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Updated: Feb 17, 2026
Assay for Phosphorylation and Microtubule Binding Along with Localization of Tau Protein in Colorectal Cancer Cells
Published on: October 10, 2017
Isoform-independent and -dependent phosphorylation of microtubule-associated protein tau in mouse brain during
Dilina Tuerde1, Taeko Kimura1, Tomohiro Miyasaka2
1From the Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397.
Abstract:
Tau is a microtubule (MT)-associated protein that regulates MT dynamics in the axons of neurons. Tau binds to MTs via its C-terminal MT-binding repeats. There are two types of tau, those with three (3R) or four (4R) MT-binding repeats; 4R tau has a stronger MT-stabilizing activity than 3R tau. The MT-stabilizing activity of tau is regulated by phosphorylation. Interestingly, both the isoform and phosphorylation change at the time of neuronal circuit formation during postnatal development; highly phosphorylated 3R tau is replaced with 4R tau, which is less phosphorylated. However, it is not known how the transition of the isoforms and phosphorylation are regulated. Here, we addressed this question using developing mouse brains. Detailed analysis of developing brains revealed that the switch from 3R to 4R tau occurred during postnatal day 9 (P9) to P18 under the same time course as the conversion of phosphorylation from high to low. However, hypothyroidism, which is known to delay brain development, delayed the timing of tau dephosphorylation but not the exchange of isoforms, indicating that isoform switching and phosphorylation are not necessarily linked. Furthermore, we confirmed this finding by using mouse brains that expressed a single isoform of human tau. Human tau, either 3R or 4R, reduced phosphorylation levels during development even though the isoform did not change. We also found that 3R tau and 4R tau were phosphorylated differently in vivo even at the same developmental days. These results show for the first time that the phosphorylation and isoform alteration of tau are regulated differently during mouse development.
Insights
The study reveals that tau isoform switching and phosphorylation changes during mouse brain development are independently regulated. This finding clarifies distinct mechanisms controlling tau
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- Tau is a microtubule-associated protein crucial for neuronal development and function.
- Tau exists in different isoforms (3R and 4R) and its phosphorylation state impacts microtubule stability.
- Developmental changes in tau isoforms and phosphorylation are observed but their regulatory mechanisms remain unclear.
Purpose of the Study:
- To investigate the regulatory mechanisms underlying tau isoform switching and phosphorylation changes during postnatal mouse brain development.
- To determine if tau isoform transition and phosphorylation are coordinately regulated or independently controlled.
Main Methods:
- Analysis of developing mouse brains at various postnatal stages.
- Investigation of tau phosphorylation and isoform expression patterns.
- Utilizing a hypothyroidism model to assess developmental delays.
- Employing genetically modified mice expressing single human tau isoforms.
Main Results:
- The switch from 3R to 4R tau isoforms and the decrease in tau phosphorylation occur concurrently between postnatal days 9 and 18.
- Hypothyroidism delayed tau dephosphorylation but not isoform switching, suggesting independent regulation.
- Expression of single human tau isoforms (3R or 4R) led to reduced phosphorylation during development, irrespective of isoform change.
- Differential in vivo phosphorylation patterns were observed between 3R and 4R tau even at the same developmental time points.
Conclusions:
- Tau isoform alteration and phosphorylation changes are regulated independently during mouse brain development.
- These findings provide novel insights into the distinct molecular mechanisms governing tau's developmental regulation.
- Understanding these independent regulatory pathways is critical for comprehending neuronal development and potential tauopathies.
