Aldosterone-induced Sgk1 relieves Dot1a-Af9–mediated transcriptional repression of epithelial Na+ channel α
Wenzheng Zhang, … , Volker Vallon, Bruce C. Kone
Wenzheng Zhang, … , Volker Vallon, Bruce C. Kone
Published March 1, 2007
Citation Information: J Clin Invest. 2007;117(3):773-783. https://doi.org/10.1172/JCI29850.
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Research Article

Aldosterone-induced Sgk1 relieves Dot1a-Af9–mediated transcriptional repression of epithelial Na+ channel α

Abstract

Aldosterone plays a major role in the regulation of salt balance and the pathophysiology of cardiovascular and renal diseases. Many aldosterone-regulated genes — including that encoding the epithelial Na+ channel (ENaC), a key arbiter of Na+ transport in the kidney and other epithelia — have been identified, but the mechanisms by which the hormone modifies chromatin structure and thus transcription remain unknown. We previously described the basal repression of ENaCα by a complex containing the histone H3 Lys79 methyltransferase disruptor of telomeric silencing alternative splice variant a (Dot1a) and the putative transcription factor ALL1-fused gene from chromosome 9 (Af9) as well as the release of this repression by aldosterone treatment. Here we provide evidence from renal collecting duct cells and serum- and glucocorticoid-induced kinase–1 (Sgk1) WT and knockout mice that Sgk1 phosphorylated Af9, thereby impairing the Dot1a-Af9 interaction and leading to targeted histone H3 Lys79 hypomethylation at the ENaCα promoter and derepression of ENaCα transcription. Thus, Af9 is a physiologic target of Sgk1, and Sgk1 negatively regulates the Dot1a-Af9 repressor complex that controls transcription of ENaCα and likely other aldosterone-induced genes.

Authors

Wenzheng Zhang, Xuefeng Xia, Mary Rose Reisenauer, Timo Rieg, Florian Lang, Dietmar Kuhl, Volker Vallon, Bruce C. Kone

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Figure 2

Af9 phosphorylation directly correlates with Sgk1 expression in mIMCD3 cells.

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Af9 phosphorylation directly correlates with Sgk1 expression in mIMCD3 c...
(A) Aldosterone coordinately induces Sgk1 expression and Af9 Ser435 phosphorylation. mIMCD3 cells were treated with ethanol or aldosterone (Aldo; 1 μM) for the indicated times and examined by IB with the indicated antibodies. Af9 phosphorylation was apparently affected by both ethanol and aldosterone. The Sgk1 or phosphorylated Af9 abundance (mean ± SE; n = 6) was normalized to the corresponding actin and expressed relative to vehicle-treated cells at the 1-hour time point (assigned as 1). *P < 0.05 versus corresponding –aldo. (B) RNAi knockdown of Sgk1 decreases Af9 phosphorylation. mIMCD3 cells stably transfected with pSilencer-4.1–CMV–Neo negative control vector (Vec), pSgk1-RNAi7 (RNAi7), or pSgk1-RNAi9 (RNAi9) were examined by IB with the indicated antibodies. The same set of stably transfected cells were repeatedly examined as in A. Data were analyzed essentially as in A (n = 4). (C) Overexpression of WT Sgk1, but not the kinase-dead mutant Sgk1, promotes Af9 phosphorylation. mIMCD3 cells were transiently transfected with pcDNA3.1 vector (Vec) or its derivatives encoding WT or kinase-dead mutant Sgk1 (Lys127Met; Mut) and analyzed by IB probed with the indicated antibodies. Data were analyzed similarly as in A (n = 4). *P < 0.05 versus vector control.