Etude des sous-unités auxiliaires du canal sodium dépendant du potentiel chez l’insecte : approches moléculaires, électrophysiologiques et pharmacologiques (Thèse de Doctorat d'Université)

Abstract

Voltage-gated sodium (Nav) channel is a crucial molecular component of the cellular excitability. It represents a target of choice for neurotoxic insecticides used in pest control. Pyrazoline-type insecticide interacts with the main Nav channel subunit with a preference for its inactivated state. A recent study showed that auxiliary subunits of Drosophila melanogaster modified this conformation. However, little information is available concerning the role and the regulation of these auxiliary subunits. The objectives of this thesis were to characterize the auxiliary subunits of the American cockroach Periplaneta americana by molecular, electrophysiological and pharmacological approaches, in order to specify their functions. The first part of this work concerns the neuronal TEH1 subunit. Two variants, PaTEH1A and PaTEH1B resulting from an intron retention modifying only the C-terminal extremity, were cloned. Using the heterologous expression system Xenopus oocytes and the two microelectrodes voltage clamp technique, we highlighted that the C-terminal extremity was involved in the modulation of Nav channels electrophysiological and pharmacological properties. The second part concerns the discovery of other auxiliary subunits. We identified several variants resulting from alternative splicing events (2 variants for PaTipE and 4 for PaTEH2). Altogether, our results indicate that auxiliary subunits are diverse and play an important role in the modulation of Na+ current and should be considered to improve pharmacological studies