title: Mmu-miR-615-3p regulates lipoapoptosis by inhibiting C/EBP homologous protein.
abstract: 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.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Miyamoto
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Mauer
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Swarup
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
authors.forename: Justin L
authors.initials: JL
authors.lastname: Mott
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Harmeet
authors.initials: H
authors.lastname: Malhi
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000502:physiology*; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000378:metabolism; D019308:Palmitic Acid / Q000494:pharmacology; D034622:RNA Interference; D051742:Transcription Factor CHOP / Q000235:genetics* / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; C497250:Ddit3 protein, mouse; C000598775:MIRN615 microRNA, mouse; D035683:MicroRNAs; D051742:Transcription Factor CHOP; D019308:Palmitic Acid