Language
English (en)
Date of Award
12-15-2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Chair and Committee
Albert A. Davis
Committee Members
John R. Cirrito, Conrad Weihl, Meredith Jackrel, Marco Sardiello
Abstract
Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ), a process thought to result from an imbalance between Aβ production and clearance. Autophagy, a major intracellular degradation pathway regulated by the mechanistic target of rapamycin (mTOR), has emerged as a potential therapeutic target for restoring Aβ homeostasis, although its precise role in Aβ metabolism remains unclear. This study investigated how pharmacological modulation of autophagy and mTOR signaling influences Aβ levels in both in vitro and in vivo models.
Wild-type SH-SY5Y neuroblastoma cells were treated with a panel of autophagy-modulating compounds, and extracellular Aβ secretion was quantified alongside the autophagy markers LC3 and p62. Of the compounds examined, only bafilomycin A1 (Baf) and the catalytic mTOR inhibitor Torin1 (Tor1) significantly altered autophagic flux and reduced extracellular Aβ levels. Co-treatment produced an additive reduction in Aβ secretion, while inhibition of Aβ production with a γ-secretase inhibitor did not alter autophagic markers, indicating that the observed changes in Aβ occurred downstream of autophagy modulation.
To determine whether these findings translated in vivo, APP/PS1 mice received hippocampal administration of Baf, Tor1, or the catalytic mTOR inhibitor Torin2 via reverse microdialysis. In contrast to the in vitro results, both Baf and Tor1 increased interstitial fluid (ISF) Aβ concentrations. Kinetic analyses demonstrated that Tor1 significantly prolonged Aβ half-life, indicating impaired extracellular clearance, whereas Baf elevated ISF Aβ without affecting Aβ half-life, suggesting increased production or secretion. Torin2 similarly prolonged Aβ half-life but did not increase steady-state ISF Aβ levels. Immunohistochemical analyses confirmed inhibition of mTORC1 signaling by Tor1 through reduced phosphorylation of S6 kinase, whereas Torin2 did not significantly alter this pathway.
These findings demonstrate that modulation of autophagy and mTOR signaling exerts markedly different effects on Aβ metabolism in vitro and in vivo, highlighting the importance of extracellular clearance mechanisms involving glial cells and the brain microenvironment. Collectively, this work identifies a previously unrecognized role for catalytic mTOR inhibition in regulating extracellular Aβ clearance and establishes a foundation for future studies investigating the molecular pathways linking mTOR signaling, autophagy, and Aβ homeostasis. Improved understanding of these mechanisms may facilitate the development of therapeutic strategies aimed at restoring Aβ balance in Alzheimer's diseases.
DOI
https://doi.org/10.48765/mn25-aj64
Recommended Citation
Wycoff, Samuel, "Interplay of Autophagy and mTOR Signaling on Amyloid-Beta" (2026). WUSM Theses and Dissertations – All Programs. 63.
https://digitalcommons.wustl.edu/all_etd/63
