Cofactor-enabled functional expression of fruit fly, honeybee, and bumblebee nicotinic receptors reveals picomolar neonicotinoid actions

The difficulty of achieving robust functional expression of insect nicotinic acetylcholine receptors (nAChRs) has hampered our un-derstanding of these important molecular targets of globally deployed neonicotinoid insecticides at a time when concerns have grown regarding the toxicity of this chemotype to insect pollina-tors. We show that thioredoxin-related transmembrane protein 3 (TMX3) is essential to enable robust expression in Xenopus laevis oocytes of honeybee (Apis mellifera) and bumblebee (Bombus ter-restris) as well as fruit fly (Drosophila melanogaster) nAChR het-eromers targeted by neonicotinoids and not hitherto robustly expressed. This has enabled the characterization of picomolar tar-get site actions of neonicotinoids, findings important in under-standing their toxicity.