Structure and Function of the Nicotinic Acetylcholine Receptor

Maelicke, Alfred

doi:10.1007/978-3-642-73220-1_10

Cited by 37 publications

(28 citation statements)

References 383 publications

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“…In contrast, the ion channel of nAChR was shown to be formed by the participation of all polypeptides of the nAChR, with a ring of serine, threonine and leucine residues in homologous positions within transmembrane domains M2, serving as elements of a binding site [46, 471. The results of the present study, suggest the existence of yet another ligand-binding site on nAChR, with one of the participating residues identified as Lys125. This residue is located in a prominent consensus sequence present in all nAChR polypeptides sequenced so far, with Lys125 being conserved in nAChR a polypeptides, but being conspicuously absent in non-a polypeptides [48,491. As shown by hydropathy calculations, the region surrounding Lys125 is situated in an amphipathic environment, which may explain why an apparently unusual residue is labeled by the electrophilic radical reaction applied in this study.…”

Section: Discussionmentioning

confidence: 99%

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Schrattenholz¹,

Godovac‐Zimmermann²,

Schäfer

et al. 1993

European Journal of Biochemistry

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The plant alkaloid physostigmine, an established anti-cholinesterase agent of the carbamate type, has recently been shown to bind to the nicotinic acetylcholine receptor from Torpedo marmorutu electrocytes [Okonjo, K. O., Kuhlmann, J. & Maelicke, A. (1991) Eur. J. Biochem. 200, Pharmacological studies of physostigmine-induced ion flux into nicotinic-acetylcholine-receptorrich membrane vesicles, indicated distinct binding sites for physostigmine and acetylcholine. As shown in this study by photoaffinity labeling with [phenyl-(n)-'HI( -)physostigmine, the physostigmine-binding site is located within the same subunit (a polypeptide) of the receptor as the acetylcholine-binding site. Using a variety of proteolytic cleavage conditions for the purified a polypeptide, several ['Hlphysostigmine-labeled peptides were isolated and sequenced. From the radioactivity released in the course of the Edman degradations of the labeled peptides, it was found that the label was associated in all cases with Lys125. These results identify a novel ligand-binding site for the Torpedo nicotinic acetylcholine receptor that is different in location from binding sites identified previously for acetylcholine, its established agonists and antagonists, and di.rect channel blockers.(-)Physostigmine (eserine), the major alkaloid of the calabar bean Physostigma venenosum Balfour [l], is a slowly reversible inhibitor of acetylcholine esterase (AChE), acting by carbamoylation of the active serine residue within the 'esteratic site' of the enzyme [2, 31. This ancient drug [4] continues to be widely used as a diagnostic aid, as an analgesic, in the recovery from anaesthesia, in the treatment of some types of psychosis, for the treatment of alcohol intoxication and glaucoma, and, most recently, for the treatment of acute brain hypoxia IS] and Alzheimer's disease [6, 71. Since physostigmine readily penetrates the bloodhrain barrier, it mainly acts in the braidcentral nervous system. In spite of its wide-spread medical applications and long use in research, however, many of its actions are not yet thoroughly understood, including those at cholinergic and serotonergic synapses [8-141. Evidence has been assembled over the past few years suggesting that, in addition to acting as an inhibitor of AChE, the drug directly interacts with both muscarinic (mAChR) and nicotinic (nAChR) acetylcholine receptors [ 10-141.Studying frog muscle nAChR, we have recently demonstrated that physostigmine, below 1 pM, induces single-channel currents with amplitudes and open-time characteristics typical for the nAChR channel [12,. At higher con- [20, 211. Surprisingly, the direct action of physostigmine at the Torpedo nAChR was unaffected by the presence of saturating concentrations of acetylcholine antagonists, including a bungarotoxin and D-tubocurarine 1201, or when nAChR was desensitized by elevated concentrations of acetylcholine [21]. In addition, we established that two monoclonal antibodies raised against nAChR could competitively inhibit the binding of physostigmi...

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Section: Discussionmentioning

confidence: 99%

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Schrattenholz¹,

Godovac‐Zimmermann²,

Schäfer

et al. 1993

European Journal of Biochemistry

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“…Dale (1914) postulated the existence of two different AChRs, nicotinic receptors (nAChR), activated by ACh and nicotine, blocked by d-tubocurarine, and muscarinic ones (mAChR), activated by ACh and muscarine, blocked by atropine (Gotti et al 1988;Hosey 1992). Molecular biology has shown AChRs to be well-defined cell membrane proteins binding appropriate ligands and propagating signals by coupling to ion channels or second messenger systems, depending on the type of receptor (Maelicke 1988;Hosey 1992). At neuromuscular junctions nAChR activation triggers the muscle action potential, prerequisite of muscle contraction (cf.…”

Section: Cholinergic and Cholinoceptive Structures Are Involved In A mentioning

confidence: 99%

“…Torpedo electric organs have been used to elucidate partial sequences of the subunits, rendering possible the isolation of cDNA clones of nAChR subunit genes from several other species. Muscle nAChRs are pentameric integral membrane proteins with four types of subunits (c~, fi, 7, 6), the smallest, c~, associated with the agonist binding site (Maelicke 1988). Neuronal nAChRs are made up from at least seven different nAChR e-subunits expressed in brain that can combine with at least four fl-subunits to produce different nAChRs (For details see Boulter et al 1987;Whiting et al 1987a;Wada et al 1988;Chini et al 1991).…”

Section: Molecular Biology and Immunology Of Acetylcholine Receptorsmentioning

confidence: 99%

“…Threedimensionally, the nAChR is thought to be a cation channel spanning the membrane with four hydrophobic and one amphipathic segment (Dani 1989;Steinbach and Ifune 1989). Upon binding of ACh to the postsynaptic nAChR, the ionic channel opens and cations pass through depolarizing the postsynaptic neuron or target organ (for details see Maelicke 1988).…”

Section: Molecular Biology and Immunology Of Acetylcholine Receptorsmentioning

confidence: 99%

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Immunohistochemistry of cholinergic receptors

Schröder

1992

Anat Embryol

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Acetylcholine and its receptors are involved in a variety of important signal transduction processes. As shown here paradigmatically for the human neuromuscular junction and the cerebral cortex, acetylcholine receptors can be visualized immunohistochemically at the cellular and subcellular level under physiological and pathological conditions. At normal motor endplates nicotinic cholinoceptors are localized at the surface of the postsynaptic junctional folds. In myasthenic syndromes investigation of muscle biopsies enables the diagnosis of receptor deficiencies at the ultrastructural level. In normal cerebral cortex pyramidal neurons are equipped with both nicotinic and muscarinic acetylcholine receptors localized to postsynaptic densities. In neuropsychiatric diseases cholinoceptor expression can be monitored at the cellular level by quantitative assessment of immunolabeled cortical neurons.

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“…There is good evidence for a significant heterogeneity of nicotine receptors [9,20]. e-Bungarotoxin, although binding to all types of nicotine receptors, blocks rather selectively only the muscle-type nicotine receptors, whereas most of the neuronal-type nicotine receptors are not blocked by this toxin [8,22].…”

Section: Discussionmentioning

confidence: 99%

Nicotinic and muscarinic modulation of 5-hydroxytryptamine (5-HT) release from porcine and canine small intestine

Racké

Schwörer

1992

Clin Investig

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Strips of porcine and canine small intestine were incubated in vitro and the release of 5-hydroxytryptamine (5-HT) was determined by HPLC with electrochemical detection. The spontaneous outflow of 5-HT from the porcine and canine small intestine largely reflects calcium-dependent 5-HT secretion from enterochromaffin cells which are under a spontaneous neuronal, excitatory input as indicated by the inhibitory effect (30-40%) of tetrodotoxin. In both species, nicotine enhanced the release of 5-HT in a concentration-dependent manner by a maximum of about 50% at 100 gM. This effect was blocked by the nicotine receptor antagonist hexamethonium, but not by the subtype-selective nicotine receptor antagonist c~-bungarotoxin. The effect of nicotine was rapidly desensitized. The presence of tetrodotoxin abolished the effect of nicotine on 5-HT release in canine tissue but not in porcine tissue. The presence of the muscarine receptor antagonist scopolamine prevented the effect of nicotine on 5-HT release from canine tissue, but significantly enhanced 5-HT release from porcine tissue. The muscarine receptor agonist oxotremorine inhibited 5-HT release from porcine tissue, but increased 5-HT release from canine tissue. However, in the presence of tetrodotoxin, oxotremorine enhanced 5-HT release in tissue from both species. In conclusion, activation of nicotine receptors induce the release of 5-HT from porcine and canine small intestine. In the dog, the effect of nicotine is mediated via the release of acetylcholine which then stimulates 5-HT release via muscarine receptors on the enterochromaffin cells. In the pig, the stimulatory effect of nicotine appears to be located directly on the enterochromaffin cells. In addition, activation of neuronal muscarine receptors in the porcine small Abbreviations: 5-HT=5-hydroxytryptamine; 5-HIAA=5-hydroxyindoleacetic acid intestine induced the release of a previously unidentified neurotransmitter which inhibited 5-HT release. Nicotine, via cholinergic interneurons, also appears to induce the release of this inhibitory neurotransmitter which opposes the direct stimulatory action of nicotine on 5-HT release.Muscarine -Serotonin 5-Hydroxytryptamine (5-HT, serotonin) is present in high concentrations in the mammalian gastrointestinal tract, predominantly in the enterochromaffin cells [10]. The enterochromaffin cells are dispersed all over the gastrointestinal mucosa and can release 5-HT into the lumen as well as into the portal circulation. During the last few years the mechanisms involved in the regulation of the release of 5-HT from enterochromaffin cells has been characterized in a number of in vitro studies, particularly using the isolated perfused guinea-pig small intestine. These studies have shown that the release of 5-HT from the enterochromaffin cells is controlled by a complex pattern of receptor-mediated mechanisms. Thus, stimulatory effects mediated by nicotine and muscarine receptors [34] or/%adrenoceptors [29] as well as inhibitory effects mediated by VIP [32, 35], c~-adrenocepto...

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Structure and Function of the Nicotinic Acetylcholine Receptor

Cited by 37 publications

References 383 publications

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Immunohistochemistry of cholinergic receptors

Nicotinic and muscarinic modulation of 5-hydroxytryptamine (5-HT) release from porcine and canine small intestine

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