Novel alternative splicing of GABA receptor RDL exon 9 from Laodelphax striatellus modulates agonist potency

Abstract

The resistance to dieldrin gene (RDL) encodes the primary subunit of the insect ionotropic γ -aminobutyric acid (GABA) receptor (GABAR), which is the target of phenylpyrazole and isoxazoline insecticides. The splice variants in exons 3 and 6 of RDL, which have been widely explored in many insects, modulate the agonist potency of the homomeric RDL GABAR and potentially play an important role in the development of insects. In the present study, four splice variants of exon 9 were identified in RDL of the small brown planthopper, Laodelphax striatellus (LsRDL), resulting in LsRDL-9a, LsRDL-9a', LsRDL-9b, and LsRDL-9c. LsRDL-9a has one more amino acid (E, glutamic acid) compared with LsRDL-9a', and LsRDL-9b lacked two amino acids and had seven different amino acids compared with LsRDL-9c. Two-electrode voltage-clamp recording on LsRDLs expressed in Xenopus oocytes showed that alternative splicing of exon 9 has significant impact on LsRDL sensitivity to the agonists GABA and β-alanine, whereas no significant difference was observed in the potencies of the non-competitive antagonists (NCAs) ethiprole and fluralaner on the splice variants. Our results suggest that alternative splicing of RDL exon 9 broadens functional capabilities of the GABAR in L. striatellus by influencing the action of GABA.

The cys‐loop ligand‐gated ion channel gene superfamilies of the cockroaches Blattella germanica and Periplaneta americana

“…7(B)). Alternative splicing of this exon has so far only been reported for the small brown planthopper, Laodelphax striatellus 59 . Exon 9 of Rdl in the genome and transcriptome of P. americana was not observed to have alternatively spliced variants.…”

“…7(A)). Such alternative splicing of this exon has only been reported once before for Laodelphax striatellus where four splice variants affected potency of the agonists GABA and β‐alanine 59 . Perhaps with the extra exon 9 influencing the action of GABA, the functional capabilities of the GABA receptor is broadened in B. germanica .…”

Distinct molecular targets for macrocyclic lactone and isoxazoline insecticides in the human louse: new prospects for the treatment of pediculosis

“…Likewise, Phh-RDL had one of the lowest EC 50 for GABA among described insect RDL receptors showing EC 50 varying between 5.43 +/- 0.02 µM in the brown planthopper Nilaparvata lugens [63] and 445 +/- 47 µM in the carmine spider mite Tetranychus cinnabarinus [61] with the exception of the RDL-2 subunit (2.4 +/- 0.3 µM) from the honey bee parasite mite Varroa destructor [51]. Similarly, spliced variant transcripts of GluCl and RDL subunits were found to give rise to functional channels in several insect species, thus increasing their receptor diversity [33, 56, 57, 60, 62, 64-66]. Here, we identified and characterized the first GluCl and GABACl receptors of human lice.…”

Synthesis and activity‐detection of photoswitchable ligands with fipronil to insect

“…Each oocyte was placed in a recording chamber that was perfused with a standard oocyte saline (SOS) solution [100 mmol L −1 sodium chloride (NaCl), 2 mmol L −1 potassium chloride (KCl), 1.8 mmol L −1 calcium chloride (CaCl 2 ), 1 mmol L −1 magnesium chloride (MgCl 2 ), and 5 mmol L −1 HEPES, pH 7.6] with a flow rate of 8–10 mL min −1 . GABA, dissolved in a SOS solution, was applied to activate expressed receptors in the oocyte for 5 s, at an interval of 85 s. Concentration‐response curves to determine the half maximal effective concentration (EC 50 ) were obtained by sequential application of increasing concentrations of GABA to homomeric Ls RDL channels expressed in oocyte 27 . Test compounds were initially dissolved in dimethyl sulfoxide (DMSO), and subsequently diluted using the SOS solution to the final concentration of DMSO less than 0.1% ( v/v ).…”