title: Retinoic acid-induced nNOS expression depends on a novel PI3K/Akt/DAX1 pathway in human TGW-nu-I neuroblastoma cells.
abstract: Neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) acts as a neurotransmitter and intracellular signaling molecule in the central and peripheral nervous system. NO regulates multiple processes like neuronal development, plasticity, and differentiation and is a mediator of neurotoxicity. The nNOS gene is highly complex with 12 alternative first exons, exon 1a-1l, transcribed from distinct promoters, leading to nNOS variants with different 5'-untranslated regions. Transcriptional control of the nNOS gene is not understood in detail. To investigate regulation of nNOS gene expression by retinoic acid (RA), we used the human neuroblastoma cell line TGW-nu-I as a model system. We show that RA induces nNOS transcription in a protein synthesis-dependent fashion. We identify the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and the atypical orphan nuclear receptor DAX1 (NR0B1) as critical mediators involved in RA-induced nNOS gene transcription. RA treatment increases DAX1 expression via PI3K/Akt signaling. Upregulation of DAX1 expression in turn induces nNOS transcription in response to RA. These results identify nNOS as a target gene of a novel RA/PI3K/Akt/DAX1-dependent pathway in human neuroblastoma cells and stress the functional importance of the transcriptional regulator DAX1 for nNOS gene expression in response to RA treatment.
authors.affiliation: II. Medizinische Klinik, Technische Universität München, 81675 Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Nagl
authors.forename: Katrin
authors.initials: K
authors.lastname: Schönhofer
authors.forename: Barbara
authors.initials: B
authors.lastname: Seidler
authors.forename: Jörg
authors.initials: J
authors.lastname: Mages
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Allescher
authors.forename: Roland M
authors.initials: RM
authors.lastname: Schmid
authors.forename: Günter
authors.initials: G
authors.lastname: Schneider
authors.forename: Dieter
authors.initials: D
authors.lastname: Saur
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D047468:Immunoprecipitation; D009447:Neuroblastoma / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000096:biosynthesis / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000187:drug effects / Q000378:metabolism; D012097:Repressor Proteins / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins; C539965:NR0B1 protein, human; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D014212:Tretinoin; D052248:Nitric Oxide Synthase Type I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt