SYVN1 and Parkinson disease: A previous study investigated the association between HRD1 (ubiquitin ligase)/SEL1L (HRD1 stabilizer) and PD, and demonstrated that 6-OHDA-induced cell death is enhanced when the SEL1L expression is downregulated [18], which is in contrast to some findings showing that the HRD1 expression is downregulated.