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1 Physiology, Dartmouth Medical School, Lebanon, New Hampshire, United States
* To whom correspondence should be addressed. E-mail: aniko.fejes-toth{at}dartmouth.edu.
Aldosterone is the principal regulator of Na homeostasis, and thereby blood pressure. One of the main targets of aldosterone is the epithelial sodium channel (ENaC) located in the apical membrane of target cells. Previous studies identified several genes involved in the regulation of ENaC such as SGK1; however SGK1 knockout mice have only a mild salt losing phenotype indicating that further genes must be involved in the action of aldosterone. In our search for further aldosterone-regulated genes, we discovered that aldosterone, at physiological concentrations, induces the expression of the promyelocytic leukemia zinc finger protein (PLZF) in renal cortical collecting duct (CCD) cell lines that stably express mineralocorticoid receptors (MRs). This effect is rapid and does not require de novo protein synthesis suggesting a direct action. Surprisingly, stable overexpression of human or mouse PLZF isoforms significantly decreased transepithelial Na transport in CCD cells while having no effect on the integrity of the monolayers. In parallel with the decline in Na transport, PLZF suppressed the mRNA levels of beta and gamma ENaC subunits. These observations suggest that PLZF is a negative regulator of ENaC in renal epithelial cells and might be part of a negative feedback loop that limits aldosterones stimulatory effects on sodium reabsorption.
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