Differential effects of UCHL1 modulation on alpha-synuclein in PD-like models of alpha-synucleinopathy

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by genetic and environmental factors. Abnormal accumulation and aggregation of alpha-synuclein (a-syn) within neurons, and mutations in the a-syn and UCH-L1 genes have been shown to play a role in the pathogenesis of PD. In light of recent reports suggesting an interaction between a-synuclein and UCH-L1, we investigated the effects of UCH-L1 inhibition on a-syn distribution and expression levels in primary neurons and hippocampal tissues derived from non transgenic (non tg) and a-syn over expressing tg mice. We show that suppression of UCH-L1 activity increased a-syn levels in control, non tg neurons, and resulted in a concomitant accumulation of presynaptic a-syn in these neurons. In contrast, blocking UCH-L1 activity in a-syn over expressing neurons decreased a-syn levels, and enhanced its synaptic clearance. In vitro studies verified the LDN-induced inhibition of UCH-L1 had minimal effect on LC3 (a marker of autophagy) in control cells, in cells over expressing a-syn UCH-L1 inhibition resulted in increased LC3 activity. These findings suggest a possible differential role of UCH-L1 function under normal and pathological conditions. Furthermore, in the context of a-syn-induced pathology, modulation of UCH-L1 activity could serve as a therapeutic tool to enhance the autophagy pathway and induce clearance of the observed accumulated/aggregated a-syn species in the PD brain.