title: Involvement of activator protein-1 in transcriptional regulation of the human mu-opioid receptor gene.
abstract: mu-Opioid receptors mediate such opioid effects as analgesia, euphoria, and immunomodulation. Gene expression of mu-opioid receptors can be modulated by various substances, including cytokines, hormones, and drugs. Some of these stimuli (e.g., IL-1beta and cocaine) have been shown to activate members of the AP-1 transcription factor family. In addition, transcription of the mu-opioid receptor gene is induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, which in turn is an activator of AP-1 transcription factors. This indicates that signaling pathways involving protein kinase C and activator protein 1 (AP-1) transcription factors are important for the specific expression pattern of the mu-opioid receptor gene. In this report, we show that TPA activates AP-1 as well as the transcription factor nuclear factor kappaB (NFkappaB) in the mu-opioid receptor expressing neuroblastoma cell line SH SY5Y. In transfection experiments performed in these cells, both factors trans-activate expression of reporter gene constructs containing the human mu-opioid receptor gene promoter. By excluding the effects of TPA on NFkappaB with the specific NFkappaB inhibitor sulfasalazine, AP-1 regulatory elements were localized. Two AP-1 elements, which differ in one nucleotide each from the classic AP-1 binding site, were delineated to positions -2388 and -1434 of the promoter. Independent of their orientation, these elements conferred TPA responsiveness on the heterologous thymidine kinase promoter. AP-1 binding to these elements was confirmed using electrophoretic mobility shift and immunoshift assays.
authors.affiliation: Department of Pharmacology, University of Magdeburg, Magdeburg, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Börner
authors.forename: Volker
authors.initials: V
authors.lastname: Höllt
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kraus
mesh_terms: D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D016328:NF-kappa B; D017450:Receptors, Opioid, mu; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate