Degradation of Keap1 activates BH3-only proteins Bim and PUMA during hepatocyte lipoapoptosis
| Autor: | Xiang-Yang Wang, M Rahmani, D E Durrant, Masayuki Yamamoto, Huiping Zhou, Steven Grant, Sophie C. Cazanave, A J Sanyal, C D Klaassen |
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| Rok vydání: | 2014 |
| Předmět: |
Apoptosis
Mice Downregulation and upregulation Cell Line Tumor Proto-Oncogene Proteins hemic and lymphatic diseases Puma medicine Animals Humans Phosphorylation Molecular Biology Adaptor Proteins Signal Transducing Mice Knockout Original Paper Gene knockdown Kelch-Like ECH-Associated Protein 1 Bcl-2-Like Protein 11 biology Tumor Suppressor Proteins Autophagy Intracellular Signaling Peptides and Proteins Membrane Proteins Hep G2 Cells Cell Biology biology.organism_classification KEAP1 Molecular biology Cell biology Mice Inbred C57BL Cytoskeletal Proteins HEK293 Cells medicine.anatomical_structure Lipotoxicity Hepatocyte Hepatocytes biological phenomena cell phenomena and immunity Apoptosis Regulatory Proteins |
| Zdroj: | Cell Death & Differentiation. 21:1303-1312 |
| ISSN: | 1476-5403 1350-9047 |
| DOI: | 10.1038/cdd.2014.49 |
| Popis: | Non-alcoholic steatohepatitis is characterized by hepatic steatosis, elevated levels of circulating free fatty acids (FFA) and hepatocyte lipoapoptosis. This lipoapoptosis requires increased JNK phosphorylation and activation of the pro-apoptotic BH3-only proteins Bim and PUMA. Kelch-like ECH-associated protein (Keap)-1 is a BTB/Kelch protein that can regulate the expression of Bcl-2 protein and control apoptotic cell death. Yet, the role of Keap1 in hepatocyte lipotoxicity is unclear. Here we demonstrate that Keap1 protein was rapidly degraded in hepatocytes, through autophagy in a p62-dependent manner, in response to the toxic saturated FFA palmitate, but not following incubation with the non-toxic FFA oleic acid. Stable knockdown of Keap1 expression, using shRNA technology, in hepatocarcinoma cell lines induced spontaneous cell toxicity that was associated with JNK1-dependent upregulation of Bim and PUMA protein levels. Also, Keap1 knockdown further sensitized hepatocytes to lipoapoptosis by palmitate. Likewise, primary hepatocytes isolated from liver-specific Keap1(-/-) mice displayed higher Bim and PUMA protein levels and demonstrated increased sensitivity to palmitate-induced apoptosis than wild-type mouse hepatocytes. Finally, stable knockdown of Bim or PUMA expression prevented cell toxicity induced by loss of Keap1. These results implicate p62-dependent autophagic degradation of Keap1 by palmitate as a mechanism contributing to hepatocyte lipoapoptosis. |
| Databáze: | OpenAIRE |
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