FIG. 3.

TonEBP regulation of AQP2 promoter activity. AQP2 (A) or TauT (B) reporter constructs along with DN-TonEBP, or empty backbone FLAG-CMV2, were transfected into NP cells, and luciferase activity was measured. Expression of DN-TonEBP resulted in a complete suppression of hypertonicity-mediated induction in AQP2 and TauT promoter activity. When pTonEBP was co-expressed with AQP2 (C) or TauT (D) under isotonic conditions, there was a significant increase in activity of both the reporters in NP cells. Note, the activity of mutant AQP2 reporter was unaffected by TonEBP. NFAT5-null and wildtype MEFs were transfected with AQP2 (E) or TauT (F) reporter and cultured under isotonic or hypertonic conditions (500 mosmol/kg). Wildtype cells evidenced an increase in activity of both the reporters under hypertonic conditions. In contrast, in hypertonic media, null MEFs showed a significant suppression of AQP2 reporter activity, whereas TauT activity remained unchanged. Values shown are the mean ± SD of three independent experiments performed in triplicate, *p < 0.05.