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Jakubík J, Zimčík P, Randáková A, Fuksová K, El-Fakahany EE, Doležal V. Molecular mechanisms of methoctramine binding and selectivity at muscarinic acetylcholine receptors. Mol Pharmacol 2014; 86:180-92. [PMID: 24870405 DOI: 10.1124/mol.114.093310] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Methoctramine (N,N'-bis[6-[[(2-methoxyphenyl)-methyl]hexyl]-1,8-octane] diamine) is an M(2)-selective competitive antagonist of muscarinic acetylcholine receptors and exhibits allosteric properties at high concentrations. To reveal the molecular mechanisms of methoctramine binding and selectivity we took advantage of reciprocal mutations of the M(2) and M(3) receptors in the second and third extracellular loops that are involved in the binding of allosteric ligands. To this end we performed measurements of kinetics of the radiolabeled antagonists N-methylscopolamine (NMS) in the presence of methoctramine and its precursors, fluorescence energy transfer between green fluorescent protein-fused receptors and an Alexa-555-conjugated precursor of methoctramine, and simulation of molecular dynamics of methoctramine association with the receptor. We confirm the hypothesis that methoctramine high-affinity binding to the M(2) receptors involves simultaneous interaction with both the orthosteric binding site and the allosteric binding site located between the second and third extracellular loops. Methoctramine can bind solely with low affinity to the allosteric binding site on the extracellular domain of NMS-occupied M(2) receptors by interacting primarily with glutamate 175 in the second extracellular loop. In this mode, methoctramine physically prevents dissociation of NMS from the orthosteric binding site. Our results also demonstrate that lysine 523 in the third extracellular loop of the M(3) receptors forms a hydrogen bond with glutamate 219 of the second extracellular loop that hinders methoctramine binding to the allosteric site at this receptor subtype. Impaired interaction with the allosteric binding site manifests as low-affinity binding of methoctramine at the M(3) receptor.
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Affiliation(s)
- Jan Jakubík
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
| | - Pavel Zimčík
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
| | - Alena Randáková
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
| | - Květoslava Fuksová
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
| | - Esam E El-Fakahany
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
| | - Vladimír Doležal
- Institute of Physiology, v.v.i. (J.J., P.Z., A.R., V.D.) and Institute of Experimental Botany, v.v.i. (K.F.), Academy of Sciences of the Czech Republic, Prague, Czech Republic; and Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, Minnesota (E.E.E.)
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Redka DS, Pisterzi LF, Wells JW. Binding of orthosteric ligands to the allosteric site of the M(2) muscarinic cholinergic receptor. Mol Pharmacol 2008; 74:834-43. [PMID: 18552124 DOI: 10.1124/mol.108.048074] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The M(2) muscarinic receptor has two topographically distinct sites: the orthosteric site and an allosteric site recognized by compounds such as gallamine. It also can exhibit cooperative effects in the binding of orthosteric ligands, presumably to the orthosteric sites within an oligomer. Such effects would be difficult to interpret, however, if those ligands also bound to the allosteric site. Monomers of the hemagglutinin (HA)- and FLAG-tagged human M(2) receptor therefore have been purified from coinfected Sf9 cells and examined for any effect of the antagonist N-methyl scopolamine or the agonist oxotremorine-M on the rate at which N-[(3)H]methyl scopolamine dissociates from the orthosteric site (k(obsd)). The predominantly monomeric status was confirmed by coimmunoprecipitation and by cross-linking with bis(sulfosuccinimidyl)suberate. Both N-methyl scopolamine and oxotremorine-M acted in a cooperative manner to decrease k(obsd) by 4.5- and 9.1-fold, respectively; the corresponding estimates of affinity (log K(L)) are -2.55 +/- 0.13 and -2.29 +/- 0.14. Gallamine and the allosteric ligand obidoxime decreased k(obsd) by more than 100-fold (log K(L) = -4.12 +/- 0.04) and by only 1.1-fold (log K(L) = -1.73 +/- 0.91), respectively. Obidoxime reversed the effect of N-methyl scopolamine, oxotremorine-M, and gallamine in a manner that could be described by a model in which all four ligands compete for a common allosteric site. Ligands generally assumed to be exclusively orthosteric therefore can act at the allosteric site of the M(2) receptor, albeit at comparatively high concentrations.
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Affiliation(s)
- Dar'ya S Redka
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario, Canada
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Colabufo NA, Pagliarulo V, Berardi F, Contino M, Perrone R, Niso M, Albo G, de Rienzo G, Pagliarulo A. Human epididymal and prostatic tracts of vas deferens: Different contraction response to noradrenaline stimulation in isolated organ bath assay. Eur J Pharmacol 2007; 577:150-5. [PMID: 17900563 DOI: 10.1016/j.ejphar.2007.08.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 08/11/2007] [Accepted: 08/28/2007] [Indexed: 11/17/2022]
Abstract
In the present study epididymal and prostatic portions of human vas deferens were separately isolated and stimulated with exogenous noradrenaline to study their contractile properties. The results displayed that the epididymal tract produced a phasic-tonic response, while the prostatic strip produced only a phasic response suggesting a different functional role of each vas deferens segment. Moreover, it has been verified if alpha(1)-adrenoceptor antagonists doxazosin, alphuzosin and terazosin could differently block the noradrenaline response in each segment. Doxazosin, the most potent antagonist, displayed similar potency in epididymal and prostatic tract (pA(2)=8.51 and 8.42, respectively). Analogously, alphuzosin, although less potent than doxazosin, displayed in the same tracts a superimposed potency (pA(2)=7.25 and 7.30, respectively). In contrast with doxazosin and alphuzosin, terazosin displayed higher potency in blocking the contractile response in prostatic tract (pA(2)=7.67) than in epididymal segment (pA(2)=6.43). These results showed that alpha(1)-adrenoceptor antagonists doxazosin and alphuzosin, although with a different potency, did not discriminate between epididymal and prostatic segment while terazosin showed high potency in prostatic tract and only a moderate activity in epididymal section. Moreover, the biological model employed in our experiments could be a valid screening method to test the potential interferences of drugs indicated for bladder outlet obstruction with the peristaltic activity or the global tone of the human vas deferens.
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Affiliation(s)
- Nicola A Colabufo
- Dipartimento Farmacochimico, Facoltá di Farmacia, Università degli Studi di Bari, via Orabona 4, 70125 Bari, Italy.
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Lanzafame A, Christopoulos A, Mitchelson F. The allosteric interaction of otenzepad (AF-DX 116) at muscarinic M2 receptors in guinea pig atria. Eur J Pharmacol 2001; 416:235-44. [PMID: 11290374 DOI: 10.1016/s0014-2999(01)00827-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The effects of the muscarinic receptor antagonist, otenzepad, in combination with the competitive antagonists N-methylscopolamine, dexetimide and atropine, or the allosteric modulators, C(7)/3'-phth, gallamine and alcuronium, were measured in the guinea pig electrically driven left atrium using the agonists, carbachol or acetylcholine. Otenzepad, in combination with C(7)/3'-phth or gallamine, gave concentration-ratios close to additive and in agreement with theoretical model predictions for combination of two allosteric modulators acting at a common site. However, when otenzepad was combined with alcuronium, dexetimide or N-methylscopolamine, supra-additive effects were observed. For either competitive antagonist in combination with otenzepad, the degree of supra-additivity was more evident after 2-h equilibration than after 40 min. When otenzepad was combined with atropine, no supra-additivity was observed with carbachol as the agonist, but was evident with acetylcholine. Otenzepad was also unable to fully inhibit [3H]N-methylscopolamine binding when the radioligand was employed at a concentration of approximately 100 x K(D). It is concluded that the action of otenzepad involves an allosteric site and a number of possibilities are discussed for its location.
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Affiliation(s)
- A Lanzafame
- Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy (Monash University), 381 Royal Parade, Victoria 3052, Parkville, Australia
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Seya K, Miki I, Murata K, Junke H, Motomura S, Araki T, Itoyama Y, Oshima Y. Pharmacological properties of pteleprenine, a quinoline alkaloid extracted from Orixa japonica, on guinea-pig ileum and canine left atrium. J Pharm Pharmacol 1998; 50:803-7. [PMID: 9720631 DOI: 10.1111/j.2042-7158.1998.tb07143.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have investigated the pharmacological properties of pteleprenine, a quinoline alkaloid, on contractile responses of the guinea-pig ileum and on inotropic responses of the canine left atrium. Although pteleprenine (0.1-1 microM) had no effect on the contraction of the ileum induced by acetylcholine at 10 microM it significantly inhibited acetylcholine-induced contraction of the ileum. Pteleprenine (0.1-10 microM) reduced nicotine induced-contraction of the ileum in a concentration-dependent manner yet had no maximum relaxant effect even at a concentration of 10 microM. From Schild analysis the pA2 of pteleprenine on the guinea-pig ileum was found to be 6.6. The contraction of the ileum induced by 10 microM 1,1-dimethyl-4-phenylpiperazinium, a specific agonist of nicotinic acetylcholine receptors, was concentration-dependently suppressed by 10 nM-10 microM pteleprenine. In contrast, 0.1-10 microM pteleprenine did not antagonize the acetylcholine- and nicotine-induced negative inotropic contractile responses of the canine left atrium. These results show that pteleprenine has inhibitory action against nicotinic acetylcholine receptors in the guinea-pig ileum but not in the canine left atrium. Our findings also suggest that pteleprenine might be a novel lead compound as a nicotinic receptor antagonist.
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Affiliation(s)
- K Seya
- Department of Pharmacology, Hirosaki University School of Medicine, Japan
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Munns M, Pennefather JN. Pharmacological characterization of muscarinic receptors in the uterus of oestrogen-primed and pregnant rats. Br J Pharmacol 1998; 123:1639-44. [PMID: 9605571 PMCID: PMC1565341 DOI: 10.1038/sj.bjp.0701794] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. Radioligand binding and contractility studies were undertaken to determine the subtype/s of muscarinic receptors present in uteri of oestrogen-treated and late pregnant rats. 2. Competition binding studies with uterine membrane preparations and [3H]-QNB (quinuclidinyl benzilate) provided negative log dissociation constants (pKi) for each antagonist as follows; oestrogen-treated - atropine (7.98) > or = himbacine (7.83) > methoctramine (7.52) > or = hexahydrosiladiphenidol (HHSiD; 7.32) > or = 5,11-dihydro- 11-[[[2-[2 - [(dipropylamino)methyl] - 1 piperidinyl]ethyl]amino] - carbonyl] - 6H-pyrido-[2,3-b][1,4]- benzodiazepin-6-one (AF-DX 384; 7.10)> 11 -[[2- [(diethylamino)methyl]-1-piperidinyl]-acetyl]5,11-dihydro-6H-pyridol+ ++]2,3,-b][1,4]benzodiazepin-6-one (AF-DX 116, 6.77)>pirenzepine (6.17); late pregnant atropine (8.05)> or =methoctramine (7.95)> or =himbacine (7.71)> or =HHSiD (7.52)> or =AF-DX 384 (7.34)>AF-DX 116 (6.72)>pirenzepine (6.18). 3. The potency of carbachol in causing uterine contraction was similar in preparations from pregnant and non-pregnant animals (pD2=5.57 and 5.46, respectively). Each muscarinic antagonist caused parallel, rightward shifts of carbachol concentration-response curves. The pA2 estimates were: oestrogen-treated - atropine (9.42)> himbacine (8.73) HHSiD (8.68) methoctramine (8.49)> or =AF-DX 384 (7.91)> or =AF-DX 116 (7.36)> or =pirenzepine (7.26); late pregnant atropine (9.48)>himbacine (8.37)> or = HHSiD (8.22) > or =methoctramine (8.01) > or =AF-DX 116 (7.73)> or = AF-DX 384 (7.44)> or = pirenzepine (6.92). 4. The relative pKi estimates for antagonists obtained in membrane preparations from oestrogen-treated rats suggest the presence of muscarinic M2 subtypes. In functional studies pA2 values indicated the additional presence of muscarinic M3 receptor or, possibly an atypical receptor subtype. The similarity between pKi and pA2 estimates obtained in uteri from oestrogen-treated and pregnant animals, respectively, indicates that pregnancy does not affect myometrial muscarinic receptors in the rat.
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Affiliation(s)
- M Munns
- Department of Pharmacology, Monash University, Clayton, Victoria, Australia
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