[D-TRP32]Neuropeptide Y: A Competitive Antagonist of NPY in Rat Hypothalamus

Abstract

Neuropeptide Y (NPY) is a potent orexigenic peptide. Structure-activity studies have revealed that nearly the entire sequence of NPY is required to elicit feeding responses. Therefore, in order to develop antagonistic peptides for NPY-induced feeding, we synthesized full-length analogs of NPY, substituting D-Trp in the C-terminal receptor binding region, and screened their activity in rat hypothalamus. Although [D-Trp36]NPY and [D-Trp34]NPY inhibited isoproterenol-stimulated hypothalamic membrane adenylate cyclase activity, [D-Trp32]NPY exhibited no intrinsic activity. Furthermore, [D-Trp32]NPY inhibited [125I]NPY binding to rat hypothalamic membranes with a potency comparable to that of NPY. The presence of 30 and 300 nM concentrations of [D-Trp32]NPY shifted the inhibitory dose-response curve of NPY on isoproterenol-stimulated hypothalamic membrane adenylate cyclase activity parallel to the right with comparable KB values. Moreover, in vivo experiments in rats revealed that [D-Trp32]NPY (10 micrograms) significantly attenuated the 1-h feeding response induced by NPY (1 microgram). Several other substitutions at position 32 including 2-D-Nal resulted in agonist activity, suggesting that there are strict structural requirements to induce the antagonistic property in NPY. These findings confirm that [D-Trp32]NPY is a competitive antagonist of NPY in both in vitro and in vivo systems. Analogs based on [D-Trp32]NPY may have potential clinical application, since NPY has been implicated in the pathophysiology of a number of feeding disorders including obesity, anorexia, and bulimia.

High Identification Rates of Endogenous Neuropeptides from Mouse Brain

“…Neuropeptide Y and galanin are of high interest in various biological studies due to their important roles such as food intake control and cognition. Although they are abundant in the brain, 43 they have not been reported in previous neuropeptidomic studies with high confidence, probably because of its high hydrophobicity and long sequence. 44 The reliable identification of such long and hydrophobic neuropeptides using our approach assists an exploration of their roles in physiological and behavioral processes.…”

Complete L‐Alanine Scan of Neuropeptide Y Reveals Ligands Binding to Y1 and Y2 Receptors with Distinguished Conformations

“…The C-terminal tetrapeptide builds a turn structure and its correct folding and orientation is of utmost importance because the affinity is only provided after stabilizing this conformation. The role of Thr32 is not clear, since replacement by Ala led to a loss of affinity by 103-fold, whereas high affinity and antagonistic properties are reported for a peptide with the exchange by D-TY (Balasubramaniam et al, 1994). Part of the amino acids of the a-helix may be involved as well as the properly orientated N-terminal segment.…”

The First Selective Agonist for the Neuropeptide YY5Receptor Increases Food Intake in Rats

“…However, it has also been shown that both Y 1 and Y 5 receptor antagonists can inhibit NPY-induced food intake (13,14). One limitation of the agonists currently used for in vivo studies is the lack of receptor selectivity; NPY and PYY bind to the receptors Y 1 (12), but antagonism against NPY-induced increase in food intake has been observed as well (16,17 Because highly specific tools to investigate the Y 5 receptor activity are still missing, we have focused our work on the design of NPY receptor agonists with both high affinity and selectivity for the Y 5 subtype. It is well established that the C-terminal part of NPY represents the interaction site with the Y receptors and that amino acid exchange is poorly tolerated in the region 33-36 (49); therefore, we induced a conformational change within the peptide region that mediates receptor binding by introducing the ␤-turn-inducing dipeptide Ala-Aib (aminoisobutyric acid) (19) (21).…”