δ-conopeptide evia isolated from conus ermineus is a new pharmacological tool for discriminating...
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Abstracts / Journal of Physiology - Paris 99 (2006) 245–278 247
Chameau, P., Van de Vrede, Y., Fossier, P., Baux, G., 2001. Ryanodine-,IP3- and NAADP-dependent calcium stores control acetylcholinerelease. Pflugers Arch. 443, 289–296.
d-Conopeptide EVIA isolated from Conus ermineus is a new
pharmacological tool for discriminating sodium channel
subtypes
Julien Barbier a,b, Hung Lamthanh b, Frederic Le Gall b,
Philippe Favreau a, Evelyne Benoit a, Haijun Chen c,
Nicolas Gilles b, Nitza Ilan d, Stefan H. Heinemann c,
Dalia Gordon d, Andre Menez b, Jordi Molgo a
a Laboratoire de Neurobiologie Cellulaire et Moleculaire,
C.N.R.S., 91198 Gif-sur-Yvette Cedex, Franceb Departement d’Ingenierie et d’Etudes des Proteines,
C.E.N./Saclay, 91191 Gif sur Yvette, Francec Research Unit Molecular and Cellular Biophysics, Medical
Faculty of the Friedrich Schiller University Jena, Germanyd Department of Plant Sciences, Tel-Aviv University,
Tel-Aviv, Israel
E-mail address: [email protected] (J. Barbier)
d-Conotoxin EVIA (d-EVIA), isolated from the west-African gasteropod Conus ermineus venom, contains 32amino acid residues and a six cysteine/four loop frameworksimilar to that of previously described conopeptides of the O-superfamily, i.e., x-, d-, lO-, and j-conotoxins. However, itdisplays low sequence homology with the latter conotoxins.
Native and chemically synthesized d-EVIA inhibit volt-age-sensitive Na+ channel inactivation with unique tissuespecificity upon binding to receptor site-6 of neuronalNa+ channels as detected in binding studies with rat brainsynaptosomes. Using amphibian myelinated axons andspinal neurons, we demonstrate that d-EVIA increasesthe duration of action potentials by inhibiting Na+ channelinactivation, and enhances nerve terminal excitability andsynaptic efficacy at the neuromuscular junction, but doesnot affect directly-elicited skeletal muscle action potentials.
The neuronal-selective property of d-EVIA has beenconfirmed by showing that a fluorescent derivative of d-EVIA labels motor nerve endings but not skeletal musclefibers. Moreover, in a heterologous expression system, d-EVIA inhibits inactivation of rat neuronal Na+ channelsubtypes (rNaV1.2a, rNaV1.3 and rNaV1.6), but does notaffect rat skeletal (rNaV1.4) nor human cardiac muscle(hNaV1.5) Na+ channel subtypes. d-EVIA, in the rangeof concentrations used, is the first conotoxin found to affectneuronal Na+ channels without acting on Na+ channels ofskeletal and cardiac muscles.
Hence, it is a unique tool for discriminating voltage-sensitive Na+ channel subtypes, and it may serve as a leadto design new drugs adapted to treat diseases characterizedby defective nerve conduction.
doi:10.1016/j.jphysparis.2005.12.020
Functional study of SG2Na by siRNA technique
Marion Benoist, Stephane Gaillard, Benedicte Dargent,
Francis Castets
INSERM UMR641, Institut Jean-Roche, Faculte de
Medecine-Nord, 13916 Marseille Cedex 20, France
E-mail address: [email protected](M. Benoist)
In neurons, scaffolding proteins play a crucial role in theestablishment, maintenance and structure of dendriticspines. These proteins are also involved in many post-synaptic signaling pathways. In mammals, the threemembers of the striatin family (striatin, SG2NA, zinedin)constitute a new group of scaffolding proteins specificallyexpressed in dendritic spines. Information concerning thephysiological role of the striatin family is beginning toemerge. First, we have shown that striatin expression isimportant for both dendritic growth in cultured rat embry-onic motoneurons and for the control of motor function inadult rats. Second, striatin and SG2NA have been proposedto be regulatory subunit of proteins phosphatase 2A. At themolecular level, each protein of the striatin family sharesidentical protein–protein interactions domains: from theN- to the C-termini, a caveolin-binding domain, a coiled-coil structure a Ca2+/calmodulin-binding domain and alarge WD-repeat-domain. To precise the implication ofthese proteins in signaling and trafficking in neurons, weused siRNA technique to inhibit SG2NA expression.
By semi-quantitative immunoblotting, we demonstratedthat the selected siRNAs specifically and dramaticallyinhibited the exogenous expression of SG2NA. This effectwas independent of the type of siRNA expressing vectorsand was observed in different cell types (COS-7, N2a,B104 and HEK). To visualize siRNA expressing cells, weconstructed bi-cystronic vectors expressing EGFP-Actinand siRNA. These vectors allowed us to observe a robustdecrease in SG2NA expression in cultured hippocampalneurons. SG2NA inhibition was found to alter neuronalsurvival, presumably by apopototic caspase dependentphenomenon. Thus, we concluded that SG2NA (andpotentially other striatin family members) is probablyinvolved in neuronal survival.
doi:10.1016/j.jphysparis.2005.12.021
Antagonistic effect of calcium permeating pathways
on embryonic Xenopus laevis neuronal differentiationFrancis-Olivier Tchikaya, Pascal Benquet,
Georgette Bonnec, Yves Pichon, Daniel Boujard,
Francois Tiaho
Equipe TDNX—UMR 6026, Universite Rennes 1,
35042 Rennes Cedex, France
E-mail address: [email protected] (P. Benquet)