Phosphorylated tau showed the biggest reported response in a laboratory study of how cells handle several proteins linked to Alzheimer’s disease. The pattern was not uniform: phosphorylated tau had the largest reported abundance change and a high association with LC3, the signal used to track recruitment to the macroautophagy compartment, while amyloid-beta showed limited engagement.
After 48 hours of butyric-acid exposure without bafilomycin A1, the reported relative abundance was 40.87 for phosphorylated tau, compared with 19.04 for tau, 3.18 for APP, 2.15 for amyloid-beta and 3.22 for alpha-synuclein. The reported standard errors were 11.47, 3.69, 0.27, 0.66 and 1.04, respectively.
In the matching 48-hour groups treated with bafilomycin A1, phosphorylated tau was reported at 63.53, with a standard error of 23.50, and tau at 19.52, with a standard error of 2.56. Together, the reported values made phosphorylated tau the most pronounced response in this comparison.
A split response among the proteins
Amyloid-beta showed a different pattern. Its reported abundance was 2.15, with a standard error of 0.66, after 48 hours of butyric acid alone and 2.20, with a standard error of 0.17, when bafilomycin A1 was added. The matched groups did not differ significantly. Alpha-synuclein was reported at 0.78, with a standard error of 0.32, after 24 hours without the inhibitor and 3.22, with a standard error of 1.04, after 48 hours. With bafilomycin, the corresponding values were 0.73, with a standard error of 0.48, and 2.74, with a standard error of 1.17; the inhibitor did not significantly alter abundance at matching time points.
LC3 abundance was higher in the bafilomycin-treated groups. After 24 hours, the reported value was 8.81, with a standard error of 0.75, with the inhibitor, compared with 0.23, with a standard error of 0.08, without it. After 48 hours, the values were 13.90, with a standard error of 1.66, and 1.31, with a standard error of 0.24, respectively. The study used LC3 overlap as a recruitment and localization measure, not as a standalone readout of completed protein breakdown.
The overlap analysis varied by protein and by the signal used as the reference. At 48 hours, the proportion of LC3 colocalized with phosphorylated tau was 0.39, with a standard error of 0.05. The proportions of total amyloid-beta and tau signal colocalized with LC3 were 0.03, with a standard error of 0.01, and 0.03, with a standard error of 0.02. APP and phosphorylated tau each had a reported total-protein-associated proportion of 0.25, with standard errors of 0.05 and 0.06, respectively.
A controlled cell experiment
To make the comparison, the researchers used mouse neuroblastoma N2a cells expressing the human Swedish APP mutation. They exposed the cells to 5 mM butyric acid for 24 or 48 hours, then gave inhibitor groups 400 nM bafilomycin A1 for 2 hours. The question was whether APP, amyloid-beta, alpha-synuclein, tau and phosphorylated tau were differentially engaged by macroautophagy during APP-associated proteotoxic stress.
Western blotting quantified relative protein abundance, while confocal immunofluorescence examined intracellular location and overlap with LC3. The researchers used one-way ANOVA or Kruskal-Wallis tests with post hoc comparisons, accepting a p-value below 0.05 as statistically significant. The measurements were reported as means with standard errors, so the exact size of each response should be read alongside the uncertainty around it.
The boundaries of the result
The result is bounded by the model and the measurements. It is a comparison within mouse neuroblastoma cells expressing human Swedish APP, under the defined chemical exposures, using relative abundance and LC3 colocalization as endpoints. In other words, it describes protein-specific responses in this experimental setup.
Taken together, the measurements describe selective, rather than uniform, macroautophagy engagement. Phosphorylated tau had the strongest reported abundance response and a high LC3-associated fraction, while amyloid-beta had similar reported abundance with and without the inhibitor at 48 hours.
The authors acknowledged funding from the South African Medical Research Council and declared no commercial or financial relationships that could be construed as a potential conflict of interest. They also stated that the original contributions were included in the article or supplementary material, with further inquiries directed to the corresponding authors.
Paper data and sources
Original title: Differential autophagy cargo engagement in amyloid-β-induced neuronal toxicity
Authors: Brink D, Theart R, Loos B
Journal/Repository: Frontiers in neuroscience
Status: Peer-reviewed
First online: 2026-10-09
DOI: Not available
Original paper · Full text