title: Identification of antagonists to the vasotocin receptor sub-type 4 (VT4R) involved in stress by molecular modelling and verification using anterior pituitary cells.
abstract: The vasotocin receptor family is homologous to the mammalian vasopressin G-protein coupled receptor (GPCR) family. The vasotocin receptor 2 (VT2R) and 4 (VT4R) have recently been shown to play important role(s) in the neuroendocrine regulation of stress in birds. A homology-based structural model of VT4R of the domestic chicken, Gallus gallus, was built using the sophisticated SYBYL-X suite. The structure of VT4R built with and without extra- and intracellular unstructured loops showed a seven-helix transmembrane domain, which is a characteristic feature of GPCRs. Several agonists and antagonists were screened by molecular docking to map their potential binding sites on the structure of VT4R. Interestingly, the presence of the N-terminal, intracellular and extracellular loops and C-terminal amino acid sequences emerging from the transmembrane domains during molecular docking appeared to influence the binding interface of the peptide agonists and peptide/non-peptide antagonists on the VT4R. The presence of unstructured loops, however, did not affect the relative binding affinity ranking of the peptide antagonists to VT4R. In general, the natural ligand, arginine vasotocin and the peptide/non-peptide antagonists were observed to be more deeply buried in the receptor. Results of in vitro inhibition experiments, using cultured anterior pituitary cells, showed excellent agreement with the binding affinity of the antagonists predicted by molecular docking. The results of this study provide valuable clues for the rational design of novel pharmaceutical compounds capable of blocking or attenuating the stress response.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Jayanthi
authors.affiliation: Department of Poultry Sciences, University of Arkansas, Fayettevillez, AR 72701, USA.
authors.forename: Seong Wook
authors.initials: SW
authors.lastname: Kang
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bingham
authors.affiliation: Department of Poultry Sciences, University of Arkansas, Fayettevillez, AR 72701, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Tessaro
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Thallapuranam K Suresh
authors.initials: TKS
authors.lastname: Kumar
authors.affiliation: Department of Poultry Sciences, University of Arkansas, Fayettevillez, AR 72701, USA.
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Kuenzel
mesh_terms: D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001665:Binding Sites; D001717:Birds; D002478:Cells, Cultured; D008024:Ligands; D008297:Male; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017483:Receptors, Vasopressin / Q000737:chemistry* / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D065092:Antidiuretic Hormone Receptor Antagonists; D008024:Ligands; D017483:Receptors, Vasopressin; C034862:vasotocin receptor