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Regulation of food intake by mechanosensory ion channels in enteric neurons.

Olds WH, Xu T - Elife (2014)

Bottom Line: Modulating activities of a specific subset of enteric neurons, the posterior enteric neurons (PENs), results in sixfold changes in food intake.Deficiency of the mechanosensory ion channel PPK1 gene or RNAi knockdown of its expression in the PENS result in a similar increase in food intake, which can be rescued by expression of wild-type PPK1 in the same neurons.Finally, pharmacological inhibition of the mechanosensory ion channel phenocopies the result of genetic interrogation.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Howard Hughes Medical Institute, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, United States.

ABSTRACT
Regulation of food intake is fundamental to energy homeostasis in animals. The contribution of non-nutritive and metabolic signals in regulating feeding is unclear. Here we show that enteric neurons play a major role in regulating feeding through specialized mechanosensory ion channels in Drosophila. Modulating activities of a specific subset of enteric neurons, the posterior enteric neurons (PENs), results in sixfold changes in food intake. Deficiency of the mechanosensory ion channel PPK1 gene or RNAi knockdown of its expression in the PENS result in a similar increase in food intake, which can be rescued by expression of wild-type PPK1 in the same neurons. Finally, pharmacological inhibition of the mechanosensory ion channel phenocopies the result of genetic interrogation. Together, our study provides the first molecular genetic evidence that mechanosensory ion channels in the enteric neurons are involved in regulating feeding, offering an enticing alternative to current therapeutic strategy for weight control.

No MeSH data available.


PPK1 functions in Drosophila PENs to regulate feeding.(A–B) Results of capillary feeding assays by either inactivating (A, Ilp7-Gal4 or HGN1-Gal4; UAS-shiTS1) or activating (B, Ilp7-Gal4 or HGN1-Gal4; UAS-TRPA1) the PENs (n = 4–8 replicates). (C) Outside and inside views of the hindgut (red, phalloidin, muscle) with posterior enteric neuron projections (green, 22C10). (D) PPK1 expresses in the PENs projecting to the hindgut pylorus (left) and rectum (right) (PPK1-Gal4;UAS-mCD8::GFP). (E) The effect of PPK1 knock-down on food intake (Ilp7-Gal4 or HGN1-Gal4, UAS-PPK1-RNAi#1 or UAS-PPK1-RNAi#2) (n = 3–8 replicates). (F) Food intake results for PPK1 deficiency (dfb88h49/dfA400) and rescued animals (dfb88h49/dfA400; Ilp7-Gal4, UAS-PPK1) (n = 4–7 replicates). (G) Food intake results when PPK1 is inhibited using benzamil in wild-type or Ilp7 > PPK1 RNAi #1 flies (n = 8–10 replicates). * = p < 0.05, compared to corresponding UAS and Gal4 control or indicated controls. Significances indicated are based on ANOVA and Tukey post-hoc test. Data represent the average ± s.e.m. of the results obtained.DOI:http://dx.doi.org/10.7554/eLife.04402.004
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fig2: PPK1 functions in Drosophila PENs to regulate feeding.(A–B) Results of capillary feeding assays by either inactivating (A, Ilp7-Gal4 or HGN1-Gal4; UAS-shiTS1) or activating (B, Ilp7-Gal4 or HGN1-Gal4; UAS-TRPA1) the PENs (n = 4–8 replicates). (C) Outside and inside views of the hindgut (red, phalloidin, muscle) with posterior enteric neuron projections (green, 22C10). (D) PPK1 expresses in the PENs projecting to the hindgut pylorus (left) and rectum (right) (PPK1-Gal4;UAS-mCD8::GFP). (E) The effect of PPK1 knock-down on food intake (Ilp7-Gal4 or HGN1-Gal4, UAS-PPK1-RNAi#1 or UAS-PPK1-RNAi#2) (n = 3–8 replicates). (F) Food intake results for PPK1 deficiency (dfb88h49/dfA400) and rescued animals (dfb88h49/dfA400; Ilp7-Gal4, UAS-PPK1) (n = 4–7 replicates). (G) Food intake results when PPK1 is inhibited using benzamil in wild-type or Ilp7 > PPK1 RNAi #1 flies (n = 8–10 replicates). * = p < 0.05, compared to corresponding UAS and Gal4 control or indicated controls. Significances indicated are based on ANOVA and Tukey post-hoc test. Data represent the average ± s.e.m. of the results obtained.DOI:http://dx.doi.org/10.7554/eLife.04402.004

Mentions: The change of glucose levels could result from differences in food intake. Previous work by Miguel-Aliaga and colleagues revealed that silencing Ilp7-Gal4 neurons increases defecation (Cognigni et al., 2011), which could be the result of increased feeding. We therefore examined the hypothesis that the activities of the PENs regulate food intake. Consistent with the hypothesis, we silenced the PENs in the absence of food and found that this abolished the gains in glucose levels (Figure 1E). We next investigated this directly using the capillary feeding assay (Ja et al., 2007). Silencing the PENs dramatically increased food intake (Figure 2A), which is consistent with the gains in glucose levels seen earlier. Conversely, activating these neurons caused dramatic decreases in feeding (Figure 2B). Together, manipulation of the activities of the PENs results in an overall six-fold change in feeding in comparison to the controls. This change is significantly larger than alterations by modulation of neuropeptide F signaling (Hong et al., 2012). These data indicate that the activities of the PENs play a prominent role in feeding.10.7554/eLife.04402.004Figure 2.PPK1 functions in Drosophila PENs to regulate feeding.


Regulation of food intake by mechanosensory ion channels in enteric neurons.

Olds WH, Xu T - Elife (2014)

PPK1 functions in Drosophila PENs to regulate feeding.(A–B) Results of capillary feeding assays by either inactivating (A, Ilp7-Gal4 or HGN1-Gal4; UAS-shiTS1) or activating (B, Ilp7-Gal4 or HGN1-Gal4; UAS-TRPA1) the PENs (n = 4–8 replicates). (C) Outside and inside views of the hindgut (red, phalloidin, muscle) with posterior enteric neuron projections (green, 22C10). (D) PPK1 expresses in the PENs projecting to the hindgut pylorus (left) and rectum (right) (PPK1-Gal4;UAS-mCD8::GFP). (E) The effect of PPK1 knock-down on food intake (Ilp7-Gal4 or HGN1-Gal4, UAS-PPK1-RNAi#1 or UAS-PPK1-RNAi#2) (n = 3–8 replicates). (F) Food intake results for PPK1 deficiency (dfb88h49/dfA400) and rescued animals (dfb88h49/dfA400; Ilp7-Gal4, UAS-PPK1) (n = 4–7 replicates). (G) Food intake results when PPK1 is inhibited using benzamil in wild-type or Ilp7 > PPK1 RNAi #1 flies (n = 8–10 replicates). * = p < 0.05, compared to corresponding UAS and Gal4 control or indicated controls. Significances indicated are based on ANOVA and Tukey post-hoc test. Data represent the average ± s.e.m. of the results obtained.DOI:http://dx.doi.org/10.7554/eLife.04402.004
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225495&req=5

fig2: PPK1 functions in Drosophila PENs to regulate feeding.(A–B) Results of capillary feeding assays by either inactivating (A, Ilp7-Gal4 or HGN1-Gal4; UAS-shiTS1) or activating (B, Ilp7-Gal4 or HGN1-Gal4; UAS-TRPA1) the PENs (n = 4–8 replicates). (C) Outside and inside views of the hindgut (red, phalloidin, muscle) with posterior enteric neuron projections (green, 22C10). (D) PPK1 expresses in the PENs projecting to the hindgut pylorus (left) and rectum (right) (PPK1-Gal4;UAS-mCD8::GFP). (E) The effect of PPK1 knock-down on food intake (Ilp7-Gal4 or HGN1-Gal4, UAS-PPK1-RNAi#1 or UAS-PPK1-RNAi#2) (n = 3–8 replicates). (F) Food intake results for PPK1 deficiency (dfb88h49/dfA400) and rescued animals (dfb88h49/dfA400; Ilp7-Gal4, UAS-PPK1) (n = 4–7 replicates). (G) Food intake results when PPK1 is inhibited using benzamil in wild-type or Ilp7 > PPK1 RNAi #1 flies (n = 8–10 replicates). * = p < 0.05, compared to corresponding UAS and Gal4 control or indicated controls. Significances indicated are based on ANOVA and Tukey post-hoc test. Data represent the average ± s.e.m. of the results obtained.DOI:http://dx.doi.org/10.7554/eLife.04402.004
Mentions: The change of glucose levels could result from differences in food intake. Previous work by Miguel-Aliaga and colleagues revealed that silencing Ilp7-Gal4 neurons increases defecation (Cognigni et al., 2011), which could be the result of increased feeding. We therefore examined the hypothesis that the activities of the PENs regulate food intake. Consistent with the hypothesis, we silenced the PENs in the absence of food and found that this abolished the gains in glucose levels (Figure 1E). We next investigated this directly using the capillary feeding assay (Ja et al., 2007). Silencing the PENs dramatically increased food intake (Figure 2A), which is consistent with the gains in glucose levels seen earlier. Conversely, activating these neurons caused dramatic decreases in feeding (Figure 2B). Together, manipulation of the activities of the PENs results in an overall six-fold change in feeding in comparison to the controls. This change is significantly larger than alterations by modulation of neuropeptide F signaling (Hong et al., 2012). These data indicate that the activities of the PENs play a prominent role in feeding.10.7554/eLife.04402.004Figure 2.PPK1 functions in Drosophila PENs to regulate feeding.

Bottom Line: Modulating activities of a specific subset of enteric neurons, the posterior enteric neurons (PENs), results in sixfold changes in food intake.Deficiency of the mechanosensory ion channel PPK1 gene or RNAi knockdown of its expression in the PENS result in a similar increase in food intake, which can be rescued by expression of wild-type PPK1 in the same neurons.Finally, pharmacological inhibition of the mechanosensory ion channel phenocopies the result of genetic interrogation.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Howard Hughes Medical Institute, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, United States.

ABSTRACT
Regulation of food intake is fundamental to energy homeostasis in animals. The contribution of non-nutritive and metabolic signals in regulating feeding is unclear. Here we show that enteric neurons play a major role in regulating feeding through specialized mechanosensory ion channels in Drosophila. Modulating activities of a specific subset of enteric neurons, the posterior enteric neurons (PENs), results in sixfold changes in food intake. Deficiency of the mechanosensory ion channel PPK1 gene or RNAi knockdown of its expression in the PENS result in a similar increase in food intake, which can be rescued by expression of wild-type PPK1 in the same neurons. Finally, pharmacological inhibition of the mechanosensory ion channel phenocopies the result of genetic interrogation. Together, our study provides the first molecular genetic evidence that mechanosensory ion channels in the enteric neurons are involved in regulating feeding, offering an enticing alternative to current therapeutic strategy for weight control.

No MeSH data available.