Diversity of Insect Nicotinic Acetylcholine Receptor Subunits

Nicotinic acetylcholine receptors (nAChRs) are ligand‑gated ion channels that mediate fast synaptic transmission in the insect nervous system and are targets of a major group of insecticides, the neonicotinoids. They consist of five subunits arranged around a central ion channel. Since the subunit composition determines the functional and pharmacological properties of the receptor the presence of nAChR families comprising several subunit‑encoding genes provides a molecular basis for broad functional diversity. Analyses of genome sequences have shown that nAChR gene families remain compact in diverse insect species, when compared to their nematode and vertebrate counterparts. Thus, the fruit fly (Drosophila melanogaster), malaria mosquito (Anopheles gambiae), honey bee (Apis mellifera), silk worm (Bombyx mori) and the red flour beetle (Tribolium castaneum) possess 10‑12 nAChR genes while human and the nematode Caenorhabditis elegans have 16 and 29 respectively. Although insect nAChR gene families are amongst the smallest known, receptor diversity can be considerably increased by the posttranscriptional processes alternative splicing and mRNA A‑to‑I editing which can potentially generate protein products which far outnumber the nAChR genes. These two processes can also generate species‑specific subunit isoforms. In addition, each insect possesses at least one highly divergent nAChR subunit which may perform species‑specific functions.

Corresponding Author: Andrew K. Jones—MRC Functional Genomics Unit, Department
of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.
Email: andrew.jones@dpag.ox.ac.uk
Source: Insect Nicotinic Acetylcholine Receptors, edited by Steeve Hervé Thany.