Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors

GABAA receptors (GABAARs) play a crucial role in inhibition in the central nervous system. GABAARs containing the δ subunit mediate tonic inhibition, have distinctive pharmacological properties and are associated with disorders of the nervous system. To explore this receptor sub-class, we recently d...

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Autores principales:	Hong-Jin Shu, Xinguo Lu, John Bracamontes, Joe Henry Steinbach, Charles F. Zorumski, Steven Mennerick
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	GABA allosteric modulators inhibition antidepressant dentate gyrus neurosteroid ethanol Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
Acceso en línea:	https://doaj.org/article/2d6c80293f0b4718b46de2d30e9260f4
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spelling	oai:doaj.org-article:2d6c80293f0b4718b46de2d30e9260f42021-11-18T05:04:05ZPharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors1663-356310.3389/fnsyn.2021.763411https://doaj.org/article/2d6c80293f0b4718b46de2d30e9260f42021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fnsyn.2021.763411/fullhttps://doaj.org/toc/1663-3563GABAA receptors (GABAARs) play a crucial role in inhibition in the central nervous system. GABAARs containing the δ subunit mediate tonic inhibition, have distinctive pharmacological properties and are associated with disorders of the nervous system. To explore this receptor sub-class, we recently developed mice with δ-containing receptors rendered resistant to the common non-competitive antagonist picrotoxin (PTX). Resistance was achieved with a knock-in point mutation (T269Y; T6’Y) in the mouse genome. Here we characterize pharmacological and biophysical features of GABAARs containing the mutated subunit to contextualize results from the KI mice. Recombinant receptors containing δ T6’Y plus WT α4 and WT β2 subunits exhibited 3-fold lower EC50 values for GABA but not THIP. GABA EC50 values in native receptors containing the mutated subunit were in the low micromolar range, in contrast with some published results that have suggested nM sensitivity of recombinant receptors. Rectification properties of δ-containing GABAARs were similar to γ2-containing receptors. Receptors containing δ T6’Y had marginally weaker sensitivity to positive allosteric modulators, likely a secondary consequence of differing GABA sensitivity. Overexpression of δT6’Y in neurons resulted in robust PTX-insensitive IPSCs, suggesting that δ-containing receptors are readily recruited by synaptically released GABA. Overall, our results give context to the use of δ receptors with the T6’Y mutation to explore the roles of δ-containing receptors in inhibition.Hong-Jin ShuXinguo LuJohn BracamontesJoe Henry SteinbachJoe Henry SteinbachCharles F. ZorumskiCharles F. ZorumskiCharles F. ZorumskiSteven MennerickSteven MennerickSteven MennerickFrontiers Media S.A.articleGABA allosteric modulatorsinhibitionantidepressantdentate gyrusneurosteroidethanolNeurosciences. Biological psychiatry. NeuropsychiatryRC321-571ENFrontiers in Synaptic Neuroscience, Vol 13 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	GABA allosteric modulators inhibition antidepressant dentate gyrus neurosteroid ethanol Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
spellingShingle	GABA allosteric modulators inhibition antidepressant dentate gyrus neurosteroid ethanol Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571 Hong-Jin Shu Xinguo Lu John Bracamontes Joe Henry Steinbach Joe Henry Steinbach Charles F. Zorumski Charles F. Zorumski Charles F. Zorumski Steven Mennerick Steven Mennerick Steven Mennerick Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
description	GABAA receptors (GABAARs) play a crucial role in inhibition in the central nervous system. GABAARs containing the δ subunit mediate tonic inhibition, have distinctive pharmacological properties and are associated with disorders of the nervous system. To explore this receptor sub-class, we recently developed mice with δ-containing receptors rendered resistant to the common non-competitive antagonist picrotoxin (PTX). Resistance was achieved with a knock-in point mutation (T269Y; T6’Y) in the mouse genome. Here we characterize pharmacological and biophysical features of GABAARs containing the mutated subunit to contextualize results from the KI mice. Recombinant receptors containing δ T6’Y plus WT α4 and WT β2 subunits exhibited 3-fold lower EC50 values for GABA but not THIP. GABA EC50 values in native receptors containing the mutated subunit were in the low micromolar range, in contrast with some published results that have suggested nM sensitivity of recombinant receptors. Rectification properties of δ-containing GABAARs were similar to γ2-containing receptors. Receptors containing δ T6’Y had marginally weaker sensitivity to positive allosteric modulators, likely a secondary consequence of differing GABA sensitivity. Overexpression of δT6’Y in neurons resulted in robust PTX-insensitive IPSCs, suggesting that δ-containing receptors are readily recruited by synaptically released GABA. Overall, our results give context to the use of δ receptors with the T6’Y mutation to explore the roles of δ-containing receptors in inhibition.
format	article
author	Hong-Jin Shu Xinguo Lu John Bracamontes Joe Henry Steinbach Joe Henry Steinbach Charles F. Zorumski Charles F. Zorumski Charles F. Zorumski Steven Mennerick Steven Mennerick Steven Mennerick
author_facet	Hong-Jin Shu Xinguo Lu John Bracamontes Joe Henry Steinbach Joe Henry Steinbach Charles F. Zorumski Charles F. Zorumski Charles F. Zorumski Steven Mennerick Steven Mennerick Steven Mennerick
author_sort	Hong-Jin Shu
title	Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
title_short	Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
title_full	Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
title_fullStr	Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
title_full_unstemmed	Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors
title_sort	pharmacological and biophysical characteristics of picrotoxin-resistant, δsubunit-containing gabaa receptors
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/2d6c80293f0b4718b46de2d30e9260f4
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Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABAA Receptors

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