title: The expression of aquaporin-1 in the medulla of the kidney is dependent on the transcription factor associated with hypertonicity, TonEBP.
abstract: Expression of aquaporin-1 (AQP1) and -2 (AQP2) channels in the kidney are critical for the maintenance of water homeostasis and the operation of the urinary concentrating mechanism. Hypertonic stress induced in inner medullary (IMCD3) cells by addition of NaCl to the medium substantially up-regulated the mRNA and protein expression of AQP1, suggesting that its activation occurs at a transcriptional and a translational levels. In contrast, no up-regulation of AQP1 was observed when these cells were exposed to the same tonicity by addition of urea. To explore the transcriptional activation of aqp1 under hypertonic stress, we examined the role of the transcription factor associated with hypertonicity, TonEBP. Treatment of IMCD3 cells with the TonEBP inhibitor rottlerin or silencing its expression with specific shRNA technology led to a substantial reduction in AQP1 expression under hypertonic conditions. Moreover, we defined a conserved TonEBP binding site located 811 bp upstream of the aqp1 exon that is essential for its expression. Single site-directed mutation of this TonE site led to a 54 ± 5% (p < 0.01) decrease in AQP1 luciferase-driven activity under hypertonic stress. TonEBP mutant mice display marked decrement in the expression of AQP1 in the inner medulla. In conclusion, these data demonstrate that TonEBP is necessary for the regulation of AQP1 expression in the inner medulla of the kidney under hypertonic conditions.
authors.affiliation: Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado, Denver, Colorado 80045, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Lanaspa
authors.forename: Ana
authors.initials: A
authors.lastname: Andres-Hernando
authors.forename: Nanxing
authors.initials: N
authors.lastname: Li
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rivard
authors.forename: Christina
authors.initials: C
authors.lastname: Cicerchi
authors.forename: Carlos
authors.initials: C
authors.lastname: Roncal-Jimenez
authors.forename: Robert W
authors.initials: RW
authors.lastname: Schrier
authors.forename: Tomas
authors.initials: T
authors.lastname: Berl
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D051398:Aquaporin 1 / Q000096:biosynthesis* / Q000235:genetics; D051399:Aquaporin 2 / Q000235:genetics / Q000378:metabolism; D001578:Benzopyrans / Q000494:pharmacology; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing; D007679:Kidney Medulla / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009997:Osmotic Pressure / Q000187:drug effects / Q000502:physiology; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology; D020218:Response Elements / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D014508:Urea / Q000494:pharmacology
chemical_list: D000098:Acetophenones; C496021:Aqp1 protein, mouse; C496024:Aqp2 protein, mouse; D051399:Aquaporin 2; D001578:Benzopyrans; D004791:Enzyme Inhibitors; C492200:Nfat5 protein, mouse; D014157:Transcription Factors; D051398:Aquaporin 1; D012965:Sodium Chloride; D014508:Urea; C085746:rottlerin