Role of an AP-2-like element in transcriptional regulation of mouse μ-opioid receptor gene

Jane L. Ko, Hsien Ching Liu, Horace H Loh

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25 Scopus citations


Previously, several important cis-elements and trans-factors have been shown to play a functional role in the proximal promoter of mouse μ-opioid receptor (MOR) gene. In this study, we defined another functional element located the in -450 to -400 bp (translational start site designated as +1) region of the proximal promoter, which is also essential for the full promoter activity. It is designated as the morAP-2-like element for its sequence homologous to the consensus AP-2 element. Surprisingly, electrophoretic mobility shift analysis (EMSA) revealed that Sp1 and Sp3, but not AP-2 proteins, were specifically bound to the morAP-2-like element. Mutation of the morAP-2-like element, resulting in a loss of Sp binding, led to an approximately 35% decrease in activity, further confirming the positive role of the morAP-2-like element in MOR gene expression. Dephosphorylation of Sp proteins with alkaline phosphatase also decreased Sp binding to the morAP-2-like element in EMSA, suggesting phosphorylation of Sp is essential for its binding to this element. However, direct or indirect activation of PKA, a classical G-protein coupled signaling pathway, resulted in no significant change of Sp binding to the morAP-2-like element, nor of the promoter activity the SH-SY5Y cells, MOR expressing cells, suggesting that phosphorylation of Sp does not involve PKA. These results suggest that the binding of different phosphorylated forms of Sp proteins to the morAP-2-like element may contribute to the fine tuning of MOR expression in different cells.

Original languageEnglish (US)
Pages (from-to)153-162
Number of pages10
JournalMolecular Brain Research
Issue number1-2
StatePublished - Apr 10 2003


  • AP-2-like element
  • Mouse MOR promoter
  • Phosphorylation/dephosphorylation
  • Sp1/3

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