Molecular and functional characterization of voltage-gated sodium channel variants from Drosophila melanogaster

Abstract

Extensive alternative splicing and RNA editing have been documented for the transcript of DmNa V (formerly para), the sole sodium channel gene in Drosophila melanogaster. However, the functional consequences of these post-transcriptional modifications are not well understood. In this study we isolated 64 full-length DmNa V cDNA clones from D. melanogaster adults. Based on the usage of 11 alternative exons, 64 clones could be grouped into 29 splice types. When expressed in Xenopus oocytes, 33 DmNa V variants generated sodium currents large enough for functional characterization. Among these variants, DmNa V 5-1 and DmNa V 7-1 channels activated at the most hyperpolarizing potentials, whereas DmNa V 1-6 and DmNa V 19 channels activated at the most depolarizing membrane potentials. We identified an A-to-I editing event in DmNa V 5-1 that is responsible for its uniquely low-voltage-dependent activation. The wide range of voltage dependence of gating properties exhibited by DmNa V variants represents a rich resource for future studies to determine the role of DmNa V in regulating sodium channel gating, pharmacology, and neuronal excitability in insects.

Drosophila as a Model for Epilepsy:bssIs a Gain-of-Function Mutation in the Para Sodium Channel Gene That Leads to Seizures

“…Electrophysiology of heterologously expressed para Na 1 channels was as described previously Olson et al 2008). A DmNa v 1-1 L1699F cDNA subcloned into the pGH19 expression vector was linearized with NotI and transcribed with T7 polymerase (mmESSAGE mmACHINE kit, Ambion).…”

Identification of ion channel genes in the Acyrthosiphon pisum genome

“…Insect VGSCs are presumed to gain heterogeneity and functional diversity by extensive alternative splicing (Olson et al, 2008). Nine such splicing sites have been identified in para and its orthologues to date; seven exons, a, b, i, j, e, f, h, are optional and form parts of the intracellular linkers of mature channel proteins, whereas exons c/d and l/k are mutually exclusive and are situated in the transmembrane regions.…”

Alternative splicing of para-sodium channel .ALPHA.-subunit genes from diamondback moth strains with different sensitivity to a pyrethroid

“…Tan et al 14) reported that alternative splicing generates spliced variants with different sensitivity to pyrethroid in B. germanica; the channel variant containing a mutually exclusive exon G2 was 100-fold less sensitive to deltamethrin than that containing exon G1. Olson et al 17) isolated 64 full-length sodium channel spliced variants from D. melanogaster and expressed in Xenopus oocytes. They showed that DmNav5-1 and DmNav7-1 channels were activated at the most hyperpolarizing potentials, whereas DmNav1-6 and DmNav19 channels were activated at the most depolarizing membrane potentials.…”