Acetylcholine.
Ontology highlight
ABSTRACT:
SUBMITTER: Brown DA
PROVIDER: S-EPMC1760728 | biostudies-other | 2006 Jan
REPOSITORIES: biostudies-other
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Project description: Not available
| S-EPMC2884600 | biostudies-literature
Project description:Despite extensive studies on nicotinic acetylcholine receptors (nAChRs) and homologues, details of acetylcholine binding are not completely resolved. Here, we report the crystal structure of acetylcholine bound to the receptor homologue acetylcholine binding protein from Lymnaea stagnalis. This is the first structure of acetylcholine in a binding pocket containing all five aromatic residues conserved in all mammalian nAChRs. The ligand-protein interactions are characterized by contacts to the aromatic box formed primarily by residues on the principal side of the intersubunit binding interface (residues Tyr89, Trp143 and Tyr185). Besides these interactions on the principal side, we observe a cation-π interaction between acetylcholine and Trp53 on the complementary side and a water-mediated hydrogen bond from acetylcholine to backbone atoms of Leu102 and Met114, both of importance for anchoring acetylcholine to the complementary side. To further study the role of Trp53, we mutated the corresponding tryptophan in the two different acetylcholine-binding interfaces of the widespread α4β2 nAChR, i.e. the interfaces α4(+)β2(-) and α4(+)α4(-). Mutation to alanine (W82A on the β2 subunit or W88A on the α4 subunit) significantly altered the response to acetylcholine measured by oocyte voltage-clamp electrophysiology in both interfaces. This shows that the conserved tryptophan residue is important for the effects of ACh at α4β2 nAChRs, as also indicated by the crystal structure. The results add important details to the understanding of how this neurotransmitter exerts its action and improves the foundation for rational drug design targeting these receptors.
| S-EPMC3956608 | biostudies-literature
Project description:α-Conotoxin MII (α-CTxMII) is a 16-residue peptide with the sequence GCCSNPVCHLEHSNLC, containing Cys2-Cys8 and Cys3-Cys16 disulfide bonds. This peptide, isolated from the venom of the marine cone snail Conus magus, is a potent and selective antagonist of neuronal nicotinic acetylcholine receptors (nAChRs). To evaluate the impact of channel-ligand interactions on ligand-binding affinity, homology models of the heteropentameric α3β2-nAChR were constructed. The models were created in MODELLER with the aid of experimentally characterized structures of the Torpedo marmorata-nAChR (Tm-nAChR, PDB ID: 2BG9) and the Aplysia californica-acetylcholine binding protein (Ac-AChBP, PDB ID: 2BR8) as templates for the α3- and β2-subunit isoforms derived from rat neuronal nAChR primary amino acid sequences. Molecular docking calculations were performed with AutoDock to evaluate interactions of the heteropentameric nAChR homology models with the ligands acetylcholine (ACh) and α-CTxMII. The nAChR homology models described here bind ACh with binding energies commensurate with those of previously reported systems, and identify critical interactions that facilitate both ACh and α-CTxMII ligand binding. The docking calculations revealed an increased binding affinity of the α3β2-nAChR for α-CTxMII with ACh bound to the receptor, and this was confirmed through two-electrode voltage clamp experiments on oocytes from Xenopus laevis. These findings provide insights into the inhibition and mechanism of electrostatically driven antagonist properties of the α-CTxMIIs on nAChRs.
| S-EPMC4035485 | biostudies-literature
Project description:PurposeThe α7 nicotinic acetylcholine receptor (nAChR) is widely expressed in the nervous system, including in the inner retinal neurons in all species studied to date. Although reductions in the expression of α7 nAChRs are thought to contribute to the memory and visual deficits reported in Alzheimer's disease (AD) and schizophrenia , the α7 nAChR knockout (KO) mouse is viable and has only slight visual dysfunction. The absence of a major phenotypic abnormality may be attributable to developmental mechanisms that serve to compensate for α7 nAChR loss. We hypothesized that the upregulation of genes encoding other nAChR subunits or muscarinic acetylcholine receptor (mAChR) subtypes during development partially accounts for the absence of major deficiencies in the α7 nAChR KO mouse. The purpose of this study was to determine whether the deletion of the α7 nAChR subunit in a mouse model resulted in changes in the regulation of other cholinergic receptors or other ion channels in an α7 nAChR KO mouse when compared to a wild-type (WT) mouse.MethodsTo examine gene expression changes, we employed a quantitative real-time polymerase chain reaction (qPCR) using whole retina RNA extracts as well as RNA extracted from selected regions of the retina. These extracts were collected using laser capture microdissection (LCM). The presence of acetylcholine receptor (AChR) subunit and subtype proteins was determined via western blotting. To determine any differences in the number and distribution of choline acetyltransferase (ChAT) amacrine cells, we employed wholemount and vertical immunohistochemistry (IHC) and cell counting. Additionally, in both WT and α7 nAChR KO mouse retinas, the distribution of the nAChR subunit and mAChR subtype proteins were determined via IHC for those KO mice that experienced mRNA changes.ResultsIn the whole retina, there was a statistically significant upregulation of α2, α9, α10, β4, nAChR subunit, and m1 and m4 mAChR subtype transcripts in the α7 nAChR KO mice. However, the retinal layers showed complex patterns of transcript expression. In the ganglion cell layer (GCL), m2 and m4 mAChR subtype transcripts were significantly upregulated, while β3 and β4 nAChR subunit transcripts were significantly downregulated. In the inner portion of the inner nuclear layer (iINL), α2, α9, β4, nAChR subunit, and m3 and m4 mAChR subtype transcripts were significantly downregulated. In the outer portion of the inner nuclear layer (oINL), β2, β4, and m4 AChR subunit transcripts were significantly upregulated. Western blot experiments confirmed the protein expression of α3-α5 and α9-containing nAChR subunits and m1-m2 mAChR subtypes in mouse retinas. IHC results supported many of the mRNA changes observed. Finally, this is the first report of α9 and α10 nAChR subunit expressions in the retina of any species.ConclusionsRather than a simple upregulation of a single AChR subunit or subtype, the absence of the α7 nAChR in the KO mice was associated with complex layer-specific changes in the expression of AChR subunits and subtypes.
| S-EPMC4169779 | biostudies-literature
Project description:Humans recover from hepatic injury largely by liver regeneration. This complicated process requires hepatocyte proliferation driven by collaboration amongst multiple hepatic cell types. Immune cells also contribute, with some producing mitogenic cytokines such as IL-6 but others damaging hepatocytes by secreting IFNγ. A better understanding of immune cell functions in liver regeneration is necessary to improve clinical interventions. Here, we demonstrate that B cells expressing choline acetyltransferase (ChAT), the enzyme synthesizing acetylcholine (ACh), are specifically required for liver regeneration. Mice lacking ChAT+ B cells subjected to partial hepatectomy (PHX) display greater mortality due to failed liver regeneration. We show that both Kupffer cells and hepatic CD8+ T cells express the α7 nicotinic ACh receptor (nAChR; encoded by Chrna7), and that liver regeneration is also disrupted in mice lacking α7 nAChR. Thus, two regulatory axes promoting hepatocyte proliferation operate following PHX: one where hepatic ChAT+ B cells and α7 nAChR+ Kupffer cells interact to drive IL-6 production by Kupffer cells, and another where ChAT+ B cells and α7 nAChR+ hepatic CD8+ T cells interact to reduce IFNγ production by CD8+ T cells. Our work offers novel insights into liver regeneration mechanisms that may point to new therapies for liver damage.
2025-05-02 | GSE283252 | GEO
Project description:The M3 muscarinic acetylcholine receptor (CHRM3) is predominantly expressed in the basal epidermal layer where it mediates the effects of the auto/paracrine cytotransmitter acetylcholine. Patients with the autoimmune blistering disease pemphigus develop autoantibodies to CHRM3 and show alterations in keratinocyte adhesion, proliferation and differentiation, suggesting that CHRM3 controls these cellular functions. Chrm3 mice display altered epidermal morphology resembling that seen in patients with pemphigus vulgaris. Here, we characterized the cellular and molecular mechanisms whereby CHRM3 controls epidermal structure and function. We used single cell (sc)RNA-seq to evaluate keratinocyte heterogeneity and identify differentially expressed genes in specific subpopulations of epidermal cells in Chrm3 KO neonatal mice.
2022-05-06 | GSE201885 | GEO
Project description:Nicotine elicits bitter taste by activating TRPM5-dependent and TRPM5-independent but neuronal nAChR-dependent pathways. The nAChRs represent common targets at which acetylcholine, nicotine and ethanol functionally interact in the central nervous system. Here, we investigated if the nAChRs also represent a common pathway through which the bitter taste of nicotine, ethanol and acetylcholine is transduced. To this end, chorda tympani (CT) taste nerve responses were monitored in rats, wild-type mice and TRPM5 knockout (KO) mice following lingual stimulation with nicotine free base, ethanol, and acetylcholine, in the absence and presence of nAChR agonists and antagonists. The nAChR modulators: mecamylamine, dihydro-β-erythroidine, and CP-601932 (a partial agonist of the α3β4* nAChR), inhibited CT responses to nicotine, ethanol, and acetylcholine. CT responses to nicotine and ethanol were also inhibited by topical lingual application of 8-chlorophenylthio (CPT)-cAMP and loading taste cells with [Ca2+]i by topical lingual application of ionomycin + CaCl2. In contrast, CT responses to nicotine were enhanced when TRC [Ca2+]i was reduced by topical lingual application of BAPTA-AM. In patch-clamp experiments, only a subset of isolated rat fungiform taste cells exposed to nicotine responded with an increase in mecamylamine-sensitive inward currents. We conclude that nAChRs expressed in a subset of taste cells serve as common receptors for the detection of the TRPM5-independent bitter taste of nicotine, acetylcholine and ethanol.
| S-EPMC4454666 | biostudies-literature
Project description:The conformation of the neurotransmitter acetylcholine bound to the fully functional nicotinic acetylcholine receptor embedded in its native membrane environment has been characterized by using frequency-selective recoupling solid-state NMR. Six dipolar couplings among five resolved (13)C-labeled atoms of acetylcholine were measured. Bound acetylcholine adopts a bent conformation characterized with a quaternary ammonium-to-carbonyl distance of 5.1 A. In this conformation, and with its orientation constrained to that previously determined by us, the acetylcholine could be docked satisfactorily in the agonist pocket of the agonist-bound, but not the agonist-free, crystal structure of a soluble acetylcholine-binding protein from Lymnaea stagnali. The quaternary ammonium group of the acetylcholine was determined to be within 3.9 A of five aromatic residues and its acetyl group close to residues C187/188 of the principle and residue L112 of the complementary subunit. The observed >C O chemical shift is consistent with H bonding to the nicotinic acetylcholine receptor residues gammaY116 and deltaT119 that are homologous to L112 in the soluble acetylcholine-binding protein.
| S-EPMC2084291 | biostudies-literature
Project description:Aggregated amyloid-β causes pathological changes in mixed cultures of neurons and astrocytes such as sporadic cytoplasmic intracellular Ca(2+)-signalling, increase in reactive oxygen species production and cell death. Some of the toxic effects of amyloid-β are mediated through the interaction of the peptide with α7-type nicotinic acetylcholine receptors at the cell surface. Here we demonstrated that affinity purified antibodies to synthetic fragment 173-193 of the α7-subunit of the nAChR are able to protect cells from amyloid-β induced cell death. The antibodies had no effect on the amyloid-β induced calcium signal in astrocytes. However, they significantly reduced amyloid-β induced and NADPH oxidase mediated ROS production. Modulation of the NADPH oxidase activity by either the antibodies, the receptor agonist acetylcholine or the antagonist of the α7-type nicotinic acetylcholine receptors α-bungarotoxin was vital in inhibiting both amyloid-β induced ROS production, caspase 3 cleavage as well as cell death. The uncovered details of the mechanism underlying the action of antibodies to α7-type nicotinic acetylcholine receptors gives additional insight into the involvement of this receptor in Alzheimer's disease pathology and provides a new approach to anti-Alzheimer's disease vaccine design.
| S-EPMC4208291 | biostudies-literature
Project description:Learning in dynamic environments requires animals to not only associate cues with outcomes but also to determine cue salience, which modulates how quickly related associations are updated. While dopamine (DA) in the nucleus accumbens core (NAcc) has been implicated in learning associations, the mechanisms of salience are less understood. Here, we tested the hypothesis that acetylcholine (ACh) in the NAcc encodes cue salience. We conducted four odor discrimination experiments in rats while simultaneously measuring accumbal ACh and DA. We found that ACh developed characteristic dips to cues over learning before DA signals differentiated cues by value, with these dips persisting through value decreases and developing faster during meta-learning. The dips reflected the cue salience across learning stages and tasks, as predicted by a hybrid attentional associative learning model that integrated principles from the Mackintosh and Pearce-Hall models, suggesting that accumbal ACh signals encode salience and potentially gate the learning process.
| S-EPMC11741319 | biostudies-literature