Project description:Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular Ago2, a core microRNA, remain elusive. We elucidated the function and mechanism of subcellular localized Ago2 on mouse models for diabetes mellitus and diabetic cardiomyopathy. Ago2 decreased in cardiomyocyte mitochondria in both models. Overexpression of mitochondrial Ago2 attenuated diabetes-induced cardiac dysfunction. Ago2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain (ETC) subunits and decrease reactive oxygen species. Malonylation, a post-translational modification of Ago2, reduced the importing of Ago2 into mitochondria in diabetic cardiomyopathy. Ago2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function. Our results reveal that the SIRT3–Ago2–CYTB axis links glucotoxicity to cardiac ETC imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.
Project description:Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular Ago2, a core microRNA, remain elusive. We elucidated the function and mechanism of subcellular localized Ago2 on mouse models for diabetes mellitus and diabetic cardiomyopathy. Ago2 decreased in cardiomyocyte mitochondria in both models. Overexpression of mitochondrial Ago2 attenuated diabetes-induced cardiac dysfunction. Ago2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain (ETC) subunits and decrease reactive oxygen species. Malonylation, a post-translational modification of Ago2, reduced the importing of Ago2 into mitochondria in diabetic cardiomyopathy. Ago2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function. Our results reveal that the SIRT3–Ago2–CYTB axis links glucotoxicity to cardiac ETC imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.
Project description:Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular Ago2, a core microRNA, remain elusive. We elucidated the function and mechanism of subcellular localized Ago2 on mouse models for diabetes mellitus and diabetic cardiomyopathy. Ago2 decreased in cardiomyocyte mitochondria in both models. Overexpression of mitochondrial Ago2 attenuated diabetes-induced cardiac dysfunction. Ago2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain (ETC) subunits and decrease reactive oxygen species. Malonylation, a post-translational modification of Ago2, reduced the importing of Ago2 into mitochondria in diabetic cardiomyopathy. Ago2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function. Our results reveal that the SIRT3–Ago2–CYTB axis links glucotoxicity to cardiac ETC imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.
Project description:Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular Ago2, a core microRNA, remain elusive. We elucidated the function and mechanism of subcellular localized Ago2 on mouse models for diabetes mellitus and diabetic cardiomyopathy. Ago2 decreased in cardiomyocyte mitochondria in both models. Overexpression of mitochondrial Ago2 attenuated diabetes-induced cardiac dysfunction. Ago2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain (ETC) subunits and decrease reactive oxygen species. Malonylation, a post-translational modification of Ago2, reduced the importing of Ago2 into mitochondria in diabetic cardiomyopathy. Ago2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function. Our results reveal that the SIRT3–Ago2–CYTB axis links glucotoxicity to cardiac ETC imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.
Project description:Electron transport chain (ETC) biogenesis is tightly coupled to energy levels and availability of ETC subunits. Coenzyme Q: cytochrome c oxidoreductase (complex III or CIII) occupies a central position in the ETC, receiving electrons from diverse fuel sources to control the ubiquinol:ubiquinone (CoQH2/CoQ) ratio. As such, CIII is an attractive node for controlling ETC biogenesis during metabolic stress. Here, we report the discovery of mammalian CoOrdinator of Mitochondrial CYTB or “COM” complexes that regulate CIII biogenesis in a step-wise fashion in response to nutrient and nuclear-encoded ETC subunit availability. The COMA complex, consisting of UQCC1/2 and the membrane anchor C16ORF91 (UQCC4), facilitates the translation of CIII enzymatic core subunit CYTB. Subsequently, microproteins SMIM4 and BRAWNIN, together with COMA subunits form the COMB complex that stabilizes nascent CYTB. Finally, UQCC3-containing COMC promotes CTYB maturation and association with downstream CIII subunits. This stepwise assembly enables cells to adapt to metabolic stress by increasing CIII biogenesis and inducing an integrated stress response when challenged. Furthermore, when nuclear CIII subunits are unavailable for assembly, COMB is required to chaperone nascent CYTB to prevent OXPHOS collapse. Our studies highlight CYTB synthesis as a key regulatory node of ETC biogenesis, and uncover the roles of mito-SEPs in mitochondrial homeostasis during energy stress.
Project description:The existence of most peptide segments of CYTB-187AA to high confidence in five cell lines using mass spectrometry and the identification of CYTB-187AA interacting proteins.
Project description:Mitochondrial mRNAs encode key subunits of the oxidative phosphorylation complexes that produce energy for the cell. In Saccharomyces cerevisiae, mitochondrial translation is under the control of translational activators, specific to each mRNA. In Schizosaccharomyces pombe, which more closely resembles the human system by its mitochondrial DNA structure and physiology, most translational activators appear to be either lacking, or recruited for post-translational functions. By combining bioinformatics, genetic and biochemical approaches we identified two interacting factors, Cbp7 and Cbp8, controlling Cytb production in S. pombe. We show that their absence affects cytb mRNA stability and decreases the accumulation of the Cytb protein. We further identified two classes of Cbp7/Cbp8 partners and showed that they modulated Cytb or Cox1 synthesis. First, two isoforms of bS1m small mitoribosomal subunits, that appear mutually exclusive and confer translational specificity. Second, a complex of four proteins dedicated to Cox1 synthesis, which includes an RNA helicase that interacts with the mitochondrial ribosome. Our results suggest that S. pombecontains, in addition to complexes of translational activators, a heterogeneous population of mitochondrial ribosomes that could specifically modulate translation depending on the mRNA translated, in order to optimally balance the production of different respiratory complex subunits.