Oxidative stress-induced parkin misfolding, aggregation, and toxicity

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Abstract Background: Excess oxidative stress and protein misfolding are major hallmarks of neurodegenerative disease, including Parkinson’s disease (PD). Mutations in the genes encoding the ubiquitin ligase parkin cause autosomal recessive juvenile forms of Parkinsonism by the loss of parkin function in mitochondrial homeostasis and cellular protein quality control, generally. Dysfunction of parkin might also contribute to sporadic forms of PD, yet the underlying mechanisms remain mostly unexplored. Methods: We obtained key results from studies in human PD brains, a mouse model, yeast, cultured neuronal cells, and in vitro biochemistry. Human postmortem Medial Temporal Gyrus tissue was fixed for immunohistochemistry. We performed biochemical analyses of protein lysates from human brain, mouse brain, yeast and cells to assess parkin modification by oxidative stress under normal growth conditions and more so under oxidative stress. Results: Our results reveal that oxidative stress damages parkin by inducing the formation of aberrant intra- and inter-molecular disulfide bonds, leading to parkin misfolding and inclusion formation, which is toxic to cells. We furthermore find that parkin is most severely oxidized in its active conformation. Conclusion: Collectively, our study identifies a mechanism by which protein oxidation can contribute to neurodegeneration in PD by combining loss of function with toxic gain of function mechanisms.

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