title: Structure-activity study at positions 3 and 4 of human neuropeptide S.
abstract: Neuropeptide S (NPS) has been identified as the endogenous ligand of a previously orphan receptor now named NPSR. Previous studies demonstrated that the N-terminal sequence Phe(2)-Arg(3)-Asn(4) of the peptide is crucial for biological activity. Here, we report on a focused structure-activity study of Arg(3) and Asn(4) that have been replaced with a series of coded and non-coded amino acids. Thirty-eight human NPS analogues were synthesized and pharmacologically tested for intracellular calcium mobilization using HEK293 cells stably expressing the mouse NPSR. The results of this study demonstrated the following NPS position 3 structure-activity features: (i) the guanidine moiety and its basic character are not crucial requirements, (ii) an aliphatic amino acid with a linear three carbon atom long side chain is sufficient to bind and fully activate NPSR, (iii) the receptor pocket allocating the position 3 side chain can accommodate slightly larger side chains at least to a certain degree [hArg, Arg(NO2) or Arg(Me)2 but not Arg(Tos)]. Position 4 seems to be more sensitive to amino acids replacement compared to position 3; in fact, all the amino acid replacements investigated produced either an important decrease of biological activity or generated inactive derivatives suggesting a pivotal role of the Asn(4) side chain for NPS bioactivity.
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Pharmacology and Neuroscience Center, University of Ferrara, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Camarda
authors.forename: Claudio
authors.initials: C
authors.lastname: Trapella
authors.forename: Girolamo
authors.initials: G
authors.lastname: Calo'
authors.forename: Remo
authors.initials: R
authors.lastname: Guerrini
authors.forename: Anna
authors.initials: A
authors.lastname: Rizzi
authors.forename: Chiara
authors.initials: C
authors.lastname: Ruzza
authors.forename: Stella
authors.initials: S
authors.lastname: Fiorini
authors.forename: Erika
authors.initials: E
authors.lastname: Marzola
authors.forename: Rainer K
authors.initials: RK
authors.lastname: Reinscheid
authors.forename: Domenico
authors.initials: D
authors.lastname: Regoli
authors.forename: Severo
authors.initials: S
authors.lastname: Salvadori
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry / Q000378:metabolism; D001216:Asparagine / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007668:Kidney / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D008024:Ligands; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010649:Phenylalanine / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D009479:Neuropeptides; C506531:neuropeptide S, human; D010649:Phenylalanine; D001216:Asparagine; D001120:Arginine; D002118:Calcium