RNA-binding protein HuR enhances mineralocorticoid signaling in renal KC3AC1 cells under hypotonicity

Abstract

Mineralocorticoid receptor (MR) mediates the sodium-retaining action of aldosterone in the distal nephron. Herein, we decipher mechanisms by which hypotonicity increases MR expression in renal principal cells. We identify HuR (human antigen R), an mRNA-stabilizing protein, as an important posttranscriptional regulator of MR expression. Hypotonicity triggers a rapid and reversible nuclear export of HuR in renal KC3AC1 cells, as quantified by high-throughput microscopy. We also identify a key hairpin motif in the 3'-untranslated region of MR transcript, pivotal for the interaction with HuR and its stabilizing function. Next, we show that hypotonicity increases MR recruitment onto Sgk1 promoter, a well-known MR target gene, thereby enhancing aldosterone responsiveness. Our data shed new light on the crucial role of HuR as a stabilizing factor for the MR transcript and provide evidence for a short autoregulatory loop in which expression of a nuclear receptor transcriptionally regulating water and sodium balance is controlled by osmotic tone.

miR-324-5p and miR-30c-2-3p Alter Renal Mineralocorticoid Receptor Signaling under Hypertonicity

“…Wild type murine Elavl1 (HuR) 3 -UTR (mHuR 3 -UTR) was amplified by PCR from cDNA using specific primers presented in Supplementary Table S2B, in which SpeI and HindIII restriction sites were introduced to facilitate cloning into the pMIR-Report TM plasmid (Life Technologies, Villebon-sur-Yvette, France). pMIR-mMR-3 -UTR plasmid and Tis11b-encoding pTarget vector were generated as previously described [18]. All plasmids were sequenced to verify nucleotide identity at the Eurofins Genomics platform (Cologne, Germany).…”

“…Previously, we have demonstrated that variations of extracellular tonicity, prevailing in nephron segments, modulate MR expression through post-transcriptional mechanisms involving the recruitment of RNA Binding Proteins (RBPs) [16]. Indeed, we showed that hypertonicity compromises MR signaling by recruiting Tis11b (Tetradecanoyl phorbol acetate inducible sequence 11b), which degrades MR mRNA [17], while HuR (Human antigen R) favors MR mRNA stability [18] and edits MR mRNA [19], thus enhancing MR signaling under hypotonicity. In this context, we could not exclude another working hypothesis involving the recruitment of microRNAs (miRNAs), another class of post-transcriptional regulators.…”

Sexual Dimorphism of Corticosteroid Signaling during Kidney Development

“…Indeed, MR transcript levels decrease under hypertonicity following recruitment of the RNA Binding Protein (RBP) Tis11b (tetradecanoyl phorbol acetate inducible sequence 11b), which physically interacts with 3′-untranslated region (3′-UTR) of MR transcript, thus modulating its mRNA turnover in response to osmotic stress [ 23 ]. On the opposite, MR transcript levels increase under hypotonicity thanks to the recruitment of Human antigen R (HuR), another RBP, which interacts with MR 3′-UTR in the cytoplasm of renal cells to stabilize and increase MR levels, thereby modulating MR signaling [ 24 ]. Accumulating evidence now underscores the pivotal role of microRNAs (miRNAs), an additional class of post-transcriptional regulators, in the control of MR expression in the kidney [ 25 , 26 ].…”

The invention of aldosterone, how the past resurfaces in pediatric endocrinology

“…Conversely, MR transcript and protein levels were shown to increase under hypotonicity by recruiting HuR (Human antigen R), another RBP member of the Hu family. Under hypotonic stress, and rapidly exported from the nuclear compartment to the cytoplasm of renal cells where it interacts with MR 3′-UTR to stabilize and increase MR levels, thereby modulating MR signaling (Lema et al, 2017b). During this past decade, microRNAs (miRNAs) have also emerged as a new class of posttranscriptional regulators (Bartel, 2004;Ozbaki-Yagan et al, 2020).…”