Serotonin receptor 5-HT7 in Drosophila mushroom body neurons mediates larval appetitive olfactory learning

AbstractSerotonin (5-HT) and dopamine are critical neuromodulators known to regulate a range of behaviors in invertebrates and mammals, such as learning and memory. Effects of both serotonin and dopamine are mediated largely through their downstream G-protein coupled receptors through cAMP-PKA signaling. While the role of dopamine in olfactory learning in Drosophila is well described, the function of serotonin and its downstream receptors on Drosophila olfactory learning remain largely unexplored. In this study we show that the output of serotonergic neurons, possibly through points of synaptic contacts on the mushroom body (MB), is essential for training during olfactory associative learning in Drosophila larvae. Additionally, we demonstrate that the regulation of olfactory associative learning by serotonin is mediated by its downstream receptor (d5-HT7) in a cAMP-dependent manner. We show that d5-HT7 expression specifically in the MB, an anatomical structure essential for olfactory learning in Drosophila, is critical for olfactory associative learning. Importantly our work shows that spatio-temporal restriction of d5-HT7 expression to the MB is sufficient to rescue olfactory learning deficits in a d5-HT7 null larvae. In summary, our results establish a critical, and previously unknown, role of d5-HT7 in olfactory learning.

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Functional modulation of PTH1R activation and signalling by RAMP2

10.1101/2021.12.08.471790 ◽

2021 ◽

Author(s):

Katarina Nemec ◽

Hannes Schihada ◽

Gunnar Kleinau ◽

Ulrike Zabel ◽

Eugene O. Grushevskyi ◽

...

Keyword(s):

Homology Modelling ◽

Critical Role ◽

Ion Homeostasis ◽

Optical Biosensors ◽

Dependent Manner ◽

Activated State ◽

Class B ◽

Receptor Activity Modifying Proteins ◽

G Protein Coupled

Receptor-activity-modifying proteins (RAMPs) are ubiquitously expressed membrane proteins that associate with different G protein-coupled receptors (GPCRs) including the parathyroid hormone 1 receptor (PTH1R), a class B GPCR, and an important modulator of mineral ion homeostasis and bone metabolism. However, it is unknown whether and how RAMP proteins may affect PTH1R function. Using different optical biosensors to measure the activation of PTH1R and its downstream signalling, we describe here that RAMP2 acts as a specific allosteric modulator of PTH1R, shifting PTH1R to a unique pre-activated state that permits faster activation in a ligand-specific manner. Moreover, RAMP2 modulates PTH1R downstream signalling in an agonist-dependent manner, most notably increasing the PTH-mediated Gi3 signalling sensitivity. Additionally, RAMP2 increases both PTH- and PTHrP-triggered β-arrestin2 recruitment to PTH1R. Employing homology modelling we describe the putative structural molecular basis underlying our functional findings. These data uncover a critical role of RAMPs in the activation and signalling of a GPCR that may provide a new venue for highly specific modulation of GPCR function and advanced drug design.

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Multifunctional role of GPCR signaling in epithelial tube formation

10.1101/2022.01.06.475238 ◽

2022 ◽

Author(s):

Vishakha Vishwakarma ◽

Thao Phuong Le ◽

SeYeon Chung

Keyword(s):

Rho Kinase ◽

Tube Formation ◽

Dependent Manner ◽

Cortical Actin ◽

Apical Constriction ◽

Gpcr Signaling ◽

Epithelial Tube ◽

Cellular Forces ◽

G Protein Coupled

Epithelial tube formation requires Rho1-dependent actomyosin contractility to generate the cellular forces that drive cell shape changes and rearrangement. Rho1 signaling is activated by G protein-coupled receptor (GPCR) signaling at the cell surface. During Drosophila embryonic salivary gland (SG) invagination, the GPCR ligand Folded gastrulation (Fog) activates Rho1 signaling to drive apical constriction. The SG receptor that transduces the Fog signal into Rho1-dependent myosin activation has not been identified. Here, we reveal that the Smog GPCR transduces Fog signal to regulate Rho kinase accumulation and myosin activation in the apicomedial region of cells to control apical constriction during SG invagination. We also report on unexpected Fog-independent roles for Smog in maintaining epithelial integrity and organizing cortical actin. Our data supports a model wherein Smog regulates distinct myosin pools and actin cytoskeleton in a ligand-dependent manner during epithelial tube formation.

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Immunity-longevity tradeoff neurally controlled by GABAergic transcription factor PITX1/UNC-30

10.1101/2021.02.25.432801 ◽

2021 ◽

Author(s):

Benson Otarigho ◽

Alejandro Aballay

Keyword(s):

Nervous System ◽

Transcription Factor ◽

Caenorhabditis Elegans ◽

G Protein ◽

Neural Control ◽

Dependent Manner ◽

G Protein Coupled ◽

Y Receptors ◽

Neuropeptide Y Receptors

A body of evidence indicates that metazoan immune and aging pathways are largely interconnected, but the mechanisms involved in their homeostatic control remain unclear. In this study, we found that the PITX (paired like homeodomain) transcription factor UNC-30 controls the tradeoff between immunity and longevity from the nervous system in Caenorhabditis elegans. PITX/UNC-30 functional loss enhanced immunity in a GATA/ELT-2- and p38 MAPK/PMK-1-dependent manner and reduced longevity by activating the MXD/MDL-1 and PQM-1 pathways. The immune inhibitory and longevity stimulatory functions of PITX/UNC-30 required the sensory neuron ASG and a neurotransmitter signaling pathway controlled by NPR-1, which is a G protein-coupled receptor related to mammalian neuropeptide Y receptors. Our findings uncovered a suppressive role of GABAergic signaling in the neural control of a biological tradeoff where energy is allocated towards immunity at the expense of longevity.

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G protein-coupled receptor kinase 2 regulates mitochondrial bioenergetics and impairs myostatin-mediated autophagy in muscle cells

AJP Cell Physiology ◽

10.1152/ajpcell.00516.2018 ◽

2019 ◽

Vol 317 (4) ◽

pp. C674-C686 ◽

Cited By ~ 5

Author(s):

Leandro Henrique Manfredi ◽

Joshur Ang ◽

Nesibe Peker ◽

Ruben K. Dagda ◽

Craig McFarlane

Keyword(s):

Skeletal Muscle ◽

G Protein ◽

Mitochondrial Respiration ◽

Autophagic Flux ◽

Dependent Manner ◽

Receptor Kinase ◽

G Protein Coupled Receptor ◽

Protein Loss ◽

G Protein Coupled

G protein-coupled receptor kinase 2 (GRK2) is an important protein involved in β-adrenergic receptor desensitization. In addition, studies have shown GRK2 can modulate different metabolic processes in the cell. For instance, GRK2 has been recently shown to promote mitochondrial biogenesis and increase ATP production. However, the role of GRK2 in skeletal muscle and the signaling mechanisms that regulate GRK2 remain poorly understood. Myostatin is a well-known myokine that has been shown to impair mitochondria function. Here, we have assessed the role of myostatin in regulating GRK2 and the subsequent downstream effect of myostatin regulation of GRK2 on mitochondrial respiration in skeletal muscle. Myostatin treatment promoted the loss of GRK2 protein in myoblasts and myotubes in a time- and dose-dependent manner, which we suggest was through enhanced ubiquitin-mediated protein loss, as treatment with proteasome inhibitors partially rescued myostatin-mediated loss of GRK2 protein. To evaluate the effects of GRK2 on mitochondrial respiration, we generated stable myoblast lines that overexpress GRK2. Stable overexpression of GRK2 resulted in increased mitochondrial content and enhanced mitochondrial/oxidative respiration. Interestingly, although overexpression of GRK2 was unable to prevent myostatin-mediated impairment of mitochondrial respiratory function, elevated levels of GRK2 blocked the increased autophagic flux observed following treatment with myostatin. Overall, our data suggest a novel role for GRK2 in regulating mitochondria mass and mitochondrial respiration in skeletal muscle.

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Microbiota-derived lactate promotes hematopoiesis and erythropoiesis by inducing stem cell factor production from leptin receptor+ niche cells

Experimental & Molecular Medicine ◽

10.1038/s12276-021-00667-y ◽

2021 ◽

Author(s):

Yong-Soo Lee ◽

Tae-Young Kim ◽

Yeji Kim ◽

Seungil Kim ◽

Su-Hyun Lee ◽

...

Keyword(s):

Stem Cell ◽

Stem Cell Factor ◽

Leptin Receptor ◽

Dependent Manner ◽

Hematopoietic Stem ◽

Hematopoietic Recovery ◽

Bm Niche ◽

Acid Producing Bacteria ◽

G Protein Coupled

AbstractAlthough functional interplay between intestinal microbiota and distant sites beyond the gut has been identified, the influence of microbiota-derived metabolites on hematopoietic stem cells (HSCs) remains unclear. This study investigated the role of microbiota-derived lactate in hematopoiesis using mice deficient in G-protein-coupled receptor (Gpr) 81 (Gpr81−/−), an established lactate receptor. We detected significant depletion of total HSCs in the bone marrow (BM) of Gpr81−/− mice compared with heterogenic (Gpr81+/−) mice in a steady state. Notably, the expression levels of stem cell factor (SCF), which is required for the proliferation of HSCs, decreased significantly in leptin receptor-expressing (LepR+) mesenchymal stromal cells (MSCs) around the sinusoidal vessels of the BM from Gpr81−/− mice compared with Gpr81+/− mice. Hematopoietic recovery and activation of BM niche cells after irradiation or busulfan treatment also required Gpr81 signals. Oral administration of lactic acid-producing bacteria (LAB) activated SCF secretion from LepR+ BM MSCs and subsequently accelerated hematopoiesis and erythropoiesis. Most importantly, LAB feeding accelerated the self-renewal of HSCs in germ-free mice. These results suggest that microbiota-derived lactate stimulates SCF secretion by LepR+ BM MSCs and subsequently activates hematopoiesis and erythropoiesis in a Gpr81-dependent manner.

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The neuronal architecture of the mushroom body provides a logic for associative learning

eLife ◽

10.7554/elife.04577 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 450

Author(s):

Yoshinori Aso ◽

Daisuke Hattori ◽

Yang Yu ◽

Rebecca M Johnston ◽

Nirmala A Iyer ◽

...

Keyword(s):

Associative Learning ◽

Learning And Memory ◽

Mushroom Body ◽

Dopaminergic Neuron ◽

Olfactory Learning ◽

Kenyon Cell ◽

Feedforward Network ◽

Kenyon Cells ◽

Functional Logic ◽

Dendritic Arbors

We identified the neurons comprising the Drosophila mushroom body (MB), an associative center in invertebrate brains, and provide a comprehensive map describing their potential connections. Each of the 21 MB output neuron (MBON) types elaborates segregated dendritic arbors along the parallel axons of ∼2000 Kenyon cells, forming 15 compartments that collectively tile the MB lobes. MBON axons project to five discrete neuropils outside of the MB and three MBON types form a feedforward network in the lobes. Each of the 20 dopaminergic neuron (DAN) types projects axons to one, or at most two, of the MBON compartments. Convergence of DAN axons on compartmentalized Kenyon cell–MBON synapses creates a highly ordered unit that can support learning to impose valence on sensory representations. The elucidation of the complement of neurons of the MB provides a comprehensive anatomical substrate from which one can infer a functional logic of associative olfactory learning and memory.

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Learning with naturalistic odor representations in a dynamic model of the Drosophila olfactory system

10.1101/783191 ◽

2019 ◽

Cited By ~ 3

Author(s):

Ann Kennedy

Keyword(s):

Associative Learning ◽

Dynamic Model ◽

Olfactory System ◽

Mushroom Body ◽

Sparse Representations ◽

Olfactory Learning ◽

Associative Memories ◽

Kenyon Cells ◽

Output Neurons ◽

Odor Receptors

AbstractMany odor receptors in the insect olfactory system are broadly tuned, yet insects can form associative memories that are odor-specific. The key site of associative olfactory learning in insects, the mushroom body, contains a population of Kenyon Cells (KCs) that form sparse representations of odor identity and enable associative learning of odors by mushroom body output neurons (MBONs). This architecture is well suited to odor-specific associative learning if KC responses to odors are uncorrelated with each other, however it is unclear whether this hold for actual KC representations of natural odors. We introduce a dynamic model of the Drosophila olfactory system that predicts the responses of KCs to a panel of 110 natural and monomolecular odors, and examine the generalization properties of associative learning in model MBONs. While model KC representations of odors are often quite correlated, we identify mechanisms by which odor-specific associative learning is still possible.

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Identification of novel species-selective agonists of the G-protein-coupled receptor GPR35 that promote recruitment of β-arrestin-2 and activate Gα13

Biochemical Journal ◽

10.1042/bj20101287 ◽

2010 ◽

Vol 432 (3) ◽

pp. 451-459 ◽

Cited By ~ 66

Author(s):

Laura Jenkins ◽

Jose Brea ◽

Nicola J. Smith ◽

Brian D. Hudson ◽

Graeme Reilly ◽

...

Keyword(s):

G Protein ◽

Immune Modulation ◽

Metabolic Disorders ◽

Novel Species ◽

Dependent Manner ◽

G Protein Coupled Receptor ◽

Selective Agonists ◽

G Protein Coupled ◽

Major Impediment

The poorly characterized G-protein-coupled receptor GPR35 has been suggested as a potential exploratory target for the treatment of both metabolic disorders and hypertension. It has also been indicated to play an important role in immune modulation. A major impediment to validation of these concepts and further study of the role of this receptor has been a paucity of pharmacological tools that interact with GPR35. Using a receptor–β-arrestin-2 interaction assay with both human and rat orthologues of GPR35, we identified a number of compounds possessing agonist activity. These included the previously described ligand zaprinast. Although a number of active compounds, including cromolyn disodium and dicumarol, displayed similar potency at both orthologues of GPR35, a number of ligands, including pamoate and niflumic acid, had detectable activity only at human GPR35 whereas others, including zaprinast and luteolin, were markedly selective for the rat orthologue. Previous studies have demonstrated activation of Gα13 by GPR35. A Saccharomyces cerevisiae-based assay employing a chimaeric Gpa1–Gα13 G-protein confirmed that all of the compounds active at human GPR35 in the β-arrestin-2 interaction assay were also able to promote cell growth via Gα13. Each of these ligands also promoted binding of [35S]GTP[S] (guanosine 5′-[γ-[35S]thio]triphosphate) to an epitope-tagged form of Gα13 in a GPR35-dependent manner. The ligands identified in these studies will be useful in interrogating the biological actions of GPR35, but appreciation of the species selectivity of ligands at this receptor will be vital to correctly attribute function.

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Allosteric modulation of ghrelin receptor signaling by lipids

Nature Communications ◽

10.1038/s41467-021-23756-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Marjorie Damian ◽

Maxime Louet ◽

Antoniel Augusto Severo Gomes ◽

Céline M’Kadmi ◽

Séverine Denoyelle ◽

...

Keyword(s):

G Protein ◽

Dependent Manner ◽

Receptor Signaling ◽

Ghrelin Receptor ◽

Protein Activation ◽

G Protein Activation ◽

Preferential Binding ◽

Membrane Components ◽

G Protein Coupled

AbstractThe membrane is an integral component of the G protein-coupled receptor signaling machinery. Here we demonstrate that lipids regulate the signaling efficacy and selectivity of the ghrelin receptor GHSR through specific interactions and bulk effects. We find that PIP2 shifts the conformational equilibrium of GHSR away from its inactive state, favoring basal and agonist-induced G protein activation. This occurs because of a preferential binding of PIP2 to specific intracellular sites in the receptor active state. Another lipid, GM3, also binds GHSR and favors G protein activation, but mostly in a ghrelin-dependent manner. Finally, we find that not only selective interactions but also the thickness of the bilayer reshapes the conformational repertoire of GHSR, with direct consequences on G protein selectivity. Taken together, this data illuminates the multifaceted role of the membrane components as allosteric modulators of how ghrelin signal could be propagated.

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