title: Structure activity studies of nociceptin/orphanin FQ(1-13)-NH2 derivatives modified in position 5.
abstract: Nociceptin/orphanin FQ (N/OFQ) is a heptadecapeptide acting as the endogenous ligand of the N/OFQ peptide receptor (NOP). N/OFQ(1-13)-NH2 is the shortest N/OFQ sequence maintaining the same potency and efficacy as the natural peptide. Thus N/OFQ(1-13)-NH2 was used as chemical template for investigating the structure activity relationship of threonine in position 5. 28 [X(5)]N/OFQ(1-13)-NH2 derivatives, in which Thr was substituted with natural and unnatural residues, were synthesized and characterized pharmacologically for their effects at the human NOP receptor. Two different functional assays were used: agonist stimulated [(35)S]GTPγS binding in cell membranes and calcium mobilization in whole cells co-expressing chimeric G proteins. All [X(5)]N/OFQ(1-13)-NH2 derivatives behaved as full NOP agonists showing large differences in their potency. There was an excellent correlation between the results obtained in the two assays. The results of this study suggest that: position 5 does not play a pivotal role in receptor activation; the secondary alcoholic function of Thr is not important for receptor binding; side chain size, lipo/hydrophilic balance as well as hydrogen bond capability are also not crucial for receptor binding; an aliphatic amino function positively charged with at least 3 carbon atom distance from the peptide backbone has a huge disrupting effect on receptor binding. In conclusion this study demonstrates that a simple ethyl side chain as in compound 23 is sufficient in N/OFQ position 5 for maintaining bioactivity.
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, 44121 Ferrara, Italy; Laboratorio per le tecnologie delle terapie avanzate (LTTA), University of Ferrara, 44121 Ferrara, Italy. Electronic address: r.guerrini@unife.it.
authors.forename: Remo
authors.initials: R
authors.lastname: Guerrini
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, 44121 Ferrara, Italy; Laboratorio per le tecnologie delle terapie avanzate (LTTA), University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Marzola
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, 44121 Ferrara, Italy; Laboratorio per le tecnologie delle terapie avanzate (LTTA), University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Trapella
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Pacifico
authors.affiliation: Department of Medical Science, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Maria Camilla
authors.initials: MC
authors.lastname: Cerlesi
authors.affiliation: Department of Medical Science, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Malfacini
authors.affiliation: Department of Medical Science, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Ferrari
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Division of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
authors.forename: Mark Francis
authors.initials: MF
authors.lastname: Bird
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Division of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
authors.forename: David George
authors.initials: DG
authors.lastname: Lambert
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, 44121 Ferrara, Italy; Laboratorio per le tecnologie delle terapie avanzate (LTTA), University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Severo
authors.initials: S
authors.lastname: Salvadori
authors.affiliation: Department of Medical Science, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Girolamo
authors.initials: G
authors.lastname: Calo
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D018847:Opioid Peptides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011957:Receptors, Opioid / Q000378:metabolism*; D013329:Structure-Activity Relationship; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D018847:Opioid Peptides; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; D000097629:Nociceptin
keywords: Calcium mobilization assay; NOP receptor; Nociceptin/orphanin FQ; Peptide synthesis; [(35)S]GTPγS binding assay