Inhibition of NaCl-induced heat shock protein 72 expression renders MDCK cells susceptible to high urea concentrations

Neuhofer, Wolfgang; Müller, Eva; Burger‐Kentischer, Anke; Fraek, Maria Luisa; Thurau, Klaus; Beck, Franz‐Xaver

doi:10.1007/s004240050824

Cited by 37 publications

(34 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…TonEBP may be involved in the HSP105B induction because in the 5Ј flanking region (GenBank accession number for human gene, NT_031889) there are two sites that fit the consensus of TonEBP binding sites. As discussed earlier, the increased HSP70 expression protects cells from apoptosis caused by high concentrations of urea in the renal medulla (36,37,41). HSP70 inhibits the mitochondrial pathway of apoptosis at multiple steps.…”

Section: Discussionmentioning

confidence: 74%

“…A number of experiments have demonstrated that cell survival under a high level of urea increases dramatically as a function of HSP70 expression. Increased expression of HSP70 by treatment with hypertonicity (41) or by stable transfection of HSP70 cDNA (37) promotes cell survival in the presence of a high level of urea, while forced down regulation of HSP70 by using antisense nucleotides (36) renders cells more susceptible to death by urea. In this study, we demonstrate that a major form of heat-inducible HSP70, named HSP70-2, is stimulated by hypertonicity by virtue of TonEBP binding to the 5Ј flanking region.…”

mentioning

confidence: 99%

See 1 more Smart Citation

TonEBP/NFAT5 Stimulates Transcription of HSP70 in Response to Hypertonicity

Woo

Lee

et al. 2002

Molecular and Cellular Biology

184

155

View full text Add to dashboard Cite

While hyperosmolality of the kidney medulla is essential for urinary concentration, it imposes a great deal of stress. Cells in the renal medulla adapt to the stress of hypertonicity (hyperosmotic salt) by accumulating organic osmolytes. Tonicity-responsive enhancer (TonE) binding protein (TonEBP) (or NFAT5) stimulates transcription of transporters and a synthetic enzyme for the cellular accumulation of organic osmolytes. We found that dominant-negative TonEBP reduced expression of HSP70 as well as the transporters and enzyme. Near the major histocompatibility complex class III locus, there are three HSP70 genes named HSP70-1, HSP70-2, and HSC70t. While HSP70-1 and HSP70-2 were heat inducible, only HSP70-2 was induced by hypertonicity. In the 5 flanking region of the HSP70-2 gene, there are three sites for TonEBP binding. In cells transfected with a reporter plasmid containing this region, expression of luciferase was markedly stimulated in response to hypertonicity. Coexpression of the dominant-negative TonEBP reduced the luciferase expression. Mutating all three sites in the reporter plasmid led to a complete loss of induction by hypertonicity. Thus, TonEBP rather than heat shock factor stimulates transcription of the HSP70-2 gene in response to hypertonicity. We conclude that TonEBP is a master regulator of the renal medulla for cellular protection against high osmolality via organic osmolytes and molecular chaperones.

show abstract

Section: Discussionmentioning

confidence: 74%

mentioning

confidence: 99%

TonEBP/NFAT5 Stimulates Transcription of HSP70 in Response to Hypertonicity

Woo

Lee

et al. 2002

Molecular and Cellular Biology

184

155

View full text Add to dashboard Cite

show abstract

“…as the ␥-subunit of Na-K-ATPase (5) and heat shock proteins (16). The interest in our laboratory has been directed at understanding the role played in adaptation by this protein, a member of the FXYD family of small transmembrane proteins (23) that is exclusively expressed in the kidney (24).…”

Section: Discussionmentioning

confidence: 99%

Synthesis of the Na-K-ATPase γ-subunit is regulated at both the transcriptional and translational levels in IMCD3 cells

Capasso¹,

Rivard²,

Berl³

2005

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

We previously reported that hypertonicity-mediated upregulation of the ␥-subunit of Na-KATPase is dependent on both the JNK and the PI3 kinase pathways (Proc Natl Acad Sci USA 98: 13414, 2001). The present experiments were undertaken to explore the mechanisms whereby these pathways regulate the expression of the ␥-subunit in inner medullary collecting duct cells (IMCD3). Inhibition of JNK with SP-600125 (20 M), a concentration that causes an ϳ95% inhibition of hypertonicity-stimulated JNK activation, markedly decreased the amount of the ␥-subunit in response to 550 mosmol/kgH 2O for 48 h. This was accompanied by a parallel decrease in the ␥-subunit mRNA. The rate at which the ␥-subunit mRNA decreased was unaffected by actinomycin D. In contrast, inhibition of PI3 kinase with LY-294002 results in a marked decrease in the amount of ␥-subunit protein but without alteration in ␥-subunit message. The rate at which the ␥-subunit protein decreased was unaffected by cyclohexamide. Transfection of IMCD3 cells with a ␥-subunit construct results in the expression of both ␥-subunit message and protein. However, in cortical collecting duct cells (M1 cells) such transfection resulted in expression of only the message and not the protein. We conclude that JNK regulates the ␥-subunit at the transcriptional level while PI3 kinase regulates ␥-subunit expression at the translational level. There is also posttranscriptional cell specificity in the expression of the ␥ -subunit of Na-K-ATPase. osmoregulation; hypertonicity THE CELLS THAT INHABIT THE hypertonic environment of the inner medulla possess a number of adaptive mechanisms that allow them to survive this inhospitable environment. This survival is mediated initially by activation of ion transport systems (7) and thereafter by the cellular accumulation of a number of osmolytes (10). It has become increasingly evident that in addition to the proteins required for the cellular uptake and generation of these osmolytes, hypertonic stress brings about a coordinated response involving other proteins, many of which are critical to cell viability. Our laboratory has examined the role of the Na-K-ATPase with regard to the ␣-and ␤-subunits (6) and to the more recently described ␥-subunit (5). We have done so both in cultured cells and in rodents at various states of hydration (5, 6). These studies strongly suggest that synthesis of the ␥-subunit is important to cell survival when collecting duct cells are exposed to hypertonic stress (5). We have also demonstrated that ␥-subunit synthesis is linked to signaling pathways that are known to be activated by hypertonicity.More specifically, the generation of the ␥-subunits of Na-KATPase, but not the ␣-and ␤-subunits, is dependent on the activation of JNK (5). These experiments were performed with dominant-negative mutants of JNK that result in approximately a 50% decrement in JNK activation (27). Similarly, the pharmacological inhibition of PI3 kinase was found to significantly downregulate the expression of the ␥-subunit but not the other t...

show abstract

“…Although we observed some up-regulation of the ␥ under these acute conditions, it is evident that cells that survive the hypertonic stress continue to synthesize the protein as its expression is many-fold higher in the adapted cell lines. We surmise that this ongoing synthesis may be critical to the adaptive process because it distinguishes cells that are fully viable at very high tonicities (900 mosmol͞kgH 2 O) from those cells acutely exposed to osmolalities in excess of 550 mosmol͞kgH 2 O, which fail to survive despite full expression of enhanced osmolyte uptake (8,22), heat shock proteins (6,8), and the ␣ and ␤ subunits of Na-K-ATPase. It is also of interest that we observed the increase in the ␥ subunit only in cells exposed to NaCl and not to mannitol or urea substances that were also incompatible with the development of stably adapted cell lines (8).…”

Section: Discussionmentioning

confidence: 99%

The expression of the γ subunit of Na-K-ATPase is regulated by osmolality via C-terminal Jun kinase and phosphatidylinositol 3-kinase-dependent mechanisms

Capasso

Rivard

Berl

2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The ␣ and ␤ subunits of Na-K-ATPase are up-regulated by hypertonicity in inner-medullary collecting duct cells adapted to survive in hypertonic conditions. We examined the regulation of the ␥ subunit by hypertonicity. Although cultured inner-medullary collecting duct cells lacked the ␥ subunits, both variants ␥a and ␥b were expressed in cells adapted to 600 and 900 mosmol͞KgH2O. This expression was reversible with a half-time of 17.2 ؎ 0.5 h. The message of the ␥ subunit was absent in isotonic conditions and increased with higher tonicity in adapted cells. In acute experiments the appearance of the ␥ subunit was found to be both time-dependent (>24 h) and osmolality-dependent (>500 mosmol͞KgH2O). No induction was noted with urea and only minimal induction with mannitol. Increasing concentrations of the phosphatidylinositol 3-kinase inhibitor LY294002 resulted in a dose-dependent decrement in the expression of the ␥ subunit with total abolition at 10 M. This was associated with a decrease in cell viability as <20% survived the treatment with 10 M of LY294002. Neither inhibition of extracellular response kinase nor p38 mitogen-activated protein kinase inhibited osmotic induction of the ␥ subunit. In contrast, cells transfected with a dominant negative c-Jun N-terminal kinase 2-APF construct displayed complete inhibition of the ␥ subunit. Such cells have accelerated loss of viability in hypertonic conditions. This study describes the regulation of the ␥ subunit of Na-K-ATPase by hypertonicity. This regulation is transcriptionally regulated and involves signaling mediated by phosphatidylinositol 3-kinase and c-Jun N-terminal kinase 2 pathways.

show abstract

Inhibition of NaCl-induced heat shock protein 72 expression renders MDCK cells susceptible to high urea concentrations

Cited by 37 publications

References 21 publications

TonEBP/NFAT5 Stimulates Transcription of HSP70 in Response to Hypertonicity

TonEBP/NFAT5 Stimulates Transcription of HSP70 in Response to Hypertonicity

Synthesis of the Na-K-ATPase γ-subunit is regulated at both the transcriptional and translational levels in IMCD3 cells

The expression of the γ subunit of Na-K-ATPase is regulated by osmolality via C-terminal Jun kinase and phosphatidylinositol 3-kinase-dependent mechanisms

Contact Info

Product

Resources

About