Nicotinic acetylcholine receptors nicotinic receptor molecular chaperones and mechanisms of insecticide action

The focus of this research proposal is an important class of neurotransmitter receptor, the nicotinic acetylcholine receptors (nAChRs), which are target sites for two major classes of insecticide (neonicotinoids and spinosad). As with almost all classes of insecticides, major problems of resistance have now developed in insect field populations. A particular emphasis of this research proposal is to elucidate the mechanism of action of spinosad and to explore mechanisms of resistance to this insecticide. In parallel, studies will be undertaken to investigate the role of proteins involved in generating functional nAChRs. A goal of this second aspect of the proposed research project is to facilitate research aimed at elucidating the pharmacological diversity of insect nAChRs. Insect nAChRs are closely related to nAChRs expressed in the nervous system of vertebrates. Such receptors in humans have been implicated in disorders such as Alzheimer's disease and schizophrenia. Indeed, some of the research proposed in this application will focus on mammalian nAChRs and it is expected that the research findings may, in the longer term, have relevance to research aimed at discovery of drugs targeting human nAChRs.

Nicotinic acetylcholine receptors (nAChRs) are pentameric neurotransmitter-gated ion channels. In humans, nAChRs are increasingly being seen as important targets for therapeutic drug discovery. In insects and other pest species, nAChRs are the target sites for two major classes of pesticide (neonicotinoids and spinosad). For both neonicotinoids and spinosad, problems of resistance are causing severe problems in the control of agriculturally important insect pests. A central goal of this application is to examine the hypothesis that resistance to spinosad in a major pest species, Western flower thrips (WFT), Frankliniella occidentalis is a consequence of target-site resistance. This will be achieved by cloning and sequencing the spinosad-sensitive nAChR subunit homologues from WFT. This will be complemented by studies conducted with recombinant nAChRs which will examine the mechanism of action of macrocyclic lactones such as spinosad and ivermectin. In addition, we will examine the role of nAChR-selective molecular chaperone proteins in modulating the functional expression of nAChRs. We aim to improve understanding of the recently identified class of nAChR-selective chaperone proteins which we hope will also help to circumvent long-standing problems associated with heterologous expression of some insect nAChRs.