PKC-α contributes to high NaCl-induced activation of NFAT5 (TonEBP/OREBP) through MAPK ERK1/2

Hong Wang, Joan D. Ferraris, Janet D. Klein, Jeff M. Sands, Maurice B. Burg, Xiaoming Zhou*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

High NaCl in the renal medullary interstitial fluid powers the concentration of urine but can damage cells. The transcription factor nuclear factor of activated T cells 5 (NFAT5) activates the expression of osmoprotective genes. We studied whether PKC-α contributes to the activation of NFAT 5. PKC-α protein abundance was greater in the renal medulla than in the cortex. Knockout of PKC-α reduced NFAT5 protein abundance and expression of its target genes in the inner medulla. In human embryonic kidney (HEK)-293 cells, high NaCl increased PKC-α activity, and small interfering RNA-mediated knockdown of PKC-α attenuated high NaCl-induced NFAT5 transcriptional activity. Expression of ERK1/2 protein and phosphorylation of ERK1/2 were higher in the renal inner medulla than in the cortex. Knockout of PKC-α decreased ERK1/2 phosphorylation in the inner medulla, as did knockdown of PKC-α in HEK-293 cells. Also, knockdown of ERK2 reduced high NaCl-dependent NFAT5 transcriptional activity in HEK-293 cells. Combined knockdown of PKC-α and ERK2 had no greater effect than knockdown of either alone. Knockdown of either PKC-α or ERK2 reduced the high NaCl-induced increase of NFAT5 transactivating activity. We have previously found that the high NaCl-induced increase of phosphorylation of Ser591 on Src homology 2 domaincontaining phosphatase 1 (SHP-1-S591-P) contributes to the activation of NFAT5 in cell culture, and here we found high levels of SHP-1-S591-P in the inner medulla. PKC-α has been previously shown to increase SHP-1-S591-P, which raised the possibility that PKC-α might be acting through SHP- 1. However, we did not find that knockout of PKC-α in the renal medulla or knockdown in HEK-293 cells affected SHP-1-S591-P. We conclude that PKC-α contributes to high NaCl-dependent activation of NFAT5 through ERK1/2 but not through SHP-1-S591.

Original languageEnglish
Pages (from-to)F140-F148
JournalAmerican Journal of Physiology - Renal Physiology
Volume308
Issue number2
DOIs
StatePublished - 15 Jan 2015
Externally publishedYes

Keywords

  • Hypertonicity
  • Inner medulla
  • Nuclear factor of activated T cells 5
  • Osmotic response element-binding protein
  • Serine-591-phosphorylated Src homology 2 domaincontaining phosphatase 1
  • Src homology 2 domain-containing phosphatase 1
  • Tonicity-responsive enhancer-binding protein
  • Urinary concentration

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