Transcriptional activation of human mu-opioid receptor gene by insulin-like growth factor-I in neuronal cells is modulated by the transcription factor REST.
The human mu-opioid receptor gene (OPRM1) promoter contains a DNA sequence binding the repressor element 1 silencing transcription factor (REST) that is implicated in transcriptional repression. We investigated whether insulin-like growth factor I (IGF-I), which affects various aspects of neuronal induction and maturation, regulates OPRM1 transcription in neuronal cells in the context of the potential influence of REST. A series of OPRM1-luciferase promoter/reporter constructs were transfected into two neuronal cell models, neuroblastoma-derived SH-SY5Y cells and PC12 cells. In the former, endogenous levels of human mu-opioid receptor (hMOPr) mRNA were evaluated by real-time PCR. IGF-I up-regulated OPRM1 transcription in: PC12 cells lacking REST, in SH-SY5Y cells transfected with constructs deficient in the REST DNA binding element, or when REST was down-regulated in retinoic acid-differentiated cells. IGF-I activates the signal transducer and activator of transcription-3 signaling pathway and this transcription factor, binding to the signal transducer and activator of transcription-1/3 DNA element located in the promoter, increases OPRM1 transcription. We propose that a reduction in REST is a critical switch enabling IGF-I to up-regulate hMOPr. These findings help clarify how hMOPr expression is regulated in neuronal cells.
Bedini
Andrea
A
Department of Pharmacology, University of Bologna, Bologna, Italy.
Baiula
Monica
M
Spampinato
Santi
S
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D016716:PC12 Cells; D011485:Protein Binding / Q000235:genetics; D051381:Rats; D017450:Receptors, Opioid, mu / Q000235:genetics* / Q000378:metabolism*; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*; D014212:Tretinoin / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics; D000099229:RE1-Silencing Transcription Factor
D004268:DNA-Binding Proteins; D007334:Insulin-Like Growth Factor I; D017450:Receptors, Opioid, mu; D012097:Repressor Proteins; D014212:Tretinoin; D000099229:RE1-Silencing Transcription Factor