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Structural insights into opposing actions of neurosteroids on GABAA receptors

Journal Article · · Nature Communications
 [1];  [2];  [3];  [2];  [2];  [3];  [4];  [5]
  1. UT Southwestern Medical Center, Dallas, TX (United States)
  2. Stockholm University, Solna (Sweden)
  3. University of California San Diego, La Jolla, CA (United States)
  4. Stockholm University, Solna (Sweden); KTH Royal Institute of Technology, Solna (Sweden)
  5. UT Southwestern Medical Center, Dallas, TX (United States); University of California San Diego, La Jolla, CA (United States)

γ-Aminobutyric acid type A (GABAA) receptors mediate fast inhibitory signaling in the brain and are targets of numerous drugs and endogenous neurosteroids. A subset of neurosteroids are GABAA receptor positive allosteric modulators; one of these, allopregnanolone, is the only drug approved specifically for treating postpartum depression. There is a consensus emerging from structural, physiological and photolabeling studies as to where positive modulators bind, but how they potentiate GABA activation remains unclear. Other neurosteroids are negative modulators of GABAA receptors, but their binding sites remain debated. Here we present structures of a synaptic GABAA receptor bound to allopregnanolone and two inhibitory sulfated neurosteroids. Allopregnanolone binds at the receptor-bilayer interface, in the consensus potentiator site. In contrast, inhibitory neurosteroids bind in the pore. MD simulations and electrophysiology support a mechanism by which allopregnanolone potentiates channel activity and suggest the dominant mechanism for sulfated neurosteroid inhibition is through pore block.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); CPRIT Core Facility Support Award; National Institutes of Health (NIH); USDOE Office of Science (SC), Biological and Environmental Research (BER); Stockholm University; Swedish Research Council; Welch Foundation
Grant/Contract Number:
AC05-76RL01830
OSTI ID:
2424192
Journal Information:
Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 14; ISSN 2041-1723
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English

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