Enhancement of the autophagy-lysosomal pathway modulates the process of amyloid β-protein generation

[Speaker] Wataru Araki:1
[Co-author] Fumiko Yamamoto:1,2, Kaori Taniguchi:1, Naomi Mamada:2, Akira Tamaoka:2, Fuyuki Kametani:3, Madepalli K Lakshmana:4
1:Dept of Demyelinating Dis & Aging, National Inst of Neurosci, NCNP, Japan, 2:Dept of Neurology, Faculty of Medicine, Univ of Tsukuba, Japan, 3:Dept of Dementia and Higher Brain Function, Tokyo Metropolitan Inst of Medical Science, Japan, 4:Torrey Pines Inst for Molecular Studies, USA

Abnormalities in the autophagy-lysosomal pathway (ALP) are implicated in the pathology of Alzheimer's disease (AD). The transcription factor EB (TFEB) is a master regulator of ALP, and its activation leads to up-regulation of ALP. In the present study, we sought to clarify whether ALP facilitation induced by TFEB influences the process of amyloid β-protein (Aβ) generation in neurons. Rat primary cortical neurons cultured for a long term were used in this study. Untreated neurons or those infected with recombinant adenoviruses expressing wild-type amyloid precursor protein (APP) at 14 days in vitro (DIV) were then infected with adenoviruses expressing TFEB or empty adenoviruses at DIV15. Cells and conditioned media were harvested for Western blot analysis of cell lysates and Aβ measurement, respectively, at DIV18. We confirmed that TFEB up-regulated the protein expression of cathepsin D under the basal and APP overexpression conditions. Under both conditions, TFEB significantly increased ADAM10 levels, but did not affect APP and BACE1 levels; TFEB also did not affect levels of PS1, PS2, APH-1, and PEN-2, but slightly decreased mature nicastrin levels. TFEB significantly increased levels of α-C-terminal fragment (α-CTF) of APP in neurons expressing APP. TFEB decreased amounts of secreted Aβ40 under the basal condition, but increased them under the condition of APP overexpression. We are further examining whether TFEB affects the metabolism of β-CTF, using neurons overexpressing β-CTF. These results collectively suggest that TFEB-mediated enhancement of ALP modulates APP metabolism and Aβ generation in neurons.
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