Mmu-miR-615-3p regulates lipoapoptosis by inhibiting C/EBP homologous protein

• Published in: PloS one Vol. 9; no. 10; p. e109637
• Main Authors: Miyamoto, Yasuhiro, Mauer, Amy S, Kumar, Swarup, Mott, Justin L, Malhi, Harmeet
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.10.2014; Public Library of Science (PLoS)
• Subjects: 3' Untranslated Regions; Animals; Apoptosis; Augmentation; Base Sequence; Binding Sites; Biology; Biology and life sciences; CCAAT/enhancer-binding protein; Cell death; Cell Line, Tumor; Cell lines; Cells, Cultured; Cellular stress response; CHOP protein; Endoplasmic reticulum; Fatty acids; Fatty liver; Gastroenterology; Gene Expression; Gene sequencing; Genomes; HEK293 Cells; Hepatology; Homology; Humans; Liver; Liver diseases; Male; Medicine and Health Sciences; Metabolism; Mice, Inbred C57BL; Mice, Knockout; MicroRNAs; MicroRNAs - physiology; Middle Aged; miRNA; Non-alcoholic Fatty Liver Disease - metabolism; Palmitic acid; Palmitic Acid - pharmacology; Physiology; Proteins; Reporter gene; Ribonucleic acid; RNA; RNA Interference; Rodents; Stress; Stresses; Transcription Factor CHOP - genetics; Transcription Factor CHOP - metabolism; Tunicamycin; United States > US; Minnesota
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0109637

Lipoapoptosis occurring due to an excess of saturated free fatty acids such as palmitate is a key pathogenic event in the initiation of nonalcoholic fatty liver disease. Palmitate loading of cells activates the endoplasmic reticulum stress response, including induction of the proapoptotic transcription factor C/EBP homologous protein (CHOP). Furthermore, the loss of microRNAs is implicated in regulating apoptosis under conditions of endoplasmic reticulum (ER) stress. The aim of this study was to identify specific microRNAs regulating CHOP expression during palmitate-induced ER stress. Five microRNAs were repressed under palmitate-induced endoplasmic reticulum stress conditions in hepatocyte cell lines (miR-92b-3p, miR-328-3p, miR-484, miR-574-5p, and miR-615-3p). We identified miR-615-3p as a candidate microRNA which was repressed by palmitate treatment and regulated CHOP protein expression, by RNA sequencing and in silico analyses, respectively. There is a single miR-615-3p binding site in the 3'untranslated region (UTR) of the Chop transcript. We characterized this as a functional binding site using a reporter gene-based assay. Augmentation of miR-615-3p levels, using a precursor molecule, repressed CHOP expression; and under these conditions palmitate- or tunicamycin-induced cell death were significantly reduced. Our results suggest that palmitate-induced apoptosis requires maximal expression of CHOP which is achieved via the downregulation of its repressive microRNA, miR-615-3p. We speculate that enhancement of miR-615-3p levels may be of therapeutic benefit by inhibiting palmitate-induced hepatocyte lipoapoptosis.