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Cell-Autonomous Gβ Signaling Defines Neuron-Specific Steady State Serotonin Synthesis in Caenorhabditis elegans.

Xu L, Choi S, Xie Y, Sze JY - PLoS Genet. (2015)

Bottom Line: We found that signaling through cell autonomous GPB-1 to the OCR-2 TRPV channel defines the baseline expression of 5-HT synthesis enzyme tryptophan hydroxylase tph-1 in ADF chemosensory neurons.These results revealed a Gβ-mediated signaling operating in differentiated cells to specify intrinsic functional properties, and indicate that baseline TPH expression is not a default generic serotonergic fate, but is programmed in a cell-specific manner in the mature nervous system.Cell-specific regulation of TPH expression could be a general principle for tailored steady state 5-HT synthesis in functionally distinct neurons and their regulation of innate behavior.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America.

ABSTRACT
Heterotrimeric G proteins regulate a vast array of cellular functions via specific intracellular effectors. Accumulating pharmacological and biochemical studies implicate Gβ subunits as signaling molecules interacting directly with a wide range of effectors to modulate downstream cellular responses, in addition to their role in regulating Gα subunit activities. However, the native biological roles of Gβ-mediated signaling pathways in vivo have been characterized only in a few cases. Here, we identified a Gβ GPB-1 signaling pathway operating in specific serotonergic neurons to the define steady state serotonin (5-HT) synthesis, through a genetic screen for 5-HT synthesis mutants in Caenorhabditis elegans. We found that signaling through cell autonomous GPB-1 to the OCR-2 TRPV channel defines the baseline expression of 5-HT synthesis enzyme tryptophan hydroxylase tph-1 in ADF chemosensory neurons. This Gβ signaling pathway is not essential for establishing the serotonergic cell fates and is mechanistically separated from stress-induced tph-1 upregulation. We identified that ADF-produced 5-HT controls specific innate rhythmic behaviors. These results revealed a Gβ-mediated signaling operating in differentiated cells to specify intrinsic functional properties, and indicate that baseline TPH expression is not a default generic serotonergic fate, but is programmed in a cell-specific manner in the mature nervous system. Cell-specific regulation of TPH expression could be a general principle for tailored steady state 5-HT synthesis in functionally distinct neurons and their regulation of innate behavior.

No MeSH data available.


Related in: MedlinePlus

gpb-1 deficient mutants specifically diminish 5-HT synthesis in ADF neurons.(A)gpb-1 mutant alleles. Lines denote introns and rectangles denote exons of gpb-1 gene. The predicted region binding to Gγ (red) and seven WD40 repeats of the propeller domain (blue) that interacts with Gα are in reference of previous work [28,53]. A green line indicates the deleted region in the ok1875 allele, and an arrow points to the location of the yz71 mutation. (B) Photomicrographs showing tph-1::gfp and 5-HT immunostaining were selectively diminished in ADF neurons in yz71 mutants and rescued by gpb-1(g) transgene. (C—D) Quantification of tph-1::gfp fluorescence (C) and 5-HT immunoreactivity (D) in ADF and NSM neurons in L4 stage animals. (E) Quantification of ADF tph-1::gfp in WT, gpb-1(ok1875)- and yz71 at L1 stage. (F) Comparing ADF tph-1::gfp in WT with that in ok1875/yz71 hemizygotes, and ok1875/+ and yz71/+ heterozygotes. Data represent the average of 2 (5-HT staining) or 3 (GFP) repeats. N = 18–32/genotype/trial. The value of fluorescence of mutants and transgenic animals is normalized to that of WT animals, mean ± SEM, *p < 0.05, **p < 0.01, ***, p < 0.001, t-tests.
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pgen.1005540.g001: gpb-1 deficient mutants specifically diminish 5-HT synthesis in ADF neurons.(A)gpb-1 mutant alleles. Lines denote introns and rectangles denote exons of gpb-1 gene. The predicted region binding to Gγ (red) and seven WD40 repeats of the propeller domain (blue) that interacts with Gα are in reference of previous work [28,53]. A green line indicates the deleted region in the ok1875 allele, and an arrow points to the location of the yz71 mutation. (B) Photomicrographs showing tph-1::gfp and 5-HT immunostaining were selectively diminished in ADF neurons in yz71 mutants and rescued by gpb-1(g) transgene. (C—D) Quantification of tph-1::gfp fluorescence (C) and 5-HT immunoreactivity (D) in ADF and NSM neurons in L4 stage animals. (E) Quantification of ADF tph-1::gfp in WT, gpb-1(ok1875)- and yz71 at L1 stage. (F) Comparing ADF tph-1::gfp in WT with that in ok1875/yz71 hemizygotes, and ok1875/+ and yz71/+ heterozygotes. Data represent the average of 2 (5-HT staining) or 3 (GFP) repeats. N = 18–32/genotype/trial. The value of fluorescence of mutants and transgenic animals is normalized to that of WT animals, mean ± SEM, *p < 0.05, **p < 0.01, ***, p < 0.001, t-tests.

Mentions: We isolated the yz71 mutant through an unbiased forward genetic screen for mutations that specifically diminished tph-1::gfp expression in ADF serotonergic chemosensory neurons [12]. Under optimal growth conditions, yz71 mutants showed an ~90% reduction in ADF tph-1::gfp throughout the life, as compared to wild-type (WT) animals (Fig 1B and 1C). In contrast, tph-1::gfp in other neurons was not reduced in yz71 mutants (Fig 1B and 1C). 5-HT immunostaining of yz71 mutants showed dramatically diminished 5-HT levels in ADF (Fig 1B and 1D). We therefore concluded that yz71 impairs a gene function specifically required for tph-1 expression, thus 5-HT synthesis, in the ADF neurons.


Cell-Autonomous Gβ Signaling Defines Neuron-Specific Steady State Serotonin Synthesis in Caenorhabditis elegans.

Xu L, Choi S, Xie Y, Sze JY - PLoS Genet. (2015)

gpb-1 deficient mutants specifically diminish 5-HT synthesis in ADF neurons.(A)gpb-1 mutant alleles. Lines denote introns and rectangles denote exons of gpb-1 gene. The predicted region binding to Gγ (red) and seven WD40 repeats of the propeller domain (blue) that interacts with Gα are in reference of previous work [28,53]. A green line indicates the deleted region in the ok1875 allele, and an arrow points to the location of the yz71 mutation. (B) Photomicrographs showing tph-1::gfp and 5-HT immunostaining were selectively diminished in ADF neurons in yz71 mutants and rescued by gpb-1(g) transgene. (C—D) Quantification of tph-1::gfp fluorescence (C) and 5-HT immunoreactivity (D) in ADF and NSM neurons in L4 stage animals. (E) Quantification of ADF tph-1::gfp in WT, gpb-1(ok1875)- and yz71 at L1 stage. (F) Comparing ADF tph-1::gfp in WT with that in ok1875/yz71 hemizygotes, and ok1875/+ and yz71/+ heterozygotes. Data represent the average of 2 (5-HT staining) or 3 (GFP) repeats. N = 18–32/genotype/trial. The value of fluorescence of mutants and transgenic animals is normalized to that of WT animals, mean ± SEM, *p < 0.05, **p < 0.01, ***, p < 0.001, t-tests.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4581872&req=5

pgen.1005540.g001: gpb-1 deficient mutants specifically diminish 5-HT synthesis in ADF neurons.(A)gpb-1 mutant alleles. Lines denote introns and rectangles denote exons of gpb-1 gene. The predicted region binding to Gγ (red) and seven WD40 repeats of the propeller domain (blue) that interacts with Gα are in reference of previous work [28,53]. A green line indicates the deleted region in the ok1875 allele, and an arrow points to the location of the yz71 mutation. (B) Photomicrographs showing tph-1::gfp and 5-HT immunostaining were selectively diminished in ADF neurons in yz71 mutants and rescued by gpb-1(g) transgene. (C—D) Quantification of tph-1::gfp fluorescence (C) and 5-HT immunoreactivity (D) in ADF and NSM neurons in L4 stage animals. (E) Quantification of ADF tph-1::gfp in WT, gpb-1(ok1875)- and yz71 at L1 stage. (F) Comparing ADF tph-1::gfp in WT with that in ok1875/yz71 hemizygotes, and ok1875/+ and yz71/+ heterozygotes. Data represent the average of 2 (5-HT staining) or 3 (GFP) repeats. N = 18–32/genotype/trial. The value of fluorescence of mutants and transgenic animals is normalized to that of WT animals, mean ± SEM, *p < 0.05, **p < 0.01, ***, p < 0.001, t-tests.
Mentions: We isolated the yz71 mutant through an unbiased forward genetic screen for mutations that specifically diminished tph-1::gfp expression in ADF serotonergic chemosensory neurons [12]. Under optimal growth conditions, yz71 mutants showed an ~90% reduction in ADF tph-1::gfp throughout the life, as compared to wild-type (WT) animals (Fig 1B and 1C). In contrast, tph-1::gfp in other neurons was not reduced in yz71 mutants (Fig 1B and 1C). 5-HT immunostaining of yz71 mutants showed dramatically diminished 5-HT levels in ADF (Fig 1B and 1D). We therefore concluded that yz71 impairs a gene function specifically required for tph-1 expression, thus 5-HT synthesis, in the ADF neurons.

Bottom Line: We found that signaling through cell autonomous GPB-1 to the OCR-2 TRPV channel defines the baseline expression of 5-HT synthesis enzyme tryptophan hydroxylase tph-1 in ADF chemosensory neurons.These results revealed a Gβ-mediated signaling operating in differentiated cells to specify intrinsic functional properties, and indicate that baseline TPH expression is not a default generic serotonergic fate, but is programmed in a cell-specific manner in the mature nervous system.Cell-specific regulation of TPH expression could be a general principle for tailored steady state 5-HT synthesis in functionally distinct neurons and their regulation of innate behavior.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America.

ABSTRACT
Heterotrimeric G proteins regulate a vast array of cellular functions via specific intracellular effectors. Accumulating pharmacological and biochemical studies implicate Gβ subunits as signaling molecules interacting directly with a wide range of effectors to modulate downstream cellular responses, in addition to their role in regulating Gα subunit activities. However, the native biological roles of Gβ-mediated signaling pathways in vivo have been characterized only in a few cases. Here, we identified a Gβ GPB-1 signaling pathway operating in specific serotonergic neurons to the define steady state serotonin (5-HT) synthesis, through a genetic screen for 5-HT synthesis mutants in Caenorhabditis elegans. We found that signaling through cell autonomous GPB-1 to the OCR-2 TRPV channel defines the baseline expression of 5-HT synthesis enzyme tryptophan hydroxylase tph-1 in ADF chemosensory neurons. This Gβ signaling pathway is not essential for establishing the serotonergic cell fates and is mechanistically separated from stress-induced tph-1 upregulation. We identified that ADF-produced 5-HT controls specific innate rhythmic behaviors. These results revealed a Gβ-mediated signaling operating in differentiated cells to specify intrinsic functional properties, and indicate that baseline TPH expression is not a default generic serotonergic fate, but is programmed in a cell-specific manner in the mature nervous system. Cell-specific regulation of TPH expression could be a general principle for tailored steady state 5-HT synthesis in functionally distinct neurons and their regulation of innate behavior.

No MeSH data available.


Related in: MedlinePlus