N-terminal domains in mouse and human 5-hydroxytryptamine3A receptors confer partial agonist and antagonist properties to benzylidene analogs of anabaseine

Ran Zhang, Natalie A. White, Ferenc S. Soti, William R. Kem, Tina K. Machu

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Abstract

The present study tested the hypothesis that mouse and human 5-hydroxytryptamine3A (5-HT3A) receptors may be differentially modulated by benzylidene analogs of anabaseine (BA) and that these analogs may be useful in assessing residues involved in receptor gating. Mouse and human wild-type and mouse and human chimeric 5-HT3A receptors expressed in Xenopus oocytes were evaluated with the two-electrode voltage clamp technique. Our previous studies demonstrated that 3-(2,4-dimethoxybenzylidene)-anabaseine (DMXBA) is an antagonist at the mouse wild-type 5-HT3A receptor, but that its metabolites 3-(2-hydroxy, 4-methoxybenzylidene)-anabaseine (2-OHMBA), 3-(2-methoxy, 4-hydroxybenzylidene)- anabaseine (4-OHMBA), and 3-(2,4-dihydroxybenzylidene)-anabaseine (2,4-DiOHBA) are partial agonists (J Pharmacol Exp Ther, 299: 1112-1117, 2001). In the human wild-type (HWT) 5-HT3A receptor, none of the BA compounds possessed partial agonist activity. BA compounds antagonized 1.5 μM 5-HT-mediated (EC50) responses in the HWT 5-HT3A receptor with a rank order of potency (IC50 in μM) of 2-OHMBA (1.5 ± 0.1) > DMXBA (3.1 ± 0.2) > 4-OHMBA (7.4 ± 0.5) > 2,4-DiOHBA (12.8 ± 0.7). In mouse receptor chimeras containing N-terminal human receptor orthologs, 2-OHMBA inhibited 5-HT-mediated (EC50) currents with IC50 values of 2.0 ± 0.08 and 3.0 ± 0.13 μM, respectively. In human receptor chimeras containing N-terminal mouse receptor orthologs, 2-OHMBA displayed partial agonist activities with EC50 values of 1.3 ± 0.15 and 5.0 ± 0.4 μM; efficacies were 43 and 57%, respectively. Thus, amino acids present in the distal one-third of the N terminus of mouse and human 5-HT3A receptors are necessary and sufficient to confer partial agonist or antagonist properties of 2-OHMBA.

Original languageEnglish
Pages (from-to)1276-1284
Number of pages9
JournalJournal of Pharmacology and Experimental Therapeutics
Volume317
Issue number3
DOIs
StatePublished - 1 Jun 2006

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Inhibitory Concentration 50
Serotonin
anabaseine
Patch-Clamp Techniques
Xenopus
Oocytes
Electrodes
Amino Acids
3-(4-hydroxy-2-methoxybenzylidene)anabaseine
3-(2,4-dimethoxybenzylidene)anabaseine

Cite this

@article{1289d27422064a14bc1705b4844aca3f,
title = "N-terminal domains in mouse and human 5-hydroxytryptamine3A receptors confer partial agonist and antagonist properties to benzylidene analogs of anabaseine",
abstract = "The present study tested the hypothesis that mouse and human 5-hydroxytryptamine3A (5-HT3A) receptors may be differentially modulated by benzylidene analogs of anabaseine (BA) and that these analogs may be useful in assessing residues involved in receptor gating. Mouse and human wild-type and mouse and human chimeric 5-HT3A receptors expressed in Xenopus oocytes were evaluated with the two-electrode voltage clamp technique. Our previous studies demonstrated that 3-(2,4-dimethoxybenzylidene)-anabaseine (DMXBA) is an antagonist at the mouse wild-type 5-HT3A receptor, but that its metabolites 3-(2-hydroxy, 4-methoxybenzylidene)-anabaseine (2-OHMBA), 3-(2-methoxy, 4-hydroxybenzylidene)- anabaseine (4-OHMBA), and 3-(2,4-dihydroxybenzylidene)-anabaseine (2,4-DiOHBA) are partial agonists (J Pharmacol Exp Ther, 299: 1112-1117, 2001). In the human wild-type (HWT) 5-HT3A receptor, none of the BA compounds possessed partial agonist activity. BA compounds antagonized 1.5 μM 5-HT-mediated (EC50) responses in the HWT 5-HT3A receptor with a rank order of potency (IC50 in μM) of 2-OHMBA (1.5 ± 0.1) > DMXBA (3.1 ± 0.2) > 4-OHMBA (7.4 ± 0.5) > 2,4-DiOHBA (12.8 ± 0.7). In mouse receptor chimeras containing N-terminal human receptor orthologs, 2-OHMBA inhibited 5-HT-mediated (EC50) currents with IC50 values of 2.0 ± 0.08 and 3.0 ± 0.13 μM, respectively. In human receptor chimeras containing N-terminal mouse receptor orthologs, 2-OHMBA displayed partial agonist activities with EC50 values of 1.3 ± 0.15 and 5.0 ± 0.4 μM; efficacies were 43 and 57{\%}, respectively. Thus, amino acids present in the distal one-third of the N terminus of mouse and human 5-HT3A receptors are necessary and sufficient to confer partial agonist or antagonist properties of 2-OHMBA.",
author = "Ran Zhang and White, {Natalie A.} and Soti, {Ferenc S.} and Kem, {William R.} and Machu, {Tina K.}",
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N-terminal domains in mouse and human 5-hydroxytryptamine3A receptors confer partial agonist and antagonist properties to benzylidene analogs of anabaseine. / Zhang, Ran; White, Natalie A.; Soti, Ferenc S.; Kem, William R.; Machu, Tina K.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 317, No. 3, 01.06.2006, p. 1276-1284.

Research output: Contribution to journalArticle

TY - JOUR

T1 - N-terminal domains in mouse and human 5-hydroxytryptamine3A receptors confer partial agonist and antagonist properties to benzylidene analogs of anabaseine

AU - Zhang, Ran

AU - White, Natalie A.

AU - Soti, Ferenc S.

AU - Kem, William R.

AU - Machu, Tina K.

PY - 2006/6/1

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N2 - The present study tested the hypothesis that mouse and human 5-hydroxytryptamine3A (5-HT3A) receptors may be differentially modulated by benzylidene analogs of anabaseine (BA) and that these analogs may be useful in assessing residues involved in receptor gating. Mouse and human wild-type and mouse and human chimeric 5-HT3A receptors expressed in Xenopus oocytes were evaluated with the two-electrode voltage clamp technique. Our previous studies demonstrated that 3-(2,4-dimethoxybenzylidene)-anabaseine (DMXBA) is an antagonist at the mouse wild-type 5-HT3A receptor, but that its metabolites 3-(2-hydroxy, 4-methoxybenzylidene)-anabaseine (2-OHMBA), 3-(2-methoxy, 4-hydroxybenzylidene)- anabaseine (4-OHMBA), and 3-(2,4-dihydroxybenzylidene)-anabaseine (2,4-DiOHBA) are partial agonists (J Pharmacol Exp Ther, 299: 1112-1117, 2001). In the human wild-type (HWT) 5-HT3A receptor, none of the BA compounds possessed partial agonist activity. BA compounds antagonized 1.5 μM 5-HT-mediated (EC50) responses in the HWT 5-HT3A receptor with a rank order of potency (IC50 in μM) of 2-OHMBA (1.5 ± 0.1) > DMXBA (3.1 ± 0.2) > 4-OHMBA (7.4 ± 0.5) > 2,4-DiOHBA (12.8 ± 0.7). In mouse receptor chimeras containing N-terminal human receptor orthologs, 2-OHMBA inhibited 5-HT-mediated (EC50) currents with IC50 values of 2.0 ± 0.08 and 3.0 ± 0.13 μM, respectively. In human receptor chimeras containing N-terminal mouse receptor orthologs, 2-OHMBA displayed partial agonist activities with EC50 values of 1.3 ± 0.15 and 5.0 ± 0.4 μM; efficacies were 43 and 57%, respectively. Thus, amino acids present in the distal one-third of the N terminus of mouse and human 5-HT3A receptors are necessary and sufficient to confer partial agonist or antagonist properties of 2-OHMBA.

AB - The present study tested the hypothesis that mouse and human 5-hydroxytryptamine3A (5-HT3A) receptors may be differentially modulated by benzylidene analogs of anabaseine (BA) and that these analogs may be useful in assessing residues involved in receptor gating. Mouse and human wild-type and mouse and human chimeric 5-HT3A receptors expressed in Xenopus oocytes were evaluated with the two-electrode voltage clamp technique. Our previous studies demonstrated that 3-(2,4-dimethoxybenzylidene)-anabaseine (DMXBA) is an antagonist at the mouse wild-type 5-HT3A receptor, but that its metabolites 3-(2-hydroxy, 4-methoxybenzylidene)-anabaseine (2-OHMBA), 3-(2-methoxy, 4-hydroxybenzylidene)- anabaseine (4-OHMBA), and 3-(2,4-dihydroxybenzylidene)-anabaseine (2,4-DiOHBA) are partial agonists (J Pharmacol Exp Ther, 299: 1112-1117, 2001). In the human wild-type (HWT) 5-HT3A receptor, none of the BA compounds possessed partial agonist activity. BA compounds antagonized 1.5 μM 5-HT-mediated (EC50) responses in the HWT 5-HT3A receptor with a rank order of potency (IC50 in μM) of 2-OHMBA (1.5 ± 0.1) > DMXBA (3.1 ± 0.2) > 4-OHMBA (7.4 ± 0.5) > 2,4-DiOHBA (12.8 ± 0.7). In mouse receptor chimeras containing N-terminal human receptor orthologs, 2-OHMBA inhibited 5-HT-mediated (EC50) currents with IC50 values of 2.0 ± 0.08 and 3.0 ± 0.13 μM, respectively. In human receptor chimeras containing N-terminal mouse receptor orthologs, 2-OHMBA displayed partial agonist activities with EC50 values of 1.3 ± 0.15 and 5.0 ± 0.4 μM; efficacies were 43 and 57%, respectively. Thus, amino acids present in the distal one-third of the N terminus of mouse and human 5-HT3A receptors are necessary and sufficient to confer partial agonist or antagonist properties of 2-OHMBA.

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