Xrn1 Modulates Mitochondrial NAD Levels through NAD-Capped RNA Decay
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Q Exactive HF
ORGANISM(S): Saccharomyces Cerevisiae (ncbitaxon:4932)
SUBMITTER: 
Megerditch Kiledjian
PROVIDER: MSV000087605 | MassIVE | Thu Jun 10 12:10:00 BST 2021
REPOSITORIES: MassIVE
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Project description:Cockayne syndrome (CS) is a rare premature aging disease, which in the majority of cases is caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and die by 12 years of age on average. The CS proteins are involved in transcription and DNA repair, including a specialized form of DNA repair called transcription-coupled nucleotide excision repair (TC-NER). However, there is also evidence for mitochondrial dysfunction in CS, likely contributing to the severe premature aging phenotype of this disease. Our cross-species transciptomic analysis in CS postmortem brain tissue, CS mouse and C. elegans models showed that mitochondrial dysfunction is indeed a common feature in CS. Interestingly, the restoration of mitochondrial dysfunction through NAD+ supplementation significantly improved lifespan and healthspan in the C. elegans models of CS, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. We proceeded to perform molecular studies on cerebellar samples obtained from CS patients. We found that these patients exhibited molecular signatures of dysfunctional mitochondrial dynamics that can be corrected with NAD+ supplementation in primary cells with depleted CSA or CSB. Our study provides support for the interconnection between two major aging theories, DNA damage and mitochondrial dysfunction. Together these two agents contribute to an accelerated aging program that can be averted by NAD+ supplementation.
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Project description:The macro domain of the histone variant macroH2A1.1 is an evolutionary conserved ADP ribose-binding module of unknown physiological function. We demonstrate that during myogenic differentiation alternative splicing switches the expression of macroH2A1 from the non-ADP ribose binding to the binding isoform. While differentiation commitment is normal in cells lacking macroH2A1.1, we observe two phenotypes: diminished cell fusion correlating with reduced expression of adhesion and migration genes and reduced mitochondrial capacity. While the integrity of the ADP ribose-binding pocket is dispensable for gene regulation and fusion, it is critical to sustain optimal mitochondrial fatty acid oxidation. Rescue experiments using a pharmacological PARP-1 inhibitor and metabolomics support the idea that loss of macroH2A1.1 leads to PARP-1 activation and accelerated NAD+ consumption. As a consequence, the level of nicotinamide mononucleotide, the key metabolite for mitochondrial NAD+ pool regeneration, is reduced and sirtuins fail to maintain mitochondrial proteins in their hypoacetylated and active form. Our results support the idea that chromatin states containing the histone variant macroH2A1.1 contribute to optimal mitochondrial oxidative capacity by channeling the consumption of NAD+ from the nucleus to mitochondria in a manner largely independent on transcriptional regulation.
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Project description:Metabolic dysfunction is a primary feature of the premature aging Werner syndrome (WS), a heritable human disease caused by mutations in the gene encoding the DNA helicase Werner (WRN). However, the relationship between WRN mutation and its severe metabolic phenotypes is unclear. Here we report mitochondrial dysfunction and depletion of NAD+, a fundamental ubiquitous cofactor, in WS patient samples and WS animal models. NAD+ repletion restores NAD+ metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. At the organismal level, NAD+ repletion remarkably delays accelerated aging, including stem cell dysfunction in both C. elegans and Drosophila models of WS. Mechanistically, WRN physically binds to a key NAD+ biosynthetic enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) and facilitates its NAD+ production. Our findings reveal an unprecedented anti-aging mechanism of WRN that integrates its new function of NAD+ synthesis to coordinate mitochondrial maintenance and energy expenditure, and suggest therapeutic potential.
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Project description:Mitochondrial PARP1 Regulates NAD+-dependent Poly ADP-ribosylation on Mitochondrial Nucleoids
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Project description:Nicotinamide adenine dinucleotide (NAD+) is a vital small molecule with important redox capacity in oxidative phosphorylation (OXPHOS) and a key co-factor in various enzymatic reactions. The recent identification of the mitochondrial NAD+ transporter SLC25A51 provides strong evidence for a direct regulation of the mitochondrial NAD+ pool. Though the effect of this transporter on glucose metabolism has been described, its contribution to other NAD+-dependent processes such as ADP-ribosylation remains elusive. Here, we report that knockdown of SLC25A51 decreased the NAD+ concentration in mitochondria but increased the NAD+ concentration in the cytoplasm and nucleus. The increase in nuclear and cytoplasmic NAD+ was not due to the upregulation of the salvage pathway, thus pointing towards an overall redistribution of NAD+ from the mitochondria towards the cyto/nuclear compartment. Furthermore, the NAD+ redistribution induced by knockdown or knockout of SLC25A51 resulted, as quantified by immunofluorescence or analyzed by mass-spectrometry, in a loss of mitochondrial ADP-ribosylation and an increase of PARP1-mediated nuclear ADP-ribosylation under basal conditions. Further, MMS/Olaparib induced PARP1 chromatin retention and the sensitivity of triple-negative MDA-MB-436 breast cancer cells to PARP inhibition were both reduced upon knockdown of SLC25A51. In addition, H2O2-induced PARP1-dependent nuclear ADP-ribosylation was prolonged while phosphorylation of H2AX was unexpectedly reduced. Together these results provide evidence that lack of SCL25A51 and subsequently altered NAD+ compartmentalization affects not only mitochondrial and nuclear ADP-ribosylation but also other chromatin associated events.
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Project description:Background: Diabetes mellitus is the leading cause of cardiovascular and renal disease in the United States. In spite of all of the beneficial interventions implemented in patients with diabetes, there remains a need for additional therapeutic targets in diabetic kidney disease (DKD). Mitochondrial dysfunction and inflammation are increasingly recognized as important causes of the development and progression of DKD. However, the molecular connection between mitochondrial function, inflammation, and fibrosis remains to be elucidated. Methods: In the present studies we tested the hypothesis that enhancing NAD metabolism could increase mitochondrial sirtuin 3 (SIRT3) activity, improve mitochondrial function, decrease mitochondrial DNA damage, and prevent inflammation and progression of DKD. Results: We found that treatment of db-db mice with type 2 diabetes with nicotinamide riboside (NR) prevented albuminuria, increased urinary KIM1 excretion, and several parameters of DKD. These effects were associated with increased SIRT3 activity, improved mitochondrial function, and decreased inflammation at least in part via inhibiting the activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway. Conclusions: NR supplementation boosted the NAD metabolism to modulate mitochondrial function and inflammation and prevent progression of diabetic kidney disease.
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