Mitochondrial Fidelity in Mammalian Neurons

Summary Mitochondria are multifaceted organelles that play vital roles in a myriad of cellular functions, including energy production, metabolism, calcium homeostasis, and cell death. It is generally accepted that a decline in mitochondria quality is a key contributor to mitochondrial dysfunction, aging, and represents a key point of convergence for several neurological disorders. Yet, precisely how dysfunctional mitochondria contribute to these conditions remains elusive. Mitochondria are thought to be constantly rejuvenated via collaborative processes of mitogenesis, fission-fusion, and multi-level quality-control mechanisms. Accordingly, the average half-life of mitochondrial proteins in the brain has been estimated at less than 3 weeks. Recently, I identified a discrete number of mitochondrial long-lived proteins (mt-LLPs) that last at least four months in mouse brain and heart. These long-lived mitochondrial proteins (mt-LLPs) include OxPhos complexes and several mitochondrial cristae associated proteins, which similarly to other architecturally stable and long-lived structures (i.e. nuclear pore complexes) are recognized for their highly defined and elaborate ultrastructure. Therefore, we hypothesized that the exceptional longevity of mt-LLPs could play an essential role in the long-term stabilization of the mitochondrial cristae in long-lived, post-mitotic cells. The goal of this research proposal is to delineate the localization of mt-LLPs within mitochondria in neurons, examine their temporal dynamics and integration with newly synthesized proteins, and investigate their potential contribution to mitochondrial fitness and long-term cristae stability. In Aim 1, using a combination of pulse-chase protein labeling methods, super-resolution fluorescent imaging and mass spectrometry I propose to (1) examine the spatio-temporal dynamics of mt-LLPs in axonal and somato-dendritic domains of primary neurons. In Aim 2, we propose to extend our analysis to include mitochondrial DNA (mtDNA) by investigating the coordination between mt-LLPs enrichment and mtDNA longevity neurons. In Aim 3, I will investigate the mechanism(s) involved in persistence of mt-ELLPs in neurons using genetic manipulations targeting mitochondrial cristae stability. Lastly, in Aim 4 we will begin the investigation into the coordination between nuclear and mitochondrial genome expression in neurons. In summary, insights from the proposed experiments will significantly advance our understanding of long-term of mitochondrial proteome homeostasis and genome integrity in neurons, which could provide with new molecular targets for modulating the mitochondrial network dynamics in the processes of neurodegeneration.