A common regulatory locus affects both HNF4/HNF1alpha pathway activation and sensitivity to LPS-mediated apoptosis in rat hepatoma cells.
Lipopolysaccharide (LPS) has been shown to protect certain cultured mammalian cells from undergoing programmed cell death (apoptosis) when exposed to tumor necrosis factor (TNF). However, LPS has also been reported to induce apoptosis in cultured endothelial cells, suggesting that apoptotic response mechanisms may be dependent upon cell type. In order to understand the influence of tissue-specific gene expression on apoptosis, we compared LPS-induced apoptosis in hepatoma cells with dedifferentiated hepatoma variant cells that have been selected for the loss of the liver-enriched HNF4/HNF1alpha transcriptional activation pathway. We report here that while human, rat and mouse hepatoma cell lines are resistant to LPS-mediated cell death, the HNF4-/HNF1alpha- rat hepatoma variant cells undergo rapid apoptosis (as determined by morphological analysis, DNA laddering and the TUNEL assay) upon exposure to LPS. Genetic rescue experiments show that restoration of the HNF4/HNF1alpha pathway via chromosome transfer render the hepatoma variant cells resistant to LPS-mediated apoptosis. However, the introduction of HNF1alpha alone failed to alter the apoptotic phenotype, suggesting that the defect(s) in the hepatoma variant cells that influence apoptotic responses lies upstream of HNF4/HNF1alpha expression. This study provides for the first time direct evidence of a common regulatory locus involved in activation of hepatic gene expression and sensitivity to LPS-mediated apoptosis.
Pediatric Research Institute, St Louis University Health Sciences Center, and Cardinal Glennon Children's Hospital, Pediatric Research Institute, St Louis, MO 63110, USA. bullaga@slu.ed
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Bulla
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Givens
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Brown
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Oladiran
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Kraus
D000818:Animals; D017209:Apoptosis; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D006528:Carcinoma, Hepatocellular; D004268:DNA-Binding Proteins; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008113:Liver Neoplasms; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000235:genetics*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D051557:Hepatocyte Nuclear Factor 4; C496489:Hnf1a protein, rat; D008070:Lipopolysaccharides; C403128:MLX protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; C501970:Tcfl4 protein, mouse; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta