Replacement of Thr32 and GIn34 in the C-Terminal Neuropeptide Y Fragment 25-36 by cis-Cyclobutane and cis-Cyclopentane β-Amino Acids Shifts Selectivity toward the Y4 Receptor

Neuropeptide Y (NPY) and pancreatic polypeptide (PP) control central and peripheral processes by activating the G protein coupled receptors YxR (x = 1, 2, 4, 5). We present analogs of the C-terminal fragments 25-36 and 32-36 of NPY and PP containing (1R,2S)-cyclobutane (beta Cbu) or (1R,2S)cyclopentane (beta 6Cpe) fl-amino acids, which display exclusively Y4R affinity. In particular, [beta Cpe(34)]-NPY-(25-36) is a Y4R selective partial agonist (EC50 41 +/- 6 nM, E-max 71%) that binds Y4R with a K-i of 10 +/- 2 nM and a selectivity >100-fold relative to YiR ancrY2R and >50-fold relative to Y5R Comparably, [Y-32, beta Cpe(34)-NPY(PP)-(32-36) selectively binds and activates Y4R (EC50 94 +/- 21 nM, E-max 73%). The NMR structure of [beta Cpe(34)]NPY-(25-36) in dodecylphosphatidylcholine micelles shows a short helix at residues 27-32, while the C-terminal segment R-33 beta Cpe(34)R(35)Y(36) is extended. The biological properties of the,beta Cbu- or beta Cpe-containing NPY and PP C-terminal fragments encourage the future application of these beta-amino acids in the synthesis of selective Y4R ligands.