Nuclear export of phosphorylated C/EBPbeta mediates the inhibition of albumin expression by TNF-alpha

EMBO J. 2001 Dec 3;20(23):6712-23. doi: 10.1093/emboj/20.23.6712.

Abstract

Decreased albumin expression is a frequent feature of cachexia patients afflicted with chronic diseases, including cancer, and a major contributor to their morbidity. Here we show that tumor necrosis-alpha (TNF-alpha) treatment of primary mouse hepatocytes or TNF-alpha overexpression in a mouse model of cachexia induces oxidative stress, nitric oxide synthase (NOS) expression and phosphorylation of C/EBPbeta on Ser239, within the nuclear localization signal, thus inducing its nuclear export, which inhibits transcription from the albumin gene. SIN-1, a NO donor, duplicated the TNF-alpha effects on hepatocytes. We found similar molecular abnormalities in the liver of patients with cancer-cachexia. The cytoplasmic localization and association of C/EBPbeta-PSer239 with CRM1 (exportin-1) in TNF-alpha-treated hepatocytes was inhibited by leptomycin B, a blocker of CRM1 activity. Hepatic cells expressing the non-phosphorylatable C/EBPbeta alanine mutant were refractory to the inhibitory effects of TNF-alpha on albumin transcription since the mutant remained localized to the nucleus. Treatment of TNF-alpha mice with antioxidants or NOS inhibitors prevented phosphorylation of C/EBPbeta on Ser239 and its nuclear export, and rescued the abnormal albumin gene expression.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Active Transport, Cell Nucleus
  • Aged
  • Alanine / chemistry
  • Animals
  • Antibiotics, Antineoplastic / pharmacology
  • Antioxidants / pharmacology
  • CCAAT-Enhancer-Binding Protein-beta / metabolism*
  • CHO Cells
  • Cachexia
  • Case-Control Studies
  • Cell Nucleus / metabolism
  • Cells, Cultured
  • Cricetinae
  • Cytoplasm / metabolism
  • Fatty Acids, Unsaturated / pharmacology
  • Hepatocytes / metabolism
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Lipopolysaccharides / pharmacology
  • Liver / cytology
  • Male
  • Mice
  • Middle Aged
  • Molsidomine / analogs & derivatives*
  • Molsidomine / metabolism
  • Mutation
  • Nitric Oxide Donors / pharmacology
  • Nitric Oxide Synthase / metabolism
  • Oxidative Stress
  • Phosphorylation
  • Precipitin Tests
  • Promoter Regions, Genetic
  • Protein Structure, Tertiary
  • Serine / metabolism
  • Serum Albumin / biosynthesis*
  • Time Factors
  • Transcription, Genetic
  • Transfection
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • Antibiotics, Antineoplastic
  • Antioxidants
  • CCAAT-Enhancer-Binding Protein-beta
  • Fatty Acids, Unsaturated
  • Lipopolysaccharides
  • Nitric Oxide Donors
  • Serum Albumin
  • Tumor Necrosis Factor-alpha
  • Serine
  • linsidomine
  • Molsidomine
  • Nitric Oxide Synthase
  • Alanine
  • leptomycin B