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 language | English (US) |
|---|---|
| Article number | e0223272 |
| Journal | PLoS ONE |
| Volume | 14 |
| Issue number | 10 |
| DOIs | |
| State | Published - Jan 1 2019 |
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All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)
- General
- Biochemistry, Genetics and Molecular Biology(all)
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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 journal › Article
TY - JOUR
T1 - L-3,3′,5-triiodothyronine and pregnenolone sulfate inhibit Torpedo nicotinic acetylcholine receptors
AU - Moffett, Steven X.
AU - Klein, Eric A.
AU - Brannigan, Grace
AU - Martin, Joseph V.
PY - 2019/1/1
Y1 - 2019/1/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85072932456&partnerID=8YFLogxK
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U2 - https://doi.org/10.1371/journal.pone.0223272
DO - https://doi.org/10.1371/journal.pone.0223272
M3 - Article
C2 - 31584962
VL - 14
JO - PloS one
JF - PloS one
SN - 1932-6203
IS - 10
M1 - e0223272
ER -