title: Regulation of ROMK (Kir 1.1) channel expression in kidney thick ascending limb by hypertonicity: role of TonEBP and MAPK pathways.
abstract: The present study assessed the mechanisms by which hypertonicity caused by NaCl enhances the renal outer medullary potassium channel (ROMK) mRNA abundance in rat kidney medullary thick ascending limb (MTAL) and in cultured mouse TAL cells. Using the run-off technique, we observed that the ROMK gene transcription rate in nuclei isolated from MTAL fragments was enhanced approximately 40% by a high NaCl medium. In MTAL fragments, hypertonicity (450 mosm) caused by NaCl, not by mannitol or urea, enhanced both ROMK mRNA abundance and tonicity-responsive enhancer binding protein (TonEBP) total abundance and nuclear localization. In an immortalized mouse TAL cell culture in which ROMK is apically expressed, hypertonicity caused by both NaCl and mannitol, not urea, enhanced both ROMK mRNA abundance and TonEBP total abundance and nuclear localization. Confocal microscopy confirmed an increased nuclear translocation of TonEBP in response to NaCl-induced hypertonicity. Finally, inhibition of the p38 MAPK pathway by SB203580 and of the ERK pathway by PD98059 abolished the NaCl-induced stimulation of TonEBP and ROMK. These results establish that mRNA expression of ROMK is augmented in the MTAL by NaCl-induced hypertonicity through stimulation of ROMK gene transcription, and that TonEBP and the p38 MAPK and ERK pathways are involved in this effect.
authors.affiliation: INSERM U426, Faculté de Médecine Xavier Bichat, et Université Paris 7, Paris, France.
authors.forename: Morgan
authors.initials: M
authors.lastname: Gallazzini
authors.forename: Zoubida
authors.initials: Z
authors.lastname: Karim
authors.forename: Maurice
authors.initials: M
authors.lastname: Bichara
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism; D008138:Loop of Henle / Q000187:drug effects* / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D008353:Mannitol / Q000494:pharmacology; D051379:Mice; D009994:Osmolar Concentration; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000378:metabolism* / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D014508:Urea / Q000494:pharmacology
chemical_list: D005419:Flavonoids; D007093:Imidazoles; C510693:Kcnj1 protein, mouse; C510692:Kcnj1 protein, rat; C492200:Nfat5 protein, mouse; C492199:Nfat5 protein, rat; D024661:Potassium Channels, Inwardly Rectifying; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D012333:RNA, Messenger; D014157:Transcription Factors; D008353:Mannitol; D012965:Sodium Chloride; D014508:Urea; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one