Porcine glucocorticoid receptor (NR3C1) gene: Tissue-specificity of transcriptional strength and glucocorticoid responsiveness of alternative promoters

• Glucocorticoid receptor (GR) expression of Large white pig showed tissue-specific.
• Exon 1–4 and 1–10 were abundant in tissue detected, some others varied among tissues.
• GR promoters activities were cell-specific, long promoters were more authentic.
• GR promoters containing nGRE was activated by GCs stimulation.
• GR promoter sensitivity to GCs was associated with nGRE number located on it.

Glucocorticoid receptor (GR) is transcribed in a tissue- and cell-specific manner with multiple exon 1 mRNA variants driven by selective promoters. We recently cloned and characterized the 5.3 kb proximal promoter sequence of porcine GR gene containing 7 untranslated alternative first exons each processed by a distinct promoter. In this study, we showed tissue-specific expression of total GR and its exon 1 mRNA variants in hippocampus, muscle and liver of pigs. Total GR mRNA was most abundant in liver, followed by muscle and hippocampus in descending order. Among all the GR exon 1 mRNA variants detected, GR exon 1–9/10 and 1–4 were the most predominant variants in all the three tissues. The abundance of GR exon 1–4 mRNA was similar to that of 1–10 in muscle, but was significantly lower than 1–10 in liver and hippocampus. The activities of truncated short (S) and long (L) promoters of respective GR exon 1 mRNA variants were analyzed by luciferase reporter assay in 3 representative cell lines, SY5Y, C2C12 and HepG2. S1–10 and S1–4 demonstrated significantly higher activities than other short promoters in all the cell lines examined. Nevertheless, the strongest activity and cell specificity were detected for L1–10 promoter, which was consistent with the predominant exon 1–9/10 expression in porcine tissues. Moreover, with 3 potential nGRE binding sites, L1–10 promoter was more sensitive to dexamethasone (DEX) in HepG2. Our data provide basic knowledge of the transcriptional mechanism underlying the tissue- and cell-specific expression of porcine GR under basal or ligand-stimulated conditions.