Tryptophan replacement in the nociceptin/orphanin FQ receptor ligand Ac-RYYRWK-NH2

In the present study we describe the in vitro pharmacological characterization of the nociceptin/orphanin FQ (N/OFQ) receptor (NOP) ligand Ac-RYYRWK-NH2 and the synthesis and biological evaluation of 13 Trp5 substituted Ac-RYYRWK-NH2 analogs. Results indicate that Ac-RYYRWK-NH2 behaves as a highly potent and selective partial agonist at the NOP receptors and that the whole indole moiety of the Trp5 side chain is not required, being a phenyl-ethyl side chain already sufficient for maintaining high potency

Structure-activity relationship study on human urotensin II

The vasoactive cyclic undecapeptide urotensin-II (U-II) has been identified as an endogenous ligand for the G-protein coupled receptor now referred to as the UT receptor. The U-II/UT receptor system might be relevant for cardiovascular functions. A structure-activity study of human U-II investigating 31 peptides in the rat aorta bioassay is reported. Ala- and D-scan investigations indicated that the sequence Phe6-Trp7-Lys8-Tyr9 is essential for biological activity and that Lys8 and Tyr9 are particularly important. These two residues were substituted with a series of coded and non-coded amino acids. These studies demonstrated that the positive charge of the primary aliphatic amine at position 8 and its relative spatial orientation is crucial for both receptor occupation and activation, while the only chemical requirement at position 9 is the presence of an aromatic moiety. Moreover, this study led to the identification of UT receptor partial agonists (compounds 23 and 24) which can be used as chemical templates for further investigations aimed at the identification of selective antagonists

Tryptophan replacement in the nociceptin/orphanin FQ receptor ligand Ac-RYYRWK-NH2

reserved9noThis work was supported by funds from the University of Ferrara (60% grants to GC and SS), the Italian Ministry of the University (FIRB 2001 and Cofin 2004 grant to DR and SS), and the National Institute of Health (RO1HL71212 grant to DR and SS).In the present study we describe the in vitro pharmacological characterization of the nociceptin/orphanin FQ (N/OFQ) receptor (NOP) ligand Ac-RYYRWK-NH2 and the synthesis and biological evaluation of 13 Trp5 substituted Ac-RYYRWK-NH2 analogs. Results indicate that Ac-RYYRWK-NH2 behaves as a highly potent and selective partial agonist at the NOP receptors and that the whole indole moiety of the Trp5 side chain is not required, being a phenyl-ethyl side chain already sufficient for maintaining high potency.mixedCARRA' G; CALO' G; SPAGNOLO B; R. GUERRINI; ARDUIN M; MARZOLA E; TRAPELLA C; REGOLI D; SALVADORI SCarra', Giacomo; Calo', Girolamo; Spagnolo, Barbara; Guerrini, Remo; Arduin, Marika; Marzola, Erika; Trapella, Claudio; Regoli, Domenico; Salvadori, Sever

Synthesis and biological activity of nociceptin/orphanin FQ analogues substituted in position 7 or 11 with C alpha,alpha-dialkylated amino acids

Previous structure-activity and NMR studies on nociceptin/orphanin FQ (N/OFQ) demonstrated that Aib substitution of Ala7 and/or Ala11 increases the peptide potency through an alpha helix structure induction mechanism. On these bases we synthesised and evaluated pharmacologically in the mouse vas deferens assay a series of N/OFQ-NH2 analogues substituted in position 7 and 11 with Ca,a-disubstituted cyclic, linear and branched amino acids. None of the 20 novel N/OFQ analogues produced better results than [Aib7]N/OFQ-NH2. Thus, this substitution was combined with other chemical modifications known to modulate peptide potency and/or efficacy generating compound 21 [Nphe1Aib7Arg14Lys15]N/OFQ-NH2 (coded as UFP-111), compound 22 [(pF)Phe4Aib7Arg14Lys15]N/OFQ-NH2 (UFP-112) and compound 23 [Phe1W(CH2-NH)Gly2(pF)Phe4Aib7Arg14Lys15]N/OFQNH2 (UFP-113). These novel peptides behaved as highly potent NOP receptor ligands showing full (UFP-112) and partial (UFP-113) agonist and pure antagonist (UFP-111) activities in a series of in vitro functional assays performed on pharmacological preparations expressing native as well as recombinant NOP receptors

Synthesis and biological activity of nociceptin/orphanin FQ analogues substituted in position 7 or 11 with C alpha,alpha-dialkylated amino acids

Previous structure–activity and NMR studies on nociceptin/orphanin FQ (N/OFQ) demonstrated that Aib substitution of Ala7 and/or Ala11 increases the peptide potency through an alpha helix structure induction mechanism. On these bases we synthesised and evaluated pharmacologically in the mouse vas deferens assay a series of N/OFQ-NH2 analogues substituted in position 7 and 11 with Cα,α-disubstituted cyclic, linear and branched amino acids. None of the 20 novel N/OFQ analogues produced better results than [Aib7]N/OFQ-NH2. Thus, this substitution was combined with other chemical modifications known to modulate peptide potency and/or efficacy generating compound 21 [Nphe1Aib7Arg14Lys15]N/OFQ-NH2 (coded as UFP-111), compound 22 [(pF)Phe4Aib7Arg14Lys15]N/OFQ-NH2 (UFP-112) and compound 23 [Phe1Ψ(CH2–NH)Gly2(pF)Phe4Aib7Arg14Lys15]N/OFQ-NH2 (UFP-113). These novel peptides behaved as highly potent NOP receptor ligands showing full (UFP-112) and partial (UFP-113) agonist and pure antagonist (UFP-111) activities in a series of in vitro functional assays performed on pharmacological preparations expressing native as well as recombinant NOP receptors

N- and C-terminal modifications of nociceptin/orphanin FQ generate highly potent NOP receptor ligands

Previous structure-activity studies on nociceptin/orphanin FQ (N/OFQ) identified [Phe1\ube(CH2- NH)Gly2]N/OFQ(1-13)-NH2 and [Nphe1]N/OFQ(1-13)-NH2 as a N/OFQ peptide receptor (NOP) partial agonist and pure antagonist, respectively. The addition of fluorine to the Phe4 or the insertion of a further pair of basic amino acids Arg14-Lys15 generate potent agonists. On the basis of these findings, we combined in the N/OFQ-NH2 template the chemical modifications Arg14-Lys15 and (pF)Phe4 that increase the agonist potency with those conferring partial agonist (Phe1\ube(CH2NH)Gly2) or pure antagonist (Nphe1) properties. Twelve peptides were synthesized and pharmacologically evaluated in Chinese hamster ovary cells expressing the human recombinant NOP and in electrically stimulated mouse vas deferens and guinea pig ileum assays. All peptides behaved as NOP ligands; the chemical modifications Arg14-Lys15 and (pF)- Phe4 increased ligand affinity/potency. Peptides with the normal Phe1-Gly2 peptide bond behaved as full agonists, and those with the Phe1\ube(CH2NH)Gly2 modification behaved as partial agonists, while those with the Nphe1 modification behaved as partial agonists or pure antagonists depending on the presence or absence of the (pF)Phe4 modification, respectively. The full agonist [(pF)Phe4,Arg14,Lys15]N/OFQ-NH2, the partial agonist [Phe1\ube(CH2NH)- Gly2,(pF)Phe4,Arg14,Lys15]N/OFQ-NH2, and the pure antagonist [Nphe1,Arg14,Lys15]N/OFQ-NH2 represent the most potent peptide ligands for NOP

Structure-activity studies on neuropeptide S - Identification of the amino acid residues crucial for receptor activation

Neuropeptide S (NPS) has been recently recognized as the endogenous ligand for the previous orphan G-protein-coupled receptor GPR154, now referred to as the NPS receptor (NPSR). The NPS-NPSR receptor system regulates important biological functions such as sleeping/wakening, locomotion, anxiety, and food intake. To collect information on the mechanisms of interaction between NPS and its receptor, a classical structure-activity relationship study was performed. Human (h) NPS derivatives obtained by Ala and D-scan and N- and C-terminal truncation were assessed for their ability to stimulate calcium release in HEK293 cells expressing the human recombinant NPSR. The results of this study indicate that (i) the effect of hNPS is mimicked by the fragment hNPS- (1-10); (ii) Phe2, Arg3, and Asn4 are crucial for biological activity; (iii) the sequence Thr8-Gly9-Met10 is important for receptor activation, although with non-stringent chemical requirements; and (iv) the sequence Val6-Gly7 acts as a hinge region between the two above-mentioned domains. However, the stimulatory effect of hNPS given intracerebroventricularly on mouse locomotor activity was not fully mimicked by hNPS-(1-10), suggesting that the C-terminal region of the peptide maintains importance for in vivo activity. In conclusion, this study identified the amino acid residues of this peptide most important for receptor activation