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

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

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

Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling-5

<p><b>Copyright information:</b></p><p>Taken from "Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling"</p><p>http://www.biomedcentral.com/1471-2202/8/65</p><p>BMC Neuroscience 2007;8():65-65.</p><p>Published online 6 Aug 2007</p><p>PMCID:PMC1963332.</p><p></p>hybrid GFP (first chromosome) and homozygous for mutations were analyzed for the fluorescence in the wing. The rescue in background was analyzed as double heterozygous (). Flies were heat-shocked at day 3 and analyzed two days later. Positive control: MARCM system (chromosome recombination based on flipase under heat-shock promotor induces axonal marker -)

Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling-1

<p><b>Copyright information:</b></p><p>Taken from "Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling"</p><p>http://www.biomedcentral.com/1471-2202/8/65</p><p>BMC Neuroscience 2007;8():65-65.</p><p>Published online 6 Aug 2007</p><p>PMCID:PMC1963332.</p><p></p>re. In tube (C), homozygous mutants their genetic background give: T value 3.87, P = 0.001, degrees of freedom: 18 ; T value 7.6, P = 0.0001, degrees of freedom: 18 (); T value 4.36, P = 0.0004, degrees of freedom 18 (). The heterozygous mutants show a similar trend (n = 10). Statistics for mutants genetic background in tube C: T value 4, P = 0.001, degrees of freedom: 16 (and ); T value 1.98, P = 0.06, degrees of freedom: 16 (). (2) The experiment was also performed using a derivative protocol: one single pierced transparent tube was used with 1 ml grape juice in a saturated atmosphere. We observed progression of the accumulation from 2 to 24 hours. Values are mean ± SEM (n = 10). For at 24 hours: T value 1.8, P value: 0.085, degrees of freedom: 18 (3) Analysis of the mutant and the rescue (protocol as in (1)). The rescue (, along with , exposed to single acute heat shock at late third instar larva 3 day old adult stage, showed reverse phenotype (similar to control genetic background). Statistics for the mutant the rescue in tube C: T value 3.42, P = 0.003, degrees of freedom: 18 (n = 10)

Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling-0

<p><b>Copyright information:</b></p><p>Taken from "Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling"</p><p>http://www.biomedcentral.com/1471-2202/8/65</p><p>BMC Neuroscience 2007;8():65-65.</p><p>Published online 6 Aug 2007</p><p>PMCID:PMC1963332.</p><p></p>�l) was placed inside the three systems. The protocols are described in the Methods section. Briefly, tubes are painted black to eliminate any visual interference with exploration. One set of experiments is carried out in an aerated chamber (odour gradients are maintained), the other in grape juice-saturated atmosphere (see figure 4 and Methods section). One hundred flies were placed in the chamber and the flies inside the 3 tubes were counted 10 hours later. (A) tube with 50 μl, (B) 100 μl and (C) 300 μl. The mutants , and were analyzed along with genetic background and . Values are mean ± SEM (n = 10)

Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling-3

<p><b>Copyright information:</b></p><p>Taken from "Exploratory behaviour in NO-dependent cyclase mutants of shows defects in coincident neuronal signalling"</p><p>http://www.biomedcentral.com/1471-2202/8/65</p><p>BMC Neuroscience 2007;8():65-65.</p><p>Published online 6 Aug 2007</p><p>PMCID:PMC1963332.</p><p></p>nts. Mutants (20 flies, 5 days old, red eyed, females to avoid pheromone interference) were released in the chamber without disturbing the aggregated spot (aggregates stable, probably because of altered vision). Simultaneously, a second fresh spot was placed inside. Here, the graph represents the time course of the ratio of aggregated flies (or ) on the pre-aggregated spot the fresh one. Values are mean ± SEM (n = 10). The mutant against control gave T value: 3.38, P = 0.003 and degrees of freedom: 18. Heat shock rescue was carried out as in figure 1. () The control of flies aggregated the total in the chamber is represented for the strains tested above. We saw no significant differences between the strains. The apparatus was the same than in the figure 5 and 6