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Unfolding aggregates
Parkinson’s disease (PD) is characterized by the presence of Lewy bodies (LBs), abnormal protein aggregates in the neurons. In LB, α-synuclein associates with other proteins, including parkin and its substrate aminoacyl tRNA synthetase complex–interacting multifunctional protein-2 (AIMP2). The role of AIMP2 in PD pathophysiology remains unclear. Here, Ham et al. studied the role of AIMP2 in vitro and in vivo and showed that the protein had self-aggregating properties and accelerated the formation of α-synuclein aggregates. In models of α-synucleinopathies, AIMP2 was required for the formation of α-syn aggregates. The results suggest that AIMP2 plays a critical role in LB formation and might be a potential therapeutic target for reducing α-synuclein aggregates.
Abstract
Lewy bodies are pathological protein inclusions present in the brain of patients with Parkinson’s disease (PD). These inclusions consist mainly of α-synuclein with associated proteins, such as parkin and its substrate aminoacyl transfer RNA synthetase complex–interacting multifunctional protein-2 (AIMP2). Although AIMP2 has been suggested to be toxic to dopamine neurons, its roles in α-synuclein aggregation and PD pathogenesis are largely unknown. Here, we found that AIMP2 exhibits a self-aggregating property. The AIMP2 aggregate serves as a seed to increase α-synuclein aggregation via specific and direct binding to the α-synuclein monomer. The coexpression of AIMP2 and α-synuclein in cell cultures and in vivo resulted in the rapid formation of α-synuclein aggregates with a corresponding increase in toxicity. Moreover, accumulated AIMP2 in mouse brain was largely redistributed to insoluble fractions, correlating with the α-synuclein pathology. Last, we found that α-synuclein preformed fibril (PFF) seeding, adult Parkin deletion, or oxidative stress triggered a redistribution of both AIMP2 and α-synuclein into insoluble fraction in cells and in vivo. Supporting the pathogenic role of AIMP2, AIMP2 knockdown ameliorated the α-synuclein aggregation and dopaminergic cell death in response to PFF or 6-hydroxydopamine treatment. Together, our results suggest that AIMP2 plays a pathological role in the aggregation of α-synuclein in mice. Because AIMP2 insolubility and coaggregation with α-synuclein have been seen in the PD Lewy body, targeting pathologic AIMP2 aggregation might be useful as a therapeutic strategy for neurodegenerative α-synucleinopathies.
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