Contribution of SHP-1 protein tyrosine phosphatase to osmotic regulation of the transcription factor TonEBP/OREBP

Xiaoming Zhou*, Morgan Gallazzini, Maurice B. Burg, Joan D. Ferraris

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Hypertonicity activates the transcription factor TonEBP/OREBP, resulting in increased expression of osmoprotective genes, including those responsible for accumulation of organic osmolytes and heat-shock proteins. Phosphorylation of TonEBP/OREBP contributes to its activation. Several of the kinases that are involved were previously identified, but the phosphatases were not. In the present studies we screened a genomewide human phosphatase siRNA library in human embryonic kidney (HEK)293 cells for effects on TonEBP/OREBP transcriptional activity. We found that siRNAs against 57 phosphatases significantly alter TonEBP/OREBP transcriptional activity during normotonicity (290 mosmol/kg) or hypertonicity (500 mosmol/kg, NaCl added) or both. Most siRNAs increase TonEBP/OREBP activity, implying that the targeted phosphatases normally reduce that activity. We further studied in detail SHP-1, whose knockdown by its specific siRNA increases TonEBP/OREBP transcriptional activity at 500 mosmol/kg. We confirmed that SHP-1 is inhibitory by overexpressing it, which reduces TonEBP/OREBP transcriptional activity at 500 mosmol/kg. SHP-1 dephosphorylates TonEBP/OREBP at a known regulatory site, Y143, both in vivo and in vitro. It inhibits TonEBP/OREBP by both reducing TonEBP/OREBP nuclear localization, which is Y143 dependent, and by lowering high NaCl-induced TonEBP/OREBP transactivating activity. SHP-1 coimmunoprecipitates with TonEBP/OREBP and vice versa, suggesting that they are physically associated in the cell. High NaCl inhibits the effect of SHP-1 on TonEBP/OREBP by increasing phosphorylation of SHP-1 on Ser591, which reduces its phosphatase activity and localization to the nucleus. Thus, TonEBP/OREBP is extensively regulated by phosphatases, including SHP-1, whose inhibition by high NaCl increases phosphorylation of TonEBP/OREBP at Y143, contributing to the nuclear localization and activation of TonEBP/OREBP.

Original languageEnglish
Pages (from-to)7072-7077
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number15
StatePublished - 13 Apr 2010
Externally publishedYes


  • Hypertonicity
  • NFAT5
  • Nuclear localization
  • Phosphorylation
  • siRNA library


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