Publicação
Role of sirtuin 3 on mitochondrial dynamics in Huntington's disease striatal cells
| Resumo: | Altered mitochondrial dynamics has been implicated in the pathogenesis of several neurodegenerative disorders, including Huntington’s disease (HD). Sirtuins, NAD+-dependent lysine deacetylases, have emerged as important cellular targets that can interfere with mitochondrial biogenesis, fission/fusion, motility and mitophagy. Among them, sirtuin 3 (SIRT3) is particularly relevant, being the main deacetylase located in mitochondria. Here we evaluated the influence of SIRT3 on mitochondrial dynamics using striatal cells derived from HD knock-in mice (STHdhQ111/Q111) versus wild-type cells (STHdhQ7/Q7). Increased mitochondrial fragmentation was observed in untransfected HD cells. Indeed, STHdhQ111/Q111 cells exhibited an overall decrease in the levels of mitochondrial fusion proteins (Mfn2, OPA1) and an increase in fission-related Fis1. Drp1 (also involved in mitochondrial fission) was preferentially accumulated in the mitochondrial fraction of HD cells. Increased LC3-II/I ratio, which evaluates autophagosome formation, was observed in STHdhQ111/Q111 cells. Moreover, the autophagy adaptor p62 was found to be decreased in mutant cells. Parkin and PINK1, two markers of mitophagy, were also assessed. Untransfected HD cells exhibited lower levels of both proteins. No significant changes were detected in phosphorylated Parkin (required for its enzymatic activation and mitochondrial translocation). These data suggest that PINK1/Parkin-dependent mitophagy is impaired in HD striatal cells. Overexpression (OE) of SIRT3 reduced the unbalance between fission/fusion by decreasing the protein levels of Fis1 in STHdhQ7/Q7 and STHdhQ111/Q111 cells, and Drp1 accumulation in mitochondria in STHdhQ111/Q111 cells. Concordantly, an increased number of mutant cells presenting tubular mitochondria was observed after SIRT3OE. An additional significant increase in LC3-II/I ratio was observed in STHdhQ111/Q111-SIRT3 cells, indicative of macroautophagy activation. Data suggest that enhanced SIRT3 levels restore mitochondrial morphology in mutant cells by reducing mitochondrial fission, with additional activation of macroautophagy.1 |
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| Autores principais: | Carmo, Catarina Sofia Rodrigues do |
| Assunto: | Huntington’s disease Mitochondrial dysfunction Mitochondrial dynamics Fission / fusion balance Mitophagy Sirtuin 3 |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Altered mitochondrial dynamics has been implicated in the pathogenesis of several neurodegenerative disorders, including Huntington’s disease (HD). Sirtuins, NAD+-dependent lysine deacetylases, have emerged as important cellular targets that can interfere with mitochondrial biogenesis, fission/fusion, motility and mitophagy. Among them, sirtuin 3 (SIRT3) is particularly relevant, being the main deacetylase located in mitochondria. Here we evaluated the influence of SIRT3 on mitochondrial dynamics using striatal cells derived from HD knock-in mice (STHdhQ111/Q111) versus wild-type cells (STHdhQ7/Q7). Increased mitochondrial fragmentation was observed in untransfected HD cells. Indeed, STHdhQ111/Q111 cells exhibited an overall decrease in the levels of mitochondrial fusion proteins (Mfn2, OPA1) and an increase in fission-related Fis1. Drp1 (also involved in mitochondrial fission) was preferentially accumulated in the mitochondrial fraction of HD cells. Increased LC3-II/I ratio, which evaluates autophagosome formation, was observed in STHdhQ111/Q111 cells. Moreover, the autophagy adaptor p62 was found to be decreased in mutant cells. Parkin and PINK1, two markers of mitophagy, were also assessed. Untransfected HD cells exhibited lower levels of both proteins. No significant changes were detected in phosphorylated Parkin (required for its enzymatic activation and mitochondrial translocation). These data suggest that PINK1/Parkin-dependent mitophagy is impaired in HD striatal cells. Overexpression (OE) of SIRT3 reduced the unbalance between fission/fusion by decreasing the protein levels of Fis1 in STHdhQ7/Q7 and STHdhQ111/Q111 cells, and Drp1 accumulation in mitochondria in STHdhQ111/Q111 cells. Concordantly, an increased number of mutant cells presenting tubular mitochondria was observed after SIRT3OE. An additional significant increase in LC3-II/I ratio was observed in STHdhQ111/Q111-SIRT3 cells, indicative of macroautophagy activation. Data suggest that enhanced SIRT3 levels restore mitochondrial morphology in mutant cells by reducing mitochondrial fission, with additional activation of macroautophagy.1 |
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