Inositol plays an important role in protecting cells from hypertonic stress. The renal medulla is normally hypertonic; the degree of hypertonicity changes depending on hydration status. In certain pathologic states all tissues experience hypertonicity and adapt to the adverse environment using mechanisms similar to those of the renal medulla. Regulation of the sodium/inositol cotransporter is critical in osmo-protective accumulation of inositol in renal epithelial cells, brain, and eyes. When cells are exposed to a hypertonic environment, transcription of the gene coding for the cotransporter is markedly stimulated resulting in increased activity of the cotransporter and cellular accumulation of inositol. Tonicity-responsive enhancers involved in the hypertonicity- induced stimulation of the transcription of the cotransporter gene are spread over a wide region upstream of the gene. We hypothesize that there are special structural features in the chromatin that allow all the enhancers to interact with the promoter. To test this directly we will first prepare a 100 kb genomic DNA fragment containing the cotransporter locus - the entire gene and 60 kb of flanking sequence containing all the enhancers. Taking advantage of yeast genetic methods, variations of the locus will be prepared by selectively deleting the enhancers and changing their location. Wildtype and variant locus DNA will be introduced into cells and regulation of the gene will be studied to assess the effects of the changes. Information obtained will provide novel insight into the role of long-range interactions of the chromatin in gene regulation. The role of a transcription factor that specifically interacts with tonicity-responsive enhancers will be studied in animals. Transgenic mouse lines expressing the dominant negative form of the transcription factor will be generated. We will examine whether the renal medullas of these animals are injured as expected due to the lack of adaptation to hypertonicity. To explore the role of this transcription factor further, mouse lines deficient in the transcription factor will be generated using the gene targeting technique. Phenotypes of these animals will be scrutinized. This work will enhance knowledge regarding how cells adapt to the hypertonic stress.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
7R01DK042479-14
Application #
6634962
Study Section
General Medicine B Study Section (GMB)
Program Officer
Ketchum, Christian J
Project Start
1990-07-01
Project End
2005-03-31
Budget Start
2003-07-01
Budget End
2005-03-31
Support Year
14
Fiscal Year
2003
Total Cost
$345,937
Indirect Cost
Name
University of Maryland Baltimore
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Yoon, Hyung-Ju; You, Sungyong; Yoo, Seung-Ah et al. (2011) NFAT5 is a critical regulator of inflammatory arthritis. Arthritis Rheum :
Roth, Isabelle; Leroy, Valérie; Kwon, H Moo et al. (2010) Osmoprotective transcription factor NFAT5/TonEBP modulates nuclear factor-kappaB activity. Mol Biol Cell 21:3459-74
Sheen, Mee R; Kim, Jeong-Ah; Lim, Sun W et al. (2009) Interstitial tonicity controls TonEBP expression in the renal medulla. Kidney Int 75:518-25
Kwon, Min Seong; Na, Ki Young; Moeckel, Gilbert et al. (2009) Urea promotes TonEBP expression and cellular adaptation in extreme hypertonicity. Pflugers Arch 459:183-9
Kwon, Min Seong; Lim, Sun Woo; Kwon, H Moo (2009) Hypertonic stress in the kidney: a necessary evil. Physiology (Bethesda) 24:186-91
Kim, Jeong-Ah; Sheen, Mee Rie; Lee, Sang Do et al. (2009) Hypertonicity stimulates PGE2 signaling in the renal medulla by promoting EP3 and EP4 receptor expression. Kidney Int 75:278-84
Kwon, H Moo (2008) Protein misfolding in hypertonic stress: new insights into an old idea. Focus on ""genome-wide RNAi screen and in vivo protein aggregation reporters identify degradation of damaged protein as an essential hypertonic stress response"". Am J Physiol Cell Physiol 295:C1474-5
Hasler, Udo; Leroy, Valerie; Jeon, Un Sil et al. (2008) NF-kappaB modulates aquaporin-2 transcription in renal collecting duct principal cells. J Biol Chem 283:28095-105
Navarro, Paola; Chiong, Mario; Volkwein, Karen et al. (2008) Osmotically-induced genes are controlled by the transcription factor TonEBP in cultured cardiomyocytes. Biochem Biophys Res Commun 372:326-30
Kim, Jeong Ah; Jeon, Un Sil; Kwon, Min Seong et al. (2007) Transcriptional activator TonE-binding protein in cellular protection and differentiation. Methods Enzymol 428:253-67

Showing the most recent 10 out of 46 publications