GPR37 and Parkinson disease: In addition, Parkin, a RING-finger type E3 ligase, is responsible for the proper disposal of multiple substrates involved in PD, including mutated a-synuclein, glycosylated synuclein-22, Parkin-associated endothelin-like receptor (Pael-R), synphilin, cell division control-related protein and a polyglutamine-expanded ataxin-3 mutant [19, 78, 79].