title: Pharmacology of putative selective hBRS-3 receptor agonists for human bombesin receptors (BnR): affinities, potencies and selectivity in multiple native and BnR transfected cells.
abstract: The orphan receptor, bombesin receptor subtype-3(BRS-3) is a G-protein-coupled receptor classified in the bombesin (Bn) receptor family because of its high homology (47-51%) with other members of this family [gastrin-releasing peptide receptor [GRPR] and neuromedin B receptor [NMBR]]. There is increasing interest in BRS-3, because primarily from receptor knockout studies, it seems important in energy metabolism, glucose control, insulin secretion, motility and tumor growth. Pharmacological tools to study the role of BRS-3 in physiology/pathophysiology are limited because the natural ligand is unknown and BRS-3 has low affinity for all naturally occurring Bn-related peptides. However, a few years ago a synthetic high-affinity agonist [dTyr(6),betaAla(11),Phe(13),Nle(14)]Bn-(6-14) was described but was nonselective for BRS-3 over other Bn receptors. Based on this peptide, in various studies a number of putative selective, high-potency hBRS-3 agonists were described, however the results on their selectivity are conflicting in a number of cases. The purpose of the present study was to thoroughly study the pharmacology of four of the most select/potent putative hBRS-3 agonists (#2-4, 16a). Each was studied in multiple well-characterized Bn receptor-transfected cells and native Bn receptor bearing cells, using binding studies, alterations in cellular signaling (PLC, PKD) and changes in cellular function(growth). Two peptides (#2, #3) had nM affinities/potencies for hBRS-3, peptide #4 had low affinity/potency, and peptide #16a very low (>3000 nM). Peptide#3 had the highest selectivity for hBRS-3 (100-fold), whereas #2, 4 had lower selectivity. Peptide #16a's selectivity could not be determined because of its low affinity/potencies for all hBn receptors. These results show that peptide #3 is the preferred hBRS-3 agonist for studies at present, although its selectivity of only 100-fold may limit its utility in some cases. This study underscores the importance of full pharmacological characterization of newly reported selective agonists.
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1804, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Sancho
authors.forename: Terry W
authors.initials: TW
authors.lastname: Moody
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Mantey
authors.forename: Alessia
authors.initials: A
authors.lastname: Di Florio
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Uehara
authors.forename: David H
authors.initials: DH
authors.lastname: Coy
authors.forename: Robert T
authors.initials: RT
authors.lastname: Jensen
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001839:Bombesin / Q000819:agonists* / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D015195:Drug Design; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008024:Ligands; D051379:Mice; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020033:Protein Isoforms / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D018004:Receptors, Bombesin / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000819:agonists / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D007295:Inositol Phosphates; D008024:Ligands; D009842:Oligopeptides; D010446:Peptide Fragments; D020033:Protein Isoforms; D018004:Receptors, Bombesin; D011994:Recombinant Proteins; C553591:bombesin (6-14), Tyr(6)-Apa(11)-4-Cl-Phe(13)-Nle(14)-; C107120:bombesin receptor subtype 3; C089212:protein kinase D; D011493:Protein Kinase C; D001839:Bombesin