Simultaneous stimulation of GABA and beta adrenergic receptors stabilizes isotypes of activated adenylyl cyclase heterocomplex

BACKGROUND: We investigated how the synthesis of cAMP, stimulated by isoproterenol acting through β-adrenoreceptors and Gs, is strongly amplified by simultaneous incubation with baclofen. Baclofen is an agonist of δ-aminobutyric acid type B receptors [GABA(B)], known to inhibit adenylyl cyclase via Gi. Because these agents have opposite effects on cAMP levels, the unexpected increase in cAMP synthesis when they are applied simultaneously has been intensively investigated. From previous reports, it appears that cyclase type II contributes most significantly to this phenomenon. RESULTS: We found that simultaneous application of isoproterenol and baclofen specifically influences the association/dissociation of molecules involved in the induction and termination of cyclase activity. Beta/gamma from [GABA]B receptor-coupled Gi has a higher affinity for adenylyl cyclase isoform(s) when these isoforms are co-associated with Gs. Our data also suggest that, when beta/gamma and Gαs are associated with adenylyl cyclase isoform(s), beta/gamma from [GABA]B receptor-coupled Gi retards the GTPase activity of Gαs from adrenergic receptor. These reciprocal regulations of subunits of the adenylyl cyclase complex might be responsible for the drastic increase of cAMP synthesis in response to the simultaneous signals. CONCLUSIONS: Simultaneous signals arriving at a particular synapse converge on molecular detectors of coincidence and trigger specific biochemical events. We hypothesize that this phenomenon comes from the complex molecular architectures involved, including scaffolding proteins that make reciprocal interactions between associated molecules possible. The biochemistry of simultaneous signaling is addressed as a key to synaptic function

Using the pea aphid Acrythociphon pisum as a tool for screening biological responses to chemicals and drugs

<p>Abstract</p> <p>Background</p> <p>Though the biological process of aphid feeding is well documented, no one to date has sought to apply it as a tool to screen the biological responses to chemicals and drugs, in ecotoxicology, genotoxicology and/or for interactions in the cascade of sequential molecular events of embryogenesis. Parthenogenetic insect species present the advantage of an anatomical system composed of multiple germarium/ovarioles in the same mother with all the intermediate maturation stages of embryos from oocyte to first instar larva birth. This could be used as an interesting model to visualize at which step drugs interact with the cell signalling pathway during the ordered developmental process.</p> <p>Findings</p> <p>We designed a simple test for screening drugs by investigating simultaneously zygote mitotic division, the progression of embryo development, cell differentiation at early developmental stages and finally organogenesis and population growth rate. We aimed to analyze the toxicology effects of compounds and/or their interference on cellular signalling by examining at which step of the cascade, from zygote to mature embryo, the developmental process is perturbed. We reasoned that a parthenogenetic founder insect, in which the ovarioles shelter numerous embryos at different developmental stages, would allow us to precisely pinpoint the step of embryogenesis in which chemicals act through specific molecular targets as the known ordered homeobox genes.</p> <p>Conclusion</p> <p>Using this method we report the results of a genotoxicological and demographic analysis of three compound models bearing in common a bromo group: one is integrated as a base analog in DNA synthesis, two others activate permanently kinases. We report that one compound (Br-du) altered drastically embryogenesis, which argues in favor of this simple technique as a cheap first screening of chemicals or drugs to be used in a number of genotoxicology applications.</p

Exploratory behaviour in NO-dependent cyclase mutants of Drosophila shows defects in coincident neuronal signalling

<p>Abstract</p> <p>Background</p> <p><it>Drosophila </it>flies explore the environment very efficiently in order to colonize it. They explore collectively, not individually, so that when a few land on a food spot, they attract the others by signs. This behaviour leads to aggregation of individuals and optimizes the screening of mates and egg-laying on the most favourable food spots.</p> <p>Results</p> <p>Flies perform cycles of exploration/aggregation depending on the resources of the environment. This behavioural ecology constitutes an excellent model for analyzing simultaneous processing of neurosensory information. We reasoned that the decision of flies to land somewhere in order to achieve aggregation is based on simultaneous integration of signals (visual, olfactory, acoustic) during their flight. On the basis of what flies do in nature, we designed laboratory tests to analyze the phenomenon of neuronal coincidence. We screened many mutants of genes involved in neuronal metabolism and the synaptic machinery.</p> <p>Conclusion</p> <p>Mutants of NO-dependent cyclase show a specifically-marked behaviour phenotype, but on the other hand they are associated with moderate biochemical defects. We show that these mutants present errors in integrative and/or coincident processing of signals, which are not reducible to the functions of the peripheral sensory cells.</p

Nano-architecture of gustatory chemosensory bristles and trachea in Drosophila wings

International audienceIn the Drosophila wing anterior margin, the dendrites of gustatory neurons occupy the interior of thin and long bristles that present tiny pores at their extremities. Many attempts to measure ligand-evoked currents in insect wing gustatory neurons have been unsuccessful for technical reasons. The functions of this gustatory activity therefore remain elusive and controversial. To advance our knowledge on this understudied tissue, we investigated the architecture of the wing chemosensory bristles and wing trachea using Raman spectroscopy and fluorescence microscopy. We hypothesized that the wing gustatory hair, an open-ended capillary tube, and the wing trachea constitute biological systems similar to nano-porous materials. We present evidence that argues in favour of the existence of a layer or a bubble of air beneath the pore inside the gustatory hair. We demonstrate that these hollow hairs and wing tracheal tubes fulfil conditions for which the physics of fluids applied to open-ended capillaries and porous materials are relevant. We also document that the wing gustatory hair and tracheal architectures are capable of trapping volatile molecules from the environment, which might increase the efficiency of their spatial detection by way of wing vibrations or during flight

Continued Neurogenesis in Adult Drosophila as a Mechanism for Recruiting Environmental Cue-Dependent Variants

Background The skills used by winged insects to explore their environment are strongly dependent upon the integration of neurosensory information comprising visual, acoustic and olfactory signals. The neuronal architecture of the wing contains a vast array of different sensors which might convey information to the brain in order to guide the trajectories during flight. In Drosophila, the wing sensory cells are either chemoreceptors or mechanoreceptors and some of these sensors have as yet unknown functions. The axons of these two functionally distinct types of neurons are entangled, generating a single nerve. This simple and accessible coincidental signaling circuitry in Drosophila constitutes an excellent model system to investigate the developmental variability in relation to natural behavioral polymorphisms. Methodology/Principal Findings A fluorescent marker was generated in neurons at all stages of the Drosophila life cycle using a highly efficient and controlled genetic recombination system that can be induced in dividing precursor cells (MARCM system, flybase web site). It allows fluorescent signals in axons only when the neuroblasts and/or neuronal cell precursors like SOP (sensory organ precursors) undergo division during the precedent steps. We first show that a robust neurogenesis continues in the wing after the adults emerge from the pupae followed by an extensive axonal growth. Arguments are presented to suggest that this wing neurogenesis in the newborn adult flies was influenced by genetic determinants such as the frequency dependent for gene and by environmental cues such as population density. Conclusions We demonstrate that the neuronal architecture in the adult Drosophila wing is unfinished when the flies emerge from their pupae. This unexpected developmental step might be crucial for generating non-heritable variants and phenotypic plasticity. This might therefore constitute an advantage in an unstable ecological system and explain much regarding the ability of Drosophila to robustly adapt to their environment

Trade-Off between Toxicity and Signal Detection Orchestrated by Frequency- and Density-Dependent Genes

Behaviors in insects are partly highly efficient Bayesian processes that fulfill exploratory tasks ending with the colonization of new ecological niches. The foraging (for) gene in Drosophila encodes a cGMP-dependent protein kinase (PKG). It has been extensively described as a frequency-dependent gene and its transcripts are differentially expressed between individuals, reflecting the population density context. Some for transcripts, when expressed in a population at high density for many generations, concomitantly trigger strong dispersive behavior associated with foraging activity. Moreover, genotype-by-environment interaction (GEI) analysis has highlighted a dormant role of for in energetic metabolism in a food deprivation context. In our current report, we show that alleles of for encoding different cGMP-dependent kinase isoforms influence the oxidation of aldehyde groups of aromatic molecules emitted by plants via Aldh-III and a phosphorylatable adaptor. The enhanced efficiency of oxidation of aldehyde odorants into carboxyl groups by the action of for lessens their action and toxicity, which should facilitate exploration and guidance in a complex odor environment. Our present data provide evidence that optimal foraging performance requires the fast metabolism of volatile compounds emitted by plants to avoid neurosensory saturation and that the frequency-dependent genes that trigger dispersion influence these processes

Photoaffinite des recepteurs #mu# et #delta# opioiedes et du recepteur au VIP (vasoactive intestinal peptide)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Rôle et fonctionnalité des récepteurs gustatifs dans les ailes de drosophiles

Les capacités cognitives pour assurer l exploration et la découverte de nouvelles niches écologiques sont au cœur des processus d adaptation et de survie des espèces vertébrés et invertébrés. A cet égard, les systèmes neuronaux chimio-sensoriels composés des organes olfactifs et gustatifs permettent le guidage et repérage des sources de nourritures et/ou des partenaires sexuels. Un fait marquant chez les insectes et en particulier la drosophile réside dans le fait que les organes gustatifs sont disséminés sur le corps. La bordure antérieure de l aile est tapissée avec des sensilles gustatives alternées avec des sensilles mécaniques. La fonctionnalité et le rôle des cellules gustatives au niveau de l aile de la drosophile reste énigmatique et à ce jour largement inconnue (Stocker, 1994). Notre travail a consisté à explorer la signalisation et le mécanisme de transduction de ces récepteurs et à questionner leur importance dans l adaptation des insectes à leur écosystème. Nos résultats portent sur trois volets. Nous avons vérifié que l expression des récepteurs du goût est effective dans les ailes des trois insectes différents (drosophiles, pucerons et abeilles) par RT-PCR. Nous avons ensuite étudié la fonctionnalité de ces récepteurs vis-à-vis des molécules sucrées et amères à l aide d une souche transgénique (G-CaMP), qui exhibe une forte fluorescence provoquée par des piques de calcium cytosolique. Enfin, des tests comportementaux ont été réalisé avec une souche transgénique (Poxn*) dans laquelle les sensilles chimio-sensorielles de l aile sont spécifiquement invalidés sans altérer les autres structures olfactives et/ou gustatives. Les résultats montrent un effet significatif des cellules chimio-sensorielles de l aile quant à l orientation dans l espace et à l apprentissage Bayesien. Nos résultats sur ces trois volets nous ont permis d élaborer des hypothèses au regard de l évolution neuroanatomique de l aile des insectes depuis les organismes ancestraux d origine marine desquels ils dérivent. Des experts en aérodynamiques proposent la création d un vortex durant le vol qui forme une spirale de courant d air le long de la bordure antérieur de l aile. La parfaite superposition entre ce vortex et le nerf costal de l aile nous permet de déduire que les vibrations de l aile entre 50 et 1.000 Hertz chez les insectes sont en mesure de nébuliser des matériaux (micro poussières, micro gouttelettes, molécules faiblement volatiles) lesquels vont être captés/entrainés dans le vortex et adressés aux sensilles gustatives. Notre hypothèse est que ce mécanisme permettrait aux insectes pollinisateurs de gouter les fleurs sans se poser et sans mettre à contribution la trompe buccale (proboscis). Ce scénario permettrait de dissocier le goût de l ingestion digestive en évitant les empoisonnements par des molécules toxiques émises par les plantes et d autre part il rend l exploration plus efficace, en minimisant le temps de recherche.Cognitive capacities used to ensure the exploration and discovery of new ecological niches are at the heart of the process of adaptation and survival of vertebrate and invertebrate species. In this respect, the neural chemosensory systems, composed of the olfactory and gustatory organs, allow the guidance and finding of food sources and/or sexual partners. A striking feature in insects and particularly in Drosophila is that gustatory organs are disseminated in the body. The anterior margin of the wing is lined with gustatory sensilla alternated with mechanosensory sensilla. The function of gustatory cells in the wing of Drosophila remains enigmatic and actually quite unknown (Stocker, 1994). Our work consisted in exploring the signaling and the transduction mechanisms of these receptors and in questioning their importance in the adaptation of insects to their ecosystem. Our results are based on three components. We have verified that the expression of gustatory receptors occurs in the wings of three different insects (Drosophila, aphid and honey bee) by RT-PCR. We have studied the function of these receptors vis-à-vis of sweet and bitter molecules using a transgenic line (G-CaMP) that exhibits a strong fluorescence provoked by cytosolic calcium picks. Finally, behavioral assays have been realized with a transgenic line (Poxn*) in which the chemosensory sensilla have been invalidated without altering the other olfactory and gustatory structures. Our results show a significant effect of wing chemosensory cells as far as orientation is space and Bayesian learning and have permitted us to elaborate hypothesis regarding the neuroanatomical evolution of the wing of insects since ancestral organisms of marine origin from which they derive. Experts in aerodynamics propose the creation of a vortex during flight that forms a spiral of air along the anterior border of the wing. The perfect superposition between this vortex and the costal nerve of the wing allows us to deduce that the vibrations of the insect wing between 50 and 1.000 Hertz are able to nebulize materials (microdust, microdrops, weakly volatile molecules), which are captured/trapped in the vortex and addressed to the gustatory sensilla. Our hypothesis is that this mechanism would let pollinator insects taste flowers without landing and without involving the proboscis. In this scenario insects would dissociate taste from ingestion, avoiding poisoning by toxic molecules emitted by plants and rending exploration more efficient by minimizing searching time.NICE-Bibliotheque electronique (060889901) / SudocSudocFranceF

Evolutionary Divergence of Phosphorylation to Regulate Interactive Protein Networks in Lower and Higher Species

The phosphorylation of proteins affects their functions in extensively documented circumstances. However, the role of phosphorylation in many interactive networks of proteins remains very elusive due to the experimental limits of exploring the transient interaction in a large complex of assembled proteins induced by stimulation. Previous studies have suggested that phosphorylation is a recent evolutionary process that differently regulates ortholog proteins in numerous lineages of living organisms to create new functions. Despite the fact that numerous phospho-proteins have been compared between species, little is known about the organization of the full phospho-proteome, the role of phosphorylation to orchestrate large interactive networks of proteins, and the intertwined phospho-landscape in these networks. In this report, we aimed to investigate the acquired role of phosphate addition in the phenomenon of protein networking in different orders of living organisms. Our data highlighted the acquired status of phosphorylation in organizing large, connected assemblages in Homo sapiens. The protein networking guided by phosphorylation turned out to be prominent in humans, chaotic in yeast, and weak in flies. Furthermore, the molecular functions of GO annotation enrichment regulated by phosphorylation were found to be drastically different between flies, yeast, and humans, suggesting an evolutionary drift specific to each species

The Mapping of Predicted Triplex DNA:RNA in the Drosophila Genome Reveals a Prominent Location in Development- andMorphogenesis-Related Genes

International audienceDouble-stranded DNA is able to form triple-helical structures by accommodating a third nucleotide strand. A nucleic acid triplex occurs according to Hoogsteen rules that predict the stability and affinity of the third strand bound to the Watson–Crick duplex. The " triplex-forming oligonucleotide " (TFO) can be a short sequence of RNA that binds to the major groove of the targeted duplex only when this duplex presents a sequence of purine or pyrimidine bases in one of the DNA strands. Many nuclear proteins are known to bind triplex DNA or DNA:RNA, but their biological functions are unexplored. We identified sequences that are capable of engaging as the " triplex-forming oligonucleotide " in both the pre-lncRNA and pre-mRNA collections of Drosophila melanogaster. These motifs were matched against the Drosophila genome in order to identify putative sequences of triplex formation in intergenic regions, promoters, and introns/exons. Most of the identified TFOs appear to be located in the intronic region of the analyzed genes. Computational prediction of the most targeted genes by TFOs originating from pre-lncRNAs and pre-mRNAs revealed that they are restrictively associated with development-and morphogenesis-related gene networks. The refined analysis by Gene Ontology enrichment demonstrates that some individual TFOs present genome-wide scale matches that are located in numerous genes and regulatory sequences. The triplex DNA:RNA computational mapping at the genome-wide scale suggests broad interference in the regulatory process of the gene networks orchestrated by TFO RNAs acting in association simultaneously at multiple sites