title: Toward an understanding of agonist binding to human Orexin-1 and Orexin-2 receptors with G-protein-coupled receptor modeling and site-directed mutagenesis.
abstract: The class A G-protein-coupled receptors (GPCRs) Orexin-1 (OX1) and Orexin-2 (OX2) are located predominantly in the brain and are linked to a range of different physiological functions, including the control of feeding, energy metabolism, modulation of neuro-endocrine function, and regulation of the sleep-wake cycle. The natural agonists for OX1 and OX2 are two neuropeptides, Orexin-A and Orexin-B, which have activity at both receptors. Site-directed mutagenesis (SDM) has been reported on both the receptors and the peptides and has provided important insight into key features responsible for agonist activity. However, the structural interpretation of how these data are linked together is still lacking. In this work, we produced and used SDM data, homology modeling followed by MD simulation, and ensemble-flexible docking to generate binding poses of the Orexin peptides in the OX receptors to rationalize the SDM data. We also developed a protein pairwise similarity comparing method (ProS) and a GPCR-likeness assessment score (GLAS) to explore the structural data generated within a molecular dynamics simulation and to help distinguish between different GPCR substates. The results demonstrate how these newly developed methods of structural assessment for GPCRs can be used to provide a working model of neuropeptide-Orexin receptor interaction.
authors.affiliation: Evotec (U.K.) Ltd. , 114 Innovation Drive, Milton Park, Abingdon, Oxfordshire OX14 4RZ, U.K.
authors.forename: Alexander
authors.initials: A
authors.lastname: Heifetz
authors.forename: Oliver
authors.initials: O
authors.lastname: Barker
authors.forename: G Benjamin
authors.initials: GB
authors.lastname: Morris
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Law
authors.forename: Mark
authors.initials: M
authors.lastname: Slack
authors.forename: Philip C
authors.initials: PC
authors.lastname: Biggin
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008956:Models, Chemical; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D009479:Neuropeptides / Q000378:metabolism*; D064446:Orexin Receptors / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D000068797:Orexins; D011487:Protein Conformation; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: C000596229:HCRT protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled