NEUROPEPTIDE-Y AND THE NONPEPTIDE ANTAGONIST BIBP-3226 SHARE AN OVERLAPPING BINDING-SITE AT THE HUMAN Y-1 RECEPTOR

Neuropeptide Y (NPY) is a 36-amino acid peptide that exhibits actions on the cardiovascular system and the central nervous system. NPY can r egulate blood pressure, psychomotor function, anxiety, food intake, an d endocrine secretions. BIBP 3226, the first potent and selective nonp eptide antagonist at the NPY Y-1 receptor, was designed by mimicking t he carboxyl-terminal structure of NPY. We investigated the interaction of NPY and BIBP 3226 with the human Y-1 receptor at the molecular lev el. Alanine mutants at positions Y100, D104, W288, and H298 of the hum an Y-1 receptor showed no or significantly reduced binding for NPY but were not affected in their ability to bind BIBP 3226. Receptors with alanine mutations at positions W163, F173, Q219, N283, F286, and D287 showed reduced binding for both NPY and BIBP 3226. Mutations at other positions were tested (H105, S170, L174, V178, D200, D205, S206, H207, S210, T212, T280, T284, N289, H290, and Q291) and did not affect the binding of NPY or BIBP 3226. The human Y-1 receptor mutant Y211A showe d no affinity for BIBP 3226 but retained wild-type affinity for NPY. B ased on these experimental results, a detailed model for the interacti on of BIBP 3226 with the human Y-1 receptor was developed using a Y-1 receptor model and a three-dimensional model of BIBP 3226. The experim ental results, supported by modeling studies, clearly suggest that the native ligand (NPY) and the antagonist (BIBP 3226) share an overlappi ng binding site.