Lifespan varies dramatically among even closely related species, as exemplified within groups such as primates and rodents. Despite these disparities in lifespan, recent studies have focused on intra-specific aging pathologies, primarily within the murine system. While mice have provided much insight into aging biology, it is unclear if such a short-lived species lack defenses against senescence that may have evolved in related long- lived species. Many age-related diseases have been linked to mitochondrial dysfunction that are measured by decreased energy generation, structural damage to cellular components, and even cell death. Post translational modifications (PTMs) orchestrate many of the pathways associated with cellular metabolism, and are thought to be a key regulator in biological senescence. Hyperacetylation is one such modification that has been implicated in numerous mitochondrial impairments affecting energy metabolism. Recently, we observed significant hyperacetylation of proteins/enzymes in pathways associated with oxidative phosphorylation due to sirtuin 3 (SIRT3) knockout and elevated SIRT3 expression via caloric restriction - both factors that influence protein acetyl status. Furthermore, caloric restriction ad SIRT3 expression significantly increased electron flux through both complex I and II of the electron transport system (ETS) in muscle of mice, suggesting acetylation status plays a critical role in mitochondrial respiration. When comparing differences between species, preliminary work comparing mice to the long-lived naked mole rat revealed ETS-wide differences, such as lower leak respiration and complex IV activities in the brain and heart of naked mole rats, indicating inherent differences in mitochondrial metabolism. Here, we aim to establish whether hyperacetylation is associated with mitochondrial dysfunction and differences in lifespan between mice, rats, thirteen-lined ground squirrels, grey squirrels and naked mole rats. We will measure flux through the ETS in the muscle and liver of all five species using high-resolution respirometry and substantiate these measurements by measuring isolated complex activities. Next, we will quantify the stoichiometry of peptide acetylation from these samples to determine if they are correlated with both mitochondrial function and lifespan. The research proposed here will elucidate the evolutionary role of acetylation in regulating aging, and establish potential targets as well as validate existing targets for therapeutic interventions. The R03 small-grant mechanism is an excellent fit for the proposed work, as it nicely piggybacks with our ongoing aging studies in the murine model and takes advantage of our recently developed methods to determine site-specific stoichiometry of acetylation in a large proteome.
Despite the vast differences in lifespan that exist between closely related species, little is known regarding the mechanisms underlying these disparities. Dysregulated post-translational modifications of proteins have been linked to age-related diseases within species and under normal conditions have been established as an important regulator of mitochondrial function. This application will take advantage of newly developed methods and investigate this link using a comparative approach between five species of rodents representing short, mid, and long lifespans to understand the biochemical and physiological underpinnings of aging.
| Krautkramer, Kimberly A; Dhillon, Rashpal S; Denu, John M et al. (2017) Metabolic programming of the epigenome: host and gut microbial metabolite interactions with host chromatin. Transl Res 189:30-50 |
