UCH-L1 (also known as PARK5 and PGP9.5) was previously found to be enriched in neurons, shown to promote alpha-synuclein neurotoxicity in PD patients (Liu et al., 2009) at the same time being proposed as an oncogene (Hurst-Kennedy et al., 2012; Zhong et al., 2012). Here, UCHL1 is linked to Parkinson disease.