An L319F mutation in transmembrane region 3 (TM3) selectively reduces sensitivity to okaramine B of the <i>Bombyx mori</i>  <scp>l</scp>-glutamate-gated chloride channel

Furutani, Shogo; Okuhara, Daiki; Hashimoto, Anju; Ihara, Makoto; Kai, Kenji; Hayashi, Hideo; Sattelle, David B.; Matsuda, Kazuhiko

doi:10.1080/09168451.2017.1359487

Cited by 7 publications

(6 citation statements)

References 17 publications

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“…1). As predicted, a very recent publication has indicated that activation by IVM was strongly reduced and that activation by okaramine B, an insecticidal indole alkaloid, was completely abolished in the silkworm (Bombyx mori) GluCl containing an L319F mutation, which is equivalent to the L315F mutation in the Musca GluCl (Furutani et al, 2017). More importantly, we have shown in the present study that the L315F mutation has opposite impacts on the selectivity of fluralaner and IVM for GluCls.…”

Section: Discussionsupporting

confidence: 85%

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

Nakata¹,

Fuse²,

Yamato³

et al. 2017

Mol Pharmacol

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Fluralaner (Bravecto) is a recently marketed isoxazoline ectoparasiticide. This compound potently inhibits GABA-gated chloride channels (GABACls) and less potently glutamate-gated chloride channels (GluCls) in insects. The mechanism underlying this selectivity is unknown. Therefore, we sought to identify the amino acid residues causing the low potency of fluralaner toward GluCls. We examined the fluralaner sensitivity of mutant housefly () GluCls in which amino acid residues in the transmembrane subunit interface were replaced with the positionally equivalent amino acids of GABACls. Of these amino acids, substitution of an amino acid (Leu315) in the third transmembrane region (TM3) with an aromatic amino acid dramatically enhanced the potency of fluralaner in the GluCls. In stark contrast to the enhancement of fluralaner potency, this mutation eliminated the activation of currents and the potentiation but not the antagonism of glutamate responses that are otherwise all elicited by the macrolide parasiticide ivermectin (IVM). Our findings indicate that the amino acid Leu315 in GluCls plays significant roles in determining the selectivity of fluralaner and IVM for these channels. Given the high sequence similarity of TM3, this may hold true more widely for the GluCls and GABACls of other insect species.

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Section: Discussionsupporting

confidence: 85%

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

Nakata¹,

Fuse²,

Yamato³

et al. 2017

Mol Pharmacol

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“…In addition, two other mutations V327G (adjacent to the important G326 residue) and L329F were also found in GluCl3 of a strain exhibiting an around 500‐fold resistance ratio (RR). L329 corresponds to M345 of C. elegans GluClα, a residue predicted to be involved in ivermectin binding; 7 while two substitutions at a position equivalent to L329F (L315F and L319F in GluCl of M. domestica and Bombyx mori , respectively) also showed reduced sensitivity to ivermectin 42,43 . However, none of these recently identified mutations (I321T, V327G and L329F) have been functionally validated.…”

Section: Introductionmentioning

confidence: 99%

“…L329 corresponds to M345 of C. elegans GluCl⊍, a residue predicted to be involved in ivermectin binding; 7 while two substitutions at a position equivalent to L329F (L315F and L319F in GluCl of M. domestica and Bombyx mori, respectively) also showed reduced sensitivity to ivermectin. 42,43 However, none of these recently identified mutations (I321T, V327G and L329F) have been functionally validated. Characterizing the properties of these mutations could help in understanding the macrocyclic lactone resistance mechanisms in T. urticae and, in the long term, might aid in designing effective pest management strategies.…”

Section: Introductionmentioning

confidence: 99%

Untangling a Gordian knot: the role of a GluCl3 I321T mutation in abamectin resistance in Tetranychus urticae

Xue

Mermans

Papapostolou

et al. 2020

Pest Management Science

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BACKGROUND The cys‐loop ligand‐gated ion channels, including the glutamate‐gated chloride channel (GluCl) and GABA‐gated chloride channel (Rdl) are important targets for drugs and pesticides. The macrocyclic lactone abamectin primarily targets GluCl and is commonly used to control the spider mite Tetranychus urticae, an economically important crop pest. However, abamectin resistance has been reported for multiple T. urticae populations worldwide, and in several cases was associated with the mutations G314D in GluCl1 and G326E in GluCl3. Recently, an additional I321T mutation in GluCl3 was identified in several abamectin resistant T. urticae field populations. Here, we aim to functionally validate this mutation and determine its phenotypic strength. RESULTS The GluCl3 I321T mutation was introgressed into a T. urticae susceptible background by marker‐assisted backcrossing, revealing contrasting results in phenotypic strength, ranging from almost none to 50‐fold. Next, we used CRISPR‐Cas9 to introduce I321T, G314D and G326E in the orthologous Drosophila GluCl. Genome modified flies expressing GluCl I321T were threefold less susceptible to abamectin, while CRISPRed GluCl G314D and G326E flies were lethal. Last, functional analysis in Xenopus oocytes revealed that the I321T mutation might reduce GluCl3 sensitivity to abamectin, but also suggested that all three T. urticae Rdls are affected by abamectin. CONCLUSION Three different techniques were used to characterize the role of I321T in GluCl3 in abamectin resistance and, combining all results, our analysis suggests that the I321T mutation has a complex role in abamectin resistance. Given the reported subtle effect, additional synergistic factors in resistance warrant more investigation. © 2020 Society of Chemical Industry

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“…Subsequent studies showed that the GluCl target site actions of 4 okaramines (A, B, Q, and B‐H2, see Figure 2) agreed well with their insecticidal potency. [ 50 ] In addition to targeting insect GluCls, okaramine B also targets GluCls of the tick Ixodes scapularis . [ 51 ] When compared to ivermectin, okaramines have an even more attractive specificity profile, being inactive against insect GABA receptors and against human GABA or glycine receptors.…”

Section: Glucl Ligand (Ivermectin) Transitions From An Animal Health mentioning

confidence: 99%

Turning a Drug Target into a Drug Candidate: A New Paradigm for Neurological Drug Discovery?

2020

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The conventional paradigm for developing new treatments for disease mainly involves either the discovery of new drug targets, or finding new, improved drugs for old targets. However, an ion channel found only in invertebrates offers the potential of a completely new paradigm in which an established drug target can be re‐engineered to serve as a new candidate therapeutic agent. The L‐glutamate‐gated chloride channels (GluCls) of invertebrates are absent from vertebrate genomes, offering the opportunity to introduce this exogenous, inhibitory, L‐glutamate receptor into vertebrate neuronal circuits either as a tool with which to study neural networks, or a candidate therapy. Epileptic seizures can involve L‐glutamate‐induced hyper‐excitation and toxicity. Variant GluCls, with their inhibitory responses to L‐glutamate, when engineered into human neurons, might counter the excitotoxic effects of excess L‐glutamate. In reviewing recent studies on model organisms, it appears that this approach might offer a new paradigm for the development of candidate therapeutics for epilepsy.

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An L319F mutation in transmembrane region 3 (TM3) selectively reduces sensitivity to okaramine B of the Bombyx mori l-glutamate-gated chloride channel

Cited by 7 publications

References 17 publications

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

Untangling a Gordian knot: the role of a GluCl3 I321T mutation in abamectin resistance in Tetranychus urticae

Turning a Drug Target into a Drug Candidate: A New Paradigm for Neurological Drug Discovery?

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