Purification, Identification, and Characterization of an Osmotic Response Element Binding Protein

doi:10.1006/bbrc.2000.2376

Biochemical and Biophysical Research Communications

Volume 270, Issue 1, 2 April 2000, Pages 52-61

https://doi.org/10.1006/bbrc.2000.2376 Get rights and content

Abstract

Kidney cells, especially the epithelial cells lining the collecting tubules in the inner medulla, are constantly exposed to concentrated urine. They are protected from the osmotic effect of high levels of sodium ion and urea by accumulating compatible osmolytes such as sorbitol, betaine, and myo-inositol. These osmolytes are involved in maintaining cell volume and electrolyte contents because they do not perturb the protein structure and function over a wide range of concentrations. Sorbitol is produced via the reduction of glucose by aldose reductase (AR), while betaine and myo-inositol are transported into the cells through specific transporters. Under hyperosmotic stress, transcriptions of genes encoding these proteins are highly induced. The induction of transcription was found to be mediated through the osmotic response elements (OREs) located in the 5′ flanking sequences of these genes. We had earlier identified the OREs in human AR gene. In this study we purified and identified the osmotic response element binding protein (OREBP). OREBP is a transcription factor of approximately 200 kDa in size, characterized by a Rel-like DNA binding domain and a glutamine-rich transactivation domain. Dominant negative OREBP significantly diminished hyperosmotic AR gene induction. Immunohistochemical analysis showed that this transcription factor is rapidly translocated into the nucleus upon hyperosmotic stress.

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Citation Excerpt :
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^☆: This work was supported by Research Grant Council Grant HKU7278/97M.

^☆☆: Abbreviations used: AR, aldose reductase; BGT1, betaine/γ-aminobutyric acid transporter; SMIT, Na⁺-dependent myo-inositol transporter; OREs, osmotic response elements; NFAT, nuclear factor of activated T cells; TonE, tonicity-responsive enhancer; OREBP, osmotic response element binding protein

²: To whom correspondence should be addressed. Fax: 852-28171006. E-mail: [email protected].

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Regular ArticlePurification, Identification, and Characterization of an Osmotic Response Element Binding Protein☆,☆☆

Abstract

Brain Res. Mol. Brain Res.

Cell

Curr. Opin. Cell Biol.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Cell

J. Biol. Chem.

Renal medullary organic osmolytes

Physiol. Rev.

Living with water stress: Evolution of osmolyte systems

Science

Molecular basis of osmotic regulation

Am. J. Physiol.

Regulation of gene expression by hypertonicity

Annu. Rev. Physiol.

Renal osmoregulatory transport of compatible organic osmolytes

Curr. Opin. Nephrol. Hypertens.

Osmoregulation in the mammalian kidney: The role of organic osmolytes

J. Exp. Zool.

Cell volume regulation in the nephron

Annu. Rev. Physiol.

Regulation of mammalian brain cell volume

J. Exp. Zool.

Regular Article
Purification, Identification, and Characterization of an Osmotic Response Element Binding Protein☆,☆☆