title: Up-regulation of the mitochondrial malate dehydrogenase by oxidative stress is mediated by miR-743a.
abstract: These experiments reveal for the first time that microRNAs (miRNAs) mediate oxidant regulated expression of a mitochondrial tricarboxylic acid cycle gene (mdh2). mdh2 encoded malate dehydrogenase (MDH) is elevated by an unknown mechanism in brains of patients that died with Alzheimer's disease. Oxidative stress, an early and pervasive event in Alzheimer's disease, increased MDH activity and mRNA level of mdh2 by 19% and 22%, respectively, in a mouse hippocampal cell line (HT22). Post-transcriptional events underlie the change in mRNA because actinomycin D did not block the elevated mdh2 mRNA. Since miRNAs regulate gene expression post-transcriptionally, the expression of miR-743a, a miRNA predicted to target mdh2, was determined and showed a 52% reduction after oxidant treatment. Direct interaction of miR-743a with mdh2 was demonstrated with a luciferase based assay. Over-expression or inhibition of miR-743a led to a respective reduction or increase in endogenous mRNA and MDH activity. The results demonstrate that miR-743a negatively regulates mdh2 at post-transcriptional level by directly targeting the mdh2 3'UTR. The findings are consistent with the suggestion that oxidative stress can elevate the activity of MDH through miR-743a, and provide new insights into possible roles of miRNA in oxidative stress and neurodegeneration.
authors.affiliation: Department of Neurology & Neuroscience, Weill Cornell Medical College/Burke Medical Research Institute, White Plains, New York, USA. qis2002@med.cornell.edu
authors.forename: Qingli
authors.initials: Q
authors.lastname: Shi
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gibson
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D018390:Gene Targeting; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology; D006861:Hydrogen Peroxide / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000096:biosynthesis* / Q000378:metabolism; D051379:Mice; D057507:Mice, 129 Strain; D035683:MicroRNAs / Q000494:pharmacology*; D008928:Mitochondria / Q000201:enzymology*; D018384:Oxidative Stress / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation
chemical_list: D020413:3' Untranslated Regions; D035683:MicroRNAs; C560968:Mirn743 microRNA, mouse; D006861:Hydrogen Peroxide; D008291:Malate Dehydrogenase; D008156:Luciferases