“ Characterization of Neuropeptide S Derivatives at the Human NPS Receptor ”

Neuropeptide S (NPS) is the endogenous 20-amino acid neuropeptide that selectively binds and activates a previously orphan GPCR, referred to as the neuropeptide S receptor (NPSR). Activation of NPSR induces intracellular calcium mobilization and cyclic AMP (cAMP) accumulation, indicating coupling to Gq and Gs signaling pathways and resulting in increased cellular excitability. The NPS/NPSR system is an important signalling pathway in both central and peripheral nervous systems and plays a role in the modulation of multiple physiological functions, including anxiety-related behaviour, learning and memory processes, locomotion, food intake, sleep-wake regulation, pain and drug addiction. In this thesis, the activity of Neuropeptide S derivatives at the human NPS receptor was assessed. Receptor activation was evaluated using a fluorescence-based calcium mobilization assay. In the calcium mobilization assay, NPS acted as a full agonist, displaying a high maximal efficacy (Emax= 208%) and high potency (pEC50= 8.88), in line with literature results. Consequently, NPS peptide derivatives (NPS(2-12)-NH2, NPS(1-10)-NH2, Ac[D-Cys5]NPS(2-12)-NH2 and Ac-[tbu-D-Gly5]NPS(2-12)-NH2) were evaluated alongside with tetrapeptide ligands SFKN-NH2 and SFRN-NH2 and a series of derivatives (Ac-Cha-KN-NH2, Ac-Cha-RN-NH2, Ac-SFKN-NH2, Ac-SFRN-NH2, S-Cha-KN-NH2 and S-Cha-RN-NH2). Results in terms of detailed in vitro pharmacological profiles are reported in this thesis work, and these findings may support further studies of innovative pharmacological entities acting at the NPS/NPSR system.