title: Lysosomal enzyme cathepsin B enhances the aggregate forming activity of exogenous α-synuclein fibrils.
abstract: The formation of intracellular aggregates containing α-synuclein (α-Syn) is one of the key steps in the progression of Parkinson's disease and dementia with Lewy bodies. Recently, it was reported that pathological α-Syn fibrils can undergo cell-to-cell transmission and form Lewy body-like aggregates. However, little is known about how they form α-Syn aggregates from fibril seeds. Here, we developed an assay to study the process of aggregate formation using fluorescent protein-tagged α-Syn-expressing cells and examined the aggregate forming activity of exogenous α-Syn fibrils. α-Syn fibril-induced formation of intracellular aggregates was suppressed by a cathepsin B specific inhibitor, but not by a cathepsin D inhibitor. α-Syn fibrils pretreated with cathepsin B in vitro enhanced seeding activity in cells. Knockdown of cathepsin B also reduced fibril-induced aggregate formation. Moreover, using LAMP-1 immunocytochemistry and live-cell imaging, we observed that these aggregates initially occurred in the lysosome. They then rapidly grew larger and moved outside the boundary of the lysosome within one day. These results suggest that the lysosomal protease cathepsin B is involved in triggering intracellular aggregate formation by α-Syn fibrils.
authors.affiliation: Department of Basic Geriatrics, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tsujimura
authors.affiliation: Department of Basic Geriatrics, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Taguchi
authors.affiliation: Department of Basic Geriatrics, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Neurology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Harutsugu
authors.initials: H
authors.lastname: Tatebe
authors.affiliation: Department of Neurology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Tokuda
authors.affiliation: Department of Neurology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Mizuno
authors.affiliation: Department of Basic Geriatrics, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Kyoto 602-8566, Japan. Electronic address: mtanaka@koto.kpu-m.ac.jp.
authors.forename: Masaki
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D000682:Amyloid / Q000378:metabolism; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002402:Cathepsin D / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D066263:Protein Aggregation, Pathological / Q000378:metabolism*; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D000682:Amyloid; D051844:alpha-Synuclein; D002401:Cathepsin B; D002402:Cathepsin D
keywords: Aggregate formation; Cathepsin B; Fibril; Lysosome; α-Synuclein