Abstract
Prohibitin (PHB) is a highly conserved protein that has multiple functions in the cell. We recently demonstrated that PHB plays an important role in combating oxidative stress and its expression is down-regulated in human and animal models of inflammatory bowel disease. Little is known regarding the regulation of PHB expression in intestine or other tissues. In this study we examined the regulation of PHB expression in intestinal epithelial cells using the model cell line Caco2-BBE. We successfully cloned the 1192-bp human PHB promoter region and identified the transcription start site 1594 bp upstream from the translation start site due to an intervening intron. We show that the acute phase cytokine interleukin-6 (IL-6) increases PHB protein and mRNA abundance and induces PHB promoter activation. The IL-6 response element site in the PHB promoter is required for maximal basal promoter activity and responsiveness to IL-6. IL-6 also increases binding of nuclear proteins to the IL-6 response element in the PHB promoter that are supershifted by a STAT3 antibody. Both basal promoter activity and IL-6 responsiveness are attenuated by signal transducer and activator of transcription 3 short interference RNA, suggesting that signal transducer and activator of transcription 3 mediates PHB activity by IL-6. Confirming these in vitro results, IL-6(-/-) mice exhibit reduced PHB expression in the colon compared with wild-type mice. These results suggest that IL-6 modulates PHB expression in cultured intestinal epithelial cells and in the intestine in vivo.
Highlights
PHB is a potential tumor suppressor gene, and expression of PHB is altered in gastric, cervical, breast, and colorectal cancer [11,12,13,14,15]
We show that the acute phase cytokine IL-6 increases PHB protein and mRNA expression and induces PHB promoter activation in cultured intestinal epithelial cells
These results suggest that IL-6 modulates PHB expression in cultured intestinal epithelial cells and in the intestine in vivo
Summary
PHB is a potential tumor suppressor gene, and expression of PHB is altered in gastric, cervical, breast, and colorectal cancer [11,12,13,14,15]. The 5Ј-flanking region of the human PHB gene isolated from Caco2-BBE cells was confirmed by sequence comparison with factor of activated T-cells sites are located at Ϫ679 to Ϫ673 bp and at C, relative luciferase activity was measured in serum-deprived Caco2-BBE cells transfected with pGL3 vector, full-length PHB promoter (Ϫ1054), full-length PHB promoter with mutated IL-6RE site (IL-6RE MUT), Ϫ949 deletion construct, or ␣ 2-macroglobulin (␣2-M) promoter (as a positive control) and treated with IL-6 (100 ng/ml) for 6 h.
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