α-Synuclein ubiquitination and novel therapeutic targets for Parkinson's disease.

Accumulation of α-synuclein is key to the pathogenesis of Parkinson's disease (PD), though the exact mechanisms involved in its toxicity are still subject to debate. Increased α-synuclein expression or reduced degradation may play a role in the proteotoxicity observed in PD. Here we review the mechanisms of α-synuclein ubiquitination by different E3 ubiquitin-ligases, and its degradation via the proteasome, autophagy and lysosomes. Activators of α- synuclein ubiquitination and degradation pathways represent a plausible strategy to decrease α-synuclein burden in the disease. Nevertheless, since proteasomes and autophagy might be impaired in the disease, and because proteolytic impairment causes the accumulation of monoubiquitinated α-synuclein and the formation of toxic inclusions, compounds that promote α-synuclein monoubiquitination should be used in concert with compounds that boost these proteolytic pathways. This combined approach may therefore ease the accumulation of α-synuclein in PD and may represent a promising new avenue for the development of novel treatments for the disease.