The nicotinic acetylcholine receptor gene family of the malaria mosquito, Anopheles gambiae

Nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission in the insect nervous system and are targets of widely selling insecticides. We have identified the nAChR gene family from the genome of the malaria mosquito vector, Anopheles gambiae, to be the second complete insect nAChR gene family described following that of Drosophila melanogaster. Like Drosophila, Anopheles possesses 10 nAChR subunits with orthologous relationships evident between the two insects. Interestingly, the Anopheles orthologues of Dβ2 and Dβ3 possess the vicinal cysteines that define α subunits. As with Dα4 and Dα6, the Anopheles orthologues are alternatively spliced at equivalent exons. Reverse transcription-polymerase chain reaction analysis shows that RNA A-to-I editing sites conserved between Dα6 of Drosophila and α7-2 of the tobacco budworm, Heliothis virescens, are not shared with the equivalent nAChR subunit of Anopheles. Indeed, RNA-editing sites identified in functionally significant regions of Dβ1, Dα5, and Dα6 are not conserved in the mosquito orthologues, indicating considerable divergence of RNA molecules targeted for editing within the insect order Diptera. These findings shed further light on the diversity of nAChR subunits and may present a useful basis for the development of improved malaria control agents by enhancing our understanding of a validated mosquito insecticide target.