All ETDs from UAB

Advisory Committee Chair

Jianhua Zhang

Advisory Committee Members

James Collawn

Anita Hjelmeland

Adam Wende

Talene Yacoubian

Document Type

Dissertation

Date of Award

2017

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Parkinson’s disease (PD) is the 2nd most common neurodegenerative disorder with aging as a significant risk factor. Sharing with aging brains, postmortem PD brains exhibit cellular deficits including autophagic dysfunction, mitochondrial dysfunction, and intracellular protein aggregates of alpha-synuclein. This dissertation will focus on the interplay between these key disease features. To that end, we coupled primary cortical neuronal cultures from either rats or mice with Seahorse extracellular flux, metabolomics and biochemical techniques. Autophagy is an important cell recycling program responsible for the clearance of damaged proteins and organelles. Bafilomycin A1 and chloroquine are compounds that inhibit autophagy by targeting the lysosome. Since it is now clear that mitochondrial quality control is dependent on autophagy, we determined whether these compounds could modify cellular bioenergetics. As expected, both bafilomycin and chloroquine significantly increased the autophagosome marker LC3-II. Under these conditions, we found that they significantly inhibited parameters of mitochondrial function and increased mtDNA damage without inducing cell death. Associated with these mitochondrial deficits, we also observed significant alterations in TCA cycle intermediates, indicating a significant role of autophagy in cellular metabolic programs. Beyond the importance of autophagy for mitochondrial quality, we further investigated the interplay between protein aggregation and autophagy in a PD model. Exposure to aSyn pre-formed fibrils (PFFs) has been shown to induce aggregation of endogenous aSyn resulting in cell death that is exacerbated by autophagy induction through either starvation or inhibition of mTOR by rapamycin. Since mTOR inhibition may also inhibit protein synthesis, and starvation by itself can be detrimental to neuronal survival, we investigated the effects of autophagy induction by a starvation and mTOR-independent method, using trehalose. We observed that on exposure to PFFs, there was increased abundance of pS129-aSyn aggregates and cell death. Trehalose alone increased LC3-II levels, consistent with increased autophagosome levels, that remained elevated with PFF exposure. Interestingly, trehalose alone increased cell viability over a 14-day time course and was also able to restore cell viability to control levels, but PFFs still exhibited toxic effects on the cells. Together, these data provide essential information regarding the interplay of autophagy, mitochondrial function and protein aggregation in PD.

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