Praja1 ubiquitin ligase facilitates degradation of polyglutamine proteins and suppresses polyglutamine-mediated toxicity.

Baijayanti Ghosh, Susnata Karmakar, Mohit Prasad, Atin K Mandal

Molecular biology of the cell 2021 Aug 15

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A network of chaperones and ubiquitin ligases sustain intracellular proteostasis and is integral in preventing aggregation of misfolded proteins associated with various neurodegenerative diseases. Using cell-based studies of polyglutamine (polyQ) diseases, spinocerebellar ataxia type 3 (SCA3) and Huntington's disease (HD), we aimed to identify crucial ubiquitin ligases that protect against polyQ aggregation. We report here that Praja1 (PJA1), a Ring-H2 ubiquitin ligase abundantly expressed in the brain, is diminished when polyQ repeat proteins (ataxin-3/huntingtin) are expressed in cells. PJA1 interacts with polyQ proteins and enhances their degradation, resulting in reduced aggregate formation. Down-regulation of PJA1 in neuronal cells increases polyQ protein levels vis-a-vis their aggregates, rendering the cells vulnerable to cytotoxic stress. Finally, PJA1 suppresses polyQ toxicity in yeast and rescues eye degeneration in a transgenic Drosophila model of SCA3. Thus, our findings establish PJA1 as a robust ubiquitin ligase of polyQ proteins and induction of which might serve as an alternative therapeutic strategy in handling cytotoxic polyQ aggregates.

Citation

Baijayanti Ghosh, Susnata Karmakar, Mohit Prasad, Atin K Mandal. Praja1 ubiquitin ligase facilitates degradation of polyglutamine proteins and suppresses polyglutamine-mediated toxicity. Molecular biology of the cell. 2021 Aug 15;32(17):1579-1593