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Evidence for coassembly of mutant GABA C ρ1 with GABA A γ2S, glycine α1 and glycine α2 receptor subunits in vitro
Author(s) -
Pan ZhuoHua,
Zhang Dongxian,
Zhang Xishan,
Lipton Stuart A.
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00198.x
Subject(s) - homomeric , xenopus , glycine , glycine receptor , protein subunit , receptor , gabaa receptor , strychnine , chemistry , cys loop receptors , gamma aminobutyric acid , biochemistry , microbiology and biotechnology , biophysics , biology , amino acid , acetylcholine receptor , nicotinic acetylcholine receptor , gene
Functional coassembly of γ‐aminobutyric acid (GABA) C ρ1 subunits with GABA A (α1, β2, and γ2S) or glycine (α1, α2, and β) subunits was examined using two‐electrode voltage‐clamp recordings in the Xenopus laevis oocyte expression system. To facilitate this study, we took advantage of the unique gating and pharmacological properties of two mutant ρ1 subunits, ρ1(T314A) and ρ1(T314A/L317A). When the ρ1(T314A) subunit was coexpressed with GABA γ2S, glycine α1 or glycine α2 subunits, GABA response properties were different from those of homomeric ρ1(T314A) receptors. Additionally, the sensitivity of heteromeric ρ1(T314A) and γ2S receptors to picrotoxinin (PTX) blockade of GABA‐evoked responses was altered compared to that of homomeric ρ1(T314A) receptors. Changes in GABA response properties and picrotoxinin sensitivity were also observed when ρ1(T314A) subunits were coexpressed with wild‐type ρ1 subunits. When ρ1(T314A/L317A) subunits were coexpressed with GABA γ2S, glycine α1 or glycine α2 subunits, suppression by GABA of spontaneously active current was reduced compared to that of homomeric ρ1(T314A/L317A) receptors. Recovery of the spontaneous current from inhibition by GABA for GABA ρ1(T314A/L317A)/γ2S heteromeric receptors displayed an additional component. Coinjection of wild‐type ρ1 with γ2S cRNAs at a ratio of 1 : 1 resulted in a > 10‐fold reduction in GABA‐evoked current. Furthermore, coexpression of wild‐type ρ1 and γ2S subunits was found to shift the GABA dose–response curve. Our results provide functional evidence that the GABA C ρ1 subunit can coassemble with the GABA A γ2S subunit, and, at least in its mutated form, ρ1 can also form heteromeric receptors with glycine α1 or α2 subunits in vitro.