L-3,3′,5-triiodothyronine and pregnenolone sulfate inhibit Torpedo nicotinic acetylcholine receptors

Steven X. Moffett, Eric A. Klein, Grace Brannigan, Joseph V. Martin

Research output: Contribution to journalArticle

Abstract

The nicotinic acetylcholine receptor (nAChR) is an excitatory pentameric ligand-gated ion channel (pLGIC), homologous to the inhibitory γ-aminobutyric acid (GABA) type A receptor targeted by pharmaceuticals and endogenous sedatives. Activation of the GABAA receptor by the neurosteroid allopregnanolone can be inhibited competitively by thyroid hormone (L- 3,3′,5-triiodothyronine, or T3), but modulation of nAChR by T3 or neurosteroids has not been investigated. Here we show that allopregnanolone inhibits the nAChR from Torpedo californica at micromolar concentrations, as do T3 and the anionic neurosteroid pregnenolone sulfate (PS). We test for the role of protein and ligand charge in mediated receptor inhibition by varying pH in a narrow range around physiological pH. We find that both T3 and PS become less potent with increasing pH, with remarkably similar trends in IC50 when T3 is neutral at pH < 7.3. After deprotonation of T3 (but no additional deprotonation of PS) at pH 7.3, T3 loses potency more slowly with increasing pH than PS. We interpret this result as indicating the negative charge is not required for inhibition but does increase activity. Finally, we show that both T3 and PS affect nAChR channel desensitization, which may implicate a binding site homologous to one that was recently indicated for accelerated desensitization of the GABAA receptor by PS.

Original languageEnglish (US)
Article numbere0223272
JournalPLoS ONE
Volume14
Issue number10
DOIs
StatePublished - Jan 1 2019

Fingerprint

pregnenolone
Torpedo
cholinergic receptors
Nicotinic Receptors
triiodothyronine
sulfates
GABA-A Receptors
Pregnanolone
Neurotransmitter Agents
Deprotonation
receptors
Ligand-Gated Ion Channels
Aminobutyrates
Torpedo californica
Triiodothyronine
Hypnotics and Sedatives
Thyroid Hormones
Inhibitory Concentration 50
triiodothyronine sulfate
pregnenolone sulfate

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences(all)
  • General
  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

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title = "L-3,3′,5-triiodothyronine and pregnenolone sulfate inhibit Torpedo nicotinic acetylcholine receptors",
abstract = "The nicotinic acetylcholine receptor (nAChR) is an excitatory pentameric ligand-gated ion channel (pLGIC), homologous to the inhibitory γ-aminobutyric acid (GABA) type A receptor targeted by pharmaceuticals and endogenous sedatives. Activation of the GABAA receptor by the neurosteroid allopregnanolone can be inhibited competitively by thyroid hormone (L- 3,3′,5-triiodothyronine, or T3), but modulation of nAChR by T3 or neurosteroids has not been investigated. Here we show that allopregnanolone inhibits the nAChR from Torpedo californica at micromolar concentrations, as do T3 and the anionic neurosteroid pregnenolone sulfate (PS). We test for the role of protein and ligand charge in mediated receptor inhibition by varying pH in a narrow range around physiological pH. We find that both T3 and PS become less potent with increasing pH, with remarkably similar trends in IC50 when T3 is neutral at pH < 7.3. After deprotonation of T3 (but no additional deprotonation of PS) at pH 7.3, T3 loses potency more slowly with increasing pH than PS. We interpret this result as indicating the negative charge is not required for inhibition but does increase activity. Finally, we show that both T3 and PS affect nAChR channel desensitization, which may implicate a binding site homologous to one that was recently indicated for accelerated desensitization of the GABAA receptor by PS.",
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L-3,3′,5-triiodothyronine and pregnenolone sulfate inhibit Torpedo nicotinic acetylcholine receptors. / Moffett, Steven X.; Klein, Eric A.; Brannigan, Grace; Martin, Joseph V.

In: PLoS ONE, Vol. 14, No. 10, e0223272, 01.01.2019.

Research output: Contribution to journalArticle

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