Interaction between RING1 (R1) and Ubiquitin-Like (UBL) Domain Is Critical for the Regulation of Parkin Activity [Neurobiology]

December 2nd, 2015 by Ham, S. J., Lee, S. Y., Song, S., Chung, J.-R., Choi, S., Chung, J.

Parkin is an E3 ligase that contains an UBL domain in the N-terminus and an R1-in-between-ring (IBR)-RING2 (R2) motif in the C-terminus. We showed that the UBL domain specifically interacts with the R1 domain and negatively regulates Parkin E3 ligase activity, Parkin-dependent mitophagy, and Parkin translocation to the mitochondria. The binding between the UBL domain and the R1 domain was suppressed by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) treatment or by expression of PTEN-induced putative kinase 1 (PINK1), an upstream kinase that phosphorylates Parkin at S65 residue of the UBL domain. Moreover, we demonstrated that phosphorylation of the UBL domain at S65 prevents its binding to the R1 domain and promotes Parkin activities. We further showed that mitochondrial translocation of Parkin, which depends on the interaction between the R1 domain and a mitochondrial outer membrane protein, VDAC1, is also suppressed by competitive binding of the UBL domain to the R1 domain. Interestingly, Parkin with missense mutations-associated with Parkinson′s disease (PD) in the UBL domain, such as K27N, R33Q, and A46P, did not translocate to the mitochondria and induce E3 ligase activity by CCCP treatment, which correlated with the interaction between the R1 domain and the UBL domain with those PD mutations. These findings provide a molecular mechanism of how Parkin recruitment to the mitochondria and Parkin activation as an E3 ubiquitin ligase are regulated by PINK1, and explain the previously unknown mechanism of how Parkin mutations in the UBL domain cause PD pathogenesis.