O-β-linked N-acetylglucosaminylation
(O-GlcNAcylation) modulates tau phosphorylation and
aggregation: the pharmacological increase of tau O-GlcNAcylation upon treatment with inhibitors of O-GlcNAc hydrolase (OGA) constitutes a potential strategy to tackle
neurodegenerative diseases. Analysis of tau O-GlcNAcylation
could potentially be used as a pharmacodynamic biomarker both in preclinical
and clinical studies. The goal of the current study was to confirm
tau O-GlcNAcylation at S400 as a pharmacodynamic
readout of OGA inhibition in P301S transgenic mice overexpressing
human tau and treated with the OGA inhibitor Thiamet G and to explore
if additional O-GlcNAcylation sites on tau could
be identified. As a first step, an immunoprecipitation-liquid chromatography-mass
spectrometry (IP-LC-MS) methodology was developed to monitor changes
in O-GlcNAcylation around S400 of tau in mouse brain
homogenate (BH) extracts. Second, additional O-GlcNAc
sites were identified in in-house produced recombinant O-GlcNAcylated human tau at relatively high concentrations, thereby
facilitating collection of informative LC-MS data for identification
of low-concentration O-GlcNAc-tryptic tau peptides
in human transgenic mouse BH extracts. This strategy enabled, for
the first time, identification of three low abundant N-terminal and
mid-domain O-GlcNAc sites of tau (at S208, S191,
and S184 or S185) in human transgenic mouse BH. Data are openly available
at (doi:
10.17632/jp57yk9469.1; doi: 10.17632/8n5j45dnd8.1; doi: 10.17632/h5vdrx4n3d.1).
Background: Clearance of tau seeds by immunization with tau antibodies is currently evaluated as therapeutic strategy to block the spreading of tau pathology in Alzheimer’s disease and other tauopathies. Preclinical evaluation of passive immunotherapy is performed in different cellular culture systems and in wild-type and human tau transgenic mouse models. Depending on the preclinical model used, tau seeds or induced aggregates can either be of mouse, human or mixed origin. Objective: We aimed to develop human and mouse tau-specific antibodies to discriminate between the endogenous tau and the introduced form in preclinical models. Methods: Using hybridoma technology, we developed human and mouse tau-specific antibodies that were then used to develop several assays to specifically detect mouse tau. Results: Four antibodies, mTau3, mTau5, mTau8, and mTau9, with a high degree of specificity for mouse tau were identified. Additionally, their potential application in highly sensitive immunoassays to measure tau in mouse brain homogenate and cerebrospinal fluid is illustrated, as well as their application for specific endogenous mouse tau aggregation detection. Conclusion: The antibodies reported here can be very important tools to better interpret the results obtained from different model systems as well as to study the role of endogenous tau in tau aggregation and pathology observed in the diverse mouse models available.
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