• Sana Afreen and Adriana Ferreira.
• Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
• Neuroscience. 2019 Aug 1; 412: 1-15.

AbstractCalpain-mediated tau cleavage into the neurotoxic tau45-230 fragment plays an important role in Alzheimer's disease (AD). This tau fragment accumulates mainly in the cytoplasm of degenerating neurons. However, subcellular localization studies indicated that a pool of tau45-230 associates with the cytoskeleton in hippocampal neurons. In the present study, we assessed whether such localization could underlie tau45-230 neurotoxic effects. Quantitative Western blot analysis showed decreased levels of full-length tau bound to microtubules in tau45-230-expressing hippocampal neurons when compared to controls. In addition, the presence of this tau fragment induced a transient increase in tyrosinated tubulin, a marker of unstable microtubules, followed by a significant decrease in the levels of this tubulin isoform. The data obtained also showed a significant reduction in actin filaments in tau45-230-expressing neurons. These changes in microtubules and actin filaments correlated with delayed neurite elongation and axonal differentiation in the presence of this tau fragment. Together, these results suggest that tau45-230 could exert its toxic effects, at least in part, by modifying the composition of the neuronal cytoskeleton and impairing neurite elongation in neurons undergoing degeneration.Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.

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