Structural and Functional Impact of Parkinson Disease-Associated Mutations in the E3 Ubiquitin Ligase Parkin

ABSTRACT Mutations in the PARKIN/PARK2 gene that result in loss‐of‐function of the encoded, neuroprotective E3 ubiquitin ligase Parkin cause recessive, familial early‐onset Parkinson disease. As an increasing number of rare Parkin sequence variants with unclear pathogenicity are identified, structure–function analyses will be critical to determine their disease relevance. Depending on the specific amino acids affected, several distinct pathomechanisms can result in loss of Parkin function. These include disruption of overall Parkin folding, decreased solubility, and protein aggregation. However pathogenic effects can also result from misregulation of Parkin autoinhibition and of its enzymatic functions. In addition, interference of binding to coenzymes, substrates, and adaptor proteins can affect its catalytic activity too. Herein, we have performed a comprehensive structural and functional analysis of 21 PARK2 missense mutations distributed across the individual protein domains. Using this combined approach, we were able to pinpoint some of the pathogenic mechanisms of individual sequence variants. Similar analyses will be critical in gaining a complete understanding of the complex regulations and enzymatic functions of Parkin. These studies will not only highlight the important residues, but will also help to develop novel therapeutics aimed at activating and preserving an active, neuroprotective form of Parkin. Fiesel et al., provides a structure‐function analysis of human PARK2 mutations and pathogenic PD mechanisms. The crystalline structure in the front shows the ‘closed’, auto‐inhibited conformation of the E3 ubiquitin ligase Parkin. Upon activation by PINK1, Parkin undergoes major structural rearrangements in order to gain enzymatic activity. The functional data in the monochrome background are obtained from cell‐based imaging of the Parkin mutants. Activation and enzymatic activity of Parkin is coupled to its translocation from the cytosol onto damaged mitochondria.