Parkinson's disease (PD) is a common neurodegenerative disease, but its pathogenesis remains elusive. A mutation in ubiquitin C-terminal hydrolase L1 (UCH-L1) is responsible for a form of genetic PD which strongly resembles the idiopathic PD. We previously showed that 1-(3′,4′-dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline (3′,4′DHBnTIQ) is an endogenous parkinsonism-inducing dopamine derivative. Here, we investigated the interaction between 3′,4′DHBnTIQ and UCH-L1 and its possible role in the pathogenesis of idiopathic PD. Our results indicate that 3′,4′DHBnTIQ binds to UCH-L1 specifically at Cys152 in vitro. In addition, 3′,4′DHBnTIQ treatment increased the amount of UCH-L1 in the insoluble fraction of SH-SY5Y cells and inhibited its hydrolase activity to 60%, reducing the level of ubiquitin in the soluble fraction of SH-SY5Y cells. Catechol-modified UCH-L1 as well as insoluble UCH-L1 were detected in the midbrain of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated PD model mice. Structurally as well as functionally altered UCH-L1 have been detected in the brains of patients with idiopathic PD. We suggest that conjugation of UCH-L1 by neurotoxic endogenous compounds such as 3′,4′DHBnTIQ might play a key role in onset and progression of idiopathic PD.
We investigated the interaction between ubiquitin C-terminal hydrolase L1 (UCH-L1) and the brain endogenous parkinsonism inducer 1-(3′,4′-dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline (3′,4′DHBnTIQ). Our results indicate that 3′,4′DHBnTIQ binds to UCH-L1 specifically at cysteine 152 and induces its aggregation. 3′,4′DHBnTIQ also inhibits the hydrolase activity of UCH-L1. Catechol-modified as well as insoluble UCH-L1 were detected in the midbrains of MPTP-treated Parkinson's disease (PD) model mice. Conjugation of UCH-L1 by neurotoxic endogenous compounds like 3′,4′DHBnTIQ might play a key role in onset and progression of PD.