Neuropeptide y receptor in bovine hippocampus is a Y 2 receptor

Abstract

[ 125I]NPY bound to a single class of saturable binding sites on bovine hippocampus membranes with a K D of 0.1 nM and B max of 165 fmol/mg of protein. The rank order of potency of NPY fragments and other structurally related peptides to inhibit [ 125I]NPY binding was: PYY ≥ NPY ⪢ BPP ≥ APP and NPY > NPY-(13–36) > NPY-(18– 36) ≥ NPY-(20–36) ⪢ NPY-(26–36) > NPY-(free acid). The identity of the NPY binding site was investigated by affinity labeling. Gel electrophoresis followed by autoradiography revealed a band with a mol mass of 50 kDa. Unlabeled NPY or PYY, but not BPP, HPP and APP, inhibited labeling of [ 125I]NPY to the 50 kDa protein band. Moreover, labeling was inhibited by NPY > NPY- (18–36) ≥ NPY-(13–36) ≥ NPY-(20–36) > NPY-(26–36) > NPY- (free acid). The binding of [ 125I]NPY and the intensity of the cross-linked band were reduced in parallel by increasing concentrations of unlabeled NPY (IC 50 = 0.7 nM and 0.6 nM, respectively). These studies demonstrate that bovine hippocampal membranes contain a 50 kDa [ 125I]NPY binding site that has the ligand specificity characteristic of the Y 2 receptor subtype.