The effects of insecticides on two splice variants of the glutamate-gated chloride channel receptor of the major malaria vector, Anopheles gambiae

Between half to one million people die annually from malaria. Anopheles gambiae mosquitos are major malaria vectors. Unfortunately, resistance to currently used A. gambiae control agents has emerged, creating a demand for novel control measures. The pentameric glutamate-gated chloride channel receptors (GluClRs) expressed in the muscle and nerve cells of these organisms are a potentially important biological target for malaria control. The pharmacological properties of Anophiline GluClRs are, however, largely unknown. Accordingly, we compared the efficacy of four insecticides (lindane, fipronil, picrotoxin and ivermectin) on two A. gambiae GluClR splice variants with the aim of providing a molecular basis for designing novel anti-malaria treatments.The A. gambiae GluClR b1 and c splice variants were expressed homomerically in Xenopus laevis oocytes and studied using two-electrode voltage-clamp.The b1 and c GluClRs were activated with similar potencies by glutamate and ivermectin. Fipronil was more potent than picrotoxin and lindane at inhibiting glutamate and ivermectin-gated currents. Importantly, b1 GluClRs exhibited a reduced sensitivity to picrotoxin and lindane. They also recovered from these effects to a greater extent than c GluClRs.We show that the two splice variant subunits exhibit differential sensitivities to multiple, structurally divergent insecticides. This is achieved without accompanying changes in the sensitivity to the endogenous neurotransmitter, glutamate, implying that drug resistance may be caused by alterations in relative subunit expression levels without affecting physiological function. Finally, our results strongly suggest that it should be feasible to develop novel subunit-specific pharmacological agents