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1.  Calcium-stores mediate adaptation in axon terminals of Olfactory Receptor Neurons in Drosophila 
BMC Neuroscience  2011;12:105.
Background
In vertebrates and invertebrates, sensory neurons adapt to variable ambient conditions, such as the duration or repetition of a stimulus, a physiological mechanism considered as a simple form of non-associative learning and neuronal plasticity. Although various signaling pathways, as cAMP, cGMP, and the inositol 1,4,5-triphosphate receptor (InsP3R) play a role in adaptation, their precise mechanisms of action at the cellular level remain incompletely understood. Recently, in Drosophila, we reported that odor-induced Ca2+-response in axon terminals of olfactory receptor neurons (ORNs) is related to odor duration. In particular, a relatively long odor stimulus (such as 5 s) triggers the induction of a second component involving intracellular Ca2+-stores.
Results
We used a recently developed in-vivo bioluminescence imaging approach to quantify the odor-induced Ca2+-activity in the axon terminals of ORNs. Using either a genetic approach to target specific RNAs, or a pharmacological approach, we show that the second component, relying on the intracellular Ca2+-stores, is responsible for the adaptation to repetitive stimuli. In the antennal lobes (a region analogous to the vertebrate olfactory bulb) ORNs make synaptic contacts with second-order neurons, the projection neurons (PNs). These synapses are modulated by GABA, through either GABAergic local interneurons (LNs) and/or some GABAergic PNs. Application of GABAergic receptor antagonists, both GABAA or GABAB, abolishes the adaptation, while RNAi targeting the GABABR (a metabotropic receptor) within the ORNs, blocks the Ca2+-store dependent component, and consequently disrupts the adaptation. These results indicate that GABA exerts a feedback control. Finally, at the behavioral level, using an olfactory test, genetically impairing the GABABR or its signaling pathway specifically in the ORNs disrupts olfactory adapted behavior.
Conclusion
Taken together, our results indicate that a relatively long lasting form of adaptation occurs within the axon terminals of the ORNs in the antennal lobes, which depends on intracellular Ca2+-stores, attributable to a positive feedback through the GABAergic synapses.
doi:10.1186/1471-2202-12-105
PMCID: PMC3226658  PMID: 22024464
2.  Peptides That Mimic the Amino-Terminal End of the Rabies Virus Phosphoprotein Have Antiviral Activity▿  
Journal of Virology  2009;83(20):10808-10820.
We wanted to develop a therapeutic approach against rabies disease by targeting the lyssavirus transcription/replication complex. Because this complex (nucleoprotein N-RNA template processed by the L polymerase and its cofactor, the phosphoprotein P) is similar to that of other negative-strand RNA viruses, we aimed to design broad-spectrum antiviral drugs that could be used as a complement to postexposure vaccination and immunotherapy. Recent progress in understanding the structure/function of the rabies virus P, N, and L proteins predicts that the amino-terminal end of P is an excellent target for destabilizing the replication complex because it interacts with both L (for positioning onto the N-RNA template) and N (for keeping N soluble, as needed for viral RNA encapsidation). Thus, peptides mimicking various lengths of the amino-terminal end of P have been evaluated, as follows: (i) for binding properties to the N-P-L partners by the two-hybrid method; (ii) for their capacity to inhibit the transcription/replication of a rabies virus minigenome encoding luciferase in BHK-21-T7 cells; and (iii) for their capacity to inhibit rabies virus infection of BHK-21-T7 cells and of two derivatives of the neuronal SK-N-SH cell line. Peptides P60 and P57 (the first 60 and first 57 NH2 residues of P, respectively) exhibited a rapid, strong, and long-lasting inhibitory potential on luciferase expression (>95% from 24 h to 55 h). P42 was less efficient in its inhibition level (75% for 18 to 30 h) and duration (40% after 48 h). The most promising peptides were synthesized in tandem with the Tat sequence, allowing cell penetration. Their inhibitory effects were observed on BHK-21-T7 cells infected with rabies virus and Lagos bat virus but not with vesicular stomatitis virus. In neuronal cells, a significant inhibition of both nucleocapsid inclusions and rabies virus release was observed.
doi:10.1128/JVI.00977-09
PMCID: PMC2753138  PMID: 19706704

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