title: Regulation of expression of 1,25D3-MARRS/ERp57/PDIA3 in rat IEC-6 cells by TGF beta and 1,25(OH)2D3.
abstract: We examined the transcriptional regulation of expression of the redox-sensitive Membrane-Associated-Rapid Response, Steroid-binding (1,25D(3)-MARRS) protein specific for 1,25(OH)(2)D(3) in a rat small intestinal cell line, IEC-6, that demonstrates rapid responses to 1,25(OH)(2)D(3). 1,25D(3)-MARRS binds and is activated by 1,25(OH)(2)D(3), but is not itself up-regulated by treatment with 1,25(OH)(2)D(3), nor is there a Vitamin D response element (VDRE) in its proximal promoter. We previously reported that transforming growth factor beta (TGFbeta) increased steady state levels of 1,25D(3)-MARRS transcript and protein approximately two-fold [Rohe B, Safford SE, Nemere I, Farach-Carson, MC. Identification and characterization of 1,25D(3)-membrane-associated rapid response, steroid (1,25D(3)-MARRS)-binding protein in rat IEC-6 cells. Steroids 2005;70:458-63]. To determine if this up-regulation could be attributed to the function of a highly conserved consensus smad 3 binding element present in the proximal promoter of the 1,25D(3)-MARRS gene, we created a promoter-reporter [SEAP] construct that was responsive to TGFbeta (200 pM). Deletion or mutation of the smad 3 element greatly reduced the response of the 1,25D(3)-MARRS promoter to TGFbeta. Subsequent studies found that the smad 3 response element is bound by a protein found in the IEC-6 nuclear extract, most likely smad 3. Interestingly, although 1,25(OH)(2)D(3) alone did not increase expression of the 1,25D(3)-MARRS promoter-reporter, co-treatment of transfected IEC-6 cells with 1,25(OH)(2)D(3) and TGFbeta shifted the dose-response curve to a lower effective concentration (100 pM peptide). We conclude that TGFbeta is a transcriptional regulator of 1,25D(3)-MARRS expression via a functional smad 3 element and that cross-talk with non-classical 1,25(OH)(2)D(3)-stimulated pathways occurs. The findings have broad implications for redox-sensitive signaling phenomena including those that regulate phosphate transport in the intestine.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Rohe
authors.forename: Susan E
authors.initials: SE
authors.lastname: Safford
authors.forename: Ilka
authors.initials: I
authors.lastname: Nemere
authors.forename: Mary C
authors.initials: MC
authors.lastname: Farach-Carson
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000502:physiology*; D002460:Cell Line; D005786:Gene Expression Regulation / Q000502:physiology*; D045170:Matrix Attachment Regions; D019704:Protein Disulfide-Isomerases / Q000096:biosynthesis* / Q000235:genetics*; D051381:Rats; D014158:Transcription, Genetic / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D016212:Transforming Growth Factor beta; C513196:PDIA3 protein, rat; D019704:Protein Disulfide-Isomerases; D002117:Calcitriol