Effect of agent and host factors on alpha-synuclein strain pathogenesis

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Protein misfolding diseases, or proteinopathies, are a group of invariably fatal neurodegenerative disorders affecting more than 6.8 million Americans. In multiple system atrophy (MSA) and other synucleinopathy patients, the protein α-synuclein (α-syn) misfolds into a self-templating conformation that spreads via a prion- like manner throughout the body, including the central nervous system (CNS). It is hypothesized that the conformation, or strain, that α-syn misfolds into encodes information about the clinical symptoms and neuropathologies a patient will develop. While previous studies focused on the biochemical differences between α-syn strains, the mechanism of how those differences encode distinct biological phenotypes of disease is poorly understood. The long-term goal of our research is to identify the agent and host factors that contribute to the varied clinical presentations observed across synucleinopathies. In this proposal, we will test the hypothesis that strain-specific differences in aggregate transport and neuroanatomical spread contribute to disease pathogenesis. In Aim 1, we will use alexa fluor-labeled α-syn aggregates to investigate the rate and direction of axonal transport in vitro and in vivo. To determine the molecular mechanisms responsible for α-syn transport, we will use chemical and genetic tools to disrupt microtubule polymerization, dynein motor activity, and dynein cargo adaptor binding, and quantify the strain-specific effects on α-syn axonal transport. In Aim 2, we will determine the role of trans-synaptic spread on α-syn strain pathogenesis. To rigorously perform these studies, we will first determine the titer of three different α-syn strains both in vitro and in vivo. We will then use the sciatic nerve injection model, with and without nerve transection, to determine if α-syn neuroinvasion relies exclusively on trans-synaptic spread, of if extraneural pathways contribute to disease pathogenesis when the same titer of each strain is injected. Finally, we will perform a thorough disease pathogenesis study to establish a temporal-spatial map of strain-specific α-syn spread. This work is innovative because it is the first study to investigate how interactions between the host and strain impact disease progression, and to establish between in vitro and in vivo α-syn titers. This work is significant because it is the first to investigate how interactions between host and strain contribute to the mechanisms underlying axonal transport and trans-synaptic spread of disease. Critically, by identifying the cellular and molecular machinery responsible for α-syn propagation, the results of these experiments will lead to new areas of promising investigation.