Functional Coupling of the γ‐Aminobutyric Acid<sub>B</sub> Receptor with Calcium Ion Channel and GTP‐Binding Protein and Its Alteration Following Solubilization of the γ‐Aminobutyric Acid<sub>B</sub> Receptor

Ohmori, Yasuhiro; Hirouchi, Masaaki; Taguchi, Junichi; Kuriyama, Kinya

doi:10.1111/j.1471-4159.1990.tb13285.x

Cited by 42 publications

(7 citation statements)

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“…A GPCR system in diatoms involving GABA or other extracellular or intracellular ligands may function similarly in protecting the cells against abiotic and biotic stressors such as temperature or salinity changes. The coupling of GABA B receptors with Ca 2+ ion channels or Ca 2+ -sensing receptors in other organisms [45,46] suggests the potential for a GPCR to mediate the documented increase in intracellular Ca 2+ following exposure to physical and chemical stressors in diatoms [13,14,16]. …”

Section: Discussionmentioning

confidence: 99%

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

et al. 2013

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BackgroundThe G protein-coupled receptor (GPCR) signaling pathway plays an essential role in signal transmission and response to external stimuli in mammalian cells. Protein components of this pathway have been characterized in plants and simpler eukaryotes such as yeast, but their presence and role in unicellular photosynthetic eukaryotes have not been determined. We use a comparative genomics approach using whole genome sequences and gene expression libraries of four diatoms (Pseudo-nitzschia multiseries, Thalassiosira pseudonana, Phaeodactylum tricornutum and Fragilariopsis cylindrus) to search for evidence of GPCR signaling pathway proteins that share sequence conservation to known GPCR pathway proteins.ResultsThe majority of the core components of GPCR signaling were well conserved in all four diatoms, with protein sequence similarity to GPCRs, human G protein α- and β-subunits and downstream effectors. There was evidence for the Gγ-subunit and thus a full heterotrimeric G protein only in T. pseudonana. Phylogenetic analysis of putative diatom GPCRs indicated similarity but deep divergence to the class C GPCRs, with branches basal to the GABAB receptor subfamily. The extracellular and intracellular regions of these putative diatom GPCR sequences exhibited large variation in sequence length, and seven of these sequences contained the necessary ligand binding domain for class C GPCR activation. Transcriptional data indicated that a number of the putative GPCR sequences are expressed in diatoms under various stress conditions in culture, and that many of the GPCR-activated signaling proteins, including the G protein, are also expressed.ConclusionsThe presence of sequences in all four diatoms that code for the proteins required for a functional mammalian GPCR pathway highlights the highly conserved nature of this pathway and suggests a complex signaling machinery related to environmental perception and response in these unicellular organisms. The lack of evidence for some GPCR pathway proteins in one or more of the diatoms, such as the Gγ-subunit, may be due to differences in genome completeness and genome coverage for the four diatoms. The high divergence of putative diatom GPCR sequences to known class C GPCRs suggests these sequences may represent another, potentially ancestral, subfamily of class C GPCRs.

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Section: Discussionmentioning

confidence: 99%

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

et al. 2013

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“…The selective GABA B receptor agonist baclofen, which has been shown to activate G‐protein‐coupled receptors and increase high‐affinity GTPase activity in young hippocampal membranes (Ohmori et al . 1990; Odagaki et al .…”

Section: High‐affinity Gtpase Activitymentioning

confidence: 99%

Kainate receptor agonists and antagonists mediate tolerance to kainic acid and reduce high‐affinity GTPase activity in young, but not aged, rat hippocampus

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Wrightson

Mullaney

et al. 2004

Journal of Neurochemistry

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Domoic acid acts at both kainic acid (KA) and a-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-sensitive glutamate receptors and induces tolerance against subsequent domoic acid insult in young but not aged rat hippocampus. To determine the receptor specificity of this effect, tolerance induction was examined in hippocampal slices from young and aged rats. Slices were preconditioned by exposure to low-dose KA to activate kainate receptors, or the AMPAreceptor selective agonist (S)-5-fluorowillardiine (FW), and following washout, tolerance induction was assessed by administration of high concentrations of KA or FW (respectively). FW preconditioning failed to induce tolerance to subsequent FW challenges, while KA-preconditioned slices were significantly resistant to the effects of high-dose KA. KA preconditioning failed to induce tolerance in aged CA1. Given the lasting nature of the tolerance effect, we examined Gprotein-coupled receptor function. A number of ionotropic KA receptor agonists and antagonists significantly reduced constitutive GTPase activity in hippocampal membranes from young but not aged rats. Furthermore, in young CA1, low concentrations of the AMPA/KA blocker GYKI-52466 also induced tolerance to high-dose KA. Our findings suggest that tolerance is triggered by a selective reduction in constitutive KA-sensitive G-protein activity, and that this potential neuroprotective mechanism is lost with age.

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“…It has been demonstrated that both GTP and GDP inhibit the binding of neurotransmitters to a wide variety of receptors, such as dopaminergic [20], adrenergic [21], serotoninergic [22], purinergic [23], GABAergic [24], muscarinic [25] and opioid [26] receptors. However, in these cases, GMP, cGMP and adenine derivatives had no inhibitory effects, nor did guanine nucleotides modify the binding of the respective antagonists.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of guanine nucleotides on kainic acid binding and on adenylate cyclase activity in chick optic tectum

et al. 1994

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In G protein-coupled receptors, neurotransmitter-induced binding of GTP to G proteins triggers the activation of effector systems while simultaneously decreasing the affinity of the transmitter for its specific binding site within the receptor~G protein complex. In the present study we show that, in the chick optic tectum, guanine nucleotides inhibit the binding of the glutamate analog, kainate, and activate adenylate cyclase by different mechanisms and acting on different sites. GMP-PNP, a non-hydrolyzable analog of GTP, binds tightly to G proteins so that the binding is stable even after exhaustive washing. By use of this property, we have prepared membrane samples in which G protein GTP-binding sites are pre-saturated with GMP-PNP. Experiments carried out with these membranes show that GMP-PNP, GDP-S and GMP inhibit the binding of [3H]kainate by interacting with site(s) unrelated to G proteins, whereas GMP-PNP activates adenylate cyclase activity by binding to G proteins.

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Functional Coupling of the γ‐Aminobutyric Acid_B Receptor with Calcium Ion Channel and GTP‐Binding Protein and Its Alteration Following Solubilization of the γ‐Aminobutyric Acid_B Receptor

Cited by 42 publications

References 15 publications

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

Kainate receptor agonists and antagonists mediate tolerance to kainic acid and reduce high‐affinity GTPase activity in young, but not aged, rat hippocampus

Differential effects of guanine nucleotides on kainic acid binding and on adenylate cyclase activity in chick optic tectum

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Functional Coupling of the γ‐Aminobutyric AcidB Receptor with Calcium Ion Channel and GTP‐Binding Protein and Its Alteration Following Solubilization of the γ‐Aminobutyric AcidB Receptor

Cited by 42 publications

References 15 publications

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

Identification of G protein-coupled receptor signaling pathway proteins in marine diatoms using comparative genomics

Kainate receptor agonists and antagonists mediate tolerance to kainic acid and reduce high‐affinity GTPase activity in young, but not aged, rat hippocampus

Differential effects of guanine nucleotides on kainic acid binding and on adenylate cyclase activity in chick optic tectum

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Functional Coupling of the γ‐Aminobutyric Acid_B Receptor with Calcium Ion Channel and GTP‐Binding Protein and Its Alteration Following Solubilization of the γ‐Aminobutyric Acid_B Receptor