Functional analysis reveals ionotropic GABA receptor subunit RDL is a target site of ivermectin and fluralaner in the yellow fever mosquito, Aedes aegypti

Abstract

BACKGROUND: Ionotropic γ-aminobutyric acid (iGABA) receptors are involved in various physiological activities in insects, including sleep, olfactory memory, movement, and resistance to viruses. Ivermectin and fluralaner can disturb the insect nervous system by binding to iGABA receptors, and are therefore an effective means for controlling insect pests. However, the molecular mechanisms underlying the insecticidal effect of both the compounds on Aedes. aegypti remain unexplored.RESULTS: In this study, we investigated the spatiotemporal expression profile of Ae. aegypti RDL (Ae-RDL), a subunit of iGABA receptor. RDL dsRNA suppressed the expression of Ae-RDL mRNA in Ae. aegypti larvae and adult by 60% and 50.67%, resepectly. However, the physiology of Ae. aegypti larvae was not significantly affected. The mortality of Ae. aegypti larvae and adult females subjected to Ae-RDL knockdown significantly decreased after exposure to ivermectin and fluralaner. Additionally, Ae-RDL was cloned into Xenopus laevis oocytes and characterized using the two-electrode voltage-clamp method. The inward current was induced by GABA binding to the functional Ae-RDL homomeric receptors at a median effective concentration (EC 50 ) of 100.4 ± 59.95 ∼M (n > 3). The significant inhibitory effect of ivermectin and fluralaner on inward current indicated that both insecticides exerted a significant antagonistic effect on Ae-RDL. However, ivermectin also showed strong agonistic as well as weak activation effects on Ae-RDL. These contrasting effects of ivermectin on Ae-RDL depended on ivermectin concentration. CONCLUSION: Our study revealed that Ae-RDL subunit is a target of ivermectin and fluralaner, providing new insights into the insecticidal mechanism of both compounds in Ae. aegypti.

Effect of Fluralaner on the biology, survival, and reproductive fitness of the Neotropical malaria vector Anopheles aquasalis

“…The modulator targets GABA, ionotropic receptors, in which the localization site of the isoxazoline molecules are located and have different locations in particular insects, including mosquitoes (41)(42)(43). The mechanisms that allow understanding of the interference in the vectors' physiological activities due to the drug's action on the nervous system are still being explored (44).…”

“…Many insecticides act on the developmental stages of the mosquito vector life, interfering with its ability to reproduce (41,54), locomotion (44), vectorial capacity, and other factors that regulate the transmission of diseases (55,56). Ivermectin in sub-lethal dosages decreased the reproductive ability of An.…”

Can Essential Oils Be a Natural Alternative for the Control of Spodoptera frugiperda? A Review of Toxicity Methods and Their Modes of Action

“…These antecedents allow us to suppose that the bioactivity of the EOs observed on S. frugiperda could be due, in part, to the effect of these compounds on GABA. Nevertheless, there are few studies on the specific mode of action and the expression of genes associated with this complex [ 125 , 126 , 127 ]. Both essential oils and synthetic insecticides act as non-competitive allosteric modulators of GABARs by binding to them and maintaining a constant flow of chloride ions into the cell, thus keeping the nervous system in permanent excitement [ 40 , 101 , 113 , 122 , 128 , 129 ].…”

Impact of Ae-GRD on Ivermectin Resistance and Its Regulation by miR-71-5p in Aedes aegypti

“…In Ae. aegypti , RDL was targeted by ivermectin and florellan [ 10 ]. When expressed in Xenopus laevis oocytes, RDL formed pentameric anion-selective channels.…”