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Daly JW. Thirty years of discovering arthropod alkaloids in amphibian skin. JOURNAL OF NATURAL PRODUCTS 1998; 61:162-172. [PMID: 9461669 DOI: 10.1021/np970460e] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Amphibian skin has provided a wide range of biologically active alkaloids. During the past 30 years, over 400 alkaloids of over 20 structural classes have been detected. These include the batrachotoxins, which are potent and selective activators of sodium channels, the histrionicotoxins, which are potent noncompetitive blockers of nicotinic receptor-gated channels, the pumiliotoxins and related allo- and homo-pumiliotoxins, which have myotonic and cardiotonic activity due to effects on sodium channels, and epibatidine, which has potent antinociceptive activity due to agonist activity at nicotinic receptors. Further classes of alkaloids from amphibian skin include pyrrolidines and piperidines, decahydroquinolines, pyrrolizidines, various indolizidines, quinolizidines, and tricyclic gephyrotoxins, pyrrolizidine oximes, pseudophrynamines, coccinellines, and cyclopentaquinolizidines. Most alkaloids of amphibian skin appear to be sequestered from dietary arthropods. The source of the batrachotoxins, histrionicotoxins, pumiliotoxins, epibatidine, and certain izidines are unknown.
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Affiliation(s)
- J W Daly
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Arias HR. Luminal and non-luminal non-competitive inhibitor binding sites on the nicotinic acetylcholine receptor. Mol Membr Biol 1996; 13:1-17. [PMID: 9147657 DOI: 10.3109/09687689609160569] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The nicotinic acetylcholine receptor presents two very well differentiated domains for ligand binding that account for different cholinergic properties. In the hydrophilic extracellular region of the alpha subunit exist the binding sites for agonists such as the neurotransmitter acetylcholine, which upon binding trigger the channel opening, and for competitive antagonists such as d-tubocurarine, which compete for the former inhibiting its pharmacological action. For non-competitive inhibitors, a population of low-affinity binding sites have been found at the lipid-protein interface of the nicotinic acetylcholine receptor. In addition, at the M2 transmembrane domain, several high-affinity binding sites have been found for non-competitive inhibitors such as chlorpromazine, triphenylmethylphosphonium, the local anaesthetic QX-222 and the hydrophobic probe trifluoromethyl-iodophenyldiazirine. They are known as luminal binding sites. Although the local anaesthetic meproadifen seems to be located between the hydrophobic domains M2-M3, this locus is considered to form part of the channel mouth, thus this site can also be called a luminal binding site. In contraposition, experimental evidences support the hypothesis of the existence of other high-affinity binding sites for non-competitive inhibitors located not at the channel lumen, but at non-luminal binding domains. Among them, we can quote the binding site for quinacrine, which is located at the lipid-protein interface of the alpha M1 domain, and the binding site for ethidium, which is believed to interact with the wall of the vestibule very far away from both the lumen channel and the lipid membrane surface. The aim of this review is to discuss these recent findings relative to both structurally and functionally relevant aspects of non-competitive inhibitors of the nicotinic acetylcholine receptor. We will put special emphasis on the description of the localization of molecules with non-competitive antagonist properties that bind with high-affinity to luminal and non-luminal domains. The information described herein was principally obtained by means of methods such as photolabelling and site-directed mutagenesis in combination with patch-clamp. Our laboratory has contributed with data obtained by using biophysical approaches such as paramagnetic electron spin resonance and quantitative fluorescence spectroscopy.
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Affiliation(s)
- H R Arias
- Instituto de Investigaciones Bioquimicas de Bahia Blanca, Argentina
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Vickroy TW, Malphurs WL. Irreversible blockade of high-affinity choline uptake in rat brain by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). Biochem Pharmacol 1994; 48:1281-7. [PMID: 7945422 DOI: 10.1016/0006-2952(94)90166-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
N-Ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), an agent that causes irreversible covalent modification of protein carboxyl residues, has been used previously to produce irreversible occlusion of neurotransmitter receptors as well as other cellular proteins. The present investigation was undertaken to ascertain the mechanism by which EEDQ inhibits stimulus-dependent acetylcholine (ACh) release from rat brain hippocampal synaptosomes. Brief pretreatment with EEDQ (up to 100 microM) eliminated completely calcium-evoked [3H]acetylcholine ([3H]ACh) release and reduced de novo synthesis of transmitter by greater than 90%. Studies revealed that pretreatment with EEDQ in vitro caused a time- and concentration-dependent inhibition of high-affinity [3H]choline uptake (HACU) by synaptosomes. EEDQ-induced inhibition of HACU was not reversed by repeated tissue washing; however, co-incubation with hemicholinium-3, a highly specific and reversible inhibitor of HACU, protected against EEDQ-induced inhibition of HACU, as well as the loss of stimulus-dependent [3H]-ACh release. In vivo administration of EEDQ (20 mg/kg, s.c.) to rats caused marked reductions (46-65%) in synaptosomal HACU as well as the number of membrane binding sites for the muscarinic cholinergic antagonist L-[benzilic-4,4'-3H]quinuclidinyl benzilate ([3H]QNB) in the hippocampus and striatum. Treatment with atropine (100 mg/kg) prevented the reduction in [3H]QNB binding but did not influence EEDQ-induced inhibition of HACU. Taken together, these results indicate that EEDQ causes a direct and irreversible inhibition of high-affinity choline transporters on CNS cholinergic nerve terminals and, therefore, may be a useful investigational tool for characterization of the turnover and regulation of this transporter protein in vivo.
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Affiliation(s)
- T W Vickroy
- Department of Physiological Sciences, University of Florida, Gainesville 32610-0144
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Johnson DA, Nuss JM. The histrionicotoxin-sensitive ethidium binding site is located outside of the transmembrane domain of the nicotinic acetylcholine receptor: a fluorescence study. Biochemistry 1994; 33:9070-7. [PMID: 8049208 DOI: 10.1021/bi00197a007] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A novel, relatively photostable, long-wavelength fluorescent membrane probe, N-(Texas Red sulfonyl)-5(and 6)-dodecanoylamine (C12-Texas Red), was synthesized and used as an electronic energy acceptor for Förster fluorescence resonance energy transfer (FRET) between ethidium bound to a histrionicotoxin-sensitive binding site on the Torpedo nicotinic acetylcholine receptor (AChR) and the lipid membrane surface. FRET from membrane-partitioned 5-(N-dodecanoylamino)fluorescein (C12-fluorescein) to the membrane-partitioned C12-Texas Red was also determined with a parallel set of cuvettes to (1) compare FRET results with a donor in a known position in the membrane and (2) assess the surface density of the membrane-partitioned C12-Texas Red. Stern-Volmer analysis of the FRET results showed that C12-Texas Red quenched membrane-partitioned C12-fluorescein fluorescence 2.9 times more effectively than it quenched the receptor-bound ethidium fluorescence even though the Förster critical distances for the two donor-acceptor pairs were very similar (49.9 and 54.3 A, respectively). Analysis of the ethidium to C12-Texas Red FRET as a function of acceptor surface density with the assumptions that the donor is attached along the major axis of symmetry of a cylindrical protein embedded perpendicularly into the membrane (On-Axis FRET model) suggested that the distance of closest approach between the receptor-bound ethidium and the membrane surface was approximately 52 A. Because the minimum distance between the surface of the lipid-membrane domain and the major symmetry axis of the AChR is approximately 28 A, the FRET results strongly suggest that the ethidium binding site is not located near the entrance of the luminal transmembrane domain is generally assumed.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D A Johnson
- Division of Biomedical Sciences, University of California, Riverside 92521-0121
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Ochoa EL, Chattopadhyay A, McNamee MG. Desensitization of the nicotinic acetylcholine receptor: molecular mechanisms and effect of modulators. Cell Mol Neurobiol 1989; 9:141-78. [PMID: 2663167 DOI: 10.1007/bf00713026] [Citation(s) in RCA: 161] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. Loss of response after prolonged or repeated application of stimulus is generally termed desensitization. A wide variety of phenomena occurring in living organisms falls under this general definition of desensitization. There are two main types of desensitization processes: specific and non-specific. 2. Desensitization of the nicotinic acetylcholine receptor is triggered by prolonged or repeated exposure to agonists and results in inactivation of its ion channel. It is a case of specific desensitization and is an intrinsic molecular property of the receptor. 3. Desensitization of the nicotinic acetylcholine receptor at the neuromuscular junction was first reported by Katz and Thesleff in 1957. Desensitization of the receptor has been demonstrated by rapid kinetic techniques and also by the characteristic "burst kinetics" obtained from single-channel recordings of receptor activity in native as well as in reconstituted membranes. In spite of a number of studies, the detailed molecular mechanism of the nicotinic acetylcholine receptor desensitization is not known with certainty. The progress of desensitization is accompanied by an increase in affinity of the receptor for its agonist. This change in affinity is attributed to a conformational change of the receptor, as detected by spectroscopic and kinetic studies. A four-state general model is consistent with the major experimental observations. 4. Desensitization of the nicotinic acetylcholine receptor can be potentially modulated by exogenous and endogenous substances and by covalent modifications of the receptor structure. Modulators include the noncompetitive blockers, calcium, the thymic hormone peptides (thymopoietin and thymopentin), substance P, the calcitonin gene-related peptide, and receptor phosphorylation. Phosphorylation is an important posttranslational covalent modification that is correlated with the regulation and desensitization of the receptor through various protein kinases. 5. Although the physiological significance of desensitization of the nicotinic receptor is not yet fully understood, desensitization of receptors probably plays a significant role in the operation of the neuronal networks associated in memory and learning processes. Desensitization of the nicotinic receptor could also possibly be related to the neuromuscular disease, myasthenia gravis.
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Affiliation(s)
- E L Ochoa
- Department of Biochemistry and Biophysics, University of California, Davis 95616
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Hallowed SF, Rechnitz GA. Enzyme-Amplified Receptor Assay (ERA): A Novel Approach to Drug Detection. ANAL LETT 1987. [DOI: 10.1080/00032718708078037] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Oliveira L, Madsen BW, Kapai N, Sherby SM, Swanson KL, Eldefrawi ME, Albuquerque EX. Interaction of narcotic antagonist naltrexone with nicotinic acetylcholine receptor. Eur J Pharmacol 1987; 140:331-42. [PMID: 3653249 DOI: 10.1016/0014-2999(87)90290-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The interactions of naltrexone with the nicotinic acetylcholine receptor were studied electrophysiologically using the frog sciatic nerve-sartorius muscle and biochemically using membranes from the electric organ of Torpedo ocellata. At nanomolar concentrations naltrexone increased the peak amplitude of endplate currents with little change in the decay time constant. At micromolar concentrations there was a concentration-dependent depression of endplate current and miniature endplate current amplitudes and decay time constants. Decay time constant depression was enhanced with hyperpolarization. Only marginal curvature was induced in peak endplate current amplitude versus membrane voltage plots by naltrexone. Naltrexone had no effect on single channel conductance but decreased open channel lifetime, according to fluctuation analysis. Naltrexone alone (less than or equal to 3 microM) did not impair binding of [125I]alpha-bungarotoxin to the receptor in a fast pre-equilibration assay, but increased the ability of acetylcholine to displace [125I]alpha-bungarotoxin. The drug displaced the agonist-stimulated binding of [3H]perhydrohistrionicotoxin to the channel site. Biphasic functional changes in neuromuscular transmission can be attributed to an allosteric mechanism with increased agonist binding to the nicotinic receptor at nanomolar concentrations and caused a non-competitive blockade of the ionic channel at micromolar concentrations.
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Affiliation(s)
- L Oliveira
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201
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Mansour NA, Valdes JJ, Shamoo AE, Annau Z. Biochemical interactions of carbamates and ecothiophate with the activated conformation of nicotinic acetylcholine receptor. JOURNAL OF BIOCHEMICAL TOXICOLOGY 1987; 2:25-42. [PMID: 3508476 DOI: 10.1002/jbt.2570020104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Purified Torpedo nobiliana electric organ acetylcholine receptor (AChR) was reconstituted into membranes containing natural phospholipids supplemented with cholesterol (25% w/w). The reconstituted system facilitates the study of the effects of drugs on the regulation of the AChR channel complex under both resting and carbachol (carb)-stimulated conditions. Neostigmine (Neo) was the only carbamate to induce activation of [3-H]-phencyclidine ([3-H]-PCP) binding to the channel sites, acting as a weak agonist. The activation of [3-H]-PCP binding is dependent upon the nature of the reconstituted systems, with carb/Neo activation ratios of 8, 3, and 1 for the intact purified AChR vesicles fraction (PVF), the PVF reconstituted in phospholipid/cholesterol (CRPVF), and the PVF reconstituted in phospholipid (RPVF), respectively. The carbamates Neo, physostigmine (Physo), and pyridostigmine (Pyrido) inhibited carb-activated [3-H]-PCP binding with Ki values of 10, 20, and 1,600 microM, respectively. The inhibition was mixed competitive-noncompetitive in nature. The characteristic response of CRPVF to carb-stimulated [22-Na] influx was inhibited by the three carbamates, with IC-50 values of 6, 50, and 1,000 microM for Neo, Physo, and Pyrido, respectively. The quaternary ammonium organophosphate ecothiophate (Eco) inhibited carb-stimulated [22-Na] influx with potency similar to that of Neo. Preincubation of AChR preparation with the carbamates and ecothiophate caused a reduction in the binding of [125-I]-alpha-bungarotoxin ([125-I]-alpha-BGT) with the following decreasing order of potency: Neo less than Physo less than Eco less than Pyrido. Calcium has a direct modulatory role on the time-course inhibition of [125-I]-alpha-BGT binding by these drugs. While we observed a high potency of Neo and Physo in inhibiting [125-I]-alpha-BGT binding, it was undetectable for the carbamate insecticide 2-methyl-2-(methylthio)propionaldehyde-O-(methylcarbamoyl)oxime (aldicarb). These data suggest that the potent anticholinesterase carbamate agents interact differently with the AChR and its ionic channel. Their interactions with the nicotinic AChR channel system can be described as (a) weakly agonist, (b) directly acting on the open conformation of the channel, and (c) blocking the AChR-binding sites.
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Affiliation(s)
- N A Mansour
- Department of Environmental Health Sciences, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, MD 21205
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Abstract
The antiviral drug amantadine has anticholinergic effects in the guinea-pig atrium at concentrations greater than 1 X 10(-4)M. It is a competitive inhibitor of [3H]-quinuclidinyl benzilate binding to the muscarinic receptor, but antagonizes the negative inotropic effect of acetylcholine in a non-competitive manner. It increases the duration of the atrial action potential and also increases the force of atrial contraction. These effects are evident at approximately 10 times lower concentrations than the antimuscarinic effects. The increase in contractility can be reversed by propranolol (5 X 10(-7)M) but the increase in action potential duration is potentiated by propranolol. Shortening of the action potential duration by acetylcholine was reversed by amantadine, but at approximately ten times lower levels than were needed to reduce the negative inotropic effect. Interactions between beta adrenoceptor binding of [3H]-dihydroalprenolol and amantadine could not be demonstrated. Similarly, binding of [3H]-nitrendipine to the calcium channel is not influenced. It is suggested that amantadine may exert its positive inotropic effect by interaction with the potassium channel, causing a delay in outward current.
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Akasu T, Karczmar AG, Koketsu K. Effects of serotonin (5-hydroxytryptamine) on amphibian neuromuscular junction. Eur J Pharmacol 1983; 88:63-70. [PMID: 6602056 DOI: 10.1016/0014-2999(83)90392-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A study of the effects of serotonin transmission was carried out on the frog neuromuscular junction by means of microelectrode methods. Serotonin was employed in concentrations of 5-100 microM. Serotonin did not affect membrane characteristics or the resting potential whether at non-neuronal (muscular fiber) or endplate segments of the junction. While serotonin did not affect the frequency of the miniature endplate potentials (MEPPs), it significantly decreased evoked release of acetylcholine. Serotonin significantly decreased, in a dose-dependent fashion, the amplitude of acetylcholine potentials, endplate currents (EPCs), endplate potentials (EPPs) and MEPPs. Also, serotonin shortened significantly the EPC time course and half-decay time, and caused loss of membrane voltage sensitivity of the half-decay time. While it did not affect the null potential, serotonin changed the voltage-EPC relationship from linear to non-linear, and markedly attenuated the dependence of EPC amplitude on membrane potential. These results demonstrate that serotonin induces depressant effects at both pre- and post-synaptic sites of amphibian neuromuscular junction and that its post-synaptic action is directed at the receptor-channel macromolecule rather than at either the channel or the receptor alone.
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Chapter 5 Amphibian Alkaloids. ACTA ACUST UNITED AC 1983. [DOI: 10.1016/s0099-9598(08)60051-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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Ohta Y, Akasu T, Karczmar AG. The mechanism of the anti-desensitizing action of sodium fluoride at the amphibian neuromyal junction. Neuropharmacology 1982; 21:861-75. [PMID: 6815547 DOI: 10.1016/0028-3908(82)90077-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Greenberg M, Tsong TY. Binding of quinacrine, a fluorescent local anesthetic probe, to mammalian axonal membranes. Evidence for a local anesthetic receptor site. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34227-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Lauffer L, Hucho F. Triphenylmethylphosphonium is an ion channel ligand of the nicotinic acetylcholine receptor. Proc Natl Acad Sci U S A 1982; 79:2406-9. [PMID: 6285383 PMCID: PMC346203 DOI: 10.1073/pnas.79.7.2406] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The lipophilic cation triphenylmethylphosphonium (Ph3MeP+), which is widely used as a sensor for membrane potential with cells, organelles, and membrane vesicles, is shown also to accumulate in membranes rich in nicotinic acetylcholine receptor in a voltage-independent way. Evidence is presented that Ph3MeP+ in this system is bound to a cation-binding site of the ion channel that is part of the acetylcholine receptor complex. Binding is stimulated by cholinergic effectors (Kd = 13 microM in the absence of carbamoylcholine; Kd = 1.5 microM in the presence of 10 microM carbamoylcholine), and this stimulation is blocked by alpha-bungarotoxin. Ph3MeP+ blocks efflux of 22Na from receptor-rich microsacs and appears to compete with the channel ligand phencyclidine for a common binding site. In contrast to the binding of other proven channel ligands, Ph3MeP+-binding is not affected by desensitization.
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Miller KW, Sauter JF, Braswell LM. A stereoselective pentobarbital binding site in cholinergic membranes from Torpedo californica. Biochem Biophys Res Commun 1982; 105:659-66. [PMID: 7092877 DOI: 10.1016/0006-291x(82)91485-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Daly JW. Alkaloids of neotropical poison frogs (Dendrobatidae). FORTSCHRITTE DER CHEMIE ORGANISCHER NATURSTOFFE = PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS. PROGRES DANS LA CHIMIE DES SUBSTANCES ORGANIQUES NATURELLES 1982; 41:205-340. [PMID: 7049875 DOI: 10.1007/978-3-7091-8656-5_6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Tarrab-Hazdai R, Goldfarb V. Isolation and characterization of a lipid-embedded domain of the acetylcholine receptor from Torpedo californica. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 121:545-51. [PMID: 7056257 DOI: 10.1111/j.1432-1033.1982.tb05821.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Albuquerque EX, Warnick JE, Mayer RF, Eldefrawi AT, Eldefrawi ME. Recent advances in the molecular mechanisms of human and animal models of myasthenia gravis. Ann N Y Acad Sci 1981; 377:496-518. [PMID: 6280564 DOI: 10.1111/j.1749-6632.1981.tb33756.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The receptor-channel molecule is a dynamic system which exists in multiple conformations and that is the way we should think of it when we study antibody interaction with the molecule. The results presented here suggest that some antibodies may affect receptor function by occupying sites other than the receptor site. Some of these sites may by exposed only in certain conformations, and occupation of some site by antibodies may effect conformational changes. These small but perhaps important differences in cholinergic channel properties of the myasthenic muscle from the normal one are revealed by studying the effect of myasthenic sera on drug interactions with the channel sites. The sera of myasthenics are able to react with certain channel conformations and are able to affect the interaction of channel antagonists such as H12HTX and QNB. The sera appear to act preferentially with the open conformation of the channel. As a consequence of such an effect, important conformational changes of the channel may fail to occur upon activation.
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Heidmann T, Changeux JP. Stabilization of the high affinity state of the membrane-bound acetylcholine receptor from Torpedo marmorata by noncompetitive-blockers. Evidence for dual interaction and pharmacological selectivity. FEBS Lett 1981; 131:239-44. [PMID: 7297675 DOI: 10.1016/0014-5793(81)80375-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Desouki A, Eldefrawi AT, Eldefrawi ME. A new mechanism revealed for the action of antibodies on acetylcholine receptor function. Exp Neurol 1981; 73:440-50. [PMID: 7262247 DOI: 10.1016/0014-4886(81)90278-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Eldefrawi ME, Warnick JE, Schofield GG, Albuquerque EX, Eldefrawi AT. Interaction of imipramine with the ionic channel of the acetylcholine receptor of motor endplate and electric organ. Biochem Pharmacol 1981; 30:1391-4. [PMID: 6268097 DOI: 10.1016/0006-2952(81)90331-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Regulation of [3H]perhydrohistrionicotoxin binding to Torpedo ocellata electroplax by effectors of the acetylcholine receptor. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)69691-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Heidmann T, Changeux JP. Interaction of a fluorescent agonist with the membrane-bound acetylcholine receptor from Torpedo marmorata in the millisecond time range: resolution of an "intermediate" conformational transition and evidence for positive cooperative effects. Biochem Biophys Res Commun 1980; 97:889-96. [PMID: 7470156 DOI: 10.1016/0006-291x(80)91460-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Eldefrawi ME, Eldefrawi AT. Coupling between the nicotinic acetylcholine receptor site and the ionic channel site. Ann N Y Acad Sci 1980; 358:239-52. [PMID: 6259991 DOI: 10.1111/j.1749-6632.1980.tb15398.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Eldefrawi ME, Eldefrawi AT, Aronstam RS, Maleque MA, Warnick JE, Albuquerque EX. [3H]Phencyclidine: a probe for the ionic channel of the nicotinic receptor. Proc Natl Acad Sci U S A 1980; 77:7458-62. [PMID: 6261260 PMCID: PMC350523 DOI: 10.1073/pnas.77.12.7458] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
To evaluate [3H]phencyclidine ([3H]PCP)as a probe for the ionic channel of the nicotinic receptor, the characteristics of its binding to electric organ membranes od Torpedo ocellata and its effects on frog sartorius muscle were studied. Similar to PCP, [3H]PCP depressed the peak amplitude of endplate current, caused nonlinearity in the voltage-current relationship at negative potentials, accelerated the decay time of the end-plate current, and shortened the channel lifetime. Thus, [3H]PCP interacted with the ionic channel of the nicotinic receptor, although there were a few differences between its effect and that of PCP. Binding of [3H]PCP to Torpedo membranes was to sites on the ionic channel of acetylcholine (AcCho) receptor because it was saturable, dependent upon protein concentration, and inhibited by drugs that interact with the ionic channel, and the initial rate of binding was potentiated by receptor agonists. Equilibrium binding of [3H]PCP to Torpedo membranes was with two affinities, but in the presence of AcCho, [3H]PCP binding was with a single affinity. The affinities of channel drugs obtained by inhibition of binding of [3H]PCP and [3H[perhydrohistrionicotoxin to Torpedo membranes were different, with correlation coefficients of 0.52 and 0.82 in the absence and presence of a receptor agonist, respectively; this suggests differences in their binding sites on the ionic channel of the AcCho receptor.
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Albuquerque EX, Adler M, Spivak CE, Aguayo L. Mechanism of nicotinic channel activation and blockade. Ann N Y Acad Sci 1980; 358:204-38. [PMID: 6259990 DOI: 10.1111/j.1749-6632.1980.tb15397.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Epstein N, Hess GP, Kim PS, Noble RL. Inactivation (desensitization) of the acetylcholine receptor in Electrophorus electricus membrane vesicles by carbamylcholine: comparison between ion flux and alpha-bungarotoxin binding. J Membr Biol 1980; 56:133-7. [PMID: 7441723 DOI: 10.1007/bf01875964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The inactivation (desensitization) of the acetylcholine receptor by carbamylcholine, a stable analogue of acetylcholine, has been investigated in eel Ringer's solution, pH 7.0, 0 degrees C, by measurements of (i) ion flux and (ii) the kinetics of the reaction of [125I]-alpha-bungarotoxin with the receptor. The effect of preincubation with carbamylcholine is significantly different in the two types of measurement. In both the receptor-controlled flux of inorganic ions and the toxin-binding kinetics a biphasic process has been observed (Hess, G.P., Lipkowitz, S., Struve, G.E., 1978, Proc. Nat. Acad. Sci. USA 75:1703; Hess, G.P. et al., 1975, Biochem. Biophys. Res. Commun. 64:1018; Bulger, J.E. et al., 1977, Biochemistry 16:684), only the initial fast phase of which is inhibited and the subsequent slow phase persists. However, preincubation with carbamylcholine per se has no effect on the toxin reaction. The results obtained are consistent with the proposal of Katz and Thesleff (Katz, B., Thesleff, S., 1957, J. Physiol. (London) 138:65) that the active form of the receptor is converted to an inactive form in the presence of acetylcholine receptor ligands, and with our previous experiments (Hess et al., 1978) which indicated that one receptor form is responsible for the initial fast phase of both the receptor-controlled ion flux and the toxin binding reaction, and that its conversion to the other form results in the slow phases in these two measurements.
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Sobel A, Heidmann T, Cartaud J, Changeux JP. Reconstitution of a functional acetylcholine receptor. Polypeptide chains, ultrastructure, and binding sites for acetylcholine and local anesthetics. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 110:13-33. [PMID: 7439153 DOI: 10.1111/j.1432-1033.1980.tb04838.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The 'reconstitution cycle' is composed of the following sequence of operations. Highly purified receptor-rich membranes prepared from Torpedo marmorata electric organ are exposed to pH 11 to remove the 43,000-Mr protein and dispersed into solution by sodium cholate under conditions where more than 85% of the receptor protein is in its 9-S form. Elimination of the detergent by filtration on a Sephadex column (or dialysis) yields a 'reconstituted receptor' fraction, under conditions which conserve part of the endogenous lipids, or 'reconstituted vesicles' in the presence of an excess of exogenous lipids. The polypeptide composition of these fractions was analysed by sodium dodecylsulfate gel electrophoresis. Conditions are defined for quantitative measurements of the various polypeptide chains. The 40,000-Mr chain, which is labelled by the affinity reagent 4-(N-maleimido)phenyl [3H]trimethylammonium and therefore carries the acetylcholine receptor site, is the dominant polypeptide in the alkaline-treated membranes and the reconstituted acetylcholine receptor. Electron microscopy discloses that many of the alkaline-treated membranes no longer form closed vesicles and do not show the transverse asymmetry of the native membranes observed after tannic acid fixation. In the reconstituted receptor fractions, the receptor molecules reaggregate into discs and may be exposed on both faces of the discs. In the reconstituted vesicles, receptor rosettes are integrated to the lipid vesicles. With native membranes, the radioactive local anesthetic [3H]trimethisoquin binds to three classes of sites: non-specific, low-affinity and high-affinity. Carbamylcholine causes an increase in the number of high-affinity sites up to approximately 0.7 times the number of alpha-125I-bungarotoxin sites. This ratio, the three classes of binding sites, and their regulation by carbamylcholine are conserved through the reconstitution cycle.
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Aronstam RS, Eldefrawi AT, Eldefrawi ME. Similarities in the binding sites of the muscarinic receptor and the ionic channel of the nicotinic receptor. Biochem Pharmacol 1980; 29:1311-4. [PMID: 6249329 DOI: 10.1016/0006-2952(80)90292-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Eldefrawi ME, Aronstam RS, Bakry NM, Eldefrawi AT, Albuquerque EX. Activation, inactivation, and desensitization of acetylcholine receptor channel complex detected by binding of perhydrohistrionicotoxin. Proc Natl Acad Sci U S A 1980; 77:2309-13. [PMID: 6246539 PMCID: PMC348704 DOI: 10.1073/pnas.77.4.2309] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The effects of receptor activation were studied on the interaction of perhydrohistrionicotoxin (H(12)-HTX) with the ionic channel of the nicotinic acetylcholine (AcCho) receptor in membranes from the electric organ of Torpedo ocellata and with the endplate region of the soleus muscle of the rat. In Torpedo membranes, the initial rate (i.e., within 30 sec) of [(3)H]H(12)-HTX bindings to the ionic channel of the AcCho receptor was accelerated 10(2)- to 10(3)-fold in the presence of carbamoylcholine (Carb). H(12)-HTX also inhibited Carb-activated (22)Na(+) influx, over 95% inhibition at 10 muM H(12)-HTX. At this concentration H(12)-HTX did not inhibit [(3)H]AcCho binding to the AcCho-receptor sites. There was good correspondence between the degree of acceleration of [(3)H]H(12)-HTX binding and the stimulation of (22)Na(+) influx over a wide range of Carb concentrations (up to 100 muM). Preincubation of Torpedo membranes with Carb decreased the initial rate of [(3)H]H(12)-HTX binding, as well as the rate of (22)Na(+) influx, which may reflect desensitization of the AcCho-receptor. d-Tubocurarine inhibited the agonist-mediated acceleration of [(3)H]H(12)-HTX binding and (22)Na(+) influx. In the soleus muscle endplate, H(12)-HTX inhibited the transient depolarization induced by microiontophoretic application of AcCho; the more receptors activated and channels opened, the stronger was the inhibition by H(12)-HTX. These findings suggest that H(12)-HTX binds to closed and open ionic channels, with a preference for the latter conformation. It is also suggested that the conformational changes associated with activation or desensitization of the receptor can be monitored by studying binding of [(3)H]H(12)-HTX to the ionic channel sites as well as by the AcCho-receptor-regulated (22)Na(+) influx.
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Albuquerque EX, Tsai MC, Aronstam RS, Witkop B, Eldefrawi AT, Eldefrawi ME. Phencyclidine interactions with the ionic channel of the acetylcholine receptor and electrogenic membrane. Proc Natl Acad Sci U S A 1980; 77:1224-8. [PMID: 6928673 PMCID: PMC348458 DOI: 10.1073/pnas.77.2.1224] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The effects of phencyclidine (PCP) were studied on the electrogenic and chemosensitive properties of the neuromuscular junction of skeletal muscle as well as on the binding sites on the acetylcholine (AcCho) receptor and its ionic channel in the electric organ membranes of the electric ray. The directly elicited muscle twitch was markedly potentiated by prolonging the falling phase of the muscle action potential and blocking delayed rectification. The indirectly elicited muscle twitch was transiently potentiated and then blocked by PCP at concentrations below 60 muM. PCP blocked miniature endplate potentials and AcCho sensitivities at the junctional region of innervated muscle, blocked the extrajunctional sensitivity of the chronically denervated muscle, and significantly depressed the peak amplitude of the endplate current (EPC) in a voltage- and time-dependent manner. PCP also caused acceleration of the time course of EPC decay and shortening of the mean life-time of the open ionic channel. The effects of PCP were not due to inhibition of AcCho receptor sites because PCP did not protect against the quasi-irreversible inhibition of receptor sites by alpha-bungarotoxin, nor did it inhibit binding of [(3)H]AcCho or [(125)I-labeled alpha-bungarotoxin to the receptor sites. On the other hand, PCP blocked the binding of [(3)H]perhydrohistrionicotoxin to the sites of the ionic channel of the AcCho receptor. The data suggest that PCP reacts with the electrogenic K(+) channel and the ionic channel associated with the AcCho receptor in the open as well as the closed conformation.
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Matthews JC, Albuquerque EX, Eldefrawi ME. Influence of batrachotoxin, veratridine, grayanotoxin 1 and tetrodotoxin on uptake of Na-22 by rat brain membrane preparations. Life Sci 1979; 25:1651-8. [PMID: 513972 DOI: 10.1016/0024-3205(79)90406-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Lindstrom J, Merlie J, Yogeeswaran G. Biochemical properties of acteylcholine receptor subunits from Torpedo californica. Biochemistry 1979; 18:4465-70. [PMID: 497150 DOI: 10.1021/bi00588a003] [Citation(s) in RCA: 193] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Four polypeptide chains composing acetylcholine receptors from the electric organ of Torpedo californica were purified by preparative electrophoresis in sodium dodecyl sulfate. Their apparent mole ratio alpha/beta/gamma/delta is 2:1:1:1. These chains are not readily distinguished by amino acid or carbohydrate composition but are distinguished by apparent molecular weight and polypeptide maps. By peptide maps, no extensive homology is evident between these chains or between any of these chains and higher molecular weight chains found in receptor-enriched membrane fragments.
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Eldefrawi ME, Copio DS, Hudson CS, Rash J, Mansour NA, Eldefrawi AT, Albuguergue EX. Effects of antibodies to Torpedo acetylcholine receptor on the acetylcholine receptor--ionic channel complex of Torpedo electroplax and rabbit intercostal muscle. Exp Neurol 1979; 64:428-44. [PMID: 428517 DOI: 10.1016/0014-4886(79)90281-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Barkas T. Myasthenia gravis, the acetylcholine receptor and the immune response. INTERNATIONAL JOURNAL OF IMMUNOPHARMACOLOGY 1979; 1:263-71. [PMID: 162144 DOI: 10.1016/0192-0561(79)90002-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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