title: TonEBP stimulates multiple cellular pathways for adaptation to hypertonic stress: organic osmolyte-dependent and -independent pathways.
abstract: TonEBP (tonicity-responsive enhancer binding protein) is a transcription factor that promotes cellular accumulation of organic osmolytes in the hypertonic renal medulla by stimulating expression of its target genes. Genetically modified animals with deficient TonEBP activity in the kidney suffer from severe medullary atrophy in association with cell death, demonstrating that TonEBP is essential for the survival of the renal medullary cells. Using both TonEBP knockout cells and RNA interference of TonEBP, we found that TonEBP promoted cellular adaptation to hypertonic stress. Microarray analyses revealed that the genetic response to hypertonicity was dominated by TonEBP in that expression of totally different sets of genes was increased by hypertonicity in those cells with TonEBP vs. those without TonEBP activity. Of over 100 potentially new TonEBP-regulated genes, we selected seven for further analyses and found that their expressions were all dependent on TonEBP. RNA interference experiments showed that some of these genes, asporin, insulin-like growth factor-binding protein-5 and -7, and an extracellular lysophospholipase D, plus heat shock protein 70, a known TonEBP target gene, contributed to the adaptation to hypertonicity without promoting organic osmolyte accumulation. We conclude that TonEBP stimulates multiple cellular pathways for adaptation to hypertonic stress in addition to organic osmolyte accumulation.
authors.affiliation: Department of Medicine, University of Maryland, Baltimore, Maryland. USA; Department of Physiology, Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Sang Do
authors.initials: SD
authors.lastname: Lee
authors.forename: Soo Youn
authors.initials: SY
authors.lastname: Choi
authors.forename: Sun Woo
authors.initials: SW
authors.lastname: Lim
authors.forename: S Todd
authors.initials: ST
authors.lastname: Lamitina
authors.forename: Steffan N
authors.initials: SN
authors.lastname: Ho
authors.forename: William Y
authors.initials: WY
authors.lastname: Go
authors.forename: H Moo
authors.initials: HM
authors.lastname: Kwon
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006982:Hypertonic Solutions / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D009995:Osmosis / Q000502:physiology*; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D006982:Hypertonic Solutions; C492200:Nfat5 protein, mouse; D014157:Transcription Factors