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Feeding state, insulin and NPR-1 modulate chemoreceptor gene expression via integration of sensory and circuit inputs.

Gruner M, Nelson D, Winbush A, Hintz R, Ryu L, Chung SH, Kim K, Gabel CV, van der Linden AM - PLoS Genet. (2014)

Bottom Line: Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression.While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway.Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Feeding state and food availability can dramatically alter an animals' sensory response to chemicals in its environment. Dynamic changes in the expression of chemoreceptor genes may underlie some of these food and state-dependent changes in chemosensory behavior, but the mechanisms underlying these expression changes are unknown. Here, we identified a KIN-29 (SIK)-dependent chemoreceptor, srh-234, in C. elegans whose expression in the ADL sensory neuron type is regulated by integration of sensory and internal feeding state signals. We show that in addition to KIN-29, signaling is mediated by the DAF-2 insulin-like receptor, OCR-2 TRPV channel, and NPR-1 neuropeptide receptor. Cell-specific rescue experiments suggest that DAF-2 and OCR-2 act in ADL, while NPR-1 acts in the RMG interneurons. NPR-1-mediated regulation of srh-234 is dependent on gap-junctions, implying that circuit inputs regulate the expression of chemoreceptor genes in sensory neurons. Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression. While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway. Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

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daf-2 and daf-16a are required in ADL, but not in the intestine, to regulate srh-234 expression.A) Percentage of mutant animals with defects in insulin signaling expressing srh-234p::gfp at wild-type levels. daf-2(e1307) is a temperature sensitive allele. In all experiments, animals were raised at 15°C (permissive temperature) and shifted to the 25°C (restrictive temperature) as L4 larvae. Animals (n>150) were examined at 150× magnification for each genotype. B, C) Relative expression of srh-234p::gfp in daf-2 or daf-16 mutants carrying compared to wild-type when fed or starved. For strains carrying ADL::daf-2 cDNA, pan-neural::daf-2 cDNA, intestine::daf-2 cDNA, ADL::daf-16a cDNA and intestine::daf-16a cDNA extrachromosomal arrays (see Material and Methods), data shown is for at least two independent transgenic lines. Animals (n = 18–25) were examined at 400× magnification for each genotype. * indicates values that are different from that of wild-type animals at P<0.001, # and ## indicates the values that are different between the genotypes compared by brackets at P<0.001, and P<0.05, respectively, using either a two-sample t-test or a χ2 test of independence. Error bars denote the SEM or SEP.
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pgen-1004707-g003: daf-2 and daf-16a are required in ADL, but not in the intestine, to regulate srh-234 expression.A) Percentage of mutant animals with defects in insulin signaling expressing srh-234p::gfp at wild-type levels. daf-2(e1307) is a temperature sensitive allele. In all experiments, animals were raised at 15°C (permissive temperature) and shifted to the 25°C (restrictive temperature) as L4 larvae. Animals (n>150) were examined at 150× magnification for each genotype. B, C) Relative expression of srh-234p::gfp in daf-2 or daf-16 mutants carrying compared to wild-type when fed or starved. For strains carrying ADL::daf-2 cDNA, pan-neural::daf-2 cDNA, intestine::daf-2 cDNA, ADL::daf-16a cDNA and intestine::daf-16a cDNA extrachromosomal arrays (see Material and Methods), data shown is for at least two independent transgenic lines. Animals (n = 18–25) were examined at 400× magnification for each genotype. * indicates values that are different from that of wild-type animals at P<0.001, # and ## indicates the values that are different between the genotypes compared by brackets at P<0.001, and P<0.05, respectively, using either a two-sample t-test or a χ2 test of independence. Error bars denote the SEM or SEP.

Mentions: As internal state signals in C. elegans are conveyed through an insulin signaling pathway with DAF-2 being the main insulin-like receptor [25], we explored whether insulin signaling plays a role in the regulation of srh-234. Consistent with low daf-2 insulin signaling being associated with a starved state, we found that daf-2(e1307) mutants reduce srh-234 expression in ADL in fed conditions, similar to starved wild-type animals (Figure 3A). Since daf-2 activates insulin signaling by repressing the daf-16 FOXO transcription factor, and loss of daf-16 function results in active insulin signaling [26], we next examined whether daf-16(mu86) suppressed the daf-2- and starvation-induced downregulation of srh-234 expression. Indeed, we found that both daf-16(mu86) mutants and daf-2(e1307); daf-16(mu86) double mutants showed a significant increase in srh-234 expression during starvation compared to starved wild-type animals (Figure 3A), suggesting that starved animals reduce srh-234 expression by lowering DAF-2 signaling and activating DAF-16.


Feeding state, insulin and NPR-1 modulate chemoreceptor gene expression via integration of sensory and circuit inputs.

Gruner M, Nelson D, Winbush A, Hintz R, Ryu L, Chung SH, Kim K, Gabel CV, van der Linden AM - PLoS Genet. (2014)

daf-2 and daf-16a are required in ADL, but not in the intestine, to regulate srh-234 expression.A) Percentage of mutant animals with defects in insulin signaling expressing srh-234p::gfp at wild-type levels. daf-2(e1307) is a temperature sensitive allele. In all experiments, animals were raised at 15°C (permissive temperature) and shifted to the 25°C (restrictive temperature) as L4 larvae. Animals (n>150) were examined at 150× magnification for each genotype. B, C) Relative expression of srh-234p::gfp in daf-2 or daf-16 mutants carrying compared to wild-type when fed or starved. For strains carrying ADL::daf-2 cDNA, pan-neural::daf-2 cDNA, intestine::daf-2 cDNA, ADL::daf-16a cDNA and intestine::daf-16a cDNA extrachromosomal arrays (see Material and Methods), data shown is for at least two independent transgenic lines. Animals (n = 18–25) were examined at 400× magnification for each genotype. * indicates values that are different from that of wild-type animals at P<0.001, # and ## indicates the values that are different between the genotypes compared by brackets at P<0.001, and P<0.05, respectively, using either a two-sample t-test or a χ2 test of independence. Error bars denote the SEM or SEP.
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pgen-1004707-g003: daf-2 and daf-16a are required in ADL, but not in the intestine, to regulate srh-234 expression.A) Percentage of mutant animals with defects in insulin signaling expressing srh-234p::gfp at wild-type levels. daf-2(e1307) is a temperature sensitive allele. In all experiments, animals were raised at 15°C (permissive temperature) and shifted to the 25°C (restrictive temperature) as L4 larvae. Animals (n>150) were examined at 150× magnification for each genotype. B, C) Relative expression of srh-234p::gfp in daf-2 or daf-16 mutants carrying compared to wild-type when fed or starved. For strains carrying ADL::daf-2 cDNA, pan-neural::daf-2 cDNA, intestine::daf-2 cDNA, ADL::daf-16a cDNA and intestine::daf-16a cDNA extrachromosomal arrays (see Material and Methods), data shown is for at least two independent transgenic lines. Animals (n = 18–25) were examined at 400× magnification for each genotype. * indicates values that are different from that of wild-type animals at P<0.001, # and ## indicates the values that are different between the genotypes compared by brackets at P<0.001, and P<0.05, respectively, using either a two-sample t-test or a χ2 test of independence. Error bars denote the SEM or SEP.
Mentions: As internal state signals in C. elegans are conveyed through an insulin signaling pathway with DAF-2 being the main insulin-like receptor [25], we explored whether insulin signaling plays a role in the regulation of srh-234. Consistent with low daf-2 insulin signaling being associated with a starved state, we found that daf-2(e1307) mutants reduce srh-234 expression in ADL in fed conditions, similar to starved wild-type animals (Figure 3A). Since daf-2 activates insulin signaling by repressing the daf-16 FOXO transcription factor, and loss of daf-16 function results in active insulin signaling [26], we next examined whether daf-16(mu86) suppressed the daf-2- and starvation-induced downregulation of srh-234 expression. Indeed, we found that both daf-16(mu86) mutants and daf-2(e1307); daf-16(mu86) double mutants showed a significant increase in srh-234 expression during starvation compared to starved wild-type animals (Figure 3A), suggesting that starved animals reduce srh-234 expression by lowering DAF-2 signaling and activating DAF-16.

Bottom Line: Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression.While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway.Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Feeding state and food availability can dramatically alter an animals' sensory response to chemicals in its environment. Dynamic changes in the expression of chemoreceptor genes may underlie some of these food and state-dependent changes in chemosensory behavior, but the mechanisms underlying these expression changes are unknown. Here, we identified a KIN-29 (SIK)-dependent chemoreceptor, srh-234, in C. elegans whose expression in the ADL sensory neuron type is regulated by integration of sensory and internal feeding state signals. We show that in addition to KIN-29, signaling is mediated by the DAF-2 insulin-like receptor, OCR-2 TRPV channel, and NPR-1 neuropeptide receptor. Cell-specific rescue experiments suggest that DAF-2 and OCR-2 act in ADL, while NPR-1 acts in the RMG interneurons. NPR-1-mediated regulation of srh-234 is dependent on gap-junctions, implying that circuit inputs regulate the expression of chemoreceptor genes in sensory neurons. Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression. While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway. Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

Show MeSH