Cloning and Functional Characterisation of Two Novel Nicotinic Acetylcholine Receptor α Subunits from the Insect Pest Myzus persicae

Abstract

Abstract:Nicotinic acetyicholine receptors play a major role in excitatory neurotransmission in insect CNSs and constitute an important target for insecticides. Here, we report the isolation and functional characterisation of two cDNAs encoding nicotinic acetyicholine receptor a subunits from a major insect pest, the peach-potato aphid Myzus persicae. These two subunits, termed Mpal and Mpa2, are respective structural homologues of the Drosophila Da2/Schistocerca gregaria aLl a-subunit pair and the Drosophila ALS a subunit. Xenopus oocyte expression confirmed that each Myzus subunit can form functional acetylcholine-or nicotine-gated channels. However, some electrophysiological and pharmacological properties of the Myzus subunits were distinct from those encoded by the corresponding Drosophila subunits. Coexpression of the Myzus subunits with the chick /32 subunit revealed other differences from the Drosophila system, as only very limited potentiation of agonist-induced currents was observed with Mpa2 and none with Mpal. Available data therefore indicate that structurally homologous insect nicotinic acetylcholine receptor a subunits from different species can exhibit distinctive physiological and pharmacological characteristics.

Five nicotinic acetylcholine receptor subunits from the Morotoge shrimp,Pandalopsis japonica: cloning, tissue distribution, and functional expression inXenopusoocytes

“…Successful functional expression of α1 and α2 members has been reported in heterologous systems. The subunits Dα2 (the fruit fly D. melanogaster), Sgα1 (the locust S. gregaria), and Mpα1 and Mpα2 (the aphid M. persicae) formed homomeric nAChRs when expressed in Xenopus oocytes (Amar et al1995;Marshall et al 1990;Sawruk et al 1990;Sgard et al 1998). These results indicate that α1 and α2 group members are able to form functional channels as homopentamers, whereas α3 and α4 subgroup members are not, despite their sequence similarity (Figure 1).…”

“…Although the Sgα1 subunit from the locust Schistocerca gregaria and Mpα1 and Mpα2 from the aphid Myzus persicae formed homopentameric channels when expressed in Xenopus laevis oocytes (Amar et al 1995;Marshall et al 1990;Sgard et al 1998). Invertebrate subunits have failed to form heteromeric functional channels, which is contrast to vertebrate nAChRs.…”

The invertebrate pharmacology of insecticides acting at nicotinic acetylcholine receptors

“…The Mpα1 and Dmα2 subunits share 94% amino acid sequence in the N-terminal (which contains the agonist binding domain), however whereas Dmα2 interacts with IMI, Mpα1 does not. 76,77) Therefore, the weight of evidence clearly implies that hemipteran insects display unique neonicotinoid pharmacology when compared to other insect orders.…”

“…This may be expected given that unique nAChR subunits have been identified in the pea aphid genome, together with the fact that differences in the pharmacology occurs even for highly species conserved nAChR subunits. 76,77) Therefore, care should be exercised when comparing neonicotinoid profiles across insect orders. Although the nAChR subunit pentamer combination that forms a neonicotinoid insecticidal-relevant binding site in Hemiptera (or any invertebrate) has not yet been resolved, the fact that FRC M. persicae displays significant levels of resistance to all commercialized neonicotinoids implies that the Mpβ1 subunit is an essential component.…”

A review of experimental techniques used for the heterologous expression of nicotinic acetylcholine receptors

“…In addition, Xenopus oocytes have been used successfully to examine nAChR subunits cloned from several invertebrate species, including the aphid Myzus persicae [89], the brown planthopper Nilaparvata lugens [90], the fruit fly Drosophila melanogaster [69,91], the locust Schistocerca gregaria [92] and the nematode Caenorhabditis elegans [93,94]. Frustratingly, the heterologous expression of invertebrate nAChRs has proved to be extremely difficult [59,95] and, in several instances, this has often been achieved only by co-expression with vertebrate nAChR subunits [65,91,96,97].…”