Abstract
BackgroundTau is a microtubule-binding protein, which is subject to various post-translational modifications (PTMs) including phosphorylation, methylation, acetylation, glycosylation, nitration, sumoylation and truncation. Aberrant PTMs such as hyperphosphorylation result in tau aggregation and the formation of neurofibrillary tangles, which are a hallmark of Alzheimer’s disease (AD). In order to study the importance of PTMs on tau function, antibodies raised against specific modification sites are widely used. However, quality control of these antibodies is lacking and their specificity for particular modifications is often unclear.MethodsIn this study, we first designed an online tool called ‘TauPTM’, which enables the visualization of PTMs and their interactions on human tau. Using TauPTM, we next searched for commercially available antibodies against tau PTMs and characterized their specificity by peptide array, immunoblotting, electrochemiluminescence ELISA and immunofluorescence technologies.ResultsWe demonstrate that commercially available antibodies can show a significant lack of specificity, and PTM-specific antibodies in particular often recognize non-modified versions of the protein. In addition, detection may be hindered by other PTMs in close vicinity, complicating the interpretation of results. Finally, we compiled a panel of specific antibodies and show that they are useful to detect PTM-modified endogenous tau in hiPSC-derived neurons and mouse brains.ConclusionThis study has created a platform to reliably and robustly detect changes in localization and abundance of post-translationally modified tau in health and disease. A web-based version of TauPTM is fully available at http://www.tauptm.org.
Highlights
Tau is a microtubule-binding protein, which is subject to various post-translational modifications (PTMs) including phosphorylation, methylation, acetylation, glycosylation, nitration, sumoylation and truncation
Researchers are becoming increasingly aware of interplay between different PTMs, in particular on heavily modified proteins such as tau
In order to provide an overview of the current state of knowledge of the tau PTM landscape and facilitate the visualization of potential or proven interactions between PTMs, we designed an interactive tool, which comprises all modifications that have been shown in human brain so far
Summary
Tau is a microtubule-binding protein, which is subject to various post-translational modifications (PTMs) including phosphorylation, methylation, acetylation, glycosylation, nitration, sumoylation and truncation. Aberrant PTMs such as hyperphosphorylation result in tau aggregation and the formation of neurofibrillary tangles, which are a hallmark of Alzheimer’s disease (AD). In order to study the importance of PTMs on tau function, antibodies raised against specific modification sites are widely used. Quality control of these antibodies is lacking and their specificity for particular modifications is often unclear. The formation of neurofibrillary tangles due to aggregation of the microtubule associated protein tau is at the center of multiple neurodegenerative disorders, including progressive supranuclear palsy (PSP), frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), corticobasal degeneration, Pick’s disease, Alzheimer’s disease (AD) and others [1]. In order to study the effects of PTMs on tau function, antibodies raised against specific modification sites are commonly used. Proteins heavily modified by PTMs may escape antibody detection due to steric hindrance and lead to false-negative results
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