mRNA localization as a driver of mitochondrial dysfunction during neurodegeneration - Project Summary/Abstract
Age-related neurodegenerative diseases are a class of incurable diseases that result in the progressive
degeneration of neuronal cells. Mitochondria are essential cellular organelles that are key sources of
ATP generated by oxidative phosphorylation. Mitochondria contain their own DNA and protein synthesis
machinery, yet 99% of mitochondrial proteins are encoded by nuclear DNA and must be imported into
the mitochondria. Mitochondria are dynamic in both their composition and structure, forming dynamic
tubular networks through fission and fusion reactions. In neurodegenerative disorders such as
Alzheimer’s, Parkinson’s and Huntington’s disease, there is a phenomenon known as mitochondrial
fragmentation, in which the normal, elongated shape of mitochondria becomes disrupted and they
instead take on a more fragmented, round appearance. How mitochondrial fragmentation leads to
mitochondrial dysfunction is unknown, but it is important to understand as inhibition of mitochondrial
fragmentation has been found to be protective in disease models of Alzheimer’s, Parkinson’s and
Huntington’s disease. We propose a novel hypothesis that stable localization of nuclear-encoded
mitochondrial mRNAs to the mitochondrial surface and co-translational targeting of proteins to
individual mitochondrial fragments leads to heterogeneity in the expression of mitochondrial proteins
across mitochondrial fragments driving mitochondrial dysfunction. This proposal seeks to establish
basic principles of this hypothesis. To accomplish this, we will (Aim1) quantify the heterogeneity of
protein expression across different mitochondrial morphologies driven by human disease inducing
proteins Aβ42 and Htt103Q. Secondly, we will (Aim2) test the impact of mRNA localization and co-
translation mitochondrial protein insertion on protein heterogeneity and mitochondrial dysfunction.
Finally, we will (Aim3) establish tools for exploring this question in mammalian models by exploring
mitochondrial mRNA localization and protein heterogeneity in mammalian cells. In the short term our
goal is to establish a new model that explains how mitochondria become dysfunctional across different
mitochondrial morphologies. In the long term we will build on these discoveries by conducting further
investigations using mammalian models of neurodegeneration.
