FP06-5 Renal Mineralocorticoid Receptor Expression Is Regulated By Tis11b-Mediated Post-Transcriptional Control: Pathophysiological Implications

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 381-386-Steroid Hormone Actions, Biosynthesis & Metabolism
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-383
Say Viengchareun*1, Ingrid Lema2, Vixra Keo2, Larbi Amazit3, Jerome Nevoux2, Laetitia Martinerie4, Nadia Cherradi5 and Marc Lombes6
1Inserm, Le Kremlin Bicetre, France, 2Inserm U693, Le Kremlin-Bicetre, France, 3inserm u693, le kremlin bicetre, France, 4INSERM U693, Le Kremlin Bicetre, France, 5INSERM U1036, Grenoble, France, 6Fac de Medicine Paris-SUD, Le Kremlin-Bicetre, France
The Mineralocorticoid Receptor (MR, NR3C2) mediates sodium-retaining action of aldosterone. MR is highly expressed in the distal nephron where the renal corticopapillary gradient generates strong variations in extracellular fluid tonicity. This osmotic gradient, pivotal for the regulation of ion and water transport, is impaired during renal development and in various kidney diseases. These pathophysiological conditions are accompanied by variations of renal MR expression; however, the mechanisms regulating MR expression remain sparse.

We showed previously that post-transcriptional events control renal MR abundance (Viengchareun Mol Endo 2009). Here, using cortical collecting duct KC3AC1 cells, we show that the RNA Binding Protein Tis11b (a member of tristetraprolin/ZFP36 family) induces a dramatic reduction of MR expression under hypertonicity. Consistent with a Tis11b-mediated MR downregulation mechanism, hypertonicity induces a 2-4-fold increase of Tis11b mRNA and protein levels, concomitant with the decreased MR expression. In contrast, RNAi-dependent reduction of Tis11b expression induces the increase of MR expression level. We suggest that Tis11b modulates MR mRNA stability/degradation through binding to Adenine/Uridine Rich Elements (AURE), located in the 3’-UnTranslated Region (3’-UTR) of MR mRNA. Eight highly conserved AURE were indeed identified in the 3’-UTR of MR mRNA.

To examine whether MR transcript was a direct target of Tis11b, the entire 3’-UTR of MR mRNA was subcloned downstream of a luciferase reporter gene and truncated mutants, carrying or lacking AURE, were generated. Cotransfection assays in HEK 293 cells showed that Tis11b induces a 2-fold reduction in luciferase activity of AURE-containing constructs. RNA-ChiP assays demonstrated that endogenously expressed Tis11b physically interacts with MR mRNA AURE in KC3AC1 cells. Finally, to demonstrate the physiological relevance of our findings, we challenged the renal osmotic gradient and demonstrated that mice present with a modification in renal MR expression under water deprivation or diuretic treatment (furosemide, indapamide).

Our data are important to explain the partial aldosterone resistance associated with cyclic variations of renal MR expression during the perinatal period. Whether such regulatory post-transcriptional mechanisms occur in other MR target tissues (cardiovascular and central nervous system) or are altered in kidney diseases and hypertension remains to be established.

Nothing to Disclose: SV, IL, VK, LA, JN, LM, NC, ML

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was in part supported by an ANR grant (ANR 2011 EPHIMIR, BSV1 028 01), and by Inserm and Université Paris-Sud fundings.