p62/SQSTM1-dependent autophagy of Lewy body-like α-synuclein inclusions

PLoS One. 2012;7(12):e52868. doi: 10.1371/journal.pone.0052868. Epub 2012 Dec 31.

Abstract

α-Synuclein is the main component of Lewy bodies, the intraneuronal inclusion bodies characteristic of Parkinson's disease. Although α-synuclein accumulation is caused by inhibition of proteasome and autophagy-lysosome, the degradation of α-synuclein inclusions is still unknown. Formation of Lewy body-like inclusions can be replicated in cultured cells by introducing α-synuclein fibrils generated in vitro. We used this cell culture model to investigate the autophagy of α-synuclein inclusions and impaired mitochondria. The intracellular α-synuclein inclusions immediately underwent phosphorylation and ubiquitination. Simultaneously they were encircled by an adaptor protein p62/SQSTM1 and directed to the autophagy-lysosome pathway in HEK293 cell line. Most phospho-α-synuclein-positive inclusions were degraded in 24 h, however, lysosomal dysfunction with bafilomycin A1 significantly affected their clearance. Moreover, inhibition of autophagy by Atg-5 siRNA treatment reduced the incorporation of α-synuclein inclusions into LC3-positive autophagosomes. Knockdown experiments demonstrated the requirement of p62 for α-synuclein autophagy. These results demonstrate that α-synuclein inclusions are preferred targets for p62-dependent autophagy. Next, we investigated the autophagic clearance of impaired mitochondria in α-synuclein inclusion-containing cells. Impaired mitochondria were almost completely eliminated after mitochondrial uncoupling even in the presence of α-synuclein inclusions, suggesting that mitochondrial clearance is not prevented by α-synuclein inclusions in HEK293 cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amyloid / metabolism
  • Autophagy*
  • HEK293 Cells
  • Humans
  • Lewy Bodies / metabolism*
  • Lysosomes / metabolism
  • Mitochondria / metabolism
  • Mitophagy
  • Phagosomes / metabolism
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Proteolysis
  • Sequestosome-1 Protein
  • Ubiquitination
  • alpha-Synuclein / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Amyloid
  • SQSTM1 protein, human
  • Sequestosome-1 Protein
  • alpha-Synuclein

Grants and funding

This study was supported by Grants-in-Aid from the Research Committee of CNS Degenerative Diseases, the Ministry of Health, Labour and Welfare of Japan to M.N., and from the Ministry of Education, Culture, Sports, Science, and Technology, Japan, to Y.W. (No. 24591272), T.T. (No. 23591252), T.M. (No. 22591595), and M.T. (No. 21500329). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.