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A genome-wide RNAi screen in Caenorhabditis elegans identifies the nicotinic acetylcholine receptor subunit ACR-7 as an antipsychotic drug target.

Saur T, DeMarco SE, Ortiz A, Sliwoski GR, Hao L, Wang X, Cohen BM, Buttner EA - PLoS Genet. (2013)

Bottom Line: We validate the requirement for acr-7 by showing that acr-7 knockout suppresses clozapine-induced larval arrest and that expression of a full-length translational GFP fusion construct rescues this phenotype. nAChR agonists phenocopy the developmental effects of clozapine, while nAChR antagonists partially block these effects.ACR-7 is strongly expressed in the pharynx, and clozapine inhibits pharyngeal pumping. acr-7 knockout and nAChR antagonists suppress clozapine-induced inhibition of pharyngeal pumping.No APDs are known to activate nAChRs, but a number of studies indicate that α7-nAChR agonists may prove effective for the treatment of psychosis. α-like nAChR signaling is a mechanism through which clozapine may produce its therapeutic and/or toxic effects in humans, a hypothesis that could be tested following identification of the mammalian ortholog of C. elegans acr-7.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
We report a genome-wide RNA interference (RNAi) screen for Suppressors of Clozapine-induced Larval Arrest (scla genes) in Caenorhabditis elegans, the first genetic suppressor screen for antipsychotic drug (APD) targets in an animal. The screen identifies 40 suppressors, including the α-like nicotinic acetylcholine receptor (nAChR) homolog acr-7. We validate the requirement for acr-7 by showing that acr-7 knockout suppresses clozapine-induced larval arrest and that expression of a full-length translational GFP fusion construct rescues this phenotype. nAChR agonists phenocopy the developmental effects of clozapine, while nAChR antagonists partially block these effects. ACR-7 is strongly expressed in the pharynx, and clozapine inhibits pharyngeal pumping. acr-7 knockout and nAChR antagonists suppress clozapine-induced inhibition of pharyngeal pumping. These findings suggest that clozapine activates ACR-7 channels in pharyngeal muscle, leading to tetanus of pharyngeal muscle with consequent larval arrest. No APDs are known to activate nAChRs, but a number of studies indicate that α7-nAChR agonists may prove effective for the treatment of psychosis. α-like nAChR signaling is a mechanism through which clozapine may produce its therapeutic and/or toxic effects in humans, a hypothesis that could be tested following identification of the mammalian ortholog of C. elegans acr-7.

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Ach release was not the mechanism of clozapine-induced larval arrest.Mutations in genes required for Ach release failed to suppress clozapine-induced developmental delay. Strong loss-of-function of the choline acetyltransferase gene cha-1 or the synaptic vesicle Ach transporter gene unc-17 alone produced developmental delay. Therefore, both weak (n2411 or e113) and strong (p1152 or e245) loss-of-function alleles were tested.
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pgen-1003313-g006: Ach release was not the mechanism of clozapine-induced larval arrest.Mutations in genes required for Ach release failed to suppress clozapine-induced developmental delay. Strong loss-of-function of the choline acetyltransferase gene cha-1 or the synaptic vesicle Ach transporter gene unc-17 alone produced developmental delay. Therefore, both weak (n2411 or e113) and strong (p1152 or e245) loss-of-function alleles were tested.

Mentions: Our results did not exclude the possibility that clozapine might activate ACR-7 by triggering release of acetylcholine (Ach). If clozapine does so, then mutations in genes required for Ach release should have suppressed clozapine-induced developmental delay. We tested two alleles of the choline acetyltransferase gene cha-1 and two alleles of the synaptic vesicle Ach transporter gene unc-17 for suppression of clozapine-induced developmental delay [35], [36]. Although both genes are required for Ach release, we found that mutations in cha-1 or unc-17 were not suppressors, suggesting that clozapine did not cause developmental delay by stimulating Ach release (Figure 6).


A genome-wide RNAi screen in Caenorhabditis elegans identifies the nicotinic acetylcholine receptor subunit ACR-7 as an antipsychotic drug target.

Saur T, DeMarco SE, Ortiz A, Sliwoski GR, Hao L, Wang X, Cohen BM, Buttner EA - PLoS Genet. (2013)

Ach release was not the mechanism of clozapine-induced larval arrest.Mutations in genes required for Ach release failed to suppress clozapine-induced developmental delay. Strong loss-of-function of the choline acetyltransferase gene cha-1 or the synaptic vesicle Ach transporter gene unc-17 alone produced developmental delay. Therefore, both weak (n2411 or e113) and strong (p1152 or e245) loss-of-function alleles were tested.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3585123&req=5

pgen-1003313-g006: Ach release was not the mechanism of clozapine-induced larval arrest.Mutations in genes required for Ach release failed to suppress clozapine-induced developmental delay. Strong loss-of-function of the choline acetyltransferase gene cha-1 or the synaptic vesicle Ach transporter gene unc-17 alone produced developmental delay. Therefore, both weak (n2411 or e113) and strong (p1152 or e245) loss-of-function alleles were tested.
Mentions: Our results did not exclude the possibility that clozapine might activate ACR-7 by triggering release of acetylcholine (Ach). If clozapine does so, then mutations in genes required for Ach release should have suppressed clozapine-induced developmental delay. We tested two alleles of the choline acetyltransferase gene cha-1 and two alleles of the synaptic vesicle Ach transporter gene unc-17 for suppression of clozapine-induced developmental delay [35], [36]. Although both genes are required for Ach release, we found that mutations in cha-1 or unc-17 were not suppressors, suggesting that clozapine did not cause developmental delay by stimulating Ach release (Figure 6).

Bottom Line: We validate the requirement for acr-7 by showing that acr-7 knockout suppresses clozapine-induced larval arrest and that expression of a full-length translational GFP fusion construct rescues this phenotype. nAChR agonists phenocopy the developmental effects of clozapine, while nAChR antagonists partially block these effects.ACR-7 is strongly expressed in the pharynx, and clozapine inhibits pharyngeal pumping. acr-7 knockout and nAChR antagonists suppress clozapine-induced inhibition of pharyngeal pumping.No APDs are known to activate nAChRs, but a number of studies indicate that α7-nAChR agonists may prove effective for the treatment of psychosis. α-like nAChR signaling is a mechanism through which clozapine may produce its therapeutic and/or toxic effects in humans, a hypothesis that could be tested following identification of the mammalian ortholog of C. elegans acr-7.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
We report a genome-wide RNA interference (RNAi) screen for Suppressors of Clozapine-induced Larval Arrest (scla genes) in Caenorhabditis elegans, the first genetic suppressor screen for antipsychotic drug (APD) targets in an animal. The screen identifies 40 suppressors, including the α-like nicotinic acetylcholine receptor (nAChR) homolog acr-7. We validate the requirement for acr-7 by showing that acr-7 knockout suppresses clozapine-induced larval arrest and that expression of a full-length translational GFP fusion construct rescues this phenotype. nAChR agonists phenocopy the developmental effects of clozapine, while nAChR antagonists partially block these effects. ACR-7 is strongly expressed in the pharynx, and clozapine inhibits pharyngeal pumping. acr-7 knockout and nAChR antagonists suppress clozapine-induced inhibition of pharyngeal pumping. These findings suggest that clozapine activates ACR-7 channels in pharyngeal muscle, leading to tetanus of pharyngeal muscle with consequent larval arrest. No APDs are known to activate nAChRs, but a number of studies indicate that α7-nAChR agonists may prove effective for the treatment of psychosis. α-like nAChR signaling is a mechanism through which clozapine may produce its therapeutic and/or toxic effects in humans, a hypothesis that could be tested following identification of the mammalian ortholog of C. elegans acr-7.

Show MeSH
Related in: MedlinePlus