Nuclear export of phosphorylated C/EBPbeta mediates the inhibition of albumin expression by TNF-alpha.
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.
Buck
M
M
Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA. mbuck@vapop.ucsd.edu
Zhang
L
L
Halasz
N A
NA
Hunter
T
T
Chojkier
M
M
D021581:Active Transport, Cell Nucleus; D000368:Aged; D000409:Alanine / Q000737:chemistry; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D016466:CHO Cells; D002100:Cachexia; D016022:Case-Control Studies; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000166:cytology; D008297:Male; D051379:Mice; D008875:Middle Aged; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000378:metabolism; D009154:Mutation; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012694:Serine / Q000378:metabolism; D012709:Serum Albumin / Q000096:biosynthesis*; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D000975:Antioxidants; D022782:CCAAT-Enhancer-Binding Protein-beta; D005231:Fatty Acids, Unsaturated; D008070:Lipopolysaccharides; D020030:Nitric Oxide Donors; D012709:Serum Albumin; D014409:Tumor Necrosis Factor-alpha; D012694:Serine; C002385:linsidomine; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D000409:Alanine; C038753:leptomycin B