An electrophysiological preparation of<i>Ascaris suum</i>pharyngeal muscle reveals a glutamate-gated chloride channel sensitive to the avermectin analogue, milbemycin D

Rj, Martin

doi:10.1017/s0031182000084833

Cited by 88 publications

(55 citation statements)

References 13 publications

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“…One way worms die from ivermectin is as a result of starvation caused by the inhibition of pharyngeal pumping (21)(22)(23)(24). In light of this and previous studies it is clear that one of the genetic pathways leading -14) acts in neurons.…”

Section: Ivermectin Targets Three Members Of the Family Of Ivermectin-mentioning

confidence: 90%

The genetics of ivermectin resistance in Caenorhabditis elegans

Dent

Smith

Vassilatis

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

426

458

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The ability of organisms to evolve resistance threatens the effectiveness of every antibiotic drug. We show that in the nematode Caenorhabditis elegans, simultaneous mutation of three genes, avr-14, avr-15, and glc-1, encoding glutamate-gated chloride channel (GluCl) ␣-type subunits confers high-level resistance to the antiparasitic drug ivermectin. In contrast, mutating any two channel genes confers modest or no resistance. We propose a model in which ivermectin sensitivity in C. elegans is mediated by genes affecting parallel genetic pathways defined by the family of GluCl genes. The sensitivity of these pathways is further modulated by unc-7, unc-9, and the Dyf (dye filling defective) genes, which alter the structure of the nervous system. Our results suggest that the evolution of drug resistance can be slowed by targeting antibiotic drugs to several members of a multigene family. Ivermectin is used to treat numerous parasitic infections of humans, pets, and livestock (1). Treatment with ivermectin is the cornerstone of efforts to eradicate river blindness (onchocerciasis). However, reports of resistance to ivermectin in nematodes are increasingly common (2-4). Ivermectin also kills the nematode Caenorhabditis elegans at therapeutic concentrations, making C. elegans a useful model system in which to examine mechanisms of ivermectin toxicity and resistance. Ivermectin activates glutamate-gated chloride channels (GluCls) that contain ␣-type channel subunits (5-7). In C. elegans, ␣-type subunits are encoded by a family of genes including: glc-1 (encoding GLC-1͞GluCl␣1), avr-15 (encoding AVR-15͞GluCl␣2), and possibly other uncharacterized genes found in the genome sequence (5-8). Severe loss-of-function mutations in glc-1 or avr-15 do not make worms resistant to ivermectin (6, 7), either because GluCls are not physiologically important targets of ivermectin, or because multiple GluCl genes contribute independently to ivermectin sensitivity. To clarify the role of the GluCls in the nematocidal effects of ivermectin, we had screened for ivermectin-resistant mutants (6). Here we analyze the effects of these and other, previously characterized mutations on ivermectin sensitivity. We show that simultaneous mutation of three genes encoding GluCl ␣-type subunits confers high-level resistance to ivermectin. Our results suggest that the ability of ivermectin to target several members of a multigene family may decrease the rate at which resistance evolves. MethodsGenetics. Unless otherwise indicated the mutant alleles used were: avr-14(ad1302), avr-15(ad1051), gcl-1(pk54::Tc1), unc-7(e5), unc-9(e101), osm-1(ad1307), osm-5(ad1308), dyf-11(ad1303), and che-3(ad1306). avr-15(ad1051), glc-1(pk54::Tc1), unc-7(e5), and unc-9(e101) appear to be molecular nulls (refs. 6,7,and 18; T. Starich, personal communication). Ivermectin-resistant mutants were isolated in a screen for ivermectin resistance in an avr-15(ad1051) background by using the mutagen ethyl methanesulfonate as described (6). All strains were outcrossed twice with N2 ...

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Section: Ivermectin Targets Three Members Of the Family Of Ivermectin-mentioning

confidence: 90%

The genetics of ivermectin resistance in Caenorhabditis elegans

Dent

Smith

Vassilatis

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

426

458

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“…As no additional orthologs of IVM-sensitive channels were found in the B. malayi genome database, these proteins must represent the main putative target for IVM in this parasite based on data obtained in other species of nematodes (26)(27)(28). Identifying their anatomical localization in mf provides new insights to explain the pharmacological consequences of treatment of filariases with IVM.…”

Section: Discussionmentioning

confidence: 99%

Ivermectin disrupts the function of the excretory-secretory apparatus in microfilariae of Brugia malayi

Moreno

Nabhan

Solomon

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

148

141

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Ivermectin (IVM) is a broad-spectrum anthelmintic used in filariasis control programs. By binding to nematode glutamate-gated chloride channels (GluCls), IVM disrupts neurotransmission processes regulated by GluCl activity. IVM treatment of filarial infections is characterized by an initial dramatic drop in the levels of circulating microfilariae, followed by long-term suppression of their production, but the drug has little direct effect on microfilariae in culture at pharmacologically relevant concentrations. We localized Brugia malayi GluCl expression solely in a muscle structure that surrounds the microfilarial excretory-secretory (ES) vesicle, which suggests that protein release from the ES vesicle is regulated by GluCl activity. Consistent with this hypothesis, exposure to IVM in vitro decreased the amount of protein released from microfilariae. To better understand the scope of IVM effects on protein release by the parasite, three different expression patterns were identified from immunolocalization assays on a representative group of five microfilarial ES products. Patterns of expression suggest that the ES apparatus is the main source of regulated ES product release from microfilariae, as it is the only compartment that appears to be under neuromuscular control. Our results show that IVM treatment of microfilariae results in a marked reduction of protein release from the ES apparatus. Under in vivo conditions, the rapid microfilarial clearance induced by IVM treatment is proposed to result from suppression of the ability of the parasite to secrete proteins that enable evasion of the host immune system. filarial nematode | macrocyclic lactone | glutamate-gated chloride channels

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“…The antiparasitic effects of ivermectin (IVM) are known to be (i) paralysis of the pharyngeal muscle (Geary et al 1993;Martin 1996), and (ii) paralysis of the somatic muscle (Kass et al 1980;Boisvenue et al 1983;Holden-Dye et al 1988;Holden-Dye and Walker 1990). Attempts to elucidate the mode of action of IVM have therefore been focused on the effects of IVM on the neuromuscular system in nematodes.…”

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confidence: 99%

Study of the nematode putative GABA type‐A receptor subunits: evidence for modulation by ivermectin

Feng

Hayashi²,

Beech

et al. 2002

Journal of Neurochemistry

116

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Two alleles of the HG1 gene, which encodes a putative GABA receptor a/c subunit, were isolated from Haemonchus contortus. These two alleles were shown previously to be associated with ivermectin susceptibility (HG1A) and resistance (HG1E), respectively. Sequence analysis indicates that they differ in four amino acids. To explore the functional properties of the two alleles, a full-length cDNA encoding the b subunit, a key functional component of the GABA receptor, was isolated from Caenorhabditis elegans (gab-1, corresponding to the GenBank locus ZC482.1) and coexpressed in Xenopus oocytes with the HG1 alleles. When gab-1 was coexpressed with either the HG1A allele or the HG1E allele in Xenopus oocytes, c-aminobutyric acid (GABA)-responsive channels with different sensitivity to the agonist were formed. The effects of ivermectin on the hetero-oligomeric receptors were determined. Application of ivermectin alone had no effect on the receptors. However, when coapplied with 10 lM GABA, ivermectin potentiated the GABA-evoked current of the GAB-1/ HG1A receptor, but attenuated the GABA response of the GAB-1/HG1E receptor. We demonstrated that the coexpressed HG1 and GAB-1 receptors are GABA-responsive, and provide evidence for the possible involvement of GABA receptors in the mechanism of ivermectin resistance.

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An electrophysiological preparation ofAscaris suumpharyngeal muscle reveals a glutamate-gated chloride channel sensitive to the avermectin analogue, milbemycin D

Cited by 88 publications

References 13 publications

The genetics of ivermectin resistance in Caenorhabditis elegans

The genetics of ivermectin resistance in Caenorhabditis elegans

Ivermectin disrupts the function of the excretory-secretory apparatus in microfilariae of Brugia malayi

Study of the nematode putative GABA type‐A receptor subunits: evidence for modulation by ivermectin

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