Proteasome inhibition and aggregation in Parkinson's disease: a comparative study in untransfected and transfected cells

Authors

  • Emiliano Biasini,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    2. Dulbecco Telethon Institute (DTI), Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
    • 1

      These two authors contributed equally to this work.

  • Luana Fioriti,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    2. Dulbecco Telethon Institute (DTI), Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
    • 1

      These two authors contributed equally to this work.

  • Ilaria Ceglia,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
  • Roberto Invernizzi,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
  • Alessandro Bertoli,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
    • 2

      Current address: Department of Biological Chemistry, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy.

  • Roberto Chiesa,

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    2. Dulbecco Telethon Institute (DTI), Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author
  • Gianluigi Forloni

    1. Department of Neuroscience, Istituto di Ricerche Farmacologiche ‘Mario Negri’ Milano, Italy
    Search for more papers by this author

Address correspondence and reprint requests to Gianluigi Forloni Istituto di Ricerche Farmacologiche ‘Mario Negri’, 20157 Milano, Italy.
E-mail: forloni@marionegri.it

Abstract

Dysfunction of the ubiquitin-proteasome system (UPS) has been implicated in Parkinson's disease (PD) and other neurodegenerative disorders. We have investigated the effect of UPS inhibition on the metabolism of α-synuclein (SYN) and parkin, two proteins genetically and histopathologically associated to PD. Pharmacological inhibition of proteasome induced accumulation of both parkin and SYN in transfected PC12 cells. We found that this effect was caused by increased protein synthesis rather than impairment of protein degradation, suggesting that inhibition of the UPS might lead to non-specific up-regulation of cytomegalovirus (CMV)-driven transcription. To investigate whether endogenous parkin and SYN can be substrate of the UPS, untransfected PC12 cells and primary mesencephalic neurones were exposed to proteasome inhibitors, and parkin and SYN expression was evaluated at both protein and mRNA level. Under these conditions, we found that proteasome inhibitors did not affect the level of endogenous parkin and SYN. However, we confirmed that dopaminergic neurones were selectively vulnerable to the toxicity of proteasome inhibitors. Our results indicate that studies involving the use of proteasome inhibitors, particularly those in which proteins are expressed from a heterologous promoter, are subjected to potential artefacts that need to be considered for the interpretation of the role of UPS in PD pathogenesis.

Ancillary