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 6

Sgk1 phosphorylates Af9 and regulates transcription of ENaCα and other aldosterone target genes in vivo in mouse kidneys.

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Sgk1 phosphorylates Af9 and regulates transcription of ENaCα and other a...
(A and B) Low-salt diet coordinately increases Af9 phosphorylation and mRNA expression of Sgk1 and ENaCα in mouse kidneys. Whole lysates from the right kidneys of WT mice (Sgk1+/+) fed the indicated diet were pooled within the group (n = 3 in each group, similar for B–E) and analyzed by IB probed with the antibodies shown. Similarly, total RNA from the left kidneys was pooled within the group (n = 3) and analyzed with primers specific for the indicated genes. Representative agarose gel analyses of the final quantitative RT-PCR with the mean of 3 different measurements are shown. SEM was less than 20% in all cases. (C–E) Af9 phosphorylation is regulated by salt intake, is achieved in an Sgk1-dependent or -independent manner, and correlates with expression of several aldosterone target genes. As in A, except that Sgk1+/+ mice or their age- and sex-matched Sgk1–/– littermates fed the indicated diets were used and that additional aldosterone target genes were examined (n = 3 for each group and condition). Arrow denotes unknown protein. CTGF, connecting tissue growth factor.