A pharmacological characterization of GABA, THIP and DS2 at binary alpha 4 beta 3 and beta 3 delta receptors: GABA activates beta 3 delta receptors via the beta 3(+)delta (-) interface

作者：Lee H J; Absalom N L; Hanrahan J R; van Nieuwenhuijzen P; Ahring P K; Chebib M^*

来源：Brain Research, 2016, 1644: 222-230.

DOI：10.1016/j.brainres.2016.05.019

• GABA
• GABA(A) receptor
• delta Subunits
• THIP (Gaboxadol)
• DS2
• Mutations

There is growing evidence that GABA (gamma-aminobutyric acid) can activate GABA(A) receptors (GABA(A)Rs) in the absence of an a subunit. In this study, we compared the pharmacology of homomeric and binary alpha 4, beta 3 or delta subunits with ternary alpha 4 beta 3 delta to identify subunit interfaces that contribute to the pharmacology of GABA, THIP, and DS2, and the antagonists, Zn2+, gabazine and bicuculline. beta 3 delta receptors form functional GABA-gated channels when expressed in Xenopus oocytes with a pharmacology that differs to homomeric beta 3, binary alpha 4 beta 3 and ternary alpha 4 beta 3d receptors. GABA had similar potency at alpha 4 beta 3 and beta 3d receptors (25 mu M and 26 mu M, respectively) but differed at alpha 4 beta 3d receptors where GABA exhibited a biphasic concentration-response (EC50 (1)=12.6nM; EC50 (2)=6.3 mu M). THIP activated beta 3d receptors (EC50=456 mu M) but was a more potent activator of alpha 4 beta 3 (EC50=27 mu M) and alpha 4 beta 3d receptors (EC50 (1)=27.5nM; EC50 (2)=29.5 mu gamma), indicating that the alpha 4 subunit significantly contribute to its potency. The d-preferring modulator, DS2 had marginal or no effect at beta 3 delta and alpha 4 beta 3 receptors, indicating a role for both the alpha 4 and d subunits for its potency. Gabazine inhibited GABA-elicited currents at beta 3d receptors whereas bicuculline activated these receptors. Mutational analysis verified that GABA binds to the beta 3(+) delta(-) interface formed by the beta 3 and d subunits. In conclusion, evaluating agents against binary GABAARs such as beta 3 delta and alpha 4 beta 3 receptors enables identification of interfaces that may contribute to the pharmacology of the more complex ternary alpha 4 beta 3d receptors.

• 出版日期2016-8-1