17 beta-Estradiol stimulates mouse neuropeptide Y-Y-1 receptor gene transcription by binding to estrogen receptor alpha in neuroblastoma cells

Several studies have shown that neuropeptide Y (NPY) is involved in the sti mulation of gonadotropin hormone releasing hormone (GnRH) and luteinizing h ormone (LH) secretion and that these effects are modulated by gonadal stero id feedback. The NPY regulation of GnRH release is probably mediated by the activation of the Y-1 receptor subtype. In this study we examined the regu lation of the Y-1 receptor gene transcription by estrogens in transiently t ransfected NG108-15 neuroblastoma glioma cells. A chimeric plasmid containi ng the murine Y-1 receptor promoter fused to the firefly luciferase reporte r gene was induced by approximately 2-fold in response to 17 beta -estradio l treatment. The estrogen-mediated enhancement of luciferase activity was d ose-dependent, blocked by the estrogen receptor (ER) antagonist ICI 182,780 , and was strictly dependent on the presence of ER alpha, since it occurred only in NG108-15 cells cotransfected with an expression vector for the hum an ER. Mutational analysis was performed to investigate whether the hemipal indromic estrogen-responsive elements (EREs) flanking the Y-1 receptor gene are responsible for conferring estradiol inducibility to the Y-1 receptor gene promoter. Mutation of the ERE1 half site at position -932, or mutation of the ERE2 half site at position -809, relative to the ATG, failed to aff ect the 17 beta -estradiol-mediated enhancement of luciferase activity. Con versely, mutation of both ERE1 and ERE2 half sites completely abolished act ivation of luciferase activity induced by estrogen. We also examined whethe r 17 beta -estradiol stimulates the transcriptional activity of the Y1 rece ptor gene by binding to ER beta. Results demonstrated that luciferase activ ity was not modulated by estrogens when cells were transfected with the exp ression plasmid bearing the human ER beta. Moreover coexpression of both ER alpha and ER beta completely abolished the estrogen-induced activation of luciferase activity observed in the presence of ER alpha. Our data suggest that estrogens activate Y-1 receptor gene transcription possibly via a dire ct interaction of ER alpha with the hemipalindromic EREs flanking the Y-1 r eceptor gene. Copyright (C) 2000 S .Karger AG, Basel.