scholarly journals G protein-coupled receptor trafficking and signaling: new insights into the enteric nervous system

2019 ◽  
Vol 316 (4) ◽  
pp. G446-G452 ◽  
Author(s):  
Simona E. Carbone ◽  
Nicholas A. Veldhuis ◽  
Arisbel B. Gondin ◽  
Daniel P. Poole
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
G Protein ◽  
Molecular Mechanisms ◽  
Intestinal Inflammation ◽  
Receptor Expression ◽  
Enteric Neurons ◽  
Future Research ◽  
Detailed Knowledge ◽  
G Protein Coupled

G protein-coupled receptors (GPCRs) are essential for the neurogenic control of gastrointestinal (GI) function and are important and emerging therapeutic targets in the gut. Detailed knowledge of both the distribution and functional expression of GPCRs in the enteric nervous system (ENS) is critical toward advancing our understanding of how these receptors contribute to GI function during physiological and pathophysiological states. Equally important, but less well defined, is the complex relationship between receptor expression, ligand binding, signaling, and trafficking within enteric neurons. Neuronal GPCRs are internalized following exposure to agonists and under pathological conditions, such as intestinal inflammation. However, the relationship between the intracellular distribution of GPCRs and their signaling outputs in this setting remains a “black box”. This review will briefly summarize current knowledge of agonist-evoked GPCR trafficking and location-specific signaling in the ENS and identifies key areas where future research could be focused. Greater understanding of the cellular and molecular mechanisms involved in regulating GPCR signaling in the ENS will provide new insights into GI function and may open novel avenues for therapeutic targeting of GPCRs for the treatment of digestive disorders.

scholarly journals Hyperglycaemia-Induced Downregulation in Expression of nNOS Intramural Neurons of the Small Intestine in the Pig

2019 ◽  
Vol 20 (7) ◽  
pp. 1681 ◽  
Author(s):  
Michał Bulc ◽  
Katarzyna Palus ◽  
Michał Dąbrowski ◽  
Jarosław Całka
Keyword(s):  
Nitric Oxide ◽  
Nervous System ◽  
Small Intestine ◽  
Enteric Nervous System ◽  
Molecular Mechanisms ◽  
Muscle Relaxation ◽  
Biologically Active ◽  
Enteric Neurons ◽  
Smooth Muscle Relaxation ◽  
Gi Tract

Diabetic autonomic peripheral neuropathy (PN) involves a broad spectrum of organs. One of them is the gastrointestinal (GI) tract. The molecular mechanisms underlying the pathogenesis of digestive complications are not yet fully understood. Digestion is controlled by the central nervous system (CNS) and the enteric nervous system (ENS) within the wall of the GI tract. Enteric neurons exert regulatory effects due to the many biologically active substances secreted and released by enteric nervous system (ENS) structures. These include nitric oxide (NO), produced by the neural nitric oxide synthase enzyme (nNOS). It is a very important inhibitory factor, necessary for smooth muscle relaxation. Moreover, it was noted that nitrergic innervation can undergo adaptive changes during pathological processes. Additionally, nitrergic neurons function may be regulated through the synthesis of other active neuropeptides. Therefore, in the present study, using the immunofluorescence technique, we first examined the influence of hyperglycemia on the NOS- containing neurons in the porcine small intestine and secondly the co-localization of nNOS with vasoactive intestinal polypeptide (VIP), galanin (GAL) and substance P (SP) in all plexuses studied. Following chronic hyperglycaemia, we observed a reduction in the number of the NOS-positive neurons in all intestinal segments studied, as well as an increased in investigated substances in nNOS positive neurons. This observation confirmed that diabetic hyperglycaemia can cause changes in the neurochemical characteristics of enteric neurons, which can lead to numerous disturbances in gastrointestinal tract functions. Moreover, can be the basis of an elaboration of these peptides analogues utilized as therapeutic agents in the treatment of GI complications.

Developmental regulation of GDNF response and receptor expression in the enteric nervous system

Development ◽  
2000 ◽  
Vol 127 (20) ◽  
pp. 4383-4393
Author(s):  
D.S. Worley ◽  
J.M. Pisano ◽  
E.D. Choi ◽  
L. Walus ◽  
C.A. Hession ◽  
...  
Keyword(s):  
Nervous System ◽  
Cell Surface ◽  
Neural Crest ◽  
Enteric Nervous System ◽  
Developmental Stages ◽  
Developmental Regulation ◽  
Precursor Cells ◽  
Receptor Expression ◽  
Enteric Neurons ◽  
Maximal Response

The development of the enteric nervous system is dependent upon the actions of glial cell line-derived neurotrophic factor (GDNF) on neural crest-derived precursor cells in the embryonic gut. GDNF treatment of cultured enteric precursor cells leads to an increase in the number of neurons that develop and/or survive. Here we demonstrate that, although GDNF promoted an increase in neuron number at all embryonic ages examined, there was a developmental shift from a mitogenic to a trophic response by the developing enteric neurons. The timing of this shift corresponded to developmental changes in gut expression of GFR alpha-1, a co-receptor in the GDNF-Ret signaling complex. GFR alpha-1 was broadly expressed in the gut at early developmental stages, at which times soluble GFR alpha-1 was released into the medium by cultured gut cells. At later times, GFR alpha-1 became restricted to neural crest-derived cells. GFR alpha-1 could participate in GDNF signaling when expressed in cis on the surface of enteric precursor cells, or as a soluble protein. The GDNF-mediated response was greater when cell surface, compared with soluble, GFR alpha-1 was present, with the maximal response seen the presence of both cis and trans forms of GFR alpha-1. In addition to contributing to GDNF signaling, cell-surface GFR alpha-1 modulated the specificity of interactions between GDNF and soluble GFR alphas. These experiments demonstrate that complex, developmentally regulated, signaling interactions contribute to the GDNF-dependent development of enteric neurons.

scholarly journals The enteric nervous system of the human and mouse colon at a single-cell resolution

2019 ◽  
Author(s):  
Eugene Drokhlyansky ◽  
Christopher S. Smillie ◽  
Nicholas Van Wittenberghe ◽  
Maria Ericsson ◽  
Gabriel K. Griffin ◽  
...  
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
Single Cell ◽  
Molecular Mechanisms ◽  
Current Model ◽  
Human Colon ◽  
Enteric Neurons ◽  
Stem Cell Maintenance ◽  
Reference Map ◽  
Human And Mouse

AbstractAs the largest branch of the autonomic nervous system, the enteric nervous system (ENS) controls the entire gastrointestinal tract, but remains incompletely characterized. Here, we develop RAISIN RNA-seq, which enables the capture of intact single nuclei along with ribosome-bound mRNA, and use it to profile the adult mouse and human colon to generate a reference map of the ENS at a single-cell resolution. This map reveals an extraordinary diversity of neuron subsets across intestinal locations, ages, and circadian phases, with conserved transcriptional programs that are shared between human and mouse. These data suggest possible revisions to the current model of peristalsis and molecular mechanisms that may allow enteric neurons to orchestrate tissue homeostasis, including immune regulation and stem cell maintenance. Human enteric neurons specifically express risk genes for neuropathic, inflammatory, and extra-intestinal diseases with concomitant gut dysmotility. Our study therefore provides a roadmap to understanding the ENS in health and disease.

Developmental expression of G proteins in a migratory population of embryonic neurons

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 729-742 ◽  
Author(s):  
A.M. Horgan ◽  
M.T. Lagrange ◽  
P.F. Copenhaver
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
G Protein ◽  
G Proteins ◽  
Enteric Neurons ◽  
Developmental Expression ◽  
Heterotrimeric G Proteins ◽  
Aluminium Fluoride ◽  
Related Proteins ◽  
Embryonic Neurons

Directed neuronal migration contributes to the formation of many developing systems, but the molecular mechanisms that control the migratory process are still poorly understood. We have examined the role of heterotrimeric G proteins (guanyl nucleotide binding proteins) in regulating the migratory behavior of embryonic neurons in the enteric nervous system of the moth, Manduca sexta. During the formation of the enteric nervous system, a group of approx. 300 enteric neurons (the EP cells) participate in a precise migratory sequence, during which the undifferentiated cells populate a branching nerve plexus that lies superficially on the visceral musculature. Once migration is complete, the cells then acquire a variety of position-specific neuronal phenotypes. Using affinity-purified antisera against different G protein subtypes, we found no apparent staining for any G protein in the EP cells prior to their migration. Coincident with the onset of migration, however, the EP cells commenced the expression of one particular G protein, Go alpha. The intensity of immunostaining continued to increase as migration progressed, with Go alpha immunoreactivity being detectable in the leading processes of the neurons as well as their somata. The identity of the Go alpha-related proteins was confirmed by protein immunoblot analysis and by comparison with previously described forms of Go alpha from Drosophila. When cultured embryos were treated briefly with aluminium fluoride, a compound known to stimulate the activity of heterotrimeric G proteins, both EP cell migration and process outgrowth were inhibited. The effects of aluminium fluoride were potentiated by alpha toxin, a pore-forming compound that by itself caused no significant perturbations of migration. In preliminary experiments, intracellular injections of the non-hydrolyzable nucleotide GTP gamma-S also inhibited the migration of individual EP cells, supporting the hypothesis that G proteins play a key role in the control of neuronal motility in this system. In addition, once migration was complete, the expression of Go alpha-related proteins in the EP cells underwent a subsequent phase of regulation, so that only certain phenotypic classes among the differentiated EP cells retained detectable levels of Go alpha immunoreactivity. Thus Go may perform multiple functions within the same population of migratory neurons in the course of embryonic development.

scholarly journals Molecular mechanisms of metabotropic GABAB receptor function

2021 ◽  
Vol 7 (22) ◽  
pp. eabg3362
Author(s):  
Hamidreza Shaye ◽  
Benjamin Stauch ◽  
Cornelius Gati ◽  
Vadim Cherezov
Keyword(s):  
G Protein ◽  
Molecular Mechanisms ◽  
Gabab Receptor ◽  
Neurological Diseases ◽  
Activation Mechanism ◽  
Allosteric Modulators ◽  
Inhibitory Neurotransmitter ◽  
Therapeutic Drugs ◽  
G Protein Coupled ◽  
The Brain

Metabotropic γ-aminobutyric acid G protein–coupled receptors (GABAB) represent one of the two main types of inhibitory neurotransmitter receptors in the brain. These receptors act both pre- and postsynaptically by modulating the transmission of neuronal signals and are involved in a range of neurological diseases, from alcohol addiction to epilepsy. A series of recent cryo-EM studies revealed critical details of the activation mechanism of GABAB. Structures are now available for the receptor bound to ligands with different modes of action, including antagonists, agonists, and positive allosteric modulators, and captured in different conformational states from the inactive apo to the fully active state bound to a G protein. These discoveries provide comprehensive insights into the activation of the GABAB receptor, which not only broaden our understanding of its structure, pharmacology, and physiological effects but also will ultimately facilitate the discovery of new therapeutic drugs and neuromodulators.

scholarly journals Rgs4 is a regulator of mTOR activity required for motoneuron axon outgrowth and neuronal development in zebrafish

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aya Mikdache ◽  
Marie-José Boueid ◽  
Lorijn van der Spek ◽  
Emilie Lesport ◽  
Brigitte Delespierre ◽  
...  
Keyword(s):  
Nervous System ◽  
G Protein ◽  
Neural Development ◽  
Neuronal Development ◽  
Axon Outgrowth ◽  
Rgs Proteins ◽  
Protein Signaling ◽  
Loss Of Function ◽  
G Protein Coupled

AbstractThe Regulator of G protein signaling 4 (Rgs4) is a member of the RGS proteins superfamily that modulates the activity of G-protein coupled receptors. It is mainly expressed in the nervous system and is linked to several neuronal signaling pathways; however, its role in neural development in vivo remains inconclusive. Here, we generated and characterized a rgs4 loss of function model (MZrgs4) in zebrafish. MZrgs4 embryos showed motility defects and presented reduced head and eye sizes, reflecting defective motoneurons axon outgrowth and a significant decrease in the number of neurons in the central and peripheral nervous system. Forcing the expression of Rgs4 specifically within motoneurons rescued their early defective outgrowth in MZrgs4 embryos, indicating an autonomous role for Rgs4 in motoneurons. We also analyzed the role of Akt, Erk and mechanistic target of rapamycin (mTOR) signaling cascades and showed a requirement for these pathways in motoneurons axon outgrowth and neuronal development. Drawing on pharmacological and rescue experiments in MZrgs4, we provide evidence that Rgs4 facilitates signaling mediated by Akt, Erk and mTOR in order to drive axon outgrowth in motoneurons and regulate neuronal numbers.

G-protein-coupled receptors signalling at the cell nucleus: an emerging paradigmThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell.

2006 ◽  
Vol 84 (3-4) ◽  
pp. 287-297 ◽  
Author(s):  
Fernand Gobeil ◽  
Audrey Fortier ◽  
Tang Zhu ◽  
Michela Bossolasco ◽  
Martin Leduc ◽  
...  
Keyword(s):  
G Protein ◽  
Cell Nucleus ◽  
Intracellular Signaling ◽  
Molecular Mechanisms ◽  
Nuclear Translocation ◽  
Cell Metabolism ◽  
Hormone Secretion ◽  
G Protein Coupled Receptors ◽  
A Cell ◽  
G Protein Coupled

G-protein-coupled receptors (GPCRs) comprise a wide family of monomeric heptahelical glycoproteins that recognize a broad array of extracellular mediators including cationic amines, lipids, peptides, proteins, and sensory agents. Thus far, much attention has been given towards the comprehension of intracellular signaling mechanisms activated by cell membrane GPCRs, which convert extracellular hormonal stimuli into acute, non-genomic (e.g., hormone secretion, muscle contraction, and cell metabolism) and delayed, genomic biological responses (e.g., cell division, proliferation, and apoptosis). However, with respect to the latter response, there is compelling evidence for a novel intracrine mode of genomic regulation by GPCRs that implies either the endocytosis and nuclear translocation of peripheral-liganded GPCR and (or) the activation of nuclearly located GPCR by endogenously produced, nonsecreted ligands. A noteworthy example of the last scenario is given by heptahelical receptors that are activated by bioactive lipoids (e.g., PGE2 and PAF), many of which may be formed from bilayer membranes including those of the nucleus. The experimental evidence for the nuclear localization and signalling of GPCRs will be reviewed. We will also discuss possible molecular mechanisms responsible for the atypical compartmentalization of GPCRs at the cell nucleus, along with their role in gene expression.

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