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Stoichiometry of δ subunit containing GABA(A) receptors
BACKGROUND AND PURPOSE: Although the stoichiometry of the major synaptic αβγ subunit-containing GABA(A) receptors has consensus support for 2α:2β:1γ, a clear view of the stoichiometry of extrasynaptic receptors containing δ subunits has remained elusive. Here we examine the subunit stoichiometry of...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John wiley & Sons Ltd
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3925037/ https://www.ncbi.nlm.nih.gov/pubmed/24206220 http://dx.doi.org/10.1111/bph.12514 |
Sumario: | BACKGROUND AND PURPOSE: Although the stoichiometry of the major synaptic αβγ subunit-containing GABA(A) receptors has consensus support for 2α:2β:1γ, a clear view of the stoichiometry of extrasynaptic receptors containing δ subunits has remained elusive. Here we examine the subunit stoichiometry of recombinant α4β3δ receptors using a reporter mutation and a functional electrophysiological approach. EXPERIMENTAL APPROACH: Using site-directed mutagenesis, we inserted a highly characterized 9′ serine to leucine mutation into the second transmembrane (M2) region of α4, β3 and δ subunits that increases receptor sensitivity to GABA. Whole-cell, GABA-activated currents were recorded from HEK-293 cells co-expressing different combinations of wild-type (WT) and/or mutant α4(L297S), β3(L284S) and δ(L288S) subunits. KEY RESULTS: Recombinant receptors containing one or more mutant subunits showed increased GABA sensitivity relative to WT receptors by approximately fourfold, independent of the subunit class (α, β or δ) carrying the mutation. GABA dose–response curves of cells co-expressing WT subunits with their respective L9′S mutants exhibited multiple components, with the number of discernible components enabling a subunit stoichiometry of 2α, 2β and 1δ to be deduced for α4β3δ receptors. Varying the cDNA transfection ratio by 10-fold had no significant effect on the number of incorporated δ subunits. CONCLUSIONS AND IMPLICATIONS: Subunit stoichiometry is an important determinant of GABA(A) receptor function and pharmacology, and δ subunit-containing receptors are important mediators of tonic inhibition in several brain regions. Here we demonstrate a preferred subunit stoichiometry for α4β3δ receptors of 2α, 2β and 1δ. |
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