix 3 region whereas DEDs of class II do not. Functional assays using mutants of Fas-associated death domain revealed that this basic region influences binding and recruitment of caspase-8 and cellular FLICE inhibitor protein to the DISC.     

A novel model of solute transport in a hollow-fiber bioartificial pancreas based on a finite element method

Extravascular bioartificial pancreas based on hollow fiber seems to be a promising treatment of diabetes mellitus. However, solutes mass-transport limitations in such a device could explain its lack of success. To determine critical device parameters, we have developed a novel tridimensional model based on finite element method for glucose, insulin, and oxygen diffusion around an islet of Langerhans encapsulated in a hollow-fiber section. A glucose ramp stimulation was applied outside the fiber and diffused to the islet. Concomitantly, a stationary oxygen partial pressure was applied outside the fiber, and determined local oxygen partial pressure on the islet environment. An insulin secretion model stimulated by a glucose concentration ramp and corrected by the local oxygen partial pressure was also implemented. Insulin secretion by the islet was thus computed as a response to glucose signal. The model predictions notably showed that the fiber radius had to be small enough to favor a fast response for insulin secretion and to ensure a maximal oxygen partial pressure in the islet environment. Besides the effect of fiber radius, a better islet oxygenation could be achieved by adjustments on the islet density, i.e., on the fiber length dedicated to a single islet. These hints should allow the future proposal of an optimal design for an implantable bioartificial pancreas.     

Melanin-concentrating hormone and its receptors: state of the art

Melanin-concentrating hormone (MCH) is a cyclic neuropeptide of nineteen amino acids in mammals. Its involvement in the feeding behaviour has been well established during the last few years. A first receptor subtype, now termed MCHIR, was discovered in 1999, following the desorphanisation of the SLCI orphan receptor, using either reverse pharmacology or systematic screening of agonist candidates. A second MCH receptor, MCH2R, has been discovered recently, by several groups working on data mining of genomic banks. The molecular pharmacology of these two receptors is only described on the basis of the action of peptides derived from MCH. The present review tentatively summarizes the knowledge on these two receptors and presents the first attempts to discover new classes of antagonists that might have major roles in the control of obesity and feeding behaviour.     

Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus-avis (L.) L.C.M. Rich. and neighbouring tree ectomycorrhizae

Several achlorophyllous orchids associate with ectomycorrhizal hymenomycetes deriving carbon from surrounding trees for the plant. However, this has not been shown for achlorophyllous orchids associating with species of Rhizoctonia, a complex of basal lineages of hymenomycetes that are the most common orchid partners. We analysed Neottia nidus-avis, an achlorophyllous orchid symbiotic with a Rhizoctonia, to identify its symbionts by internal transcribed spacer (ITS) sequencing. Analysis of 61 root systems from 23 French populations showed that N. nidus-avis associates highly specifically with a group of species of Sebacinaceae. Their diversity emphasizes the need for further investigations in the Sebacinaceae systematics. Sebacinoid ITS sequences were often identical within orchid populations and a trend to regional variation in symbionts was observed. Using ITS and intergenic spacer (IGS) polymorphism, we showed that each root system harboured a single species, but that several genets colonized it. However, no polymorphism of these markers was found among portions of each root: this is consistent with the putative mode of entry of the fungus, i.e. from the rhizome into roots but not repeatedly from the soil. In addition, ectomycorrhizae were always found within the N. nidus-avis root systems: 120 of the 144 ectomycorrhizae typed by ITS sequencing were colonized by a sebacinoid fungus identical in ITS sequence to the respective orchid symbiont (even for the IGS polymorphism in some cases). Because sebacinoids were demonstrated recently to be ectomycorrhizal, the orchid is likely to derive its resources from surrounding trees, a mycorrhizal cheating strategy similar to other myco-heterotrophic plants studied to date.     

Targeted Expression of the only Zinc Finger Gene in Transgenic Mice is Associated with Impaired Mammary Development

The only zinc finger (OZF) gene encodes a protein consisting mainly of 10 zinc finger motifs of the Krüppel type of yet unknown function. To potentially assess its in vivo role, mammary targeted deregulation of the expression of the murine gene was performed in transgenic mice using a goat -casein-based transgene. Mammary expression of the transgene was observed in the 11 lines obtained. In three expressing lines, this expression was tissue-specific and developmentally regulated. Further analysis of mice from two expressing lines revealed that transgene-homozygous females could not sustain full growth of their pups. This phenotype was associated with an impaired mammary gland development noticeable only after mid-gestation. It was characterised by an increase of the adipocyte to acini ratio and low or absence of fat globules within these acini compared to non-transgenic control animals. These transgenic observations strongly suggest that OZF is active in the mammary gland, interfering with the lactation process and thus that the described transgenic mice could be useful models to search for the cellular partner(s) of this protein.     

Solid-phase synthesis of alpha-substituted 3-bisarylthio N-hydroxy propionamides as specific MMP inhibitors

A novel series of potent and specific MMP-2,3,9,13 inhibitors has been obtained by modulation on solid phase by alpha and aryl substitutions on 3-arylthio-N-hydroxy-propionamides starting from itaconic acid.     

Homocysteine induces oxidative stress by uncoupling of NO synthase activity through reduction of tetrahydrobiopterin

Hyperhomocysteinemia is a risk factor for cardiovascular diseases that induces endothelial dysfunction. Here, we examine the participation of endothelial NO synthase (eNOS) in the homocysteine-induced alterations of NO/O(2)(-) balance in endothelial cells from human umbilical cord vein. When cells were treated for 24 h, homocysteine dose-dependently inhibited thrombin-activated NO release without altering eNOS phosphorylation and independently of the endogenous NOS inhibitor, asymmetric dimethylarginine. The inhibitory effect of homocysteine on NO release was associated with increased production of reactive nitrogen and oxygen species (RNS/ROS) independent of extracellular superoxide anion (O(2)(-)) and was suppressed by the NOS inhibitor L-NAME. In unstimulated cells, L-NAME markedly decreased RNS/ROS formation and the ethidium red fluorescence induced by homocysteine. This eNOS-dependent O(2)(-) synthesis was associated with reduced intracellular levels of both total biopterins (-45%) and tetrahydrobiopterin (-80%) and increased release of 7,8-dihydrobiopterin and biopterin in the extracellular medium (+40%). In addition, homocysteine suppressed the activating effect of sepiapterin on NO release, but not that of ascorbate. The results show that the oxidative stress and inhibition of NO release induced by homocysteine depend on eNOS uncoupling due to reduction of intracellular tetrahydrobiopterin availability.     

Synthesis of nucleoside libraries on solid support. II. 2,6,8-Trisubstituted purine nucleosides using 8-bromoguanosine as precursor

A series of 2,6,8-trisubstituted purine nucleoside libraries was prepared by parallel solid-phase synthesis using 8-bromoguanosine as a common synthetic precursor. Polystyrene-methoxytrityl chloride resin was linked to the N2 or O5' position of the guanosine analogues. 8-Bromoguanosine was derivatized at the C8 position via carbon-carbon bond formation. Nucleophilic aromatic substitution at C2 and/or C6 positions with various amines produced two series of purine nucleoside libraries with very diverse substitution.     

Nuclear medicine in the era of genomics and proteomics: lessons from annexin V

In the past decade, genomics and proteomics have begun to develop many new targets for potential diagnostic and therapeutic agents. Among the life sciences, nuclear medicine is also deeply involved in the field of clinical investigation. Experience with radiolabeled annexin V highlights the many steps required to translate a good basic-science concept into the clinical setting. This model also emphasizes the value of synergy between basic and medical specialties in developing and optimizing a clinically useful product initially derived from basic investigation.