The effects of dephosphorylation signal on glucocorticoid hormone‐mediating GLUT5 expression in intestinal cells

Glucocorticoid hormone is considered to be important for differentiation and maturation of mammalian intestine through glucocorticoid hormone receptor (GR), which belongs to a superfamily of nuclear receptors. Recently, some laboratories showed that dephosphorylation of nuclear receptors are important for their activity and target genes expression. In this study, we examined the relationship between glucocorticoid hormone and dephosphorylation signals for a putative GR target genes, GLUT5 expression in intestinal cell line, Caco‐2. Expression of GLUT5 gene was induced in Caco‐2 cells treated by both glucocorticoid hormone and inhibitor of p44/42 MAP kinase activity. The induction of GLUT5 gene by co‐treatment of glucocorticoid hormone and p44/42 MAP kinase inhibitor was correlated with not only the binding activity of GR, but also acetylation of histone H3 and H4 on the upstream region of GLUT5 gene. Our results suggest that the inactivation of p44/42 MAP kinase enhances glucocorticoid hormone‐mediating GLUT5 gene expression in Caco‐2 cell through controlling the activity of GR binding and histone acetylation on the GLUT5 gene.