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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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ACR-7 acted in the pharyngeal muscle.(A) ACR-7 was highly expressed in the pharynx as indicated by the arrows. A, anterior; P, posterior; D, dorsal; V, ventral. Scattered expression was also observed in the tail and vulval regions. (B) Clozapine inhibited pharyngeal pumping in wild-type animals in a concentration-dependent manner. Suppression of clozapine-induced inhibition of pharyngeal pumping was seen in acr-7(tm863) animals, and rescue was observed with expression of ACR-7 in the mutant background. A putative acr-7 promoter was utilized to drive expression for the acr-7(tm863) mchEx40 strain, whereas the pharyngeal muscle-specific myo-2 promoter was utilized for the acr-7(tm863) mchEx207 strain. (C) Both nicotine and clozapine inhibited the pumping rate in N2 animals. d-TC partially blocked these effects. Importantly, d-TC alone had no effect on pumping. (D) d-TC failed to block clozapine- or nicotine-induced inhibition of pumping in acr-7(lf) animals. * P<0.05; ** P<0.01; *** P<0.0001.
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pgen-1003313-g007: ACR-7 acted in the pharyngeal muscle.(A) ACR-7 was highly expressed in the pharynx as indicated by the arrows. A, anterior; P, posterior; D, dorsal; V, ventral. Scattered expression was also observed in the tail and vulval regions. (B) Clozapine inhibited pharyngeal pumping in wild-type animals in a concentration-dependent manner. Suppression of clozapine-induced inhibition of pharyngeal pumping was seen in acr-7(tm863) animals, and rescue was observed with expression of ACR-7 in the mutant background. A putative acr-7 promoter was utilized to drive expression for the acr-7(tm863) mchEx40 strain, whereas the pharyngeal muscle-specific myo-2 promoter was utilized for the acr-7(tm863) mchEx207 strain. (C) Both nicotine and clozapine inhibited the pumping rate in N2 animals. d-TC partially blocked these effects. Importantly, d-TC alone had no effect on pumping. (D) d-TC failed to block clozapine- or nicotine-induced inhibition of pumping in acr-7(lf) animals. * P<0.05; ** P<0.01; *** P<0.0001.

Mentions: We generated transgenic lines expressing a Pacr-7::GFP transcriptional fusion construct or a Pacr-7::acr-7::GFP translational fusion construct. In both cases, GFP was strongly expressed in the pharyngeal muscles of transgenic animals (Figure 7A). Using pharyngeal pumping and fluorescent bead assays, we previously showed that clozapine caused dose-dependent inhibition of pharyngeal pumping [12]. Inhibition of pharyngeal pumping causes larval arrest in C. elegans[37]. Thus, clozapine likely delayed development, in part, by inhibiting pharyngeal pumping.


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)

ACR-7 acted in the pharyngeal muscle.(A) ACR-7 was highly expressed in the pharynx as indicated by the arrows. A, anterior; P, posterior; D, dorsal; V, ventral. Scattered expression was also observed in the tail and vulval regions. (B) Clozapine inhibited pharyngeal pumping in wild-type animals in a concentration-dependent manner. Suppression of clozapine-induced inhibition of pharyngeal pumping was seen in acr-7(tm863) animals, and rescue was observed with expression of ACR-7 in the mutant background. A putative acr-7 promoter was utilized to drive expression for the acr-7(tm863) mchEx40 strain, whereas the pharyngeal muscle-specific myo-2 promoter was utilized for the acr-7(tm863) mchEx207 strain. (C) Both nicotine and clozapine inhibited the pumping rate in N2 animals. d-TC partially blocked these effects. Importantly, d-TC alone had no effect on pumping. (D) d-TC failed to block clozapine- or nicotine-induced inhibition of pumping in acr-7(lf) animals. * P<0.05; ** P<0.01; *** P<0.0001.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1003313-g007: ACR-7 acted in the pharyngeal muscle.(A) ACR-7 was highly expressed in the pharynx as indicated by the arrows. A, anterior; P, posterior; D, dorsal; V, ventral. Scattered expression was also observed in the tail and vulval regions. (B) Clozapine inhibited pharyngeal pumping in wild-type animals in a concentration-dependent manner. Suppression of clozapine-induced inhibition of pharyngeal pumping was seen in acr-7(tm863) animals, and rescue was observed with expression of ACR-7 in the mutant background. A putative acr-7 promoter was utilized to drive expression for the acr-7(tm863) mchEx40 strain, whereas the pharyngeal muscle-specific myo-2 promoter was utilized for the acr-7(tm863) mchEx207 strain. (C) Both nicotine and clozapine inhibited the pumping rate in N2 animals. d-TC partially blocked these effects. Importantly, d-TC alone had no effect on pumping. (D) d-TC failed to block clozapine- or nicotine-induced inhibition of pumping in acr-7(lf) animals. * P<0.05; ** P<0.01; *** P<0.0001.
Mentions: We generated transgenic lines expressing a Pacr-7::GFP transcriptional fusion construct or a Pacr-7::acr-7::GFP translational fusion construct. In both cases, GFP was strongly expressed in the pharyngeal muscles of transgenic animals (Figure 7A). Using pharyngeal pumping and fluorescent bead assays, we previously showed that clozapine caused dose-dependent inhibition of pharyngeal pumping [12]. Inhibition of pharyngeal pumping causes larval arrest in C. elegans[37]. Thus, clozapine likely delayed development, in part, by inhibiting pharyngeal pumping.

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