Nicotinic acetylcholine receptors in the synganglion of the tick Ixodes ricinus: Functional characterization using membrane microtransplantation

Abstract

Nicotinic acetylcholine receptors are an important class of excitatory receptors in the central nervous system of arthropods. In the ticks Ixodes ricinus , the functional and pharmacological properties of nicotinic receptors located in their neurons are still unknown. The objective of this study was to characterize the pharmacological properties of tick nicotinic receptors using membrane microtransplantation in Xenopus laevis oocytes and two-electrodes voltage clamp method. The membranes microtransplanted were extracted from the tick synganglion. We found that oocytes microtransplanted with tick synganglion membranes expressed nicotinic acetylcholine receptor subtypes which were activated by acetylcholine (1 mM) and nicotine (1 mM). Currents induced by pressure application of acetylcholine and nicotine were diminished by 10 nM α-bungarotoxin and methyllycaconitine, suggesting that they expressed two subtypes of nicotinic receptors, α-bungarotoxin-sensitive and -insensitive, respectively. In addition, we found that nicotine receptors expressed in the synganglion membranes were poorly sensitive to the neonicotinoid insecticides clothianidin (CLT), imidacloprid (IMI), acetamiprid (ACE) and thiamethoxam (TMX), in agreement with their lack of activity as acaricides. Interestingly, current amplitudes were strongly potentialized in the presence of 1 μM PNU-120596. CLT was more active as an agonist than IMI, TMX and ACE. Finally, we demonstrated that microtransplantation of purified membrane from the tick synganglion can be a valuable tool for the development and screening of compounds targeting tick nicotinic acetylcholine receptor subtypes.

Transcriptome of the synganglion in the tick Ixodes ricinus and evolution of the cys-loop ligand-gated ion channel family in ticks

“…For arachnids, the first functional characterization of an alpha-type receptor was done for the brown dog tick Rhipicephalus sanguineus , but in vitro expression patterns were unreliable [ 18 ]. In the tick I. ricinus , the microtransplatation of synganglion membranes in oocytes of Xenopus levis allowed to express nicotinic acetylcholine receptors and to evaluate their sensitivity to insecticides [ 19 ], but insofar no cloning of alpha-type receptor has been reported for ticks. A GABA receptor was first identified in Drosophila melanogaster , the Rdl gene [ 20 ], whereas Rdl homologs were cloned in the ticks Dermacentor variabilis [ 21 ] and Rhipicephalus microplus [ 22 ] respectively.…”

The control of Hyalomma ticks, vectors of the Crimean–Congo hemorrhagic fever virus: Where are we now and where are we going?

“…This type of trap, which to our knowledge has never been tested on Hyalomma sp., could prove effective due to the hunting behavior of adults. The identification of new tick-specific targets, such as substances in their nervous system, may also allow the development of vaccines [ 202 ] or new acaricides that preserve non-target fauna [ 203 ], particularly in association with nanoparticles [ 58 ].…”

Transcriptome of the synganglion and characterization of the cys-loop ligand-gated ion channel gene family in the tickIxodes ricinus

“…For arachnids, the first functional characterization of an alpha-type receptor was done for the brown dog tick Rhipicephalus sanguineus , but in vitro expression patterns were unreliable 17 . In the tick I. ricinus , the microtransplatation of synganglion membranes in oocytes of Xenopus levis allowed to express nicotinic acetylcholine receptors and to evaluate their sensitivity to insecticides 18 , but insofar no cloning of alpha-type receptor has been reported for ticks. A GABA receptor was first identified in Drosophila melanogaster (the Rdl gene 19 , confering resistance to the insecticide dieldrin), whereas Rdl homologs were cloned in the ticks Dermacentor variabilis 20 and Rhipicephalus microplus 21 respectively.…”