It is not known if or how mammalian cells induce selective translation of mitochondrial proteins and if this differs by cell/tissue type. The long-trm goal of this research is to identify strategies that can be used to increase mitochondrial protein synthesis in humans for the purpose of increasing healthspan. The overall objective is to identify post-transcriptional mechanisms that are involved in increasing mitochondrial protein synthesis during periods of energetic stress in mammalian cells/tissues. The central hypothesis is that the selective translation of mitochondrial proteins observed in liver, skeletal muscle, and heart of mammals during periods of energetic stress is dictated by the complexity of mRNA sequence elements and/or subcellular localization to the mitochondrial reticulum. This hypothesis has been formulated based on evidence generated in the applicants' laboratories as well as extensive published evidence in lower eukaryotes. The rationale for the proposed research is that the successful completion of this research would provide new opportunities to identify therapeutic targets to slow aging and prolong healthspan by targeting mechanisms that have been virtually unstudied in mammalian cells. The research has two specific aims: 1) to determine in vitro the mechanisms responsible for the preferential translation and synthesis of mammalian mitochondrial proteins during the signaling of energetic stress, and the extent of the contribution of autophagy/mitophagy to these increases, and 2) to identify strategies that activate pathways of energetic stress in vivo to preserve mitochondrial protein synthesis and slow aging. To accomplish these specific aims, multiple cell types and tissues will be analyzed. Methods used in vitro include polysome profiles with analysis of rapidly translating mRNA, bioinformatic analysis of mRNA sequences, and novel stable isotope techniques for the determination of mitochondrial protein synthesis and autophagic flux. Methods used in vivo include additional novel isotope techniques for measuring protein synthesis at the tissue, organelle, and individual protein level as well as cellular proliferation. The contribution of the proposed research is significant because it is designed to elucidate an important, but unstudied, regulatory step of mitochondrial biogenesis. Further, it is designed to translate in vitro mechanisms to in vivo studies to determine if these mechanisms can be targeted therapeutically. The proposed research is innovative because it considers post-transcriptional mechanisms of mitochondrial biogenesis, which have previously been largely overlooked. Further, the laboratory is among the very few groups capable of making long-term protein synthetic and cellular proliferation measurements that allow for the translation of in vitro studie to in vivo outcomes. Finally, the in vivo assessment of the synthesis of individual mitochondrial proteins has until now not been feasible, thus the project is technically innovative. The results are expected to have a positive impact because they focus on mechanisms that may offer novel therapeutic targets that are alternatives to a therapy (lifelong caloric restriction) that has provn efficacy, but extremely limited adherence in humans.
The proposed research is relevant to public health because it supports the National Institute of Aging mission of addressing mechanisms of aging and then develops interventions to target them therapeutically. The project is designed to translate in vitr mechanisms into possible in vivo treatments using pharmacologic approaches that are already in human use for other age-related diseases. Although the current proposal is focused on aging, it is likely that information gained will also be relevant to chronic diseases (e.g. diabetes and heart disease) in which mitochondrial dysfunction is thought to be causative.
|Pettit, Ashley P; Jonsson, William O; Bargoud, Albert R et al. (2017) Dietary Methionine Restriction Regulates Liver Protein Synthesis and Gene Expression Independently of Eukaryotic Initiation Factor 2 Phosphorylation in Mice. J Nutr 147:1031-1040|
|Shankaran, Mahalakshmi; King, Chelsea L; Angel, Thomas E et al. (2016) Circulating protein synthesis rates reveal skeletal muscle proteome dynamics. J Clin Invest 126:288-302|
|Bruns, Danielle R; Drake, Joshua C; Biela, Laurie M et al. (2015) Nrf2 Signaling and the Slowed Aging Phenotype: Evidence from Long-Lived Models. Oxid Med Cell Longev 2015:732596|
|Drake, Joshua C; Bruns, Danielle R; Peelor 3rd, Frederick F et al. (2015) Long-lived Snell dwarf mice display increased proteostatic mechanisms that are not dependent on decreased mTORC1 activity. Aging Cell 14:474-82|
|Miller, Benjamin F; Wolff, Christopher A; Peelor 3rd, Fredrick F et al. (2015) Modeling the contribution of individual proteins to mixed skeletal muscle protein synthetic rates over increasing periods of label incorporation. J Appl Physiol (1985) 118:655-61|
|Miller, Benjamin F; Ehrlicher, Sarah E; Drake, Joshua C et al. (2015) Assessment of protein synthesis in highly aerobic canine species at the onset and during exercise training. J Appl Physiol (1985) 118:811-7|
|Khademi, Shadi; Frye, Melinda A; Jeckel, Kimberly M et al. (2015) Hypoxia mediated pulmonary edema: potential influence of oxidative stress, sympathetic activation and cerebral blood flow. BMC Physiol 15:4|
|Drake, Joshua C; Bruns, Danielle R; Peelor 3rd, Frederick F et al. (2014) Long-lived crowded-litter mice have an age-dependent increase in protein synthesis to DNA synthesis ratio and mTORC1 substrate phosphorylation. Am J Physiol Endocrinol Metab 307:E813-21|
|Miller, Benjamin F; Drake, Joshua C; Naylor, Bradley et al. (2014) The measurement of protein synthesis for assessing proteostasis in studies of slowed aging. Ageing Res Rev 18:106-11|