Identification and characterization of a novel endogenous murine parkin mutation

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Abstract
J. Neurochem. (2010) 113, 402–417. Abstract Various mutations in the PARK2 gene which encodes the protein, parkin, are causal of a disease entity‐termed autosomal recessive juvenile parkinsonism. Parkin can function as an E3 ubiquitin‐protein ligase, mediating the ubiquitination of specific targeted proteins and resulting in proteasomal degradation. Parkin is thought to lead to parkinsonism as a consequence of a loss in its function. In this study, immunoblot analyses of brain extracts from Balb/c, C57BL/6, C3H, and 129S mouse strains demonstrated significant variations in immunoreactivity with anti‐parkin monoclonal antibodies (PRK8, PRK28, and PRK109). This resulted partly from differences in the steady‐state levels of parkin protein across mouse strains. There was also a complete loss of immunoreactivity for PRK8 and PRK28 antibodies in C3H mice due to was because of a homologous nucleotide mutation resulting in an E398Q amino acid substitution. In cultured cells, parkin harboring this mutation had a greater tendency to aggregate, exhibited reduced interaction with the E2 ubiquitin‐conjugating enzymes, UbcH7 and UbcH8, and demonstrated loss‐of‐function in promoting the proteosomal degradation of a specific putative substrate, synphilin‐1. In situ, C3H mice displayed age‐dependent increased levels of brain cortical synphilin‐1 compared with C57BL/6, suggesting that E398Q parkin in these mice is functionally impaired and that C3H mice may be a suitable model of parkin loss‐of‐function similar to patients with missense mutations.

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