Regulation of ceruloplasmin in human hepatic cells by redox active copper: Identification of a novel AP-1 site in the ceruloplasmin gene

Dola Das, Nisha Tapryal, Shyamal K. Goswami, Paul L. Fox, Chinmay K. Mukhopadhyay

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

Cp (ceruloplasmin), a copper containing plasma protein, mainly synthesized in the liver, is known to be functional between the interface of iron and copper metabolism. We have reported previously that Cp is regulated by cellular iron status, but the process of the regulation of Cp by copper still remains a subject for investigation. In the present paper, we show that PDTC (pyrrolidine dithiocarbamate), a thiol compound widely known to increase intracellular redox copper, regulates Cp expression in hepatic cells by a copper-dependent transcriptional mechanism. To find out the mechanism of induction, chimeric constructs of the Cp 5′-flanking region driving luciferase were transfected into human hepatic cells. Deletion and mutational analyses showed the requirement of a novel APRE [AP-1 (activator protein-1) responsive element] present about 3.7 kb upstream of the translation initiation site. The role of AP-1 was confirmed by electrophoretic mobility-shift analysis. Western blot and overexpression studies detected the AP-1 as a heterodimer of c-jun and c-fos proteins. The activation of AP-1 was found to be copper-dependent as a specific extracellular chelator bathocuproine disulfonic acid blocked PDTC-mediated induction of AP-1-DNA binding and increased reporter gene activity. Whereas, in a copper-free medium, PDTC failed to activate either AP-1 or Cp synthesis, supplementation of copper could reverse AP-1 activation and Cp synthesis. Our finding is not only the first demonstration of regulation of Cp by redox copper but may also explain previous findings of increased Cp expression in cancers like hepatocarcinoma, where the intracellular copper level is higher in a redox compromised environment.

Original languageEnglish (US)
Pages (from-to)135-141
Number of pages7
JournalBiochemical Journal
Volume402
Issue number1
DOIs
StatePublished - Feb 15 2007

Keywords

  • Activator protein-1 (AP-1)
  • Ceruloplasmin
  • Copper
  • Gene regulation
  • Luciferase
  • Transcription

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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