Investigating the molecular mechanisms of p53-dependent lifespan regulation in Drosophila melanogaster

This dissertation was focused on elucidating the molecular mechanisms that govern p53-dependent longevity in Drosophila melanogaster. Specifically, determining the role of metabolism in p53-dependent longevity. A relationship between p53 and glucose-6-phosphate dehydrogenase (G6PD) has previously been established in mice. G6PD is a metabolic enzyme important for producing reducing equivalents used in redox regulation as well as biological precursors crucial to cell growth. I hypothesized that G6PD played a role in p53-dependent longevity. A lack of physical interaction between the two proteins, Dmp53's inability to influence the activity of G6PD, and epistasis lifespan experiments contributed to a clear lack of G6PD involvement in p53-dependent longevity.;A relationship between p53 and redox regulation was also investigated as another mechanism that could explain p53-dependent longevity. Specifically, I determined the relationship between p53 and glutamate cysteine ligase (GCL), a glutathione producing redox enzyme known to play a role in aging and longevity. Glutathione is one of the most critically important molecules utilized in redox homeostasis and furthermore, redox regulation has long been implicated as a major cause of aging as there is a pro-oxidizing shift in redox state throughout an organism's life. Therefore, I investigated the involvement of redox state in p53-dependent lifespan regulation. I did not discover any evidence that indicated p53 and GCLc were acting in the same longevity pathways, however by modulating GCLc levels in multiple tissues I observed tissue-specific GCLc knockdown-mediated longevity effects independent of p53. I demonstrated that RNAi knockdown of GCLc in two key metabolic tissues, the insulin producing cells (IPCs) and fat body produced significant longevity effects in female flies. In the IPCs, longevity was correlated with reduction of Drosophila insulin-like peptides (dILPs), meanwhile fat body GCLc knockdown seemed to mimic another longevity intervention, dietary restriction (DR), specifically through reduction of methionine.;A comparative transcriptional profile array was used to identify common genes upregulated or downregulated in three known longevity interventions: DR, p53, and Sir2. Synaptogyrin, a vesicle trafficking protein, was identified in this screen and is characterized in scientific literature. Synaptogyrin was determined to be a novel longevity gene able to increase lifespan of the adult fly in a dose-dependent manner. Epistasis experiments indicated that Synaptogyrin has a moderate role in the p53-dependent longevity pathway as p53-longevity is partially reduced in the absence of Synaptogyrin. This dissertation provides a foundation to investigate an emerging neuroprotective role for p53, as well as tissue-specific modulation of key redox enzymes in aging and longevity.