Crystal Structures of Human Orexin 2 Receptor Bound to the Subtype-Selective Antagonist EMPA

Structure. 2018 Jan 2;26(1):7-19.e5. doi: 10.1016/j.str.2017.11.005. Epub 2017 Dec 7.

Abstract

Orexin peptides in the brain regulate physiological functions such as the sleep-wake cycle, and are thus drug targets for the treatment of insomnia. Using serial femtosecond crystallography and multi-crystal data collection with a synchrotron light source, we determined structures of human orexin 2 receptor in complex with the subtype-selective antagonist EMPA (N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulfonyl)-amino]-N-pyridin-3-ylmethyl-acetamide) at 2.30-Å and 1.96-Å resolution. In comparison with the non-subtype-selective antagonist suvorexant, EMPA contacted fewer residues through hydrogen bonds at the orthosteric site, explaining the faster dissociation rate. Comparisons among these OX2R structures in complex with selective antagonists and previously determined OX1R/OX2R structures bound to non-selective antagonists revealed that the residue at positions 2.61 and 3.33 were critical for the antagonist selectivity in OX2R. The importance of these residues for binding selectivity to OX2R was also revealed by molecular dynamics simulation. These results should facilitate the development of antagonists for orexin receptors.

Keywords: GPCR; X-ray crystallography; X-ray free-electron laser; orexin receptor; serial femtosecond crystallography; subtype selective ligand.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminopyridines / chemistry*
  • Aminopyridines / metabolism
  • Animals
  • Azepines / chemistry*
  • Azepines / metabolism
  • Baculoviridae / genetics
  • Baculoviridae / metabolism
  • Binding Sites
  • Cloning, Molecular
  • Crystallography / methods
  • Gene Expression
  • Genetic Vectors / chemistry
  • Genetic Vectors / metabolism
  • Humans
  • Hydrogen Bonding
  • Kinetics
  • Molecular Dynamics Simulation
  • Orexin Receptor Antagonists / chemistry*
  • Orexin Receptor Antagonists / metabolism
  • Orexin Receptors / chemistry*
  • Orexin Receptors / genetics
  • Orexin Receptors / metabolism
  • Orexins / chemistry*
  • Orexins / metabolism
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sf9 Cells
  • Spodoptera
  • Sulfonamides / chemistry*
  • Sulfonamides / metabolism
  • Synchrotrons
  • Thermodynamics
  • Triazoles / chemistry*
  • Triazoles / metabolism

Substances

  • Aminopyridines
  • Azepines
  • HCRTR1 protein, human
  • HCRTR2 protein, human
  • N-ethyl-2-((6-methoxy-pyridin-3-yl)-(toluene-2-sulphonyl)amino)-N-pyridin-3-ylmethyl-acetamide
  • Orexin Receptor Antagonists
  • Orexin Receptors
  • Orexins
  • Recombinant Proteins
  • Sulfonamides
  • Triazoles
  • suvorexant