Defining proteostasis networks in axon segments

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PROJECT SUMMARY/ABSTRACT Neurodegenerative disorders represent a significant challenge to human health. Many therapeutic strategies revolve around suppressing death of the neuronal cell body. However, neuronal connectivity depends on long projections called axons that use specialized mechanisms to survive in isolation from the soma. The degeneration of axons is a common, sometimes initiating event in a variety of neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease, and peripheral neuropathies. Protecting axon health is necessary for sustaining functional connectivity and will have broad relevance to many diseases. In the aging nervous system there is a well-documented decline in protein homeostasis and accumulation of protein aggregates that threaten neuronal function. Protein homeostasis is predominantly studied in context of the neuronal cell body. However, axons are also susceptible because protein aggregates interfere with transport and disrupt synaptic function. Polypeptides are most vulnerable to misfolding and aggregation as they exit the ribosome. Axons locally synthesize many proteins needed for survival however there is a gap in knowledge regarding basic mechanisms that protect axons from protein misfolding. This project will determine the capacity of axon segments to resist protein misfolding and aggregation. We will also determine the preferred mechanisms used within axon segments for degrading non-native polypeptides and disposing of aggregates. NAD+ levels decline as we age and this project will identify the consequences local NAD+ depletion on protein homeostasis within the axon compartment. Altogether, this project will generate new insight on local mechanisms controlling axon health and reveal treatment opportunities in neurodegenerative disorders.