A Role for the Circadian Clock Protein Per1 in the Regulation of the NaCl Co-transporter ( NCC) and the with-no-lysine Kinase ( WNK) Cascade in Mouse Distal Convoluted Tubule Cells

Background: The role of the circadian protein Per1 in the regulation of sodium reabsorption in the distal convoluted tubule (DCT) is unknown. Results: Per1 transcriptionally regulates the sodium transporter NCC and the WNK kinase cascade. Conclusion: Per1 regulates sodium reabsorption in the DCT through NCC and the WNK cascade. Significance: These data demonstrate a role for Per1 in the regulation of renal sodium transporters. It has been well established that blood pressure and renal function undergo circadian fluctuations. We have demonstrated that the circadian protein Per1 regulates multiple genes involved in sodium transport in the collecting duct of the kidney. However, the role of Per1 in other parts of the nephron has not been investigated. The distal convoluted tubule (DCT) plays a critical role in renal sodium reabsorption. Sodium is reabsorbed in this segment through the actions of the NaCl co-transporter (NCC), which is regulated by the with-no-lysine kinases (WNKs). The goal of this study was to test if Per1 regulates sodium transport in the DCT through modulation of NCC and the WNK kinases, WNK1 and WNK4. Pharmacological blockade of nuclear Per1 entry resulted in decreased mRNA expression of NCC and WNK1 but increased expression of WNK4 in the renal cortex of mice. These findings were confirmed by using Per1 siRNA and pharmacological blockade of Per1 nuclear entry in mDCT15 cells, a model of the mouse distal convoluted tubule. Transcriptional regulation was demonstrated by changes in short lived heterogeneous nuclear RNA. Chromatin immunoprecipitation experiments demonstrated interaction of Per1 and CLOCK with the promoters of NCC, WNK1, and WNK4. This interaction was modulated by blockade of Per1 nuclear entry. Importantly, NCC protein expression and NCC activity, as measured by thiazide-sensitive, chloride-dependent Na-22 uptake, were decreased upon pharmacological inhibition of Per1 nuclear entry. Taken together, these data demonstrate a role for Per1 in the transcriptional regulation of NCC, WNK1, and WNK4.