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Sirtuin 3: The Mitochondrial Guardian - A Key Player in Cancer Prevention

Dive into the role of Sirtuin 3, a crucial mitochondrial watchdog protein identified by David Gius, M.D., Ph.D. Explore its impact on cancer prevention, aging, and longevity through deacetylation and post-translational protein modification. Discover how Sirtuin genes enhance lifespan and inhibit tumorigenesis, with insights on Sirt3 as a tumor suppressor in human cancers and a potential physiological target for stress response. Uncover the intricate mechanism involving targets like MnSOD for detoxifying mitochondrial superoxide, shedding light on the link between metabolism, oxidative damage, and cellular health. Join the journey through the Gius Lab's groundbreaking research on Sirtuin 3 and its implications in cancer biology.

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Sirtuin 3: The Mitochondrial Guardian - A Key Player in Cancer Prevention

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  1. Sirtuin 3: A Mitochondrial Watchdog Protein David Gius, M.D., Ph.D. Professor, Departments of Cancer Biology, Pediatrics, and Radiation Oncology Vanderbilt University School of Medicine Vanderbilt Medical School

  2. The Human Sirtuins Nuclear • Sirt1 • Sirt6 • Sirt7 Mitochondrial • Sirt3 • Sirt4 • Sirt5 Cytoplasmic • Sirt2

  3. In active protein Active protein Protein Deacetylation as a Post-Translation Protein Modification Non-Histone Protein

  4. ? Activation of Sirtuin genes increase longevity Mice lacking Sirt2 and Sirt3 were constructed to determine if they prevent cancer / TSGs? Rational for Sirtuins as Tumor Suppressors Carcinogenesis Decreases aging Increasing age Caloric Restriction

  5. Tumor Suppressor Gene • Loss of function results in an in vitro tumor permissive cellular phenotype (two hit tissue culture immortalization. • Genetic knockout in mice results in the formation of murine tumors. • There is a loss of function or decrease in protein levels in human malignancies and this matches human samples.

  6. CMV Promoter Oncogene 1 CMV Promoter Oncogene 2 Proliferative gene Pro Pro - - proliferative proliferative Pro Pro - - survival genes survival genes I I P P P P P P P P Normal cell Normal cell Transformed cell Transformed cell Two Gene Transformation Model for MEFs TSG Gene Loss Myc Ras

  7. Sirt3-/- MEFs are immortalized by a Single Oncogene Sirt3+/+ Myc/Ras cells Sirt3-/- Myc/Ras cells Kim et al, 2010 Cancer Cell

  8. In Vitro Transformation Sirt3-/- MEFs by a Single Oncogene

  9. Mammary Carcinogenesis in the Sirt3 knockout mice

  10. SIRT3 is Decreased in Human Breast Cancers Tissue Array (IHC) RNA Array (RT-PCR) Kim et al, 2010 Cancer Cell

  11. SIRT3 is Decreased in Human Breast Cancers Oncomine, UMich

  12. Sirt3 is a mitochondrial tumor suppressor but… Mechanism? Is it a sensing protein? What are the targets of Sirt3 ? Or what dysregulated proteins play a role in the Sirt3-/- tumor permissive?

  13. Transformed Sirt3 KO MEFs exhibit mt Superoxide Kim et al, 2010 Cancer Cell

  14. Primary Mitochondrial O2- Detoxification Pathway O2- H2O2 H2O + O2 MnSOD Catalase

  15. Criteria for Potential Sirt3 physiological Target • A protein that contain at least one reversible acetyl lysine that is altered by either caloric restriction, feasting, or other type of stress. • A Protein is hyperacetylated in the Sirt3 knockout livers or MEFs. • A protein contains at least one lysine that is deacetylated by Sirt3 both in vitro and in vivo. • The reversible acetyl lysine is evolutionary through out multiple species including less complex species. • Acetylation of the target lysine regulates enzymatic activity.

  16. MnSOD contains a reversible lysine Tao et al., 2010, Molecular Cell

  17. MnSOD’s reversible is deacetylated by Sirt3

  18. MnSOD K122 is an evolutionarily conserved reversible lysine Tao et al., 2010, Molecular Cell

  19. MnSOD K122 is Deacetylated by Sirt3 in vitro and in vivo In vitro In vivo

  20. De-Acetylated MnSOD Acetylated MnSOD MnSODK122 acetylation status directs dismutase activity MnSOD-/- MEFs Tao et al., 2010, Molecular Cell

  21. MnSODK122-R prevents in vitro Immortalization Tao et al., 2010, Molecular Cell

  22. MnSOD De-Acetylation Responds to Exercise and CR

  23. O2- O2- O2- - + O2- O2- H2O2

  24. AC AC AC AC AC AC FOXO How does MnSOD fit into this model?? Feasting Metabolic State Fasting Metabolic State ATP and Oxidative damage Repair of Oxidative damage MnSOD AC AC AC AC AC AC AC AC Aging Cancer Pro-metabolism Longevity Hibernation Energy Conservation

  25. The Gius Lab

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