STRUCTURE-ACTIVITY-RELATIONSHIPS WITH NEUROPEPTIDE-Y ANALOGS - A COMPARISON OF HUMAN Y-1-LIKE, Y-2-LIKE AND RAT Y-2-LIKE SYSTEMS

A structure-activity study utilising 36 synthetic Ala-analogues of the 36-residue oligopeptide neuropeptide Y (NPY) has been performed with mucosal preparations from the rat jejunum (Y-2-like receptor) and comp ared with receptor displacement binding in the human neuroblastoma cel l lines, SMS-KAN, (Y-2-receptors) and SK-N-MC cells (Y-1-receptors). E ach amino acid of the natural sequence was replaced by L-alanine, and the four intrinsic alanine residues at position 12, 14, 18 and 23 were replaced by glycine. The purified peptides were characterized by elec trospray mass spectrometry, analytical HPLC and amino acid analysis. B inding was investigated using membranes prepared from either SMS-KAN o r SK-N-MC cells. The activity of each Ala-NPY analogue was assessed in mucosal preparations of rat jejunum, where NPY and PYY exert antisecr etory responses which are Y-2-like in pharmacology. Fourteen analogues with L-alanine replacements at position 3, 5, 8, 13, 20, 21, 22, 26, 27, 28, 29, 30, 34 and 36 were selected, none of which exhibited any a ntagonism of NPY responses. An order of agonist potency showed [Ala(3) ] NPY and [Ala(30)] NPY equipotent with NPY, a 4 - 20-fold loss of act ivity with [Ala(5)] NPY, [Ala(13)] NPY, [Ala(20)] NPY, [Ala(21)] NPY a nd [Ala(22)] NPY; a 50-100-fold loss of activity, [Ala(8)] NPY, [Ala(2 7)] NPY, [Ala(28)] NPY and [Ala(36)] NPY, while [Ala(34)] NPY was inac tive. This structure-activity relationship is similar to, but not the same as that observed in Y-2-expressing SMS-KAN cells. (C) 1998 Elsevi er Science B.V. All rights reserved.