title: In vitro binding and functional studies of Ac-RYYRIK-ol and its derivatives, novel partial agonists of the nociceptin/orphanin F/Q receptor.
abstract: Following the discovery of nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) and its endogenous ligand, an extensive search has started to find selective agonists and antagonists targeting this novel receptor-ligand system due to their therapeutic potentials. By the help of the combinatorial chemistry a series of hexapeptides with a general formula of Ac-RYY-R/K-W/I-R/K-NH(2) having high NOP receptor affinity and selectivity were identified. On the basis of this information we developed a number of novel compounds. The detailed structure-activity studies on the partial agonist Ac-RYYRIK-NH(2) are reported in this communication. Besides the modifications on N- and C-terminal, Arg-Cit exchange was performed on the template structure. The novel hexapeptides were analyzed in radioligand binding, functional biochemical [(35)S]GTPgammaS binding assays by using membranes from rat brains and Chinese hamster ovary cells expressing human NOP receptor. The agonist/antagonist properties were also tested on in the mouse vas deferens bioassay. C-terminal modification yielded a high affinity, selective and potent NOP ligand (Ac-RYYRIK-ol) with a partial agonist property. Several analogs of this compound were synthesized. The presence of the positively charged arginine residue at the first position turned out to be crucial for the biological activity of the hexapeptide. The N-terminal modifications with various acyl groups (ClAc, pivaloyl, formyl, benzoyl, mesyl) decreased the affinity of the ligand towards the receptor and the intrinsic activity for stimulating the G-protein activation was also decreased. The structure-activity studies on the hexapeptide derivatives provided some basic information on the structural requirements for receptor binding and activation.
authors.affiliation: Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary. ozge@nucleus.szbk.u-szeged.hu
authors.forename: Ozge
authors.initials: O
authors.lastname: Gunduz
authors.forename: Ferenc
authors.initials: F
authors.lastname: Sipos
authors.forename: Barbara
authors.initials: B
authors.lastname: Spagnolo
authors.forename: László
authors.initials: L
authors.lastname: Kocsis
authors.forename: Anna
authors.initials: A
authors.lastname: Magyar
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Orosz
authors.forename: Anna
authors.initials: A
authors.lastname: Borsodi
authors.forename: Girolamo
authors.initials: G
authors.lastname: Calò
authors.forename: Sándor
authors.initials: S
authors.lastname: Benyhe
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics*; D018847:Opioid Peptides / Q000819:agonists* / Q000494:pharmacology / Q000502:physiology; D010759:Phosphorus Isotopes / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011957:Receptors, Opioid / Q000502:physiology*; D014649:Vas Deferens / Q000187:drug effects / Q000294:innervation / Q000528:radiation effects; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009842:Oligopeptides; D018847:Opioid Peptides; D010759:Phosphorus Isotopes; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C479838:(Nphe(1),Arg(14),Lys(15))N-OFQ NH(2); C512381:Ac-RYYRIK-ol