Parkin is an E3 ligase in the ubiquitin-proteasome system. Hereditary Parkinson’s disease is most commonly caused by mutations in the parkin gene and is characterized by the progressive loss of dopaminergic neurons and the presence of Lewy bodies in the substania nigra (Jenner et al.,1992). Recent evidence suggests that phosphorylation of parkin at Ser378 may have an important regulatory role on its E3 ubiquitin ligase activity (Yamamoto et al., 2005). Anti-Phospho-Ser378 Parkin Western blot of HEK293 cells transfected with Parkin WT (Phospho) and Parkin S378 mutant (non-phospho) showing the phospho-specific immunolabeling of the ~ 52 k parkin protein. The immunolabeling is absent in the parkin S378 mutant.