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Updated: Jul 6, 2025

Methods for the Discovery of Novel Compounds Modulating a Gamma-Aminobutyric Acid Receptor Type A Neurotransmission
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Interaction modes of human orexin 2 receptor with selective and nonselective antagonists studied by NMR spectroscopy

Kayo Imamura1, Ken-Ichi Akagi2, Yohei Miyanoiri3

  • 1Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

Structure (London, England : 1993)
|January 9, 2024
PubMed

Insights

Researchers used NMR to study orexin receptor 2 (OX2R) structural changes when bound to antagonists. The study revealed distinct dynamic behaviors between selective and non-selective orexin receptor antagonists, crucial for drug development.

Area of Science:

  • Neuroscience
  • Structural Biology
  • Pharmacology

Background:

  • Orexin neuropeptides regulate critical physiological functions including sleep-wake cycles and feeding behavior.
  • Orexin receptors (OX1R and OX2R) are key targets, but subtle differences in their orthosteric sites impede subtype-selective antagonist development.
  • Understanding receptor dynamics is vital for designing effective orexin receptor modulators.

Purpose of the Study:

  • To investigate the structural plasticity of the orexin receptor 2 (OX2R) in complex with different antagonists using solution-state NMR.
  • To elucidate how subtype-selective and non-selective antagonists influence OX2R dynamics.
  • To provide insights into ligand recognition mechanisms for improved drug design.

Main Methods:

  • Solution-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed on 13CH3-ε-methionine labeled OX2R.
  • Structural changes were monitored upon complexation with subtype-selective (EMPA) and non-selective (suvorexant) antagonists.
  • Ligand exchange experiments were performed to identify residues sensitive to ligand binding.

Main Results:

  • Mutations within the orthosteric site of OX2R allosterically impacted the intracellular tip of transmembrane helix 6 (TM6).
  • Three methionine residues showed significant perturbation upon ligand binding, identified through exchange experiments.
  • The suvorexant-bound OX2R state exhibited greater structural plasticity compared to the EMPA-bound state, contrary to expectations based on crystal structures.

Conclusions:

  • The dynamic behavior of OX2R differs significantly depending on the antagonist bound, even for structurally similar compounds.
  • Solution-state NMR reveals dynamic features not apparent from static crystal structures, offering crucial insights into ligand recognition.
  • These findings are essential for the rational design of subtype-selective orexin receptor antagonists.
Keywords:
(13)C methyl methionine NMREMPAGPCROX2Rorexin 2 receptorstructural plasticitysuvorexant

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