Urea signalling to immediate-early gene transcription in renal medullary cells requires transactivation of the epidermal growth factor receptor

Hongyu Zhao, Wei Tian, Hongshi Xu, David M. Cohen

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Signalling by physiological levels of urea (e.g. 200 mM) in cells of the mammalian renal medulla is reminiscent of activation of a receptor tyrosine kinase. The epidermal growth factor (EGF) receptor may be transactivated by a variety of G-protein-coupled receptors, primarily through metalloproteinase-dependent cleavage of a membrane-anchored EGF precursor. In the murine inner medullary collecting duct (mIMCD3) cell line, urea (200 mM) induced prompt (1-5 min) tyrosine phosphorylation of the EGF receptor. Pharmacological inhibition of EGF receptor kinase activity with AG1478 or PD153035 blocked urea-inducible transcription and expression of the immediate-early gene, Egr-1. AG1478 blocked, either fully or partially, other hallmarks of urea signalling including Elk-1 activation and extracellular signal-regulated kinase phosphorylation. EGF receptor kinase inhibition also blocked the cytoprotective effect of urea observed in the context of hypertonicity-inducible apoptosis. EGF receptor transactivation was likely to be attributable to metalloproteinase-dependent ectodomain shedding of an EGF receptor agonist because both specific and non-specific inhibitors of metalloproteinases blocked the urea effect. Heparin-binding EGF (HB-EGF), in particular, was implicated because the diphtheria toxin analogue and highly specific antagonist of HB-EGF, CRM197, also blocked urea-inducible transcription. In aggregate, these data indicate that signalling in response to urea in renal medullary cells requires EGF receptor transactivation, probably through autocrine action of HB-EGF.

Original languageEnglish (US)
Pages (from-to)479-487
Number of pages9
JournalBiochemical Journal
Volume370
Issue number2
DOIs
StatePublished - Mar 1 2003

Keywords

  • Heparin-binding epidermal growth factor
  • Hypertonicity
  • Metalloproteinase

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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