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Updated: Sep 24, 2025
In Vitro Aggregation Assays Using Hyperphosphorylated Tau Protein
Published on: January 2, 2015
Residue-based propensity of aggregation in the Tau amyloidogenic hexapeptides AcPHF6* and AcPHF6
Abha Dangi1,2,3, Abhishek Ankur Balmik3,4, Archana Kisan Ghorpade1,2
1Central NMR Facility, CSIR-National Chemical Laboratory Dr HomiBhabha Road 411008 Pune India.
Abstract:
In Alzheimer's disease and related tauopathies, the aggregation of microtubule-associated protein, Tau, into fibrils occurs via the interaction of two hexapeptide motifs PHF* 275VQIINK280 and PHF 306VQIVYK311 as β-sheets. To understand the role of the constituent amino acids of PHF and PHF* in the aggregation, a set of 12 alanine mutant peptides was synthesized by replacing each amino acid in PHF and PHF* with alanine and they were characterized by nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), transmission electron microscopy (TEM) and ThS/ANS fluorescence assay. Our studies show that while the aggregation was suppressed in most of the alanine mutant peptides, replacement of glutamine by alanine in both PHF and PHF* enhanced the fibrillization.
Insights
Researchers investigated how specific amino acids in Tau protein influence Alzheimer's disease aggregation. Replacing glutamine with alanine in key motifs unexpectedly enhanced fibril formation, offering new insights into tauopathies.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Alzheimer's disease and related tauopathies are characterized by the aggregation of microtubule-associated protein, Tau.
- Tau aggregation into fibrils involves two key hexapeptide motifs, PHF* (VQIINK) and PHF (VQIVYK), forming β-sheets.
Purpose of the Study:
- To elucidate the role of individual amino acids within the PHF and PHF* motifs in Tau aggregation.
- To understand the structural and functional impact of specific amino acid substitutions on fibril formation.
Main Methods:
- Synthesis of 12 alanine mutant peptides by substituting each amino acid in PHF and PHF* motifs with alanine.
- Characterization using nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), and transmission electron microscopy (TEM).
- Assessment of fibrillization propensity via Thioflavin S (ThS) and Anilinonaphthalene Sulfonic acid (ANS) fluorescence assays.
Main Results:
- Most alanine substitutions suppressed Tau aggregation, indicating the importance of native amino acids for fibril formation.
- Unexpectedly, replacing glutamine with alanine in both PHF and PHF* motifs significantly enhanced Tau fibrillization.
- NMR, CD, TEM, and fluorescence assays provided consistent data on the aggregation behavior of mutant peptides.
Conclusions:
- The study reveals a complex role for specific amino acids in Tau aggregation, challenging previous assumptions.
- Glutamine residues in PHF and PHF* motifs appear to be critical in regulating, rather than promoting, Tau aggregation.
- These findings offer novel targets for therapeutic strategies aimed at preventing or treating tauopathies.
