Different binding sites for the neuropeptide YY1 antagonists 1229U91 and J-104870 on human Y1 receptors

The peptidic Y1 antagonist 1229U9I and the non-peptidic antagonist J-104870 have high binding affinities for the human Y1 receptor. These Y1 antagonis ts show anorexigenic effects on NPY-induced feeding in rats, although they have completely different structures and molecular sizes. To identify the b inding sites of these ligands, we substituted amino acid residues of the hu man Y1 receptor with alanine and examined the abilities of the mutant recep tors to bind the radio-labeled ligands. Alanine substitutions, F98A, D104A, T125A, D200A, D205A, L215A, Q219A, L279A, F282A, F286A, W288A and H298A, i n the human Y1 receptor lost their affinity for the peptide agonist PW, but not for 1229U91 and J-104870, while L303A and F173A lost affinity for 1229 U91 and J-104870, respectively. N283A retained its affinity for 1229U9I, bu t not for PYY and J-104870. Y47A and N299A retained their affinity for J-10 4870, but not for PYY and I229U91. W163A and D287A showed no affinity for a ny of the three ligands. Taken together, these data indicate that the bindi ng sites of I229U91 are widely located in the shallow region of the transme mbrane (TM) domain of the receptor, especially TM1, TM6 and TM7. In contras t, J-104870 recognized the pocket formed by TM4, TM5 and TM6, based on the molecular modeling of the YI receptor and J-104870 complex. In conclusion, 1229U91 and J-104870 have high affinities for Y1 receptors using basically different binding sites. D287 of the common binding site in the TM6 domain could be crucial for the binding of Y1 antagonists. (C) 2001 Elsevier Scien ce Inc. All rights reserved.