2-36[K-4,RYYSA(19-23)]PP a novel Y5-receptor preferring ligand with strongstimulatory effect on food intake

Members of the neuropeptide Y (NPY) family regulate many physiological proc esses via interaction with at least four functional, pharmacologically dist inct Y-receptors. However, selective antagonists developed for several subt ypes have not been useful in defining particular Y-receptor functions in vi vo. To identify critical residues within members of the NPY family required for Y-receptor subtype-selectivity we have determined the contribution of each residue within NPY to receptor binding by replacing them with L-alanin e. In a second study, chimeric peptides where single or stretches of residu es were interchanged between members of the NPY family were generated and r ested in radioligand binding studies. Overall, substituted alanine analogue s exhibited similar orders of affinities at each Y-receptor subtype with no obvious subtype-selectivity. Residues of particular interest are Leu(30) w hich exhibited selectivity for the Y4-receptor, whereas Asp(16) does not ap pear to play any role in ligand binding. Several chimeric peptides, e.g., [ K-4]pancreatic polypeptide ([K-4]PP) and [RYYSA(19-23)]PP clearly showed hi gher affinity at the Y4 and Y5 subtypes compared to the Y1 and Y2 subtypes. in addition, the transfer of a proline residue from position 14 to 13 in p eptide YY decreases its affinity at the Y1-, Y4- and Y5-receptors but is un changed at the Y2 subtype. Combining these results, and with the help of mo lecular modelling, second generation chimeras were designed. The most signi ficant improvement was achieved in chimera 2-36[K-4,RYYSA(19-23)]PP where t he affinity for the Y5 subtype increased by ninefold over that from NPY. Se veral of these compounds were also tested for their ability to stimulate fo od intake in a rat model. Interestingly, again 2-36[K-4,RYYSA(19-23)]PP sho wed the most dramatic effect with a major increase on food intake over a ra nge of doses compared to NPY suggesting a possible synergistic effect of se veral Y-receptors on feeding behaviour. (C) 2000 Elsevier Science B.V. All rights reserved.