NEDD4 and Parkinson disease: Since Nedd4 is a ubiquitin ligase that functions in the endosomal–lysosomal pathway, our data are also consistent with other studies which have implicated this pathway in PD pathogenesis (Dodson et al., 2012) and genetic screens showing that genetic perturbations in endosomal trafficking increase α-synuclein toxicity in relevant cell models (Willingham et al., 2003).