Rottlerin inhibits tonicity-dependent expression and action of TonEBP in a PKCδ-independent fashion

Hongyu Zhao, Wei Tian, David Cohen

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Novel protein kinase C (PKC) isoforms PKCδ and PKCε have recently been implicated in signaling by hypertonic stress. We investigated the role of the putative PKCδ inhibitor rottlerin on tonicity-dependent gene regulation. In the renal medullary mIMCD3 cell line, rottlerin blocked tonicity-dependent transcription of a tonicity enhancer (TonE)-driven luciferase reporter gene, as well as tonicity-dependent transcription of the physiological tonicity effector gene aldose reductase, but not urea-dependent transcription. Consistent with these data, rottlerin inhibited tonicity-dependent expression of TonE binding protein (TonEBP) at the mRNA and protein levels. Another inhibitor of both novel and conventional PKC isoforms, GF-109203X, suppressed TonEBP-dependent transcription but failed to influence tonicity-inducible TonEBP expression. Global PKC downregulation with protracted phorbol ester treatment, however, failed to influence tonicity-dependent signaling, arguing against a PKCδ-dependent mechanism of rottlerin action in this model. In addition, hypertonic stress failed to induce phosphorylation of PKCδ. Furthermore, in a PC-12 cell model with a comparable degree of tonicity-dependent transcription, constitutive overexpression of dominant negative-acting PKCδ or PKCε effectively decreased tonicity signaling to extracellular signal-regulated kinase activation, as expected, but failed to influence TonE-dependent transcription. TonE-dependent transcription, however, remained rottlerin sensitive in this PC-12 cell model. In the aggregate, these data indicate that rottlerin dramatically inhibits tonicity-dependent TonEBP expression and TonE-dependent transcription but, despite its reputed mode of action, does so through a PKCδ-independent pathway.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Physiology
Volume282
Issue number4 51-4
StatePublished - 2002

Fingerprint

Protein Kinase C
Carrier Proteins
Osmotic Pressure
Protein Isoforms
rottlerin
Aldehyde Reductase
Protein C Inhibitor
Extracellular Signal-Regulated MAP Kinases
Phorbol Esters
Protein Kinase Inhibitors
Luciferases
Reporter Genes
Genes
Urea
Down-Regulation
Phosphorylation
Kidney
Cell Line
Messenger RNA

Keywords

  • Hypertonicity
  • Inner medullary collecting duct
  • Kidney
  • Renal
  • Signal transduction

ASJC Scopus subject areas

  • Physiology

Cite this

Rottlerin inhibits tonicity-dependent expression and action of TonEBP in a PKCδ-independent fashion. / Zhao, Hongyu; Tian, Wei; Cohen, David.

In: American Journal of Physiology - Renal Physiology, Vol. 282, No. 4 51-4, 2002.

Research output: Contribution to journalArticle

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AB - Novel protein kinase C (PKC) isoforms PKCδ and PKCε have recently been implicated in signaling by hypertonic stress. We investigated the role of the putative PKCδ inhibitor rottlerin on tonicity-dependent gene regulation. In the renal medullary mIMCD3 cell line, rottlerin blocked tonicity-dependent transcription of a tonicity enhancer (TonE)-driven luciferase reporter gene, as well as tonicity-dependent transcription of the physiological tonicity effector gene aldose reductase, but not urea-dependent transcription. Consistent with these data, rottlerin inhibited tonicity-dependent expression of TonE binding protein (TonEBP) at the mRNA and protein levels. Another inhibitor of both novel and conventional PKC isoforms, GF-109203X, suppressed TonEBP-dependent transcription but failed to influence tonicity-inducible TonEBP expression. Global PKC downregulation with protracted phorbol ester treatment, however, failed to influence tonicity-dependent signaling, arguing against a PKCδ-dependent mechanism of rottlerin action in this model. In addition, hypertonic stress failed to induce phosphorylation of PKCδ. Furthermore, in a PC-12 cell model with a comparable degree of tonicity-dependent transcription, constitutive overexpression of dominant negative-acting PKCδ or PKCε effectively decreased tonicity signaling to extracellular signal-regulated kinase activation, as expected, but failed to influence TonE-dependent transcription. TonE-dependent transcription, however, remained rottlerin sensitive in this PC-12 cell model. In the aggregate, these data indicate that rottlerin dramatically inhibits tonicity-dependent TonEBP expression and TonE-dependent transcription but, despite its reputed mode of action, does so through a PKCδ-independent pathway.

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