Trapping of ivermectin by a pentameric ligand-gated ion channel upon open-to-closed isomerization

Abstract

Ivermectin (IVM) is a broad-spectrum anthelmintic drug used to treat human parasitic diseases like river blindness and lymphatic filariasis. By activating invertebrate pentameric glutamate-gated chloride channels (GluCl receptors; GluClRs), IVM induces sustained chloride influx and long-lasting membrane hyperpolarization that inhibit neural excitation in nematodes. Although IVM activates the C. elegans heteromeric GluClα/β receptor, it cannot activate a homomeric receptor composed of the C. elegans GluClβ subunits. To understand this incapability, we generated a homopentameric α7-GluClβ chimeric receptor that consists of an extracellular ligand-binding domain of an α7 nicotinic acetylcholine receptor known to be potentiated by IVM, and a chloride-selective channel domain assembled from GluClβ subunits. Application of IVM prior to acetylcholine inhibited the responses of the chimeric α7-GluClβR. Adding IVM to activated α7-GluClβRs, considerably accelerated the decline of ACh-elicited currents and stabilized the receptors in a non-conducting state. Determination of IVM association and dissociation rate constants and recovery experiments suggest that, following initial IVM binding to open α7-GluClβRs, the drug induces a conformational change and locks the ion channel in a closed state for a long duration. We further found that IVM also inhibits the activation by glutamate of a homomeric receptor assembled from the C. elegans full-length GluClβ subunits.

GluClR-mediated inhibitory postsynaptic currents reveal targets for ivermectin and potential mechanisms of ivermectin resistance

“…Our IPSC and single channel data suggest that the potentiating effect of IVM at GluClRs requires several minutes to stabilise [35]. This relatively long delay could reflect the slow binding of IVM directly from the aqueous solution or slow IVM-induced conformational effects at GluClRs once bound [46, 47]. Alternatively, it may reflect a slow accumulation rate of IVM into the membrane, possibly coupled with a slow lateral diffusion rate within the membrane that controls its access to receptor binding sites.…”

Modeling of SARS-CoV-2 Treatment Effects for Informed Drug Repurposing

“…In addition, IVM interacts with nAChR (IC 50 156 nM) ( Degani-Katzav et al, 2017 ). It has been hypothesized that inhibition of nAChR downregulates angiotensin-converting enzyme 2 (ACE2) expression and thus reduces the points of entry for SARS-CoV-2 ( Oakes et al, 2018 ).…”

Mutational Analysis at Intersubunit Interfaces of an Anionic Glutamate Receptor Reveals a Key Interaction Important for Channel Gating by Ivermectin

“…Others also reported irresponsiveness to Glu in human embryonic kidney (HEK) cells transfected with the wild type GluClβ subunit alone (Slimko et al, 2002; Frazier et al, 2013; Daeffler et al, 2014). Most recently, we succeeded to obtain responses of a few hundred picooamperes in CHO cells transfected with the WT GluClβ subunit alone using the X-tremeGENE HP DNA Transfection Reagent (Roche Life Science); but, in this case, we challenged the cells with 100 mM Glu, and only 4 of 46 cells responded (Degani-Katzav et al, 2017). In contrast, CHO cells co-transfected with both WT GluCl α and β subunits commonly display robust responses to both Glu and IVM (Degani-Katzav et al, 2016).…”