The molecular determinants of neurosteroid binding in the GABA(A) receptor

Yusuke Sugasawa, John R. Bracamontes, Kathiresan Krishnan, Douglas F. Covey, David E. Reichert, Gustav Akk, Qiang,Chen, Pei Tang, Alex S. Evers, Wayland W.L. Cheng. Journal of Steroid Biochemistry and Molecular Biology, Volume 192, September 2019, Article number 105383 Read More

Abstract

Neurosteroids positively modulate GABA-A receptor (GABAAR) channel activity by binding to a transmembrane domain intersubunit site. Understanding the interactions in this site that determine neurosteroid binding and its effect is essential for the design of neurosteroid-based therapeutics. Using photo-affinity labeling and an ELIC-α1GABAAR chimera, we investigated the impact of mutations (Q242L, Q242W and W246L) within the intersubunit site on neurosteroid binding. These mutations, which abolish the thermal stabilizing effect of allopregnanolone on the chimera, reduce neither photolabeling within the intersubunit site nor competitive prevention of labeling by allopregnanolone. Instead, these mutations change the orientation of neurosteroid photolabeling. Molecular docking of allopregnanolone in WT and Q242W receptors confirms that the mutation favors re-orientation of allopregnanolone within the binding pocket. Collectively, the data indicate that mutations at Gln242 or Trp246 that eliminate neurosteroid effects do not eliminate neurosteroid binding within the intersubunit site, but significantly alter the preferred orientation of the neurosteroid within the site. The interactions formed by Gln242 and Trp246 within this pocket play a vital role in determining the orientation of the neurosteroid that may be necessary for its functional effect. © 2019 Elsevier Ltd

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Posted on June 26, 2019
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