Abstract
Delta-opioid receptors (DOR) present on T cells have been shown to mediate the immunomodulatory effects of endogenous and synthetic DOR agonists on T cells. Considerable evidence indicates that there is stimulated transcription of DOR gene in activated T cells, which is correlated with augmented expression of DOR and enhanced capacity of DOR agonists to affect the T-cell's functions. However, the molecular mechanism underlying the stimulated transcription of the DOR gene in activated T cells is still unclear. In the present study, we analyzed a 1.3-kb DNA fragment immediately upstream of the translation start site (-1300 to +1 bp, with the translation start site designated as +1) of the mouse DOR gene in EL-4 cells, a mouse lymphoma T cell line that exhibits enhanced expression of DOR transcripts when activated by phytohemagglutinin. Through both in vivo and in vitro experiments, we have demonstrated that increased binding activity of Ikaros at the Ikaros-binding site (-378 to -374) in the DOR promoter is required for the stimulated transcription of DOR gene in phytohemagglutinin-activated T cells.
Highlights
Endogenous and synthetic ␦-opioids have been shown to modulate T-cell proliferation, cytokine production, and calcium mobilization, through the ␦-opioid receptor (DOR)1 on T cells [1,2,3,4]
We analyzed a 1.3-kb DNA fragment immediately upstream of the translation start site (؊1300 to ؉1 bp, with the translation start site designated as ؉1) of the mouse DOR gene in EL-4 cells, a mouse lymphoma T cell line that exhibits enhanced expression of DOR transcripts when activated by phytohemagglutinin
The expression of DOR transcripts is at very low levels in resting T cells, it is significantly increased in activated T cells through a transcriptional mechanism, correlated with augmented expression of DOR protein
Summary
Endogenous and synthetic ␦-opioids have been shown to modulate T-cell proliferation, cytokine production, and calcium mobilization, through the ␦-opioid receptor (DOR) on T cells [1,2,3,4]. We analyzed a 1.3-kb DNA fragment immediately upstream of the translation start site (Ϫ1300 to ϩ1 bp, with the translation start site designated as ϩ1) of the mouse DOR gene in EL-4 cells, a mouse lymphoma T cell line that constitutively expresses low level of DOR transcripts [5] and can be activated by low concentrations of phytohemagglutinin (PHA) [8]. Through both in vivo and in vitro experiments, we have demonstrated that increased binding activity of Ikaros at the Ikaros-binding site (Ϫ378 to Ϫ374) in the DOR promoter is required for the stimulated transcription of the DOR gene in PHA-activated EL-4 cells
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