title: De-phosphorylation of TRalpha-1 by p44/42 MAPK inhibition enhances T(3)-mediated GLUT5 gene expression in the intestinal cell line Caco-2 cells.
abstract: Thyroid hormone and p44/42 MAPK inactivation are important in intestinal differentiation. We demonstrated not only that treatment with p44/42 MAPK inhibitor U0126 in intestinal cell line Caco-2 cells reduced the phosphorylation of serine and threonine residues of TRalpha-1, but also that T(3) and U0126 synergistically induced GLUT5 gene expression. EMSA demonstrated that the binding activity of TRalpha-1-RXR heterodimer on GLUT5-TRE in nuclear proteins of Caco-2 cells was synergistically enhanced by co-incubation in vitro with T(3) and CIAP, which strongly de-phosphorylates proteins. ChIP and transfection assays revealed that co-treatment of T(3) and U0126 induces TRalpha-1-RXR binding to GLUT5-TRE on the human GLUT5 enhancer region, and recruitment of the transcriptional complex in cells. These results suggest that inactivation of p44/42 MAPK enhances T(3)-induced GLUT5 gene expression in Caco-2 cells through increasing TRalpha-1 transactivity and binding activity to the GLUT5-TRE, probably due to de-phosphorylation of TRalpha-1.
authors.affiliation: Laboratory of Nutritional Physiology, Graduate School of Nutritional and Environmental Sciences, COE Program in the 21st Century, The University of Shizuoka, Shizuoka 422-8526, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Mochizuki
authors.forename: Naomi
authors.initials: N
authors.lastname: Sakaguchi
authors.forename: Satsuki
authors.initials: S
authors.lastname: Takabe
authors.forename: Toshinao
authors.initials: T
authors.lastname: Goda
mesh_terms: D018938:Caco-2 Cells; D015870:Gene Expression; D051296:Glucose Transporter Type 5 / Q000378:metabolism*; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D037021:Thyroid Hormone Receptors alpha / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
chemical_list: D051296:Glucose Transporter Type 5; C495726:SLC2A5 protein, human; D037021:Thyroid Hormone Receptors alpha; D014284:Triiodothyronine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3