title: New structural insights into the apelin receptor: identification of key residues for apelin binding.
abstract: Apelin is the endogenous ligand of the orphan 7-transmembrane domain GPCR APJ, now named the apelin receptor (ApelinR). Apelin plays a prominent role in body fluid and cardiovascular homeostasis. To better understand the structural organization of the ApelinR, we built 3 homology 3-dimensional (3D) models of the human ApelinR using the validated cholecystokinin receptor-1 3D model or the X-ray structures of the β2-adrenergic and CXCR4 receptors as templates. Docking of the pyroglutamyl form of apelin 13 (pE13F) into these models revealed the conservation at the bottom of the binding site of a hydrophobic cavity in which the C-terminal Phe of pE13F was embedded. In contrast, at the top of the binding site, depending on the model, different interactions were visualized between acidic residues of the ApelinR and the basic residues of pE13F. Using site-directed mutagenesis, we showed that Asp 92, Glu 172, and Asp 282 of rat ApelinR are key residues in apelin binding by interacting with Lys 8, Arg 2, and Arg 4 of pE13F, respectively. These residues are only seen in the CXCR4-based ApelinR 3D model, further validating this model. These findings bring new insights into the structural organization of the ApelinR and the mode of apelin binding.
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Gerbier
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Leroux
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Couvineau
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Alvear-Perez
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Maigret
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France xavier.iturrioz@college-de-france.fr c.llorens-cortes@college-de-france.fr.
authors.forename: Catherine
authors.initials: C
authors.lastname: Llorens-Cortes
authors.affiliation: College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France xavier.iturrioz@college-de-france.fr c.llorens-cortes@college-de-france.fr.
authors.forename: Xavier
authors.initials: X
authors.lastname: Iturrioz
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000073861:Apelin; D000075244:Apelin Receptors; D001665:Binding Sites / Q000235:genetics; D017124:Conserved Sequence; D000242:Cyclic AMP / Q000096:biosynthesis; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein
chemical_list: C115436:APLN protein, human; C104575:APLNR protein, human; D000073861:Apelin; D000075244:Apelin Receptors; C491284:Aplnr protein, rat; D036341:Intercellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; D000242:Cyclic AMP
keywords: APJ; G protein–coupled receptor; homology models; molecular modeling; site-directed mutagenesis