A critical residue in the α1M2-M3 linker regulating mammalian GABAA receptor pore gating by diazepam

Elife. 2021 Feb 16:10:e64400. doi: 10.7554/eLife.64400.

Abstract

Benzodiazepines (BZDs) are a class of widely prescribed psychotropic drugs that modulate activity of GABAA receptors (GABAARs), neurotransmitter-gated ion channels critical for synaptic transmission. However, the physical basis of this modulation is poorly understood. We explore the role of an important gating domain, the α1M2-M3 linker, in linkage between the BZD site and pore gate. To probe energetics of this coupling without complication from bound agonist, we use a gain of function mutant (α1L9'Tβ2γ2L) directly activated by BZDs. We identify a specific residue whose mutation (α1V279A) more than doubles the energetic contribution of the BZD positive modulator diazepam (DZ) to pore opening and also enhances DZ potentiation of GABA-evoked currents in a wild-type background. In contrast, other linker mutations have little effect on DZ efficiency, but generally impair unliganded pore opening. Our observations reveal an important residue regulating BZD-pore linkage, thereby shedding new light on the molecular mechanism of these drugs.

Keywords: GABAA receptor; M2-M3 linker; allosteric modulator; benzodiazepine; diazepam; molecular biophysics; structural biology; xenopus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation
  • Animals
  • Diazepam / pharmacology*
  • Gain of Function Mutation
  • Ion Channel Gating / drug effects*
  • Oocytes
  • Patch-Clamp Techniques
  • Rats
  • Receptors, GABA-A / drug effects*
  • Receptors, GABA-A / genetics
  • Xenopus laevis

Substances

  • Receptors, GABA-A
  • Diazepam

Grants and funding

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.