Odorant receptor modulation: Ternary paradigm for mode of action of insect repellents

The modulation of insect behavior for the purpose of controlling the spread of infectious diseases has been the task of a few insect repellents for which the mechanistic modes of action on odorant receptors (ORs) are unclear. Here, we study the effects of the repellents DEET and IR3535, and a novel OR co-receptor (Orco) agonist on odorant-evoked currents in Xenopus oocytes expressing two subtypes of Aedes aegypti ORs (AaORs). We show that DEET and IR3535 behave as insurmountable antagonists of ORs, and that modulation of OR activity is not restricted to antagonism and agonism, but also includes synergism. This knowledge of the molecular mechanisms underlying OR blockade, activation and hyperactivation will be fundamental to the development of novel strategies for the control of mosquito behavior.

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► DEET and IR3535 are insurmountable antagonists of insect ORs.
► DEET and IR3535 do not affect Orco activation.
► Orco agonist reveals functional homo oligomerization of Orco.
► Orco activation by agonist is enhanced in the presence of odorant.
► ORs complexes exhibit multiple conformational states.