title: p62/SQSTM1-dependent autophagy of Lewy body-like α-synuclein inclusions.
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.
authors.affiliation: Department of Basic Geriatrics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Harutsugu
authors.initials: H
authors.lastname: Tatebe
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Taguchi
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Endo
authors.forename: Takahiko
authors.initials: T
authors.lastname: Tokuda
authors.forename: Toshiki
authors.initials: T
authors.lastname: Mizuno
authors.forename: Masanori
authors.initials: M
authors.lastname: Nakagawa
authors.forename: Masaki
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000682:Amyloid / Q000378:metabolism; D001343:Autophagy; D057809:HEK293 Cells; D006801:Humans; D016631:Lewy Bodies / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D063306:Mitophagy; D010588:Phagosomes / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D000071456:Sequestosome-1 Protein; D054875:Ubiquitination; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000682:Amyloid; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D051844:alpha-Synuclein